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Equipment Discussions >> Classic Telescopes

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5793052 - 04/11/13 06:46 PM Attachment (14 downloads)

1

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ngc2289
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Loc: Corpus Christi, TX.
Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5793055 - 04/11/13 06:46 PM Attachment (13 downloads)

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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5793076 - 04/11/13 07:03 PM

another tasco

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5793090 - 04/11/13 07:10 PM



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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5793123 - 04/11/13 07:25 PM



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Bonco
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5793218 - 04/11/13 08:15 PM

Chances are your 10K will be just fine and thats a good price for a complete package. Typically they have very good optics. If yours is good it will stand up optically to any 75mm-80mm achro out there including Unitrons. Let us know how it performs.
Bill


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DAVIDG
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5793359 - 04/11/13 09:49 PM Attachment (16 downloads)

Quote:

Well for better or worse I just bought myself a TASCO 10K(circle T) 80mm f/15. Comes with case, mount, and ota. Price $237 shipped which doesn't seem to bad.



Some of these Japanese objectives are excellent. Here is a shot of 80mm Selsi being tested that I picked up on Ebay for under $100. The lens is extremely good from the nearly dead perfectly straight Ronchi lines. Look for the "passed Japanese Optical Institute" sticker when looking to buy any of these scopes. From what I have read and from the objective I have tested, these telescope WERE tested and DID meet some very good specs.

- Dave


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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: DAVIDG]
      #5793389 - 04/11/13 10:09 PM

I want one of those testers. There was a thread that described how to make one. Looks like the expensive part is the flat.

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Bob Myler
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Reged: 05/18/06

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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5794386 - 04/12/13 12:54 PM

So David - how "flat" does a Flat have to be?

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terraclarke
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Re: Fair price for Unitron 75mm f/16 Objective. [Re: Bob Myler]
      #5794397 - 04/12/13 01:01 PM

Any one here ever gotten one of these? I was wondering if it's worth the ~30 bucks?

http://schmidling.com/ez-testr.htm#Order


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CharlieB
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: terraclarke]
      #5794450 - 04/12/13 01:23 PM

I have one and it's OK for detecting gross problems with an objective. It's a single pass system and good only for detecting gross problems. Double pass autocollimation is far, far superior. Jack does produce some very useful homebrewing equipment, though.

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DAVIDG
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: Bob Myler]
      #5794530 - 04/12/13 01:56 PM

Quote:

So David - how "flat" does a Flat have to be?



The flat can be many waves from optically flat and introduce only a tiny bit of optical error as in under a 1/20 of wave or less. What is critical is that the flat must be optically smooth. Here is a link that explains this. http://www.telescope-optics.net/testing_optical_quality.htm So a smooth 1/2 to 1/4 wave flat is ideal for doublepass testing and many times can be purchased on the used market very inexpensively. As the name implies this a double pass test so light passes thru the objective twice, doubling any errors it has, which makes them much easier to see. This a Null test, there is nothing the measure. If your optics test like perfect spherical mirror there are perfect. If your lens shows straight Ronchi lines at the wavelength your testing at, it is extremely well corrected for spherical aberration at that wavelength. You can also quickly determine if an element is flipped, the air spacing is not uniform, and the best rotational orientation of one element to the other. A single pass test using a star does not have this type of sensitivity or utility, plus one can only test when the stars are visible, while a double pass can be done any time and under controlled conditions. If a single pass test is done using another telescope to produce a collimated beam, the errors in those optics directly add to the ones your testing unlike a double pass with flat.

- Dave


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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: DAVIDG]
      #5795386 - 04/12/13 09:09 PM

The telescope is on the way. According to the FedEx website the scope should arrive next Wednesday.

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labmand
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Loc: Michigan USA
Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5797247 - 04/13/13 05:57 PM

ngc2289, Man, I was gonna buy that one, guess I was to slow to pull the trigger, was waiting to find out if shipping was included or what it would be, so then I turned my attention to the Sears by the same seller, dang sold too.
So I put a wtb add up, hope one of you guys have pitty on me and send one my way.


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Bonco
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: labmand]
      #5797258 - 04/13/13 06:03 PM

Quote:

ngc2289, Man, I was gonna buy that one, guess I was to slow to pull the trigger, was waiting to find out if shipping was included or what it would be, so then I turned my attention to the Sears by the same seller, dang sold too.
So I put a wtb add up, hope one of you guys have pitty on me and send one my way.




Ha! Pretty funny you and I have already communicated about your wanted to buy ad. I hope my Carton, Towa 339 fits your needs. I think the Carton lens will be as good as any 80/1200 you could find.
Bill


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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: labmand]
      #5797380 - 04/13/13 07:40 PM

I almost didn't get the scope either. It was me, and another guy competing to buy the scope. The seller told us both who ever got the payment to him first got the scope. It seems I won, well at least that is what the seller said.

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5804633 - 04/17/13 02:12 PM

Well according to the FedEx website the scope is in town, and on a truck for delivery!

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: Bonco]
      #5805852 - 04/17/13 11:24 PM Attachment (10 downloads)

a

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. [Re: ngc2289]
      #5805858 - 04/17/13 11:25 PM Attachment (9 downloads)

b

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. [Re: ngc2289]
      #5805861 - 04/17/13 11:26 PM Attachment (10 downloads)

c

Edited by ngc2289 (04/17/13 11:27 PM)


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