Sunday, January 04, 2015

 

Destination Moon Night Nine: Sometimes You Squeak By…


With stormy weather predicted to be on its way, I thought I’d better get out and take more lunar images while I could, muchachos. Unfortunately, while not forecasting dire conditions for the evening in question, the weather goobers agreed there’d be “some clouds.” Worse, Seeing on the Clear Sky Clock was transitioning from dark blue squares to light blue ones. I thought it was still worth a shot, though. The weather gurus are saying we’ll have a cool and wet winter, so there’s no telling how many more chances I’ll get at Miss Hecate before spring.

Last time out, I’d gotten a little rushed and had to finish set up in the dark. Darkness is now coming on in a hurry, and it had snuck up on me. That wasn't my only mistake.  I'd decided not to install the DewBuster dew-heater system on the C8’s corrector that night.  Naturally, it became obvious not long after sundown that it was going to be a dew-heavy evening, so I had to waste more time getting the heater installed.

I'd also forgot to hunt up my JMI motofocus motor, and had to scramble to get it on the scope, too. Overall, Night 8 had a flying-by-the-seat of my pants feel. That’s understandable, I reckon, since Destination Moon had taken a few months off, but I didn’t like that feeling and resolved to do better on Night 9.

Ha! This is Unk we are talking about. I did at least start set up an hour before sunset and get my 1995 C8, Celeste, on the VX mount and heater strip on her corrector before dark. I was feeling right proud of myself was standing there fat, dumb, and happy in the gloaming, staring up at beautiful Luna. Till I realized I’d forgotten to rustle up the dadgum Motofocus again.

I retrieved the widget from the house and installed it on the C8, snapping the motor over the SCT’s focus control. What’s a Motofocus, anyhow, and why do I use one? A recipe for out of focus Solar System images? Twitch the focuser and walk back to the computer to observe your results. Not only will focusing cause some shake on even firmly mounted scopes, shaking that may continue for some time at f/20 or f/30, you may forget which way you turned the focus knob the last time when you go back to the scope to tweak some more. It’s a pain, and you apt to settle for less than perfect. Sitting and watching the image on the computer and focusing with a wired remote control is mucho bettero.

There are two ways to do that. One is with a Crayford focuser on the rear cell. These are similar to the focusers on (some) Newtonians and refractors, and focus by moving the camera back and forth instead of the SCT’s mirror, which is what the normal focus control does. That’s good in that it eliminates focus shift. The SCT’s moving mirror system causes the target to move back and forth in the field because of slightly loose tolerances between mirror and baffle tube. That is not a problem at f/5 or f/10, but at f/20 or f/30, which most of us use for Solar System work, it may move the crater of interest right out of the camera’s view.

A Crayford focuser equipped with a motor is probably the best remote focus solution if you use a refractor or Newtonian or if you are an SCT owner who only want to use the focuser for planetary/lunar work. Unfortunately, one causes problems for deep sky imaging with a CAT. The extra back focus required by a Crayford may make it impossible to bring your camera to focus, at least if you have a reducer in the imaging train, as you probably will with an SCT. Motorized Crayfords also tend to be more expensive than your parsimonious old Unk likes. Enter the JMI Motofocus.

“Whats they-at Unk?” Well, I’ll tell you, Skeezix; it is a lot like JMI’s old Motodec. That blank look on your kisser tells me you weren’t around in the days of non-goto fork mount SCTs that required add on motors for declination guiding. To make that long story short, then, the Motofocus is a motor that snaps over the SCT’s normal focus control (or, actually, a replacement focus knob and collar JMI includes with the Motofocus). There’s also a cable and a two-button remote. Push the buttons to focus one way or the other (holding one down for several seconds conveniently speeds up the motor) as you can sit at the PC.

Yes, there will be image shift, but even on my 1995 Ultima 8 OTA it is bearable. And it is just so cool (and effective) to be up on the deck with the PC and watching the screen to focus. I did have to spring for two extension cables for the Motofocus’ uber-short cord to allow me to do that, but even figuring in the extra cost of those from JMI, the price was still lower than for a motorized Crayford. If you are less lazy than Unk, you can even fabricate your own extension cords, and not have to pay the extra fare.

