DIY moon viewing filters and rings to reduce chromatic aberration w/ 20x80 binocs?

[Om_Audio]

I have a pair of Zhumell 20x80 SuperGiant Binoculars:

http://www.amazon.com/Zhumell-20x80-.../dp/B0006OC490

I read somewhere that you can reduce the aperture of the primary lenses to reduce chromatic issues and more easily view the moon. Does anyone have info? I would like to make something for tonight's lunar eclipse viewing.

As for neutral density filters I have never read anything DIY but would appreciate info or links to products that would work with my binocs. Not sure if filters will work with my eyepieces.

Thanks!

O

[julianh72]

Well, for one thing, the Moon will be MUCH dimmer than normal during the eclipse (especially if you can get an early moonrise view during totality), so I would have thought reducing aperture shouldn't be necessary?

[Om_Audio]

I will be viewing the moon before and after and other days so still need the info. I am going to make some cardboard cutouts tonight and try to make perfect holes and enlarge them to taste. I will have great full sky view from 1500ft peak in local mtns. Total eclipse here is around midnight and moon was at 30degrees or so last night around 8 or 9pm so will be pretty high in the sky not at all near moonrise- I am excited.
Thx.

[Renato1]

I really wouldn't think you'd need to do anything to your binoculars for tonight.

That said, making an aperture mask is simple. get the cheapest black plastic folder that you store loose A4 paper in. Mark it with a compass, and cut out two discs that cover the front aperture. Mark the smaller aperture that you want and cut that out, so that you have a disc with a big hole cut out of it.

I then just cut out a long strip of plastic, wrap it around the front tube and tape it together, then put the disc next to the wrap, and tape the disc to it with lots of black insulation tape. You then have an aperture mask that you can easily slip on and off.

Alternatively, just for tonight, you can just tape the aperture mask to the front of your binoculars.

As for filters. If you have a lot of eye relief, just get the filters that you'd use on a telescope eyepiece, put a small amount of Blutack or other reuseable adhesive around the metal edge, and stick it over the front eyepiece.

This Blutack trick - if you have the long eye-relief - also works extremely well with nebula filters on binoculars. Curiously, it actually works best if you only use one nebula filter over one eyepiece, and superimpose the filtered and unfiltered images. When I've used two nebula filters in binoculars I thought the view was too dark, and I didn't actually see any more nebulas than by using one alone.

Back to the moon, if you don't have a neutral density or polarising filters, the other thing you can do is go look for cheap $5 sunglasses that seem to give the clearest image, then cut bits off them with heavy duty scissors, and stick those bits over the binocular eyepieces with Blutack.

They used to sell Ambervison and BluBlocker sunglasses in $2 shops, which were great for cutting up and attaching to eyepieces. They were actually better than the telescope eyepiece filters I'd bought for my telescopes to view Jupiter - but you do get the yellow colour over everything.
Good luck,
Renato