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Equipment Discussions >> Classic Telescopes

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ngc2289
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Fair price for Unitron 75mm f/16 Objective.
      #5784686 - 04/07/13 08:15 PM

What would be a fair price for a Unitron 75mm f/16 objective in cell? The objective is in excellent condition if a little dusty. Thank you.

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sgorton99
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5784696 - 04/07/13 08:17 PM

Here is one right now on ebay - http://www.ebay.com/itm/Vintage-Unitron-75mm-1200mm-f-16-Telescope-Lens-And-C...

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: sgorton99]
      #5784706 - 04/07/13 08:20 PM

Yes I know. That is my bid you are looking at. Just wanted to know what I should set my max bid at.

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sgorton99
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5784718 - 04/07/13 08:26 PM

Oh, last December one was listed on Astromart for $170. It sold, but I can't tell you how much it actually went for.

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: sgorton99]
      #5784777 - 04/07/13 09:01 PM

Thank you. So the amount I was thinking of isn't to far off.

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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5785053 - 04/07/13 11:33 PM

than there is the one on Ebay that went for over $400.

http://www.ebay.com/itm/Unitron-75mm-Refractor-Lens-in-Complete-Collimatable-...


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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5786398 - 04/08/13 04:55 PM

Looks like I won't be getting the lens. I placed a max bid of $170.51, and the auction is already up to that amount. With 4 days left I am sure someone will outbid me. That is OK though, and I will not increase my bid anymore.

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5788413 - 04/09/13 03:04 PM

Well I have changed my mind. As a back-up I was checking to see if I could get a Carton 80mm f/15 lens from Sheldon Faworski. He is out of the f/15 lenses. Sheldon sold all the f/15 lenses he had to a certain someone I won't name in the UK. I think we all know who that dastardly fiend is( )! So I have now increased my max bid. Here is hoping I get it!!

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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5788435 - 04/09/13 03:09 PM

If you have no luck I am sure someone here will be able to help you out

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Bonco
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5788527 - 04/09/13 03:34 PM

For comparison Sheldon sold me 2 80mm f/15's for $120 each. Fantastic lenses I might add. I offered one of the OTA'swith mount for Sale at $170 here on CN. No bites. People don't know how good these lenses are. Good luck on the Unitron lens.
Bill


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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5792114 - 04/11/13 10:59 AM

Well I decided the Unitron was getting a little too expensive. So I am not going to purchase the Unitron instead I have ordered a Jaegers 83mm f/1219 objective lens. Although the Surplus Shed site states the lens is uncoated. When I called up Majestic Coating they said to check because a lot of these lenses are coated. So heres hoping I get a good one!!

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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5792128 - 04/11/13 11:09 AM

Now comes the other side of the story. I am not sure if Surplus Shed is making sure the doublets are matched sets. In other words, they might have a flint that is good and the crown and then just send a set that looks good. No chips or other blems. Make sure you ask them if they are a matched set.

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5792211 - 04/11/13 11:59 AM

I sent Surplus Shed an e-mail asking for a matched set, and they said they Ronchi test each lens set before shipping.

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bremms
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5792263 - 04/11/13 12:26 PM

I had hit or miss on the SS 80mm F15. I had to send one back since the FL was off and the correction was terrible. The other one I ordered has a nearly perfect star test. Have another on the shelf that I haven't tested.

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DAVIDG
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5792348 - 04/11/13 01:14 PM Attachment (18 downloads)

Quote:

I sent Surplus Shed an e-mail asking for a matched set, and they said they Ronchi test each lens set before shipping.



While that maybe true, I don't believe they understand how to test these lenses. When you do a double pass autocollimation test you need to adjust the position of Ronchi screen so your viewing 5 bands or less. If your viewing more bands the sensitity is not very great and lines will look straight.
I've purchased a number of Jaegers objective from them over the last 2 years. Attached is picture of 4" f/15 on my test setup using double pass autcollimation. As one can see the lines are bowing and from the amount I judge this objective to have about 1/4 wave or worse of overcorrection. This is typical of the objectives I have purchased.

- Dave


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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: DAVIDG]
      #5792652 - 04/11/13 03:53 PM

I rest my case. However, they are great people and will work with you.

