Quote:
Originally Posted by Peter.M
I not sure what values you used for your newt analysis but I will tell you that a 70mm secondary should not produce a 11mm 100% illumination in your scope.
diameter 250mm
ratio 4
diagonal 70mm
inside diameter 265mm
wall thickness 1mm
minimum height 65mm
spare in travel 10mm
additional height for camera 55mm
100% illumination 5.6mm
Generally you want to get the 100% illumination to be larger than the diagonal of your CCD, for the kaf8300 this is 22.5mm.
Just changing the secondary size until the 100% illumination covers the 23mm I get a secondary size of 83mm. Looking at the orion optics AG10 they use a 100mm secondary, obviously these scopes are built for larger sensors but you can see that 83mm does not seem silly.
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Hi Peter,
I've measured my distances, and they're attached.
I didn't realize OO used 100mm secondary for the AG10. So mine's probably undersized. will it make a difference if I used a larger secondary, say 83mm or close, if so what do you think the difference would be?
the base of my focuser is actually 172mm from the centre.
i'll enter the values again in newt and see what it comes up with.
I thought about using a larger focuser, might just do that, but then that's for later cause that'll need a larger corrector and it all adds up quickly.
I'm pretty sure the current 100% area is definitely larger than 5mm because when I view a flat with the qhy8, the vignetting is toward the edges of the frame.
Cheers
Alistair