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Optical quality of Carton 70 mm, f/4.5 achromat

refractor optics ATM
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#1 geovermont

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Posted 11 January 2017 - 02:02 PM

Hi all,

I'm considering using one of the 70 mm, 315 mm focal length, f/4.5 air-spaced, coated achromats from Carton for a terrestrial spotting scope. I intend to keep the total magnification to between 13 x and 26 x, but still, this is a pretty short focal length and I'm wondering if it's likely that I could pull this off without excessive spherical and especially chromatic aberration. The lens is not expensive, but if it's definitely going to perform poorly in this application, then I'll search around for something else.

Thanks,

George



#2 G.Richard

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Posted 11 January 2017 - 02:24 PM

I own numerous Carton scopes George and found they all perform excellently.  I would have to think yours should not be a different than mine.  I have two 60mm f6 scopes that show no false color when using them on the moon.  


Edited by G.Richard, 11 January 2017 - 02:24 PM.


#3 geovermont

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Posted 11 January 2017 - 08:48 PM

Thanks,

It's very helpful to hear that similar lenses have worked well for a spotting scope. I'll give it a try.

George



#4 oldtimer

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Posted 12 January 2017 - 09:10 PM

I used this lens (from Sheldon) to make an  RFT. It is a very good lens. With my Clestron 25mm 60 degree 1.25" eyepiece views are excellent to the edge.


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#5 geovermont

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Posted 13 January 2017 - 10:37 AM

That's quite helpful. It will take me a while to put this together, but I'll be sure to post my experience with constructing this scope.

 

George



#6 Chuck Hards

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Posted 13 January 2017 - 04:51 PM

Post pics!  I've had one of these lenses mounted for 18 years.  It just blows me away every time I use it. 

 

I'll post pics if I can find them.



#7 terraclarke

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Posted 13 January 2017 - 09:29 PM

I have one from Sheldon. I highly recommend it. Its great as a very sharp daytime spotter and a nighttime RFT. It is extremely small and portable. I have a 1.25" dielectric mirror diagonal and a 1.25" 45degree correct image prism diagonal and several eyepieces ranging from 27mm to 8mm giving me a range in magnifications from 12X to 40X as an extra small, extralight travel kit. Even an over-aperature solar filter. Mine has a 1/4-20 mounting block on it and can be used on a small photo tripod.



#8 oldtimer

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Posted 14 January 2017 - 10:55 AM

Terra;

 

I recognize that last line in your signature line as being from an old sci-fi movie, which one was it?


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#9 Taosmath

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Posted 14 January 2017 - 10:59 AM

A couple of people have mentioned 'Sheldon' as a supplier for these lenses.  Could someone please tell me the complete name of the company as I can't find anything via google (other than quotations from Sheldon Cooper on Big Bang theory.....)



#10 geovermont

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Posted 17 January 2017 - 11:22 AM

Sorry for the delay--didn't see our post. Look in the Classifieds on this site for items for sale by MASILMW . At the moment, he has a 60 x 900 mm achromat and a couple of other items up for sale. I ought an item from him last year that worked out well and he gets good ratings. He  puts some interesting pieces up for sale regularly.



#11 terraclarke

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Posted 17 January 2017 - 07:58 PM

Terra;

 

I recognize that last line in your signature line as being from an old sci-fi movie, which one was it?

The Thing from Another World, 1951, RKO Studios, directd by Howard Hawks



#12 terraclarke

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Posted 17 January 2017 - 08:00 PM

A couple of people have mentioned 'Sheldon' as a supplier for these lenses.  Could someone please tell me the complete name of the company as I can't find anything via google (other than quotations from Sheldon Cooper on Big Bang theory.....)

Sheldon Faworski (MASILMW)



#13 Taosmath

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Posted 18 January 2017 - 11:25 PM

Thanks for the leads.  I tracked him down and he gave me a link to his ad: http://www.cloudynig...-in-metal-cell/.

 

$25 Shipped for a 70mm f4.5 sounds like too good a project opportunity to miss, so I've grabbed a couple - one for a finder and one for a small RFT.



#14 mikerepp

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Posted 19 January 2017 - 10:01 AM

The Thing from Another World, 1951.  One of the best scifi movies ever!  Love that movie.




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