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Vintage ATM Maksutov

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#26 Mr Magoo

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Posted 19 September 2021 - 06:33 PM

I'm not sure how old this Brandon is. I believe I had on of these years ago and gave it to a friend. If memory serves me correctly, I believe it was a Kellner in design. 

 

IMG_2579.JPG


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#27 Marc-Andre

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Posted 19 September 2021 - 06:36 PM

The RA motor is missing. The brass gear is interesting to me in that it is actually two separate sheets cut to make one gear. I can not understand why it is made this way and what is up with the springs. I'm sure one of you will know why it is made this way. I have an old Cramer 1/15 rpm (4 rph) motor from another mount and the mounting hole spacing and distance to the shaft centerline matches exactly with what is on this mounting bracket. The shaft on the motor I have is way too long and I really don't want to cut it down for this so I will be looking for another motor for this mount. The worm block has some extra holes and looks like it may have been repurposed from another mount. 

 

attachicon.gifIMG_2565.JPG

I forget where I got it, but I had a similar split gear with internal springs years ago.  I conclude that it was designed to reduce play by maintaining constant contact with lead and trailing gear teeth of the worm gear.


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#28 davidc135

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Posted 19 September 2021 - 06:36 PM

The RA motor is missing. The brass gear is interesting to me in that it is actually two separate sheets cut to make one gear. I can not understand why it is made this way and what is up with the springs. I'm sure one of you will know why it is made this way. I have an old Cramer 1/15 rpm (4 rph) motor from another mount and the mounting hole spacing and distance to the shaft centerline matches exactly with what is on this mounting bracket. The shaft on the motor I have is way too long and I really don't want to cut it down for this so I will be looking for another motor for this mount. The worm block has some extra holes and looks like it may have been repurposed from another mount. 

 

attachicon.gifIMG_2565.JPG

Very impressive! The gear was made that way to remove backlash, I think.  David


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#29 Mr Magoo

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Posted 19 September 2021 - 06:37 PM

Well that is pretty much what I have for now guys and gals.

 

I forgot to mention that the 50mm Criterion eyepiece is very nice and one that I do not have even with all of my Criterion stuff. 

 

I have not had the scope long enough to have it out in the field yet. I'm betting it is a great performer. I will definitely get it out for a push to session and not wait until I find a motor. 


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#30 Marc-Andre

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Posted 19 September 2021 - 06:41 PM

This interesting little bracket is attached to the finder and is made of wood. Not sure what it was used for. 

 

attachicon.gifIMG_2552.JPG

Is it open to the finder internals.  It might have been for a light bulb to illuminate the reticle. 



#31 RichA

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Posted 19 September 2021 - 06:42 PM

This interesting little bracket is attached to the finder and is made of wood. Not sure what it was used for. 

 

attachicon.gifIMG_2552.JPG

illuminating the reticle.


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#32 mdowns

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Posted 19 September 2021 - 06:44 PM

Did you find this local Ken? There are one or two old IAS members down here I could possibly bounce this off of.



#33 Mr Magoo

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Posted 19 September 2021 - 06:45 PM

Here's a great article that may shed some light:

https://stellafane.o...illard/mak.html

 

Roberrt

Ah yes Robert my friend!  I have found that page too, but I am still chasing. A little more info on that. Allen Mackintosh who was a co-founder of the Maksutov Club was here in Indiana at the time this scope was purportedly made. He was working at Indiana University in Bloomington, Indiana  as stated in this transcript of his letter which. This scope came from a widow of a gentleman who owned it in Bloomington, Indiana. To add to the story a little more, Mackintosh was also a member of our astronomy society at one time. 


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#34 Brent Campbell

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Posted 19 September 2021 - 06:47 PM

Any idea where the optics came from?  I understand that Cumberland optics, who made the optics for quester and quantum, sold optic sets back in the day.  Does the focal length and aperture match the questar?  
 

The real question is how does it perform optically?  It sure is a beautiful telescope!


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#35 Mr Magoo

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Posted 19 September 2021 - 06:47 PM

Is it open to the finder internals.  It might have been for a light bulb to illuminate the reticle. 

It is not. I don't believe that it was used to light the reticle. 



#36 luxo II

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Posted 19 September 2021 - 06:47 PM

The RA motor is missing. The brass gear is interesting to me in that it is actually two separate sheets cut to make one gear. I can not understand why it is made this way and what is up with the springs.

 

Wow lucky you, its great to see another of the ATM maks surviving from the Maksutov Club which puts it around late 1950's, maybe 1960... The club members shared the know-how and blanks from Hayward or Newport Glass, the optics made by each ATM. It looks a similar to the one by Carl Dahl in Gleanings Bulletin C, page 18.

 

The 4" versions were scaled from John Gregory's 6" design resulting in f/23.

 

OK... the gears.. this was a way to remove backlash, I made one like this a long time ago.. The worm wheel is split in two halves and the two halves are tensioned with springs against each other, so that the teeth engage the worm firmly. If you ever dismantle this, you need to find a way to rotate one gear against the other, preloading the springs, before meshing the teeth with the worm again.


Edited by luxo II, 19 September 2021 - 07:12 PM.

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#37 Mr Magoo

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Posted 19 September 2021 - 06:48 PM

Any idea where the optics came from?  I understand that Cumberland optics, who made the optics for quester and quantum, sold optic sets back in the day.  Does the focal length and aperture match the questar?  
 

The real question is how does it perform optically?  It sure is a beautiful telescope!

No clue where they came from. I have not had it out yet. 



