Saturday, August 25, 2018

#157 - Thursday, August 23, 2018 - Back to Basics

With the increasingly complex deep sky imaging rigs I have, and all of the gear that is necessary to make it work, it was nice on Thursday night just to throw my 8-inch Schmidt-Cassegrain, its simple alt-az mount, a battery, tablet, camera bag, table and chair into the car, like old times.  Three trips got all the gear in the car instead of nine.  It reminded me of when I first got started, and we get fit everything into the trunk of my then-boyfriend's Corvette.  Now it usually takes the entire back of my compact SUV!

Before that, though, I helped mow the lawn at the observatory earlier in the evening, and I had brought along my camera bag in the hopes of having time to image the sun before it went below the trees.  I got there late from work, so they were already mostly done.  So I pulled out the club's Lunt solar scope, set it up on the club's Celestron NexStar SE mount (the exact same one I have), and first put an eyepiece on it to see how things looked.

The sun was so.  Boring.  Like, the most boring sun I've ever seen!  No sunspots, no plages, not even any prominences.  At first, I thought I saw a tiny sunspot, but it turned out to just be a dust mote on the eyepiece (it didn't stay with the sun when I tapped the telescope).  As it turns out though, there was a sunspot there!  It's about a third of the way up from the bottom, near the center.

Date: 23 August 2018
Object: Sun
Camera: ZWO ASI1600MM Pro
Telescope: Lunt LS60THA 60mm pressure-tuned (500mm FL)
Accessories: N/A
Mount: Celeston NexStar SE
Frames: 1963/2003
Exposure: 0.35 ms
Gain: 0
Stacking program: RegiStax 6

After getting dinner with one of my friends, I went back to my house and loaded up my gear into the car.  Since the moon is large and bright this time of the month, it was a planetary imaging night rather than a deep-sky night.  Usually I do planets from my front yard, but the apartment building blocked where Jupiter and Venus were, so I drove to a nearby empty cul-de-sac on top of a hill.  Venus was rapidly dipping toward the horizon, so I rushed to get everything setup, and was ready to go in about 10 minutes.  Once I trained the camera on Venus, however, I could see right away that it wasn't going to work - the atmosphere was boiling like crazy that low, and Venus was a blobby, crescent-shaped mess.  Oh well, next time.

This year is excellent for planet-lovers - literally everything is up right now if you stay out late enough (and Mercury rises before the sun in the morning - not by much though!).  If you don't want to stay up late, you still get the best of show - Jupiter, Saturn, and Mars, plus Neptune if you so desire.  I worked my way across the sky from west to east.

Jupiter was my first target, and after using my Bahtinov mask  to focus on Arcturus, I centered Jupiter, and then cut the ZWO ASI1600MM Pro's frame size from its native 4656x3520 down to 640x480.  The primary reason for this is faster frame rate.  The atmosphere is always moving and swirling, and every once in a while, you get a clear column of air.  A high frame rate will get you more frames in those moments of "good seeing."  In addition, planets rotate, and Jupiter rotates fast - you need to collect your data within a 3-minute window to minimize the rotation.  With a monochrome camera, that means collecting a few thousand frames on all four channels - luminance, red, green, and blue - in that time frame.  I usually collect 2,000.  When I run at a small cropped frame, and the planet is bright enough to have fast exposure times, I can get 100 fps or more.  It only took about 20 seconds to get each color channel!  However, I could see on the screen that Jupiter wasn't looking very good - it was pretty fuzzy, and I couldn't make out much detail.  I could also see the edges undulating.  This meant that the seeing was still pretty bad, even though Clear Sky promised 4/5 seeing conditions.  It was only about an hour after sunset, though, so there was still ground heating and other sources of turbulence.  If I came back later, then it might be better.  But sometimes, the data can surprise you - and I was very surprised with this data set!  The videos looked bad, but the RegiStax image quality ranking plot actually looked pretty promising, and then each color channel, once I stacked and applied wavelet deconvoution, looked great!  It just goes to show, don't decide that your data is junk until you've given it a fair shake...


All my data that night also turned out weirdly dim, so I'm not sure what's up with that, but punching up the brightness in RegiStax helped.  
Here's the final product!

Object: Jupiter
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik LRGB Type 2c 1.25" filters
Mount: Celestron NexStar SE
Frames: L: 1141/2015
    R: 1279/2030
G: 1024/2021
B: 1154/2010
FPS: 122
Exposure: L: 1 ms
  R: 3 ms
  G: 3 ms
  B: 5 ms
ISO/Gain: 139
Stacking program: RegiStax 6

Not too bad!  Not my best, but way better than I thought it would be based on the videos I took!

Next was Saturn!  I decided to try something I haven't tried with this camera yet - adding a 2x Barlow.  This is a lens that you can screw onto the nosepiece, and it doubles your magnification.  It also doubles your effective focal ratio (so on my C8, from f/10 to f/20), which makes the image dimmer (this is a result of the light being more spread out among the pixels).  So my frame rate was a tad slower due to the longer exposure time, but Saturn's rotation is much less obvious than Jupiter's anyway (and slower).  The seeing was starting to settle by this point, but I still didn't get quite the sharpest image of Saturn.

Date: 23 August 2018
Object: Saturn
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik LRGB Type 2c 1.25" filters, 2x Barlow
Mount: Celestron NexStar SE
Frames: L: (not used)
    R: 577/2001
G: 602/2003
B: 393/2002
Exposure: L: 15 ms
  R: 40 ms
  G: 40 ms
  B: 80 ms
ISO/Gain: 139
Stacking program: RegiStax 6

Next was Mars!  Now that the dust storm as abated, there's a lot more surface detail to see.  If the atmosphere cooperates, that is.  I tried with the Barlow on, but they all came out too fuzzy from RegiStax - I didn't even bother combining the color channels.  The un-Barlowed one looks better, although I did get some artifacts near the left edge.

