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Milling tolerances for Jaegers objective cell

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#26 bremms

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Posted 09 February 2013 - 08:21 PM

lens removed from cell.

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#27 bremms

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Posted 09 February 2013 - 08:22 PM

Cell

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#28 bremms

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Posted 09 February 2013 - 08:24 PM

With the retainer.

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#29 bremms

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Posted 09 February 2013 - 08:29 PM

I like the idea of strips on the sides of the cell. Maybe HDPE or Teflon.
Thought you might like these pictures of my cell. It's very simple. And I didn't have to single point any threads..

#30 terraclarke

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Posted 10 February 2013 - 04:37 PM

Great pics Marc of your retaining cell. It looks similar to the one I am making. Thanks for the tips.

Mine too has the collar that slips over and bolts onto the tube, in my case a 76mm Unitron tube. Mine will have a little interior rim the same thickness as the Unitron tube wall where it will sit square and below that there will be 5 holes drilled to secure the cell to the tube. This cuts the aperture of the lens down from 83 to 78 mm. Above this the cell widens to accommodate the wider objective lens. Then the top of the cell will be threaded for the Unitron thread on dew shield. The entire cell assembly will stand 55 mm but 10 mm will be obscured by the dew she's shield when attached.
I built a cradle for the OTA last week which has two opposing Vixen dovetail bars 8 inches long, so the scope can be mounted on my Vixen StarGuy or my CG4 or my Unistar Deluxe. The bars are also drilled and tapped with 1/4 20 holes so I can also put the scope on my Vintage Professional Jr. Panhead 16mm motion picture tripod.

When this project is finished I will begin planning my Jaegers 4 inch F15.

#31 bremms

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Posted 11 February 2013 - 07:16 AM

Did you go and buy a Zeiss Terra? They are really sweet. I do poke at them on occasion as some owners may stretch the truth about capabilities. Truth is, they really are very good. An old friend had an AS 80 840. It had superb optics and mechanics.

#32 terraclarke

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Posted 11 February 2013 - 10:09 AM

Hi Marc,

I did. A good friend told that basically, when a good deal comes along, you've got to strike while the iron is hot. Not in those exact words but you get his meaning. It was way to good of a deal to pass up so I did just that. I haven't got it yet but should have it in a week or so. Its a Telementor T1 which was exactly the model I wanted, the one with the helical focusor, and its on a beautiful T2 mount, the one with all the pretty blue and red. I am very excited. I will post pictures when I receive it.

Terra

#33 Geo.

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Posted 11 February 2013 - 11:21 AM

I was able to just fit an 83mm Jaegers into a Vixen 80mm cell. Not sure what that says.

#34 bremms

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Posted 11 February 2013 - 01:04 PM

If the TM was a good deal, yes strike while the iron is hot. I like the T1, the T2 sliding lens thing seems a bit odd. I never used a T2, maybe it works great.

#35 terraclarke

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Posted 11 February 2013 - 03:52 PM

I would be afraid that the sliding objective could more easily get out of collimation?

Terra

#36 bremms

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Posted 11 February 2013 - 04:39 PM

Exactly.. but it is German. They probably spent a lot of time engineering that properly.

#37 AllanDystrup

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Posted 12 February 2013 - 04:39 AM

The T1 helical focuser has a travel of 35mm, while the T2 internal tube R&P has a travel of 100mm; Both have plenty of back-focus, eg for for a diagonal + bino. The helical focuser has a reputation for being very smooth (I've never tried it), but as an owner of a T2 I can testify that the internal R&P is also *very* precise and robust - I've never heard of any problems with that design.

The Telementor and T-mount is a uniquely innovative and well crafted example of astro engineering, and I'm sure you'll fall in love with that baby when you hold it in your arms...

#38 Astrojensen

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Posted 12 February 2013 - 05:08 AM

Now of course I've loaned my Telementor 1 to a friend, so I don't have it at hand, but from what I recall, the helical focuser has a travel of 55mm. The back focus is about 140mm. I couldn't reach focus with my Baader Maxbright and T2 diagonal without corrector, but with the 1.5x (sold as 1.7x) corrector, it was fine. The Telementor 2 / Telemator has the internal focuser, which works extremely well. It has about 160mm back focus. I can reach focus with the Baader Maxbright and T2 diagonal without corrector with some eyepieces, but others require the 1.25x corrector.

