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New to me 8” 1940s needing refurb

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#26 mconsidine

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Posted 25 September 2020 - 08:55 PM

Ok I guess that's not a latitude adjustment. My mistake...

#27 tim53

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Posted 25 September 2020 - 10:06 PM

That's a bit of a variant I don't think I've seen before. Ie the latitude adjustment ...

Looks to be made for less than 45 degrees latitude.  might be a clue as to where it was made.



#28 Cato85

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Posted 25 September 2020 - 10:55 PM

After a few nerve wracking hours the main reflector is in a viewable state. I’m still pondering a full true restoration to get rid of the deeper wipe lines from the previous person’s cleaning and the minor acid water marks, But I’m super surprised still yet in its condition. And it’s the fastest blind cell alignment and encasement to original position I’ve ever had. After cleaning viewing through the raw glass sides it indeed is Pyrex it does have a green hue to it. I stand corrected on the blue hue as I previously said, I used alternate lighting source to check for this.

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Edited by Cato85, 26 September 2020 - 03:59 AM.

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#29 Cato85

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Posted 25 September 2020 - 11:53 PM

Looks to be made for less than 45 degrees latitude.  might be a clue as to where it was made.

From what I’ve been able to ascertain is it was probably built in Washington state for an owner a father son astronomy team who lived in California. Primary reflector hand shaped and ground and coated by a university student in central/Southern California. 
prisms from laboratory optical company in New Jersey. Used for astrophotography in Arizona/New Mexico. Then the family moved to Iowa. Father passed away and left it to his son who passed away who gave it to his friend my neighbor who had it for about 5-6 years who gifted it to me earlier this week. I’m still trying to pin names date and so fourth but it’s quite a good tale to learn and hear about (better than any story I’ve been a part of). I’m a California native who lives here in Iowa and California.


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#30 davidc135

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Posted 26 September 2020 - 06:50 AM

The mirror is more likely to be plate if it's noticeably green. My 6'' pyrex flat is a very pale yellow green when seen through the side.  David



#31 tim53

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Posted 26 September 2020 - 11:28 AM

Is the mirror glued into the cell?  What does the back look like?  And is the mirror tapered (from a mold) or ground flat on the back and straight on the sides?

 

-Tim.



#32 Cato85

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Posted 26 September 2020 - 01:33 PM

The mirror is more likely to be plate if it's noticeably green. My 6'' pyrex flat is a very pale yellow green when seen through the side.  David

 

Is the mirror glued into the cell?  What does the back look like?  And is the mirror tapered (from a mold) or ground flat on the back and straight on the sides?

 

-Tim.

The rear is completely flat. Coated surface is slightly concave to focus the light. Under compact fluorescent light it appears blue so I used incandescent and it appeared to have a slight green hue. The rear under magnification has very little air bubbles suggesting a mold contact. Outside rim is ground circular with tooling marks at about 70*ish angle and the upper and lower edges are a non uniform 45* back cut to remove the harsh edge. The cell is wood rear with a metal bezel on the optical side. It’s retained by three screws. In the wood portion first is a heavy card stock type of paper then two layers above it of a thicker more compressible type of paper, around the edge is also a thick type of paper. 
 

the photo I posted that the blue hue is apparent is a photo of the rear surface. 
the only color that was very noticeable was blue. Under the alternative light source it was slightly greenish. 


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#33 Cato85

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Posted 26 September 2020 - 01:45 PM

Larger rear view under CFL light

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#34 Cato85

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Posted 26 September 2020 - 01:47 PM

Larger of the edge 

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Edited by Cato85, 26 September 2020 - 01:53 PM.


#35 davidc135

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Posted 26 September 2020 - 02:16 PM

Density would settle it. I see specific gravities of 2.23 for low expansion boro-silicate inc pyrex, 2.4 for plate and 2.5 or so for today's float. So, quite a difference.  David



#36 Cato85

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Posted 26 September 2020 - 02:39 PM

Density would settle it. I see specific gravities of 2.23 for low expansion boro-silicate inc pyrex, 2.4 for plate and 2.5 or so for today's float. So, quite a difference.  David 

 

Could there be a non-invasive test rather than using a piece of it or suspending in water and using weight differential? Possibly an infrared laser used by a gemologist or such to determine the compounds? I really don’t want to damage it in any way. It already has two small chips. 
 

