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Boller & Chivens retirement

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#51 starman876

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Posted 01 April 2021 - 04:35 PM

Also, my friend tells me the B&C is f/18.

got to love those long focal lengths cassegrains.



#52 gnabgib

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Posted 01 April 2021 - 05:25 PM

Jeff;

       Sent you a PM about the telescope.

 

Kevin



#53 bierbelly

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Posted 01 April 2021 - 05:33 PM

Tim, what a beauty. The sit down position looks good. As a retiree on fix income it is quite out of my budget cool.gif Your cass is also a beauty.

Cash out refi and its yours!
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#54 CHASLX200

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Posted 01 April 2021 - 06:23 PM

Back in ancient times I made a 12.5” f/16 Classical Cass with a 3.5” secondary.  Images were fairly good but the contrast suffered a bit so I asked our local optician to make a smaller secondary and longer efl, so he polished me a 1.97” f/30 mirror and the images were very good.  Maybe using larger eyepieces helped.  Unfortunately a few years later I sent the primary off for a new coat and it was ruined so that scope was let go.

 

The UH24 was a 24" f/75 Boller & Chivens we used on Mauna Kea for photographing Mars and visually was very good.  I am sure if we had electronic cameras like are used today it would have produced excellent images, especially up on that huge volcano.

Yikes at F/75. Even a 55mm eyepiece would be crazy power. Gonna need a good finder.



#55 Jeff B1

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Posted 01 April 2021 - 06:29 PM

Yikes at F/75. Even a 55mm eyepiece would be crazy power. Gonna need a good finder.

The Lowell Planetary Patrol had access to these slooooow casses:

 

Mauna Kea Observatory, Hawaii: 24-inch, F/75 Boller and Chives Cassegrain
Republic Observatory, Johannesburg, South Africa: 20-inch, Boller and Chivens Cassegrain
Cerro Tololo Interamerican Observatory, Chile: 24-inch, F/75 Boller and Chivens Cassegrain
Magdalena Peak Station, New Mexico: 24-inch, F/75 Boller and Chivens Cassegrain
Lowell Observatory, Flagstaff, AZ: 24", F/75 Morgan Cassegrain

 

The f/75 was Clyde Tombaugh's idea.


Edited by Jeff B1, 01 April 2021 - 06:30 PM.

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#56 Jeff B1

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Posted 01 April 2021 - 06:31 PM

Cash out refi and its yours!

Not interested.



#57 CHASLX200

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Posted 01 April 2021 - 06:34 PM

The Lowell Planetary Patrol had access to these slooooow casses:

 

Mauna Kea Observatory, Hawaii: 24-inch, F/75 Boller and Chives Cassegrain
Republic Observatory, Johannesburg, South Africa: 20-inch, Boller and Chivens Cassegrain
Cerro Tololo Interamerican Observatory, Chile: 24-inch, F/75 Boller and Chivens Cassegrain
Magdalena Peak Station, New Mexico: 24-inch, F/75 Boller and Chivens Cassegrain
Lowell Observatory, Flagstaff, AZ: 24", F/75 Morgan Cassegrain

 

The f/75 was Clyde Tombaugh's idea.

I don't know how you could ever center a object at that slow speed.



#58 starman876

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Posted 01 April 2021 - 07:25 PM

I don't know how you could ever center a object at that slow speed.

professional mechanics is how.  no hand guiding with those scopes.


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#59 Jeff B1

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Posted 02 April 2021 - 05:31 AM

Never a problem.  The UH24 had a 55mm eyepiece and a 3" refractor on the side that was aliened okay.



#60 Terra Nova

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Posted 02 April 2021 - 07:31 AM

The B&C 16" is a cassegrain, not a cat.

Aren’t all forms of CAssegrain Telescopes CATs? It seems to me that CAT is an inclusive acronym for SCTs, Maks, CCs, RCs, DKs, etc.



#61 starman876

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Posted 02 April 2021 - 08:03 AM

Aren’t all forms of CAssegrain Telescopes CATs? It seems to me that CAT is an inclusive acronym for SCTs, Maks, CCs, RCs, DKs, etc.