Date: 23 August 2018
Object: Mars
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik LRGB Type 2c 1.25" filters
Mount: Celestron NexStar SE
Frames: L: 778/2013 (not included in final)
    R: 748/2021
G: 767/2011
B: 879/2025
Exposure: L: 0.3 ms
  R: 0.6 ms
  G: 1 ms
  B: 2 ms
ISO/Gain: 139
Stacking program: RegiStax 6

Last week, the venerable lunar imager Robert Reeves gave me a tip on using the Shake Reduction filter in Photoshop to tease out a little additional sharpness.  Sometimes it works, and sometimes it doesn't, but it did all right with this image.  

Next was the moon, with the Barlow still on (I imaged the moon between the zoomed-in and zoomed-out sets on Mars).  It's nearing full, but there were still some gorgeous shadows in the craters near the unlit edge.  These take forever to register in RegiStax due to the large number of align points.  I took the images with the red filter, since red light is scattered less in the atmosphere, and I find my images always come out sharper with that filter than with luminance, green, or blue.

Date: 23 August 2018
Object: Moon
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik R Type 2c 1.25" filter, 2x Barlow
Mount: Celestron NexStar SE
Frames: 401/2000
Exposure: 4 ms
Gain: 139
Stacking program: RegiStax 6

I took a second set of images as well in a different area, but my mount is not the best at tracking, and the image shifts frame-to-frame ended up being too much, and it didn't come out well.

I swung back my Saturn after I re-did Mars without the Barlow, and got this much-better image.
Date: 23 August 2018
Object: Saturn
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik LRGB Type 2c 1.25" filters, 2x Barlow
Mount: Celestron NexStar SE
Frames: L: 493/2021
    R: 604/2018
G: 882/2021
B: 1005/2010
Exposure: L: 4 ms
  R: 10 ms
  G: 10 ms
  B: 20 ms
ISO/Gain: 139
Stacking program: RegiStax 6

Also, it's not just the camera that was seeing less-colorful images than usual - I looked at Saturn, and it seemed almost de-saturated in color.  Mars even naked-eye looked less red.  I'm wondering if that is a result of the moonlight washing things out, or maybe some aerosol or smoke in the atmosphere, or something like that.  My Jupiter image came out rather colorless indeed.

I only reluctantly packed up and went home at 11:15 PM - the atmosphere was getting more steady, and I wanted to try some different things.  But I had to be at work the next morning, so off to bed!  I really miss imaging DSOs - my last one was over a month ago - but planets are fun too.  And you can actually see them in the telescope - sometimes better than the camera can!



Wednesday, August 22, 2018

#156 - Sunday, August 19, 2018 - Astronomy Merit Badge

One of my coworkers leads a local high-school-aged Boy Scout troop, and asked if I'd be interested in teaching the Astronomy merit badge.  I had let my Boy Scout membership lapse after I taught another STEM merit badge back in 2015, so I renewed my membership and sent in my paperwork to certify as an Astronomy merit badge counselor.  Then I got to work planning.

I am a Girl Scout troop leader, and I've been a Girl Scout continuously since 1998 when I was a Brownie.  It's really interesting to see how different the boy's and girl's programs are.  The two Boy Scout merit badges I've taught are very rigid, knowledge-based recitations of facts.  After the last STEM merit badge I taught, their troop leaders were quizzing them on questions in the requirements list.  The Girl Scout program, on the other hand, encourages exploration of a topic, and looks at multiple aspects on the theme of the badge.  They often include options to speak to people in a related career field about what they do.

For example, here is one of the requirements of the Boy Scout Astronomy badge:

3.    With the aid of diagrams (or real telescopes if available), do each of the following:
a. Explain why binoculars and telescopes are important astronomical tools. Demonstrate or explain how these tools are used.
b. Describe the similarities and differences of several types of astronomical telescopes, including at least one that observes light beyond the visible part of the spectrum (i.e., radio, X-ray, ultraviolet, or infrared).
c. Explain the purposes of at least three instruments used with astronomical telescopes.
d. Describe the proper care and storage of telescopes and binoculars both at home and in the field.


And here's one of the requirements for the Girl Scout "Sky" badge, which is a Senior-level badge (9th-10th grade):

It was a bit of a struggle to come up with some ways to make teaching the Boy Scout badge requirements interesting - but I made a powerpoint of just pictures, and let the force of my science enthusiasm make the interest.  I made a point of mentioning my Girl Scout experience, my occupation, and my physics degrees :)  

I only had an hour and a half to cover both the requirements that are very much "let me tell you about this thing" and to show off some sights in the telescope.  I brought my 8-inch Schmidt-Cassegrain along on its Celestron NexStar SE mount, as well as my Oberwerk binoculars that I won at an astronomy symposium in 2016 so that I could show the difference between refractor and reflector, and between binoculars and a telescope, in one swoop.

Their meeting ended at 9, but the sun set at 8:30, so the planets popped out one by one as soon as we got outside toward the end of the meeting.  The parking lot of the church they met at was brightly lit, but the sky was fairly open, so planets made easy targets.  First was the Moon, which always surprises and delights people because it's something you see all the time, but seeing the amazing detail of the craters in a big telescope is really something else.  I trained both instruments on it so that they could compare.  Next was Venus, which was a beautiful crescent, slightly less than half-lit.  This was perfect, since I'd spent a little time in the talking portion on why Mercury and Venus have phases, but the others don't.  After Venus I worked across the sky from west to east, hitting up Jupiter next, which was peaking out its red spot low and to the right, and had all four of its Galilean moons on brilliant display off to the right (SCTs flip images left-right).  Next was Saturn, which is also a real crowd-pleaser, since it looks very much like you just hung a picture of it in front of the telescope.  It's always so sharp and unreal-looking.  It's my personal favorite at the eyepiece.  And, finally, Mars, which was brilliant.  It's so big right now!  

