Re: [APML]the real M13

[Aplanatic@aol.com]

Tony,

Assuming:

Aperture=14.5"
Obstruction=5.5"
Optical Transmission = 80%
Sky Background = 21 mag/arcsec^2
Exposure = 12 minutes
Camera = ST-10

You should record stars to 22.8 magnitude with an SNR of 3.

Dave Rowe


>    I think you might run into problems keeping the core from burning up... 
> and it will be interesting to see how far out you can record... I picked 12 
> minutes at f/8  because at this exposure the blooming wasn't terrible yet, 
> but faint stars should have recorded... speaking of which, I have no idea 
how 
> faint they are... but I'll bet they are very faint... in TEN SECONDS this 
CCD 
> can record what I used to get with color film... so 12 minutes should be 
kind 
> of scary... I am sure someone who knows the math can figure it out... I was 
> using the 14.5" Cass, the seeing was pretty good, and the sky was dark...I 
> have found that last item to be very important when it comes to trying to 
go 
> for the really faint stuff... even a quarter moon will wipe out the S/N.
>  
>        Tony
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