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Edmunds 3" Reflector

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#1 dcullen

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Posted 19 January 2013 - 11:19 PM

A while back I was given a Edmund's 3" reflector and I sort of just put it in a closet. Recently I decided that it ought to be checked out and maybe used. Here is what it looks like now.
https://picasaweb.go...51cOIRFbhTD4...

https://picasaweb.go...51cOIRFbhTD4...

Anyway, I pulled the very dirty mirror and carefully following direction found online, cleaned it. I was surprised and happy to find only a few scratches and rub marks.

I've also determined that there are a couple of missing pieces. There is no focusing mechanism. It fairly obvious that there should be a tube the friction fits into the focuser base. And there are no eyepieces. I guessed that it was designed to work with .965 eyepieces.

I collimated it and checked out the moon by holding a 1.25 eyepiece over the focuser base. I was pleasantly surprised by the crisp image while hand holding the eyepiece.

Well I found a copy of Edmund's catalog #623 that has the same model telescope the "Space Conqueror" and that revealed that it would have come with 1/2" Ramsden eyepiece and a barlow. But the real jewel is item 60,070 .917 focuser. It had a phenolic impregnated tube for focusing and took .917 microscope eyepiece.

So I have no focusing tube and no .917 eyepieces. So my first thought was to replace the focuser with a basic 1.25 focuser. That leads to a whole chain of changes. The existing secondary is a single stalk that is attached to one of the mounting screws. I also noticed that the 26mm eyepiece I used came to focus much lower than a regular 1.25 focuser would. So if I use the 1.25, I'll need to shorten the back of tube to relocated the mirror.

The more I think, the less I like this idea (and I've already ordered a focuser) I'm looking at a new focuser, new spider or trying to cobble something together for the secondary. And then I'd have to cut the original tube.

Now I'm thinking about what to use as a focuser tube. I'm wondering if I can piece something together using pvc pipe and perhaps using .965 eyepieces. That would involve the fewest alterations and would still be a usable telescope

Any advice or opinions :question:

#2 apfever

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Posted 20 January 2013 - 05:07 AM

Doug,

No need to shorten the tube. You can drill a few new holes and just move the primary up to a closer location. This will preserve the tube and original mounting location. Multiple sets of holes for different primary locations are not uncommon in Newtonians. The old Edmund reflectors used a 1.25" focuser that has the mounting hole for the single stalk secondary. You can probably find one by placing a WANT ad. You could put an ad in both CN and AM.

Your scope looks to be either modified or a very early version of the Palomar Jr. or some other side line offering. I've never seen one quite like it, but I do remember this exact scope showing up here before, possibly as an ad. Do you have any idea of age or history? The finder looks like a paper roll tube.

#3 rdandrea

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Posted 20 January 2013 - 03:15 PM

Brings back memories--that was my first scope.

The focuser is a slide-type. There was a phenolic tube that slid up and down in the plastic housing to focus.

It was designed to take .917" eyepieces. It came with 1", 1/2" and 1/4" Ramsdens and a Barlow that was a plano-concave singlet, held in place by split rings above and below. It was adjustable.

If you can find the phenolic insert or some other slider, 23 mm microscope eyepieces will do the trick for you. They are pretty widely available.

#4 GeneT

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Posted 20 January 2013 - 04:14 PM

When I was very young, I drooled over the telescope ads for the Edmund 3.

#5 dcullen

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Posted 22 January 2013 - 12:01 PM

Got an idea for the focuser from Ray Cash's DOB page. Mount a 2" to 1.25" adaptor to teh tube.

#6 actionhac

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Posted 22 January 2013 - 01:37 PM

I have the same telescope.
Unfortunately I'm missing the entire mount. The odds are very good I'll find one someday, hopefully.
I do have a complete focuser though and I have taken some pictures with the idea these may be of some use to you.
I recently saw a picture of this scope in a magazine but I can't for the life of me remember where. I think it was late 50's when Edmund printed the constellations on this model, normally it's just plain white.

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#7 actionhac

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Posted 22 January 2013 - 01:45 PM

Here is the focuser.
The eyepiece is standard .917 microscope size. I'll bet you could go on ebay and find Edmund Scientific microscope eyepieces if you really want originality.

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#8 actionhac

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Posted 22 January 2013 - 01:50 PM

Exploded view.
The focusing tube is impregnated fiber but shellaced cardboard should do. Craft store or hobby shop or model rocketry should have 1" outside diameter tube.

