Friday, December 22, 2017

#122 - Wednesday, December 20, 2017 - Darn, Foiled Again!

This time, I got out of the house on time (almost) - I scarfed down a homemade egg & sausage sandwich, threw my gear in the car, and got out to the observatory a little before 6 PM.  The sky was still darkening, but a few stars were popping out.  I cautiously entered the Asian beetle-infected dome and started getting setup.

Things went fairly smoothly this time - I cranked down hard on the screw holding the drawtube of the focuser in place using my Leatherman, since it tends to slip, took my time centering the Pacman Nebula (NGC 281) in the view and double-checking, and then I started acquiring 10-minute subframes with my red filter in place.  I got 20 wonderful luminance frames back in November, so now I just needed RGB color frames.  I wanted to pack up at midnight, so with my remaining time, I calculated I could get 9x600s subs for each color channel, plus some extra time built in for changing filters and fixing guiding problems.  Guiding got off to a bit of a rocky start (I don't think this scope is balanced for having a heavy camera dangling off the back, so it's got quite a bit of backlash that PHD has to push through first), but then settled down nicely to about 1 arcsec error or less.  The sky looked great.

The club's 140mm Vixen neo-achromat refractor on its Losmandy Gemini mount, with my borrowed SBIG ST-8300M CCD camera attached.

After setting up the CCD camera inside the memorial dome, I next set up my Nikon D5300 on my Vixen Polarie star tracker (see more about it in this post) and aimed it at Orion.  It hadn't quite cleared the trees yet, but I went ahead and started the run and figured I would just delete the ones with the trees still visible later.  Since I don't have the polar alignment module for it, I could only get about 60 seconds of exposure time at 95mm focal length pointing southeast in order to get minimal trailing (there was still some trailing though).  It came out quite nicely.
Date: 20 December 2017
Object: Orion's Belt
Camera: Nikon D5300
Telescope: 50-200mm lens at 95mm, f/4.5
Mount: Vixen Polarie
Subframes: 103x60s (1h43m), ISO-1600
Darks: 60
Biases: 0
Flats: 0
Temperature: 29F

If you go check it out on AstroBin, you can see what all is in this image, including four nebulae and of course, the three stars that make up Orion's Belt!

I went out and checked my gear periodically, rotated the scope, and then switched from the red to the green filter (I have a manual filter wheel that is a lot better than my old one now!).  Around 10:30, I went outside to check again...and clouds had rolled in! D:  I stopped taking images and went back inside and waited about 20 minutes, but it wasn't looking like it was going to clear up anytime soon.  All my forecasts had promised me no clouds until at least midnight.  Oh well...

On the bright side, I did get a solid set of red frames on the Pacman Nebula, and I got this nice widefield of Orion.  

Someday, I'll get a complete CCD images of the Pacman Nebula!

Sunday, December 17, 2017

#121 - Saturday, December 16, 2017 - ♫You Gotta Know When to Fold 'Em♪

Finally, after several weeks of cloudy nights and clear, moonlit nights, a clear, dark night descended upon the observatory.  Four out of five of my forecasts promised clear skies, and ClearDarkSky said 4/5 on transparency (an important measure for if there will be thin, high clouds, which most forecasts don't count as clouds).  And it would be above freezing to boot!  With my D5300 back in hand after getting it repaired at Nikon (see the end of this post), and armed with my new Astronomik LRGB filters for my borrowed SBIG ST-8300M, I headed out late to the observatory after a Girl Scout meeting (I'm a troop leader for a few high schoolers).

From my co-leader's house, I followed Google's directions for the quickest route, which of course were fraught with peril.  It brought me a way I go sometimes, but had me turn on a road after the one I usually turned on - but I decided to see it through to see if it was really faster.  Well, after totally missing the minuscule turn, I turned around in the town just up the road, which was an adventure in itself because the streets were lined with cars and people for some kind of event.  The road it was having me turn down was the road to the Boy Scout camp that is adjacent to the state park, and I hit a dead end.  Now, there may have been a road through the camp that hooked back up with the road I use to get to the observatory, but I didn't necessarily want to drive through the middle of the camp in the middle of the night, so I whipped around and headed back the way I knew.  All in all, I finally pulled into the observatory parking lot at 8 PM.

I missed imaging the Christmas Tree nebula last year, and since I got out there so late, it was already just high enough to start imaging.  After setting up and focusing (and checking that my new filters were, in fact, parfocal - yay!), I started guiding, looked like crap.  I have about 50/50 luck with the Losmandy Gemini II mount that is in the memorial dome in it guiding well - sometimes it is spot-on, seeing-limited perfect, and sometimes it just decides to go visit Crazy Town.  (To be honest, it may not even be the mount, but weirdness with PHD - sometimes if I power down and restart everything, it works great).  After re-focusing the guide scope and trying again, it was still bad, so I gave up and slewed to a different target that was way up high and had already crossed the meridian - the Pacman Nebula, NGC 281, which I got luminance data for last time I was out.  I set it to take a 5-minute exposure on the red filter, and then went to go set up my DSLR on my Vixen Polarie star tracker.

When I came back to check on the test frame, it was super out of focus!  Once again, the focuser on that scope had slipped out, which was a result of me forgetting to tighten the screw on the focuser when I had focused earlier.  So I re-focused on star Caph in Cassiopeia, then drove back over to the Pacman Nebula and re-centered it using the Focus tool in CCDOps (which basically takes back-to-back, low-resolution images for focusing and centering targets - most nebulae have some kind of open cluster affiliated with them that is easy to see in this mode), and then started acquiring 5-minute frames in Sequence Generator Pro.  Finally, I was off to the races!

...almost.  I came back to check on the first two frames, and I had left the Bahtinov mask on...
This is what happens when you start imaging your target with the focusing mask still on the end of the telescope.

So after re-starting my red frames, I set up my DSLR on my Vixen Polarie.  The Vixen Polarie is a little device about the size of a large point-and-shoot camera and attaches to a regular camera tripod.  It's got a little 360-degree rotating head on top to attach your DSLR to, and a boresight hole in the side to sight Polaris through to roughly polar align it.  Then you simply turn the dial to the sidereal tracking rate, and it slowly rotates the camera at sidereal speed for imaging wide-field targets.  It's more well-suited to short focal length, short exposure images, and the rough polar alignment doesn't work that great (there is a $200 polar alignment module available, but that will have to wait till later).  I aimed my camera with a 55-200mm lens set at roughly 135mm at the Orion Molecular Complex area (including the Orion Nebula and Orion's Belt), figured out that 90 seconds was as long as I could do without trailing at that focal length on the Polarie, checked on the telescope one more time, and then finally went inside to eat dinner around 10 PM.