Also what would the significance be between the grades of glass. Other than trying to pin down a manufactured date range?


Edited by Cato85, 26 September 2020 - 02:46 PM.


#37 DAVIDG

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Posted 26 September 2020 - 06:10 PM

 The fact that the blank is clear and polished on the back surface is  evidence that is made from green plate glass. Pyrex blanks made in that time frame were made by Corning and sloped side, raised rim on the back and made in a mold that had Corning Pyrex impressed in the glass.  So the shape was very distinctful.   The glass type is not really that important. What is, is the quality of the figure on the mirror. The fact that the coating is still reflective indicates that at some point, it was aluminumized vs chemically silvered. 

   I also have the original blue prints and casting as well made from the original patterns.

 

                               - Dave  

 

SPRINGFIELD blueprint.jpg


Edited by DAVIDG, 26 September 2020 - 07:17 PM.

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#38 Cato85

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Posted 26 September 2020 - 06:39 PM

 The glass type is not really that important. What is, is the quality of the figure on the mirror. The fact that the coating is still reflective indicates that at some point, it was aluminumized vs chemically silvered. 

   I also have the original blue prints and casting as well made from the original patterns.

 

                               - Dave  

 

attachicon.gifSPRINGFIELD blueprint.jpg

Thats absolutely cool what you have there. Is that a reprint? Looks original to me. I agree it’s got an aluminum type coating. I’m looking into having it ran through a spectrometer to see exactly what the coating is and glass material so I can actually date the coating and glass. Just for my own curiosity. 



#39 davidc135

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Posted 26 September 2020 - 06:54 PM

Could there be a non-invasive test rather than using a piece of it or suspending in water and using weight differential? Possibly an infrared laser used by a gemologist or such to determine the compounds? I really don’t want to damage it in any way. It already has two small chips. 
 

Also what would the significance be between the grades of glass. Other than trying to pin down a manufactured date range?

If you decide to have it recoated it could be weighed out of the cell, either in and out of water as you say or the volume of glass could be calculated if it is regular. I don't suppose it matters very much as far as performance goes. The plate mirror figure might be distorted a bit more during cooling.



#40 DAVIDG

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Posted 26 September 2020 - 07:06 PM

 It is an original blue print sold by John Pierce of the Springfield Telescope Makers.  Both plate glass and Pyrex was available starting in the 40's. Aluminumizing started commercially in the mid 40's. One of the most popular was Clausing in Illinois.  It could be have recoated many times since the 40's thou. 

    I believe you said that the focuser had a manufactures name. In my opinion that is the best clue you have to when the scope was made.

 

                             - Dave 



#41 jcruse64

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Posted 26 September 2020 - 07:12 PM

Dave, you are a treasure!



#42 Cato85

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Posted 26 September 2020 - 07:50 PM

If you decide to have it recoated it could be weighed out of the cell, either in and out of water as you say or the volume of glass could be calculated if it is regular. I don't suppose it matters very much as far as performance goes. The plate mirror figure might be distorted a bit more during cooling.

 

 It is an original blue print sold by John Pierce of the Springfield Telescope Makers.  Both plate glass and Pyrex was available starting in the 40's. Aluminumizing started commercially in the mid 40's. One of the most popular was Clausing in Illinois.  It could be have recoated many times since the 40's thou. 

    I believe you said that the focuser had a manufactures name. In my opinion that is the best clue you have to when the scope was made.

 

                             - Dave 

Thank you Dave and Dave. Also volume can be calculated on irregular items using the displaced water. 
I’m sure it’s been recoated at some point. Although the secondary mirror attached to the spider appears to be silvered as there’s bleed lines down the sides. And it’s definitely a plate glass. 

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#43 DAVIDG

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Posted 27 September 2020 - 09:30 AM

 If the diagonal was silvered it would  be badly  tarnished by now, so it has been aluminized.  From  the shape it is most likely war surplus and made from optical glass like BK7.

 I highly recommend you learn to test the mirrors or have them tested. You are going to spend a good amount of time restoring this one and if the optics have issues it will be a disappointment and it will not get used.  It does no good in my opinion to have a telescope that is pretty to look at, but poor to look through.

