Which scope has the fastest exposure time and why?

[cuivenion]

I'm still struggling to wrap my head around exposure times, mainly due to contrary views being expressed on posts that I've read. Here's my question:

I have two scopes, 130mm F5 (650mm FL) reflector, and a 200mm F5 (1000mm FL)reflector. Which one has the fastest exposure time and why?

Thanks for your help.

[wimvb]

Neither. The name of the (astrophotography) game is not chasing brightness, but chasing signal to noise ratio (SNR). One can always brighten an image during processing.

Increased brightness is only better if the noise doen't increase with it. In the case of the larger (200 mm) scope, it will collect more photons in a certain time period, and therefore lead to better SNR.

That's the short version. The long version of this topic was discussed earlier this year (would have to look it up), and is called the F-myth.

Hope this helps.

Did look it up:

 

[cuivenion]

Thanks for the reply, I'll have too re read that thread.