helix

[bokglob]

greetings. this image of the helix nebula ngc7293 was taken at qld astrofest on a night when the air temperature remained at above 23c for the entire capture:mad2:. unfortunatly a combination of an uncooled dslr and to high an iso setting resulted in horrendous noise levels,requiring some experimental processing on my part(newb)with dss and ps. it's been a personal goal of mine to image this target for ages so i'll stick with it untill i get another chance. hope i have'nt ruined it!:D liveandlearn!! 15x7min at iso800 ed80, heq5 pro, canon500d, phd guiding

[jjjnettie]

That's very nice indeed Darrell.
I envy your ability to take these long exposures. Maybe one day I'll get there.

[AlexN]

Better than my attempts at the helix thus far... I have 24x10min subs of it on this PC that I took last new moon, however the light pollution has washed it out horrendously and its being a REAL pain to process...

You've done well..

did you take darks? if not, take a few over the next few nights while the temperature is similar to that of the night of capture.... More you can get the better if the images are very noisy..

Best of luck!

[h0ughy]

well its a great shot considering the temperature. Thats why a cooled DLSR was very high on my agenda and i had my 350D modded and cooled.

[gregbradley]

You salvaged quite a nice shot there.

You can always take darks at home at that higher temp or close to it and subtract darks from your Astrofest image to help clean it up.

Greg.

[gregbradley]

C'mon Houghy time to step up and get yourself a CCD eh?

Greg.

[AlexN]

I believe Houghy has a QHY8 these days also.. ?

[bokglob]

thanks guys, the advice on darks is appreciated.i must explore a "dark library", as i have read some stuff on it recently(sounds simple enough) is this a good idea?

[Hagar]

Pretty good result considering the temprature and an uncooled camera.
Well done.

[Octane]

Darrell,

Commendable effort. :)

Other people might tell you otherwise, but, I keep saying that a dark library for a DSLR is pretty much next to useless. You really need to have the same temperature/humidity/everything (or, very close to it) as your light frames.

Dark libraries would work fine for good quality CCDs as they're designed for this purpose. A DSLR is a commercial/consumer device, which is going to respond in different ways to varying temperature/humidity situations. You will find that hot pixels and noise will vary from time to time. Unless all that is removed from your light frames, you're going to end up with artifacts sprinkled throughout your final stacked image.

Having said that, you can quite easily clone out hot pixels and random noise in post-processing.

Anyway, just some advice that has served me well. :)

Regards,
Humayun

[prokyon]

Hi Darrell,

nice pic. This is one of my favorite objects. The only thing you could change is to reduce the green a little.

werner

[CoolhandJo]

What noise?? Nice detail. Well done.

[multiweb]

Very nice Darell . Another great shot. You're on a roll. :thumbsup:

[spearo]

looks good, like the colors!
well done
frank

[dpastern]

Looks good to my untrained eyes. Good detail as well. I didn't notice too much noise, but then, I didn't go looking for it either.

Dave