Wednesday, October 21, 2020
#569 Mars Redux
|The ASI120MC, Shorty Barlow, and Meade flip mirror.|
Did I take a peek or two at Mars in 2018? Sure I did, but it wasn’t a very good year for the planet what with the dust storms and all. I’d been hearing, howsomeever, that this year’s apparition was turning out to be a Real Good one.
And….as I thankfully have frequently of late, one afternoon last week I felt the call of the backyard. “Time to get the C8 set up, I reckon.” What would I set up Mrs. Peel, my Celestron Edge 800, for, though? That was obvious. While we are now pulling away from the Red One, when Mars was at opposition on the 6th of October, we were a mere 62 million kilometers from that mysterious world, we won’t be as close again for 15 more years, and the planet is still awfully big and bright.
15 years? That will make your old Unk…well, “15 years older,” and I question whether I’ll be up to getting even an 8-inch SCT into the backyard by then. Frankly, thanks to the injuries I suffered last year, it ain’t exactly a piece of cake for me to get the freaking Advanced VX set up now. That being the case, I figgered I’d better take advantage of this Mars opposition. And I will, y’all, I will. The image you see here will just be the beginning, I hope. As I was during the BIG opposition of 2003, I plan to be in the backyard taking my humble planetary snapshots almost every clear evening.
First step, then, was deciding on the camera to use. Well, that wasn’t much of a decision to make since I really only have one planetary camera these days. Planetary camera? Without going into a lot of detail which will be amply explained by the links above, what you want for taking pictures of the Solar System is a camera with a small sensor which is possessed of many pixels. And you want it to output .avi video. You’ll take as many frames as possible and reasonable and stack those into a finished still image.
|Sky & Telescope's Mars Profiler helps you find your way across Mars. |
That’s when I began hearing about a new mainland Chinese company, ZWO optical. Looking at their offerings, I found they had a camera that appeared might do the job for me, the ZWO ASI120MC, a one-shot color job with a maximum resolution of 1280x 960 (all my other cameras hovered around 640x480). As above, when you’re imaging planets the idea is to take a lot of frames and stack them in the interest of reducing noise and catching moments of good seeing. The 120, ZWO said, was capable of up to 100 frames per second (fps) at lower resolutions and 20fps at max. That sounded right good to me, so I took a chance.
This was before ZWO, which is now one of the top CCD/CMOS astronomy camera vendors, hit the bigtime. When I ordered, they had no U.S. dealer; my little widget had to come all the way from the People’s Republic of China. Which it did in a surprisingly short time.
What was in the box when it appeared on the front porch of the legendary Chaos Manor South and your not-quite-so old Uncle got it into his hot little hands? Well, there was the substantial and, frankly, impressive camera itself. Metal, nicely finished in red. There was also a 1.25-inch nosepiece, a short USB cable, a CD with some software, and an IR block filter to make it easy to get shots with easy to balance color. Heck there was even a fisheye lens for the cam, which some folks have used to turn the 120 into an inexpensive all-sky camera.
Anyhoo, the little camera has been my sole Solar System imager over the last decade. Hey, I don’t aspire to become the next Damian Peach or Chris Go—even if I had the talent and dedication to achieve the results of those masters. As always, Unk is a dabbler. One night, I’m looking at a bright comet with a 3-inch refractor, the next I’m doing deep sky video, the next, spectroscopy. You get the picture. The ZWO proved to be simple to use and has produced results that have pleased me.
Oh, Unk did fib a bit. I do have another camera that would work well on the planets, my QHY5L guide cam. However, it’s black and white. I want color, and if you think your fumbling Uncle is gonna start shooting through RGB filters, you’ve got another think coming. It’s one-shot color all the way ‘round here.
By the way, the 120mc is still readily available from ZWO and their dealers. It’s a little more expensive than mine was, but you do get a little lagniappe for the extra dineros: the camera now sports an ST4 auto-guide output. Is the 120mc color version sensitive enough for guiding? Based on my experience using the camera for short-exposure deep sky imaging, I would say it definitely is. And for planetary use, it is still the bomb. You can get ZWOs with bigger chips these days, but, again, for the planets you don’t need bigger chips. The megapixel range 6mm sensor in this little camera is just right.
Would it still work, though? I hadn’t used the camera in quite a while, and many Windows 10 updates had intervened. Only one way to find out…downloaded the latest driver from ZWO’s website, rounded up a USB “printer” cable, connected it to the laptop and cam, lit off Sharpcap, and she started right up, no problem.
Sharpcap? Yes. While I previously used Firecapture (and before that, the now-forgotten K3CCD Tools), I’ve chosen to move on to Sharpcap for control of my planetary camera. Firecapture is still great, but, for one thing, I am more used to using Sharpcap now, since I fire it up on a regular basis to do polar alignments (its polar alignment tool is flat-out amazing). Also, I might as well get my money’s worth out of the software since I am paying for a subscription to the Pro version Sharpcap. Finally, it is an impressive, professionally executed, frequently updated piece of software.
And so, it was time to put the scope together on one cool if hardly chilly Possum Swamp afternoon. The telescope was, as I’ve done mentioned, Mrs. Peel. To get planetary images that show much detail, you need mucho focal length. Even my girl’s 2000mm would not be enough. I would increase that, however, with a 2x Barlow.
|I began with the ringed wonder.|
There is. The secret is a “flip mirror.” A flip mirror is like a star diagonal, but with a couple of differences. Normally it works just like a diagonal: light enters from the telescope and is diverted 90-degees by a mirror and to the eyepiece. However, a flip mirror includes a knob or lever that allows you to flip the mirror down, out of the light path. Images then go out the back of the diagonal through a camera port. Put an eyepiece in the flip mirror’s eyepiece holder, attach your camera to the camera port, center up the target in the eyepiece, flip the mirror down, and it will be in the field of your camera (flip mirrors are adjustable so you can align the camera and eyepiece views).
