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Jaegers Lens spacers

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#1 Z28500

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Posted 25 March 2012 - 03:04 PM

Any knowledge out there about the masking tape that Surplus Shed says to put in between the crown and flint of some of their lenses? I guess I lucked out when I bought my 103mm x 1575mm f/15 Jaegers, because it came with it's own aluminum spacer. I think it's aluminum, it may be plastic, I'm not sure, all I care about is that it works. I'm a little leery about using masking tape, what thickness masking tape, what thousand's of an inch is it? Do you layer it? Isn't that important? I sure think so. But I may be wrong.
Z

#2 Benach

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Posted 25 March 2012 - 03:42 PM

For f/15 probably not important.

#3 mikey cee

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Posted 25 March 2012 - 03:50 PM

My 6" F/8 Jaegers has 6 teflon tape spacers that are self sticky type. Also there are 6 teflon "spacers" on the flint's retaining ring. ;) Mike

#4 Gene7

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Posted 25 March 2012 - 04:47 PM

The best and most common spacers are three small tabs of aluminum tape. They stick in place. Use only three or you can create stresses. A common thickness is .003 inches. You can star test to see what thickness is best. Gene

#5 Z28500

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Posted 25 March 2012 - 06:30 PM

Is that 6" Jaegers a Surplus Shed lens? The reason I asked is because I have bought a D=103mm f=1575MM F/15 Jaegers from S.S. and it came with the spacer. I put it in a mock up I built out of PVC and it worked perfectly. Some of their other lenses need the tape and I wanted to know how accurate it was. Because they really do have some good prices.
Z

#6 mikey cee

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Posted 25 March 2012 - 10:19 PM

The lens was purchaed in 1974 for $235. Jaegers probably put 6 spacers in because they had nothing better to do. Doubling up their costs on any one facet of their business was a brilliant business move I'm sure. :smirk: Mike

#7 Z28500

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Posted 02 April 2012 - 01:00 AM

Mike,
What were those spacers back in 1974 made out of? And were those Teflon spacers in between, And/or at the sides of the lens against the lens cell?
Z

#8 Benach

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Posted 02 April 2012 - 01:06 AM

Between the lenses. It is to create an airgap betwee the lenses.

#9 Marc-Andre

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Posted 02 April 2012 - 08:47 AM

The best and most common spacers are three small tabs of aluminum tape. ...... A common thickness is .003 inches. You can star test to see what thickness is best. Gene


Where can I purchase aluminum tape. Does the tape come in different thicknesses. I bought a 60mm f15 C.O.C. at Stellafane which has no spacers between the elements. The image is "mushy". I suspect the objectice was dismantled, spacers lost, and maybe it was re-assembled wrong. There are also no markings on the lens elements to suggest radial alignment. I'm definately new to doing optical work. Thanks

#10 mikey cee

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Posted 02 April 2012 - 09:43 AM

Z....Those were as far as I'm able to tell all teflon sticky backed tape. There are six spacers between the elements. There are also six on the face of the retaining ring that goes against the flint. ;) Mike

#11 Z28500

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Posted 02 April 2012 - 11:10 AM

My Jaegers D=103mm F=1575mm came from surplusshed.com with a solid spacer ring that S.S. said to put in between the crown and the flint and then line up the marks that they put on the edges of the lens for the orientation. The spacer seemed to be made out of hard black plastic. Other lenses I've had in the past have had a 1 piece flexable clear plastic spacers - very thin too, maybe 20 thousands or so. The Jaegers spacer seemed to be around 40 or 50 thousands, kind of thick, and I was wondering if that was normal. I know that the long focal length scopes are more forgiving, but I wanted to find out if anyone out there has a similar space between the crown & flint. Right now the lenses are in a PVC mock up (to physically check the focal length)and they seem OK. Actually more than that, they are awesome lenses. They're just not coated yet. After I build the aluminum tube for it, I'll send them in for coating. Which is another issue, where to send them & then, which coatings?
Z

#12 Gene7

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Posted 04 April 2012 - 12:28 PM

Any hardware store should have aluminum tape. Home Depot will have a choice. Heavy Duty should be thinker. Again, star test to see what thickness, one or two layers, for example. ZZ, .020 does not sound right, that is quite thick, again, star test. See if inside and outside positions are the same view.