With the Toshiba laptop up and running, camera plugged into the USB, and computer plugged into the VX mount’s serial port, I turned a critical eye to the sky. Didn’t like what I was seeing, y’all. In late afternoon, it had been clear as a bell. An hour after sunset, there were bands of thin cloud approaching from the west, and the humidity had spiked way up. The DewBuster would deal with the resulting dewfall, but there wasn't nothing it could do about fog, and it felt like that was a distinct possibility.

Oh, well, wasn't anything on the gull-dern boob-tube anyhow; might as well give it a try. I fired up the VX and essayed a 2+4 goto alignment, an AllStar polar alignment, and, finally, a second goto alignment, since I’d had to move the mount a fur piece in altitude and azimuth during polar alignment. I wanted to use my fave Moon software, Virtual Moon Atlas, to goto craters and other features, so I needed not only the mount's tracking, but also its goto to be spot on.

When all of that was done, I took another look at Diana. Those dratted clouds had moved from west to east and would soon be covering the gibbous Moon, who was hanging high in the east and, for the moment, shining brilliantly as she approached 11 days of age. Time was a-wasting. Unk got on the stick, focusing up on Copernicus on FireCapture’s display. To the extent I could focus. The image was swimming like crazy as the outliers of the clouds began to impinge on Luna. I synced on the crater in VMA so my gotos would be good, but wondered if I was wasting my time given the lousy images on the PC.

I was tempted to just call the whole thing off, but sometimes the images you see in real time onscreen can be deceiving. Sometimes finished, processed images on nights like these can be—if not perfect—surprisingly acceptable. I was feeling like I should stop dawdling with Destination Moon and get ‘er done, so Unk kept on keeping on.

While I gave y’all the rundown on my equipment setup last time, I didn’t say nothing about camera settings in FireCapture for the ZWO, and some of y’all have asked about that. I keep it simple. Gain is at around 60, which gives plenty of brightness, but keeps noise down. Exposure? I aim at holding the histogram to 60%, and adjust the exposure with that in mind. What I was taught back in the early webcam days still maintains:  aim for an image slightly dimmer than what you think looks best. That will keep your frame-rate up and the chances of overexposing highlights down.

How long do I expose for? I generally find 1000 frames, which I can get in a little over 30 seconds at the camera’s highest resolution, will produce enough good frames for a decent picture under reasonable seeing. It will also yield reasonably small .avi files. Keep in mind, though, that I am on the Gulf of Mexico coast where seeing is often flat-out excellent. If you live in a place where the air is less steady, you will need more frames for a sharp finished image.

That our seeing is often top-notch is an advantage to living down in the Swamp. Disadvantage? Despite having a few nights thus far this fall where the temperature dropped below 32F (unusual for autumn here), the dadgum skeeters are still around. All it took to bring ‘em back was nighttime temps in the 60s and high humidity. They were biting the hell out of me right after sunset. I trotted back inside, got a lighter, and fired up a citronella candle, which kept the biting devils at bay (mostly).

It was then, I thought, time to get going. That’s what your silly old Uncle gets for thinking.  The thin clouds that had formerly only been impinging on the Moon were now covering her shining face. All I could do was cool my heels, occasionally re-centering Copernicus on the monitor with ASCOM’s little onscreen hand control, and fuming.

After half an hour, the nasty clouds drifted off, and it looked like I would have a OK if not overly-steady hour or three. What did I do in that time? I journeyed up and down the terminator, snagging features that didn't show as “Imaged” in the Notes field in Virtual Moon Atlas’ info window.

Gassendi

I thought I surely must have already imaged this magnificent formation, but Virtual Moon said “no.” Hokay. Click on this big crater on the chart, mash the “goto selected” button in VMA, and away we went. While the VX’s goto is amazingly good, at f/20 with a 1/3rd inch camera I generally have to do a little centering, but that was OK. If the features were off screen after gotos, they were just off screen and always in the same place and it was easy to line things up with the ASCOM HC direction buttons.

