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Equipment Discussions >> Classic Telescopes

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starman876
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: TOM KIEHL]
      #5941895 - 06/26/13 06:28 PM

Gee that guy sounds like one of us 45 years ago

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Dave M
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: starman876]
      #5942138 - 06/26/13 09:10 PM

Quote:

Gee that guy sounds like one of us 45 years ago



You was around that long ago


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starman876
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: Dave M]
      #5942142 - 06/26/13 09:12 PM

I was in my twenties then

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starman876
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: starman876]
      #5942146 - 06/26/13 09:13 PM

If I find everything for that 6" cassegrain I will post a pic. I bought it from the guy who made it in 1978. Looks like Toms, but it in a aluminum tube. Came with a 16X50 finder. No idea where that went.

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Dave M
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: starman876]
      #5942169 - 06/26/13 09:28 PM

Tom`s is also a aluminum tube..

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DAVIDG
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: starman876]
      #5942174 - 06/26/13 09:32 PM Attachment (12 downloads)

Tom,
One of the possible reasons why the former owner most likely couldn't get an image was that he didn't have a baffle tube in the primary. Without the baffle tube the image is flooded with sky light.
My secondary is uncoated so the image is dim and I was playing around with it last night and it was very difficult to see an image because the image was swamped with sky flooding since I didn't have baffle tube as well. I calculated I need a 1.5" diameter by 8-5/8" piece of tube for the baffle. I dug around my labs at work and I didn't find anything but a quick search on the 'Net uncovered that Stables sells 1.5" x 15" mailing tubes for $1.99. So after work I stopped off at the local Stables and bought one. So over the next few days I'll make a mounting flange to mount to the inside of the mirror cell, give it a couple of coats of polyurethane to seal it and spray it flat black.

- Dave


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TOM KIEHL
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Reged: 11/17/12

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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: DAVIDG]
      #5942352 - 06/26/13 11:56 PM

Quote:

This scope looks to be based on what is described in Ken Novak's book "Cassegrain Notes". Here is a link to it.
http://bobmay.astronomy.net/CassNotes/#Cass

- Dave


David, I have a question,To the best of your knowledge, Did Ken Novak ever sell complete 6" cassegrain OTA'S ? The reason I ask is that after reading all of " Ken Novak's Cassegrain Notes" , and seeing all the drawings and pictures, included in those notes,they resemble my scope to a "T"..less the Edmunds finder. Maybe a kit by Novak , for sale that the buyer could assemable ? .....Can anyone shed some light on what the scribing's on the back of the mirror might mean? 1st. the word "MIRROR" 2nd. "BLC" and 3rd. "LSTEINLE or possibly L.STEINLE" could L.STEINLE be a mirror grinder that worked for Novak ?

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TOM KIEHL
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Reged: 11/17/12

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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: starman876]
      #5942384 - 06/27/13 12:54 AM

Quote:

If I find everything for that 6" cassegrain I will post a pic. I bought it from the guy who made it in 1978. Looks like Toms, but it in a aluminum tube. Came with a 16X50 finder. No idea where that went.


Johann, What if, your scope and my scope are TWINS ?,,,Then what is the odds that two different ATMer's made the same scope? That is why I think that Ken Novak sold a KIT or sold an OTA..... My tube is Aluminun also...

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Blake Andrews
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: TOM KIEHL]
      #5942387 - 06/27/13 12:56 AM

Regarding the finderscope, I'm pretty sure that it was manufactured in the early to mid-1970s. JTII used that Oval silver with red lettering sticker in 1974.

Looks like a fun project.

Cheers!
Blake


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amicus sidera
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: Blake Andrews]
      #5942730 - 06/27/13 09:24 AM

Took a look at Novak's advertisements in back issues of Sky & Telescope... in April of 1981 the copy stated that he was offering a "new booklet on Cassegrain telescopes", as well as "low-cost convertible systems for dual Newtonian-Cassegrain telescopes". Other ads that I looked at mentioned that he sold mirrors (unspecified as to type), as well as secondary holders and baffles for Cassegrain telescopes.

By "systems" one could infer that he was selling complete optical sets; anyone have an early-1980's Novak catalog for confirmation?

Fred


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TOM KIEHL
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: amicus sidera]
      #5942755 - 06/27/13 09:36 AM

A HA, Thanks Fred, I thought so, Maybe were on to something here....Hope Johann can find his parts to his Cass. and post pictures so we can compare .