I do not like plastic rings. I and other people have found they get a kink in them and you MUST not mount with such pressure to take it out. Gene

#13 Gene7

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Posted 04 April 2012 - 12:27 PM

Any hardware store should have aluminum tape. Home Depot will have a choice. Heavy Duty should be thinker. Again, star test to see what thickness, one or two layers, for example. ZZ, .020 does not sound right, that is quite thick, again, star test. See if inside and outside positions are the same view.

I do not like plastic rings. I and other people have found they get a kink in them and you MUST not mount with such pressure to take it out. Gene

#14 Gene7

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Posted 04 April 2012 - 12:27 PM

Any hardware store should have aluminum tape. Home Depot will have a choice. Heavy Duty should be thinker. Again, star test to see what thickness, one or two layers, for example. ZZ, .020 does not sound right, that is quite thick, again, star test. See if inside and outside positions are the same view.

I do not like plastic rings. I and other people have found they get a kink in them and you MUST not mount with such pressure to take it out. Gene

#15 Ed Holland

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Posted 04 April 2012 - 02:58 PM

+1 on not using a ring. For my 5" Meade, I had spacer problems when one of the originals detached. I figured out a process to make a ring, very carefully and accurately from Mylar film. This failed to keep the lenses spaced accurately, because the retaining ring did not contact evenly around the circumference. The elements could rock in relation to each other.... poor & unpredictable star tests were the result.

My solution was to make 3 "tab spacers" in the classical style, between the elements. Then, at the same locations, I added 3 more "cushions" cut from card that fit between the outer element and the retaining ring. This ensured the elements were secured properly, with gentle tightening ot the ring. Star tests were good, and the system is very stable.

Just my 2p

Ed

#16 ed_turco

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Posted 07 April 2012 - 04:05 PM

Three spacers is probably the way to go, but the smart thing to do might be to measure the thickness of the space that came with the Jaegers 4" lens.

#17 M Schnittker

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Posted 12 April 2012 - 12:24 AM

My 4 1/8" f/15 Jaegers lens I bought in 1969 has a metal ring spacer about 1/8" thick. I recently bought the same lens from Surplus Shed (uncoated though I believe) and it came with the same sort of spacer. I've used scotch tape with my old Jaegers 6" f/10 and she works fine, don't know if thinner metal tape would make a difference.

Sort of new subject - Z28500 mentioned making a cell for his 102mm out of PVC, can he provide more detail? Mine came with a Jaegers aluminum cell and I'd greatly like to find another for the Surplus Shed lens. I'd also like to find a Jaegers cell or equivalent for the 6" Jaegers lenses. I have one of Jaegers cells for the 6" lenses and have thought more than once it would be interesting to find out how much it would cost to make a few copies at a machine shop. Any ideas out there? Any demand for copies of the 4" and 6" Jaegers cells? They do not collimate but slide a good ways into the tube so don't really need adjustment other than a small whack in the right direction now and then. I also have a Celestron CR6 collimatible 6" f/8 lens cell with dew shield I managed to buy years ago but it narrows to 5.5" ID about 3" behind the lens where it is threaded to screw on to a tube an example of which I've never been able to locate. I know it would vignette to some degree a 6" f/10 (5.5" OD at 5" behind lens) or f/15 cone of light (5.5" OD at 7.5" behind the lens). Come to think of it, 5.5" ID would vignette a 6" f/8 any closer than 4" behind the lens, why did Celestron design the cell to cut off the cone of light for their f/8 lens? Covers up any turned edge problems the lenses might have?