I brought some Southwest beef & bell pepper skillet with me (yup, ripped directly off the back of Kraft Colby & Monterey Jack cheese) (and it's delicious by the way) in a tupperware, and threw it in the microwave, plugged it in and...nada.  The readout was backlit, but none of the buttons worked, the light didn't come on, etc.  Then I remembered the last time I was out there, I reported that the microwave wasn't working, and that maybe the outlet was dead.  Nope.  No hot dinner for Molly.  Then I got an idea...the club has a few dew zappers in the dome room (known to the rest of the world as "hair dryers"), so I went and grabbed one of those.
Desperate times call for desperate measures!

It worked okay - by the time the top was nice and toasty, the lower layer would be back to room temperature, so I finally gave up after about 10 minutes and just ate it lukewarm.  

By the time I was done eating, it was time to go switch to the green filter (I was doing just 7x300s for each color channel so I could still get to bed at a reasonable hour), but some thin, high clouds had rolled in (in fact, two of my compatriots came out to watch the tail end of the Geminids meteor shower, and they had already left as a result).  Given everything else that wasn't going well that night, I decided it was time to call it quits around 10:30 PM.  It was a shame - not that cold, no wind to speak of, and wintertime targets rising.  Oh well, here's hoping for another chance this week before the moon starts encroaching on my first-half-of-the-night hours.

Sunday, November 26, 2017

#120 - Saturday, November 25th, 2017 - Long Exposure

Two nights out this week - yay for long weekends!  I could only stay out until about midnight because I had church the next morning, but with darkness falling so early these days, that still gave me several hours to work with.

I was a little late getting out to the observatory - about 6 PM - but joy of joys, I wasn't alone!  A few of my fellow sky-people were there from the astronomy club!  It was warm for a late fall evening (nearly 40 degrees F), so a few had set up a Meade 127mm apo refractor that belongs to the club, with a Skyris camera for "electronically-assisted viewing."  As usual, however, it was put away by the time I finished getting everything set up and rolling.  But it was nice having other people to chat with in the warm room after I was set up.  I'm usually out there alone.

My new Astronomik LRGB filters are on their way, so I decided to take some luminance data on something with my CLS (light pollution) filter to knock that out of the way.  The moon was nearly at first quarter toward the west, so I needed to keep to the east.  I was going to do M81 & M82, since I'm dying to capture the rich red hydrogen exploding out of the core of M82 that has eluded my red-insensitive DSLR, but there was a tall tree limb blocking it.  So I decided to do the Pacman Nebula instead, NGC 281.  It's an emission nebula in Casseopeia, about 9,500 lightyears away in the Perseus arm of our humble galaxy.  I imaged it recently with my DSLR on its last night alive.

Setup went smoothly - syncing and focusing on Capella, calibrating PHD guiding, and after a few 60-second test images to get it centered where I wanted it, I started a series of 10-minute frames, and then went inside to chat.  I went out about every 45 minutes to rotate the dome.  After 10:30 PM, constellation Orion was high enough for me to want to slew over there and take more data on the Flame & Horsehead Nebulae, but I decided to not be impatient this time and stay the course and get a lot of frames on the Pacman.  It was time for a meridian flip, so I tried out a feature I just recently found in the computer control app for Gemini mounds: "perform meridian flip."  It didn't work quite as I'd hoped, however - it took me to where it thought the nebula was, but it wasn't centered, and was instead down and to the right off the edge of the frame, like it had been before I centered it on the other side of the meridian.  Oh, well.  Even slewing to the same coordinates (I had saved a screenshot) didn't quite work.  It might work better if I actually aligned it with several stars instead of only syncing on one, but the couple times I tried on this mount, the first two stars would take, and when it slewed to the third star of my choice, it would like point at the ground.  So I gave up on that.  Anyway, I got the nebula re-centered (or close to it), and continued the 10-minute exposures.  When I packed up about quarter to midnight, I had 20x600s exposures, or 3 hours 20 minutes of data!  The histogram was completely separated from the left side of the graph, which is good (if part of the peak is cut off by the left end of the graph, then you are losing data), but it was still pretty close to it, nowhere near having too high of background light.

I went ahead and processed just the luminance frames to see how they looked.  I'm trying out some new techniques with stretching and applying the Carboni tools at different points in the editing since I keep enhancing the gradient that exists due to my lack of flat frames.  Also, weird dark areas are appearing around some of my brighter stars, an effect I haven't seen with my DSLR, which might be related to de-biasing of nearby pixels when a given group of pixels has absorbed a lot of photons.  Hopefully my future CMOS-chipped camera I'm saving up for (the ZWO ASI1600MM) won't have this.  Or it may be an effect of processing - I'm going to try some different stacking modes.  Fellow club members think it's because the Vixen scope is not apochromatic, but neo-achromatic, which means it still has the violet halos that achromatic refractors do, they're just smaller.  I see them on my DSLR, and the Carboni tools in Photoshop can clean it up well, but it doesn't quite work for grayscale images.  Also, the weird dark spots don't appear next to every star, and they look different than halos.

Actually, they're easier to see in negative (now as white splotches).
Hmm.  Further research is required.

Anyway, I'm excited to eventually get some color on these images!  The luminance image here, despite its issues, shows amazing detail of some of the globules.  I'm really excited about using something besides my DSLR.  And the noise is practically non-existent, especially when I can run the sensor as -25 degrees C.  Speaking of cold, it was pretty bearable outside until I went out to check on things around 11 PM, and the temperature had dropped quite a bit all of a sudden!  And it wasn't just my imagination; I have data to back me up.
I use a USB digital thermometer to track the temperature - it's mostly important for when I'm using my DSLR so I can correlate light frames to dark frames at matching temperatures, but it's also helpful for context (like, "could the scope have had frost on it?") and for determining what the lowest temperature I can set the CCD chip to, since it can do only about 30 degrees C below ambient.  I have it set to record data in 5-minute intervals.

The moon is waxing, so sadly I'll have to take a short hiatus from imaging until about mid-December, when it comes up bright but late.  In the meantime, I'm thinking about setting up my 11-inch on the back porch so I can investigate what went on with the declination axis during the Hidden Hollow Star Party and see if it does it again.

