Monday, September 25, 2017

#114 - Saturday, September 23, 2017 - When All Else Fails, Borrow Someone Else's Scope, Take 3

At last year's Hidden Hollow, I wound up chatting with a lot of people about how I do astrophotography.  Some of the organizers caught wind, and when one of the speakers couldn't make it, they asked if I'd fill in with a talk, so I threw one together where I walked through the image processing process, and it went really well!  So this year, I decided to talk about lunar & planetary astrophotography, since the threshold for getting into it is a lot lower - you don't need a fancy telescope (just one with enough magnification, aka focal length, like a Schmidt-Cassegrain), or a mount that tracks particularly well, or a fancy camera (I use a $120 QHY5 guiding CCD) - see my post about lunar & planetary astrophotography here.  I talked about what kind of equipment you might want, what equipment I use, how "lucky shot" video imaging works and why you should use it, and a walkthrough on how to process RGB data in RegiStax.  It went pretty well, I think!  People appreciated how I walked through all of the steps, which usually seems to be the most mysterious part about astro-imaging that usually turns people away from wanting to try it.  The processing for planetary and lunar is also a lot less involved than deep sky, so that helps as well for people to try their hand at some kind of astro-imaging.

There were a few other talks that day, including Astro Bob King, author of “Night Sky with the Naked Eye,” which I got a free copy of courtesy of the Richland Astronomical Society for being a speaker.  All good talks!  Then I took another afternoon "nap" in my hammock.


We had the raffle prize drawing at 5:30 PM, and thanks to the tickets I bought plus the ones RAS gave me for speaking, I won an AstroZap gift certificate, a 12mm Meade astrometric eyepiece, and a beautiful, etched wooden coaster with the Hidden Hollow Star Party logo.  Woot!  

Because of all the issues I was having with my mount, the Richland Astronomical Society graciously let me borrow their Celestron AVX mount and a set of RGB filters.  I was going to use by Borg on it, but then they offered to let me use their Stellarvue 115mm apochromatic triplet refractor, and how could I refuse??  So I got it all set up with no problems, and it guided like a champ!

I was easily able to take 5-minute subframes consistently with no issues.  The only problem I had was that the scope didn't have enough backfocus for my L frames, which I need to take off the filter wheel for.  Not to worry though - I just daisy-chained two 1.25" extension tubes together, and that worked.  Field-expedient fix!  Wish I'd gotten a picture!  Over the course of the night, I imaged the Helix Nebula and the Orion Nebula in full LRGB, about 10 frames per filter.  While that was going, I gave the CGE Pro one last try - I attached my DSLR to the Borg to image the Sculptor Galaxy.  I was only able to get 2-minute subframes that didn't have streaking stars (I couldn't try to guide because PHD can't use the same driver in two instances of the program), so I guess that's not too bad.  However, I don't have any 2-minute dark frames, so I'll have to take some the next time it gets down to 60F at night (which is just about any night in the next few weeks).  

After I got home, I processed the LRGB images, and despite my inexperience, they came out okay!  I've got a lot to learn, and I'm eventually going to re-color-balance these, but it's acceptable for now.  Once I get the workflow down a little better, I'll make a tutorial post about it.
Date: 23 Setepmber 2017
Location: Hidden Hollow Star Party, OH
Object: Helix Nebula
Camera: SBIG ST-8300M (borrowed)
Telescope: Stellarvue SV115T (Richland Astronomical Society)
Accessories: Orion #25 Red, Orion #58 Green, Orion #80A Med. Blue (Richland Astronomical Society)
Mount: Celestron AVX (Richland Astronomical Society)
Guide scope: Orion 50mm guidescope
Guide camera: QHY5
Subframes: 9x300s L, 10x300s R, 9x300s G, 10x300s B (all 1x1)
Darks: 10
Biases: 10
Flats: 0
Temperature: -10C (chip), 60F (ambient)

Date: 23 Setepmber 2017
Location: Hidden Hollow Star Party, OH
Object: M42 Orion Nebula
Camera: SBIG ST-8300M (borrowed)
Telescope: Stellarvue SV115T (Richland Astronomical Society)
Accessories: Orion #25 Red, Orion #58 Green, Orion #80A Med. Blue (Richland Astronomical Society)
Mount: Celestron AVX (Richland Astronomical Society)
Guide scope: Orion 50mm guidescope
Guide camera: QHY5
Subframes: 15x60s L, 8x60s R, 9x60s G, 10x60s B
Darks: 10
Biases: 20
Flats: 
Temperature: -10C (chip), 60F (ambient)

So despite the issues I had with the CGE Pro, I still managed to come home with a few prizes.  And I've still got the timelapse to make - I got several great sequences that are going to make a very nice video.  Once I get time to make it!

