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Who made the the biggest SCT ever? Celestron?

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#101 Jim Riffle

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Posted 23 August 2019 - 01:07 PM

Hello,

 

Yes, I did complete 2 each 24 1/2" f/6.2 SCTs way back when. They were designed by Mike Simmons for me.  They had a 7 1/2" diameter focal plane and one had an 8X10 film back astro-camera built for it with integral of-axis guider port.  The standard included cameras were my custom 4x5s w/off-axis guider port and a set of matched vacuum film holders.  I only took 4x5 film images during testing and they were sharp to the edge.   Still have the negatives.  Customer taken images have been in S&T.

 

The primary was a Zerodur sphere of 25 1/2" diameter.  The secondary was a 11" diameter Zerodur hyperbola (fairly strong) null figured by itself.  Focusing was via radio control movement of secondary mirror. There was a large 2 element corrector lens group between the primary mirror and the focal plane.  This design was complex since the Schmidt plate was 3/4" thick with a 7" hole and had 3 times the optical asphere of a typical f/10 SCT corrector.  Tom Scott was the finishing optician who did the difficult corrector null figuring on  both. To even get to a starting point he had to use his back pocket comb coarse bristle end as a Ronchi ruling to even see where to start on correction!  He tore out his hair working it for many months and wanted to give up (without pay) being only able to get to within 1 wave of correction at best.  His efforts to get closer erased the total correction.  Both customers were $3/4 in by then and the OTA/mounts machine work w/paint was just waiting on completed optics.  I offered Tom a sizable $ gift (either way) to leave or stay on it.  He agreed and I was then able to enlist Dave Dodgen (not to mixed up with son Rod) to walk him thru necessary Schmidt plate figuring technique over the phone.  With Dave's gracious help Tom then made new progress and null figured both optical systems to spec. with big smiles all around.

 

The only other opticians working on the glass for these 2 SCTs were Norm Cole, Brian Lizot and Joe Appels in that order. 

 

The original #1 customer came out one night to test his finally finished SCT at my place in White Rock (Los Alamos) N.M. Since the scope would not split Sirius for him that night, he wanted a refund!!!!  He was from Lebanon and, well he used me with this pawn.  Since I knew the real value of the instrument I agreed that same night to refund his $65K less a 20% fee.  He was fine with that since he wanted the funds for a Duncan Donut franchise down in ALBQ, NM.  My wife/partner was not so fine with that night.  His first name was Kamel.  Never saw him again after years leading up his canceling.

 

The next SCT went to Helena, Arkansas and the #1, I later sold to a previous customer up in Crestone, Co. with incredible sky.  He got a nice portfolio of color 4x5 film images with it.  Years later he upgraded my cast aluminum AstroWorks mount with a much more robust all steel GEQ that was said to be by it's maker "able to hold a Volkswagon" (beetle?...)  Just after transferring the 24inch OTA  onto the new mount, that mount separated (as in broke in two) at the RA/Dec junction.  The Schmidt plate and secondary shattered on the concrete floor and all that was left were the primary and 2 element lens corrector for the focal plane.  The mount maker later walked away on him, but luckily this customer's lawyer son got all over the home owners insurance company enough to where they finally paid out.  So #1 is dead.  As far as I know, #2 still lives on in Joplin, MO.

 

In almost 40 years of custom telescope making these 24 1/2" ers were a real test for me during the time.  Later on I had a similar experience with the three automated C28" f/3.2 prime focus CCD astrographs made.  Making all those one-of -kind new design telescopes sure kept me on my toes along with the 12" f/5 series Astromaks included in the mix!  Never easy stuff!  Not always easy customers.  Not always simple installations for me.  Lots and lots of stories though.  The all white scope is sn2   24 1/2" SCT.

 

Jim Riffle, retired telescope maker from ASTROWORKS

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  • 28.jpg

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#102 SandyHouTex

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Posted 25 August 2019 - 01:37 PM

Hello,

 

Yes, I did complete 2 each 24 1/2" f/6.2 SCTs way back when. They were designed by Mike Simmons for me.  They had a 7 1/2" diameter focal plane and one had an 8X10 film back astro-camera built for it with integral of-axis guider port.  The standard included cameras were my custom 4x5s w/off-axis guider port and a set of matched vacuum film holders.  I only took 4x5 film images during testing and they were sharp to the edge.   Still have the negatives.  Customer taken images have been in S&T.

