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!
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