Hidden Hollow was a great time this year, with three (!) clear nights, great telescopes, and great company!  It's a small star party, but the people have a lot of heart - dedicated astronomers woke back up at 3 AM to work on observing lists in wintertime constellations that are starting to rise (which is a good idea, since it only got down to the upper 50's F, and it was very pleasant).  I really enjoyed giving my talk and showing people throughout the weekend how I do astrophotography, and of course I also just enjoyed being outside for a weekend.  Can't wait for next year!


#113 - Friday, September 22, 2017 - CGE Pro Mount Woes (I thought I was done with this!)

It was hot out, so I went to the education building to look through the data I had and see if there was anything usable from last night.  I ended up mostly chatting with people though.  I did have some usable short-exposure data on the Orion Nebula though, I think, well, except for the blue filter, which I discovered the next morning was very dirty.  I also didn’t have 30-second dark frames, and it was too hot to take them right then - I couldn't get the chip in the CCD camera to cool down enough (it can cool to 35C below ambient, but it was hot!).  Fellow club member Jim later on helped look at the scope with me, and we tightened up one screw a little, but I can jiggle the telescope back and forth by hand – it’s kind of loose.  But if it were just that, I wouldn’t be seeing all of that error, since the scope is going to be pulled by gravity on one direction.  It sounds like it might be a tough fix. It’s kind of frustrating because this thing was just refurbished!  I’m going to email Dr. Clay and see what he thinks - he's the one who helped me try to fix my CGE mount, and who sold me the CGE Pro.  That mount was just recently refurbished, and it's been Hyper-Tuned, so it should really not be doing this.  It's disheartening that I'm having mount issues again after all of the pain I went through with the CGE less than a year ago!

To make up for the lack of sleep on Thursday night, I set up my hammock and took an afternoon cat nap.  I rarely actually fall asleep when I "nap" (and if I do, I wake up feeling sick), but just lying there letting my mind wander is nearly as relaxing.

            
The food truck was around for dinner, and then sunset came and went.  The thin crescent moon was hanging just above the trees in the west, so I finally got a little bit of useful data!  I threw my QHY5 CCD onto the 11-inch and took a few minutes of video.  I also put the RGB filters on and grabbed Saturn data.  (I got a glasses cleaning cloth and wiped down the blue filter, and the red one too while I was at it).  I spent another several hours that night trying different things to get the mount to guide long enough to image something, but no dice.  Finally I gave up and just attached the SBIG to the Borg refractor, which I was using as a guidescope, and then I attached my 50mm Orion guidescope to the Borg to guide it.  I did as little as 30 seconds, but my stars had these weird cross-shaped patterns to them.  I thought it was the dec axis again, but then I tried just luminance and no filters, and the stars looked fine.  So in addition to the mount issues, now I also messed up the filters! I did collect some blue data, and several good green frames since that filter seemed fine, but that was about it. So I gave up on that, and just attached my Nikon D5300 to my Vixen Polarie, set my 50-200mm lens at 100mm, and imaged the lower half of the Orion constellation.  Well, when I was packing up at around 3:30 AM, I realized that I had forgotten to put the camera back into raw mode after shooting timelapse images in jpeg.  Sigh…another whole night lost!  I went to bed around 4 AM though, since my talk in the morning on lunar and planetary astrophotography was at 10:45 AM.

