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12" find and manufacturer of a 10" F5.6 ?

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#1 Tom Stock

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Posted 23 April 2025 - 01:29 PM

Today I rescued an Orion XT12i (F5) in awful shape, missing parts, coating 50%. 

 

I would guess it's from around 2012 because it's the first release of the hand controller.

 

I'll chemically silver the mirror and ultimately it will end up on my Star Liner mount.

 

Now the interesting part is that the seller had a pile of "extras" to go with it, and one of those things was a 10" F5.6 mirror.

 

He didn't remember the source, but it's a full thickness blank and the coating was reasonably good. 

 

The only markings are 55.9", and some casting marks on the pyrex blank.

 

My GUESS is that it is amateur made, so it MIGHT actually be pretty good. Most people don't give up figuring a 12" unless it's at least acceptable because of the amount of work involved.

 

But, does anyone know if any of the telescope manufacturers sold a 10" F5.6 in the past?

 

It's an F ratio I've always wanted for a 10.

 

Thanks

Tom


Edited by Tom Stock, 23 April 2025 - 01:29 PM.


#2 Augustus

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Posted 23 April 2025 - 01:35 PM

Coulter made some 10" f/5.6 that were good


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#3 ngc7319_20

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Posted 23 April 2025 - 01:36 PM

Dick Wessling, a mirror maker in Cincinnati, OH years ago preferred to make F/5.6.  But he would have signed it.



#4 Jon Isaacs

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Posted 23 April 2025 - 01:45 PM

Discovery sold a 10 inch F/5.6 as part of their DHQ line. The DHQs had particle board bases and such, the PDHQ line was 10 inch F/6 with plywood bases etc.

 

Jon


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#5 Jethro7

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Posted 23 April 2025 - 03:07 PM

Hello Tom Stock,

In relation to Jon's post. if the mirror was sold by Discovery Dobs. the mirror could have been made by Terry Ostahowski. I have an old early to middle 2000's 12.5" Discovery Dob when Terri, was partners with Discovery Dobs. Terry did not sign his mirrors. The only mark is the focal length in inches written in what looks like a sharpie pen was used.

 

HAPPY SKIES AND KEEP LOOKING UP Jethro


Edited by Jethro7, 23 April 2025 - 03:11 PM.


#6 Tom Stock

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Posted 23 April 2025 - 03:10 PM

Ok more leads than I expected. Ok, I looked again, it's 1.75" thick which makes me think pre-1995.

 

No other markings than the focal length on the side.  It's fully polished out no grayness at the edge which is a good sign.

 

Were Coulter mirrors this thick? I'll foucault test it when I get some free time.

 

Thank you!

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Edited by Tom Stock, 23 April 2025 - 03:37 PM.


#7 apfever

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Posted 23 April 2025 - 04:05 PM

I might essentially have this mirror.  It is a 10" F5.59 with the number 55.9 etched on the side exactly like the one pictured. There are no other markings. The casting looks to be the same style. Mine is 1.75" thick. If they were place side by side, I think the general consensus would be that they are the same make and time frame.  Anything remains possible. Mine came out of A Girl's Dob. smile.png

The cell is unique so far. I have seen similar but nothing definitive to match my cell. The scope was made for her by a friend that had made other similar dobs. I believe her 'friend' was an atm/side line type of production maker.  It would be a tough trace but the scope might be identifiable considering the group in this forum. I think I've posted the scope in this forum but not sure. Searches are very arduous for me but I'll look around.  


Edited by apfever, 23 April 2025 - 04:20 PM.


#8 apfever

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Posted 23 April 2025 - 04:39 PM

OK, I have about 50 pictures of the whole scope on my comp, including the original ad for a "dubsonian".   I bought it about 8 months ago. The cell rather sucked so I did a tear down and figured out all the fixes, but then lost interest and never put it back together.  Here is a picture showing the mirror and side etch. I'll offer any help I can. 

