Jump to content


Photo

Davidson 10" reflector 1947

  • Please log in to reply
48 replies to this topic

#26 terraclarke

terraclarke

    Fly Me to the Moon

  • *****
  • Posts: 5237
  • Joined: 29 May 2012
  • Loc: The Bluegrass State

Posted 06 August 2014 - 09:28 PM

Wow Ken! That's cool and the price is right for sure. Clean that puppy up and put her together and you've got one heck of a nice 10" reflector. Very nice, and good condition considering the age. Congrats!


  • Mr Magoo likes this

#27 rnc39560

rnc39560

    Surveyor 1

  • *****
  • Posts: 1947
  • Joined: 23 Jul 2013
  • Loc: MS coast

Posted 06 August 2014 - 10:11 PM

I can't find it in your thread. What's the f/ ratio? It looks loooonnnggg!  :)



#28 Mr Magoo

Mr Magoo

    Surveyor 1

  • *****
  • Posts: 1952
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 07 August 2014 - 12:15 AM

I can't find it in your thread. What's the f/ ratio? It looks loooonnnggg!   :)

I believe it is a 10" f/8 from the measurements I have taken on the OTA. I have not done the test with the mirror yet. 


  • terraclarke likes this

#29 Geo31

Geo31

    Vanguard

  • *****
  • Posts: 2342
  • Joined: 28 Jan 2013
  • Loc: Kingwood, TX

Posted 07 August 2014 - 06:39 AM

That is one seriously cool scope!  Oh man, it needs to be mounted on a steampunk GEM.


  • Mr Magoo and terraclarke like this

#30 Mr Magoo

Mr Magoo

    Surveyor 1

  • *****
  • Posts: 1952
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 07 August 2014 - 08:57 AM

That is one seriously cool scope!  Oh man, it needs to be mounted on a steampunk GEM.

That is one of the things I've been thinking about George. What would be an appropriate  mount for this if it were an ATM scope made in 1947? I really wish I could find out what happened to the mount. If a person put this much thought into the OTA, you would have to think he or she would spent some time on the mount too. I'm not giving up trying to find the maker. Just who was F. Davidson?

 

So this brings up some questions I have for the group. What was the state of ATM'ing in 1947? I'm guessing this tube is some sort of a composite material like fiberglass or phenolic possibly. Were these materials available or being used in telescope making in 1947?

 

I think when my friend, and I too, first saw the cast aluminum mirror cell, we assumed that it must be commercially made. After all, who casts there own aluminum cells? After looking at the other metal work, I kind of formed an image in my mind of a person making this scope that may have developed those skills during the wartime since this was not long after the end of WWII . Machining and metal working skills were everywhere during WWII.

 

There is some damage to the section of tubing on the focuser end, so I will be removing it today to try and effect a repair. Like a lot of old scopes, it looks like it may have been knocked over at some time and cracked the tube around the focuser hole. Luckily the focuser is okay. 



#31 Geo31

Geo31

    Vanguard

  • *****
  • Posts: 2342
  • Joined: 28 Jan 2013
  • Loc: Kingwood, TX

Posted 07 August 2014 - 12:32 PM

Hard to say on the mount.  My BiL has his father's ATM 6" scope that is probably from around the same era (I need to have him set it up sometime so I can take pics).  It's actually the first scope I ever looked through and was what started my interest in this pursuit.

 

I haven't seen the scope in many many years, but my recollection is the mount was based upon pipe fittings.  The pipe has inserts IIRC that were machined nice and smooth.  I cannot remember if it was brass or just painted a brass/gold color.  The interesting thing is the shaft housings were about twice as long as typical plumbing fittings.  I'm 98% certain that the shafts were NOT threaded, i.e., into the dec housing or into the saddle.  Something of that sort seems appropriate.

 

Again, such a cool scope!

 

As you said, there was a lot of talent around back then and a lot of surplus as well.



#32 Mr Magoo

Mr Magoo

    Surveyor 1

  • *****
  • Posts: 1952
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 07 August 2014 - 12:42 PM

Here is a shot for some perspective on the size of this. I'm 5'-8" tall. It is mirror cell up. No glass in it here. 

Attached File  001-002.JPG   453.77KB   2 downloads


  • xavier likes this

#33 Rich (RLTYS)

Rich (RLTYS)

    Fly Me to the Moon

  • *****
  • Moderators
  • Posts: 5254
  • Joined: 18 Dec 2004
  • Loc: New York (Long Island)

Posted 08 August 2014 - 05:39 AM

Healthy sized scope.

