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Crosshair eyepiece for rightangle finder scopes - where to find?

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#1 tmozdzen

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Posted 28 November 2021 - 06:05 PM

I have come across an old inventory of finderscopes. Many of them are lacking the eyepiece, and many of them have eyepieces that don't have the proper focal length - the focal length is too short I believe as I can't get the eyepiece in far enough to focus it.

 

Does anyone have suggestions as to where to pick some up?



#2 Frugal Astronomer

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Posted 28 November 2021 - 07:01 PM

I just spent the past couple weeks looking for them and they are hard to find.  I bought a used Stellarvue 50mm finderscope that didn't come with an eyepiece.  I eventually ordered one from Agena Astro.  Most come with a reticle light now.  Very hard to find a simple one without a light.  I got the AA 24mm without light.


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#3 Jon Isaacs

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Posted 28 November 2021 - 07:46 PM

A few thoughts:

 

Do these finders take 1.25 inch eyepieces?  What eyepieces are you trying to use?

 

The focal length isn't the issue, it's the location  of the focal plane/field stop/cross hairs..

 

Jon


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#4 Sincos

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Posted 28 November 2021 - 08:06 PM

For the ones with eyepieces have you tried each eyepiece,  on the ones lacking eyepieces to see if you are lucky enough to get a match ? If as Jon above asked they are 1.25 inch eyepieces try a variable zoom or two to try and zero in on the focal length you need. That’s my  $.02 worth. Good luck tracking down the solution.


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#5 havasman

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Posted 28 November 2021 - 08:06 PM

Astronomics, Agena and Stellarvue all offer reticle eyepieces with and without the illumination module. You can click on Astronomics link at the bottom of every forum page and search for ILLUMINATED RETICLE EYEPIECE. The Astro-Tech is a good one and 24mm focal length.


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#6 tmozdzen

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Posted 28 November 2021 - 10:55 PM

Thanks guys!

Yes, they take normal 1.25" eyepieces and I do have a few that work just great. Some have adjustable focus and all of them have the primary lens location adjustable.

I have no idea how the originals got lost, and I'm pretty sure the person replacing the eyepiece had no idea period or else they too were out of luck looking for a replacement.

I'll start checking and post what I find here.

Thanks everyone for the tips.

Tom



#7 Jon Isaacs

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Posted 29 November 2021 - 09:00 AM

Tom:

 

Finders that take standard 1.25 inch eyepieces generally have plenty of inward focus, normally with a standard eyepiece, you'd have to pull it out some.

 

This is because an illuminated reticule cannot be placed in the barrel, it has to be in the body.

 

It is possible to add cross hairs to many regular eyepieces. It's a bit tricky but it's what I do. I use 0.004" hard brass wire, larger than normal. I can still see the cross hairs under the darkest skies and I can use better eyepieces.  Currently I'm using a 20 mm 68° Explore Scientic.  

 

Finders are normally about F/4 so a quality eyepiece makes a big difference.

 

Jon


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#8 tmozdzen

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Posted 02 December 2021 - 12:22 PM

I'm in luck, I found a stash of crosshair finder scope eyepieces.

I have no idea why there was a case full of crosshaired eyepieces, but I'm thankful.

These were from the late 80s/early 90s.

Thanks,

Tom



#9 davidgmd

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Posted 02 December 2021 - 07:29 PM

I'm in luck, I found a stash of crosshair finder scope eyepieces.

I have no idea why there was a case full of crosshaired eyepieces, but I'm thankful.

These were from the late 80s/early 90s.

Thanks,

Tom

Beats a case full of cross-eyed hairpieces. Rim_Shot.gif


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