Lying on the shores of Mare Humorum, this big (111 Km.) crater is dang sure something to see. It's flat-floored with a double-peaked, rounded central mountain and high, terraced walls. Those are not the things that draw your attention, however. What does that is the large craterlet, Gassendi A, which has intruded on the main crater’s northern rim. It is big, 33Km in diameter, and is what in part gives Gassendi its distinctive look.

What makes Gassendi even more recognizable is the series of rilles running every which-way across its floor, Rimae Gassendi. There are a couple of nice small craterlets too. While this youngish crater—it dates from the Copernican Age (1.1 billion years ago to the present day)—is almost perfectly round, it looks somewhat oval due to its position out toward the Moon’s limb. I’ve been admiring Gassendi since I was a sprout and never have gotten enough of its stark beauty.

Clavius

OH. MY. GOD. Freaking Clavius base! Even before 2001: A Space Odyssey came out in ’68 I knew all about this crater, one of the most interesting and beautiful on the entire Moon. I double checked with VMA, but, surprisingly, like Gassendi I hadn't visited this one yet for Destination Moon. Not that this was the best night to image Clavius. When the clouds had first cleared off, the seeing had improved some, but now it was getting worse again. Nevertheless, I shot a couple of sequences, hoping for the best.

This enormous 225 Km. walled plain would be impressive on its own, but what makes it a real standout is the detail, mainly the many craters large and small that cover this old (Nectarian, 3.92 billion to 3.85 billion years ago) feature. And, particularly, the arc of five craters beginning with Rutherfurd, which has disrupted one of Clavius walls, and continuing with, D, C, N, and J on its floor. What makes this especially photogenic is that the craters are lined up in order of size, going from 55Km. (Rutherfurd) to 12Km. (Clavius J). There is no better lunar attraction for telescopes of any size than Clavius.

Le Verrier and Helicon

These two smaller craters (20 and 25 kilometers, respectively) are set all by themselves in Mare Imbrium about 235 kilometers from the center of Sinus Iridium. Nearly alone in the relatively bare area, both craters look young and sharp, but they are not really that fresh. Le Verrier dates from the  Eratosthenian (3.2 billion to1.1 billion years), and Helicon from the Imbrian (3.85 billion years to 3.2 billion years). Of the two, Helicon is the most interesting. There’s a system of ridges on the floor that form a distinct “U” shape around the low central peak.

Fontenelle

On the shores of Mare Frigoris, Fontenelle is an interesting looking crater with a size of 38 Km., making it easy for the smallest scopes. It possesses a flat lava-filled floor, a small and rounded central peak, and several rilles, which are barely visible in my image. While it dates from the Lower Imbrian Age, 3.85 billion to 3.8 billion years, this feature is fresh appearing and stands out well.

Philolaus

This one lies 311 Km. southeast of Fontenelle and is a younger and larger formation. It is 71Km. in diameter and dates from more recent Copernican age. In addition to high, terraced walls, Philolaus features a double central peak and a rough-looking floor. It is almost centered on a larger and nearly erased crater.

Birmingham

Talk about “nearly erased.” Birmingham, a large, 93 Km. crater—or what’s left of it--is old, dating from the Pre-Nectarian 4.55 billion to 3.92 billion years ago, and looks it. All that is left is portions of what must once have been impressive walls and a flat craterlet-wrecked floor. The most noticeable feature is two adjacent craterlets, G and H. As a youngun, I felt proud my state’s largest city was represented on the Moon, and was dismayed to learn Birmingham was actually named in honor of a 19th Century Irish astronomer.

Lansberg

The seeing, which had been tending to “worse,” suddenly got much worse, and Unk sat stewing for about fifteen minutes, trying to decide whether to pull that accursed Big Switch or not. Then, the the air began to steady down again, reverting to the merely “stinky” from “putrid.” On to Lansberg (a.k.a. “Landsberg), then.

With neighboring Reinhold, this is a pretty pair of craters. Lansberg itself is impressive, with a fresh look that betrays its considerable age; it dates from the Upper Imbrian 3.8 billion to 3.2 billion years back. At 40 Km. and with a position just far enough from mighty Copernicus so it catches your attention, Lansberg is awesome. It has high terraced walls and a flat floor dominated by a high central peak. There are also craterlets, but they are tiny.

