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Who here can DPAC test?

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9 replies to this topic

#1 jimeh

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Posted 11 March 2025 - 01:53 AM

I have two objectives that I would love to have tested. One is a Zeiss objective that I think is very good and the other is a Goto objective that I expected to be very good, but doesn't seem to be.

 

Is there anyone here with DPAC testing capabilities who'd be willing to look at these two objectives?

 

The Zeiss objective is developing some mold growth. I'm very hesitant to take the objective apart because Zeiss makes the lens cell to very exacting standards and then buttons it all up with hardware that's not that simple to undo. I'm not well-versed enough in DPAC testing to know if the mold affects the test in any way. I think it doesn't. I'd like to have this tested so I can figure out whether to build a new scope around the glass, or let it go,

 

The Goto is from a Hy-score 451. The retaining ring jumps the threads in the lens cell, so I added teflon tape hoping that would help. It did, but it will still jump the threads if I torque it too much (which isn't a lot of torque), so I don't know if the poor images are from the glass itself or the worn out lens cell not putting the glass in the right position. I'm 99% sure the elements are in the correct order, but honestly, I don't know if it's a Steinheil or Fraunhofer doublet, so it might be just flat out backwards. I've tried both and I'm pretty sure I have it right, but it's still not what I expected.

 

I don't know anyone with testing abilities, so I thought I'd ask here. Any help is very appreciated.

 

 


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#2 davidc135

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Posted 11 March 2025 - 03:03 AM

Apart from members in this forum who may reply, you could contact one of a number in the refractor forum who have extensive testing experience. I believe Peleuba, JeffB and ScottinNC and maybe others would be happy to help if they were Pmed.

 

The sooner you sort out the mould in the Zeiss, the better. At the least and as a stopgap, I'd try to kill it with exposure to strong sunshine. I don't think that the mould would affect the corrections but it may etch the surface if left.

 

David


Edited by davidc135, 11 March 2025 - 03:06 AM.

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#3 CHASLX200

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Posted 11 March 2025 - 05:50 AM

Not me.



#4 starman876

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Posted 11 March 2025 - 09:11 AM

If I had the optical bench ready I would gladly help.  However, there are several in this forum who have a nice setup.  Bomber Bob comes to mind as one. 


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#5 jragsdale

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Posted 11 March 2025 - 10:02 AM

I can do a DPAC for you if you'd like. And I'm not too far to ship. And I also have a similar Goto scope so I can compare it to mine for design. Shoot me a message!


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#6 Darren Drake

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Posted 11 March 2025 - 10:12 AM

Where do you live??



#7 saemark30

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Posted 11 March 2025 - 10:19 AM

How big are the objectives?



#8 deSitter

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Posted 11 March 2025 - 11:46 AM

It's a great test but it is not a substitute for star testing. Cannot recommend Suiter's book highly enough. Small refractors are better tested with stars than bars :)

 

-drl


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#9 Bomber Bob

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Posted 11 March 2025 - 12:53 PM

If I had the optical bench ready I would gladly help.  However, there are several in this forum who have a nice setup.  Bomber Bob comes to mind as one. 

Yes, I've tested dozens of objectives -- from Mush Dogs to the Super Freaky Sharp.

 

Just don't ask for photos!

 

[Thanks Again, Johann, for the 6" flat.  If IT could talk... well, couldn't post it here - not suitable for families!]


Edited by Bomber Bob, 11 March 2025 - 12:55 PM.

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#10 jimeh

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Posted 11 March 2025 - 06:01 PM

Thanks everyone! Message sent.

 

 

It's a great test but it is not a substitute for star testing. Cannot recommend Suiter's book highly enough. Small refractors are better tested with stars than bars smile.gif

 

-drl

 

I agree, but the Zeiss objective is without an OTA and I think the Goto is shifting in the cell as soon as I attach it to the tube, so bench testing is my only recourse for the moment.


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