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First experience with Gen 3 Filmless WP NV device

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#51 Eddgie

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Posted 07 September 2016 - 10:25 AM

The eyepiece focal lenght on the PVS-7 or PVS-14 type eyepeices is about 27mm.   

 

A 50mm lens would give you slightly less than 2x.

 

Do you have a 3x Afocal lens?  I am curious tho know if stars are any sharper in modern zooms than the are in my older zooms.  Even with heavy filters, I still can't get stars to be particularly sharp.    I don't think these older zooms had very good light transmission and perhaps bloat a bit becuase of internal reflections, but that is just a guess.

 

 

I had always figured a true Apo lens or ED lens would give a result that would be similar to the Afocal lenses, though at a very high cost.  These lenses get pretty pricey when they get big and fast.  I was kind of curious to know how these later lenses, which often use some ED glass, would compare.


Edited by Eddgie, 07 September 2016 - 10:26 AM.


#52 Rocket Ron

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Posted 07 September 2016 - 10:32 AM

Yes, I have the 3x Afocal.  I'll do a comparison tonight.  My 60mm is f2.8.   It's a high quality Macro lens.  

 

So my 60mm gives me 2.2x magnification?  And my 18-200 zoom would be 0.67x to 7.4x?  



#53 Eddgie

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Posted 07 September 2016 - 02:52 PM

I have gotten different figures for the focal length of the eyepieces but I think they are between 27mm and 30mm in focal length.

 

The PVS-14 and ENVIS lenses are 25mm with a focal ratio of f/1.2m so that says the focal lenght would be 30mm so to give exactly unity, the eyepiece would have to be 30mm as well, but I think that the eyepiece is in fact a tiny but shorter than 30mm.

 

In one video, Cnoct is using a Meade Light Bridge telescope and I think the focal lenght of these is supposed to be 1270mm.

 

He states that the magnification is 45x, and if this is the case and the relay lens is 1x, then this would give 28.2mm for the eyepiece but I don't know if the eyepeice is the same as it is in a PVS-7 or PVS-14.

 

I have read slightly different figures here and there ofr the lens focal lenght, but I think it is in the 27mm to 30mm range. 

I just use 27 and figure that is close enough, though I could be a little high on my magnifications.

Still, if it is 30mm, that would be 50x in my 1500mm dob, and if it were 27mm, it would be 55.5x.  so not a big error there I don't think.      Again, I have heard different figures, but when I back engineer Cnocts figures for his dob, I get 28.2mm.


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