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craigfoot

Skywatcher 130 dustcap

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Hi

Quick question. . the dust cap for my explorer 130 has a small maybe 1.5" removable cover to one side of it. . what's it for??

Craig

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Reduced brightness is the general idea.

Could as easily drop a 30% ND filter in (Moon filter).

You may find it not too bad at full aperture, so consider it as there in case.

If you decide to view the sun and cover that aperture then cover the finder as well or remove the finder.

Edited by ronin
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I've often  observed the Moon with the (2") 25mm aperture only.  This  reduces, the overall brightness,  just fine for  my observations, Sometimes the Moon just feels too bright, and you end up with night blindness (NOT PERMANENT) I'm also aware that with a 2" aperture my telescope gives me 150x  at f/48 using my 8mm?  There should be two caps on the OTA dust cap. One removeable, the other is sized accordingly to hold the one you remove, so its safely stowed!

I read recently ( although not tested the theory yet) that by using the 2" aperture and a low focal length EP, this actually increases the definition of the Airy Disk?

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Using the small aperture does reduce brightness but also reduces the resolution visible, so gives less detail. An ND filter is better but obviously costs a bit more. Generally in that sized scope I think observing at full aperture makes sense

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Ah so the reduced aperture impacts on other variables like magnification and focal ratio. . I'll give it a try next time I'm out

I've got a cheap basic moon filter that sorta turns it green. . . is there a real benefit to getting a more expensive filter?

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It won't affect magnification as the focal length remains the same. It does increase focal ratio, and so can improve the performance of some of the less good eyepieces out there.

It will also reduce the exit pupil you see, which may not be a good thing at higher mags as you might start to see floaters in your vision.

If you really can't deal with the brightness, I think the best bet is a neutral density filter which reduces the brightness but keeps it a natural colour.

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...........  There should be two caps on the OTA dust cap. One removeable, the other is sized accordingly to hold the one you remove, so its safely stowed!

Good grief!  So that's what it's for. :rolleyes:   

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