The meeting ended too soon, and the boys took off home.  We took a group photo, but there are rules, especially in Scouts, about posting images of minors on social media.  So I blurred the boy's faces, since I don't know who all has given consent, but also wanted to share the image!


Tuesday, August 21, 2018

#155 - Saturday, August 18, 2018 - Could Somebody Invent Some Darn Cloud Filters Already?

I've still got my hands on the Lumicon off-axis guider, and I am determined to get longer than a few minutes of guiding on it with my Celestron 8-inch Schmidt-Cassegrain riding atop my Celestron Advanced VX mount!  This setup is of vital importance to get working.  It is both lightweight and has a small field-of-view, which is a hard combination to get.  Currently, I have two "easy" setups - the club's memorial telescope, which is a 5-inch refractor that lives under a backyard dome out at our observatory and requires no setup besides slapping my cameras on it; and my AVX mount with my 3-inch Borg refractor, which requires a little more effort, but the large field-of-view is very forgiving of tracking and guiding errors.  Both of these setups are refractors, which are great for big targets like nebulae and some of the larger galaxies, but not so great for small targets like planetary nebulae, most galaxies, and planets.  The easiest setup, the club's memorial telescope, has the additional drawback of not being an apochromatic refractor, meaning that my stars have these blue halos around them - which are far more pronounced in my awesome ZWO ASI1600MM Pro astrophotography camera than in my Nikon D5300 DSLR.  My 3-inch Borg refractor is an apo, but does require setup and me hauling gear in and out of my apartment.

The club's memorial telescope - a Vixen 140mm neo-achromat refractor on a Losmandy Gemini G11 mount.

My 76mm Borg aprochromatic refractor on my Celestron Advanced VX mount.  Shown here with my DSLR.

In addition to the two "easy" setups, I have one "hard" setup - my Celestron 11-inch Scmidt-Cassegrain on my Celestron CGE Pro mount.  But there are a few problems with this setup: it's heavy, it takes forever to put together, and the mount is actually having a few problems at the moment.  However, the 11-inch SCT is excellent for small targets, having a field-of-view of less than half a degree (compared to 2-3 degrees for the refractors), making it perfect for those itty bitty planetary nebulae and the more distant galaxies.  I call this one "The Beast."

My 11-inch Schmidt-Cassegrain on my Celestron CGE Pro mount down at the Texas Star Party this year.

Now, I primarily use my 8-inch as either my outreach telescope or a planetary imaging scope aboard my Celestron NexStar SE alt-az mount, which is not good for photography but is super easy to use (and the very short exposure times for planets make it fine to use for that application as well), but I wanted to try to utilize it for another purpose: lightweight deep sky imaging.  I say "lightweight" because my 11-inch weighs 28 lbs, while the 8-inch only weighs 13 lbs.  So I decided to pair it with my Celestron AVX mount, and I got to start trying that out last month.

One tool will make this idea much more possible: an off-axis guider.  Rather than attaching my 4-lb Borg to the top of the C8 and cause further complication with the weight distribution, I can attach a tiny addition to the back of the tube and autoguide using that!  However, my testing so far revealed two problems: a lack of bright-enough stars to guide on in the small pick-off mirror, and some serious backlash in the declination axis.

Saturday night, I got to try out a possible solution to one of those problems: the QHY5L-II camera.  Currently, I guide with the QHY5 red hockey puck, which is fairly old and not nearly as sensitive as newer guide cameras.  Fellow astrophotographer John let me try his camera that evening.

Back of my C8 with my ZWO ASI1600MM Pro camera attached (red) and John's QHY5L-II guide camera (silver).  

Now, all of the forecasts promised it was going to clear right about 9 PM - all of them!  Even my two astronomy forecasts, which show high-altitude clouds (most regular forecasts don't include these, since it will still seem "clear" to the casual person).  But nope!  'Twas not to be.  There were slow-moving high cloud banks rolling through until 11, and there was a haze that did not dissipate.  However, up at zenith, I was able to see stars at least, so I slewed to the Dumbbell Nebula so I could at least test the guide camera.  In addition to the camera, I also borrowed a small front counterweight from John, which I taped to one of my Vixen dovetail clamps for my Borg scope and slid onto the front of the dovetail of my C8 to help with balance.  We were able to find a pretty good balance point.  It's hard to tell with the AVX, though, since the axes are pretty tight and it doesn't swing freely like other mounts do.

Results were good!  After taking dark frames to beat down the background noise on the sensor, I was able to see several potential guide stars in the image with minimal noise!  Finally, some progress.


Unfortunately, the backlash in the declination axis was still, present, despite the careful balance.  My polar alignment was good, and the way that it flips around the axis would seem to indicate that it's not polar alignment.  In addition, I could see the pause when changing directions in dec when I was looking at stars in the main camera.  *sigh*  So I'm not entirely sure what to try next on that front.

I tried taking images anyway, but they all were streaky in dec, even at only 60 seconds.  Now, the seeing wasn't great either with all the clouds and haze, so it still wasn't a true test, but I think I'm still going to have to figure out this backlash issue.

It's been over a month since my last deep-sky image - it's summer time, with all of these fantastic targets to image, and I'm dying! 😭😭  Cloudy and moonlit weekend nights don't help!  The next new moon (or even third quarter), I'm just going to bring my refractor out and image on that instead!  And keep brainstorming ways to get the C8 to work.


#154 - Tuesday, August 14, 2018 - Passing It On

I've been super busy lately, so sorry for the delayed posts!

This past Tuesday night, I did an outreach event with a few astronomy club members (Phil, Terry, and Sarah) out at a soccer complex a short drive from where I live.  As per usual, I brought out my 8-inch Celestron Schmidt-Cassegrain on my Celestron NexStar SE mount, which is an alt-az mount that is not ideal for photography, but is great for outreach due to its ease of setup and use.  The telescope, however, is excellent - planets are large and well-resolved due to its long focal length and large aperture, and with a focal reducer attached, I can pull in some gorgeous nebulae, galaxies, and globular clusters that are sure to please the crowd.

