Three Recent Images

[Jim McMillan]

Three recent images:

Hubble's Nebula - about 10 hours total exposure over 3 nights
The Whale Galaxy - about 8 hours total exposure over 3 nights
NGC 2903 - almost 11 hours total exposure over 2 nights

We had a pretty decent run of weather over the last couple of weeks allowing much more imaging than what is normal for March. ACP is performing virtually perfectly for me.

I hope you like them.

Jim

[Dick Berg]

Jim,

Great images! I hope you will collect the color information for the Whale and 2903. Are these all ten or fifteen minute subs or are you shooting longer ones?

[Jim McMillan]

Thanks, Dick. I shoot 10 min subs 95% of the time - as I did for all these images. Some time back, Stan Moore published a formula to help determine the "optimum" exposure time to minimize the effects of read noise. The idea is to make the read noise inconsequential versus all the other forms of noise (I think called "shot" noise). For my camera, the forumula determined I want to have a background ADU level of no less than 800 or so. For 10 min exposures, for luminance and no moon, my background ADU level is 2750 or so (it approaches 10,000 with a full moon); R is about 800, G is about 1000 and B is about 750. I guess I could go a bit longer with the RGB, but then you start trading off lost images to satellites, dealing with longer darks, etc. so I've landed at 10 min. The only time I deviate is if I want to go shorter because of excessive blooming. For instance, I'll only go 3 min when imaging M13 in luminance because blooming will destroy the results.

I'm hoping to add color...it depends on the weather this week. Otherwise, the moon will start to cause problems with the color data. I don't really get too concerned with the moon if just taking B&W...but it really makes things much more difficult to process if taking color.

Jim

[Bob Denny]

I'm with Dick, very nice! The 2903 shows so much faint detail waaaayyyy out. Amazing!!

[Jim McMillan]

Added color to NGC 2903 from the last 2 night's runs. This was a fast processing job; I might go back and try to do it a bit better when I have time.

Jim

[Dick Berg]

Jim, This is absolutely spectacular! But I know you will make it even more beautiful. The definition is really very good, especially that it shows up the three faint galaxies in the lower half of the image.

The little galaxy on the lower left is UGC 5086, a "low surface brightness galaxy". (See: http://simbad.u-strasbg.fr/simbad/si...=UGC%20%205086 if you're interested.) And another one at the 4:30 position - something called a "passive red spiral" (See: http://simbad.u-strasbg.fr/simbad/si...122238#lab_bib)