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Edmund Scientific Telescope help

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#1 Druchti

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Posted 06 January 2021 - 09:04 PM

Hey , I'm new to the forum and new to telescopes! I recently stumbled upon an old Edmund Scientific Telescope and brought it home with me. I thought it was to cool looking and too interesting to pass on ! I'm not for sure what it is exactly but from the little I've looked around it seems to be a 4 inch f/15 refractor? It's not complete and was wondering if parts for these are still available ? The mount itself is all there i believe and everything moves freely . The scope tube looks to be all straight no dents or dings in it . But the glass is not mounted in it. I have the lenses and a few other parts that came with it but not sure exactly everything I need to put this back together. Is this scope of any quality and worth the effort to get it back into working order ? Any information on this scope would be greatly appreciated! 

Thanks 

Derick 

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#2 Druchti

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Posted 06 January 2021 - 09:06 PM

Mis parts that came with it 

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#3 Druchti

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Posted 06 January 2021 - 09:07 PM

More photos 

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#4 Bomber Bob

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Posted 06 January 2021 - 09:16 PM

If that's all the parts, you're missing the focuser.  Tough but not impossible to find an original one; or, like some other owners, adapt a modern focuser to it.


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#5 Druchti

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Posted 06 January 2021 - 09:17 PM

The tube length is 50.25" and 4" across 



#6 Russell Smith

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Posted 06 January 2021 - 09:17 PM

Welcome to cloudy nights.
Your in the right place to get some help with that beauty.
One thing I see is that 12.5mm eyepiece does not belong to that telescope.
Russ
3 inch f16ish?


Edited by Russell Smith, 06 January 2021 - 10:07 PM.

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#7 Druchti

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Posted 06 January 2021 - 09:21 PM

If that's all the parts, you're missing the focuser.  Tough but not impossible to find an original one; or, like some other owners, adapt a modern focuser to it.

Ya that's everything that came with it ..Would I be better off finding the original or would there be an advantage on mounting a modern focuser to it ? 



#8 Russell Smith

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Posted 06 January 2021 - 10:03 PM

You are going to have to put the objective back in its cell, put together correctly and with the proper spacers.

As Bomber Bob said finding an original focusing assembly my take some doing.

I personally would post a wanted ad and try to find one and of it's a no go then purchase a modern replacement and keep searching. 

If you take some time to search past threads you will find all the information to put the objective back.

Russ



#9 apfever

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Posted 06 January 2021 - 10:31 PM

That's a great scope. Intact and in decent shape worth at least a few hundred bare bones (with a focuser).  An original focuser will be a little tough to locate but not impossible, a decent chance with a 'want' ad.  A replacement focuser would be fine considering it has nothing.  A replacement would probably be an upgrade but the original will add collectability value.  Make sure any replacement focuser is for 1.25" eyepieces and NOT the smaller eyepieces with 0.965" barrels. 

 

Don't clean the lens'.  That is a bit of an art and always a careful job. No windex and paper towel action please. The lens look nice.


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#10 YourNotSirius

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Posted 06 January 2021 - 10:53 PM

It appears that you also need the objective lens assembly for the finder scope. I don't see it in any of the photos. If so, it will be easier to locate an entire finder scope from that time period. They show up here in the classifieds on occasion. You can also post a want ad for it. The same for the focusing unit although, I do agree that a more modern unit will make using the scope a more pleasant experience.

 

You will soon discover that the EQ mount is quite solid. It appears that you may have even managed to get the clock drive with it. At least, part of it seems to be there. Again, the photos don't show enough detail.

 

As advised by others here, be very careful with the lens elements. They SHOULD have witness marks on the edges to show which way they are to be assembled. If not, it will take some time to study the assembly to determine which way each element must face. If you belong to, or know of, a local astronomy club then one of the members may be familiar with lens assemblies and can help. Provided, of course, that you even need such help. Additionally, there are plenty of lens cleaning instructions in the forums to help you clean it, if you so choose but, which appears to be unneeded.

 

Good find! Enjoy!

 

Q


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#11 ccwemyss

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Posted 06 January 2021 - 11:10 PM

It would help if you posted a picture looking down from the other end. It looks to me, in the shot from the back end, that there is already glass in the front, with a set of spacers. So the loose glass might be a replacement lens. The lens does appear to have a set of spacers (the little foil tabs). Don't lose them. Their thickness is precisely set to optically separate the two pieces of glass by just the right distance. 