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bremms
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: DAVIDG]
      #5792658 - 04/11/13 03:57 PM

Did you use the 0.100 to 0.120" spacer in that test? I did notice with my 4" F15 that the correction was best with the spacer as it is a supposed to be a Baker design. 2-3mm may not give enough under correction. to fix the over correction.

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DAVIDG
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: bremms]
      #5792918 - 04/11/13 05:26 PM

Quote:

Did you use the 0.100 to 0.120" spacer in that test? I did notice with my 4" F15 that the correction was best with the spacer as it is a supposed to be a Baker design. 2-3mm may not give enough under correction. to fix the over correction.



I used the spacer provided with the lens and also varied the spacing. It didn't help. I have the Baker design in OLSO files so I can see what happens when the air space is varied. When you vary the air spacing you also change were the red and blue wavelengths come to focus. So you need to test that has well, if not the performance can look better in the green but the color correction can then be much worse.
The best way to fix one of these objectives is to refigure a surface or surfaces. That is why I have purchasing the uncoated ones since I can starting refiguring them without having to polish off the anti-reflective coating.

- Dave


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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: DAVIDG]
      #5792945 - 04/11/13 05:42 PM

Seems we have a couple of guys here with much more expertise than I will ever have. Maybe you can help. I have a Jeagers 6" F8 with awesome low power views. However, when I start to bumb the power up the lens is awful. Stars turn to spikes. I tried different spacing, but if the spacing was too large I just started getting ghost images. Maybe if I oiled the lens it would work better. Or, did I get one of the Surplus shed mis mathced sets? Of course they told me the Ronchi tested it. I do not have a ronchi test set up otherwise I would have tested it.

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5793022 - 04/11/13 06:26 PM

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.

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

2

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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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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. new [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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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. new [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. new [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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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805864 - 04/17/13 11:28 PM Attachment (16 downloads)

d

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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805865 - 04/17/13 11:28 PM

That looks a lot better then the box I have . Is that a Tasco?

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805868 - 04/17/13 11:29 PM Attachment (15 downloads)

e

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805870 - 04/17/13 11:30 PM Attachment (10 downloads)

f

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805871 - 04/17/13 11:30 PM Attachment (12 downloads)

g

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805877 - 04/17/13 11:33 PM

Tasco 10K came in today.

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805892 - 04/17/13 11:42 PM Attachment (11 downloads)

h

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805896 - 04/17/13 11:45 PM Attachment (11 downloads)

i

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805898 - 04/17/13 11:46 PM Attachment (11 downloads)

j

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5805907 - 04/17/13 11:49 PM

The flash makes the lens look much dustier then it is.

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Dave M
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5806266 - 04/18/13 08:45 AM

Very Nice

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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: Dave M]
      #5806313 - 04/18/13 09:18 AM

Wow another Tasco. Nice. What happened to the 75mm Unitron objective

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5806573 - 04/18/13 12:46 PM

The 75mm got too expensive. With shipping the objective was almost as expensive as the entire Tasco.

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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5806765 - 04/18/13 01:38 PM

I think the last 75mm lens went for $150.

I think the mad craze of bidding is over. Things are back to normal. Evident of tile guy sales. prices are back where they belong.


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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5806802 - 04/18/13 02:08 PM

When I retracted my bid the amount was at $170.51 plus the shipping. The Tasco was $180 plus shipping.

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starman876
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5806820 - 04/18/13 02:21 PM

You got a great scope instead of just an onjective. I would be very pleased if I were you. And you most likely have a better scope in the end.

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Bonco
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5807091 - 04/18/13 04:46 PM

The telescope package looks great. Likely the optics will be fine. I think you got it at a bargain price.
Bill


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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5809785 - 04/19/13 10:56 PM Attachment (11 downloads)

When I was cleaning up what I thought was a Tasco I found this small makers mark! What does it mean??

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5809791 - 04/19/13 11:02 PM

I forgot to mention it's dated 1868! So I got a really old, and rare scope!!!

