14 replies to this topic

[ORION3004]

Hello Cloudy Nights members:

I need your help for the identification of the producer of the refractor lens that I show on the pictures, It is a 5 inch F15 achromat and it delivers outstanding moon and planets images. I bought it ca. 15 years in Germany in the form of a Newton type folded refractor, in a wooden square tube.

 

e.

 

[Joe1950]

Looks similar to this:

 

http://www.cloudynig...und-scientific/

[ORION3004]

Thank you Joe, but the cell is of Steel rather than of aluminium.

[ORION3004]

it weights 1600 g (3.5 lb).

[Starhawk]

It would appear to be a scientific lens someone got their hands on. That's about the only time you see a cell that large and made from stainless steel. I did some quick numbers- your weight only makes sense if the cell is steel.  Is it a doublet or a triplet? Count reflections from a flashlight.

 

-Rich

[ORION3004]

Hello Rich:

 

I am almost sure it is a doublet, because it has only three thin separators in a 120 degree array, you can see two of them on the first picture. I will count the reflections from a flashlight.

[catboat]

I think Joe1950 steered you in the right direction with post #2.  I believe Edmund used steel for some of its cells for other size objectives.  Edmund may have used steel for some of the 5” objectives as well.  The company sold a lot of products and fabricated parts to help sell various components for DIY projects.  I wouldn’t expect 100% consistency.  

 

Except for the split-ring counter cell shown in the thread that Joe linked, your cell looks like the 5" Edmund.  The three separate retainers for the glass are pretty distinctive.  It’s an easily copied design, of course, so not conclusive.  Your focal length is close to the advertised f/14 for the Edmund 5” objective.  

 

Examining the edge markings on the glass would be the best clue about the origin.

 

If you send Robert (“actionhac”) a PM, I’m sure he’d be interested in comparing details.  

Edited by catboat, 08 December 2015 - 03:58 AM.

[Jon Isaacs]

The coefficient of thermal expansion of steel is a better match for glass, aluminum can pinch the lens..

Jon

[clamchip]

It sure looks like my lens that Joe1950 has provided a link for above.

My cell is aluminum but Edmund did use steel for cells almost exclusively on the 3 and 4 inch f/15 lenses so

the chance of a steel 5 inch cell is pretty high.

The Edmund 5 inch lens has a very unusual f/14.2 focal ratio (71" inches) and will be a good measurement

to check for determining if its Edmund Scientific.

I'm within days of testing my lens, just a few finishing touches on the telescope I have under construction.

 

Robert

[ORION3004]

Thank you everyone, tomorrow I will measure the focal length, I will take advantage of the fact that the OTA is disassembled at this moment.

[ORION3004]

I measured the focal length (by measuring the light pathway among the lens and the two mirrors in the disassembled folded refractor) and it is roughly 177 cm (ca. 70 inches), which yields a F14 telescope, definitely it is not a F15, It is not possible to make an error of 4 inches in measuring the FL.

 

I think it is right, it is an old Edmund Scientific and I am totally satisfied with that, I like the old well renamed achromats. It is very comfortable because the focuser is almost at the middle of the tube and it is always at almost the same height no matter where the telescope is pointing (on an alt azimuth mount).

 

 

Martin

Edited by ORION3004, 12 December 2015 - 09:28 PM.

[Joe1950]

The Edmund optics, both mirrors and achromats were top notch, Martin. The one you have looks to be in excellent condition. Robert may know who supplied the lenses to Edmunds. Their mirrors were made, for the most part, by a local optician who did outstanding work. Then they would be sent to the Franklin Institute Science Museum in Philadelphia for final testing and evaluation.

 

I live about 15 minutes from the retail store site and would go there often. It was quite a place.

 

Enjoy that fine scope, Martin!

 

joe

[ORION3004]

thank you guys, I really appreciate your help, now I will proceed to assemble the OTA. And I am sorry because my posts are not eloquent, I am not an english native speaker.

[Joe1950]

Your posts are excellent, Martin!  

[clamchip]

The source of Edmund Scientific's telescope objectives has always been a mystery and I'll go to my grave wondering probably.

After that I can personally ask Norman Edmund!

In the 1950's the Edmund ads stated:

"We found a Japanese optical engineer who designed some excellent astronomical objectives. We place orders with him".

Based on various individual's recollections it appears more than likely it may have been Carton Optical Company that was the source.

 

Robert

Edited by actionhac, 13 December 2015 - 07:54 PM.