Hortensius

Moving to the north from Lansberg, we run across Hortensius, a medium-small 15 Km. crater washed over by one of Copernicus’ rays. On this night, much of this young (Copernican) crater was in shadow, but there’s not much to see beyond its sharp, perfect looking form anytime. There are steep slopes and a small, flat floor and that is purty much it.

Vitello

My luck and the seeing holding in at least temporarily, I was off to the south and the sands of Mare Humorum for a quartet of craters. Vitello is a nicely detailed 41 Km. feature with high walls and a lumpy floor. In addition to those lumpy hills, there are craterlets, a smallish central peak, and a rille system that is just barely visible in my image.

Doppelmayer

Despite having seen better days, Doppelmayer is still noticeable and impressive. It is 65 Km. in diameter and was formed in the Nectarian days. There’s a jumbled and rounded looking central peak and a series of hills in semicircular lines. “Semicircular” because the side of Doppelmayer facing Mare Humorum has been flooded by Mare lava and has been almost totally obliterated.

Lee

Stationed between Vitello and Doppelmayer, Lee is in even worse shape than the Doppelmayer. What is left of this 41 Km. Nectarian feature is a little more than 180-degrees of contiguous walls.  There are some hills and rough ground along the surviving walls opposite Humorum, but that is all.

Ramsden

Everybody in my generation of amateur astronomers knows the name “Ramsden,” as in Jesse Ramsden, the 18th Century astronomer who invented the simple Ramsden eyepiece, which was all the poorer among us, like li’l Unk, could afford back in the Day. This is his crater.

Ramsden is an oddly shaped 25 Km formation with a slightly oblong appearance. Otherwise? Besides the two craterlets, one that’s intruded into one of the walls, and one nearby, the most interesting thing here is the rille the crater’s formation disrupted, Rimae Ramsden, a double line of rilles with the crater smack in the middle of their length.

Pitatus

Shortly after I finished with Ramsden, the seeing, never good, began to get dramatically worse again. However, Unk was on a roll, and rolled on anyway. A little unwisely as you can see from the result. Anyhow, Pitatus on a good night is an astounding formation—a big crater with a flat, dark floor and a shape much like that of Plato. There’s a rounded central peak and numerous craterlets, but all I picked up was a bland floor with a couple of brigher spots and a blur of a central peak. This is one I would like to revisit. Pitatus is 98 Km. across and was formed in the Nectarian Age, 3.92 billions to 3.85 billion years ago.

Gauricus

Is an old crater, from the Pre Nectarian time and the major impression I have of it is “rounded and soft.” Especially on this night when the seeing was making everything look soft. This 80 Km. feature is just barely with us; it’s walls have been eroded away and slammed by many impacts. The most obvious feature of the flat floor is a ghost crater, or a pair of connected ghost craters, Gauricus F.

And that, as they say, was that. The seeing went south even moreso, and your old Uncle was ready to shut down and warm up from the chilly mid 60 temps. As is my usual practice, I didn’t even look at the .avi files much less process them once I was back inside; pictures always look better, or at least less depressing, in the morning. No, it was the dadburned Yell and an episode of Arrow I’d missed on On-demand.

The next day as I was converting the raw files to normal .avis (“Debayering” them), I was heartened that they didn’t look nearly as bad as I expected. Oh, they were not masterpieces, but all except the shot of Pitatus and Gauricus had some detail to give up, which they did after a run through Registax’s wavelet filters.

One more good thing? After I finished stacking and sharpening the evening’s haul, I did a little playing around with that new stacking program, Autostakkert, which I mentioned to y’all that I had not been able to get working right. As I expected, it turned out to be pilot error (so what else is new?). I am all het up give it a go when Night 10 of Destination Moon comes ‘round, muchachos. For now, though, Luna is gone and it is time to hit the deep sky again.

Total Thus Far:  100 Down, 200 to Go…

Next Time: Deforking Bertha...

Comments:
I believe your in-picture label(Cassini) should be Gassendi. The name of the jpg file does say Gassendi.
Don Horne
 
Thanks for catching that!
 
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