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#9 actionhac

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Posted 22 January 2013 - 01:53 PM

Tube is 2 1/2" long and 29/32" inside diameter with a small piece of felt for a snug fit for the eyepiece barrel.
Robert

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#10 actionhac

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Posted 22 January 2013 - 03:03 PM

I found it in "A Guide To Astronomy" Fawcett 1958. This is the only picture I have found the 3" with the constellations on the tube. Sitting on the page here with some pretty cool company in 1958.

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#11 rdandrea

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Posted 22 January 2013 - 03:49 PM

My 1961 model didn't have the constellations or Edmund name, just plain white, so maybe that will help narrow down the date. It might be helpful to the OP if you can put a set of calipers on the focusing tube. Knowing the OD might help him find a substitute. Is it really 1"? That would make the tube thicker than I remember.

A "D" class model rocket engine is 15/16" wide. That makes me think that Estes BT-50 body tube might be the right size, although it will need to be impregnated with something to make it stronger.

#12 actionhac

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Posted 22 January 2013 - 04:03 PM

Yes its 1" outside diameter. 29/32" inside diameter. The .917 eyepiece would be loose in the tube without the felt. 2 1/2" long.
It always surprises me how all us classic telescope gals and guys know model rocketry. I guess we all came from the same mold. I mean the "baking mold" not the green slimy stuff!

Robert

#13 mikey cee

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Posted 22 January 2013 - 04:16 PM

My 1959 3" has no constellations either. I have two focus tubes one for the 1/2" eyepiece and another longer one for the barlow lens. Wow 60x up to 180x! They even misprinted the power range in my 1959 catalog too!:shocked: Mike

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#14 rdandrea

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Posted 22 January 2013 - 04:21 PM

It always surprises me how all us classic telescope gals and guys know model rocketry.


I guess we're just space geeks.

#15 dgreyson

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Posted 22 January 2013 - 04:37 PM

Model rocketry, Trains and Ham radio seem to be recurring themes here. the Post Sputnik science craze of the 50's to 60's perhaps.
I wouldnt be surprised if some of the gentle readers of Classic Telescopes also liked microscopes as well. The Edmund Scientific catalog was required reading for a lot of folks.

#16 will808

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Posted 22 January 2013 - 06:03 PM

These telescopes introduced many thousands of kids to astronomy...i have one of these and used it as recently as 2 years ago,it's fine on the moon & Jupiter...a little hard to use but it's only $30 and they kept it at that price for decades!

#17 Jim T

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Posted 22 January 2013 - 07:27 PM

I picked one of these (plain white tube) up at a garage sale about 3-4 months ago for $15. It is nearly complete. Missing just the barlow (this model only came with ONE eyepiece at the time). I really wish it had a 1" eyepiece. At f/10 with a narrow-AFOV 1/2", it could use a wider field. I don't think it really needed a 2x barlow anyway.

I hope that I "saved it" for use by some kid that wants it. Although I'd refuse to get it over the original $30 cost. I'm sure that I'll find a good home for it as it is.

Still, always cool to see these from the past. My first scope was the Edmund 4.25", which I still have in complete original form.

#18 dcullen

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Posted 23 January 2013 - 03:25 PM

Thanks for the pics and dimensions actionhac. Little details like the felt strip help alot.
Looks like a BT-50 body tube will work. Maybe juice up with some CA or Epoxy. Now, there is that temping Karl Zeiss microscope eyepiece on fleabay.

#19 mikey cee

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Posted 23 January 2013 - 05:42 PM

The .917 eyepiece would be loose in the tube without the felt. :lol:Ahh yes the little felt strip. After more than 50 years I still can remember keepng it "fluffed up" to hold the eyepiece in place. But the barlow tube had no felt. :confused:I bet I had that eyepice apart a dozen times trying to keep it perfectly clean too. By the way the ramsden lenses sat at the ends of a teeny weeny phonolic tube just like it's bigger brothers. :p Mike

#20 DAVIDG

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Posted 24 January 2013 - 09:35 AM

Here is a spot diagram for 3" f/12 spherical mirror for a field of view that 1/2 degree in diameter ie the size of the full Moon. It is diffraction limited to the edge of the field and as on axis has Stehl ratio of 0.994 and wave rating of 1/27. This is why these long focus spherical mirror of modest aperture can really perform. This is better then a typical 3" f/15 refractor. What you need to be sure of is that the diagonal is optically flat. Many time they used very poor quality diagonals that wreck the image quality.

- Dave

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