And now for my other subject from last session

[LewisM]

After the Skull Nebula settled behind the roof line, I swung over to the Rosette Nebula last night (well, morning actually).

Details:

Vixen DED 108SS astrograph refractor (f/5)
SBIG ST-8XE mono with Astronomik Ha-LRGB set (only Ha used)
Total of 1 hour (6 x 10 minute Ha frames)
Vixen GPD2 mount, Synscan GOTO system controlling
CCDStack sigma-reject, Catmul-Rom, and a median stack


I know it needs more, but VERY happy with the start to proceedings.

Biggerer and betterer: http://www.astrobin.com/full/63277/0/

[Larryp]

Looks excellent, Lewis

[wayne anderson]

Very good Lewis, lots of detail in there, keep adding to it and it will look even better.

[rmuhlack]

looks like a great start, and I can't see any obvious blooming there either. is it simply dithering that has brought the blooming under control (together with a sigma reject / median stack) or are you using some other tricky method ;)

[renormalised]

Ha Ha Ha Ha Ha Ha :) :P

Nice shot :)

[gregbradley]

Very good shot Lewis. The stars look to be oversharpened. That is problem when you use sharpening applied to the whole image. Its best to use a layered approach to sharpening where you control a mask and make it selective. Or a star mask to prevent the stars from being sharpened as they damage easily.

If you are not sure how to do that and have Photoshop PM me and I can walk you through it.

Greg.

[LewisM]

Another tricky method - CCDStack and MaxIM handle blooming pretty blooming well.

Dithering didn't do too much to the bloom actually (though great for noise reduction)

[LewisM]

Greg, thanks for that - I do have an action for star selection, and didn't use it - MEA CULPA!

I'll go back to the raw export tiff and take it on again. Stay tuned. If I fail, you'll get an email :)

[LewisM]

Took another go with Greg's suggestions.

Hmmmm.... more data please :)

http://www.astrobin.com/full/63289/0/

[gregbradley]

Thats very nice now. Its an excellent image. Sure, more data is always good but at the size image I am not sure what you are seeing that requires lot more data. Is it noisy zoomed in?

I often shoot Ha 2x2 because usually its just adding some red areas to a colour image and 2x2 Ha is often much cleaner and the stars are already smallish in Ha. Getting the signal up quickly in limited imaging time is the game.

Greg.

[DavidNg]

I think it is better too with your new photo. Perhaps you can try longer sub to increase S/N? I see other folks often use 20min or even more with Ha. I too will try to shoot 2x2 Ha as Greg has suggested.

[LewisM]

I love shooting 2x2, as the results look fantastic when downloaded in preview, but I find them a little more problematic when it comes to tidy up. Besides, binned x2, the SBIG ST-8XE images are SMALL at 756 px.

[LewisM]

Now to fill it with LRGB tonight (fingers and toes crossed)