Friday, November 24, 2017

#119 - Wednesday, November 22, 2017 - Filter Phenomena

Happy Thanksgiving!
I got an early start out at the observatory on "Thanksgiving Eve," arriving out there around 5:45 PM, about a half hour after sunset.  I ate a Jimmy John's sandwich for dinner on the drive, and after turning on the heater in the warm room, I hustled over to the mini-dome where the memorial scope is kept to start getting set up.  I needed to test whether I had finally properly cleaned by blue filter since I finally found my multi-coated optics & filters cleaning solution (exactly where I thought it was, not sure why I couldn't find it before).  However, I realized on the drive there that I had forgotten the USB cable for the camera, since I transferred it from its normal camera bag to my DSLR camera bag, since my DSLR is currently on its way back to Nikon for repair (see log entry #118 for what happened).  Fortunately, I found a spare in the warm room's computer desk.  I started unpacking...and realized I had left the filters at home in my other camera bag too!  So yes, I drove the 25 minutes back to my house to grab them.  (The club doesn't have any imaging filters, at least that I can find.)  So it was nearly 7 PM by the time I finally started imaging.

On my last trip out, I learned that the menu button on the memorial scope's hand controller (a Losmandy Gemini II mount) does't like the cold (I learned over the summer that it doesn't like the humidity either), but I also learned that I have full control over the scope from my tablet thanks to the Gemini Telescope app that comes with its ASCOM driver.  It even has a "perform meridian flip" button that I am super excited to try!  It also lets me use a wider catalog of stars for the initial sync step of the alignment process.  (I don't actually align the mount besides the one-star sync; I haven't had much luck with the alignment working properly, and since it's very well polar aligned, it's not terribly necessary.  I just pick a new sync star if I'm changing areas of the sky between targets. and the gotos are pretty close).  I synced it to Mirach, since my first target of the evening was getting blue data on M33 so that I can finally process it (I have L, R, and G data already from previous trips).  I couldn't see the diffraction spikes from my Bahtinov mask very well during focusing, however, which wasn't a good sign.  I got it close, and then slewed over to M33 to take some test images.  The stars looked better than they have previously (see this post for some background on the blue filter issues), but only in part of the image - they still had weird diffraction-y mess on stars on the other half, it looks like.
Ignore the high noise level; it's a screen grab of an unprocessed FITS file, with the gain adjusted arbitrarily.

So I think the blue filter is shot.  Luckily for me, I have a $125 gift certificate to Oceanside Photo and Telescope for the Astronomical League imaging award I won earlier this year, which I will spend on a set of Astronomik parfocal LRGB filters that I have already picked out.  Having parfocal filters will be nice anyway - with the ones I currently have, I have to slew to a nearby bright star, re-focus, slew back and re-center the target every time I change color channels.  The L filter cuts IR and UV, which don't focus perfectly and can leave your stars looking de-focused.  However, I only have a 3-position filter wheel at the moment, so the additional ease that that brings will have to wait.

Aside: Filters

As I was writing this and researching which LRGB filters I wanted, I decided to find out exactly what I already had - and it turns out the filters I have are not RGB at all, but UBVRI filters used for photometry!  I've been using three, the BVR ones - blue, visible, and red.  The visible filter appears green.  I have the I filter too, which is IR-pass, but haven't used it - I have read that using an IR-pass filter is your luminance channel for planetary imaging can make really sharp images, though, so I may have to try that sometime.  The U is ultraviolet, which I don't have.  I couldn't find much information out there on what exactly the difference is between the two types, but I think the main take-home is that UBVRI uses a standard, well-defined spectrum and is used for scientific purposes, while RGB filter spectra tend to vary by manufacturer.  Below are the two spectra.
Johnson-Cousins UBVRI filter spectrum

Astronomik LRGB Type 2c filter spectrum (the yellow line is the L, or luminance, filter)

A few observations are that the blue and green filters have greater overlap in the RGB spectrum than the UBVRI one; the green and red filters have greater overlap in the UBVRI spectrum than the RGB; and the red UBVRI filter extends much farther into the IR than the RGB set does.  I will note, however, that my red UBVRI filter still provided some very sharp images (sharper than the green and blue, in my opinion) despite passing a decent amount of IR, which in refractors usually has a slightly different focal point than the visible part of the spectrum because they are made for the visible spectrum.

Anyways, moving on.

Moving on: Back to imaging

Since my blue filter still wasn't working, I decided to go ahead and take some luminance data on a few things while I was out there and the skies were nice.  I used my Astronomik CLS filter (a nifty light pollution-blocking filter that does a very nice job, particularly with my DSLR images).  I've been wanting to image the Heart Nebula, IC 1805, so I slewed over to it.  However, it is a bit too large for the FOV (field-of-view) I have in the memorial scope; it's a good 1.8x2.6 degrees to get the whole thing, but I only have about 1.3x1 degree FOV with the SBIG ST-8300 on the memorial scope, which is a Vixen 140mm neo-achromat, f/5.7.  I decided to image just the heart of it (tee hee).  It's in Cassiopeia, so it will be up for quite a while from my latitude.  

Unfortunately, it didn't turn out very well - I had some guiding problems, and it looks like I was ever-so-slightly out of focus.  For some reason, I couldn't get nice diffraction spikes to form on Mirach with the Bahtinov mask.
Date: 22 November 2017
Object: IC 1805 Heart Nebula (central region)
Camera: SBIG ST-8300M
Telescope: Vixen NA140ssf
Accessories: Astronomik CLS filter (2-inch)
Mount: Losmandy Gemini II
Guide scope: Celestron 102mm
Guide camera: QHY5
Subframes: 5x600s (50m) | Luminance Only
Darks: 10
Biases: 20
Flats: 0
Temperature: -25C (sensor), 25-29F (ambient)

Our local professional astrophotographer tells me this one is hard to get even under dark skies.  I'll give it another try with my new LRGB filters on my Borg when it warms up a bit, since it requires more setup (I have to bring my mount and put it together).  The Borg has a shorter focal length (500mm), and thus a wider FOV - 2x1.5 degrees with the SBIG.  We'll see.

After having all the guiding problems, I homed the telescope, power cycled it, and tried a different target - the Flame & Horsehead Nebulae, since Orion was finally up.  Alnitak formed very nice diffraction spikes with my Bahtinov mask, so I was able to get much better focus.  Bonus, I could see the Flame Nebula in 1-second long exposures in the Focus mode of the CCDOps software, which made framing the image much simpler.  (The CCD chip is by far and away more sensitive than my DSLR chip).  I did have to rotate the camera though to put the Flame and the Horsehead side-by-side on the longer axis of the sensor than the shorter one, otherwise you would have a tall and narrow image of this wide scene.  