 

 Here is a picture of similar antique telescope that I restored  with a  modified Springfield type mount that was written up in Scientific American in the early 50's. The mirror is made of plate glass and looked like someone polished it with steel wool at one time so I had to totally repolish it back to an optical polish and refigure the optics.  Now it works like a telescope should.

 

  The Springfield mount  was feature on  the covers of Scientific American in 1926. 

   

 

                 - Dave 

 

dmg antique telescope.jpg

 

2amSciAmmrach1926 v2.jpg


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#44 clamchip

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Posted 27 September 2020 - 10:27 AM

I own a 6 inch Springfield I need to finish.

In the photos its mounted to a Edmund Extra Heavy Duty pedestal and legs I added to

make it so I can work on it.

Built by R. V. Leonard and addressed to the U. S. Marine Hospital here in Seattle.

The restoration was started by a friend who moved to smaller quarters, no longer had

the space for it.

During his restoration he replaced the damaged steel tube with a aluminum one (I wish

the old steel tube was still around but it was thrown out) and had the mirrors re-coated

by P. A. Clausing Inc. in 1996. Primary mirror is plate glass, 6 inch f/8.42 

Robert

 

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Edited by clamchip, 27 September 2020 - 10:29 AM.

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#45 sbrewster

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Posted 27 September 2020 - 01:02 PM

Thanks Tim for this link... a wonderful video.

 

--Steve


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#46 Cato85

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Posted 27 September 2020 - 02:55 PM

 If the diagonal was silvered it would  be badly  tarnished by now, so it has been aluminized.  From  the shape it is most likely war surplus and made from optical glass like BK7.

 I highly recommend you learn to test the mirrors or have them tested. You are going to spend a good amount of time restoring this one and if the optics have issues it will be a disappointment and it will not get used.  It does no good in my opinion to have a telescope that is pretty to look at, but poor to look through.

 

 Here is a picture of similar antique telescope that I restored  with a  modified Springfield type mount that was written up in Scientific American in the early 50's. The mirror is made of plate glass and looked like someone polished it with steel wool at one time so I had to totally repolish it back to an optical polish and refigure the optics.  Now it works like a telescope should.

 

  The Springfield mount  was feature on  the covers of Scientific American in 1926. 

   

 

                 - Dave 

Yes. I’m building the test stands this week and hopefully can complete the main reflector testing by next weekend. Before I go to Las Vegas for the first time ever the following week. I wholeheartedly agree that having a nice telescope with unobservable equipment is useless. I’m a very determined person and I will get this operable. Even if I have to build my own ion glow depositor maybe. I went to school for aeronautical engineering. I’m definitely not an optical specialist by any means, but I can suss out most things and I’m quite resourceful and very patient.  I’m in this for it’s history and to let my kids observe history through history. I’m really appreciative for everyone’s assistance, knowledge and experience it really is invaluable. 



#47 tim53

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Posted 27 September 2020 - 03:17 PM

Thanks Tim for this link... a wonderful video.

 

--Steve

Hi Steve:  At the risk of getting off topic, that telescope is available for use in a public outreach setting.  I inquired about it, but my observatory is isolated and I'm still working full time.  And it was too expensive to buy outright.

 

-Tim.



#48 Cato85

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Posted 29 September 2020 - 09:26 PM

Ok so after looking at how much it’s going to cost me to build an ion glow depositor it’s slightly prohibitive in cost, for a single set of optics. I’d really appreciate any suggestions for having the primary and secondary mirror recoated with a company or individual whom I can trust in the care and attention of the items. I will not mail them due to unknown issues that can arise, so I’d prefer to transport them personally. Any and all suggestions are greatly appreciated. Thank you everyone. 
 

Tim you’re not off topic I totally understand your wanting that lovely observing piece. 



#49 DAVIDG

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Posted 29 September 2020 - 10:22 PM

 My recommendation is that you first need to test the optics. It makes no sense to me  to recoat optics that are poorly figured. Recoating them wouldn't make them better. 

 

                           - Dave 


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#50 Terra Nova

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Posted 03 October 2020 - 12:40 PM

 My recommendation is that you first need to test the optics. It makes no sense to me  to recoat optics that are poorly figured. Recoating them wouldn't make them better. 

 

                           - Dave 

A lot of good, practical, common sense in that statement. You’ll never make a silk purse out of a sow’s ear. The primary optics are the very heart of the instrument. At least get a good Foucault test of the mirror if nothing else before proceeding much further.


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