 

Rich (RLTYS)


  • Mr Magoo likes this

#34 amicus sidera

amicus sidera

    Skylab

  • *****
  • Posts: 4154
  • Joined: 14 Oct 2011
  • Loc: East of the Sun, West of the Moon...

Posted 08 August 2014 - 10:02 AM

This instrument, or parts of it, may have been produced by the Davidson Manufacturing Company of Alhambra and Los Angeles, California. 

 

Started in 1932, Davidson was apparently a producer, and at times a reseller, of photographic equipment, primarily darkroom gear and tripods. By 1952 the company seems to have become deeply involved in optics manufacturing and had four facilities in the L.A. basin, three in Alhambra and one in Los Angeles proper. In 1953 all production appears to have been moved to a brand-new facility in West Covina, California. The firm was tasked with re-figuring the primary of the 42" Clark & Sons reflector at Lowell Observatory in 1956. The company, or a branch of it, may have later became known as Davidson Optics, Inc., and eventually Davidson Optronics at present.

 

(Information in the foregoing paragraph collated from a brief web search)

 

As Lew Chilton mention in the archived CN article referenced by the OP, Davidson Manufacturing apparently produced a line of eyepieces and a focusing mount at their West Covina facility in 1955; eyepiece focal lengths were 11mm, 16mm and 22mm. Neither the eyepieces nor the focuser displayed in the S&T advertisements at the time resemble the focuser and eyepiece in the OP, but that is hardly surprising given that the latter may be eight years or more older. This single ad ran in S&T for only about a year, from mid-1955 to 1956.

 

Davidson Optronics has a website, as well as a telephone number and an email address if further inquiries are contemplated: http://www.davidsonoptronics.com

 

The Optical Society of Southern California might also be able to provide further information on this firm: http://www.ossc.org

 

Alternatively, the instrument's origins can forever remain a mystery.

 


Edited by amicus sidera, 08 August 2014 - 02:36 PM.

  • Mr Magoo and wfj like this

#35 wfj

wfj

    Apollo

  • *****
  • Posts: 1193
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 08 August 2014 - 02:15 PM

Here is a shot for some perspective on the size of this. I'm 5'-8" tall. It is mirror cell up. No glass in it here. 

attachicon.gif001-002.JPG

 

Understand this issue all to well.  I frequently come accross vintage scopes/mirrors that are too tall.

 

I remember Preston acquiring one years back - I asked him if he was going to make it into a travel telescope :)

 

I don't hear often of the outcomes of these. Myself and many others are a little gun shy of ladders - the mere memory of the ladder journey to the San Francisco Sidewalk Astronomers 24" eyepiece gives me the shudders...

 

Just last month got a nice 12" f/8 for free (the guy begged me to take it), but even assessing it is a chore given the 8 foot focal length! Guess I'm spoiled by small f/ scopes that keep my feet on the ground.

 

I've toyed with "low rider" and "chiefspiegler" (Ed Jones) remakes, but my heart isn't quite in those. The CO and/or making a custom plano concave lens isn't all that appealing, not to mention the functional issues of counterweighting such on GEM mounts.

 

What to do when they get too big.


Edited by wfj, 08 August 2014 - 02:17 PM.

  • Mr Magoo likes this

#36 amicus sidera

amicus sidera

    Skylab

  • *****
  • Posts: 4154
  • Joined: 14 Oct 2011
  • Loc: East of the Sun, West of the Moon...

Posted 08 August 2014 - 02:45 PM

 

 


 

What to do when they get too big.

 

 

I've seen raised decks built around instruments like these, with a hole in the center to accommodate the mount and pier, as well as allow clearance for the lower part of the tube; thus the eyepiece remains at a reasonable height. A long-focus reflector as described, equipped with a tiny secondary, could likely equal or best any refractor of similar aperture in regards to planetary viewing, not to mention saving the happy owner $100,000 or so...  :)


Edited by amicus sidera, 08 August 2014 - 02:46 PM.


#37 Mr Magoo

Mr Magoo

    Surveyor 1

  • *****
  • Posts: 1952
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 08 August 2014 - 06:18 PM

This is why I thought of the English style fork mount (I think that is the correct term) because it will get the eyepiece lower. It is certainly era appropriate. Mel's scope sure inspired me also. Terra suggested looking in Ingalls's "Amateur Telescope Making" book and I just happened to have a copy. Low and behold, it is a 1947 edition, same as the scope. 