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#9 apfever

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Posted 23 April 2025 - 04:44 PM

Your guess is as good as mine.  My mirror/cell is currently out and in the basement. I can get to it.

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Edited by apfever, 23 April 2025 - 04:48 PM.


#10 Tom Stock

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Posted 23 April 2025 - 05:06 PM

apfever that is fascinating! How did it perform? Do you know where this mirror maker was located?

I am in shock that you have an exact match for this mirror. I never expected that!

Now the question is did the ATM friend make this mirror (seems unlikely if they are identical) or are they from a coulter or other mass produced scope originally?

Edited by Tom Stock, 23 April 2025 - 05:11 PM.


#11 apfever

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Posted 23 April 2025 - 10:18 PM

Okayyyy.  The lady that it was made for had it for a few years. I believe the whole dob might be between 5 or 10 years old, maybe less, can't be certain. I do recognize older school parts, including the basic nature of the cast primary. Apparently the lady's friend had all kinds of scope parts for a rather long time doing this stuff as a side line. The lady was in school for astronomy, physics, engineering, ....and such. Her boyfriend was college age. She recently graduated and became a certified Astrophysicist. She and her boyfriend split up cordially. Her boyfriend had just bought her a new full Celestron CAT set up just before they split up. She took the secondary glass out of the spider and left the rest of the complete dob behind. Her boyfriend asked her about the carcass and she said he could just sell it or...whatever.  He put it up for $100 miss labeled as an 8".   It was miss labeled by size since he was going by pure estimate, he was a fairly casual poster. I corrected him on the size so he could change the ad for a while. I am why he changed the ad and stated both the primary size and upper cage size. I wasn't out to take advantage of him.  By then I had my foot in the door and his responses still weren't great so I got it.  Everything about meeting the boyfriend, the location, the situation, his story, other stuff there, it all matched up and felt right.  Now I'm feeling I did post this scope in the Classics forum earlier somewhere, probably a little different story if I did but I'm doing the best I can. 

 

My computer date on the original ad screen shot is Aug. 2024. That might have changed as I used the picture, not sure how that end works. I don't think I've had if for a year. I'm positive the mirror is older school appropriate for this forum. I've seen a LOT of old school primaries and this rings too strongly that way, always did, along with other major scope parts. The dob in turn has newer brackets and such in the construction. 

 

I think were both in the same limbo boat with a vintage production mirror from the same source. Ain't that the 'pile'!   Apparently the lady adored the dob, and was still local. I always thought she would come out of the woodwork if I posted the finish scope with my hindsight type rebuilds, and got it public through some astronomy venues (like CN).   I took all my pictures when I got the scope, and they are all Aug. 2024 so that is probably about when I got it.  Here is the screen shot of the original ad, and at my place.  I also engineered and built that custom Nashbar in the background, a lot of fun with no gear fear on length. It's triple cored with sleeved aircraft tubing. 

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Edited by apfever, 23 April 2025 - 10:23 PM.


#12 Tom Stock

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Posted 23 April 2025 - 10:24 PM

apfever thanks for the info. That is a very interesting story, and a really interesting build.

 

I'm betting these are Coulter F5.6 mirrors, and the girl ex BF spelled Dobsonian wrong when trying to sell the thing (and the size).


Edited by Tom Stock, 23 April 2025 - 10:28 PM.


#13 apfever

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Posted 23 April 2025 - 10:33 PM

A girls dob, cute, compact, light build.  If anybody recognizes the build, we're GOLDEN for primary I.D. 

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Edited by apfever, 23 April 2025 - 10:35 PM.


#14 apfever

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Posted 23 April 2025 - 10:49 PM

HA!  I did the same build on this one as I did the recent Edmund SC resto I've been posting today.  This is the same cell as above from the Girl's Dob.  

 

Secondary assembly as bought with removed glass. 

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#15 apfever

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Posted 23 April 2025 - 10:56 PM

I'll stop here, pm request or for post here,  still about 40 or so pictures, lots of bits and pieces of rebuild work like the cell above. Several more of the entire set up.  Your call. 

