657 replies to this topic

[clamchip]

Throughout the life of the Edmund catalog up until around 1976 you could buy "High Quality Refractor Objectives" mounted in a cell or unmounted. The 3"f/15 and 4"f/15 are the same as what came on the 3 and 4 inch refractors.

And then we have the 5 inch lens, with it's different cell and a focal ratio of 14.2, and Edmund didn't make a finished 5 inch telescope.

This 5 inch lens is lumped in with the 3 and 4 lenses in the catalog just like it was a member of the family.

Does anyone know anything about the Edmund 5"f/14 lens?

Rather than the steel cell with screw in retainer ring the 5 has a cast aluminum cell with 3 blocks to

retain the lenses.

The blocks each have a single machine screw to hold them, and the cell also has a

flange with collimation screws.

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Edited by actionhac, 05 December 2015 - 01:39 PM.

[clamchip]

Edmund supplied this split ring for mounting the cell to your tube. Its split to give you a little flexibility

installing it inside your 7 inch tube, this is the way Edmund designed it to work, inside a 7 inch tube, which

is a pretty large tube for a 5 inch lens.

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Edited by actionhac, 05 December 2015 - 01:40 PM.

[clamchip]

 Here's the usual Edmund ink stampings on the lens edges to help you index and get the elements

facing the correct direction.

I woke up this morning thinking about this lens and I think it might be high time we test this lens

in a telescope under the stars and planets yes I think so! I'll scrounge around here and see if I can

dig up a tube and focuser.

Robert

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[ScottAstroNut]

This sounds like a great project.  Can't wait to see how it turns out.  I'd bet that the Edmund lens is a real performer.

[Spectral Joe]

At my last job we had two of these lenses, FWIW they were both slightly undercorrected. I thought the cell design was a bit of a kludge and would have made  new one if they were used more often.

[clamchip]

I've come up with a plan for the focuser.

I'm going to barrow half of a ESCO cell I have so I will have the focuser flange that fits inside a 7 inch

aluminum tube, and I have a Jaegers focuser that someone drilled 4 holes in that will make it easy to

attach it to a plate.

Now I just need to make a plate to join these two parts together.

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Edited by actionhac, 05 December 2015 - 03:07 PM.

[clamchip]

This might come in handy for someone putting together a Jaegers 6 inch refractor, it uses a 7 inch tube also

if I remember correctly, and the Jaegers 7" focuser is very difficult to find these days.

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[clamchip]

The bolts are larger than they need to be but I used the existing holes that are all 1/4".

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[Joe1950]

Nice work, Robert. That's going to be some scope.

 

On the lens photos, I see some indexing lines on the edges of the two lenses. They appear about 1/4" displaced. I don't think that will make any difference however.

 

Very exciting.

[clamchip]

I noticed the indexing lines arn't lined up too, I thought I would try it out first.

I'm very excited about this project, I've owned this lens for 7 years and finally getting around to

doing something with it and its happening!

[clamchip]

I'm looking for information on the Edmund 5" lens and found only this 

so far in about one hour of search:

http://www.cloudynig...ch#entry6132498

I'm surprised at the rarity of this Edmund item.

The price of this lens with cell in the Edmund catalog with the 4 inch for comparison:

'62 $150.00 ($80.95)

'69 $173.50 ($91.50)

'73 $269.50 ($159.50)

'75 $345.00 ($185.00)

'77 and '78 available without cell only: $295.00 ($155.00)

 

Robert

Edited by actionhac, 06 December 2015 - 12:37 PM.

[clamchip]

I found a tube today and I didn't even need to leave the farm.

I have nowhere to buy telescope tubing locally I usually order it from Hastings.

It has a few holes in it because it was going to be a Newtonian that someone never finished.

Its 60 inches long and the lens has a focal length of 72 inches so that leaves 12 inches for

miscellaneous doodads like a focuser and a star diagonal. 

