20 replies to this topic

[Linn]

Hello all,
I received a Edmunds 5 inch f/15 lens in its cell today and have a question. Looking at the lens I do not see any spacers between the elements. Does anyone know if there should be spacers, or am I missing something? I did set it up outside and got back (way back) and could find a focus point.

I have tried to load a picture, but I can't seem to get the file small enough, unless the image is thumbnail size.

Thank you for your help.
Linn

[apfever]

Linn,

My 4" Edmund refractor has three small foil spacers. I have an original vintage Edmund 1.25" focuser that fits in a 4-7/8" I.D. tube.

[Chuck Hards]

Could it be cemented?

[apfever]

I didn't consider a new lens, if it is a new lens. I've had two edmund 4" vintage and both were spaced doublets. I have not seen a 5", vintage or newer.

[Linn]

From what I can tell from the little on the internet, these objectives may have been designed by Dr. Rank. I sent a PM to a CN'er in Australia who has one a week ago looking for info and am still waiting for a reply.

If anyone wants to see pictures, PM me with an email and I will send the ones I took this afternoon.
Thanks,
Linn

[clamchip]

The early Edmund 5" lens is a f14.2 (71"FL) and came with a aluminum cell with 3 120deg spaced clips to retain the elements within the cell. This one does use 3 foil spacers to air space the two elements.
Thats all I know about the Edmund 5" lens. Its extremely rare.

Robert

[bremms]

The newer Rank design has a 0.10mm airspace or 0.004" about 4 layers of thick aluminum foil. That is from the Edmund Optics spec sheet.

[Linn]

The early Edmund 5" lens is a f14.2 (71"FL) and came with a aluminum cell with 3 120deg spaced clips to retain the elements within the cell. This one does use 3 foil spacers to air space the two elements.
Thats all I know about the Edmund 5" lens. Its extremely rare.
Robert

Well, I will have to take a magnet to the cell, but the three clips are there. I suspect the cell is aluminum due to the weight.

bremms, is there any way I can get a copy of the spec sheet?

Thanks all,
Linn

[Chuck Hards]

Could it be a continuous-perimeter plastic spacer, and thus difficult to detect in-situ in the cell?

[Linn]

Could it be a continuous-perimeter plastic spacer, and thus difficult to detect in-situ in the cell?

Chuck, that has crossed my mind as well. The lens cell came from a PVC pipe telescope of unknown heritage. I don't know how old the lens set is. I will try to get some pictures up tomorrow.

[Linn]

As promised, pictures of the lens and cell. I have heard from the seller he had assumed it was an Edmunds as he did not know of any 5 inch objectives from other sources.

[clamchip]

I have the same lens and it is Edmund Scientific.
Do you have a picture of the printing on the lens cover?

Attached Thumbnails

• 

[clamchip]

This is the counter-cell supplied with mine, it fits inside a 7 inch OD tube and is split to to give some flexibility for various wall thicknesses of the tube.

Attached Thumbnails

• 

[clamchip]

I measured the 3 spacers and they are .005"

Attached Thumbnails

• 

[clamchip]

Most but not all Edmund lenses I've owned have index marks printed on the element edges, usually a number and a arrow on each element and you want the arrows to point at each other. You can see mine are a little off but pointing at each other.
If you find your index arrows are off like mine do not move them until you have star tested the lens, you can always line them up later.

Attached Thumbnails

• 

[clamchip]

Here's another example, 4"f15 Edmund lens:

Attached Thumbnails

• 

[clamchip]

Linn I see something under the 3 lens retainers, is it a black plastic spacer with a inward facing projection under each retainer?
Do you think the lens cover you have fits well enough to be original equipment? it looks like military surplus.

Robert

[Chuck Hards]

Wouldn't early Edmund hardware actually be military surplus?

[clamchip]

Linn's lens cover looks suspiciously like surplus military hardware.
Not the telescope objective lenses though. The 3, 4, 5, and 6 inch lenses were imported.
Some eyepieces and finders and other misc. things were also imported.
Most all the other optical stuff was military surplus.
It is believed the telescope objective lenses came from Carton in Japan. Since I have no idea myself (only that they were imported) I'm open to any ideas but until I see it in print on a document of some kind I will probably go to my grave wondering.
The good news for me is after I go to my grave I can ask Mr. Edmund himself!

Robert

[Linn]

First, I got to looking at the lens in different light this afternoon and I think Chuck may have been right about a plastic spacer. I can see a slightly milky annular ring, slightly offset, down in the glass. There is a very small clamshell on one of the interior surfaces and it seems to be at the same level as the ring.

Robert, there is a ring with a small dog ear shaped tab at each retainer, one hides the small clamshell, on the top of the front element. I also see what might be green felt (very thin) under the retainers. I just got out a flashlight and can see a faint 8 on each element and the two arrows pointing at each other! I do not have the split counter-cell. The objective was mounted in its old scope by three screws through the tube wall threaded into holes on the side of the cell. Any idea of the age of your objective?

The lens cap probably has a story of its own, it is imprinted "REAR 36-INCH F8" and is from Zenith Optical, a division of Polan Industries. I Googled and they made a lot of optical stuff for the DOD as well as coffee pots. I would have liked to see the 36 inch scope this came from. Maybe an entry into the rare scope thread? The cover has had small pieces cut out to fit around the machine screw heads on the side of the cell, so not original. Looks like it originally twisted off. The diameter is a perfect fit though.

Thanks for the info, keep any more information coming.
Linn

[clamchip]

Just as I suspected, the lens cover is from General Patton's coffee pot!
The oldest catalog I own is 1957 and the 5" lens is not listed. Next one I have is 1962 and the 5" lens is listed for $150, the 4 inch is $80.
The latest I have is 1971 and the 5" is still available at $185

Robert