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Old 05-03-2018, 11:35 AM
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Windston (Dan)
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Newtonian flats without light leaks? Is it possible???

Like the title states, I've recently been having a bunch of trouble taking flats with my Newtonian. At night time, the is pretty much 0 light entering the system from the primary cell or the focuser, it's pretty much only from the sky. However during the day when trying to take flats, light is obviously entering the system through the primary mirror cell, as the primary mirror back is basically completely exposed, and the gaps from the focuser fit to the tube isn't perfect.

My question is, how the hell do I combat this? I've done in the past a pure black t-shirt doubles over the primary cell and held on with a rubber band (over the back of the tube), and another black t-shirt over the focuser, but I don't think it's perfect and it's a lot of dicking around, is there a better way?


Last edited by Windston; 05-03-2018 at 01:58 PM.
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Old 05-03-2018, 06:33 PM
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ChrisV (Chris)
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I've had similar problems at night as I shoot from a verandah with house lights behind the scope. It came up as weird circular bands of light from around the primary making internal reflections (more noticeable on dim objects that need more stretching). I got a roll of black alfoil from a stage lighting shop and strapped it over the back of the newt. Comes in 30m rolls. I also used plain alfoil and that seemed okay
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Old 05-03-2018, 07:24 PM
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peter_4059 (Peter)
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How about a lightbox and take the flats at night?
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Old 05-03-2018, 07:31 PM
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billdan (Bill)
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I put an old Collingwood beanie over the back of my 8 inch Newt, to stop stray light getting in from the back.
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flat, imaging, newtonian

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