Well, it wasn't quite lost - my Saturn data wasn't that great, and neither was the lunar data (the seeing wasn't very good), but I went back into the data I took last weekend on my Borg scope out at the observatory and saw that I had some luminance and red frames.  Combined with the images I took this night, I had enough data to stack!  I am discovering that processing LRGB monochrome data is difficult and requires a lot more work and tweaking than my DSLR data does, but it's a whole new world to explore! (And thank goodness for YouTube tutorials!)
Date: 22 September 2017
Location: Hidden Hollow Star Party, OH
Object: M31 Andromeda Galaxy
Camera: SBIG ST-8300M (borrowed)
Telescope: Borg 76ED (piggyback on C11)
Accessories: RGB filters
Mount: Celestron CGE Pro
Guide scope: Orion 50mm guidescope
Guide camera: QHY5
Subframes: 36x30s L, 40x30s R, 22x30s G, 5x30s B
Darks: 10 (L&R), 10 (G&B)
Biases: 20 (L&R), 10 (G&B)
Flats: 0
Temperature: -15C chip (L&R), -10C chip (G&B)

Well, actually, one of the lunar ones came out okay (I was processing those while I was writing this).
Date: 22 September 2017
Location: Hidden Hollow Star Party, OH
Object: Moon
Camera: QHY5
Telescope: Celestron C11
Accessories: f/6.3 focal reducer
Mount: Celestron CGE Pro
Frames: 1 - 800? 2 - 296
Exposure: 15 ms

So the night wasn't a total loss, but it sure felt like it.  It's hard when the skies are clear to have non-functioning equipment!  On the other hand, I did get to enjoy lots of fantastic visual views through people's big juicy Dobsonian telescopes.  It's not particularly dark out at Hidden Hollow, but lots of things really pop with the right filter in a Dob.  Globular clusters are one of my favorite things to look at in a Dob, and I also saw the Swan Nebula, Veil Nebula, and a fabulous view of the Orion Nebula, with lots of detail that I normally only see in my images!  One of the interesting things about the Orion Nebula is that the red is so apparent in images, but you never see it visually, except maybe under exceptionally dark skies with a gigantic fast reflector.  It always appears this greenish-blue.  I might color my images of it like that sometime to represent the visual view better.  

I did also take a few looks through "Big Blue," the 36-inch reflector at the Warren Rupp Observatory out at Hidden Hollow.  

It's so tall, you have to take a scissor lift to get to the eyepiece!  Globular clusters resolve quite clearly into hundreds of stars, and I could see the football shape easily in the Dumbbell Nebula.  They pulled up Stephan's Quintet as well, but I could still only guess at dim fuzzy things.  NGC 7331 near the Quintet looked very nice though.


#112 - Thursday, September 21, 2017 - Off to Hidden Hollow!

Usually, the Hidden Hollow Star Party is a wet, cloudy mess – more party than star!  In fact, one of this year’s t-shirts has a cartoon if a guy holding up an umbrella trying to look through his telescope with rain and lightning all around.  But not this year!  I kept my eyes on the forecast all week, and it held out – clear all weekend!  So I decided to go out there for Thursday night viewing.  I loaded the 11-inch SCT and its CGE Pro mount into the car, plus all the accessory bins, guide scope, camera bag, and personal gear, and drove to the Hidden Hollow camp.  After dropping my stuff in the bunkhouse, I rolled up the top of the hill next to the Warren Rupp Observatory, unloaded my gear, and got the 11-inch built (by myself!).  
"Big Blue" - the 36-inch reflector!

I had eaten my dinner on the drive up – a Subway sandwich – so I hung around the scope until it got dark.  Since the forecast was so good, there were several other people there a night early as well.  My goal for the weekend was to image a couple things on the 11-inch with the borrowed SBIG ST-8300, in color (using RGB filters).  However, one issue after another had me almost going home empty-handed!

           
"The Beast"

It took a while to figure out, but something is wrong with my declination axis. Guiding didn’t look too terrible, but I was getting weird bouncy streaky stars, even at only 30 seconds.  I re-aligned, re-polar aligned, checked the balance, and still it wasn’t working.  I finally noticed in the eyepiece that when I moved the dec axis, the stars seemed to bounce back and forth quickly, like the gears were sticking or something.  
Single 4-minute frame of the Crescent Nebula

So I tried guiding only in one direction for dec, and it helped a little, but not much.  I spent all night chasing after one solution or another, and between waiting on frames, thinking of solutions, and in general chatting with people and looking through their scopes, the night passed quickly, and before I knew it, dawn was arriving. So I went to bed, and slept in till noon (I set an alarm).  