The T-mount is almost without equal. The setting circles are 4.5" in diameter and highly accurate. You can use them to polar align in daylight with enough accuracy to use them to dial in stars and planets in daytime. I've used my Telemator to split Castor in the early afternoon.


Clear skies!
Thomas, Denmark

#39 terraclarke

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Posted 12 February 2013 - 09:06 AM

I am sure that both the T1 and T2 focusing mechanisms are excellent. I am just used to the eyepiece moving rather than the objective (although I do have 1 Mak, a Lomo which is related to post-war Zeiss and works wonderfully as well). I also have heard how wonderfully the helical focuser works. I can't wait to receive it. The mount too. I will start its own thread when it comes.

#40 Astrojensen

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Posted 12 February 2013 - 02:44 PM

When you first see or use the Telementor 2 or Telemator with the internal focuser, your first thought is "what the heck is going on", but later you learn to value it, as it makes for a rock-solid bomb-proof attachment of heavy accesories, without having to worry about focuser slip and sag.

Very few 60mm's can take a binoviewer+diagonal+adapters+2x25mm LER Zeiss eyepieces. Or a 30mm ES82 2" eyepiece and 2" Baader diagonal.

The only negative I can say about it is that it's a little too coarse, but other than that, it works like a dream. Here Zeiss was *really* thinking outside the box and came up with something truly brilliant and elegant. An engineering masterpiece.


Clear skies!
Thomas, Denmark

#41 terraclarke

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Posted 12 February 2013 - 03:45 PM

I could certainly appreciate that. Same problem often when attaching a heavy h-alpha train to the back end of the telescope.

Terra

#42 Sasa

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Posted 12 February 2013 - 03:53 PM

The only negative I can say about it is that it's a little too coarse, but other than that, it works like a dream.


I would add also another slight negative of the internal focusing mechanism. Due to double tube, the OTA is quite heavy (definitely, it feels heavier than for example similarly sized ED100). But it is more than paid back by the option of hanging anything on the eyepiece side without worrying about sliding focuser.

#43 Astrojensen

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Posted 12 February 2013 - 04:26 PM

Actually, the inner tube is very light and adds very little total weight. The majority of the weight comes from the very thick-walled heavy duty outer tube. I've had mine taken apart to regrease the focuser (a five-minute job) and was surprised by how light the sliding tube is.

Given the huge advantage of not having to deal with any focuser issues whatsoever when using heavy accesories, it's a bit of a mystery to me why not more manufacturers have used this design on their 50mm - 70mm scopes. An 80mm is big enough to support a beefy 2" focuser, but on the smaller scopes it might make more sense to make a lightweight inner focuser for the comparatively lightweight objective.

It certainly made sense to Zeiss.


Clear skies!
Thomas, Denmark

#44 Sasa

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Posted 13 February 2013 - 04:38 AM

Good to know Thomas. I haven't taken the inner tube out yet. I just thought that the inner tube was a part of reason why the telescope felt so heavy.

#45 bremms

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Posted 13 February 2013 - 08:13 AM

The outer tube is probably heavy since it needs to be bored and maintain shape for smooth focusing. These were also meant as teaching instruments, so were probably made a bit rugged.

#46 terraclarke

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Posted 26 February 2013 - 01:36 PM

The work continued last week on the replacement cell to fit a 83mm Jaegers objective lens to a Unitron optical tube. After the rough lathe work was finished and the cell was still attached to the aircraft grade aluminum stock we made a 3-D solid model in CADD based on all initial measurements and then created a plastic polymer 3-D model of the cell to see how it would fit with the existing tube, dew shield, and objective lens.

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#47 terraclarke

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Posted 26 February 2013 - 01:40 PM

The "real" 3-D plastic model allowed us to make final adjustments before cutting and milling. Here, the interior has been finished to smallest i.d. and now we are opening up the end of the cell which will fit over the optical tube. It will eventually be bolted in place. There is a small rim against which the flint element of the objective will rest. That rim corresponds to the smallest i.d.

Terra

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#48 terraclarke

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Posted 26 February 2013 - 01:42 PM

Now the exterior of the tube is being cut down from that end to its desired diameter.

Terra

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#49 terraclarke

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Posted 26 February 2013 - 01:47 PM

Now the cell is cut from the remaining stub of aluminum working stock.

Terra

#50 terraclarke

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Posted 26 February 2013 - 01:50 PM

Here's a picture of the cell cut off from the stock.

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