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martym
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Reged: 02/15/10

Re: Jaegers objective new [Re: mikey cee]
      #4768654 - 08/25/11 02:05 PM

Yes, Barry at D&G told me that he tests the lens after comming back from coating. Why would that be done unless the glass is being changed from the heating and that is known. He has the test results before and after coating in front of him.

What's the people like AP doing when they are sending their triplets out for coating and comming back bad. Must being going into a screaming tizzy. Can you imagine?

marty


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BarabinoSr
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Reged: 11/17/05

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Re: Jaegers objective new [Re: martym]
      #4769115 - 08/25/11 06:59 PM

I'm reading these posts about Ronchi testing lenses .I cant afford to spend a lot of money on having someone test a lens or even building a unit to do that and I dont have a problem with it if that is what someone wants to do. I'm also not going to worry about anyone's "bad lens".Though testing lenses that way is ok ,I dont need to have a tester to see if a lens is bad or not. If you are an experienced observer and are familiar with your refractor systems ,you know that many factors come into play when determining objective lens quality,among these being glass types and sizes,air temperature ,eyepiece and objective differences .
I built a 6" f/15 refractor from a mounted A Jaegers objective back in 1976 and it was excellent, handling magnifications of up to 300x very well with various orthoscopic eyepieces,and recently I finished a 4" f/8.3 refractor with a Jaegers lens,and it too produced great images with varying eyepieces.
There are bound to be bad objectives here and there,but the point is do the simple things to check it first. Before I built the 4",I made a "Box scope" that helped greatly in the final design of the main instrument .This has always worked for me. G


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dawsonian2000
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Reged: 07/26/06

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Re: Jaegers objective new [Re: martym]
      #4769214 - 08/25/11 07:58 PM

Quote:

Yes, Barry at D&G told me that he tests the lens after comming back from coating. Why would that be done unless the glass is being changed from the heating and that is known. He has the test results before and after coating in front of him.

What's the people like AP doing when they are sending their triplets out for coating and coming back bad. Must being going into a screaming tizzy. Can you imagine?

marty




Now, I wonder what percentage of the batch of lens elements Barry sent out for coating by Majestic actually come back with issues?


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dan_h
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Re: Jaegers objective new [Re: dawsonian2000]
      #4769382 - 08/25/11 09:34 PM

Probably very few. The lens has to be tested after coating because it is assembled into its cell at that time. Testing assures proper assembly and that the lens is not pinched in the cell, that the spacers are properly applied and that the lens elements are properly centered once assembled. I would expect any manufacturer to test a lens for these issues once it is assembled.

dan


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dawsonian2000
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Re: Jaegers objective new [Re: dan_h]
      #4769626 - 08/25/11 11:49 PM

That's an encouraging bit of information, Dan! I would hate to see anyone's optics turn up in a scrapheap. But, I bet some do.


Mel


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dawsonian2000
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Re: Jaegers objective new [Re: Sean Cunneen]
      #4771303 - 08/26/11 11:54 PM

Hey Sean,

Going off topic for a pinch, I like what you did to make the collimation cell for Jill! A really nice piece of work! I would like to get some insight from you on making one for my 6" f/10. We can PM or use external email to discuss further.

Thanks,
Mel


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Sean Cunneen
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Reged: 08/01/07

Loc: Blue Island Illinois
Re: Jaegers objective new [Re: dawsonian2000]
      #4771886 - 08/27/11 11:03 AM

ahem. i'll make this post as quietly as possible. I may have had the elements all flipped around wrong. I'll let you know





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watcher
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Reged: 11/21/07

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Re: Jaegers objective new [Re: Sean Cunneen]
      #4772318 - 08/27/11 02:41 PM

OOOOPS!

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Sean Cunneen
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Reged: 08/01/07

Loc: Blue Island Illinois
Re: Jaegers objective new [Re: watcher]
      #4772415 - 08/27/11 03:47 PM

Let me rephrase my previous statement...

I am going to try some different configurations to see if my lens can be assembled in a different, optically better configuration.

Sean:)


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mikey cee
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Re: Jaegers objective new [Re: Sean Cunneen]
      #4772561 - 08/27/11 05:15 PM

When I've had my Jaegers 6" F/8 apart for cleaning therewas no way to visually discern which side of the crown is which. I made dang sure I marked it the first time. Mike

Edited by mikey cee (08/27/11 05:17 PM)


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DAVIDG
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Re: Jaegers objective new [Re: mikey cee]
      #4772657 - 08/27/11 06:30 PM Attachment (114 downloads)

If you test the objective it is very easy to see if you got it assembled correctly. The issue is that if you don't get it right it will still form an image and the image can be pretty good but just not as good as it good be. As I have said there are a number of cases were historic objectives have been assembled backward for years and no one has challenged the image quality, but unfortunately
the observers have not be able to take advantage of the true optical quality of the telescope for all that time. So just because you think you got it assembled right and the image looks good doesn't mean you did. Also the person before you could have done it wrong and your just repeating their mistake.
I just displayed a 3" Tinsley refractor at Stellafane that I restored were the objective was in the cell backwards for at least 30 years if not much longer and everyone I talked that had used the telescope has the image was great.
Here is a picture of that objective being tested.