#18 Z28500

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Posted 12 April 2012 - 05:07 PM

Yes, M Schnittker,
I am having a collimatable lens cell made by: www.crawmach.com contact Danny over there. He is making one to fit a surplusshed Jaegers 103mm I have. Right now I have the lens in a 4" PVC thin wall coupling which is a perfect fit (Loose-rattle-like it's supposed to be) The whole scope is a PVC "Mock Up" it's going into a 4 1/2' alum tube from www.speedymetals.com. and a 2" Dual speed focuser from crawmach.com also. After doing a little research, I was very impressed with Crawmach Machine Shop, great attitude and everything. Hope that helps.
Z

#19 Z28500

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Posted 21 April 2012 - 11:15 AM

The ring that came with my lens seemed a little thick, but a star test showed perfect focus from the center to the edge of the lens (Planets also - like Saturn) No double images, ghosting, or reflections, just perfect images from one edge of the lens to the other. The spacing must be right. Lens orientation also, Surplus Shed ronchi tested and marked the lens, they seemed to have got it right on the money.
Z

#20 Perseus_m45

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Posted 10 January 2013 - 11:04 AM

i have made the same purchase from surplus shed and was wondering how things turned out on this project?
mike

#21 bremms

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Posted 10 January 2013 - 10:46 PM

My 4" F15 SS lens showed a good bit of undercorrection with the 1/8" spacer. With 0.002" of foil spacers the lens is much better, still a little undercorrection but it is minimal. The effect of the spacer is spherical and color correction. Ghosting and edge to edge focus won't be effected too much by the spacing. You need to do intra and extrafocal ring star tests. ( use a green filter for accurate results)

#22 Z28500

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Posted 22 January 2013 - 07:37 AM

Turned out great, here is a few threads of the scope One is another forum and you have to have a user name & password:

http://www.cloudynig...&Board=atm&N...

http://www.cloudynig...5140754/page...

http://www.astronomy...08-soon-maga...

Z

#23 Z28500

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Posted 22 January 2013 - 07:49 AM

Also I have zero "ghosting" and the edge to edge image is exactly the same as it is in the center. Surplus Shed gave me a really good set (they weren't the seconds) I have a 90mm meade I bought cheap from EBay, and when the image gets to the edge it starts to get a little blurry, not with this Jaegers! The only thing the lenses do have is a little chromatic aberration, but all achromats have that problem. The bigger the lens, the more CA. I've read some reviews and a common point seems to be that CA isn't that noticable with lenses 4 inches and smaller, yet another point is how much does CA really bother a person anyway. I really don't care and I have an Apo (6 inch)! But back to the F/15-Star Test was perfect, I guess if I was going to recommend anything it would be collimation, objective lens and focuser. A good place to get those two items is where I got mine:

http://crawmach.com/home

Dan is the guy that builds them and mine were built perfect.
I got my tube from speedymetals.com and then turned it down on a lathe to .050". They also have all kinds of other alum & brass.
I also built a mock-up out of green PVC 1st to get the length right and also to see how the lens worked.
Good luck.
Z

#24 Napersky

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Posted 22 January 2013 - 03:35 PM

PM Sean Cunneen as he knows everything about spacing and building lens cells for the Jaegers.

Mark

#25 BarabinoSr

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Posted 22 January 2013 - 04:22 PM

When I got the objective for my 4.5" Jaegers, I obtained some air-conditioning duct tape. This is the kind that has some adhesive on the back and aluminum finish on the front. I was able to cut some very tiny rectangles out, place them in position using a pair of tweezers in between the elements .I also had owned previously a 6" f/15 Jaegers and did this before, so I know it will work! I also took the time to make sure that the spacers (3) were spaced equidistant from each other before putting back in the convex lens. The tape pieces did not move during this action due to the adhesive, and I don't think that the tiny amount would harm the elements.Regular aluminum foil pieces would not stay in position for me.
After this was done and later in the evening after the optics acclimated,I took the scope out for an observing session and grabbed a neat lunar shot:

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