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10" f/10 Thompson Optical Refractor

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#26 clamchip

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Posted 09 October 2022 - 11:47 AM

I got your clam beat: 

 

post-50896-0-39729700-1576599871.jpg


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#27 jragsdale

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Posted 09 October 2022 - 01:00 PM

I got your clam beat: 

 

attachicon.gifpost-50896-0-39729700-1576599871.jpg

Whoa! What happened?


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#28 clamchip

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Posted 09 October 2022 - 01:52 PM

It's the way I got it. It came from the Olympic peninsula, we have a lot of Navy Bases over there. 

Traded with a friend, we think it came from a junk yard so no body really knows what happened.

My own thinking is my Tinsley was sent out to observe a atomic test but it turned out to be a

hydrogen test (much bigger bang) and got too close.

Here it is today all fixed.

 

post-50896-0-80842900-1437788603_thumb.jpg


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#29 apfever

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Posted 09 October 2022 - 01:56 PM

Whoa! What happened?

The gyroscopic tesseract guide was removed from Who's Tardis. It was spun up (correctly) in the crux between two torodial spaces. However, being outside the Tardis allowed the tesseract to expand from it's differential size to a measurable amount. The resulting compaction caused a spacial rift to propogate, kind of like a photon arrow with a super long probability density. The path was directly into Roberts scope. That scope saved the universe. 

 

oh poop. you got in front of me while I was typing. I like mine better. 


Edited by apfever, 09 October 2022 - 02:09 PM.

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#30 tim53

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Posted 10 October 2022 - 08:08 AM

This story is interesting...  scroll down to the "vandalism damage" heading:  https://en.wikipedia... Primary Mirror.

 

-Tim.



#31 jragsdale

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Posted 10 October 2022 - 08:26 AM

This story is interesting...  scroll down to the "vandalism damage" heading:  https://en.wikipedia... Primary Mirror.

 

-Tim.

Great story!

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#32 jragsdale

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Posted 04 November 2022 - 07:56 PM

Getting into this project a little bit more today. Took apart the lens to get measurements and give it a good cleaning inside and out. Lots of dust/rust so wanted to get a fresh start on everything. Here's some details on the lens:

 

Crown: 0.45" thick (edge), 3.4kg, 10.5" OD

Metal air gap spacer: 3/32" thick, 1/8" wide

Flint: 1.04" thick (edge), 4.3kg, 10.5" OD

The chip is on the flint on the inside surface. No loose glass or anything inside, chip is "contained" in the glass.

 

Surprised to find out it's a 10.5" lens with a 10.25" clear aperture!



#33 jragsdale

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Posted 05 November 2022 - 08:21 PM

I have a friend with a large optical flat who offered his services to DPAC this big ol' lens for me. Here is the resulting figure in green. Interesting to see how the chip affects the figure in areas near it but it doesn't influence the whole figure too much, this is good to know if the plan is to use an aperture mask! Overall good figure, noticeable color separation as expected, a zone on the outer 10%, but I'm happy with these results!

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#34 davidc135

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Posted 06 November 2022 - 03:15 PM

Most of the edge effects are probably due to test diffraction. A Ronchi on the other side of focus would show, also a Foucault ke test.

 

David


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#35 jragsdale

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Posted 26 December 2022 - 01:24 PM

I found an original tube badge from another one of these refractors. Which led me to this PDF, pages 9-13, which talk a lot more about the Thompson Optical Navy refractors and what they were used for and how they were made. Nice to have some history on these now! 

 

https://www.umpqua.e...og-031616-2.pdf

 

"This telescope was designed to photograph Navy and Air Force parachute tests at NAF El Centro."

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#36 jragsdale

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Posted 23 February 2023 - 01:46 PM

Sorry for the lack of updates on this project. I haven't done much! I ended up getting a big 24" dovetail with some 12.7" ID parallax rings and upgraded my CGE to a CGE Pro. Here it is all mounted up.

 

But in the meantime, I actually tracked down and acquired a SECOND 10" f/10 Thompson Optical Refractor, this one is in excellent condition, tube, lens, baffles and all! Just need to trim the tube down to allow a focuser with diagonal, there is essentially zero backfocus with the tube as is. And I'm on the search for a heavier mount, the CGE Pro, even at 90lb capacity, just isn't going to cut it.

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Edited by jragsdale, 23 February 2023 - 01:47 PM.

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#37 clamchip

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Posted 23 February 2023 - 02:25 PM

I would be tempted to build a Berry mount for it.

But what you have there might be good enough to see what you have in the optics.

I'm in the middle of a similar project with a unknown 8 inch f/6 mirror, I'm temporarily using another

tube to see what I have. If I like it I'll give it a structure and mount to match its performance.

 

Robert 


Edited by clamchip, 23 February 2023 - 02:48 PM.

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#38 CHASLX200

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Posted 23 February 2023 - 07:12 PM

Sorry for the lack of updates on this project. I haven't done much! I ended up getting a big 24" dovetail with some 12.7" ID parallax rings and upgraded my CGE to a CGE Pro. Here it is all mounted up.

 

But in the meantime, I actually tracked down and acquired a SECOND 10" f/10 Thompson Optical Refractor, this one is in excellent condition, tube, lens, baffles and all! Just need to trim the tube down to allow a focuser with diagonal, there is essentially zero backfocus with the tube as is. And I'm on the search for a heavier mount, the CGE Pro, even at 90lb capacity, just isn't going to cut it.

Need a AP1600 for the cost of a car. Or look for a old 2.5" shaft Cave mount and make a pier. No normal mount will be big enough.



