Quote:
Originally Posted by Allan_L
Hi Mike,
I have a Celestron SCT (CPC1100).
I have tried a previous one of these, but there is this big plastic cover (over the central obstruction) in the centre of the lens that makes it difficult to place the mask flat.
Do you think it may be possible to cut out a central hole to let it lay flat against the lens.
Or do you think it would be better to oversize the mask to sit on the outer tube rim.
The mask would be about an inch from the lens in that case.
I am unsure how this would effect true focus.
Any ideas?
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I don't think it would affect focus if you put it one inch from the lens but it might be harder to mount as the mask will be one inch away from the scope and will hang on the trim only.
I can cut out the centre from the mask so it would fit on the plastic cover but it would probably reduce your scope aperture. There should be a solid ring at least 5-6mm thick around the hole. And this would be taken from your scope aperture unless plastic cover diameter is less than the central obstruction diameter.
We can do also what Dennis suggested and I will leave the solid centre on your mask but there might be another problem. Your mask aperture is already very close to the maximum I can cut. If you add too much for you mask OD to mount it on the trim it will exceed 290mm OD I can cut.
Regards,
Mike