It wasn't a totally clear sky, and it was a little hazy, but it was clear enough to hit the important targets: the planets!  The general public don't typically have the appreciation for small, dim, fuzzy galaxies that we star-nerds do, but boy are the planets awesome at the eyepiece.  And this summer is a bountiful harvest of planets indeed - Venus, Mars, Jupiter, and Saturn are all readily visible, and if you wait till later in the evening, you can nab Uranus, Neptune, and Pluto too if you're somewhere dark enough, have a big enough scope, and know what you're looking at.  (I have not, in fact, tried for Pluto yet.  I need to.  Soon.)  

Not only did we have the planets, but we also had a rather fetching view of the crescent Moon before it set.  I threw my QHY5 guide camera on for a couple quick videos early on in the evening, and they came out really nice!  Despite the haze, which reduced transparency, the seeing (atmospheric steadiness) was actually pretty good.


Date: 14 August 2018
Object: Moon
Camera: QHY5
Telescope: Celestron C8
Accessories: N/A
Mount: Celestron AVX
Frames: 106/500
Exposure: 25 ms
Stacking program: RegiStax 6

Date: 14 August 2018 
Object: Moon
Camera: QHY5
Telescope: Celestron C8
Accessories: N/A
Mount: Celestron AVX
Frames: 1: 109/460
Exposure: 25 ms
ISO/Gain: N/A
Stacking program: RegiStax 6

This outreach event had several young kids in attendance with their parents, which is always a treat.  Oftentimes, neither the kids nor the parents have looked through a telescope before, and that is truly a magical moment.  


Occasionally, I get kids that come through who have some knowledge of the planets already, which they are eager to show off, and that is really fun.  Tonight, I had a special guest - a 7-year-old girl named Makenna who was absolutely enthralled with the telescope.  We looked at Jupiter, Saturn, and Mars first, and a few bright stars were easily visible through the haze, which she also wanted to see.  Now, for most of us, stars are not terribly exciting in the eyepiece, unless it's a tight double star or a lovely open cluster or something like that.  But to Makenna, seeing a star in the eyepiece was like magic.  She asked if she could control the telescope, and I let her punch the keys on the hand controller, which was very exciting for her.  Finally I just let her scroll through the star catalog and select stars at random, most of which I wasn't familiar with, and it was anyone's guess as to whether we'd be able to see them or not - whether they were far enough up above the cloud bank off in the distance (I had the filter turned on to keep it from going below the horizon).  Oftentimes, however, a telescope with a large enough aperture can pick up all kinds of stuff you can't see through the clouds because of its light-gathering power.  I also directed her to see some double stars, like Mizar and Alcor.  I pulled in a few deep sky objects as well, although there weren't many to choose from in the light-polluted suburbs, so one of them was the Ring Nebula.  Our exchange went something like this:
"So this is called the Ring Nebu--"
"OOOH"
"It's a dying star--"
"DYING?!"
"In about 5 billion years, our own Sun--"
"WOW!"
😁😁😁😁

I also told her about how I'm a scientist and get to discover new things.  Before she left (we almost had to pry her off the telescope), she told her parents that she wanted to be a scientist.  Be still my heart!!

I didn't get home until nearly midnight, so getting up for work the next morning was a little rough, but it's worth every minute of lost sleep!

Monday, August 13, 2018

#153 - Saturday, August 11, 2018 - Failure Just Makes Room for Future Success

As with anything that is hard, sometimes you have fabulous successes, and sometimes you have crushing failures.  Saturday night was more of a temporary setback kind of failure night, but with a couple of success points to raise its overall level to decent.  I didn't get much of what I intended out of the night, but got a couple bonuses to make up for it!

Saturday night was Members Night for astronomy club members out at the observatory, and we had a delicious Italian-themed potluck, to which I brought my baked mac & cheesay.  It was a staple while I was in braces in 2016 and 2017, and I'd make it the night after I got an adjustment and it would tie me over for the next couple meals until I could eat solid foods again.  There was a shocking lack of dessert, so my heroic minion Miqaela ran out and got some delicious ice cream for us!

As the sky started to get darker, I got my gear set up - my Celestron 8-inch Schmidt-Cassegrain riding atop my Celestron Advanced VX mount, the Lumicon off-axis guider I'm testing, and my ZWO ASI1600MM Pro as my imaging camera and QHY5 red hockey puck as my guide camera.  I removed the Vixen dovetail bar I had on top of the C8 for the refractor I had previously used to guide it to save a little weight, and I was able to only put on one counterweight instead of two, woot!  Then I took my time carefully balancing, since I had some serious backlash in the declination axis last time I was out.  I wasn't quite able to balance it still however, so I had to get clever.  Fellow club member Jim had mentioned a counterweight attachment he had that slid onto the front end of the dovetail that holds the scope to the mount, which got me thinking - I had something like that attached to my Borg refractor.  I grabbed the ring I use to mount the Borg, which is attached to a Vixen dovetail clamp, and used some gaffers tape to secure a waterbottle to the inside of the ring.

An elegant counterweight from a more civilized age.

Bonus points, its position adjustable, so if guiding still looked bad, I could move it out or in to help balance better!

Since we still had a ways to go until it was dark enough for me to polar align, I took off the focal reducer I had on for balancing purposes and I imaged Saturn and Jupiter.  Well, first I went and looked through someone's scope to see if the seeing was good enough to image them - there was a high haze moving through, and I wasn't sure if it had entirely dissipated.