#39 jragsdale

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Posted 23 February 2023 - 07:48 PM

Need a AP1600 for the cost of a car. Or look for a old 2.5" shaft Cave mount and make a pier. No normal mount will be big enough.

Yeah, I've got my eyes peeled. AP1100/1200/1600. Byers Series II, Schaefer AT-9, Parks/Cave Observatory mounts, Parallax HD150, Mountain Instruments (Mathis) MI-500, etc. Someone offered me a heavy duty ATM that's actually too big, like 1000lb capacity, kind of intriguing though.



#40 ccwemyss

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Posted 23 February 2023 - 09:12 PM

There's a Byers 812 on AM currently. Not as beefy as a Series II, but still pretty strong. 

 

https://astromart.co...al-mount-558273

 

Chip W. 


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#41 jragsdale

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Posted 24 February 2023 - 10:04 AM

Well, the universe once again finds a way, after casting a wide net, the absolute PERFECT mount of my dreams has fallen into my lap. An UNUSED Schaefer AT-12 with an extra long saddle and a 5 foot x 10" portable pier. And it's relatively nearby so I can pick it up. This mount should be able to carry 2 of my 10" refractors it's so beefy. And I'm an absolute Schaefer fanboy, so this is a dream come true for me!

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#42 39cross

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Posted 24 February 2023 - 05:54 PM

You're going to have to start offering tours, what a collection!
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#43 CHASLX200

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Posted 24 February 2023 - 07:15 PM

Never saw one of them mounts and don't think one has even been within 200 miles of me.  Not sure how big or heavy it is. They are on my want list if one ever pops up local.



#44 RichA

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Posted 24 February 2023 - 07:22 PM

Sorry for the lack of updates on this project. I haven't done much! I ended up getting a big 24" dovetail with some 12.7" ID parallax rings and upgraded my CGE to a CGE Pro. Here it is all mounted up.

 

But in the meantime, I actually tracked down and acquired a SECOND 10" f/10 Thompson Optical Refractor, this one is in excellent condition, tube, lens, baffles and all! Just need to trim the tube down to allow a focuser with diagonal, there is essentially zero backfocus with the tube as is. And I'm on the search for a heavier mount, the CGE Pro, even at 90lb capacity, just isn't going to cut it.

I wonder if it would be better optically to use a smooth arc to screen off the chip, which would avoid sharp-edge diffractive effects?



#45 Kasmos

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Posted 27 February 2023 - 02:22 AM

A second Thompson and a second Schaefer. What was that nick.... never mind.

 

For some reason I'm craving Swiss Cheese. scratchhead2.gif


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#46 apfever

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Posted 27 February 2023 - 08:33 AM

I see lots of dust, a rusty allen bolt, and what appears to be a rusty slo mo shaft with the knobs. What a piece of crud. I'm enjoying resto work now even more than viewing, but if you pay shipping both ways I'd do a nut and bolt job on it and use it just enough to check it out for maybe ONLY Just a year or so?  Maybe you have to much project to get to it? If the socio-economic structure crushes by then and it can't be shipped back, then you are welcome to visit and pick it up.

 

How have you been running into this stuff? I just picked up a rare O.C. 6" rich field, Meade Starfinder GEM 6" F8, box of good goodies including a few TV, an extra 6" F8 mirror in unused condition that I seriously needed for the Edmund project, and more in one package deal. Then the nice lady wanted to start giving me things because I was the right person to be able to do the right thing with it. That's when I had to balk and talk first. She wasn't hurting by any means (apparently) and now I'm obliged to try and get her to take some money back (more than the original package cost). Maybe I can send her a hundred dollar bill in the mail. That puts the burden of acceptance on her. I accepted burden and obligation from her while there. It's nice to find people not tight to the fence but need to keep it from turning into a Chip n Dale Chipmunk thing. 

 

Maybe this is all because I started giving things away to schools and kids. I need a break. Time to be stingy. What's your excuse, Mr. Big Finds?


Edited by apfever, 27 February 2023 - 08:38 AM.

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#47 apfever

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Posted 27 February 2023 - 08:52 AM

I wonder if it would be better optically to use a smooth arc to screen off the chip, which would avoid sharp-edge diffractive effects?

I agree. See entry #15 in this string, first page. I like a nice general curve but I don't like to cusp into the primary edge like an eclipse on big problems. That's where the 'eye liner' type flare comes in at the edge. Keep it all smooth and curvy. 

 

The DPAC looks surprisingly good, even close around the top part. The bottom of the chip seems to have moved a little desirable DPAC line. Entry #33 above.


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#48 jragsdale

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Posted 27 February 2023 - 11:18 AM

I see lots of dust, a rusty allen bolt, and what appears to be a rusty slo mo shaft with the knobs.

 

How have you been running into this stuff?

Yeah, it needs a mild restore, new bolts, clean and lube. But I'm getting a deal on because of that.

 

This one I found by knowing the right person to ask, "Hey, got anything big enough to hold a 10" f/10 refractor sitting around in your garage?"


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#49 jragsdale

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Posted 27 February 2023 - 02:56 PM

For some reason I'm craving Swiss Cheese. scratchhead2.gif

Maybe the previous owner was going for a poor-man's Great Melbourne Telescope? lol.gif lol.gif

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#50 clamchip

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Posted 27 February 2023 - 06:12 PM

I've seem that lattice tube construction before and is not a bad idea these days with irrigation pipe

what it is, or I should say what the shipping costs arefrown.gif

The lattice can be done with aluminum strips, and pop rivet it all together, very easy to dolaugh.gif

 

Robert 


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