  • terraclarke likes this

#38 Mr Magoo

Mr Magoo

    Surveyor 1

  • *****
  • Posts: 1952
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 09 August 2014 - 08:09 AM

The total weight of the OTA with optics is a hair over 36 pounds. 



#39 amicus sidera

amicus sidera

    Skylab

  • *****
  • Posts: 4154
  • Joined: 14 Oct 2011
  • Loc: East of the Sun, West of the Moon...

Posted 09 August 2014 - 11:13 AM

That's some heavy iron! I suspect that cooling time may be a wee bit longer than that of your RV-6...  :grin:


  • Mr Magoo likes this

#40 fjs

fjs

    Surveyor 1

  • *****
  • Posts: 1627
  • Joined: 25 Mar 2013
  • Loc: Olympic Peninsula, USA

Posted 09 August 2014 - 11:15 AM

I have no idea if you want to see this, but here it is. Mount on Ebay



#41 wfj

wfj

    Apollo

  • *****
  • Posts: 1193
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 09 August 2014 - 04:19 PM

Fred,

Thanks for your answer, its very smart. But there are limits - when I was younger (20's) went through long refractor craze, where 8"/12"/16" refractors mattered. Got cured of that with a "clean and jerk" of a vintage 8" f/15 tube (sans focuser and objective + cell) onto a high saddle.

 

Closing on 60's, this is less interesting. Permanant observing fixtures also - when I observe its almost always mobile - last night I made my usual pilgrmage to the other side of the hill for Antares, M4, Saturn and Mars.

 

The 4" f/6.5 and the 12.5" f/4.8 get moved there more often.

 

Ken,

Have done the deep fork. Tends to vibrate. Needs a tapered design that makes big/stiff even more so. When you build big, things add up fast.

 

 

Frank,

That mount I deferred buying when a few hundred to possibly a hundred. Know both the guy selling and the guy that bought in order to sell. First sells things that are collections of parts, on the promise of a whole. Second one profits by remarketing 10x-20x and takes 5-10 years to sell fram a magnificent junkyard (or telescope art gallery). Interesting characters, hae bought from them, as well as TG.

 

I didn't buy it because it is too heavy, parts (in my opinion) are too worn and unmodifieable/replaceable, it vibrates way too much, has a too small chain drive that has way to much flex. I need light because of portable. Other than that its fine.

 

I looked at it because I had a scope that would have fit immediately.



#42 Geo31

Geo31

    Vanguard

  • *****
  • Posts: 2342
  • Joined: 28 Jan 2013
  • Loc: Kingwood, TX

Posted 09 August 2014 - 06:37 PM

My BiL's scope mount...

Attached Files


Edited by Geo31, 09 August 2014 - 06:45 PM.

  • terraclarke likes this

#43 terraclarke

terraclarke

    Fly Me to the Moon

  • *****
  • Posts: 5237
  • Joined: 29 May 2012
  • Loc: The Bluegrass State

Posted 10 August 2014 - 02:14 PM

I wonder if this could be converted? It looks like it might be big enough? I will be there tomorrow night and could have a looksee?

 

http://www.cloudynig...division-mount/


  • Mr Magoo likes this

#44 wfj

wfj

    Apollo

  • *****
  • Posts: 1193
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 10 August 2014 - 08:54 PM

By the way, I have built and converted fork mounts before. You see one of them in my avatar image adjacent to this post.

 

My first attempt was cast aluminum, where I made the wooden forms for the arm and joining block. It was solid but extremely heavy.

 

The one in the image is Mark II - it was made of sheet aluminum on the outside and a honeycomb/eggcrate on the inside. So it turned out lighter and stiffer. The base and axle were not stiff enough - Mark III unbuilt was to be a honeycomb cone axle against a honeycomb inverted arch base, but I never came up with a good enough dimensional control for the complex sheet metal fabrication.

 

The approach came out of work with aircraft/spacecraft structures. My dad, who did satellites including the Voyagers and Viking, wanted me to make it out of composites using graphite filled epoxies - he was a master of glues among other things. Wish we'd had the chance to work out the bugs back in the 70's...



#45 Mr Magoo

Mr Magoo

    Surveyor 1

  • *****
  • Posts: 1952
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 11 August 2014 - 12:56 PM

I wonder if this could be converted? It looks like it might be big enough? I will be there tomorrow night and could have a looksee?

