Celestron 20mm eyepiece

[Sean1070]

So... Bought a Celestron 114 EQ as Xmas present for my son. He unscrewed the eyepiece and the lenses fell out. Is there a diagram on how to correctly assemble the pieces anywhere?

[Mak the Night]

AFAIK The AstroMaster 114 EQ has a 20mm erecting eyepiece (shows upright images on a Newtonian telescope). If it is this one, I wasn't aware that the barrel could be unthreaded from the draw tube. http://www.celestron.com/browse-shop/astronomy/telescopes/astromaster-114eq-telescope

I've looked at the one I have (below) and there is a small objective lens at the bottom of the barrel, although it may be possible to unscrew the objective lens itself I don't know how easily they could be reassembled. 

The Celestron erecting eyepieces are not very expensive (around £25) and can be ordered from Amazon etc. They are principally designed for terrestrial observing. So if you can't put it back together it can be replaced.

http://www.aliexpress.com/item/Brand-NEW-Celestron-20mm-Erecting-Eyepiece-Erect-image-optics-For-All-standard-1-25-Reflecting-Telescopes/32522141969.html

[Dave In Vermont]

Walking in blind regards what type of Celestron 200mm eyepiece (EP) it is, here's a link to an overview of EP-designs:

http://www.quadibloc.com/science/images/eyevar34.gif

And another similar image:

http://www.handprint.com/ASTRO/IMG/eyepieces.gif

And I'll post the images as well -

Dave

[LukeSkywatcher]

I may be wrong, but i think a standard Celestron Plossl is a 2 element EP..........(one concave lens and the other convex)?. From Daves images, it wont be hard to find the right way to put them back.Once back in place..........use a wooden cocktail stick to tighten the retaining rings.

I'm thinking this one:

[Mak the Night]

This shows the objective lens of the 20mm Celestron erecting eyepiece supplied with many Celestron telescopes including the 114 EQ series. I'm guessing that the visible lens surface is very possibly the 'erecting' lens that turns the image the right way up for terrestrial viewing. There are two grooves either side of the insert which may have facilitated the removal of the lens groups. I'm pretty certain it isn't a Plossl design and my guess is that it may be a Kellner type design as it is considered by Celestron to be a fairly wide angled eyepiece 

I think if the other lens pieces could be placed back in their correct order and the final erecting lens placed back in its original position (it may be adjustable) there's a good possibility it can work again.

[ronin]

I think the supplied item will be a Kellner, although it may be a Huygens.

See if you have 2 single lens or a doublet and a single. Then assemble as the set of diagrams above.

That unfortunately is the best I think you will get from anyone.

Fortunately I have not heard of the supplied being a Ramsden otherwise it would be a toss up between Huygens and Ramsden.

Is there a letter of any sort on the eyepiece barrel ?

They often put one with the focal length like H20 = 20mm Huygen eyepiece

[Peter Drew]

I've not had one apart but I was under the impression that the erecting "eyepiece" was a straight through type of roof prism. ? 

[Mak the Night]

According to this Celestron page: http://www.celestron.com/browse-shop/astronomy/telescopes/cometron-114az The Cometron 114AZ has two Kellner eyepieces (10mm & 20mm) they are shown in the pictures in the link. Neither of them are erecting eyepieces and have metal draw tube bodies. Celestron make a few Kellners with metal draw tubes and plastic bodies.

I have the 15mm

FWIW it was one of my favourite EP's for a long time!

[Mak the Night]

I've not had one apart but I was under the impression that the erecting "eyepiece" was a straight through type of roof prism. ? 

It could well be. Usually though erecting eyepieces and inexpensive terrestrial telescopes just have an extra convex lens that initially inverts the image (after the objective) so the usual lens group element turns it back upright. In my experience the 'erecting' lens is inside the telescope between the objective and the subjective.

[LukeSkywatcher]

With Celestron.............it could be either Kellner or plossl. If its a Kellner design..........i wouldnt lose much sleep over it. Get yourself a nice Vixen NPL.

[Dave In Vermont]

A Kellner, or two, served me well back-in-the-day when the top-drawer EP's were Orthoscopics, and my Edscorp 3" F/15 refractor came with Ramsdens. Kellners are fine enough for learning your way around by.

