A nice half-hour between clouds

[george7378]

With almost a week of horrid cloud, it was a godsend to see stars in tonight's sky. I quickly pulled the scope outside, and went outside with my dad.

After a bit of dark-adaptation, we centered on the Ring Nebula (I had trouble picking out Lyra in the starry sky!) and it revealed a bright circle with a ring in averted vision. I then showed him M13, and we looked at the amazingly bright core among the stars - the best I've seen it yet! Then, it was on to M31 for the first time in ages - we both saw it with the naked eye and it was an impressive scope sight, with a satellite galaxy showing too. Then it was Milky Way all round, with an amazing spill of light through Cygnus.

Anyway, I posted this in the imaging thread because I took some test exposures with my new camera. Here they are:

Star trails of Lyra and surrounding constellations (60 seconds):

Cassiopeia (60 seconds)(do you think I got M31 in this picture or not?):

Any help and feedback is appreciated - especially on how to get the most out of these photos (How would I go about stacking and what would this achieve?).

EDIT: Here's another 60-second exposure showing Jupiter and some other stars:

Thanks, George.

[george7378]

Does anyone have any advice or tutorials on processing and stacking images like this?

Thanks.

[george7378]

I have tried stacking in GIMP and got this by stacking 9 30-second exposures (I just copied the same image 9 times and stacked it using addition:

[george7378]

I also got a nicer Cassiopeia shot by stacking (starry!)

Any advice on how to get rid of that noise at the bottom would be appreciated.

[EA2007]

Hmm,

Maybe go for shorter exposure times as you have star trails from 60 seconds. I would aim for 25 second exposures, possibly 30 seconds if you have your camera with the lowest zoom level.

If you can adjust the ISO level, perhaps increase it to 800 or 1000 and if you can adjust the f. ratio to a lower level like 3 or 4 that would be better. Though I don't know how much you can overide your camera settings.

What size chip does the camera have? Your images look quite blocky, indicating either a smaller chip size or the jpeg setting is lower (i.e. at a lower resolution).

If you can host the original images via imageshack or something (then link to them on here) I could have a play around with them if you like.

[george7378]

Thanks for the info - in this mode, I think the ISO is limited to 80, and I don't know how to override the F-ratio. Here are the pictures on photobucket:

Lyra:

Cassiopeia:

[EA2007]

Whoa....they are really dark.

Can't do much with them, sorry! You efforts are good with what you have got.

Shame the ISO isn't a lot higher.

[george7378]

Oh well, not to worry. I think the camera also does ISO1600 exposures up to 8 seconds, but I'm yet to try that. I'm not looking to image DSOs or other faint objects (although I might try stacks on M31 and similar bright ones if I can get them afocally) - more constallations, satellite passes and bright afocal objects. I will have to try some guided piggyback shots (I found that my scope has a screw that fits my camera). I am also going to be focusing on projects like sky-scapes and watching planets move with time.

Would stacking ISO1600 8 second pictures give much detail?

Is there a way of reducing noise in images once stacked? Thanks.

[LukeSkywatcher]

I also got a nicer Cassiopeia shot by stacking (starry!)

Any advice on how to get rid of that noise at the bottom would be appreciated.

This really is a very nice wide field image. Cass is very bright and stands out against the other stars and the trees and clouds make for interesting foreground and middle ground points in the composition. The image is a bit grainy though. Not sure how you cure that but i'm sure it is easily solved.

Very dark skies where you are. I'm very envious.

[LukeSkywatcher]

Did you catch M31 or not?

Here is an inverted version of the image. I find that inverting colour often shows more detail. I am not detecting anything in the image that may be M31.

Maybe someone else can:

[EA2007]

Would stacking ISO1600 8 second pictures give much detail?

Is there a way of reducing noise in images once stacked? Thanks.

If you had a good few images, say 10 individual 8 second shots at ISO1600 then yeah you probably would get something. You'll pick up the brightest stars no problem.

As for the noise, well I use Canon Utilities Digital Photo Professional (DPP) viewer and that has a very useful noise reduction filter on it for processed images, you can reduce the chromatic and luminance noise. Its free aswell, just visit the Canon site and look in the support section for EOS dSLR's.

Here's a link - scroll down for the .exe file :

Digital Photo Professional Updater for Windows

[LukeSkywatcher]

I think the way to reduce noise is to take shorter exposure and MORE of them and then stack.

So say if you have 10 exposures of 30 seconds each, It's better to have 20 exposures of 15 seconds each, or any combination. Just MORE shorter exposures and then stack. This will also eliminate star trailing, unless star trails are what you want.

[davew]

Hi George,

You did indeed catch M31.

Well done. Here is a stretched image to show it.

Dave.

[george7378]

Thanks for the edit - that's great! I am currently looking at some movies of the Moon and Venus I captured, and will try and get something from them.

[abumuhannadh]

Hi George,

You did indeed catch M31.

Well done. Here is a stretched image to show it.

Dave.

i agree, Mirach is actually just behind the tree, it could have been easier to identify if Mirach was visible, since M31 is actually not very faint in the picture.