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Nikon/Nikor 180mm "test"

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#1 SKYGZR

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Posted 17 February 2016 - 12:10 AM

This is from the "classic Gold banded" ED glass f/2.8 Manual Focus "mini-refractor" lens. The reason it's labeled a "test", is that it was used for the first time utilizing "step down" rings. I've never liked the star difractions that arise when stepping down the iris. This test (2) rings were used. 72mm down to 52mm, w/ the lens wide open. I decided to post an uncropped version to show the actual field of view on the APS-C T1i. These (all @ 800iso, 22@240s,11@300s & 7@360s) w/ the CLS clip in, were grabbed on different sessions, and included a meridian "flip" (the flip was actually from a different session), so shows the frame stacking lines when registered & stacked in DSS.

 

Did an "L" layer, so it's an LLRB. Not a great result, yet shows potential...also have two more step downs that could be used to reduce 52 to 46 and 46 to 43

 

180mm-2ring-Orion-uncropped.jpg

 

Link to the Cropped full size here: http://api.ning.com/...Cropped1920.jpg



#2 Jerry Lodriguss

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Posted 17 February 2016 - 02:47 AM

I use step down rings too with my 180mm, but note that there's a point of diminishing returns as you will get mechanical vignetting.

 

You probably should also shoot flats if you use step down rings.

 

Jerry



#3 orlyandico

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Posted 17 February 2016 - 03:09 AM

I am using a 77mm - 62mm on my Canon 70-200/2.8L and it shows mechanical vignetting.  That's only at f/3.22



#4 HarknessAstro

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Posted 17 February 2016 - 04:27 AM

Beautiful work! I love the vastness of the shot with these two amazin regions in view. Keep up the awesome work and I hope that all of your tests continue to work out well!



#5 nickatnight

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Posted 17 February 2016 - 05:12 AM

That's an interesting image with nice framing. Hope to do some wides of the region one day.



#6 SunBlack

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Posted 17 February 2016 - 11:18 AM

nice.



#7 Greg S

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Posted 17 February 2016 - 12:56 PM

That's great for a DSLR lens.  I've been eyeing some of the Nikkor 200mm f/2.8 ED lenses with manual focus.  They are a bargain on eBay at around $300.  In my case I would just connect it to a Nikon D750 and be done.

 

How do you mount the camera and lens?  Do you use rings?

 

Greg



#8 SKYGZR

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Posted 17 February 2016 - 01:43 PM

@ Jerry...how far have you stepped down w/rings? Guess I'll just have to experiment to find out where the mechanical vignetting might happen. I'll try some "sky" flats when out for extended periods, or when I have time before Solset.

 

@ Greg S, yes, the lens is mounted in rings, and for this test, was attached to the finder bracket of the ED80 w/a ball head that makes framing relatively easy.

 

I would like to try this someday on the I-Optron tracker, yet it might be a bit heavy for that unit..yet won't know till I try.



#9 margin_walker

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Posted 17 February 2016 - 05:09 PM

I would consider that a great result!



#10 epsilon160

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Posted 19 February 2016 - 10:07 AM

Very interesting! So, the intention in using filter step-down rings is to mask the aperture to control aberration without inducing diffraction effects from the 180's diaphragm?



#11 SKYGZR

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Posted 19 February 2016 - 01:49 PM

Very interesting! So, the intention in using filter step-down rings is to mask the aperture to control aberration without inducing diffraction effects from the 180's diaphragm?

Yes..this tactic can be used on pretty much any camera lens. I've also got rings for some of my older Pentax Glass to try on also, yet haven't had that opportunity.



#12 Erik Bakker

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Posted 19 February 2016 - 01:53 PM

Stunning shot of the Horse Head and M42 region  :bow:




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