Dave

[LukeSkywatcher]

A Kellner, or two, served me well back-in-the-day when the top-drawer EP's were Orthoscopics, and my Edscorp 3" F/15 refractor came with Ramsdens. Kellners are fine enough for learning your way around by.

Dave

Kellners work well with first scopes for a while. Then we all discover plossl's..........then we all discover whatever. I honestly couldnt tell you what most of my EP's are. TBH, i think they are plossl.

They work well for me....thats all i care about.

[triton1]

I haven't got a clue what mine are either except they are not Naglers

[Mak the Night]

I haven't got a clue what mine are either except they are not Naglers

I have a Nagler, I know it's a Nagler as it has Nagler written on it lol! Seriously though, trying to find information on eyepieces supplied with Celestron telescopes isn't easy. William Optics and Antares tell you exactly what EP's are supplied with their binoviewers. Celestron seem to have Kellners in their least expensive kits, usually a Plossl and a Kellner in the mid priced kits and Plossls in the more expensive kits. 

Looking again at the objective end of my Celestron 20mm erecting eyepiece it does look more like some sort of Amici prism than a convex lens group. I really don't know.

[Sean1070]

Thank You all for your help.  Here is a pic of the eyepiece.  20mm erecting eyepiece from Celestron AstroMaster 114EQ.  there are no other marking on the eyepiece.  I was able to reassemble the lenses the other night and it focuses while in use but it was a guess if i had done it right.  

[Putaendo Patrick]

I guess if your EP does what it's supposed to do, you did a fine job of reassembling it!

On a side note, Kellner EPs are interesting. They are simple to make to they often come supplied with cheaper telescopes. But if the glass and quality is good, they can be quite fine. There used to be an old argument that fewer layers of glass between your eye and the sky was better. However, with the rise of the Plossl etc, good Kellners seem to have disappeared.

But...  I recently read the specifications of a reasonably expensive Celestron telescope, perhaps a Nexstar, costing about 1,000 pounds. It apparently comes with two Kellner EPs! So either Celestron has created a new record for bundling in inferior EPs, or they are supplying something quite interesting. Anyone have any experience of these?

[Mak the Night]

Thank You all for your help.  Here is a pic of the eyepiece.  20mm erecting eyepiece from Celestron AstroMaster 114EQ.  there are no other marking on the eyepiece.  I was able to reassemble the lenses the other night and it focuses while in use but it was a guess if i had done it right.  20151229_195515.jpg

I'm glad you fixed it. I figured it was the erecting EP. I used to use to my Celestron 20mm erecting EP to help centre targets in my Newtonian scope before switching it for another eyepiece. Plus it is actually quite good as a terrestrial eyepiece! I had some great dusk views of Saturn and Venus setting earlier in the summer with it.

[LukeSkywatcher]

Thank You all for your help.  Here is a pic of the eyepiece.  20mm erecting eyepiece from Celestron AstroMaster 114EQ.  there are no other marking on the eyepiece.  I was able to reassemble the lenses the other night and it focuses while in use but it was a guess if i had done it right.  20151229_195515.jpg

Glad it works again. If you got the lens's the wrong way round when putting it back together..........there aint many combinations to try. You would have got there in the end. How many glass lens' are there in it?.

[LukeSkywatcher]

I guess if your EP does what it's supposed to do, you did a fine job of reassembling it!

On a side note, Kellner EPs are interesting. They are simple to make to they often come supplied with cheaper telescopes. But if the glass and quality is good, they can be quite fine. There used to be an old argument that fewer layers of glass between your eye and the sky was better. However, with the rise of the Plossl etc, good Kellners seem to have disappeared.

But...  I recently read the specifications of a reasonably expensive Celestron telescope, perhaps a Nexstar, costing about 1,000 pounds. It apparently comes with two Kellner EPs! So either Celestron has created a new record for bundling in inferior EPs, or they are supplying something quite interesting. Anyone have any experience of these?