A flip mirror makes finding and centering objects at large image scales and with small imaging sensors trivial. Only fly in the ointment? While you can still buy flip mirrors, they are not as plentiful as they once were. They were originally popular with deep sky imagers as well as planetary imagers back in the dark ages. Once DSO astrophotographers went to large chips, they had little further use for flip mirrors, and there was then a reduced demand for them. But you can still find them both new and used. I’m am still chugging along with the 1.25-inch Meade I’ve had for the better part of 20 years.
|Not my fave side of Mars, but there's Olympus Mons!|
Alrighty, then. I did a quick StarSense auto-align (yes, I am too lazy to center a few stars with the hand control these days, folks). Mars was still low and in the trees, so I thought I’d give Saturn a look see. Maybe Jupe, too. I started with the king, old Jupiter. Got him framed nicely, and focused and started exposing. And, in Uncle Rod fashion, I screwed up right out of the gate.
To begin, I forgot one of the first things I learned about planetary imaging way back in the webcam days: aim for the shortest exposure possible; one that yields an onscreen image that looks slightly underexposed. I didn’t. I overexposed Jupiter. However, since I plan to get out at least every couple of nights (giving Mars time to rotate new features into view) I’ll be back to Jupiter soon.
My other foul up? You want plenty of frames, but not too many. Jupiter rotates so rapidly that if you go much over a minute features will actually begin to blur. More importantly, stacking programs like Registax and AutoStakkert will refuse to process videos that are too large. For moi, about 30 – 45 seconds at 20 fps or so is more than good enough. Yes, more frames can yield a less noisy image, but you do reach the point of diminishing returns after about 1000.
|The B.A.A.'s excellent Mars Mapper.|
All you need to do to capture Mars or whatever is set exposure and gain till you get that slightly underexposed look onscreen, open the capture menu, click “start capture,” tell Sharpcap how long or how many frames, and hit the go button. When your sequence completes, the program conveniently places your file in a folder called “Sharpcap Captures” on your desktop. Whether you go for Sharpcap Pro or the basic version, the software is highly recommended by your old Uncle, and if he can get pretty good results with it, you surely can.
When Mars finally got high enough to fool with at about 21:00 local, I went there, touched up focus and ran off a few sequences. Now, what was on display was not my favorite side of Mars. I find the Mare Serenium “streak” slightly blah. However, it’s not entirely without its points of interest. On this steady night, even before I processed the images, I could see Olympus Mons was visible. Of course, Mars’ rapidly shrinking polar ice cap was on stark display.
“Mare Serenium?! Unk, I don’t know pea-turkey about that-there!” If you’ve done everything correctly, including when stacking your video frame with Registax or AutoStakkert, and have judiciously applied Registax’s famous wavelet filters, you will be surprised at how much detail you’ve recorded. You obviously need a map to sort out that detail. Ideally, one tailored for the date and time you took your pictures.
A chart just like that “MarsProfiler,” this can be found on Sky & Telescope’s website. It’s actually a little app. You enter the date and time of your image’s acquisition and it will show just what in tarnation you are looking at. While it’s not quite as detailed, I also really, really like the British Astronomical Association’s “MarsMapper.” In some ways I prefer its Mars disk format to S&T’s flat chart, but I find both of these apps absolutely indispensable.
|The beloved Rat-Bat-Spider from Angry Red Planet.|
Then, get out with the scope and get some shots of the Angry Red Planet. Even if you don’t know a thing about processing planetary images right now, you’ll have some video sequences in the can that you can work on next month—or next year—and your results will just get better as you go along.
Unk? I’ve got to teach my university classes tonight, so I may not get back to the 4th stone from the Sun this evening, but I darned sure will tomorrow night. No, it ain’t as good as 2003, but it sure feels a lot like that, muchachos, it sure feels a lot like that.
One thing you can say for your old Uncle Rod? He ain't no piker. Well, he tries not to be one anyways. Two nights after I snapped the image above, I thought I'd give Mars another try. Two days is enough time to give the planet, which has a day only a bit longer than ours, a chance to rotate into a slightly different position so it will reveal a few new features.
|Edge 800 8-inch SCT, ZWO ASI120MC, 6,000mm|
My results? I had to throw out a few sequences due to dust on the sensor chip. Once I noticed that, I moved the planet to a clear spot (I'll clean the ZWO's chip before doing any more work). The remaining sequences I got were easy enough to process, and the resulting final stills, while they darned sure won't win any prizes, are good enough for me; they make me feel like I've come home to Mars once again.
Which I'll admit is sometimes MY Mars. Not the Mars of NASA's rovers, but an old Mars of beautiful princesses, bizarre creatures, and mile-high skyscrapers adorning strange Martian cities. That's what I dreamed of when I shut down the laptop, stowed the bottle of Yell, and dozed away on the couch, anyhow.
I caught the latest blog[s] and really enjoyed them; your relaxed style writing style is the antithesis to this modern age.
However, I seem to have fallen off the mailing list as I keep missing your monthly output [which ain't good for us cat lovers] so a pointer to regaining regular issues would be good for the soul, if you get me.
O/T Oh and as an, interested party, any chance of a user's guide [or direction to] for Rebel Yell and it's various sub varieties?
thanks for reading, good health and clear skies.
Have you considered doing a shootout between the AR-102 f/6.5 and Amelia, the C102 f/10? I'd really like to hear how these scopes perform side by side.
Just a thought if you are looking for a quick astro project for the blog!