Here's an image of Mars taken last Thursday night, roughly a day after opposition. (I tried to image Mars the night before too, closer to opposition, but ran into some trouble. Horror story below).
Midpoint timestamp: 2020-10-16 07:55.2 UT
Summary: 13.5 minutes total acquisition time.
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Details (skip if you're not interested in the details):
Equipment:
Meade 10" LX200-ACF mounted on an equatorial wedge
ZWO ASI290MM monochrome camera
Tele Vue 4x Powermate
ZWO Atmospheric Dispersion Corrector (ADC)
ZWO Electronic Filter Wheel with Astronomik Deep Sky RGB filters
Acquisition:
Seeing conditions were quite good, perhaps on the lower side of excellent, but still excellent. And the good seeing lasted through most of the imaging session.
Before imaging started, I made sure to collimate the telescope while I was waiting for Mars to rise above the building.
FireCapture was used to capture sequences, where each sequences is comprised of nine, 90 second videos, while alternating filters in the order of RGBRGBRGB. The Region of Interest (ROI), camera gain and the exposure time was set to keep the frame rate pretty high -- at about 125 fps or so. This corresponds to exposure times of about 7 or 8 ms or so. Refocusing and rotation of the ADC was done in-between sequences. This went on for about 4 hours, before during and after Mars crossed the meridian.
Processing:
Each video was processed with Autostakkert! using lucky imaging techniques. For each video, approximately 70 APs were used, and 50% of the frames were kept. This processing not only outputs images for further processing, but also produces roughly sharpened image to use for evaluation in deciding which images should be used, moving forward.
I was like a kid in a candy store. Many of the sequences had beautiful data. Usually, I feel fortunate if I end up with a single sequence that isn't garbage, but this night I found one good sequence after another. I chose sequence 6 for the image above, but it was just a coin flip. There were other sequences that were just as good.
Of course I had to delete most of the raw data, because, well, "terabyte." But I'll keep the processed data and maybe make a time-lapse video out of them if I can find the time.
Each image was then processed with Registax wavelet sharpening.
The Registax sharpened images were then combined using WinJUPOS: Three images captured with the Red filter to produce one combined Red image, and so on with the Green and Blue filtered images.
Gimp was used to place the combined images in their respective color channels. Then Gimp was used for curve adjustments, contrast adjustments, and saturation adjustments.
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Horror Story: I also tried to image the night before, just a handful of hours after opposition.
It was a dark and dewy night. The neighbors had long retired for their evening slumber. It was just me and the telescope sitting alone in the eerie silence. A chill was in the air. Mars finally rose over the dank rooftops, beckoning me. No, not beckoning -- goading me. Goading me to capture an image. Mars laughed at me as I centered the planet on the capture screen. A drop of dew fell from the rain gutter.
I twisted the focus knob. A strange apparition appeared on the screen. It was Mars, but it wasn't Mars. Something else was there: an apparition of some kind. "What in the world?" I asked myself. "That's too big for a dust mote." I clicked the button on FireCapture to change the filter from L to R, just to make sure. Nothing changed; the apparition was still there. It was like something was blocking my view of Mars. A ghostly something was in-between Mars and myself. I hit the button again, this time G. Still no difference. A sound -- a murmur -- whispered out. "What is that sound!?" B. "Mrraww" came from somewhere. Nothing else. It was a hushed, cagily whine. The apparition remained. "Good god," I squealed. "My filter wheel."
A couple of turns on some thumbscrews and I rushed my camera and filterwheel inside the house. I grabbed a precision screwdriver set that I had handy and tore open the filter wheel enclosure right there on the kitchen counter. Sure enough, the belt that drives the wheel had come partially off its tracks and was sort of jamming things up. The apparition was nothing more than the partition between filters and possibly a little bit of belt. "Well, that's easy enough to fix," I told myself as I rolled the belt back on its tracks and reassembled the enclosure.
Back outside I slid the camera and filterwheel assembly back into the ADC. No sooner than I turned to the laptop did I hear a loud clang. The camera and filter wheel had fallen out onto the concrete. "Ahhh, Gad, Jaysus <redacted> <redacted> dammit," I cried as I picked up the assembly off the cold, hard ground. "What Have I done?!" I pleaded for mercy to the stars and planets. "What. Have. I. Done. Guaaah!" Porchlights illuminated. Heads came out of windows.
I re-plugged the assembly back into the ADC, this time making damned sure the thumbscrews were quite tight. Dustmotes galore. If I thought that apparition before was bad, this was godawful.
They say that you only get to drop sensitive astronomical equipment on the concrete twice: once on the concrete and once in the trash. "Guaaahh," I yelped.
Back into the kitchen. I disassembled the filter wheel a second time. 'Removed the camera. I Grabbed the handheld air blower and blew air all around every nook and cranny for about 5 minutes. I put everything back together, not knowing what to expect next.
I reattached everything back to the telescope (paying extra attention to the thumbscrews, of course). R. The filter wheel changed position. No dust motes. "Oh, thank god." G. It seemed to work. B. Yep.
I recalibrated the filter wheel positions, just to be sure, and everything seemed OK. I don't know how it survived, but yet there we were, fully functional.
Mars was still laughing.
I suppose that's not much of an ending to this story, but I'll take it!
