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Fair price for Unitron 75mm f/16 Objective.

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#1 ngc2289

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Posted 07 April 2013 - 07:15 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. :question:

#2 sgorton99

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Posted 07 April 2013 - 07:17 PM

Here is one right now on ebay - http://www.ebay.com/...e-Lens-And-C...

#3 ngc2289

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Posted 07 April 2013 - 07:20 PM

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

#4 sgorton99

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Posted 07 April 2013 - 07:26 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.

#5 ngc2289

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Posted 07 April 2013 - 08:01 PM

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

#6 starman876

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Posted 07 April 2013 - 10:33 PM

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

http://www.ebay.com/...ollimatable-...

#7 ngc2289

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Posted 08 April 2013 - 03:55 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.

#8 ngc2289

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Posted 09 April 2013 - 02:04 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( :flame: :lol: )! So I have now increased my max bid. Here is hoping I get it!!

#9 starman876

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Posted 09 April 2013 - 02:09 PM

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

#10 Bonco

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Posted 09 April 2013 - 02:34 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

#11 ngc2289

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Posted 11 April 2013 - 09:59 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!! :waytogo:

#12 starman876

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Posted 11 April 2013 - 10:09 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.

#13 ngc2289

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Posted 11 April 2013 - 10:59 AM

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

#14 bremms

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Posted 11 April 2013 - 11:26 AM

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.

#15 DAVIDG

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Posted 11 April 2013 - 12:14 PM

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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#16 starman876

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Posted 11 April 2013 - 02:53 PM

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

#17 bremms

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Posted 11 April 2013 - 02:57 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.

#18 DAVIDG

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Posted 11 April 2013 - 04:26 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.

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

#19 starman876

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Posted 11 April 2013 - 04:42 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.

#20 ngc2289

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Posted 11 April 2013 - 05:26 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.

#21 ngc2289

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Posted 11 April 2013 - 05:46 PM

1

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#22 ngc2289

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Posted 11 April 2013 - 05:46 PM

2

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#23 starman876

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Posted 11 April 2013 - 06:03 PM

another tasco :sleepy: :sleepy:

#24 ngc2289

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Posted 11 April 2013 - 06:10 PM

:tounge: :tounge: :tounge: :tounge:

#25 starman876

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Posted 11 April 2013 - 06:25 PM

:bow: :bow: :bow: :bow: :bow:






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