Not really.  CAT is abbreviation for Catadioptric. These designs always have a lot more  glass than a simple cassegrain.    RC's, DK's are a different form of cassegrain using only mirrors.  The minute corrector lenses, Meniscus, schmidt correctors and such are used we now are in the Catadioptric line of scopes or CAT's.

 

look at the description in the Cats and Casses forum

 

Cats & Casses
A forum for discussing Cassegrain (Classic Cassegrain, Ritchey-Chrétien, Dall–Kirkham, etc) and Catadioptric telescopes (Schmidt and Maksutov Cassegrains, ACF, Edge HD, etc


Edited by starman876, 02 April 2021 - 08:10 AM.

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#62 tim53

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Posted 02 April 2021 - 08:06 AM

Nope, not if they don't have refractive elements needed to form an image.  I suppose technically a CDK could be considered a cat, but probably not since DKs exist without corrective lenses in their baffle tubes.  SCTs, Maks, and things like Klevtsovs, Vixen VMCs and mirror lenses are cats because they need the refractive elements to form images.


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#63 starman876

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Posted 02 April 2021 - 08:10 AM

Nope, not if they don't have refractive elements needed to form an image.  I suppose technically a CDK could be considered a cat, but probably not since DKs exist without corrective lenses in their baffle tubes.  SCTs, Maks, and things like Klevtsovs, Vixen VMCs and mirror lenses are cats because they need the refractive elements to form images.

we are in complete agreement waytogo.gif


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#64 starman876

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Posted 02 April 2021 - 08:13 AM

Never a problem.  The UH24 had a 55mm eyepiece and a 3" refractor on the side that was aliened okay.

a good finder scope properly aligned is an absolute must on a long focal length scope.  My cassegrain is an F20. without a finder scope I would spend a long time setting up on an object.  even the F15 scopes without a finder would make it very hard to locate object. 



#65 tim53

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Posted 02 April 2021 - 08:18 AM

My f/23 Cass didn't have a finder for about a year.  I didn't want to drill holes in the teak plywood tube and mar it's uninterrupted gorgeousity.  I would site along the corner of the nonogon to find planets (all I was observing initially) and center in a 28mm RKE.  Wasn't that hard, actually.  Flat-sided tubes, especiallly shiny ones, make great finders in their own right.  if you site up the flat side close to coplanar with the surface, you can see your target reflected in the finish.  adjust mount slow motions to bring the planet and its reflection together, and you've got one axis aligned.  Move to a perpendicular facet and repeat for the other axis.  In reality, it's a little more involved than this, but you get the idea.

 

For about another 2 years, all I had was a telrad for a finder.  These days, I use the FC-76.


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#66 tim53

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Posted 02 April 2021 - 08:19 AM

sight.  Sheez.  Mars time has me all goofed up.



#67 starman876

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Posted 02 April 2021 - 08:20 AM

My f/23 Cass didn't have a finder for about a year.  I didn't want to drill holes in the teak plywood tube and mar it's uninterrupted gorgeousity.  I would site along the corner of the nonogon to find planets (all I was observing initially) and center in a 28mm RKE.  Wasn't that hard, actually.  Flat-sided tubes, especiallly shiny ones, make great finders in their own right.  if you site up the flat side close to coplanar with the surface, you can see your target reflected in the finish.  adjust mount slow motions to bring the planet and its reflection together, and you've got one axis aligned.  Move to a perpendicular facet and repeat for the other axis.  In reality, it's a little more involved than this, but you get the idea.

 

For about another 2 years, all I had was a telrad for a finder.  These days, I use the FC-76.

not all of us have flat sided tubesgramps.gif



#68 Terra Nova

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Posted 02 April 2021 - 08:27 AM

Not really.  CAT is abbreviation for Catadioptric. These designs always have a lot more  glass than a simple cassegrain.    RC's, DK's are a different form of cassegrain using only mirrors.  The minute corrector lenses, Meniscus, schmidt correctors and such are used we now are in the Catadioptric line of scopes or CAT's.

