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Old 07-01-2006, 08:14 PM
ausastronomer (John Bambury)
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Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
Posts: 2,620
Bruce,

If all the light angles are not at 90 deg you get flaring and significantly increased aberrations. Conduct a little experiment to see for yourself:-

Take a magnifying glass and focus the sun on some dull concrete, hold the magnifying glass at 90 deg to the angle of incidence of the sun then move the glass closer or further from the concrete until the suns light is focused as the smallest possible little round spot. That's how it should be. Now angle the magnifying glass (keeping the distance the same from the concrete) and you will notice the spot fan out on 1 side with a triangular shaped tail. This aint how it should be and this is exactly what happens to your round star images when things are not perfectly at 90 deg. The experiment exaggerates things a little but you get the idea. When the magnification is increased, collimation errors are critical with fast F-ratio scopes.

Its worth taking the time and learning to collimate your scope properly. With the tools you have and have on order you have all the necessary equipment to do the job properly, now its just time learning and patience.

CS-John B
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