This is where I met my first challenge of the evening: I couldn't find the dang planet!  Sometimes, my finderscope gets nudged around inside the box (especially when my cat lays on the box at home), so I wasn't sure how accurately aligned it was.  Also, I wasn't in focus yet, so I was most likely looking for a big de-focused donut.  It still wasn't showing up in the camera, so I grabbed an eyepiece and put it in the guide camera port on the off-axis guider, focused the scope, and slewed around.  I found the nearby wide double star Zubenelgenubi, and I rotated my phone so that SkySafari's map lined up with their angle to each other, but I still didn't quite come across it!  Finally I took the camera off, put in my 40mm eyepiece, and found it straightaway.  Then I centered the planet, adjusted my finderscope, put the camera back on, and focused.  Finally!   It came out okay.
Date: 11 August 2018
Object: Jupiter
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik LRGB Type 2c 1.25" filters
Mount: Celestron AVX
Frames: L: 1252/2001
    R: 995/2003
G: 732/2005
B: 665/2002
Exposure: L: 20 ms
  R: 50 ms
  G: 40 ms
  B: 70 ms
ISO/Gain: 139
Stacking program: RegiStax 6

Saturn was next, which was easier to find now that the finderscope was aligned and my camera was focused.  This one came out the best.
Date: 11 August 2018
Object: Saturn
Camera: ZWO ASI1600MM Pro
Telescope: Celeston C8
Accessories: Astronomik LRGB Type 2c 1.25" filters
Mount: Celeston AVX
Frames: L: 299/1505
    R: 304/1560
G: 148/1500
B: 632/2002
Exposure: L: 55 ms
  R: 150 ms
  G: 150 ms
  B: 150 ms
ISO/Gain: L,R,G: 139
  B: 200
Stacking program: RegiStax 6

Planetary image processing is really interesting.  You start out with a video where nearly every frame has some kind of atmospheric distortion in it.  Any single frame doesn't look that great.  Then you run it through RegiStax or AutoStakkert, and it ranks them by quality and aligns them all.  You make a cutoff on quality, and it averages them with a moving average.  The result is this very fuzzy thing.  But then you apply the voodoo magic that is wavelet deconvolution, and you get this spectacular, clear planet that seems impossible to have been taken through 300 miles of light-distorting, messy atmosphere.  
The luminance frames from this Saturn data collect.
And by "many," I mean hundreds to a few thousand.

Then it's just putting the LRGB channels together, fixing the color, brightness, and contrast a bit, and poof!  You've got an epic planetary image.  (See this post for a how-to).

Mars wasn't up yet, and I was antsy to get some deep-sky imaging done with this off-axis guider, so I polar aligned (which went smoothly), aligned (which also went smoothly, since the finderscope was now aligned), and then slewed to M16, the Eagle Nebula, which I had collected luminance frames for previously but needed color frames.  

Once I got it centered, I went over to PHD2 and got the guide camera up and running, but the only stars I had were a few elongated smudges.  Remember, I've got a Schmidt-Cassegrain, and even with the focal reducer/field flattener, the stars on the edge are not terribly point-like.  They were too dim for PHD to do much with - it kept losing them in the noise.  I did get one calibration to work, but the backlash was really bad in declination, and the calibration was a mess, so I discarded it and adjusted the homemade counterweight.  It was already at the end of the dovetail, though, so I tried to move the whole telescope forward while it was still pointing at M16.  Bad idea - the RA axis clutch slipped, invalidating my mount's alignment model.  So I slewed to home, slid the telescope forward some more, and then re-aligned.

I gave up on M16 after that and went over to M27, the Dumbbell Nebula, since M16 was pretty far west at this point and in the heavy skyglow of light pollution.  M27 was nice and high, away from the haze and light, and it's bright enough that I could take shorter frames if needed.  But I couldn't find a bright-enough star there either, even when I moved the target around to try and bring a brighter star into the field-of-view of the guidescope.  On the bright side, though, I was showing our experienced astrophotographer how I couldn't get the plate-solving program AstroTortilla to work with my ZWO camera (it will move your telescope to get your object centered for you based on the positions of bright stars in the image, and I had gotten it to work on my DSLR at the Texas Star Party, but not the ZWO), and it magically worked!  Small victory.  That will be very helpful for meridian flips.

After I couldn't get any good guide stars, I decided to give up on the 8-inch until I got a more sensitive guide camera (which, thankfully, are rather cheap, astronomically speaking), and switch to my Borg refractor, which I'd also brought with me.  I'd already taken off the 8-inch and opened up the Borg's case when I realized that that wasn't going to work - I'd lent my minion Miqaela the field flattener that that telescope desperately needs.  She was borrowing an Explore Scientific apochromatic refractor from a fellow club member, and it also really needed that field flattener.

I decided instead to perform another experiment: Periodic Error Correction, or PEC, is a routine I hadn't tried yet on any of my mounts.  Basically, you record the tracking errors in the RA gear as it rotates around, and then play them back, which un-does them enough to be a suitable replacement for guiding in some cases, if your polar alignment and balance are good enough.  On the AVX mount, you only have to record it once, and it stores it in memory.  However, you needed to use your guide camera for it, and plug an ST-4 cable directly into the mount.  I'd never done this before, and I didn't have the ST-4 cable with me.  Luckily, the club's memorial telescope setup had one, and they're the same across all manufacturers, so I was able to borrow it.  I used the USB cable on my QHY5 to center nearby star Sham and focus the camera, and then the mount did PEC all on its own.  It took about 10 minutes to complete, since that's the time it takes to make one revolution.  When it was done, I turned it on, and took some 2-minute test frames.  The stars came out looking pretty fuzzy.  So I turned it off, and then I just had streaky stars.  So I dropped the exposure time to 30 seconds and just did unguided, un-PEC'd exposures.  I lose several to periodic tracking error, but you can take a lot when they're only 30 seconds long.  Thank goodness this camera is so sensitive.

