The Starry Night, 83

:: home ::




              <<   41   42   43   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60c   60   61   62
              63   64   65   66   67   68   69   70   71   72   73   74   75   76   77   78   79   80   81   82   83   84   85   >>   SRCH


1/24/2012. I added a 14mm Hyperion extension ring between the CCD and the CCD67T telecompressor. The Ritchey's EFL was reduced to 1299mm (F5.1, 1.16"/pixel) and there are still ~5600 RoboFocus units (2.2 cm) of in-focus available. I also remeshed the Dec drive gear according to A-P's instructions. (Now do the RA for consistency's sake.) The CCDInspector report is not as excellent as before, but that may owe more to my stuffing more Teflon rails into the focuser than to anything else. I may need to tweak the Teleskop-Services collimating ring. I've changed too many variables at once to be sure precisely what is slightly off, but everything seems to remain within the limits of adjustability. As for the quest for wider, faster fields: more, more, more. Stick around.

All tonight's images are with the AT10RC @ F5.1, all guided and acquired with Maxim DL using the
ST2000XM in dual-chip mode. Tip of the night: when using the onboard guide chip in Maxim DL, autostretch the histogram of the guider! (Dope slap.) That instantly improved tracking on M81 to a huge degree (by a factor of 3-4x or more).

To begin, here's NGC 404, the Not Found Galaxy, tucked up against Mirach, plucked out of late twilight:



NGC 404 (upper left) and the star Mirach
6x300s L, 1x300s RGB


And then, of course, I shot M33 with this even wider field of view, for comparison and fun:

m33 f5.1

2x900s L, 1x900s RGB


m33 comp

This is how far we've come in widening the AT10RC field.
The rectangle marks the approximate field of
view at its native F8.


IC 443 gets some time tonight in the spirit of comparing configurations. That's a lot of density in a fairly short exposure. The background is noisy, as are all tonight's, probably owing to my enthusiastic stretching of thin data:



IC 443
H-a, 8x900s


I finished the night by slewing north to M81 and letting the telescope work until dawn. Most exposures were lost to clouds, but the guiding held and I got a few frames early and late:



9x900s L
[wait for the 1/27 image...]


That turned up a lot of bright supergiants (or knots of bright supergiants) in the arms, but not really as much detail as I had hoped to catch. This part of the sky is plagued by my worst gradients, and controlling those didn't help. I didn't rotate the field in order not to need fresh flats. On a more transparent night when I can begin this sequence earlier and devote all the night's efforts to optimizing it, I'll expect much better. [Oh, just you wait! 5 hours on 1/27 was a proper beginning. Stars and stria everywhere.]


1/25/2012: Deneb to Jupiter to M33 in bright twilight where I used both "preview" and "frame and focus" modes to watch the galaxy come up from the darkening sky. I calibrated the guider as soon as the sky would allow and then ran a 300s LRGB sequence just for drill. Yes, the autostretch detail for guiding is a robust tip. I did a couple of 900s L frames while the guiding was good, one of them is very sharp. At webrez, it's indistinguishable from the one above, so I'll spare your bandwidth. The second 900s frame features small departures owing to interuptions by incoming clouds. It would be OK in a long series of stacked images, but was useless as one of a pair or by itself. I remeshed the RA gear earlier today. And I brought the camera in late after a look at 2-3 days of rain and high humidity in the forecast.


1/27/2012. When using the onboard guide chip, binning the guiding CCD 2x2 avoids a lot of unnecessary jiggle. Probably cuts down on chasing seeing. Two D'oh! moments in one week. That's good.

Friday night was unexpectedly clear. In fact, it was very clear. I hit the usual targets, but with much better tracking. Binning the guide chip, auto-stretching the guide image, and some very casual refinement of polar alignment produced guide errors on the order of 0.5 arc seconds RMS in both RA and Dec instead of the 1 to almost 2 I was seeing before. The difference is spectacular. Five hours on M81 with such guiding brings stars up throughout the arms and neatly resolves the faint, irregular companion galaxy. Saturday night should be as good. I'll hold off on show and tell until I get a couple of deadlines behind me and have more data to play with. Probably tomorrow.


Except where noted, deep-sky photos are made with an SBIG ST2000XM CCD behind a 10-inch Astro-Tech Ritchey-Chretien carried on an Astro-Physics Mach1GTO. The CCD is equipped with Baader LRGB and 7nm H-a filters. A Meade DSI Pro monochrome camera looking through a modified Orion off-axis guider keeps the OTA pointed in the right direction. The imaging camera is controlled via Nebulosity 2; the guide camera is operated by PHD Guide 1.13, both by Stark Labs. The stock focuser on the AT10RC has been augmented with Robofocus 3.0.9 using adapters turned on the lathe downstairs. Maxim DL5.12 performs image calibration, alignment, and stacking; Photoshop CS4 and FocusMagic 3.0.2 take it from there. Gradient Xterminator by Russell Croman and Astronomy Tools by Noel Carboni see their share of work, too.


:: top ::



                   © 2011, David Cortner