Now, Alnitak, the left-mode star in Orion's Belt, is a very bright star - magnitude +4.2.  Actually, it's a double star, with its partner being +9.55.  They are only 2.2 arcseconds apart, which at its distance, corresponds with a physical separation of 574 AU (astronomical units - the distance between the Sun and the Earth).  It heavily saturates camera chips, particularly the sensitive CCD chip.  Now, if I was smarter, I would have taken some shorter-exposure frames too, but it wouldn't have mattered because some high clouds rolled in anyway, and there may have also been frost on the scope too (I didn't feel like getting a stepstool from inside to check).  But the shorter-exposure frame would have let me done a better job at processing out the super-saturation of that star.  

Let's make a long post even longer, and I'll walk you through the processing process.

Stretching the Histogram

I haven't really addressed this yet, but I have recently made the switch from doing stretching and initial adjustments in DeepSkyStacker to stretching the histogram in Photoshop instead.  Everywhere I read online, astrophotographers say to avoid doing this in DSS and do it in Photoshop instead.  I finally gave it a try, and I did notice that the noise was much lower by doing it in Photoshop.  Everyone also says that everyone has a different way of doing it, so here's a quick-and-dirty I've seen several people do.

First, open Levels (Ctrl + L).  Move the left slider (black) to the foot of the histogram (but don't cut into the main part of the histogram itself), and the middle slider (gray) to the right end of the main chunk of the histogram.  Don't adjust the right (white) slider, as you will lose star data.  Hit OK, and repeat the process a few times.
For 16-bit images (Photoshop apparently can't do 32-bit), the brightness scale of a given color channel (in this case, since I have monochrome images, there's only one channel) ranges from 0 to 255.  With a raw image fresh from DSS (choose "Embed" instead of "Apply" when you save out the image), all of the data is contained in the narrow spike you see in the above histogram.  You want to "stretch" this data out so it covers the whole 0-255 scale, basically.
Stretch #2.

Stretch #3.

Once you've done a few rounds of this, open the Curves dialog (Ctrl + M).  

Now, if you're used to editing the curves of a color image, you will notice that this one looks a bit different - it's backwards!  I don't entirely understand why Photoshop does this for monochrome images, and it feels like I'm editing the image while looking in a mirror, but you can accomplish the same objectives.  Adjust the curve to your liking.  I find that I get a nice result when I select a black point (the leftmost dropper) in a dark area of the image, and then pull the middle-left end of the curve down to increase the brightness of the dim areas of the DSO.

Dealing with Blown-Out Stars

I followed Dave Rankin's video on how to bring out the Trapezium region of M42, the Orion Nebula, for how to do this.  Basically, what you're going to do is stretch the histograms for both the long exposure (bright) image and the short exposure (dim) image, make them both layers of the same image, and use a layer mask to combine the two.  It works surprisingly well for how easy it is.  I tried it once on some Orion Nebula data I had as well.  I need to use it more often to deal with bright stars.

In my case, since I don't have short exposure data, duplicated the layer (in the Layers box in the lower right-hand corner, I right-clicked the Background layer, clicked Duplicate Layer, and named it "star"), and then used Camera Raw Filter on the "star" layer to reduce the exposure to make Alnitak dimmer.  Normally, instead, you could copy & paste your stretched and adjusted short-exposure image on top of your long-exposure image.  You can change a layer's name by double-clicking on the name in the Layers section.

Next, re-arrange the layers so that the short-exposure one is on the bottom.  (Just click and drag the layer - I had to unlock the background layer by double-clicking the lock symbol in order to do it).  After that, click on the Background layer (your long-exposure image) and click the "add layer mask" button, which looks like a white box with a dark circle in the middle (it's at the bottom of the Layers section).
Now, with the "Background" (long-exposure) layer highlighted, click the Brush tool over on the left-hand side, and make sure the color is black.  "Paint" the area around the blown-out star to expose the short-exposure, less-blown-out image underneath.  Don't go too far into your DSO, or you'll lose data there.
Obviously, that looks ridiculous.  But we're not done yet!  Go to Filters->Blur->Gaussian Blur, and turn it up pretty high - mine was 182 pixels radius.  Click OK.
Date: 22 November 2017
Object: Flame & Horsehead Nebulae
Camera: SBIG ST-8300M
Telescope: Vixen NA140ssf
Accessories: Astronomik CLS filter (2-inch)
Mount: Losmandy Gemini II
Guide scope: Celestron 102mm
Guide camera: QHY5
Subframes: 4x300s (20m) | Luminance Only
Darks: 23
Biases: 20
Flats: 0
Temperature: -25C (sensor), 23-25F (ambient)

All right, so it kind of helped.  I think there was additional haze from frost or something on the telescope objective - I should have checked for it.  Oh well.  I'll bring my dew heaters next time out.  Now flatten the layers (Layer->Flatten Image), and continue editing - noise reduction, Carboni tools, whatever else you need.

I'll try it again soon!

Now, for the rest of the post

It was cold!  As low as 23F.  Guiding worked better after I re-started PHD2, however, and I didn't have to go check on things that often, so I was able to warm my fingers and toes in the warm room.  A bit of a disappointing night, but I'm starting to get my workflow down on imaging with the CCD camera.  Woot!

Wednesday, November 15, 2017

#118 - Tuesday, November 15, 2017 - Baby It's Cold Outside

After a few weeks of cloudy weather and being busy at work, I finally got out to the observatory again last night!  One of the few benefits of wintertime is much earlier darkness.  The sun set around 5:30 PM, and I scrambled to shovel down some food and grab my camera bag.  Thank goodness for the memorial scope out at the observatory - very little setup required!  My target for the evening: NGC 281, the Pacman Nebula.  I originally hadn't realized that this was indeed a northern hemisphere object until a member of my club posted his image of it.  Super cool wintertime nebula I've been missing!  It's in Cassiopeia, so it's up for quite a chunk of the year.

I've been imaging a lot lately with my borrowed SBIG ST-8300M CCD camera, but since it was cold and I didn't want to sit in the cold in the dome and babysit the camera (since I'm still getting used to using it, and I just cleaned my blue filter with some proper solution and need to check that it's working, which will take a little time), I just decided to bring my Nikon D5300 instead and make life easier on myself.  I'll do the CCD when I have a weekend night or something when I can stay out longer, and maybe it's above freezing.  At least there wasn't any wind.

