The Starry Night, 66

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10/5/2011. Another cool, clear night with good seeing. I saw PSF's in the 1.4 arc second range and tonight's finished stack came in with a resolution of around 2.3 arc seconds despite some declination departures of mysterious origin (cable drag is my prime suspect).

I wanted to take a close look at another section of the Veil Nebula, continuing my ad hoc series on the fountains of creation, a look at a 5 - 10,000 year old supernova remnant in Cygnus. Debris from a massive star is enriching the interstellar medium by the same mechanism and with the same kind of newly-minted elements that once upon a time became the Sun, the Earth, and thee and me:



NGC 6960 passing behind the star 52 Cygni
10x900s L, 1x900s RGB
SBIG ST2000XM w/Baader LRGB filters
AstroTech 10" Ritchey-Chretien
Astro-Physics Mach1GTO


2.5 hours is a good start. Smoothing it out and bringing in those delicate shock fronts and cirrus-like ribbons without such aggressive histogram stretching will take a lot more. From earlier efforts with the 5-inch refractor, I'd guess that 10 hours will suffice but even more would be good.

It's also worth noting that Steve Jobs died earlier today. Look, I'm a PC-guy; have been since the beginning of the PC, the Apple II, the Atari, the Tandy, etc. Can you imagine that Photoshop or anything like it in its present form would exist had Apple and Jobs not welcomed the community of artists into the community of computer users? It makes the blood run cold to imagine what image editing software would be like if it had been spec'd out by the stereotypical PC engineer/geek or written entirely by the stereotypical artistic loft-dweller. Instead, we had Jobs and we got a platform and a market for Photoshop, and here you have tonight's photograph of the recapitulation of the creation of the Sun and the Earth and all that is in it. No way this image (or so many others) could have come to pass without him.


10/6/2011. And another clear night. Amy and I are off to the Smokies tomorrow and I won't be under the stars again until at least the 10th (when a cloudy spell is forecast), so I am making the most of tonight. I started capturing luminance data to add to the image above as soon as the field cleared the canopy of Bird Feeder Tree. That was only a few minutes after astronomical twilight, so no time was lost to the arboreal world. I got a PSF of about 1.4 arc seconds while focusing; individual 900s subexposures are coming in at 1.9 to 2.3 arc seconds depending on tracking. The composite image seems to be good to 2.2 or so, so sharpness is not an issue. After shooting the Veil, I slewed to V1 to try to get another data point from it.

I don't want to keep trying your patience and burning your bandwidth with consecutively better versions of the NGC 6960 field, so I'll keep the initial attempt up top for reference and update the image below and its caption to reflect the current state of the effort:



NGC 6960 passing behind the star 52 Cygni
26x900s L, 1x900s RGB
SBIG ST2000XM w/Baader LRGB filters
AstroTech 10" Ritchey-Chretien
Astro-Physics Mach1GTO


Going from 10-26 subexposures didn't make as much difference as I thought it would, at least in this web-sized reproduction. In the full-res file, the gradations within the Veil and the background are much smoother and more pleasing, but on the intertubz, I don't see a lot of improvement. I do see more and fainter arcs and wisps to the right of the brightest portions of the nebula, and I see similar detail despite less aggressive saturation boosting and histogram stretching, but overall, not the difference I expected. I'll pile up more light and see what happens.


10/13/2011. Roland's been posting some good tips on guiding in the Astro-Physics users' group; among them that longer calibration runs may be in order to get proper declination tracking. Says that ten seconds is the minimum to use, that six is definitely too short. So check the PHD Guiding parms next time out. And I've ordered the upgraded azimuth adjuster for the Mach1. Figured that I've paid a lot for this mount and it makes no sense not to be able to adjust it properly. The same rationale says I should, absolutely, positively learn to use all the polar alignment tricks and tools at my disposal.

The post-vacation cloudy spell should come to an end tomorrow, so it's back to V1 and NGC 6960 with me. Look for updates above and on subsequent pages.


10/14/2011. Couldn't get a sharp focus tonight; lousy seeing apparently. I collected 4 hours of RGB of NGC 6960 for the next mix.

