Imaging with a lens question

[Bottletopburly]

So I tried my 50mm lens out attached to a zwo585 mc I need to work on focus but other than that it works now I tried 25sec exposures and that was fine (I’m guiding too) tried 120 sec and I was just a white screen looking over exposed  I don’t think there was a pre stretch preview in Apt , gain 252 (unity ) offset initially 10 but changed to 3 ( zwo default) now should I be able to do 120sec exposure using a 50mm lens ? Idas D2 filter in train and mr blobby was about 50% .

[+Ibbo]

I think you are pushing it at that esp with Mr B arround, was the lens wide open, what f stop?

[Bottletopburly]

 Cheers steve I believe f2.8 steve 

[Clive]

With my Camon D200 at ISO 1600 and the 50mm lens at f2.8, 60sec is my limit (with or without my IDAS filter) under my Bortle 5 sky, otherwise things just get washed out.

[Bottletopburly]

3 minutes ago, Clive said:

With my Camon D200 at ISO 1600 and the 50mm lens at f2.8, 60sec is my limit (with or without my IDAS filter) under my Bortle 5 sky, otherwise things just get washed out.

Cheers Clive that’s helpful 

[+Bino-viewer]

Another 'white screener' here.

I got this with a 30sec exposure with a wide open lens a few years ago. Bortle 7 

Stopping it down to F11 helped, but my light pollution is pretty dire here.

 

Looking terrestrially a 30s exposure in complete darkness turns night into day. Weird to say the least.

I keep meaning to buy one of those 'Optolong Extreme' filters to see if that helps.

 

 

 

 

 

[philjay]

F2.8 is almost wide open and as Steve says theres mr B blasting light everywhere. My tests with a 50mm lens on a moonless night around here gave washed out images at 2 mins f2.8 but stopping down to f4 improved things and star shapes. That was with Canon nifty 50

Edited January 6, 2023 by philjay

[Bottletopburly]

36 minutes ago, philjay said:

F2.8 is almost wide open and as Steve says theres mr B blasting light everywhere. My tests with a 50mm lens on a moonless night around here gave washed out images at 2 mins f2.8 but stopping down to f4 improved things and star shapes. That was with Canon nifty 50

Thanks Phil that’s excellent info I will reset lens to F4 at have another stab 👍