Like last year, I was the only one in the bunkhouse, which is pretty nice – I don’t have to worry about waking people up when I get in late, and I didn’t have to worry about other people getting up early.  I had two more clear nights ahead of me, so I was hoping to be able to work with some people at the star party who might have a clue what's going on with the mount.



Sunday, September 17, 2017

#111 - Saturday, September 16, 2017 - No Sleep Till Andromeda

The Clear Sky forecast (http://www.cleardarksky.com) was looking very promising for last night, which also happened to be Members Night for the astronomy club out at the observatory.  The food theme for the potluck was Oktoberfest, and I couldn't find a German chocolate cake, so I got this double-chocolate torte thing instead (close enough right?), which was devoured by our many sweet-toothed members.  Now, the night before, I didn't get to bed until 11:30 PM, and then I had to be up before 3 AM to volunteer at a marathon.  I got home from that around 2:30 PM, and snuck in a 1.5 hour nap before loading my telescope gear into the car (the Borg 76mm refractor, new Celestron Advanced VX mount, camera bag, and the CCD camera I'm borrowing) and heading out to the observatory.  The sky was as fantastic as promised.

My goal for the evening was to add some RGB (red, green, blue) data to the luminance data I took on the Dumbbell Nebula last weekend.  I got everything set up and aligned, but then I had issues with guiding again - it worked for a while, but then it was getting really bad so I went to reset it, and then the ASCOM driver for the mount kept crashing, and finally I gave up and just took 2-minute subframes instead and binned the images 2x2.  Binning on a CCD camera essentially means that instead of every pixel recording the light and saving it out, pixels are combined to increase the amount of light gathered in those pixels.  From what I understand about CCD imaging, you want to take your luminance frames at the highest available resolution, so 1x1 binning, and then to get good color saturation, you take your RGB frames at 2x2 binning.  So I took all the data, and then this morning I got it copied over to my desktop and did some Googling on how to deal with LRGB data in DeepSkyStacker (I ended up following this video).  It is not easy.  (There are paid programs out there that do a better job).  If your L images have no rotation or movement from your RGB images, you can stack them separately from each other and then combine in another program like Photoshop, but my filter wheel only has 3 positions, so it's inevitable that my L images will not be exactly lined up with the RGB, especially since I have to go to a nearby bright star to re-focus, and then back to the target.  In addition, the filter wheel I have only has one screw with which to hold the camera on, so the camera naturally rotated and slid around a bit as the telescope moved across the sky, so not even my R, G, and B channels are lined up with each other, at least not without cropping out most of the image to delete the areas that don't overlap.  Ultimately, I wasn't able to use the L images with the RGB images, so I just used the RGB's alone in Photoshop with their lower resolution, but color balancing was hard and the image turned out pretty messy.  Well, here it is anyway:

Details:
Date: 16 September 2017
Object: M27 Dumbbell Nebula
Camera: SBIG ST-8300M
Telescope: Borg 76ED
Accessories: RGB filters
Mount: Celestron AVX
Guide scope: N/A
Guide camera: N/A
Subframes: 11x120s R (2x2), 11x120s G (2x2), 12x120s B (2x2)
Darks: 10
Biases: 0
Flats: 0
Temperature: -15C (chip), 54F (ambient)

It's interesting to note here how green it came out.  I see this a lot in CCD images of the Dumbbell Nebula online.  My DSLR records much more blue than green.

After I was through with the Dumbbell Nebula, I decided I wanted to try another bright target, this time all with the same binning and exposure times in case I ran into issues with DeepSkyStacker - M31 Andromeda Galaxy.  The green and blue channels ended up being out of focus, so I wasn't able to make the full LRGB image, but the luminance channel came out great!
Date: 16 September 2017
Object: M31 Andromeda Galaxy
Camera: SBIG ST-8300M
Telescope: Borg 76ED
Accessories:
Mount: Celestron AVX
Guide scope: N/A
Guide camera: N/A
Subframes: 36x30s L (18 minutes)
Darks: 10
Biases: 
Flats: 0
Temperature: -15C (chip), 54F (ambient)

Heck yeah!  That is awesome.  I can't wait to get some color data on that.  Hopefully at the star party I'm going to this weekend...it's looking like it's going to clear up.

When I finally started packing up around 4:30 AM, Orion was getting higher in the sky.  I can't believe winter is nearly upon us already!  I was very tempted to take just a set of luminance frames before packing up, but I knew I really needed to get home and get some sleep - the nap I took in the afternoon was the only sleep I had gotten in the last 24 hours, and I do need to be at work on Monday.  So I just took a single frame, 30 seconds long, binned 1x1, and besides the higher noise level since it's just a single frame, it's gorgeous!

One discovery I made last night is that it's going to take some practice for me to get a feel for what the right settings will be for a given target.  Looking at the individual FITS frames can be misleading, since you need to stretch the histogram quite a bit in order to look at them, and they can look really blown out or crazy-noisy.  Here's an example of a single Andromeda frame, from the red channel:

The core looks blown out, and there's a lot of noise.  But after stacking (and making some tweaks in Photoshop), it looks like this:

Ignore the weird rotation, the camera was sliding around inside the filter wheel, and this is aligned to the highest-scoring luminance image.

In addition to the stuff with the telescope, I also pulled out the Vixen Polarie I bought at ASTROCON, a little star tracker you can attach a DSLR to (more info on that in this blog post), and imaged the Pleaides cluster set at 100mm.  The Pleiades, also known as the Seven Sisters, is an open cluster about 444 lightyears away that is easily visible naked eye, even light fairly light-polluted locations.  It's a pretty wide-field image, but you can see some of the nebulosity associated with the cluster.  I need to take some flats for this lens.

So it was a very long, sleep-deprived 26-hour run yesterday, but I made it safely back to my house, and learned a lot!  I actually felt quite awake all night.  Astrophotography is better than coffee for waking me up.



#110 - Friday, September 15, 2017 - So Long Cassini!

Friday night, I went to a Cassini farewell party at a brewery, and brought my 8-inch SCT along to show off Saturn with.  Well, Saturn + Cassini, as Cassini's ashes were already one with the ringed planet by the time the party started.

If you are unfamiliar, the Cassini mission launched in 1997 with the goal of exploring Saturn and its moons.  It was a NASA-ESA (European Space Agency) collaboration, with ESA supplying the Huygens probe that landed on the surface of Titan, one of Saturn's more interesting moons.  The mission was wildly successful, with Cassini lasting many years longer than it was planned to, and a great deal of science was done with both probes.  Not to mention the breathtaking photos beamed back of the Saturn system.  My hands-down favorite has to be this one, where Cassini views Saturn backlit by the sun:
Backlit Saturn from the Cassini mission.  Courtesy of NASA.

Not only does it show Saturn's fascinating ring structure, including ghostly outer rings newly discovered, but the tiny whitish dot in the lower left quadrant is our humble Earth.  

Here's a neat infographic:
Alllllllllll the science!

The Cassini farewell party included a special beer, a talk about the development of Cassini's RTG (radioisotope thermoelectric generator, the device that provides electrical power and heat to a number of space missions that are in environments where they are unable to take advantage of solar radiation), cake, and views of Saturn through my telescope.  It was cloudy most of the evening, but then it cleared up soon after the talk, so I hastily (and still with a buzz from a few glasses of the special beer) set up my 8-inch.  I probably had about 80-100 people come look through the eyepiece, including bar-comers who weren't there for the party, and probably some passers-by as well.  Many had never seen Saturn in a telescope before, or even looked through a telescope at all.  Saturn is one of my favorite things to look at through a telescope, and it is a real crowd-pleaser!


Good times were had by all!  (And I got my tab paid for :] )



Monday, September 11, 2017

#109 - Sunday, September 10, 2017 - More CCD Imaging

I went back out again last night to practice some more with the SBIG ST-8300M, the monochrome CCD camera I'm borrowing.  Since I had work the next morning and the moon would be coming up before midnight, I didn't have enough time to try imaging with RGB (red, green, blue) filters, so I imaged just luminenance frames again.  Also, rather than setting up my own scope, I utilized the astronomy club's 5-inch refractor imaging rig inside a dome.
The SBIG ST-8300M CCD camera attached to my club's 5-inch refractor.

I was going to image M16 Eagle Nebula, but all day there was a barely-discernible haze, and once night fell, I couldn't even find Sagittarius.  Higher altitudes were much clearer though, so I decided to image IC 1396, the Elephant Trunk Nebula.  I started with a 3-minute subframe for centering, but I couldn't quite see the dark molecular cloud for which the nebula is made, so I took a 5-minute image, and then there it was!  I could juuust make it out.  (I've gotten pretty good at this, even on my dim, reddened tablet screen.)
See?  Don't you see it?  No?  Maybe...?

I used the Focus routine in CCDOps to center it (in the frame I grabbed in CCDOps, it was over to the right), getting an updated frame about every 3 seconds or so as I watched that bright star to the left move leftward.  When I figured it was close enough, I started up Sequence Generator Pro, cooled the chip to -20C, and fired away with 12x5-minute exposures.  

Since I'm just borrowing this camera, I don't have a darks library built up yet, so when I got home, I set it out on the back porch, had to cool to -20C, and set a series of exposures from 2 minutes to 6 minutes, 20 darks each.  It got down to -20C initially, but it must have been warmer on my porch than I thought, since the temperature listed in all of the dark frames I took was -15C instead (the chip can only go to -35C below ambient temperature).  One nice thing about FITS files, which looks like is the only file type SGP will save out for SBIG cameras, is that they have a lot of nice header data attached to them.  The downside is you need a special program to open them (I downloaded AvisFV), and you can't scroll through them, but have to open one at a time.  Also, I didn't have time to collect flats before it got dark, so I'll have to go out again later, and then re-process.  Despite the temperature difference in the darks, and the lack of flats, I stacked them anyway.
Date: 10 September 2017
Object: IC 1396 Elephant Trunk Nebula
Camera: SBIG ST-8300M (Phil's)
Telescope: Vixen na140ssf
Accessories: Astronomik CLS filter
Mount: Losmandy G11 Gemini II
Guide scope: Celestron 105mm
Guide camera: QHY5
Subframes: 12x300s (1h)
Darks: 20 (only -15C for some reason)
Biases: 20
Flats: 0
Temperature: 50F (ambient), -20C (chip)

Can you see it now??
I think if I get some good flats, and the correct temperature of darks, maybe I can get some more out of this image.  The rest of the low contrast is likely due to the crummy atmosphere.  But it's still east of the meridian in the first half of the evening, so I've got time!

On my next time out with it, I'll use some RGB filters on something and get color!


Sunday, September 10, 2017

#108 - Saturday, September 9, 2017 - Testing out some new equipment!

So my Celestron CGE Pro mount is awesome, and I love it, but let's face it, hauling 170 lbs of gear up and down the stairs of my apartment (and that doesn't include all the peripherals like eyepieces, camera bag, dew heaters, etc), loading and unloading it from the car, and getting it all set up and aligned is a pain in the rear.  It's great for when I can leave it set up for several nights in a row, but for single nights or half-nights out at the observatory, it's just not really an option.

After borrowing my minion Miqaela's Celestron Advanced VX mount for the Texas Star party, I discovered that it works really pretty well with scopes that have a short focal length, like my 3-inch Borg refractor.  And if I can get it well-polar-aligned and guiding, it could very well handle my 8-inch SCT.   As a present for myself for winning the Astronomical League award and having my corona composite image be selected as AstroBin's Image of the Day (Sept 4, 2017), I hopped onto Astromart to see if anyone happened to be selling an AVX.  Well, as luck would have it, a gentleman in Massachusetts was selling one he'd only used a couple of times for $600 - $300 off the new price!  So heck yeah I jumped on that.  It arrived Friday (and was very well packaged, I might add), and while it was of course cloudy Friday night (we had our club meeting that night anyway), it cleared up nicely for Saturday night, which must be the first time in the history of astronomy that getting new gear didn't cause cloudy nights for a week.  

After a couple of hiccups (like plugging the DEC cable in the wrong direction - there is no labeling on the cable for which way the electrons need to flow!), I got it up and running.  Woohoo!

 Now, normally I wouldn't test out two new things at the same time - that's just bad science.  But since I'd used the AVX before with my Borg refractor, I decided to just go for it and also take the moonlit night to test out a CCD camera I'm borrowing from club member Phil - a SBIG ST-8300M.  It's a monochrome camera with a CCD chip.

[ Brief aside - CCD vs CMOS ]

So what is the difference between CCD and CMOS anyway?

First, a couple definitions.