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5811924 - 04/20/13 09:57 PM Attachment (5 downloads)

I have a Vixen SP-80 refractor, and I discovered I can unscrew the 1 1/4" adapter on its focuser. I then removed the .965" tube from the Tasco's focuser, and then screw the Vixen 1 1/4" adapter onto the Tasco. Now I have a 1 1/4" focuser on the Tasco! Although the focuser does have only 1 7/16" travel. Here is a picture of the set-up.

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5836818 - 05/02/13 05:39 PM

Well before I do something stupid I am going to ask for information. I need to relocate the baffle in my Tasco, and to do so I need to remove the lens cell from the tube. I tried to take the cell off by hand but that was a no go. So I have purchased a strap wrench to loosen the lens cell. But before I start cranking on the cell one simple question. The lens cell is threaded onto the tube, and not attached in some other way? Just want to make sure before I break something! Also by how much should I move the baffle? Thank you!!

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5837542 - 05/03/13 01:00 AM

Well I answered my own question, and yes the lens does screw off. Now I think I will move the baffle about 2" closer to the focuser, and flock the front of the tube. Clear evening skies.

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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: ngc2289]
      #5837805 - 05/03/13 08:36 AM

I have been thinking myself how do I make sure the baffles are in the right spot. Most likely ray tracing is the way to go. However, I do not have that program. Anyone here have a program they can recommend?

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ngc2289
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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5838274 - 05/03/13 12:26 PM

The method I am using is to put the diagonal, and eyepiece turret in the focuser. Then I rack the focuser out to where the eyepieces focus then look into the aperture where the eyepiece is placed. When I did the afore mentioned I could see about 55mm to 60mm of the central part of the lens. So the baffle is acting like a aperture stop at it's present location, and needs to be moved.

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Re: Fair price for Unitron 75mm f/16 Objective. new [Re: starman876]
      #5838345 - 05/03/13 01:00 PM

Quote:

I have been thinking myself how do I make sure the baffles are in the right spot. Most likely ray tracing is the way to go. However, I do not have that program. Anyone here have a program they can recommend?




Neither do I. You can always do a ray trace the old fashioned way with proportional triangles. Just get out the old drafting board, T-square, right triangle, engineer's scale, and a pair of dividers. That's the way I do it.


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ngc2289
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Tasco 10K Second light. new [Re: ngc2289]
      #5842470 - 05/05/13 09:15 PM Attachment (13 downloads)

Right now I have the 10K outside waiting for sun set, and second light. First light was two weeks ago. Since first light I have moved the baffle 2" closer to the focuser, and flocked the scope interior. Pictures follow. That is all.

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Re: Tasco 10K Second light. new [Re: ngc2289]
      #5842473 - 05/05/13 09:17 PM Attachment (10 downloads)

Pic. 2

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ngc2289
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Re: Tasco 10K Second light. new [Re: ngc2289]
      #5842474 - 05/05/13 09:17 PM Attachment (7 downloads)

Pic. 3

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ngc2289
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Re: Tasco 10K Second light. new [Re: ngc2289]
      #5842477 - 05/05/13 09:18 PM Attachment (5 downloads)

Pic. 4.

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Re: Tasco 10K Second light. new [Re: ngc2289]
      #5842481 - 05/05/13 09:19 PM Attachment (14 downloads)

Pic. 5, and end.

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UND_astrophysics
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Re: Tasco 10K Second light. new [Re: ngc2289]
      #5851224 - 05/10/13 01:03 AM

Very nice setup!!!

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Re: Tasco 10K Second light. new [Re: UND_astrophysics]
      #5851233 - 05/10/13 01:10 AM

Thank you. I am enjoying it greatly weather permitting!

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Re: Tasco 10K Second light. new [Re: ngc2289]
      #5852190 - 05/10/13 02:59 PM

Great job Mike! Looking forward to hearing how second light went.

Terra


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Re: Tasco 10K Second light. new [Re: terraclarke]
      #5852499 - 05/10/13 06:39 PM

I have yet to have a night of good seeing so I can test the optics. Saturn did look nice even with the poor seeing. I could see some structure on the face of the planet, and Casini's division faintly. But like I said seeing was not that good.

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Re: Tasco 10K Second light. new [Re: ngc2289]
      #5852663 - 05/10/13 08:04 PM

Vrey nice looking setup. Congrats on a great job.

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