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1930s Kosmos Fernrohr D61 "School Telescope"

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#1 Tom Duncan

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Posted 25 December 2024 - 12:20 PM

Got this from a fellow antique/collectible dealer friend, a 1930's era "Kosmos Fernrohr D61" 'school telescope' on heavy 27lb German Equatorial mount with setting circles and a set of eyepieces. Appears to be a 61mm diameter objective and possibly 810mm focal length. Stands 39" tall as shown. 

 

Happily the objective set, while dirty, appears to be in good condition, no chips and no coatings to decay but definitely will need cleaning.

 

That can't be said for the rest of the scope, has obvious cosmetic shortcomings, loose tripod feet (not shown, along with some other parts it came with), warped/bent OTA retainment bands, what appears to be a welded portion of the mount, missing screws that hold the cell to the tube, missing the finderscope as well as it's bracket and worst of all it's missing the focusing pinion/knob/housing assembly. As the 1.25" drawtube will just slide in and out it's possible to use the scope which I'll try the next clear night. 

 

The cell looks like it should have a dew shield on it but none of the images of this and similar Kosmos scopes of the period show one.

 

Surprisingly considering it's apparent rough and tumble life it came with four un-identified as to maker or focal length 1.25" eyepieces and a screw-on sun filter as shown in the second photo. The eyepieces each have a threaded portion on top where the Sun filter threads onto, I can't help but wonder if they originally came with some sort of threaded plate to cover the threads similar in shape to the Sun filter but with a hole in the middle. Anyone know? 

 

As you likely quickly figured out the tripod leg casting at the bottom is on upside down. It rotates around the center pole against some thick/old grease and appears to be retained by a single large screw but as the screw doesn't want to budge with the amount of effort I'm willing to pit against it I'll let the next owner deal with that. I suspect this was done because the metal feet that were attached to the adjustable posts have all come off (but stayed with the scope!) and instead of just unscrewing the posts and screwing them in upside down (thus the adjustment knobs became the feet) they turned the whole assembly upside down. However in doing so the center clamping knob and washer (not shown but somehow was kept the scope) stuck down too far such that the legs couldn't reach the floor so they left them off.

 

The movements of the DEC and AZ axes are smooth, not stuck, so again, usable. 

 

Poor night skies have kept me from taking it out for likely its first dark sky view in decades but tonight might offer me a few holes in the clouds. As the restoration project is beyond my time available I'll be letting this go in due time but before that I want to see what it does on Jupiter with both the original eyepieces and some Plossl's. 

 

Tom Duncan 

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#2 JamesMStephens

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Posted 25 December 2024 - 12:36 PM

That's really something!

 

Jim



#3 Couder

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Posted 25 December 2024 - 03:20 PM

I had two Alvan Clark refractors. The eyepieces were much like yours, the threads on top indeed held filters. (1-1/8" diameter) I had an orange and a blue filter. They had the Herschel wedge, so it was safe to look at the Sun. (I did so for over 30 years). Attached are a couple pictures of the filters and a few pictures taken through them.

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#4 Couder

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Posted 25 December 2024 - 03:22 PM

I made my own dew shields. (Close inspection will reveal I did nothing to alter the original.)

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Edited by Couder, 25 December 2024 - 03:22 PM.

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#5 Tom Duncan

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Posted 26 December 2024 - 12:33 PM

I had two Alvan Clark refractors. The eyepieces were much like yours, the threads on top indeed held filters. (1-1/8" diameter) I had an orange and a blue filter. They had the Herschel wedge, so it was safe to look at the Sun. (I did so for over 30 years). Attached are a couple pictures of the filters and a few pictures taken through them.

Ah, so that's where the eyepiece designations were, on the removable caps with the holes in them. At least until you had all the caps off and didn't note which one went which EP body though the size of the eye lens can suggest a bit. So in this case all the eyepieces are missing their caps. I bet I've had some of those caps in the past.

 

Tom


Edited by Tom Duncan, 26 December 2024 - 12:34 PM.


#6 Couder

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Posted 26 December 2024 - 01:13 PM

Designations are on the top of the eyepieces on the Clarks, nothing on the screws on filters.

#7 Degeraths

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Posted 07 January 2025 - 04:57 PM

Are you planning on selling this scope? I am looking for a 1920s/30s era scope to use at our 1930s era Living History events.



#8 starfinder123123

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Posted 07 January 2025 - 08:47 PM

I had two Alvan Clark refractors. The eyepieces were much like yours, the threads on top indeed held filters. (1-1/8" diameter) I had an orange and a blue filter. They had the Herschel wedge, so it was safe to look at the Sun. (I did so for over 30 years). Attached are a couple pictures of the filters and a few pictures taken through them.

Oh Man, I love that blue filter. Is there anything today that would look like that?


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#9 Couder

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Posted 07 January 2025 - 10:47 PM

I really don't know. I sold the scopes, and now use a Baader. I haven't tried a blue filter on it, but I'll try when it gets at least in the 40's
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