30-second raw exposure, gain 139, on my ZWO ASI1600MM Pro of M27 Dumbbell Nebula.


About 80 luminance exposures in, I realized that the cooler wasn't running.  😒  That's when I finally gave up!!

At this point, it was about 2:30 AM, but the sky was gorgeous, my DSLR was clicking away on a tripod capturing Perseids, and I wasn't tired yet.  There was only a few of us left at the observatory to watch the Perseids - Miqaela, Bob and I.  But Miqaela was still taking images on the Heart Nebula, and several of the planets were up, so I took the focal reducer off again and decided to grab some planetary images, and then go home to bed.

Mars was first on my list.  I accidentally forgot to switch back to SER LuCam videos from the FITS format I use for my still frames, and because of that, the final images turned out rather dark.  I had to brighten them in RegiStax, which also brightened the background, which gave a weird effect when I re-darked the background.  However, you can see some hints of terrain features.  And an icecap that came out pinkish.

Date: 11 August 2018
Object: Mars
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik LRGB Type 2c 1.25" filters
Mount: Celestron AVX
Frames: L: 594/2005
    R: 924/2002
G: 350/2001
B: 394/2003
Exposure: L: 0.1 ms
  R: 3 ms
  G: 3 ms
  B: 10 ms
ISO/Gain: 0
Stacking program: RegiStax 6

Mars was so stinking bright that not only did I have to use very short exposure times, I had to turn the gain down to 0 just to use those exposure times!  I guess I could have gone shorter - the ZWO ASI1600MM Pro will do as short as 32 microseconds, or 0.032 ms - but lower gain means more dynamic range anyway.  Of course, the short exposure times gives me the secondary benefit of ultra-fast frame rates - over 100 fps!  That means more frames in the good moments of atmosphere.

I tried for Uranus and Neptune too, but didn't get much.  I've seen them both in that telescope with eyepieces, and they definitely have color and are disc-like as opposed to pointlike, meaning you can definitely tell they are planets rather than stars.  But I couldn't really get the exposure time quite right, and they still came out saturated, although it didn't look like it in the histogram.  They were also really small, so I might try using a Barlow next time, and maybe use my smaller-chip QHY5.

In addition to all of the imaging I had planned for the night, it was also the Perseids meteor shower!  So I sat back and looked up whenever I was waiting for something to happen.  I saw about 5 total, while my fellow club members combined spotted about 25 over the course of the night.  I had my DSLR set up on a tripod facing northeast toward Perseus, and I managed to capture 7, but only two were bright enough and fully contained in the image.  You can see the color change, it's really cool!  I had 15-second frames at ISO-1600 set to run on the internal timer all night.
This one almost points to the Andromeda galaxy.

The meteor is on the upper left, while an airplane is on the upper right.

On top of that, there were three Iridium flares, which all happened to be in the same area of the sky as I had my camera facing!  This phenomenon comes from the Iridium constellation of communications satellites, which reflect light from the sun strongly back at Earth periodically during their orbits.  There are dozens of them in orbit, so many nights out of the year, you can see one.  They only last about a minute, but they start out very dim, and then get very bright - brighter than the stars, usually - and then fade back out.  An app like Heavens Above can tell you when the next one is, and SkySafari will alert you as well. 
A really bright one!  The gap is a result of the 2-second gap between successive frames on my camera.

A dimmer one in nearly the same place, only a few minutes later - probably a replacement for that particular satellite.  Also, my camera lens started to fog up before I moved the hand warmer I use as a dew heater closer to the front.

This one was really low, so neither Heavens Above nor SkySafari warned us.  I just happened to see it when I was scrolling through my images. 

I used the same software I use to make star trails, simply called Startrails, to stitch the successive images together.

At 3:10 AM, just after my last dataset on Uranus but before I started packing up, I remembered that the Parker Solar Probe re-scheduled launch was set for 3-something that morning, so I found a NASA stream online and turned the volume up.  Bob, Miqaela and I watched the awesome sight of a United Launch Alliance Delta-IV lift off from Cape Canaveral and deliver the vehicle up into space.  I'm not sure it will ever get old, even when spaceflight becomes routine.  I also always marvel when an airplane takes off and lands, even though I've flown more times than I can remember.  What a feat of human ingenuity.  The Parker Solar Probe will skim the surface of the sun to study the solar corona and solar wind.  An interviewee on the NASA live stream compared the distance to a football field; if the sun were at one end, and the Earth at the other, the Parker probe will be at the sun's 4-yard line, seven times closer than any spacecraft has gone before.  One of the questions it will strive to answer is why the corona, which is the sun's tenuous outer atmosphere, is over 1 million degrees Kelvin, even though its surface is only 5700 Kelvin.  It will swing between Venus and the sun seven times, and orbit the sun 24 times, getting closer each time.  The first perihelion (closest solar approach) will be this November, so pretty soon.  The 24th won't be until 2025.  So many years of solar exploration!  

So Saturday night was a mixed bag, but hopefully a more sensitive guide camera will help.  Off-axis guiding will make a lightweight setup with my 8-inch possible, which is a huge capability expansion, since I won't have to use my massive CGE Pro and 11-inch SCT to do narrow field-of-view imaging of small galaxies and planetary nebulae.  Then I just have to get the balance right to reduce the backlash in declination.  Here goes!


Sunday, August 5, 2018

#152 - Saturday, August 4, 2018 - Testing the Lumicon Off-Axis Guider

It's been a few weeks!  Of course, you  know how it goes - you get a shiny new astronomy toy, and it's guaranteed to be cloudy for weeks!  And boy did we get rained on and stormed on.  That's all my fault, folks - I got an off-axis guider to test from Lumicon!


The week before I gave my talk on The Astro Imaging Channel, I logged on to watch Cary Chleborad's talk on his company Optical Structures and their ownership of Lumicon, JMI Telescopes, Astrodon, and Farpoint.  Cary asked after my talk if I'd be willing to test one of a series of off-axis guiders that is made to already have the spacings correct for specific astro-camera manufacturers - in my case, my ZWO, plus a Gosky filter wheel.  This was my first time using an off-axis guider; up till now, I've been using a guide scope.  There are some big advantages to off-axis guiding, especially for Schmidt-Cassegrain telescopes, like my Celestron 8-inch:
1. Weight.  I've been testing using my C8 on my Celestron Advanced VX mount, which has a payload capacity of 30 lbs (not including the counterweights).  With the C8 and my Borg refractor acting as guide scope, I was sitting at about 19 lbs or so.  The rule of thumb for astrophotography is you want to stay at half or less of the payload capacity of the mount in order for the guiding and tracking to work well.  With the off-axis guider (OAG), I can take off the Borg, and just have this very lightweight accessory hanging off the back of the scope.
2. Flexure.  When the guide scope is mounted on top, or on the side, or wherever, as the scope moves around from one side of the meridian to the other, the weight distribution changes, and gravity pulls on different parts of your rig.  This can cause the guide scope to point ever so slightly off of where you calibrated it at the beginning of the night, which will make guiding less effective over the course of the night.  With an OAG, its optical path is the exact same as your primary camera, so there is no more possible difference between the guide camera and the primary camera.
3. Mirror flop.  Schmidt-Cassegrain telescopes have big primary mirrors that are not attached to the back of the telescope - rather, they are held in the center by a baffle (the tube where the light cone from the secondary mirror is directed down to your eyepiece), and move up and down when you turn the focuser.  Again because of gravity, as you cross the meridian and head down toward the horizon, the mirror will tend to shift, since it's not bolted into place.  This will not only cause you to lose focus sometimes, but it is also a source of flexure, since the primary camera will now be pointed to a slightly different angle than you calibrated the guide scope to at the beginning of the night.  With an OAG, when the mirror moves slightly, what the guide camera sees will move with it, along with the primary camera.

However, there are a few drawbacks, namely being able to find a guide star.  OAGs work by having a prism on the edge that picks off an area from just off the camera's field of view.  It's a pretty small field, so you may not have a whole lot of choices of stars to guide on.


Looking down inside.  At the bottom is the ZWO camera's giant sensor, and then you can see the pick-off mirror on the right, and the QHY5's sensor reflected back at you.  


The directions say to line up the mirror with the long end of the primary camera's chip, but the filter wheel ended up being too close to get enough clearance to rotate it around, since the guide camera barrel gets in the way of the filter wheel.


Not only that, but the screws that attach the OAG to the 2-inch-barrel-sized connector that screws onto the filter wheel are hard to turn because they're so close to the filter wheel.

I got out to the observatory around 8:30 PM and got my telescope rig put together, and then I added on the OAG and cameras.

Lumicon's off-axis guider attached to my Celestron C8, with my ZWO ASI1600MM Pro as the primary camera and my QHY5 mono as the guide camera.

Once it got dark enough, I slewed over to Arcturus to get into focus.  I had two very lucky things happen: the first was that my finderscope was actually pretty close (I've been having issues with it lately), and the second is that the telescope happened to already be nearly in focus!  So I didn't have to turn up the exposure time to try and see a huge white donut, and I didn't have to take off the camera and throw on an eyepiece to make sure that there was actually even a star in the field.  So that saved some time!

Next, I slewed the scope to move the star to one side of the image and then the other to try and get it onto the guide camera's field-of-view, but I didn't see anything.  So I detached the QHY5 and put a 25 mm eyepiece there instead, which happened to be in perfect focus with the ZWO camera.  After slewing around a bit, I found it, put it in the middle, and put the QHY camera back on.  What I got - and forgot to take a screenshot of - was a crescent-shaped blob, which was the star very out-of-focus (so a big donut) but cut off on the edges since the prism only grabs part of the light cone.  I pulled the QHY camera out to try and find the focal point, but I actually needed it to be closer, which wasn't going to work.  Hmm.  Maybe I was mis-remembring the schematics Cary had sent me and the filter wheel was supposed to go before the OAG?  

I took the cameras off to try and figure out whether I had all of the necessary adapters to put the filter wheel before the OAG, but I didn't.  I needed something that would accept the 2-inch eyepiece barrel size of the telescope-end of the OAG that I could attach to my filter wheel, but I didn't have anything like that, even among all of my various adapters I've collected over the last three years.  So I resigned myself to imaging monochrome without the filter wheel, at least for testing purposes.  I attached the ZWO camera directly to the OAG and brought it into focus, but then I still couldn't get close enough with the QHY camera.  Then I asked myself, did I need the primary camera to be closer, or farther away, to work?  I found a star with an eyepiece attached to the guide camera slot, and then focused the telescope so that the guide camera was in focus when it was about halfway inserted.  Then I detached the ZWO camera and held it and pulled it away from the telescope to see if the focus was getting better or worse.  It got better, and I could see how much extra space I needed to have both the ZWO and the QHY in focus at the same time.  Being farther back is good - it's easy to add extenders.  My ZWO camera came with a few, including a 21mm-wide screw-on extension tube.  I attached that to the camera, and then I attached the filter wheel, and then the OAG got attached to the telescope.  I forgot to get a picture last night, so here's one I took today off-telescope.


Once I put the filter wheel back on and the 21mm spacer, I was at last able to bring the guide camera into focus!  It was hard to get it perfect because it would adjust a bit once I tightened the screws, and it was hard to hold steady enough to tell whether the star was really in focus.  I did get a parfocal ring on there though, and I'm going to buy several of those 1.25" connectors and parfocal rings so I can have one for each of my configurations where the guide system doesn't include a focuser, such as when I use my Orion 50mm mini-guider with my Borg.