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DAVIDG
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: amicus sidera]
      #5942796 - 06/27/13 09:58 AM

As far as I know Novak never sold Cassegrain optics or any type of telescope kits to assemble one. He did sell newtonian mirrors and secondary but I bet they were from Coulter. I have Sky and Tels back into 40's and the only companies that had ads for Cassegrain optics were Coulter, 3B and Mars Optical. Mars turned into 3B. Novak Cass parts were being designed for mostly Coulter Cass optics. As a kid a had a couple of Novak catalogs and they never mentioned a Cassegrain telescope kit. Novak's "Cassegrain Notes" was first published by him in the early 70's, I believe, which is when Coulter started to sell cassegrain mirror sets.
Since your primary mirror is made from a slope sided Corning blank, it was most likely made in the 60's. In the 70's most companies selling telescope mirrors were making them from United Lens blanks were have squared sides and both faces of the disk were the same diameter. So my guess it that it is either a homemade set of optics or 3B made them.

- Dave


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amicus sidera
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: DAVIDG]
      #5942827 - 06/27/13 10:20 AM

The first mention of Cassegrain Notes in a Novak S&T advertisement is in the April 1978 issue, page 73 (Newtonian Notes predates this by several years), but his ads from at least 1975 mention Cassegrain baffle tubes and mirror mounts... as you said, Dave, he almost certainly wasn't producing mirror sets, but reselling those made by others.

Fred

e.t.a.: just on a side note, the feeling of nostalgia I get from going through old issues of S&T can be quite strong at times; ah, for a simpler era... or at least, one in which I'm in my early twenties again!


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Dave M
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: TOM KIEHL]
      #5942840 - 06/27/13 10:28 AM

Not that it means much but didnt you tell me the guy you bought the scope from bought it from a camera shop in Houston 30-some years ago.

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DAVIDG
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: Dave M]
      #5943094 - 06/27/13 01:14 PM

Hi Tom,
I did some calculations on the setup of your scope based on some assumptions of the focal length of the primary being 24", that is an F/15 system ie 90" focal length and the back focal distance being 10". If those are right then secondary to primary distance needs to be 16.84" and the baffle tube for the primary needs to be about 1.5" ID and 8.35" long ( from the surface of primary to top of the tube) The secondary baffle needs to be 2.38" in diameter and 1.90" long.
The secondary to primary spacing is critcial because the correction for spherical aberration is detemined. It also chances the back focal length and small changes in the secondary position are going to make a large change in back focal length. If you can get the exact focal length or radius on the primary and the convex radius on the secondary I'll be happy to recalculate the spacings and baffle dimensions.

- Dave


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TOM KIEHL
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: Dave M]
      #5943391 - 06/27/13 04:32 PM

Thats what he told me.It was in used cond. then, when Dan bought it in Texas.

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DAVIDG
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: TOM KIEHL]
      #5949519 - 07/01/13 11:51 AM Attachment (9 downloads)

Without proper baffling cassegrains suffer badly from sky fogging since light from the sky goes directly into the eyepiece. The cass. I'm assembling from vintage parts doesn't have any coating on the secondary at this time, so the image is dim. Without the baffle tube it is almost impossibe to see the image buried in the all the glare from the sky fog.
Here is a shot of the baffle I made from the Stables mailing tube. I just cut it to length and then took another section about 3" long and split down the slide and cut out a strip so it would fit tightly inside the main baffle and glued it in place. The fit was a little loose in the hole in the primary so I wrapped a couple of turn of printer paper around the end that were saturated with glue. The fit is snug now and I'll give the tube a couple of coats of polyurethane to seal it well and spray it flat black on the outside and line the inside with black velvet flocking paper.

- Dave


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DAVIDG
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: DAVIDG]
      #5949522 - 07/01/13 11:53 AM Attachment (6 downloads)

Here is another shot of the tube showing the end that fits in the center of the primary.

- Dave


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Dave M
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: DAVIDG]
      #5950254 - 07/01/13 07:46 PM

Dave, Nice work on the baffle, will it just be pressed in or will you put a tiny dab of silicon on it for final assembly ?

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TOM KIEHL
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Re: ? MYSTERY ? EDMUNDS ? 6" CASSEGRAIN ? new [Re: DAVIDG]
      #5950320 - 07/01/13 08:36 PM

Very nice Dave, The scope that I have is my first attempt at restoreing a vintage cassegrain, I will need all the help I can get. So far yourself and everyone has been very helpfull in getting me throgh this project that I will start this fall, So I quess I will follow your lead, and this thread when the time comes to do my resto. Buy then hopefully you will have all the bugs (so to speak) worked out of your project, and can give me more tips that can help me on my scope restoration.

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