Quote:
Originally Posted by Peter.M
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.
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Hi Peter,
I'm probably using different values but I get a 7mm illuminated circle.
screenshots attached.
pls let me know which one's off??
what I did notice is that the 22mm distance I have for the focuser base to the inside of the scope reduces the illuminated area.
so if I move the focuser inward by 22mm, it doubles the area with the same secondary.
I would of course have to move the primary down else i'll have to use extension tubes.
what is the end result of a larger circle? any change in contrast or sensitivity, as in more light??
Alistair