Quote:
Originally Posted by alistairsam
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
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Using the numbers you provide, newt spits out a 100% illuminated area of 0mm which may explain what you see. Your tube inside diameter is distance A on your diagram times 2 so 300mm. Then all you need to do is make sure all of the other values in newt sum to be the 144mm of extra distance to the focal plane and it should give you the same numbers.
What you may be seeing with the qhy8 is vignetting of the 75% rays in the corners of the chip. Though I am not familiar with that.