CCD stands for charge-coupled device.  CCD chips have been around a long time - it was invented in 1969 at Bell Labs.  Basically, light strikes the photoactive layer (a layer of silicon), and is converted to electrons, and a capacitor for each pixel accumulates charge based on the amount of light that falls onto that pixel.  Once the exposures is signaled to be complete, the capacitors dump their charge into their neighbor, and on down the line until it reaches the last capacitor in the row, and then the charge is dumped into a voltage amplifier.  This is done sequentially until all of the pixels are read off and digitized, and then the computer displays that information as a picture.  

CMOS stands for complementary metal-oxide semiconductor, and that is the type of sensor you will find in consumer cameras and cell phones.  It's functions similarly to CCD chips, except that each pixel has its own amplifier.

They each have their advantages.  CMOS chips are cheaper to manufacture and consume less power, but they typically have higher noise, and are less sensitive.  CCD chips are more expensive, but have higher sensitivity and lower noise profiles.  However, CCD chips more readily have blooming effects when pixels are saturated (the "potential well" fills up with electrons and can't accept any more, so the charge bleeds over to neighboring pixels).  

For daytime imaging, noise isn't usually an issue - bright sunlight vastly dwarfs the noise of the chip, and you have no shortage of signal, so the lower light sensitivity of CMOS isn't an issue.  But for astrophotography, it becomes a big issue, since you have very low signal coming from those dim fuzzies.  

Most astrophotography cameras you will find out there are CCDs.  However, with the huge demand from cell phone consumers for high-quality cameras, especially in low-light conditions, CMOS chips are quickly closing the gap on quality, sensitivity, and noise.  In fact, the astrophotography camera I'm thinking about purchasing in the not-too-distant future is the ZWO ASI1600MM, which is actually a cooled CMOS chip instead of a CCD, and it has less noise than many CCD chips (at least until you get to super expensive cameras.)  

As far as astrophotography cameras go, another big advantage for CCD cameras vs DSLRs is the fact that they're usually cooled, or at least the ones meant for deep-sky imaging are.  This greatly reduces the noise.  For example, the SBIG I'm borrowing has both a fan and a TE (thermoelectric) cooler that can drop it up to 35 degrees C below ambient temperature.  So last night, since it was 50F outside (10C), I set it at -20C.  The CMOS-chipped ZWO also has this two-stage cooling.

All right, so how'd the pictures come out?

I tested out the SBIG at my house about a week or two ago to make sure I could get it to talk to the computer.  It's an older model, and SBIG doesn't make available the software used to control it anymore - CCDOps.  They're instead pushing their expensive TheSky software on people.  Fortunately, Phil still had the disks, so I was able to get CCDOps installed, and Sequence Generator Pro will run it as well.  CCDOps is helpful though for its focusing routine and other features.  It can grab single frames, but can't run a sequence.  (I'm still running the Lite version of Sequence Generator Pro, which still lets you run sequences, view your images, set the sensor cooling temperature, and lots of other stuff, you just can't access some of its other features like PHD integration and stuff like that.  I'll buy it later when I actually buy a camera).

Since I couldn't get guiding to work, I decided just to take a few test frames anyway to see what the sensitivity was like, so I aimed for M16, the Eagle Nebula, which being mostly hydrogen alpha wavelength, would look nice in monochrome, since I didn't want to mess with color filters the first night out.  This is a 60-second image taken using Sequence Generator Pro.

I was surprised by how dark it was!  Just to check, I took one in CCDOps using its Grab tool, and I could actually see it:

There it is!  I figured that CCDOps must just be stretching the histogram a lot so you could see it, and that the data really was there in the dark image, it was just hard to see.  By the time I got to this point, though, M16 was getting into the muck, and I still wasn't sure whether it would be bright enough for my testing, so I slewed to M27 instead, the Dumbbell Nebula, a much brighter target.  After using CCDOps single grabbed frames to get it mostly centered, I took a series of 15 with Sequence Generator Pro, at 3 minutes exposure time, hoping that I wouldn't lose too many frames to periodic tracking error since guiding wasn't working.

So here's a single 3-minute frame:

Yikes!  Hot pixel city!  I took dark frames and bias frames that were also pretty crazy.