Also, I got my braces off Friday before last, YIPPEE!!

Besides the clouds, it was reasonably dark, and it was really strange to be two hours into my imaging session and having it be only 9 PM.  It was chilly - my digital thermometer said lower 30s, and then dropped to 29 before I left.  The park had a strong smell of rotting leaves, and it was very quiet, since the cicadas have settled down for their long winter's nap, along with most of the other wildlife, it would seem.

Except for the Asian beetle.  The dome was full of them.

If you aren't familiar, they look a lot like ladybugs, but have some subtle differences.  They can help get rid of pests, but they are also aggressive and will bite.  Apparently, there are a lot of them in my area this year.

If you know me personally, then you probably know that I have a strong distaste for insects.  Fortunately, ladybugs are the least freaky to me, so I put up with co-habitating with them in the dome.  It was a little eerie, however, with there being so many.  When I opened the dome slit, it shook the dome, and I could hear dozens of them pitter-pattering as they were shaken from their roosts.  When I smacked the lid of my camera case against the side of the dome, twice as many fell onto it.  A few fell onto my tablet while I was using it.  When I unfolded the camp chair inside the dome and shook it to dump out all the bugs, over 30 must have landed in a wide pile on the floor, and I had to swipe another ten or so off the seat of the chair.  Thank goodness it was dark...Also, the cold made them pretty inanimate.  None flew around, or really moved much at all.

After I got the scope aligned, my camera focused (I'm pretty much the only one that uses that scope, so it is just permanently very close to focus), PHD calibrated for guiding, and the nebula centered, I took some test frames to figure out what exposure time I wanted to use (I ended up going with 6 minutes - much more and the skyglow starts to get too high.  That, and I really didn't think I had any dark frames longer than that in my dark frame library at these temperatures from last year).  Once the images started going, and everything looked solid, I scurried back into the warm room, which had reached a nice warm 68 degrees after I had originally gone in there and turned the heaters on.  We have such an excellent facility!

I went out to check on things around 9:40 PM, and discovered that my tablet had shut down because the power cable had fallen out during setup and the battery had died faster in the cold.  After getting booted back up, I saw to my dismay that the last image had been taken at 9:21, so I missed out on about three images!  Oh well, it didn't take long to get back up and running.

Thin, high clouds threatened my evening, however.  I managed to get about 13 fair images of it before I finally gave up to the clouds and switched back over to the eastern sky, where it was clearer, to image the Pleaides Cluster, M45.   It came out pretty decently, if dim.  I tried stretching the histogram in Photoshop this time instead of processing it in DeepSkyStacker, and the noise came out much lower.  I didn't do a particularly careful job at the stretching, and I applied several of Carboni's tools (see this post), including space noise reduction, light pollution removal, reduce small blue/violet halos (the Vixen NA140ssf scope that is in the memorial dome is a "neo-achromat," which has less color aberration than achromats, but it's still there), and enhance DSO/reduce stars.  Hopefully I can image it again soon with the CCD camera and fewer clouds.
Photo of the Pacman Nebula.
Date: 14 November 2017
Object: NGC 281 Pacman Nebula
Camera: Nikon D5300
Telescope: Vixen na140ssf
Accessories: Astronomik CLS filter
Mount: Losmandy Gemini II
Guide scope: Celestron 102mm
Guide camera: QHY5 
Subframes: 13x360s (1h18m), ISO-1600
Darks: 10 (38F)
Biases: (36F)
Flats: 20
Temperature: 29-33F

NGC 281 is known as the Pacman Nebula for its resemblance to Pac-Man of the classic arcade game.  It's a HII region - HII is a specific transition of hydrogen atoms that produces a characteristic red glow.  It spans about 40 arcminutes, which is a little larger than the full moon, and lies about 9,200 lightyears away from us in the nearby Perseus arm of the galaxy.
From Wikimedia Commons

I started getting the munchies around 10 PM, but I had forgotten to bring snacks.  There isn't usually much food in the fridge (just soda and leftover beer), but I lucked out - there was half a store-bought apple pie in there!  I checked the date - October 21st, which I decided I could live with.  I ate it cold because I prefer the taste of cold apples to warm ones (we do have a microwave in there), and it was delicious.
The red light makes it look more like a pizza or something.  Or radioactive.

I passed the time by scrolling through Facebook, reading my Astrophotography On the Go book by Joseph Ashley, chatting with one of my friends, and chatting on the phone with my sister, while checking the scope and rotating the dome every half hour or so.  Around 11:45 PM, I put all my layers back on and went to go pack up.  Not a bad night!  I'd meant to get 40 or so quality images on the Pacman Nebula and just focus on one target, but ended up doing two, which is fine.  The Pleiades one came out quite nice, besides the super-saturated stars.  I might need to play around with some interpolation or something so they don't just look like blotchy white circles.  It's hard to believe sometimes that stars are always point sources in the telescope when their light gets spread across so many pixels.
Photo of the Pleiades Cluster, also known as the Seven Sisters.
Date: 14 November 2017
Object: M45 Pleiades Cluster
Camera: Nikon D5300
Telescope: Vixen na140ssf
Accessories: Astronomik CLS filter
Mount: Losmandy Gemini II
Guide scope: Celestron 102mm
Guide camera: QHY5 
Subframes: 13x300s (1h5m), ISO-1600
Darks: 41
iases: 20 (36F)
Flats: 20
Temperature: 29F

The Pleiades is an open cluster of about 1,000 stars, although only seven are easily seen, hence its common name "The Seven Sisters."  It lies 444 lightyears away.  The nebulosity around it is actually a dust cloud that is passing through it and reflecting the blue light of the hot, young (100 million years old!) stars.  It is quite lovely, and the dust can be seen with the eye under dark skies in large enough scopes.

In my haste to pack up, I forgot to take bias frames (more about those here), so when I got home, I got to work quickly setting up my camera to take them and some dark frames on my back porch.  I plugged everything in, through it out on the back porch, and went to connect BackyardNikon to the camera.  It wasn't connecting, even though I was sure I had turned the camera on.  The switch was set to On.  Puzzled, I pulled everything back inside to unplug and replug things.  When I pulled out the AC power and went to plug it back in, I saw that something was wrong with the plug.  It looked like it had crumbled.

Broken AC power cable for Nikon DSLR.