 

Chip W.


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#12 Druchti

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Posted 06 January 2021 - 11:12 PM

You are going to have to put the objective back in its cell, put together correctly and with the proper spacers.
As Bomber Bob said finding an original focusing assembly my take some doing.
I personally would post a wanted ad and try to find one and of it's a no go then purchase a modern replacement and keep searching.
If you take some time to search past threads you will find all the information to put the objective back.
Russ

Sounds like I have some searching ! I'll throw up a wanted post for an original. So Is this a 4 inch f/15? And am I just looking for a edmund 1.25" inch focuser for a 4" f/15 . I'm very green to all this ..I just want to make sure I'm wording my wanted post correctly .

#13 Druchti

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Posted 06 January 2021 - 11:31 PM

It would help if you posted a picture looking down from the other end. It looks to me, in the shot from the back end, that there is already glass in the front, with a set of spacers. So the loose glass might be a replacement lens. The lens does appear to have a set of spacers (the little foil tabs). Don't lose them. Their thickness is precisely set to optically separate the two pieces of glass by just the right distance.

Chip W.

No glass in the objective end ..I'm assuming what you guys are calling the cell is the black end piece? So both lenses sit on top of eachother in the end of that ? There are threads on the end of it ..is there a ring that screws in there to hold the lenses together then that Im missing?

#14 Druchti

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Posted 06 January 2021 - 11:34 PM

Objective end 

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#15 Druchti

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Posted 06 January 2021 - 11:37 PM

I have all the parts for the finder I believe ..I was in the process of trying to figure out how it went together and missed it in the photo . The glass is very dirty in the finder scope ..can I clean this or is the same care needed on this as the large lens?

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#16 Druchti

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Posted 06 January 2021 - 11:50 PM

There are marks on the lenses .. small dot arrangements on the edges and the thicker lens has a faded 23 mark on one edge also ..can you guys point me to a thread on putting the cell back together ? Or how would I word the search for that ..everything I've tried hasn't brought much of anything yet ..I don't believe I know the right terminology for what I'm trying to do  🤦😅 definitely exited to try and get this thing back together and working again! ..thank you all for the help so far 

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#17 Kasmos

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Posted 07 January 2021 - 01:40 AM

In post #2 the part on the far right is the dewshield/lens shade for the finder's front lens (objective).

 

The link below is to a diagram that shows the typical way that the crown and flint lenses go together. The side of the crown lens with more curvature faces the flint lens.

 

https://www.cloudyni...ada/?p=10785074

 

The side with three little spacers (that appear to be still attached to one of your lenses) faces the other lens. The dots on the side are likely alignment marks to match their rotated position. I'm fairly sure the two dots line up But wait for a Edmund expert to Chime In to confirm that.

 

Google cleaning telescope objectives, or lenses and read several articles before doing it. Be very carefull not to knock off the small spacers while doing so.

 

Here's one:

 

https://www.televue....page.asp?id=103

 

Perhaps someone can explain the following better or guide you to a good source.

 

The most delicate procedure is taking them out or placing them into the objective cell.

The cell needs to be removed from the main tube to do it.

Don't try to put them in by hand as you can easily get them cocked and they can get stuck and it will lead to chipped edges.

9TE-Lens.jpg

This is a small objective and cell with a spacer ring but it's the same procedure.

They are placed on a glass or something with a soft cloth or lens tissue on it and you lift the cell to install them. 

Then install the lens retainer not shown.

You do the opposite to remove them.

 

Some cells have the retainer on the front side and others the back, so you need to keep that in mind to put them in correct.

Your problem, it appears you are missing the lens retainer.


Edited by Kasmos, 07 January 2021 - 01:54 AM.


#18 dgreyson

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Posted 07 January 2021 - 09:56 AM

If you are missing the retainer ring for the objective, a replacement can be machined. Machine shops are not cheap however and you may find that the cost may exceed the value of the scope if you don't shop around carefully. A deburred and polished ring cut from a slight larger piece of any sort of tubing can be cut out on the side until you can friction fit it into the cell. A few small dabs of hot melt glue will insure it doesn't slip and let the objective get broken.