Now, these frames are stretched pretty far so you can see them, and I don't have a good reference for what setting I'd put the stretching at to compare it with my DSLR.  (By the way, I'm using a piece of freeware called AvisFV to view the FITS files that Sequence Generator Pro saves out, and you can just use the scroll wheel to change the amount of stretching on the image - basically, make it brighter or dimmer).

Time for some magic

It's not customary for a scientist to call a mathematical or scientific process magic, but even though I have a decent understanding of how stacking works, let's face it, it's still magic.

I gave DeepSkyStacker the light frames, the darks, and the biases (a review of what these are can be found here) (and I ended up not having time to take flats before it got dark), and out came a virtually noiseless, rather nice image of M27!
Date: 9 September 2017
Location: John Bryan State Park Observatory
Object: M27 Dumbbell Nebula
Camera: SBIG ST-8300 (Phil's)
Telescope: Borg 76ED
Accessories: Astronomik CLS filter, Hotech SCA field flattener
Mount: Celestron Advanced VX
Guide scope: N/A
Guide camera: N/A
Subframes: 6x180s (18m)
Darks: 5
Biases: 15
Flats: None
Temperature: -25C (chip), 50F (ambient)

Now, as you can see, my field flattener is not quite doing its job (according to the directions, I may need a spacer or something for using it with a CCD camera as opposed to a DSLR, where the chip is set pretty far back from the front of the body), but hey lookie, it's my first CCD astro image, and it came out pretty nice!  So my next stop is going to be using it with RGB filters to get some color in there!


Monday, September 4, 2017

#107 - Sunday, September 3, 2017 - Moon too bright? Image that instead

When it's a weekend night and the moon is too bright to do deep-sky imaging, don't despair - that's the perfect time to image planets and the moon!

So I set up my 8-inch SCT in the front yard of my apartment, and after aligning slewed to Saturn first, since it would soon disappear behind the roof of my building.  My NexStar SE mount was tracking better than it has been - sometimes, when I'm looking at a highly magnified image, it drifts off rather quickly (even after picking up the backlash).  The backlash is unreal on that mount though!  I would turn on anti-backlash, but then it makes the image jump, which is difficult when you're trying to center a planet in a highly-magnified view.  Getting my QHY5 monochrome CCD focused didn't take long, but I only managed to get a luminance and half a red video before it slipped behind the roof of the apartment.  Oh well, next time.  And the luminance video turned out to be a little bright.
Date: 3 September 2017
Object: Saturn
Camera: QHY5
Telescope: Celestron 8-inch SCT
Mount: Celestron NexStar SE
Luminance channel
Frames: 689
Exposure: 4.8 ms
Gain: 31

Next, I slewed over to the moon, which was nearly full, so I went to the shadowy edge to try and image some craters partway in shadow.  I found some interesting spots and took a few 1000-frame videos, and then I attached the camera to a Barlow.  Without the Barlow, the tiny CCD chip in the QHY5 paired with my 8-inch gives me a 11.4x9 arcmin field-of-view (FOV).  But with the Barlow, it's even tinier - 5.4x4.2 arcmin.  However, the seeing around here rarely supports that kind of magnification, and even with "lucky shot" processing like what RegiStax does, it's hard to get nice sharp images.  But I think they turned out pretty nicely anyway.
Frames: 391
Exposure: 0.101 ms
ISO/Gain: 10
Frames: 600-ish?
Exposure: 0.101 ms
ISO/Gain: 10
Frames: 586
Exposure: 0.101 ms
ISO/Gain: 10
Frames: 233
Exposure: 25 ms
ISO/Gain: 50

Details:
Date: 3 September 2017
Object: Moon
Camera: QHY5
Telescope: Celestron 8" SCT
Accessories: ND filter, 4th image had 2x Barlow
Mount: Celestron NexStar SE

The nearly-full moon is so bright that I had to use my ND (neutral density) filter to get it dim enough to not saturate my camera at its lowest settings.  

In addition to that imaging, I am borrowing/testing out a SBIG ST-8300 monochrome from one of the club members.  I was hoping to do some deep-sky imaging with it last weekend, but alas, I came down with a cold within hours of returning home from the solar eclipse in Casper, WY.  So it will have to wait another week or two.  I tried imaging the moon with it, but it is too sensitive - even with the ND filter, it was way oversaturating.  Oh well, can't wait to try it on a DSO!