So I grabbed my other AC adapter and plugged it in instead.  No dice.  Then I grabbed my battery.  No power there either.  It looks like I had probably plugged in the broken adapter in the wrong orientation, since the pieces that prevent it from being plugged in wrong were gone, so chances are good that it fried.  I set it slowly on the table and went to bed.  It still didn't turn on in the morning.  Well, there goes some of the money I was saving for a good astro camera...

Sunday, November 5, 2017

The Ford Light Beacon Problem - Deploy Red Countermeasures!

After a year of cramming my telescope gear into my little 2005 Ford Focus, I finally decided it was time for an upgrade.  I loved my zippy little Focus, but I needed to think bigger!  Earlier this year, I bought a 2017 Ford Escape, which I am totally in love with.

However, it has one fatal flaw - SO MANY LIGHTS.

Whenever I go to the observatory or to a star party, the armies of Rohan appear because they saw that the beacons were lit.

With my Ford Focus, there was only one interior light that had a switch I could set to off, and I could turn off the headlights too.  So when I was at the observatory, I could open my car door to grab something, and it would stay totally dark.  Cars today, however, have no such luxury.  When I open the door to my Escape, even if I don't turn the car on, the daytime running lights, all five interior lights, the license plate lights, the "welcome lights" under the side mirrors, and the colored LED accent lighting around the cupholders, inside the doors, at the driver's and passenger's feet, and in the back seat all turn on, turning night into day.  I assume that "normal" people like this, but my fellow dark-adapted stargazers in the astronomy club don't appreciate it at all.  Car lights at a star party are a recipe for disaster, and a sure-fire way to be chased out of the field with (red) torches and pitchforks.

Before you ask, no, there is no switch to turn off the interior lights, turning off the headlights means that the daytime running lights are just on all the time (and they're white LEDs that in my opinion are brighter than the headlights), and I'd probably have to empty half the fuse box to turn them all off, which would probably break this high-tech car.  So what's a dark-adapted girl to do?

I scoured the forums for solutions, but none were terribly useful - some people take out fuses that only have one or two and some tried to get theirs modified for "police mode" with varying levels of success at the dealership.  But then, I got a better idea.  DIY red filters!  I call this solution "red countermeasures."

I quickly found some movie-industry-grade red filters (13% transmission) that were truly red, as opposed to pink (which you get if you coat clear plastic in red) on B&H Photo (here). It was less than $25 for two 20x24" sheets, including shipping.  I carefully measured the size of every light in and on my car (excluding the LED accent lighting - that would be difficult to cover, and it below the level of the windows anyway and not as bad from the outside), and cut the filter paper up into rectangles.  I also got a roll of velcro tape.  

For the interior lights, the license plate lights, and the side mirror lights, I cut small pieces of the velcro and stuck them around the lights.  I get weird looks from my friends when they see it, but I think it's a fair trade-off.  

So far, the outside velcro stickers have survived thousands of miles of road tripping, rainstorms, dust plumes of dirt roads, and four trips to the car wash.  

The red filter rectangles have matching velcro stickers, and they attach and detach quite easily!

The ones for the headlights were a little trickier.  First, the filter paper squares I got weren't quite long enough to cover the entire headlight, so I had to cut two pieces and tape them together.  I originally had envisioned using magnets with adhesive backs on the filter paper and adhering it to the car that way, since I didn't want to put velcro stickers on the body, but then I discovered that car hoods are not magnetic.  (I probably should have known this.)  So instead, I put a magnet on one end of the filter paper that attaches to the quarter panel (which is magnetic), and for the other end, I tucked a velcro sticker into the side of the front grille, and you can't see it unless you look really closely.  It has also stayed on really well through carwashes, rain, and high freeway speeds.

Unless it is super windy (like at the Texas Star Party in the early evening), the headlight filters stay on quite well.  Sometimes I've had to use ticky-tack for extra adhesion on breezy nights.  But otherwise, it's been a great and simple solution!

To store them, I tuck them all into a gallon-size Ziploc bag that lives in the seat pocket of the driver's seat.  I labeled all the pieces ("T" for trunk, "LP" for license plate, "F" for front, etc) since they are different sizes with a black sharpie.  

The lights are dimmer in person than they appear in the picture.

Happy stargazing!

Monday, October 23, 2017

A Super-Duper Primer of Astrophotography Part 11 - Timelapse Photography

Along with the many other things you can do with astrophotography without a telescope (see Part 10 of this series for some ideas), you can make super cool timelapse videos!

One of my favorite side-activities when at a star party or even out at the observatory by myself is timelapse.  You can create videos of the Milky Way rising behind an observatory, activity on the observing field at the star party, your telescope tracking across the sky, planes zipping through the night, clouds appearing and disappearing, a thunderstorm rolling through – all kinds of things.  Timelapse is also my go-to for cloudy nights at the observatory so I can at least get something for my drive out there!  It’s also rather easy to do with a DSLR and a tripod.

This method is also great for imaging meteor showers - you have a much higher chance of catching a meteor if you're imaging continuously, and then you get to make a neat video at the end too.  Two for one deal!

Compose Your Shot

Figure out what you want in your foreground and your background.  Clouds are more interesting to watch than an empty blue daylight sky; the Milky Way rising is always pretty neat, or some other constellation; telescopes moving or people moving around the observing field also make great timelapses.  I did one at the Green Bank Star Quest of me and my minion Miqaela taking down our gear at the end of the weekend with clouds rolling around in the sky at the massive 300-ft telescope moving around (watch it here).  I did another one at the Texas Star Party of the Milky Way rising behind the upper observing field, which was stuffed to the gills with people and telescopes (check that out here).  I’ve also done several of my telescope tracking across the sky and changing targets.  Daytime timelapse is fun too – clouds rolling over hills, thunderstorms, weather fronts, traffic, people, all kinds of stuff.   Again, you are only limited by your imagination!


Focusing in daytime is easy - use auto-focus, and then switch it to manual focus during the timelapse sequence (and don't touch the focuser.  At night, however, it's a little trickier, since your auto-focus won't work.  See Part 10 of this series for a section on focusing at night.

