NGC6888 best exposure time?

[myk68]

Hi All

A quick question before tonights hopefull clear skies.

I got 7 300 second exposures in luminosity the other week but when I stacked them I didnt have as much detail as I thought I would.

The question is would a one hour exposure be better than say 12 300 secs.??

oh the equip I was using is the SW ED80 with camera on a star diagnol and through the atik filter wheel if this changes the F stop.

Mike

[roundycat]

it's unlikely that you will need a diagonal for what you are doing. Just something else to hang limp, drop off, reduce the light throughput or just get in the way.

There have been many debates about one hour versus 6x10 minutes, bottom line is you cannot eradicate many of the forms of noise or interference if you only have one or two exposures. Best to go for 5m as you have been and if it doesn't give you any trouble with tracking or star bloat/bloom then extend it to 10m and then 15m. In truth, 15m is likely to be as long as you need to go.

Dennis

[myk68]

Cheers for that roundycat. I have the diagonal on as I can't get focus with out it. Which was a surprise to me on the ed80.

[Psychobilly]

You wold be far better off replacing the diagonal with an extension tube and keeping everythign in line... soemthing around 50mm should do the trick...

Peter...

[myk68]

Cheers peter Ill see if i have anything that will do. I think I tried the tube i have but the thread goes in to far and stops the filter wheel

[Psychobilly]

I think I tried the tube i have but the thread goes in to far and stops the filter wheel

I had a similar problem with the thread interfering with the prism arm on an OAG.. I shortened the thread back...

I wish there was some "consistency" in thread lengths

Peter...