Tales of woe begin here. Just skip to the next page unless you're a glutton for this sort of thing. I'm leaving them here so I can keep up with fixes made and fixes still to go.


10/15/2011. I put the weather cover over the solar scope to keep it off the ground; the cover acted like a sail, and an unexpected gust of wind tipped the scope over to the north, down the slope of the lawn. Now the 'scope refuses to focus through the external filter, and the eyeball view through the blocking filter and double stacked etalons shows half a dozen narrow red streaks (thin triangles running side to side, like a seriously out of kilter interferogram) rather than neat red Sun balls. Lunt has been great about quick replies, an RMA, and a reassuring estimates of the cost to repair the external etalon (the impact evidently "decontacted" it). The filter heads back to Tucson on Monday.

Tonight, I can't get the R-C to focus worth a damn. More bad seeing? Like yesterday night. Poor seeing was in the SkyClock forecast for both nights, but somehow that doesn't quite explain what the detectors are showing. The stars are not lively, they just won't come to a decent focus on the chip. Then the OAG somehow stopped feeding light to the guide camera. I shot NGC 6960 while guiding witih the top-monted ST80 and made 300s subs rather than 900s subs, but the results were not good. Some trailing, 3.5-4 second stars 20% out of round, or worse. Around midnight, I brought assorted parts inside, took some of the adapter bits donwstairs and drilled out a recalictrant set screw. Put it all back together. Very solid, sharp guide stars, back to V1 in M31. The OAG works again, though the axial (rotational?) adjustment is jammed up by the threaded parts somehow. Nevertheless, guiding looks pretty good, but I'm still not getting sharp images. Also, the first 900s -30C images show frost. Probably a souvenier of bringing it inside from a cool night with the chip still passing cold. I wonder if there was a nascent moisture / frost problem last night and earlier this evening to account for some of the difficulty getting tight PSF's? I'll let it run overnight and hope for the best, and I'll change the dessicant tomorrow and let things dry out before dark.

Overnight, I got 4 good frames and 12 very bad ones. Guiding went to hell. Most results look like very bad manual guiding or even like no guiding at all. I have no explanation unless something got very loose, shifted, rotated, screwed the guiding calibration, etc. The opaque frost crystals dissipated early in the run but stretched images show degradation across the image (images liik a little like they are being viewed through a sheet of shower-stall glass). There's clearly too much moisture in the CCD chamber. In the morning, I took the OAG connections apart, made a shim to help hold the USB connection in the DSI, used the lathe to turn down the part of the OAG connector that was binding the axial adjustment, fussed with tightness of the tilt prism adjustment, cinched it all back together, changed the dessicant in the main imaging camera, and set it all out on the telescope to bake in the Sun till nightfall. I've ordered a couple of USB extenders from China so that I can leave the DSI's USB plug firmly attached and disconnect the camera a few centimeters downstream. That will make it practical to bring the cameras inside during inclement weather without wear on the already-loose DSI connection.

In addition to the salutary steps in the previous paragraph, I engaged in some useless, possibly counterproductive maintenance. I used the A-P cleaning kit to loosen and remove dead bugs from the R-C's primary mirror. Also dust. The dust got redistributed as streaks etc, which has probably done me no favors. But at least all the bug-juice is gone. Someday when I am feeling bold and the grunge is actually problematic, I'll pull the rear cell, clean the optics properly, and probably spend a month getting things recollimated. It's an adventure I'll undertake after I get one of those collimatable focuser adapters -- in for a penny, in for 150 Euros or thereabouts. Or: why not just remove the 4 bolts that attach the secondary vanes to the OTA, get it out of the way, and clean as desired? I don't see how the secondary could be misplaced, as long as the same vanes go back into the same slots afterward.


10/16: The Particle Wave dessicant pack worked fine, the OAG is working well, seeing is still bad, and clouds moved in after about 2 hours of the Veil. We'll see if tonight's data contributes much of anything to this image after I get another good night or two.

10/23: Oh enough for this page. Look at the next one.



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                   © 2011, David Cortner