Taking Images

Take several test photos to decide on your ISO, shutter speed, and focal ratio.  If you are imaging during sunset or twilight, you may want to start out bright so that your images don’t get too dark too quickly.  Once you have decided, run your camera in manual mode, turn off everything auto, including D-lighting, set your white balance on something other than auto, and set your focus to manual.  My intervalometer only goes up to 399, and my camera’s interval timer goes up to 999.  Depending on your shutter speed, this may or may not be enough.  During the day, when I’m using short exposures, 399 will only get me 16 seconds of video at 24 fps, and any interruptions in your sequence, like restarting your interval timer, will show up as a jump in your final video.  999 frames will get me 41 seconds at 24 fps, and I’ve found that spending 30 seconds to a minute on a given scene in a video seems to be a good length of time.  For longer timelapses, I’ll usually use digiCamControl on my tablet to take an arbitrary number of photos (usually I’ll set it for like 3 hours and then just stop it when I need to).  For long exposures at night, it depends on how long your exposure is.  The longest I can do without getting star trails is about 15 seconds at 18mm of focal length, but with timelapse, you can get away with 30 seconds, since the images will be blurred together anyway.  However, the longer your exposure time, the fewer images you’ll be getting, so your final video will be shorter.  I imaged the Milky Way rising over the upper observing field at the Texas Star Party for about an hour and a half, and I only got 180 images, which is only 18 seconds at 10 fps.  But, I had a nice bright Milky Way.

Also, you can go ahead and take these in JPG instead of raw.

Problems You Might Run Into

Battery life is probably the number one inhibitor of timelapse.  My stock Nikon batteries only last about two hours in my D3100 that has a non-closing screen, and about four hours in my D5300 that has a closing screen.  I’ll plug into AC power when I can, but this limits where I can image.  So what I usually end up doing is when my battery dies, I’ll move to a different spot and take another timelapse, since I don’t like jumpy gaps in my timelapse videos.

Dew is also an issue, at least at night.  In the case of humid nights, I’ll station my camera near my telescope, and run my 2-inch dew heater strap over to the camera (I got an extension cord, but it’s a little too long, so it’s very lossy, which means I have to crank the current up quite a bit), and wrap it around the lens. I have a dew heater controller from Thousand Oaks that can run four heater straps – one for my 11-inch, one for my guide scope, and one for my timelapse camera.  I can’t use a blow dryer on it because you will see it in your timelapse.  I can’t even check for dew because that will show up too.  So the dew heater is a good solution.  

Another option that astrophotographer Brent Maynard told me about at the Green Bank Star Quest that I think is very clever is to use those chemical foot warmers you can get at the grocery store or the gas station.  The foot warmers are sticky on one side so they’ll attach to your socks – they’ll also attach to the side of your lens!  He even uses them on his reflector, spacing them out around the ring, and using a stretchy band or extra tape to hold them on.  They work great.  I've also used hand warmers attached to the lens with rubber bands - you only need one since they get quite hot.  Cheap and simple solution!

Creating the Video

I mentioned the app VirtualDub in my post about planetary astrophotography as a way to convert .MOVs or .AVIs to a format of AVI that RegiStax likes.  You can also use it to make videos and animated GIFs.  There is a little pre-processing you’ll need to do to your images first, though.

First, get all of your images in time-order. Nikon does this annoying thing where it rolls over after 999 images, and then starts numbering again, from 001.  This means that when you put them all together in the same folder, you’ll have your first 001, and then 001 (1) from when it rolls over, and then 001 (2) when it rolls over again…so basically putting them in name order does not put them in time order.  You can do this by going to the View tab in the folder, choosing Details, and then clicking on the “Date modified” column twice so that it’s in ascending order.  Windows, unfortunately, is very slow at re-ordering large numbers of files, so be patient. 

Once they are in time-order, click on the first image, and then hit Ctrl + A for Select All. Then, either press your F2 key, or right-click on the first image and click “rename.”  Rename it whatever you want, and then hit Enter.  This will name all of the photos the same thing, but with a (1), (2), etc after it.  This is necessary for VirtualDub to be able to pull them all in to make a video.  The numbers have to be sequential – if there is a gap, VirtualDub will only pull in images up to the gap, and then stop.  The first image has to be (1).  So if you delete some photos from the sequence later, you will need to repeat this step to re-number all the photos.  Again, Windows is slow at this, so give it a few seconds, especially if you have over 500 or so images.

Open VirtualDub, and click File -> Open Video File, and then go to the folder where your images are saved.  Make sure the “Files of Type” box says either “All types” or “Image sequence.”  Click on only the first photo in the list, which should be your (1) photo.  Click Open. This will load in all of the sequentially-numbered images in that folder.

Next, go to Video -> Frame Rate.  Here you have some flexibility – 24 fps is about what the minimum is for motion to appear smooth for the human eye, although I’ve found as low as 10 fps looks pretty nice too, at least for timelapse. You can certainly go faster, but it depends on how fast the things in your images are moving, and how long you want a particular sequence to last for when the video is all compiled.  Click the “Change frame rate to” radio button, and enter what fps you want. Click OK.

Next, go to Video -> Filters.  Click the “Add…” button.  Now, your DSLR takes some pretty large frames.  Mine are 6000x4000, which is greater than 4k video.  HD video is 1920x1080.  The larger your image frames are, the larger your final video file will be – like, dozens of gigabytes.  These take forever to upload to YouTube.  So, I reduce the frame size by clicking the “2:1 Reduction” filter, and clicking OK.  Later, I’ll compress it further.  Another option is to use a batch resizing program beforehand to bring them down to a smaller size.  I don’t use any of the other filters (besides MSU Deflicker - see below), although you are welcome to give them a try (and let me know if you get any helpful or cool results).  Click OK.

Now, go to File -> Save as AVI.  Choose where you want the video saved at, and then click OK.  A small window will appear showing progress.  Uncheck the “Show input video” and “show output video” boxes, which should make it run a little faster.  Then sit and wait.  Once it’s done, check out your video!

A word of caution here.  My homebuilt rig has a NVIDIA GTX 1070 card in it, 16 GB of RAM, and an Intel i7 processor, and it cannot play the giant video files that come out of VirtualDub smoothly.  It’s glitchy and slow.  So, your next order of business will be to reduce the file size by compressing the video.  I use an app called Any Video Free Converter to do it.  Simply drag the file in, set all of the video and audio settings to “Original” or something reasonable, and then click Convert.  Even if you set everything to Original, I think it changes it to a different AVI format or applies some other compression algorithm, and the file size comes out like one tenth of what it was – something like a few GB down to even hundreds of MB.  Not only will this play on your computer better, but it will upload to YouTube in an amount of time shorter than the age of the Universe.  I’ve found there not to be much degradation in quality after the conversion process, particularly since my computer screen is only 1920x1080.  