I have a Celestron 8SE and it cost me the guts of 2000 euros (brand new). It came with 2 EP's (i think a 10mm and a 20mm). I remember the first night using it. My 1st target was the Moon and while being blown away by the views (due to 200mm aperture over 130mm), i do remember thinking to myself that the quality of the EP's and the views were not as good as with other EP's i own (such as Vixen NPL's). I think you are on to something. Celestron really should bundle their best quality EP's with their more expensive scopes.

My 70mm Celestron refractor "travelscope" came with an erecting prism and the same 10 and 20mm EP's, and that scope only cost me 100 quid brand new from the same retailer here in Ireland.

Mustn't grumble...........but i think you have a fair point.

P.S.~~~every telescope company should stick a free copy of TLAO in the box also.Although if you own more than one scope...........that would lead to you owning many copies of the book.

So scratch that last idea.

LOL.

[Astro Imp]

Celestron really should bundle their best quality EP's with their more expensive scopes.

They won't go down that path, what they're after is getting you hooked then spending more money to improve your views.

A less cynical view might be that people who purchase high end scopes already have a scope and have gone down the ep upgrade route and wouldn't want to be spending more for the scope on eps they already have.

[LukeSkywatcher]

They won't go down that path, what they're after is getting you hooked then spending more money to improve your views.

A less cynical view might be that people who purchase high end scopes already have a scope and have gone down the ep upgrade route and wouldn't want to be spending more for the scope on eps they already have.

Very true and fair point. I just think it would be nice that if you do spend a lot of cash on a scope that you would get EP's worthy of it, even if you already have better EP's.

Cant say ive ever had a complaint about any EP that has come with a Celestron scope apart from the 10mm that came with the 70mm Travelscope. 

[happyCellophane]

Since this is the first result in google on "celestron 20mm eyepiece assembly" and I spent 6 hours of solving this problem and the topic starter was lazy enough not to tell what he did to assembly the eyepiece together, I have registered just to tell others in the same situation what to do.

original guide: https://www.celestron.com/blogs/knowledgebase/i-accidentally-took-apart-my-celestron-20-mm-erect-image-eyepiece-how-do-i-put-it-back-together

In case it gets moved/removed:

 

I “accidentally” took apart my Celestron 20 mm erect image eyepiece. How do I put it back together?

 

Care must be taken to keep the disassembled pieces clean and lenses unscratched while reassembling the eyepiece. Prepare a clean surface on a desk or table for the reassembly.
The disassembled eyepiece will consist of six parts. Top, up or uppermost will mean the eye end of the eyepiece. In the order of assembly from bottom to top, these are the pieces.

The largest part is the main body (barrel) of the eyepiece itself.  The name of the eyepiece is on the top of the eyepiece barrel.  

The second piece is a spacer. It is round and stepped and about .75 inches high. The narrow end will eventually go down into the eyepiece barrel.
The third piece is a lens. It is the bigger of the two lenses of the disassembled eyepiece. (If you look closely you'll see that it's actually two pieces of glass cemented together.)  One side is flat, and one side is curved.
Take the stepped spacer and place it on the table (narrow end down). Place the big lens with the curved side up into the larger diameter end of the spacer.

Next, place the spacer and lens into the eyepiece barrel. The narrow step end of the spacer will go down into the eyepiece barrel. Be sure that the lens is correctly in place on the spacer and not tilting at an angle after you drop it into the eyepiece barrel. Double check that the curved surface of the lens is uppermost.

The fourth piece is another spacer.  It is not stepped on the outside. On the inside, one end is stepped, and one end is beveled. Put the spacer down on the table so the beveled end is upright.

The fifth piece is the second, smaller lens. It also has a curved and a flat surface. Place this lens on top of the spacer (part four) so that the flat surface is uppermost.

Now take the smaller lens and spacer together and place them over the larger lens already in the eyepiece barrel. The inside step on the smaller spacer will fit over the larger lens. Be sure it is seated on this lens.

The sixth and final piece for reassembly is the eyecup.

Gently place the eyecup threads on to the eyepiece barrel and screw the eyecup on the barrel. Be careful not to shift any of the previously assembled parts out of position, as you reattach the eyecup. Avoid cross-threading the two pieces. Tighten the eyecup with moderate but not excessive turning force.

Note: disassembling an eyepiece may void its Celestron warranty.