Everything posted here is reduced size and/or quality to get under the size requirement. 

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Edited by apfever, 23 April 2025 - 10:58 PM.


#16 clamchip

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Posted 23 April 2025 - 11:11 PM

Here's another 5.6 10 inch and 2.14"  diagonal I'm pretty positive is Coulter.

It came in a rather interesting structure (middle photo).

And I have another one engraved the same way, that's in my Smorgasbord (bottom two photos).

Robert

 

post-50896-0-99304500-1604770875_thumb.jpg

post-50896-0-28729100-1604787159.jpg

post-50896-0-71383300-1451790392_thumb.jpg

post-50896-0-57075000-1726719834.jpg


Edited by clamchip, 23 April 2025 - 11:25 PM.

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#17 Tom Stock

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Posted 23 April 2025 - 11:28 PM

A girls dob, cute, compact, light build.  If anybody recognizes the build, we're GOLDEN for primary I.D. 

It is cute with all the girly cat stickers



#18 Tom Stock

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Posted 23 April 2025 - 11:29 PM

Here's another 5.6 10 inch and 2.14"  diagonal I'm pretty positive is Coulter.

It came in a rather interesting structure (middle photo).

And I have another one engraved the same way, that's in my Smorgasbord (bottom two photos).

Robert

 

attachicon.gif post-50896-0-99304500-1604770875_thumb.jpg

attachicon.gif post-50896-0-28729100-1604787159.jpg

attachicon.gif post-50896-0-71383300-1451790392_thumb.jpg

attachicon.gif post-50896-0-57075000-1726719834.jpg

What a strange mount. 

 

Thanks for the details I'm leaning towards a coulter because of the similar engraving location and size. They also seem the prime candidates for being transplanted.


Edited by Tom Stock, 23 April 2025 - 11:31 PM.


#19 clamchip

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Posted 23 April 2025 - 11:31 PM

What a strange mount. 

It sure is.

I bet the people who didn't see the road closed sign sure were surprised!

Robert



#20 CHASLX200

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Posted 24 April 2025 - 05:46 AM

Ok more leads than I expected. Ok, I looked again, it's 1.75" thick which makes me think pre-1995.

 

No other markings than the focal length on the side.  It's fully polished out no grayness at the edge which is a good sign.

 

Were Coulter mirrors this thick? I'll foucault test it when I get some free time.

 

Thank you!

The older blanks were thicker.



#21 Tom Stock

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Posted 24 April 2025 - 11:51 AM

It sure is.

I bet the people who didn't see the road closed sign sure were surprised!

Robert

I bet the person who tripped over that rod sticking out of it was also surprised!



#22 Sean Cunneen

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Posted 24 April 2025 - 12:14 PM

I am moving this thread to reflectors as these scopes are not old enough to be classics just yet...



#23 Senex Bibax

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Posted 25 April 2025 - 07:59 AM

It is cute with all the girly cat stickers

Not as cute as Robert's daredevil teddy about to be shot out of that yard cannon



#24 harpo80

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Posted 26 April 2025 - 05:45 AM

Tom, that looks like a Coulter I put in the first Dob I built back in the mid-late 1980s; it was thick and had that number engraved on it.  It being the same one I had is unlikely, although that Meade focuser is exactly the one I bought for it, and the primary mount (Parks I think?) resembles it too, so the possibility is intriguing.  I sold the mirror and parts, minus wood and Sonotube, when we moved east in the early 2000s and I was seduced by a 10" LX200.

 

Lots of Herschels and doubles put light on my mirror - was a great scope that I wish I'd kept.

 

 

10%22 Dob 2.jpeg


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#25 icomet

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Posted 01 May 2025 - 02:56 PM

I just sold my 1993 Nova/Swayze  10" f/6 @ 1.75" thickness.

 

Clear Skies. 




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