- Dave


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BarabinoSr
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Re: Jaegers objective new [Re: DAVIDG]
      #4772976 - 08/27/11 10:40 PM

I have also disasembled objectives for cleaning for time to time, including my former 6" f/15 Jaegers ,and when putting the elements back togather the concave goes in cell first, spacers on this element.
The concave element must face flat side to the focuser.The more convex side of the convex element must be installed as to face the concave lens .If it is not,the telescope's image will suffer.
It's role is different in the fact that one side is slightly more convex than the other side. You can see this by looking at it from edgewise.
Correct element spacing is crucial make sure that your spacers remain in place equidistant from each other,and when reapplying the retaining ring,it must not be tightened too tight ;You should be able to hear a slight rattle so that the lenses may adjust to temperature changes . Since I've deen doing this work this way,I've never had any problems . Gary

Edited by BarabinoSr (08/27/11 10:47 PM)


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Napersky
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Re: Jaegers objective new [Re: dawsonian2000]
      #4778208 - 08/30/11 01:59 PM

Mel,

I have had the Zygo for a year and a half now. I need to adjust it because the beam has to go thru a pinhole and emerge at the other side.

I just received my 6" F15 with lens cell the other day!

Mark


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dawsonian2000
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Re: Jaegers objective new [Re: Napersky]
      #4778627 - 08/30/11 05:56 PM

Awesome! The more I think about it, the more I wish I would have bought the f/15 instead of the f/10. But, on second thought, maybe not. I purchased the f/10 for transportability.

Eagerly awaiting your test results once they are performed!


Mel


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Dick
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Reged: 08/19/06

Loc: Orlando
Re: Jaegers objective new [Re: BarabinoSr]
      #4778662 - 08/30/11 06:15 PM

Time to chime in. Been watching this post for awhile. I too bought a Jaegers 6" F10. Ordered an F15 at first but after some review of others I switched to the F10 before SS shipped. No coatings on my lenses. Fred marked the edges during his testing. I may be interested in a coating buddy to reduced costs. I really would like to see the progress on everyones projects. This thread could be going on for awhile. Need to sell some things before I start to build. Too many projects costing too much money.

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dawsonian2000
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Re: Jaegers objective new [Re: Dick]
      #4778812 - 08/30/11 07:24 PM

Hi Dick,

Welcome aboard! With you living so close to me it would have been great to buddy-up on a coating deal, but despite the controversy I already sent them a couple for coating; my 6" f/10 and also a Jaegers 4.3 f/15.

Yes, this thread is going to be flaming for quite a while. I hope the end results of everyone's builds will be very satisfactory.

Mel


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Jeff B
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Re: Jaegers objective new [Re: dawsonian2000]
      #4779900 - 08/31/11 11:38 AM

Regarding the coating of these lenses. Technically, I feel the only surfaces that NEED coatings are the interior ones, R2 & R3 as they are very close in proximity and very close, if not equal, to each other in radius. This allows for the generation of ghosting, which coatings, even good old MgFl, will basically eliminate.

Also, R1, being uncoated, can be cleaned without any worry of the coating being damaged, since there isn't any. Plus, I believe, you'll be exposing the lens to only one coating process, R2 & R3, instead of two, to pick up R1 & R4. This cuts the risk of loosing the lens due to a coating mishap in half.

Just something to consider.

Jeff


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dawsonian2000
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Re: Jaegers objective [Re: Jeff B]
      #4780217 - 08/31/11 02:06 PM

Thanks Jeff!

Great information to those of us considering or getting our lenses coated. I initially was going to get R1 and R2 coated, but decided to get all four radii coated after accepting a great deal. But, your point about coating R2 and R3 makes good scientific sense. It also offers a means to save some cash; at the same time getting good performance from our refractors.

Thanks again,

Mel


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dawsonian2000
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Re: Jaegers objective [Re: dawsonian2000]
      #4785069 - 09/02/11 06:37 PM

Today, my lenses arrived at Majestic Optical Coatings. I will be sure to report back on my dealings with MOC once I have received and tested my optics.

Mel


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Dick
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Reged: 08/19/06

Loc: Orlando
Re: Jaegers objective [Re: dawsonian2000]
      #4785375 - 09/02/11 09:46 PM

I was wondering if anyone has actual numbers for lens spacing. I remember about a year ago when I called Jaegers directly and got ahold of Mr. Jaegers. I am not sure how many family members were involved with the business or which Jaegers I was talking to. He seemed to be an older man from his voice. Anyways I was building a 78mm jaegers F15 refractor and asked him about the lens spacing. Without hesitation he immediately indicated it was a 0.100" lens spacing. I now wonder what the 150mm F10 spacing would be. I know Fred at SS got all of the technical drawings / data. The spacing for all of the lenses maybe in the hands of Fred at SS. I will try to gather data from him next week and post. It maybe buried in all his stuff.

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