 

http://www.cloudynig...division-mount/

That looks really neat Terra. Unfortunately I have no funds to buy anything right now after being off from work for so long after my surgery. Hopefully I will be able to do something about a mount when I get back to work. For now I can fiddle around with the OTA. A fellow club member is going to take a cursory look at the mirror with a Ronchi EP this Saturday. For now this is the only test I can do, but it will show us if there is anything horribly wrong with it. 



#46 Mr Magoo

Mr Magoo

    Surveyor 1

  • *****
  • Posts: 1952
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 11 August 2014 - 12:59 PM

By the way, I have built and converted fork mounts before. You see one of them in my avatar image adjacent to this post.

 

My first attempt was cast aluminum, where I made the wooden forms for the arm and joining block. It was solid but extremely heavy.

 

The one in the image is Mark II - it was made of sheet aluminum on the outside and a honeycomb/eggcrate on the inside. So it turned out lighter and stiffer. The base and axle were not stiff enough - Mark III unbuilt was to be a honeycomb cone axle against a honeycomb inverted arch base, but I never came up with a good enough dimensional control for the complex sheet metal fabrication.

 

The approach came out of work with aircraft/spacecraft structures. My dad, who did satellites including the Voyagers and Viking, wanted me to make it out of composites using graphite filled epoxies - he was a master of glues among other things. Wish we'd had the chance to work out the bugs back in the 70's...

As a sheet metal worker and welder for 29 years,I have a fair bit of the metal working skills to do a lot of the fabrication. I'm no machinist or engineer, so some of that I have to fake my way through. Unfortunately I do not have a welder at home that can do aluminum, but I do have access to machines at work when I get back to work. 


  • wfj and terraclarke like this

#47 Mr Magoo

Mr Magoo

    Surveyor 1

  • *****
  • Posts: 1952
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 15 August 2014 - 09:51 PM

I did a bunch of crack repair on the upper section of the tube today. I simply opened up the cracks the best that I could and ran liquid form cyanoacrylate into them. I then quickly clamped them down or put pressure on them until it set. The glue worked great. It really absorbed into the crack and seems very strong now. After reading the other thread about heating up the RV-6 tube, I am really thinking that this is an actual Bakelite tube. I have not done the 409 test on it yet to see for sure. 

 

Where would someone have been able to get a tube like that in 1947? It is perfectly 11" I.D. and .125" thick. I think it it Bakelite because it has no discernible layers and the color is consistent all the way through. 

 

Funny story about Bakelite. My Grandmother had a set of Bakelite dishes she bought from a traveling salesman. My Mother and her twin sister sat and listened to the salesman's pitch about how they were unbreakable. So as soon as they got a chance they took one of Grandma's new bowls out in the street and whacked it with a hammer. The salesman thought it was funny luckily and replaced it for free. 



#48 amicus sidera

amicus sidera

    Skylab

  • *****
  • Posts: 4154
  • Joined: 14 Oct 2011
  • Loc: East of the Sun, West of the Moon...

Posted 16 August 2014 - 12:15 AM

Where would someone have been able to get a tube like that in 1947?

 

 

Bakelite's been available since near the beginning of the twentieth century. Matter of fact, you can still get custom Bakelite-type tubes made today; they are used primarily for transformer winding cores.


  • tim53 likes this

#49 Mr Magoo

Mr Magoo

    Surveyor 1

  • *****
  • Posts: 1952
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 18 August 2014 - 02:18 PM

I was able to take the mirror to my club meeting last Saturday and have one of our members take a look at it. We were able to examine it with a Ronchi screen, but we had a problem with  the Foucault tester and were unable to to do any knife edge tests. We will try and take another run on it with the Foucault at another time. I'm no expert with mirror testing, but my fellow member has quite a bit of mirror making experience. The Ronchi images looked very good. He had printed out some pictures of exactly what we should be seeing for that size mirror and the image looked just like the ideal model. With just the 3 bars showing it looked great to my inexperienced eye. No edge problem showing and the middle lined was dead straight. This gives me a bit of confidence now that I can work on the rest of the OTA and not be wasting my time if the mirror was a complete mess. I had already decided that if the mirror has issues, I am going to try and correct it on my own. I'm wanting to grind a mirror soon anyway and so is another club member. Unfortunately we have no instructor, so we will be relying on our study of written material we have. 








Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics