From: Milton Aupperle <milton@outcastsoft.com>

Date: December 2, 2009 2:34:02 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Mars this morning ...

Hi Jim;

Nice mars shot.

I use the 2x or 3x stacking alignment for doing sub pixel alignment on my LRGB DSO shots too. Sometimes it's really tough to get the individual LRGB channels to line up precisely at 1x size, especially with turbulence. Thats' how I did the Blue SnowBall image:

http://groups.yahoo.com/group/Astro_IIDC/files/DSO/NGC7662_BlueSnowBall_MJA.jpg

Winter finally arrived here to stay last weekend (freezing rain, then sleet, then snow on top of that with 600+ traffics accidents, RCM shutting down all highway traffic north to Edmonton and 5+ hour commutes to travel 20 kms) and the temperature dropped to -14°C last night. I was out testing my LRGB balance exposures with M34 for 3 hours and some new cold weather procedures. I'm using heating pads to keep the mount gearing from getting too cold so that it binds and keeping the laptop not freezing up. Last winter, at -35°C the hard drive would freeze solid and the Mac would spontaneously re-boot. This is especially bad under Leopard as one can't use the Processor utility to turn off the "sleep cpu" option on the G4  Macs, which drives the CPU flat out and generates a lot of much needed heat.

Right before I packed it in, I took a quick series of images of the moon using the C8 at 1150 mm focal length, with the Hutech IDAS LPR filter, a Red Astrodon filter with the Grasshopper 16 bit 1384x1036 camera. I had to use 2.3 ms exposures at 15 fps  to keep it dark enough so it didn't over saturate. Seeing was really poor with +/- 10 arc second jumps between frames at 2 ms exposures, which would be like Jim's Mars jumping a full disk width between frames. I had to shoot 4 movies as the moon was too big to fit in a single frame, then stack and aligned them using MAP procesisng (about 15 to 20 64x64 MAP points per movie) and then processed stacks in Astro IIDC. I really over pushed the contrast to bring out the dark mares and the rays from young impacts too:

http://groups.yahoo.com/group/Astro_IIDC/files/Lunar/Lunar_20091201.jpg 

Unfortunately I did not use the saturate check box to check my exposure range and I would up under exposing the frames pretty badly. This dropped contrast and made the moon disk look pretty bland. It also made it difficult to find good contrasty areas for area selection on the disk away from the limb. Since I had no appreciable drift of the moon on the CCD (good polar alignment) for the 650 frames i collected in each movie, I used the "Histogram expand brightness of all frames used for pixel alignment." option when stacking. This boosted the contrast remarkably and gave me good high contrast selection areas to use for MAP alignment. Without it, a feature like Plato's dark floor surrounded by the bright mountains would have a Pixel Variance of 4 to 5 and with this option it would be 20+ pixel variance for a 64 x 64 area. This really helped alignment.

TTYL..

Milton Aupperle

On 2-Dec-09, at 1:22 PM, jimchung2338 wrote:

Thanks Mark & Alan!

I did a better reprocess and there's more detail to be mined as can be seen in the 200% upsize.  

http://tech.groups.yahoo.com/group/Astro_IIDC/files/Planetary/Marsreprocessed.jpg

Jim