Starting Point for Cocoon Nebula

[nightster]

If nothing else goes wrong I will be imaging on Friday for the first time since May. Actually only 4th time and I am using my new scope, an 80mm triplet.  According to my research the Cocoon Neb will be near zenith about the time I could begin collecting data.  The one item I don't know and don't want to guess is exposure length. How can I best determine a starting point for exposure?  Some facts: Edge of Red zone, Guided Eq6, 80mm F6 w/ unmodded 450D, IDAS LPS filter, BYEOS.  

Thanks, Jeff

[tingting44]

simply do a few test subs. expose for 5 mins, check histogram, add to sub length or subtract till the histo is roughly 1/3rd saturated, and off you go

[red dwalf]

as above

[nightster]

Weekend turned out awesome. Even though I made a timing mistake in aquiring data the hardware all worked, the mount guided well and the refractor takes so much worry away vs a reflector. Had fun too.

[Kirscovitch]

Nice capture. What did you end up with for exposure settings?

[tingting44]

nice one, what length sub did you go for and iso?

[nightster]

I followed your advice and started low around 120 and checked Histo. Ended up at 300s @800iso. I had gone up to 360@1600 but it seemed noisy. I had perfect conditions except for a 2 hour cloud delay. I thought I was being smart and took darks and flas waiting for the intermittent clouds to clear. Problem is after I got the first sub to look good I set BYEOS on its way but a dust mote appears on all subs after that 1st one and I didn't notice it during the run. So a new law of AP for me to follow, Always take flats at end of an imaging run.

Also the processing is rubbish as this is only the third DSO I've captured and processed, still learning basics of PI. Field flattener also needed, that image is isnt cropped and the corners show curvature. Also I know using a unmoderated DSLR for Ha Nebula is not ideal. Even with the problems I noted I am still very happy. Guiding was solid, I have a screen shot in my gallery. Astrotortilla worked very well.

[nightster]

Ok, so I'm trying to use PI to process and  the Light Vortex step by step tutorial, and this is where the image seems to get weird. Maybe someone can comment if I am moving in the right direction.  If this is not the right forum for this question I can move the post.  Thanks for any help in this area.