Galaxy imaging with DSI's

[Ric]

Hi all,
does anyone know of any imaging tips for capturing galaxies.
I have this problem where I can get the arm detail with a long exposure but tend to burn out the core or it's the opposite where I can take a shorter image and detail the core but lose the arms detail.

Any ideas/tips or a website link would be greatly appreciated.

cheers

[ving (David)]

you can combine images in photoshop cs in HDR or look up easy HDR. what you do is get your arms (by over exposing thw core) in one exposure and under expose the arms to capture the core in another (and maybe a shot in between too) and combine them.

[Ric]

Hi Ving, thanks for the advice, I'll give that a go. I use Maxim but I'm pretty sure I can achieve the same goal.

Cheers

[Gama]

Why not just take shorter exposures and then just combine (Stack) them.
You then get the image you want. Plus stars tend to be much smaller and rounder.
Heres an image i took recently while trying to image very faint and small galaxies.
Its a small group of 5 galaxies with the barred spiral being 2.9 arc minutes and 14th Mag.
Since i wanted detail without bloating or saturation, i shortened exposures to 20 and 30 seconds each (I used a 22" f4.5 Newtonian and a SXV-H9) with a total combined 8 minutes.

[Ric]

Thanks Gama, I try that as well, tonights looking pretty good so far.
Normaly my exposure times are 40 - 60 seconds so I'll try halving the exposure times and see how that goes.

cheers

[asimov (John)]

http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM

[Ric]

Thanks Asimov, I've just printed that off for a hard copy

cheers

[rogerg (Roger)]

I use a combination of layers (with masks) and "Curves", only using Levels to chop the extremes.

If you can get the whole thing in to photoshop as a 16bit file (16bit TIF) then using curves is quite easy. My problem is converting a FIT to a 16bit TIF. All CCDSoft will do is 8bit TIF or 48bit TIF, my photoshop can't read 48bit TIF and 8bit TIF is too "shallow".

To combat that, I save about 3 TIF's, use curves on each and merge them with layers.

I have often wondered if something like ImagePlus gets around this, if it provides curves etc for use directly on the 16bit FIT files.

Oh, and it's a bit of a tricky trial and error process to get the brightness evenly spread but not make it look fake or have 'dead patches' of brightness where it looks obvious it shoudl be brighter. The M42 example at the previously posted link is OK but to me the core needs to be a bit brighter, because it should be.

Roger.

[Doug]

The Jerry Lodregus link is also based on film images that obviously have been scanned. No difference to technique, but don't be guided by the pictorial too much. Look at the article section here on IIS there is an article detailing HDR processing,
http://www.iceinspace.com.au/index.p...63,294,0,0,1,0
or go to :
http://home.vicnet.net.au/~tishuios

I don't know what is going on with IIS, the last part of my web address is one word; it is displaying as two??? tishuios

Roger, hunt up 'fits liberator' plug in for photoshop. Mine loads fits @ 16bit.
If you have trouble finding it drop me a line.
Cheers,
Doug