M8 - The Lagoon Nebula

[IanP]

Last year I took some shots of M8 with CPC925 and 0.63 reducer; the field included just the “core”. This year I’ve been planning to get it framed better, with the emphasis on the core, but squeezing in some surrounding nebulosity.
I'm in the process of evaluating a new camera-telescope setup, which means - discovering new problems. The setup (see attached photo) consists of the following: Orion ED80TCF, EOS 60Da and Canon EF 2x III Extender.
So here is an image of last-Friday-night's work.
The total exposure time was worth more than 3h in 1.5-2min subs.
Processed in PixInsight with the final touch in LT4, and StarSpikes added in PS.
Thanks for looking.

[Larryp (Laurie)]

Very nice!

[multiweb (Marc)]

Load of scope on the fork mount. First off, excellent data. Due for a repro though. You've clipped the hell out of it. Watch your histogram and you'll have one for the cool wall.

[gregbradley]

That looks quite good. As Marc says its probably a bit black clipped (the extreme left of your histogram is probably cut off some of the dim bits).

If you saved your processing at various stages you could continue the processing from the point before it got clipped and bring it forward keeping an eye on the histogram as you go.

Greg.

[IanP]

Thanks Laurie.

Thanks Marc.

Load of scope on the fork mount.

So far the original gear holds.

Due for a repro though. You've clipped the hell out of it.

I think I’ll wait for the next opportunity to collect more data and then reprocess the whole lot once again. I’m still worried about the background noise (one major reason for clipping) as I take most of shots at quite high ISO …

Cheers Greg.

That looks quite good. As Marc says its probably a bit black clipped (the extreme left of your histogram is probably cut off some of the dim bits).

Yes, I’m going to address this issue at the next opportunity, although looking at histograms (PixInsight HT) I can see only traces of clipping, could be the AUTO function in the ScreeTranferFunction.

[gregbradley]

Using auto anything can be a worry. I use auto on DDP in CCDStack but I probably shouldn't. It sometimes can cause a slight black clipping.

Greg.

[jsmoraes (Jorge)]

I’m still worried about the background noise (one major reason for clipping) as I take most of shots at quite high ISO …

My experience with Canon (Rebel XT) tell me that high ISO and long exposition time generate much noise and let the stars in RGB saturation. Different from mono and filters, long exposition time is dangerous to bright areas. My best work with M 42 was done with multi set of ISO and exposition, and assembled in full image with layers and mask

I can think that with color camera the time of exposition is similar to 3 times with mono camera. Since you capture at the same moment three information: R, G and B (and without any attenuation)

I read, here, some texts with different informations. But they don't correspond with the behavior of my Canon.

Now, my preference is low ISO, moderate exposition time and long session (numbers of frames)

[IanP]

Now, my preference is low ISO, moderate exposition time and long session (numbers of frames)

Thanks Jorge, I wish I could apply your way of taking photos, but I’m located not far away from the CBD and therefore my exposure time is limited to roughly 2mins.

[White Rabbit]

Nice shot Ian.
Get yourself a light pollution filter you should be able to stretch your subs out to 5 to 10 mins depending on you iso.

I live 7 clicks from Sydney cbd and could do 5 min subs easily with my 1000D. I had the cls filter from astronomik it's very good at suppressing light pollution.

[astronobob (Bob)]

Quite an awesome result from a Dslr Ian, it does appear a little black clipped though I wonder if it just a side effect of such short subs from being in LP, from what you have pulled out from your 2min subs is quite remarkable, and plenty of them have works wonders, Great capture