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DIY Phase centering telescope on the cheap

Posted: Tue Sep 10, 2019 3:19 pm
by Sauerkraut
I bought one of these on eBay, wondering if it could be used for a photo eyepiece (thinking not really because the lens is at the bottom) but discovered that by removing the lens (unscrews) and adding a black disc with a 3 mm hole to the top (drop it down inside from the top), you get a phase centering telescope on the cheap. Possibly it would work with the 2x lens in place - I didn't try that yet.

I was trying to avoid paying $50+ for one and this seems to work just fine, at least in the Optiphot.

https://www.ebay.com/itm/2X-2-times-bio ... SwWlxcfnz1

Re: DIY Phase centering telescope on the cheap

Posted: Tue Sep 10, 2019 11:19 pm
by farnsy
Can you show some pictures of exactly what you did? This project interests me.

I just bought one of those inline bertrand lenses (phase star aperture viewer) from ebay but it arrived broken and I am frustrated with the whole concept!

----- Edit -----

Actually believe it or not, I was able to fix my phase star aperture this evening by taking it apart and banging on it with a hammer to remove a dent, then gluing a mirror back in place. Back in the day companies like American Optical made things to last, even through that kind of abuse!

Still, I find this thread interesting.

Re: DIY Phase centering telescope on the cheap

Posted: Wed Sep 11, 2019 2:46 pm
by billbillt
Yes... I am interested also.. Looks like a good idea to me..

BillT

Re: DIY Phase centering telescope on the cheap

Posted: Wed Sep 11, 2019 3:31 pm
by Sauerkraut
Thank you for your interested farnsy and BillT,

First image - I removed the 2x lens from the bottom of the unit. Possibly you could leave it in.
Second image - From a previous failed attempt at making a telescope, I had fabricated a disc with a 3mm hole in the middle and glued it onto a Nikon CFW eyepiece part - the one that unscrews from the bottom of the eyepiece. Possibly a regular disc without the eyepiece part would work just as well but I happened to have this on hand.
Third image - I simply dropped the homemade disc down into the top of the tube and it fit perfectly.

It's is a tight fit putting this unit into the eyepiece tube and I didn't force it, but noticed that looking through the disc I could see the ring on the backside of the objective and align it with the condenser annulus.

I was under the impression that optics were needed in a phase telescope for it to work, but this seems to work fine. Though I have nothing to compare it with.

Please post images of your homemade versions if you get something to work. I'm sure improvements can be made to the above design since no effort was put into it. Just a case of dumb luck for which I can't even explain why I tried it.

Re: DIY Phase centering telescope on the cheap

Posted: Wed Sep 11, 2019 4:00 pm
by 75RR

Re: DIY Phase centering telescope on the cheap

Posted: Wed Sep 11, 2019 6:59 pm
by Wes
75RR wrote:
Wed Sep 11, 2019 4:00 pm
This might help:

http://www.microscopy-uk.org.uk/mag/ind ... phase.html
I referred to this article when I had to make a phase telescope for centering my microscope.

Re: DIY Phase centering telescope on the cheap

Posted: Wed Sep 11, 2019 7:09 pm
by 75RR
I referred to this article when I had to make a phase telescope for centering my microscope.
How did it turn out?

Re: DIY Phase centering telescope on the cheap

Posted: Wed Sep 11, 2019 8:27 pm
by Wes
It did the job, had to use wooden sticks and tape to keep the two bits together but in the end it all worked out fine.

Re: DIY Phase centering telescope on the cheap

Posted: Wed Sep 11, 2019 8:53 pm
by Sauerkraut
Thanks 75RR - I saw this link, but didn't have the materials on hand to make something similar. Instead I used an old post from this forum on a DIY centering scope that used two eye pieces and a homemade tube. It didn't work, in part due to impatience.

As it turns out, with the eyepiece out and no phase telescope, I was able to find center fairly well, and used the homemade telescope to confirm.