 

The primary was a Zerodur sphere of 25 1/2" diameter.  The secondary was a 11" diameter Zerodur hyperbola (fairly strong) null figured by itself.  Focusing was via radio control movement of secondary mirror. There was a large 2 element corrector lens group between the primary mirror and the focal plane.  This design was complex since the Schmidt plate was 3/4" thick with a 7" hole and had 3 times the optical asphere of a typical f/10 SCT corrector.  Tom Scott was the finishing optician who did the difficult corrector null figuring on  both. To even get to a starting point he had to use his back pocket comb coarse bristle end as a Ronchi ruling to even see where to start on correction!  He tore out his hair working it for many months and wanted to give up (without pay) being only able to get to within 1 wave of correction at best.  His efforts to get closer erased the total correction.  Both customers were $3/4 in by then and the OTA/mounts machine work w/paint was just waiting on completed optics.  I offered Tom a sizable $ gift (either way) to leave or stay on it.  He agreed and I was then able to enlist Dave Dodgen (not to mixed up with son Rod) to walk him thru necessary Schmidt plate figuring technique over the phone.  With Dave's gracious help Tom then made new progress and null figured both optical systems to spec. with big smiles all around.

 

The only other opticians working on the glass for these 2 SCTs were Norm Cole, Brian Lizot and Joe Appels in that order. 

 

The original #1 customer came out one night to test his finally finished SCT at my place in White Rock (Los Alamos) N.M. Since the scope would not split Sirius for him that night, he wanted a refund!!!!  He was from Lebanon and, well he used me with this pawn.  Since I knew the real value of the instrument I agreed that same night to refund his $65K less a 20% fee.  He was fine with that since he wanted the funds for a Duncan Donut franchise down in ALBQ, NM.  My wife/partner was not so fine with that night.  His first name was Kamel.  Never saw him again after years leading up his canceling.

 

The next SCT went to Helena, Arkansas and the #1, I later sold to a previous customer up in Crestone, Co. with incredible sky.  He got a nice portfolio of color 4x5 film images with it.  Years later he upgraded my cast aluminum AstroWorks mount with a much more robust all steel GEQ that was said to be by it's maker "able to hold a Volkswagon" (beetle?...)  Just after transferring the 24inch OTA  onto the new mount, that mount separated (as in broke in two) at the RA/Dec junction.  The Schmidt plate and secondary shattered on the concrete floor and all that was left were the primary and 2 element lens corrector for the focal plane.  The mount maker later walked away on him, but luckily this customer's lawyer son got all over the home owners insurance company enough to where they finally paid out.  So #1 is dead.  As far as I know, #2 still lives on in Joplin, MO.

 

In almost 40 years of custom telescope making these 24 1/2" ers were a real test for me during the time.  Later on I had a similar experience with the three automated C28" f/3.2 prime focus CCD astrographs made.  Making all those one-of -kind new design telescopes sure kept me on my toes along with the 12" f/5 series Astromaks included in the mix!  Never easy stuff!  Not always easy customers.  Not always simple installations for me.  Lots and lots of stories though.  The all white scope is sn2   24 1/2" SCT.

 

Jim Riffle, retired telescope maker from ASTROWORKS

All I can say is WOW!!!



#103 luxo II

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Posted 27 August 2019 - 05:12 AM

SCT maybe .. but Schmidt telescopes no, there are much bigger examples.

But nonetheless quite an achievement. Sad to hear #1 didn’t survive such a basic error as having an EQ Mount part ways... that must have been heart wrenching.

A friend of mine who produces handmade travelscopes had one smashed in transit to a customer recently ... even though it was insured it was very dismaying.

Edited by luxo II, 27 August 2019 - 05:17 AM.


#104 Jim Riffle

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Posted 27 August 2019 - 10:58 AM

I hadn't talked to that Colorado #1 24 1/2" customer in a couple years prior to the "accident" or incident.  I did know that he was going to do a big mount upgrade before though.  Late when he telephoned to tell me what happened, for the first 2-3 minutes I thought it was a big joke and so I wasn't rattled till it sunk in.  After that,  lots of periodic head shaking for a week or so.  I still shake my head whenever it comes up.  Right now for example.  Arrrggg.  

 

But more of a shock to me was a mortician who ordered a 8" folded refractor  in 84 with the mount and rings all in satin black.  The OTA was white fiberglass with black ends.  Looked just like a Unitron ready to have triplets.  Sadly and bizarrely he shot himself (dead) while on the phone with one of my AstroMak customers, also in the area.  I don't think it had to do with his refractor.   It was a one-of-a-kind beauty and he was quite the character with a great sense of humor.