Adding Audio

Your timelapse video will be even more interesting with some flowy space music or epic sci-fi anthems in the background.  First, figure out how long your video is going to be.  This is easy – just take the number of frames, and divide by the fps you’re using – for instance, 1000 frames at 24 frames per second is a 41.7-second video.  Second, find a song you want to use.  I’ve got a spacey playlist I use at public outreach events that I draw from, and there is a lot of that kind of music out there, especially for sci-fi video games.  Then, I use the free software Audacity to cut the song and have it fade out.  Just import the song, cut it at the length of your video, select about the last 5 seconds of the song clip, and then to go Filters -> Fade Out.  Then go to File -> Export to export the song as mp3.

In VirtualDub, with your image files still open, go to Audio -> Audio from another file, and select your song clip.  I usually select the option of auto-detect bit rate, and it seems to work well.  Then do the same as before – File -> Save as AVI to create your video. The audio will also be glitchy until you compress the video.


Sometimes, your timelapse will see to flicker.  This is usually due to leaving some auto-setting on, like white balance or active D-lighting.  Don’t fret, your hard work isn’t toast – there’s a great little plugin for VirtualDub called MSU DeFlicker.  It does some averaging between frames to virtually eliminate this effect.  You can just take its default settings, or play with it some if the flickering isn’t resolved with the defaults.  


And there you have it!  It takes a bit of legwork, but nothing too technically complicated, to make some kick-ass timelapse videos of the sky.  Enjoy!

#117 - Friday, October 20, 2017 - ...try, try again!

Friday night, I was exhausted from my busy week, but all the forecasts were looking so good, and there was no moon, so I just had to answer the call!  I cleaned my blue filter with some distilled water and a cotton swab, and then dried it with a clean paper towel and let it air dry, and there were no streaks.  I packed up the CCD camera and headed back out to the observatory, where now not only Jim, but a few others were camping as well.  I didn't get out until after dark because eating dinner is fairly important, so I got set up as quickly as I could.  I've gotten my process down pretty well now on the memorial scope.

I started with the blue filter on M33, but it looked just as bad as usual!  So I threw up my hands and decided just to re-take the luminance frames, in better focus.  I borrowed Jim's Bahtinov mask to help with focusing (see this post for more on what a Bahtinov mask is).   Those looked pretty good.  While they were going, I was deciding what to do next - take L frames on another target, or use my DSLR?  Jim mentioned that he had a hydrogen alpha filter he was trying out with his Mallincam earlier in the week, but he didn't have it pulled out Friday night because he was tired after several nights of observing all week.  I eagerly asked if I could borrow it - I've never tried narrowband imaging before, and I was anxious to try!  And the memorial scope was the perfect platform to test it on, since it usually has the superb tracking and guiding that is necessary for narrowband imaging, where you have to take very long exposures.

Quick aside - Narrowband Imaging

So what is narrowband imaging?
So let's say you have a monochrome CCD camera.  In order to get color, you put red, green, and blue filters in front.  These are considered "wide-band" filters, since they allow a large swath of wavelengths that are considered in the red, green, and blue regions.  Now, a lot of stuff in space emits on very specific wavelengths.  Take hydrogen, for example - all of the red you see in nebulae like Orion and Rosette and those gorgeous red blotches in galaxy M33 are coming from a specific energy transition of hydrogen atoms, known to astronomers as hydrogen-alpha, or H-alpha for short.  (Also known as H-II to most other physicists and chemists).  For anyone who remembers their high school chemistry, the red light is emitted when an electron excited to the second excited state decays down to the first excited state.  
An illustration of an electron changing energy states and emitting a photon (light).  Taken shamelessly from Starizona.
The energy of the light emitted corresponds with 656.3 nm (nanometers), which is deep in the red to us humans.  The greenish-blue in many nebulae comes from the oxygen-3, or O-III transition for short (500.3 nm, green).  Other important emission lines include sulfur-2, or S-II (672.4 nm, deep red), hydrogen-beta (486.1 nm, blue) and nitrogen-2 or N-II (658.4 nm, red).
Spectrum of some narrowband filters, with red-green-blue filters in the background for comparison. Also taken shamelessly from Starizona.
After the images are acquired at a few of these narrowband wavelengths (usually H-alpha and O-III, and then combined with LRGB), you can get exquisite detail on many kinds of deep-sky objects.  Many of the Hubble images you are probably familiar with use narrowband filters - however, in order to more easily identify differences between the different gases in a given object, false colors will be assigned to each narrowband color channel, hence why Hubble images of things we usually see as red (like the Bubble Nebula below) will look blue instead.
Image result for bubble nebula
Bubble Nebula with the "Hubble pallette" of narrowband color assignments

Bubble Nebula, as seen by my DSLR

One of the huge advantages of narrowband imaging is totally knocking out light pollution.  Since the filters select a very narrow range of color, there is very little light pollution to enter your image.  To make up for it, though, you have to take much longer exposures since you are cutting out most of the incident light - 15 minutes or more, usually.  So it can be very time consuming.

I'll do a more detailed post on narrowband imaging when I get further along in practicing it!

Continuing on...

So my first attempt at narrowband imaging was less than fruitful.  The H-alpha filter specifically was the Meade CCD Interference HA-50 Visible - A/R Coated filter, which is a little wider than some others (so I'm told - it's hard to find info on it, as it's been discontinued).   I thought I had the camera focused pretty well (again using the Bahtinov mask), but the images look kind of soft.  And even with 15-minute subframes, I didn't get very much light from the deep-sky objects I tried.  Orion wasn't quite up yet, so I went with the Veil Nebula.  I left it monochrome since I don't have RGB data on the Western Veil Nebula with the CCD camera yet.  I've seen people use H-alpha as their L frames since you can get much finer detail, so I might give that a go at some point.  Or they'll add H-alpha to their LRGB data.  Lots of things to try.
Western Veil Nebula (NGC 6960), in H-alpha, 8x900s (2 hours)

It might work better with some like the Bubble with more H-alpha, or Orion that is just brighter.  I also tried imaging the Flame and Horsehead Nebulae (Horsehead is more H-beta, but Flame is mostly H-alpha), but the scope started not tracking well again, and it was nearing 2 AM, which is my make-or-break point for either driving home or staying the night.  I had some plans for Saturday, so I left.  But I shall have to experiment with this more.  In addition to the other troubles I had, the sky transparency wasn't very good, which didn't help, of course.