#38 MisterDan

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Posted 19 September 2021 - 07:06 PM

Any idea where the optics came from?  I understand that Cumberland optics, who made the optics for quester and quantum, sold optic sets back in the day.  Does the focal length and aperture match the questar?  
 

The real question is how does it perform optically?  It sure is a beautiful telescope!

This one looks to be f/20, at least, so my guess is "no," on Cumberland.  Likely home- or custom-built.  I doubt there were many makers of long-focal-length Maksutov optics ca. 1950s-'60s, so that may narrow the focus quite a bit - especially if the scope has stayed "close to home."

 

Best wishes.

Dan


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#39 DAVIDG

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Posted 19 September 2021 - 07:06 PM

 Ken,

   It looks like the primary does not have a baffle ? Hayward Optical made molded meniscus blanks to make the John Gregory design including one in the 4" diameter.   

 

                       - Dave 


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#40 Mr Magoo

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Posted 19 September 2021 - 07:15 PM

 Ken,

   It looks like the primary does not have a baffle ? Hayward Optical made molded meniscus blanks to make the John Gregory design including one in the 4" diameter.   

 

                       - Dave 

You are correct Dave, it does not have a baffle. 



#41 luxo II

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Posted 19 September 2021 - 07:39 PM

Without a baffle it may be a bit disappointing. How are the coatings of the mirrors ? 



#42 Mr Magoo

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Posted 19 September 2021 - 07:45 PM

Without a baffle it may be a bit disappointing. How are the coatings of the mirrors ? 

The coating looks okay.



#43 Mr Magoo

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Posted 19 September 2021 - 07:47 PM

Was it common for people to build them without baffles back then?



#44 MisterDan

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Posted 19 September 2021 - 08:09 PM

Was it common for people to build them without baffles back then?

In general, a longer-focal-ratio Maksutov => smaller secondary mirror/baffle => smaller/shorter primary baffle.  Front-end "shield" (baffle) length/diameter is also key.  Many makers install primary baffles that are far too long & wide.

 

There does seem to be a small/short primary baffle visible.  Without knowing the focal ratio and other optical specs, visual inspection of the secondary/primary baffle "interaction" (via both entrance pupil and rear port) can provide more insight.

 

Cheers.

Dan



#45 DAVIDG

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Posted 19 September 2021 - 09:32 PM

 Two years ago I observed with John Gregory's s original 6" f/23 Maksutov at Stellafane. It was given to Bert Willard to display at Hartness House Amateur telescope making museum. That instrument  also lacked baffling and during the day the views were very washed out from the stray light introduced into the image plane.

   I also own a 6" Fecker Celestar which is 6" f/15 Maksutov and it lacked a primary baffle originally and again the images even at night were very washed out from  the sky flooding of stray light into the focal plane. I added a primary baffle and the contrast greatly improved. https://www.cloudyni...ar-6-questions/

    Both commercial telescopes like Questar and Quantum are baffled. So if you want the very best contrast your going to have to add a primary baffle tube.

 

                - Dave 


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#46 tim53

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Posted 19 September 2021 - 11:14 PM

A quick and dirty way to determine if your cass might not be properly baffled is to take out the eyepiece in the daytime, and look through the draw tube and see if you can see anything besides the secondary mirror.  If you can, you need a better baffle.

 

As the late Henry Miller, of the Orange County Astronomers once said:  "Cassegrains are a baffling problem."


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#47 MisterDan

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Posted 20 September 2021 - 12:44 AM

A quick and dirty way to determine if your cass might not be properly baffled is to take out the eyepiece in the daytime, and look through the draw tube and see if you can see anything besides the secondary mirror.  If you can, you need a better baffle.

 

As the late Henry Miller, of the Orange County Astronomers once said:  "Cassegrains are a baffling problem."

Maybe not "better."  Maybe "present."

 

Most cassegrain users do not bother with entrance pupil extensions (aka "light shields," "dew shields" - whatever you prefer to call them).  I'll never understand that.

 

I see another side to the coin:  if you perform that quick and dirty test without a light shield up front, and your scope "passes" said test (i.e. you see nothing but the secondary and its baffle), then you need a better baffle (or two).

 

Cheers and best wishes.

Dan


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#48 tim53

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Posted 20 September 2021 - 09:50 AM

Maybe not "better."  Maybe "present."

 

Most cassegrain users do not bother with entrance pupil extensions (aka "light shields," "dew shields" - whatever you prefer to call them).  I'll never understand that.

 

I see another side to the coin:  if you perform that quick and dirty test without a light shield up front, and your scope "passes" said test (i.e. you see nothing but the secondary and its baffle), then you need a better baffle (or two).

 

Cheers and best wishes.

Dan

I need coffee.  I don't understand.



#49 tim53

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Posted 20 September 2021 - 09:54 AM

(My 12.5" f/23 Cassegrain has a 5 ft tube, so the secondary is a foot inside the tube.  It's a bit awkward to carry around, so I prefer leaving it on a mount, but it helps with stray light (and dew, I suppose).  I also designed the baffle by starting too long and cutting back.  It's made out of PVC, so if I screwed up I could start over for a few cents.

 

-Tim.

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#50 Terra Nova

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Posted 20 September 2021 - 10:01 AM

(My 12.5" f/23 Cassegrain has a 5 ft tube, so the secondary is a foot inside the tube.  It's a bit awkward to carry around, so I prefer leaving it on a mount, but it helps with stray light (and dew, I suppose).  I also designed the baffle by starting too long and cutting back.  It's made out of PVC, so if I screwed up I could start over for a few cents.

 

-Tim.

Tim, your likeness here has gone from Santa Claus to Karl Marx! :lol: ;)


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