How to improve my M31

[Mered]

Managed to get out for the first time in months last night and finally got around to capturing M31.

Sort of happy with the results. 30 x 60 sec lights at ISO400, plus 13 darks and 10 bias. No flats yet. It was stacked and processed in DSS, with a little bit more processing in GIMP before converting to jpg.

What can I do to improve it? Longer exposures? Go up to ISO800?

It was hard to bring out the detail in the edges without blowing out the centre and also introducing noise in the edges.

[ianaiken]

I think you've mentioned two things in your post which I think will help improve.  1. Take some flats, this will balance the exposure across the frame and also remove what I think may be some vignetting on your image.  2. It is hard to not to blow out the core and at the sametime get any detail from the edges.  I think you may need to process the image twice, one to get the core and the other to get the outer.  Then use photoshop or other package to merge them together.  There are quite a few good tutorials on the internet on how to go about this.  Processing is an art and is harder than taking the actually images in some cases :-)

[StargeezerTim]

Very nice!

I think iso 800 would better. I take it you are not guiding? If not, then you could try upping it by 15 secs a time and see what you can get away with without star trailing. Doug German does a very good tutorial about curves on You tube. He shows how to stretch from a point but to lower the curve to a straight line to the white point in order to lighten fine detail without blowing the core. Its a photoshop tutorial but can be tried on GIMP.

He explains it and does it much better than I do! 

[Mered]

Ian,

I'll try processing the image twice, not an idea I'd thought of. You're not wrong about the processing being the hardest bit! Gives me something to do when the nights are cloudy though

Tim,

Correct, not guiding. I do have a guidescope and autoguider, but not yet even had a chance to set it up. I did a 5 min test shot of Deneb when I was setting up, which did have a very small amount of trailing, so next time I get out I will have a go with getting the autoguider set up. I shall look up those tutorials as well.

Thanks both!

[Tim99]

Very nice!  You took this through your ED 80?  I am just starting out in this Astrophoto game.  I've read a lot and am starting to assemble the hardware to get started.  i have a nice ED 80mm Refractor and just bought the CGEM mount and a SCT.  Anyway, thanks for sharing that picture!

[wxsatuser]

Ian,

I'll try processing the image twice, not an idea I'd thought of. You're not wrong about the processing being the hardest bit! Gives me something to do when the nights are cloudy though

Tim,

Correct, not guiding. I do have a guidescope and autoguider, but not yet even had a chance to set it up. I did a 5 min test shot of Deneb when I was setting up, which did have a very small amount of trailing, so next time I get out I will have a go with getting the autoguider set up. I shall look up those tutorials as well.

Thanks both!

If you can do 5minute exposures it will make a huge difference, 10 minutes even better.

But don't over expose.

Use the histogram and get the peak somewhere between 20 and 40%

The histogram peak is the sky brightness and this dictates the length of exposure.

Here is where I normally put mine for 5minute exposures at iso1600, yours will be different, depending

on sky brightness, iso, scope f ratio and how long you can track accurately.

[Mered]

Very nice!  You took this through your ED 80?  I am just starting out in this Astrophoto game.  I've read a lot and am starting to assemble the hardware to get started.  i have a nice ED 80mm Refractor and just bought the CGEM mount and a SCT.  Anyway, thanks for sharing that picture!

Yes, this was with the ED80. Very pleased with the scope and the mount. It's a lot to learn, and I'm still very much at the beginner stage still, but every time I go out I learn a little bit more. Looking forward to seeing pictures from yours once you get going

[Mered]

If you can do 5minute exposures it will make a huge difference, 10 minutes even better.

But don't over expose.

Use the histogram and get the peak somewhere between 20 and 40%

The histogram peak is the sky brightness and this dictates the length of exposure.

Here is where I normally put mine for 5minute exposures at iso1600, yours will be different, depending

on sky brightness, iso, scope f ratio and how long you can track accurately.

What camera is that? Mine doesn't have a histogram on the LCD, but I could take the laptop out and check them on that.

[nigelbeaumont]

I don't know if it applies to all Canon EOS models, but on my 450D while looking at an image on the LCD screen I can get a histogram of it by repeatedly pressing either the menu or display button (can't remember which) - it cycles through the image, the image with number of shots, basic histogram and then RGB histogram

[JR1987]

If you can do 5minute exposures it will make a huge difference, 10 minutes even better.

But don't over expose.

Use the histogram and get the peak somewhere between 20 and 40%

The histogram peak is the sky brightness and this dictates the length of exposure.

Here is where I normally put mine for 5minute exposures at iso1600, yours will be different, depending

on sky brightness, iso, scope f ratio and how long you can track accurately.

When you say thats where you put yours.. Im getting a little confused.  Do you live in an exceptionally dark area? I dont think I could manage a 5 minute exposure at iso1600 without just getting pure white for an image.

This is how mine came out from a 3 minute exposure at iso 800

[tingting44]

great image for such a short amount of data!

i went for 10 min subs @ iso800 last season, here is a single 10 min RAW subs, not touched or processed from last year

M31  (single RAW 10min sub - NO PROCESSING) by Martin Young, on Flickr

 

best thing you can do to improve your image is simply to get more data and a lot of it! for as long of an exposure you can get away with, without your histogram rising above around the 1/3'rd mark

[JR1987]

No processing???? how the hell did you get it so clean without any wash of white or orange over the top??

[tingting44]

No processing???? how the hell did you get it so clean without any wash of white or orange over the top??

thats what long exposures do when you are at a dark site orange over the top would be light pollution my friend and will only show worse the longer exposures you do

this is the link to my finished image if you were interested...

https://flic.kr/p/rUBRWP