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Edited by actionhac, 06 December 2015 - 05:30 PM.

[clamchip]

OMG I got a lot done today!

I'm so excited about this project!

This is a 5 inch Edmund Scientific refractor!

I thought I would see a McDonald's on Mars before I ever saw stars through this thing!

It won't be too much longer!

 

Robert!

[Lew Chilton]

Robert,

Good job! You'll probably have to add some weight to the inside of your back plate, just as I had to do when I mounted my 6-inch f/15 Jaegers objective in a 7-inch i.d. aluminum tube many years ago.

Edited by Lew Chilton, 06 December 2015 - 09:37 PM.

[clamchip]

5"f/14.2 has a CA ratio of 2.84 so I guess I should expect to see some color.

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[Chuck Hards]

This might come in handy for someone putting together a Jaegers 6 inch refractor, it uses a 7 inch tube also

if I remember correctly, and the Jaegers 7" focuser is very difficult to find these days.

 

I have the Jaegers casting for the 2.7" focuser and 7" tubing.  I was thinking of stealing the focuser tube & rack, and knobs from one of my 2.7" focusers for 5" tubing, and sticking them on the 7" casting.  Could also just make a new focuser tube & rack for it.

[clamchip]

The counter-cell is now installed in the end of the tube.

The nice thing about having a 7 inch tube for a 5 inch lens is the tube can have

very deep baffles for trapping stray light, and no reflected glare from the interior wall of the

tube since its well out of the way.

 

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[clamchip]

Here is the lens sitting loose on the counter-cell.

Next I'm going to slide some flat black art paper tubes

inside the telescope tube to control unwanted reflections for the lens test.

And then I will install the focuser.

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[Joe1950]

Robert,

 

When you get a chance, please check this post in 'Refractors' CN:

 

http://www.cloudynig...refractor-lens/

 

The OP has a 5" refractor lens that looks almost just like the one you have. But, he says it is in a steel cell. Did Edmund, to you knowledge, ever sell their acros mounted in steel?

 

Thanks.

Edited by Joe1950, 10 December 2015 - 05:44 PM.

[Bomber Bob]

I like the scopes I have, but a 5 model Edmund collection - 3" & 4" refractors plus 3" 4.25" & 6" reflectors - would correspond to my eclectic mix, and take up about the same amount of floor space.

[clamchip]

Robert,

 

When you get a chance, please check this post in 'Refractors' CN:

 

http://www.cloudynig...refractor-lens/

 

The OP has a 5" refractor lens that looks almost just like the one you have. But, he says it is in a steel cell. Did Edmund, to you knowledge, ever sell their acros mounted in steel?

 

Thanks.

Thank you very much for the link Joe, I replied to it over there in refractors.

Yes Edmund used steel cells for the 3 and 4 inch f/15 refractors their entire life up to the late red tubes

so a steel 5 inch cell wouldn't surprise me, although mine is aluminum.

The key to whether his lens is a Edmund Scientific is the focal ratio of his lens.

If his lens is the very unusual f/14.2  (71" inches) it more than likely is Edmund. I mentioned this in my

post and will be curious what he finds.

 

Robert

[Joe1950]

Thank you, Robert. The build of the cell looks so similar and even some of the marks I can barely see on the edge appear familiar.

 

Good post to him and hopefully this will help determine the make. 

 

joe

[clamchip]

I finished the telescope and had only a few minutes to find out 1) where the focal plane is so

I know what I need in the way of extensions, and 2) how far off the collimation is because the

tube end is not perfectly square.

I did get some pictures! here is the art paper interior liner which is dead flat.

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[clamchip]

The lens.

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[clamchip]

The focuser at infinite focus. I knew the tube was to short and I cut it off twice and its still too short.

I would like to end up with the focuser tube back inside

the focuser and a 4 inch long extension.

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Edited by actionhac, 11 December 2015 - 07:55 PM.