Fitting a Plastic Meade refractor focuser with shims is an extremely cheap interim solution just to get it usable enough to see if the objective is installed right and try it out a bit. Another makeshift Jerry rig is to cut a wooden plug to fit in the back so that a good focuser can be bolted on. These field expedients would let you halfway use the scope while you undertake a lengthy search for original or at least a better replacement. Good luck.
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#19 davidc135

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Posted 07 January 2021 - 11:55 AM

The objective looks to be 4'' diameter? Before putting in a focuser I'd check the focal length which can be done by measuring the distance from the objective to an image of the sun, maybe with a second person's help.

Alternatively, indoors, if the objective is equidistant from an object eg a torch and its image then the total object to image distance equals 4x focal length.

 

The two lenses that make up the objective are called the crown which faces out and the flint made from a noticeably denser glass. The first crown surface R1 should be less strongly convex than R2 which will be separated from the concave R3 of the flint by the three spacers. R4 should be weakly convex. and facing the eyepiece. I expect this corresponds to the dots. The edges of both lenses can be held together temporarily by a masking tape wrap.

 

David



#20 ccwemyss

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Posted 07 January 2021 - 12:36 PM

It's hard to see from the photo if there are threads on the inside of the front part of the lens cell. Is it threaded? I see the edges of two circles inside of it. Is one the tube and the other a machined lip that it is butted up to? Or is there a threaded ring inside of the cell? On a similar cell, I have to take the cell off of the tube by removing the three screws, and then there is a ring that goes in from the back to hold the lens in place. 

 

Chip W. 



#21 clamchip

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Posted 07 January 2021 - 12:43 PM

I would check and see if the lens fits in the cell to make sure it will.

If I remember right the Edmund 4 inch lens is 4.00" and most other 4 inch lenses

are typically larger than 4" so when mounted in the cell the clear aperture is 4 inches.

The dots are interesting, never seen that before, a good idea if it's how I think

it is:

1 dot is the sky side of the crown R1

2 dots the eye side of the crown R2

2 dots the sky side of the flint R3, and should have the 3 spacers stuck to it.

3 dots eye side of the flint  R4  the closest surface to your eye when the lens is in the telescope.

I would also line the dots up when installing the lens in the cell.

 

Robert


Edited by clamchip, 07 January 2021 - 12:44 PM.


#22 Druchti

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Posted 07 January 2021 - 07:43 PM

Thank you that helped allot I do have a question tho you guys said that the cell should be removed from the main tube to put the lenses in witch definitely looks like the way to do it .but if you look at my objective end picture my cell is bolted to the main tube from the inside . philips heads inside and then a nut on the outside ..once I put the glass into the cell how do I put the bolts back in ..I'd have to reach all the way through the length of the tube to get them back in then ..my arms aren't that long ..lol..To me it would make allot more sense if they had it threaded so you can just crank your bolts in from the outside

#23 ccwemyss

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Posted 07 January 2021 - 07:53 PM

On my similar cell, the holes in the tube are tapped, so screws can just go in from the outside. This cell may be different. It can't hurt to take it out and see what's there. It may indeed be a front-loading cell with a missing piece. But if it is rear-loading and the ring is actually in there, it will save a lot of effort. 

 

Chip W.



#24 clamchip

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Posted 07 January 2021 - 07:58 PM

Unfortunately with the Edmund you must install and remove the lens elements with the

cell attached to the tube.

You have the equatorial so what you do is point the telescope at the ground, tube vertical. 

Then you sit in a chair so you have a good working height with the mouth of the lens

cell.

Place a cotton napkin, t-shirt, dish towel, over your fingers, place the lens elements on the

cotton and carefully ease them squarely up into the cell until they bottom out inside the

cell.

Then you hold the lens there while you insert and screw in the lens retainer ring.

Flip the tube 180 deg and adjust the retainer ring so it lets the lens just barely rattle when

shaken.

Or if you feel better about inverting the tube to install the retainer ring go ahead.

Disassemble is the opposite of above.

Be very careful when raising the lens into the cell, and when lowering the lens out of the

cell that you go slow and square, don't let the lens tilt inside the cell then you risk getting

the lens caught cocked in the cell threads and a clamchip.

 

Robert 


Edited by clamchip, 07 January 2021 - 08:26 PM.

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#25 Druchti

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Posted 07 January 2021 - 08:29 PM

Are there any other sites that would be worth looking for vintage parts on? I just registered for the forum and they won't allow me to post any classified/ wanted ads for 30 days ..kind of puts a damper on my search . I definitely do not have the retainer ring and will need to track down a focuser and probably a dew shield . Do the drive motors for these come up often ? 


Edited by Druchti, 07 January 2021 - 08:32 PM.



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