 

Then there was the AstroMak that went to a Kuwait science club.  The payment was a letter of credit that finally got paid just 4 weeks before Iraq invaded them.  They don't pay till the scope clears their dock and then customs.  That was close!  I imagine that telescope had a sad ending too.

 

Jim

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#105 SandyHouTex

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Posted 27 August 2019 - 09:42 PM

I hadn't talked to that Colorado #1 24 1/2" customer in a couple years prior to the "accident" or incident.  I did know that he was going to do a big mount upgrade before though.  Late when he telephoned to tell me what happened, for the first 2-3 minutes I thought it was a big joke and so I wasn't rattled till it sunk in.  After that,  lots of periodic head shaking for a week or so.  I still shake my head whenever it comes up.  Right now for example.  Arrrggg.  

 

But more of a shock to me was a mortician who ordered a 8" folded refractor  in 84 with the mount and rings all in satin black.  The OTA was white fiberglass with black ends.  Looked just like a Unitron ready to have triplets.  Sadly and bizarrely he shot himself (dead) while on the phone with one of my AstroMak customers, also in the area.  I don't think it had to do with his refractor.   It was a one-of-a-kind beauty and he was quite the character with a great sense of humor.

 

Then there was the AstroMak that went to a Kuwait science club.  The payment was a letter of credit that finally got paid just 4 weeks before Iraq invaded them.  They don't pay till the scope clears their dock and then customs.  That was close!  I imagine that telescope had a sad ending too.

 

Jim

What a shame.



#106 gsm026

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Posted 27 August 2019 - 11:35 PM

Here is the C22 at the Jefferson County Mount Evans Outdoor Lab School.  This is the scope owned by the Denver Museum of Nature & Science.  I used it as a high school intern in 1975 and did some 35mm photography through it.  At that time it still had the original SCT optics which were none too sharp.  

 

I got to use the scope again about 25 years later as part of a volunteer group that used the observatory for public star parties in the summer (when not being used by the school).  At that point it had been converted to an R-C cassegrain. The observatory still exists, not sure if the C22 is still there or not.

 

Greg

 

C22.JPG

__hr_4-6-02 C22.jpg

__hr_4-6-02 John Polhamus.jpg


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#107 JoeR

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Posted 31 August 2019 - 03:07 PM

Perkins Observatory in Delaware, OH houses a custom built 32" Cassegrain. The dome used to be home to the 69" Perkins Telescope that was moved to Lowell Observatory due to the poor sky conditions in Ohio (Don't I know it! frown.gif) The 32" is under Bortle 6 skies and can't show much now, plus its mirrors are in dire need of re-coating.

32-inch-scope.jpg


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#108 cam1936

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Posted 05 September 2019 - 09:20 AM

Love the stories Jim, even if some have sad endings.

#109 mitsos68

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Posted 11 September 2019 - 06:28 AM

And this is interesting

 

https://www-history....Cassegrain.html

 

https://en.wikipedia...egory_Telescope


Edited by mitsos68, 11 September 2019 - 06:31 AM.


#110 Jim Riffle

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Posted 13 September 2019 - 01:35 PM

Yes, your link to the St Andrews SCT in Scotland does show it to be a 37" Concentric Schmidt Cassegrain.  With the Schmidt corrector out at the radius of curvature of the primary, it is a beast!  Looks like it has secondary mirror focusing and a large adjustable aperture iris per attached drawing.  Wonder how many clear nights it gets?

 

Jim Riffle

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#111 RalphMeisterTigerMan

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Posted 18 September 2019 - 12:27 PM

Probably the only way to find any of the vintage C22 SCT's, other than getting in touch with someone who knows where one is, would to be to take a massive road trip and visit as many older Universities and Colleges large enough to offer an Astronomy Program. Then at the administration office see if they will allow you to go through their old records having to do with the afore mentioned Astronomy programs and if there was an Observatory on the college grounds.

 

The sad part is, many of these venerable scopes were replaced with something more modern. I have read stories of these great scopes ending up being dismantled and ending up gathering dust in some long forgotten basement, probably in an unused building.

 

Sure,it sounds like a lot of travel and leg work but if you happen upon one of these old beauties, the heads of that particular college might be happy to get rid of said gem and sell it to you for a song or even let you have it for free as long as you have a big enough truck and enough strong bodies to help carry it so that heads of the College won't have to lift or have anything to do with the removal. 

 

Chances are they wouldn't even be aware of the price of such a scope once it has been cleaned up and refurbished. Sadly, they probably just consider it "junk" and good riddance to bad rubbish. You never know until you try.

 

 Good luck to anyone who tries it.

RalphMeisterTigerMan




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