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Hi all,

I was wondering is it safe to observe the moon directly through the eye piece or should I be using moon filters? The reason I am asking is that I tried to observe it last night but it was very bright. When I came away from the eyepiece I found that I could see a negative after image for a while. Is this bad for eyesight? Thanks in advance.

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It's safe, it just completely removes your night vision, so everything will seem REAL dark for a while.

Moon filters are good, you can use the small removable cap in your scopes end cap (if it has that), or for a really cheap option, just wear sunglasses, noone will see how silly you look in the dark. :(

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It's safe, it just completely removes your night vision, so everything will seem REAL dark for a while.

Moon filters are good, you can use the small removable cap in your scopes end cap (if it has that), or for a really cheap option, just wear sunglasses, noone will see how silly you look in the dark. :D

Sunglasses was just what I was thinking :(

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Moon filters are just about the least expensive filter you can get for your scope. Highly recommended if you like viewing the moon. At our public star parties, I usually employ a moon filter on my small scope, and I have had many people say, "that's the best view of the Moon I've seen all evening". I'm sure it is because they are not experiencing the almost overwhelming glare that one gets with an unfiltered scope. ( especially if it has significant aperture ! )

Jim S.

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The negative image that remains is called Persistence of vision and is not harmful, but you can get a moon filter for about £5, the ND 0.96 is a good one

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Although most posts indicate that there is no eye damage likely on viewing the Moon without a ND filter, be careful! I have had problems from this, and am now using a filter.

Chris

what problems did you have Chris? there's no more danger looking at the moon through a scope than with the naked eye - in fact probably less as you are magnifying the image of an object which only reflects light and so magnifying it / looking at a smaller area of it reduces the light intensity per square mm. I use my 16" unfiltered sometimes but actually find the view more contrasty with my Baader Neodymium filter when 50% or more illuminated.

Edited by Moonshane
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what problems did you have Chris? there's no more danger looking at the moon through a scope than with the naked eye - in fact probably less as you are magnifying the image of an object which only reflects light and so magnifying it / looking at a smaller area of it reduces the light intensity per square mm. I use my 16" unfiltered sometimes but actually find the view more contrasty with my Baader Neodymium filter when 50% or more illuminated.

In my case, the problem arose when using low mag with a 5" Mak, looking at the whole Moon. I developed an ocular migraine 2 - 3 hours later, and had a low level after-image for about a week. The difference compared with naked eye may be the fact that I was using one eye only, rather than two. I suppose that as well 400x as much light was hitting the eye.

Chris

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If the moon is very bright (on full moon nights you can read a book by it) then surely it makes sense to filter as a precaution rather than risk damage to eyes or even just the disruption of your night vision.

We have had nights when I couldn't look at the moon through the scope it was so bright it hurt! So we got the afore mentioned variable polarising filter - now i can (could if there were no clouds) gaze at the moon all night long.

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It's something I don't use and don't have a problem with but I can see why others do. It is totally down to whether you feel you need a filter. If you find it difficult to view and it seems too bright then it's obvious it's uncomfortable and you need a filter. As said by nightfisher the ND 0.96 is a pretty good, cheap filter. Some of the very cheap moon filters are rubbish if you want decent detailed views but most are ok.

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