All right, so I was finally ready to start trying to guide.  It was after 1 AM.  Some serious clouds had been rolling through, even though none of the five forecasts I use had predicted any, so good thing I wasn't really trying to image anything.  It was starting to clear up, but it was the most clear to the east, so I tried globular cluster M15 first.  However, my gotos were not great, even after I polar aligned using SharpCap (which is amazing by the way, and totally worth the $15/year for the subscription to be able to use it - basically turns your camera into a Polemaster), and my finderscope was dewing up, making it hard to find whatever star the Precise Goto routine picked, especially from my light-polluted area.  I didn't see M15 in the primary camera.  So I tried the Dumbbell instead - still no dice.  I probably wasn't using the right star for the precise goto.  Then I tried M16, the Eagle Nebula, since I could see one of the precise goto stars, Nunki, pretty well, but I couldn't find any guide stars, even in star-filled Sagittarius.  I thought I saw one or two, but they were kind of dim and smudgy, so I slewed to Vega to try and re-focus the guide scope again.  Since I was already up there, I decided to try the Ring Nebula, M57.  I could see a dim star or two in the FOV of the guide camera in PHD, but not with enough SNR (signal-to-noise ratio) - PHD kept losing it during calibration.  Taking darks probably would have helped, but for some reason every time I try to do that, when I turn on the dark subtraction, the image turns pretty much all white.  Hopefully there's an update out there for PHD that fixes this problem.  (And when I say PHD, I really mean PHD2).

Finally, after attempting to calibrate a few more times, a bright star drifted into view of the guide camera!  I edged M57 over a bit to bring it far enough into the guide camera's image to be able to use, and then I was finally able to calibrate.  It was bright enough that I could use 3s frames.  I don't think it was Vega, since I had looked at that in PHD as well and it was much brighter, but it was probably one of the other constellation stars of Lyra.  The calibration was still a little wonky though, but I knew this was more of a problem with the declination backlash I was getting rather than the OAG, since I'd seen that backlash while I was aligning the scope earlier.  The AVX is hard to balance because its two axes are not nearly as "loose" as other mounts I've used, so you kind of have to guess as to whether you're close to balanced, and you can't make it a very precise balance, in either axis.  I'll have to work on that.  I'm also going to need a front counterweight for that scope, or a longer dovetail bar.

All of the tiny white dots are noisy pixels.  That smudgy thing in the lower third of the center of the image is another star, but the SNR wasn't quite high enough to use.

I'll point out here real quick that I was using a 0.63x focal reducer on my C8, turning its 2032mm of focal length into 1280mm.  Shorter focal lengths are more forgiving of guiding errors, plus the faster focal ratio of f/6.3 rather than f/10 makes for brighter, higher SNR images.

All right.  So did it work?  When I re-selected the star in PHD every 10 minutes or so to kind of re-set the guiding since the dec backlash was so bad, it did pretty all right!  Below are JPGs of the raw FITS files at various exposure times.


2-minute exposure


5-minute exposure


7-minute exposure

Not bad!  I wasn't able to get much more than 3 minutes reliably using my Borg 76mm refractor as a guide scope, probably in large part due to the weight.  I think if I can get the declination axis properly balanced, these results would look even better - you can see a slight elongation of the stars if you zoom in.  This is really exciting!  I'll try it again on my next night out and see.

Before I packed up, Mars was burning bright in the sky, and the third-quarter moon was just beginning to rise, so I took off the OAG and the focal reducer.  For planetary bodies, you definitely don't want the focal reducer, since you want as much resolution and magnification as possible.  While the air had been pretty steady earlier in the evening according to my fellow club members (I was too busy to actually look through the scope), I could see the edges roiling while I was taking the data.  But it didn't look too bad.  And it appears as though that dust storm is clearing up!
Date: 4 August 2018
Object: Mars
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik LRGB filters Type 2c 1.25" 
Mount: Celestron AVX
Frames: L: 1087/2005
    R: 1388/2004
G: 810/2002
B: 436/2001
FPS: 30-60 fps
Exposure: L: 15 ms
  R: 30 ms
  G: 50 ms
  B: 150 ms
ISO/Gain: 50
Stacking program: RegiStax 6

By the way, the "frames" metric is how many frames made it past the quality cutoff I chose for each dataset out of the total.

The aberration around the edges isn't real - it's a result of the fact that when I align the color channels by hand in Photoshop, I can only move in intervals of whole pixels.  It's hit-or-miss as to whether I can get RegiStax to align them for me (and it can do sub-pixel, I think), and when it can't for some reason, I have to do it myself in Photoshop.  Although that is a real polar ice cap on the bottom. :)

The third-quarter moon was rising from behind the trees after I finished imaging Mars, at around 2:30 AM.  I knew I should be going to bed, but I don't often get to image the side lit during this phase, since it's up so late.  It was still low on the horizon, so the atmosphere was really boiling, but these still came out neat!  I also got a tip from the venerable Robert Reeves (whose got a Celestron telescope named after him now, and whom I got to meet at the Texas Star Party - and nab a Meade DSI Pro camera from) to try out a filter in Photoshop CC called Shake Reduction.  It's no substitute for good atmosphere, but it helped a bit!

Date: 4 August 2018
Object: Moon, Third Quarter
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik LRGB Type 2c 1.25" filters
Mount: Celestron AVX
Frames: 816/2006
Exposure: 25 ms
Gain: 50
I didn't apply the filter to this one - it didn't do much for it

Frames: 476/2002
Exposure: 40 ms
Gain: 139

I call this one "On the Shores of Silver Lake" 😁
Frames: 534/2007
Exposure: 30 ms
Gain: 139

Frames: 973/2007
Exposure: 20 ms
Gain: 139

I finally packed it in at 3 AM, and hit the sack at 4 AM!  Late night, but at least I got some images out of it.  And I got to test that Lumicon off-axis guider!  It was an exciting night.  Can't wait to try it again.