Help with getting more detail

[theghettostylus]

Last night I got set up to take some exposures of M31 I took 32 30 second shots with 40 darks and 50 bias (probably went over board) anyway when I put them in deep sky stacker there wasn't much detail coming out, I could see it was there but no tweaking would bring it out :/ there is a bit more light pollution now the big tree is chucking leafs down. I am using my 150p on my eq 3-2 mount head and pier with ra and Dec motor drives, has anyone got any advice on how to get more detail with the setup I've got?

Thanks

Jason.

[PeterCPC]

You don't say what camera you are using but you really need long exposures for M31. Its got a bright core but the rest is quite dim so you really need to be guiding and get long exposures.

Peter

[theghettostylus]

The center was very bright, I will see how long I can push the set up to. One day I plan to upgrade when I learn how to save money aha I'm using a Canon 1000d I know it's not the best kit but it's definitely sparked my interest in astrophotography.

[PeterCPC]

The Canon 1000d can give reasonable results but you still need longer exposures to get the detail out.

Peter

[Knight of Clear Skies]

The 1000D is a pretty good camera for AP. What were your exposure settings please, I'd expect to see some detail on Andromeda with a 30 second sub at f5. I got this with a single 1 minute exposure (ISO3200) at f5.6, using a 250mm zoom lens.

However, I was shooting from a very dark site, it could be that light pollution is washing out the image at your location. There are better targets for unguided imaging, as Peter says the core is bright but the arms have a low surface brightness. It can be shot successfully unguided but it's easier with a fast telephoto lens.

[theghettostylus]

I wasn't using a lense, I went the afocal way. That's a very nice photo. I could see the outer parts on the finished stacked photos but it was very very dim. I only have the 18 55mm kit lens and a 2.2 telephoto converter at the moment. I will try and bring the exposure up next time it's clear! I know I won't get amazing results but to see a bit more detail would be nice.

[D4N]

If your scope can achieve prime focus with your camera that would be the way to go. You lose too much light with afocal for deep space imaging.

/Dan

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[wimvb]

Last night I got set up to take some exposures of M31 I took 32 30 second shots with 40 darks and 50 bias (probably went over board) anyway when I put them in deep sky stacker there wasn't much detail coming out, I could see it was there but no tweaking would bring it out :/ there is a bit more light pollution now the big tree is chucking leafs down. I am using my 150p on my eq 3-2 mount head and pier with ra and Dec motor drives, has anyone got any advice on how to get more detail with the setup I've got?

Thanks

Jason.

I have a similar setup (SW 150P, EQ3-2 goto on a tripod, Pentax K20D unmodded). If your polar alignment is ok, you should be able to get longer exposures (2 min, depending on light pollution)

You will need to stretch the image after stacking, ideally in a suitable software package (PhotoShop, PixInsight or the like)

Even on a well exposed and low noise DSLR-image, you will hardly see any details without proper postprocessing.

[theghettostylus]

thanks for all the info on more detail, I put all the images through DSS again and then messed with the end result in light room, I then noticed both photos have green, blue and red streaks in. can anyone tell me what causes this? they are grey when DSS has finished but they get colour when messing around in light room.

to add the photo is terrible and just wanted you to see the strange coloured streaks for yourself. 

thanks 

[wimvb]

Never seen these Before. Are they on the raw images? If not, they must have been introduced by the stacking process.

Could this be residues from hot pixels? Should have been taken care of by the darks.

[D4N]

Yes those are hot pixels. The stacking process has turned them into little lines as each sub frame is slightly adrift from the last. I assume you aren't guiding as when there is no drift between images they stay in the same place or zig zag around if you dither.

There are a few settings in DSS that can help to get rid of these.

/Dan

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[theghettostylus]

Thanks for the info. Will look into it on DSS, I couldn't see them on the raw files. It makes sense with not guiding that they are turned into lines. I put mosaic stacking on this time and doing think they were there when I used the recommended setting. Will give it another go and see if they are still there.

Thanks again

[Knight of Clear Skies]

That's a good result considering your setup is far from ideal. DSS has a stacking option to remove hot pixels, I use that myself rather than relying on darks. Also, the kappa-sigma stacking option is very good at removing artifacts, satellite trails and the like.

[theghettostylus]

I will give that a go depending on if it's clear or not later, I was surprised at the end result. But it's fun no matter what the picture turns out like so I'm happy.