 

look at the description in the Cats and Casses forum

 

Cats & Casses
A forum for discussing Cassegrain (Classic Cassegrain, Ritchey-Chrétien, Dall–Kirkham, etc) and Catadioptric telescopes (Schmidt and Maksutov Cassegrains, ACF, Edge HD, etc

Thank you for clarifying that J! That makes perfect sense! Catadioptric! waytogo.gif 


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#69 Jeff B1

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Posted 02 April 2021 - 09:01 AM

sometimes finding an object without an eyepiece is easy.  I usually did not use a star diagonal in my Cass so looking trough the focuser one can align a bright planet up fairly close to center.   Those few 24" f/75 Cass scope I used had the ever present 3" brass refractor mounted on the tube that was close enough for government work.  

 

If I used my 12.5" f/30 for a DSO, bright nebula or something, then I had setting circles that would get me close enough for hunt an peck.  



#70 555aaa

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Posted 02 April 2021 - 10:07 AM

The larger versions of this mount used DC torque motors to provide preload. I don’t know if the 16 did. These are designed to carry a couple hundred pounds of instrumentation. Some had an option for Coude’ focus to a spectrograph under the telescope (the UW telescope has this but they never built the spectrograph for it. )

Edited by 555aaa, 02 April 2021 - 10:10 AM.


#71 MassiveRedTelescope

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Posted 03 April 2021 - 08:54 AM

I've contacted DFM to see if I can get any docs on Berea's 16" B&C.

 

Many thanks to Kevin for his insights!



#72 Terra Nova

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Posted 03 April 2021 - 11:22 AM

... in the college where I went for my undergraduate education, we had an interim program between fall and spring semesters that ran four weeks, five days a week six hours a day. Everyone was required to take interim and you could only take one course. We had a course called Electronics for Scientists that I took one interim. It was great. Some theory but lots of practical training for maintaining instruments, cobbling things together, etc. We learned to use an oscilloscope, test circuits, put together simple boards, solder, etc.

Look what I just found! It’s still a useful reference for working on older equipment. This is the 1963 edition which was several years old when I had the class. Textbooks stayed in print much longer back then. Now the textbook publishers are constantly renumbering pages and adding pictures just to put out a new edition every year or two in a greedy attempt to circumvent the used book market.

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#73 rcwolpert

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Posted 03 April 2021 - 07:20 PM

Look what I just found! It’s still a useful reference for working on older equipment. This is the 1963 edition which was several years old when I had the class. Textbooks stayed in print much longer back then. Now the textbook publishers are constantly renumbering pages and adding pictures just to put out a new edition every year or two in a greedy attempt to circumvent the used book market.

I had that same book my first semester at Case in 1967! I believe the cover was a dark blue with that same design.


Edited by rcwolpert, 03 April 2021 - 07:23 PM.

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#74 Peter Ceravolo

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Posted 03 April 2021 - 09:19 PM

Nope, not if they don't have refractive elements needed to form an image.  I suppose technically a CDK could be considered a cat, but probably not since DKs exist without corrective lenses in their baffle tubes.  SCTs, Maks, and things like Klevtsovs, Vixen VMCs and mirror lenses are cats because they need the refractive elements to form images.

The CDK is a true catadioptric system because the mirrors alone in such a system will not form an image. You need the field correctors in order for the telescope to work at all. And the field correctors will be specific to the system they are designed for, they are not interchangeable with any other CDK, or DK for that matter.

 

In order to simultaneously flatten the field, correct coma and astigmatism you have to introduce spherical aberration into the mirror system that balances out the unavoidable spherical aberration introduced by the field corrector group.

 

Back to the topic of this thread, these old telescopes usually use Classical Casegrain optics of slow focal ratio, f/15 or slower. There is not much to be gained by making the Cass system a Ritchey-Chretien since the field of view is relatively small.


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#75 RichA

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Posted 03 April 2021 - 09:48 PM

Did it have a soft view?  I have yet to see a Cat really knock my socks off other than a very few SCT's that were way above the normal soft views.
 

Most people mistake a large scope's inability to provide good images in modest seeing as "softness."  Or, the scope just never cooled down.  I looked through a professional 24 inch at Vega once.  It was a disaster, all because of seeing.  In the average location (not Florida) a scope of that size maybe sees 3 nights a year where it can reach its diffraction-limit.


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