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Celestron 20mm erecting eyepiece + filters

Thu Feb 11, 2016 11:46 am

Hi all,

Complete beginner here, so forgive me :)

I have a Celestron Powerseeker 114EQ and recently purchased a light filter set having read good things about them.
The problem I have is it seems impossible to attach a filter to the 20mm erecting eyepiece. The EP is 1.25", as are the filters, but there seems no obvious place it would fit and no sign of a thread to attach to on the EP itself.
Where am I going wrong?!
Thanks in advance!

Re: Celestron 20mm erecting eyepiece + filters

Thu Feb 11, 2016 11:16 pm

i'm new to this too.. i use a moon filter which screws to the bottom of the eye piece (silver bit) then that either fits in the scope or into the barlow..
Hope this helps


Re: Celestron 20mm erecting eyepiece + filters

Fri Feb 12, 2016 12:15 am

I don't have this eyepiece, but it is designed to allow an astronomical telescope to be used for terrestrial objects, like birdwatching etc. I imagine that since these eyepieces were not designed for astronomical viewing they didn't put a filter thread on the barrel.
Last edited by Aratus on Sun Feb 14, 2016 7:34 pm, edited 1 time in total.

Re: Celestron 20mm erecting eyepiece + filters

Sat Feb 13, 2016 11:01 pm

I'm not actually too sure I know what an erecting eye piece is. You can get erecting prisms to use instead of a star diagonal. Bird watching telescopes have an erecting prism built into them.

So, just to be sure that we are not talking at cross purposes, have you taken the eye piece out of the diagonal and tried to screw the filter into the end of it and then reinsert it back into the diagonal?

Dave B.

Re: Celestron 20mm erecting eyepiece + filters

Sun Feb 14, 2016 7:32 pm

Celestron do manufacture a 20mm erecting eyepiece, and it simply replaces a normal eyepiece to give a 'correct' image rather than convert an existing eyepiece. I think it uses its own internal lenses to flip over the image. I suspect they don't bother to add extra cost to it by including a filter thread.
If someone has a Celestron 20mm erecting eyepiece, perhaps they can chip in and confirm (or otherwise)

(btw. These eyepieces normally can only be used with refractors - an extension tube is required for a reflector.)

Re: Celestron 20mm erecting eyepiece + filters

Sun Feb 14, 2016 11:03 pm

I've googled it now, so I stand corrected. It's still not clear whether the EP has a filter thread.

Dave B.

Re: Celestron 20mm erecting eyepiece + filters

Fri Jun 08, 2018 12:40 am

I realize this is an older thread...i recently bought a celestron 127 EQ....my 20mm erecting eyepiece does NOT accept filters...my set of other eyepieces all have the threaded connection...i wish i could use a filter on the 20mm for viewing right-side-up on the moon, Jupiter, mars, etc...i may try to create a fit for personal use...if anyone has a source for a 20 mm filter, I would sure appreciate the lead...thanks, Tom
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