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Patent for Questar 700 lens?

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19 replies to this topic

#1 RichA

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Posted 02 June 2020 - 07:08 PM

May have been posted at some point before:

 

https://patents.goog...matic telescope

 

 


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#2 TerryWood

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Posted 02 June 2020 - 09:01 PM

Thanks for posting this. I posted the Questar Wide Sky Telescopes ad from 1983 in my Questar 700 Moon thread. It appears to be a Q700 with the Questar diagonal on the back. It's hard to tell if there is an additional focusing mechanism. Have you ever seen one of these?

 

V/R

 

Terry

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Edited by TerryWood, 02 June 2020 - 09:02 PM.


#3 Optics Patent

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Posted 02 June 2020 - 09:16 PM

A Wide-Sky Seven would be quite a rarity.
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#4 RichA

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Posted 02 June 2020 - 09:19 PM

A Wide-Sky Seven would be quite a rarity.

I had one.  It was basically a preview of the current "Astro" a Questar with the rear control back removed but the optics were standard Q7 optics.  When you remove the control back you shrink the distance to the primary mirror from the eyepiece "lessening" the focal ratio. 


Edited by RichA, 02 June 2020 - 09:21 PM.

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#5 RichA

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Posted 02 June 2020 - 09:19 PM

Thanks for posting this. I posted the Questar Wide Sky Telescopes ad from 1983 in my Questar 700 Moon thread. It appears to be a Q700 with the Questar diagonal on the back. It's hard to tell if there is an additional focusing mechanism. Have you ever seen one of these?

 

V/R

 

Terry

No, but it's interesting they could get the focus far enough out the back to use with a diagonal, unless the diagonal had optics in it.


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#6 TerryWood

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Posted 02 June 2020 - 09:48 PM

I have a Questar diagonal on on the back of my Q700 (it screws on) and focusing is not a problem. There were no additional optics inside the diagonal other than the mirror. However, I thought maybe the Wide-Sky version had a rack & pinion focuser too instead of twisting the barrel to focus like a standard Q700. A fine focus mechanism sure would be handy.

V/R

Terry

Edited by TerryWood, 02 June 2020 - 09:52 PM.


#7 ianatcn

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Posted 03 June 2020 - 12:30 PM

I have a Questar diagonal on on the back of my Q700 (it screws on) and focusing is not a problem. There were no additional optics inside the diagonal other than the mirror. However, I thought maybe the Wide-Sky version had a rack & pinion focuser too instead of twisting the barrel to focus like a standard Q700. A fine focus mechanism sure would be handy.

V/R

Terry

Hi Terry,

 

I have a Q700 that has a fixed diagonal on the back (a thumb screw when loosened allows the diagonal to be rotated).  The unit is focused by rack and pinion that moves the corrector back and forth.  This allows for focus to be achieved speedily. The wheels on the rack have the Questar logo on them.  I purchased it second hand some time ago thinking I was getting a Q700 with a visual back but it appears I have the wide field model. I have not seen another Q700 to compare it with. What do you think?

 

Ian


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#8 MikiSJ

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Posted 03 June 2020 - 01:02 PM

My Wife worked with and was friends with a very capable PhD Optics Engineer. In the late '70s he could have had the choice of any telescope but he chose to make an 8" f/3 - 3/5 which he gave to me. 

 

His commercial choice was a Questar and I have always respected that choice based upon his wealth of knowledge of anything regarding light and optical systems.


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#9 Optics Patent

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Posted 03 June 2020 - 01:07 PM

Ian, could you post a photo of the unit? If that’s a challenge PM me for an email and I can post.

As a tech vocabulary nerd (my day job) I can point out that the 700 focusing mechanism with the big rotation collar is best defined as helicoid focusing, like most traditional camera lenses. Every nut and bolt is essentially a helicoid.

The only Questar rack and pinion focus that comes to mind is in the fast focus II model with the focus knob on the side of the control box. Most use the threaded shaft to push the mirror, of course.
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#10 TerryWood

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Posted 03 June 2020 - 01:58 PM

Hi Terry,

 

I have a Q700 that has a fixed diagonal on the back (a thumb screw when loosened allows the diagonal to be rotated).  The unit is focused by rack and pinion that moves the corrector back and forth.  This allows for focus to be achieved speedily. The wheels on the rack have the Questar logo on them.  I purchased it second hand some time ago thinking I was getting a Q700 with a visual back but it appears I have the wide field model. I have not seen another Q700 to compare it with. What do you think?

 

Ian

Ian,

 

Wow, that sounds like quite a find! Like Ben suggested, I would really like to see a picture of that! I wonder how many of those are out there. 

 

V/R

 

Terry



#11 ianatcn

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Posted 03 June 2020 - 05:17 PM

Will try to take some pictures tomorrow. Mine looks exactly like the one in the ad that Terry posted. The r&p mechanism works on the front lens section replacing the helical system that most telephoto lenses employ. You can just make out the focus wheel in the ad. sitting under the tube towards the front of the section containing the primary mirror. The primary mirror is fixed.


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#12 TerryWood

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Posted 03 June 2020 - 05:23 PM

Looking forward to seeing them! Sounds like a unique Questar you don't see everyday. Thanks! V/R Terry

#13 ianatcn

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Posted 04 June 2020 - 05:55 AM

The following posts contain a few images of the Questar 'Wide Field' model.  It has been well used judging by the scuffs to the paintwork. Internally though, it is very clean with no signs of any marks or degradation of the coatings.  The diagonal at the back is fixed and integral to the instrument but can be rotated to required viewing angle by slackening the small brass thumb screw.

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#14 ianatcn

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Posted 04 June 2020 - 06:15 AM

Rear view showing diagonal assembly.

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#15 TerryWood

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Posted 04 June 2020 - 08:00 AM

All I know is that I want one now! That is a neat looking unit! Thanks for taking the time to post these pictures. I imagine that r & p focuser gives you much better control over fine focus. I really like it!

V/R

Terry

Edited by TerryWood, 04 June 2020 - 08:01 AM.


#16 Optics Patent

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Posted 04 June 2020 - 09:07 AM

Very cool - totally new to me!

I'm pretty sure that the diagonal is threaded to the tube that extends form the plate with the four screws.  Those screws remove to allow removal of that tube, with its captured front flange that is greased to allow smooth rotation when the set screw is loosened.


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#17 Optics Patent

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Posted 04 June 2020 - 09:16 AM

The price lists in 1990 (the final year the 700 was offered) listed a "fast focus, rack and pinion" for the 700 for about 30% of the broadband 700 price.


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#18 TerryWood

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Posted 04 June 2020 - 09:40 AM

My diagonal threads on as well, though not as snugly as that one appears. I still have threads left to go after it is on there tight. 

 

V/R

 

Terry



#19 ianatcn

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Posted 04 June 2020 - 09:41 AM

Ben, That makes sense as the r&p takes you between extremes of focus in just over half a turn of the wheel.  

 

Terry, it is a buttery smooth action to the focus wheel and very quick to nail perfect focus.

 

Will try it out with some other eyepiece when we next get a clear night.


Edited by ianatcn, 04 June 2020 - 10:19 AM.

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#20 TerryWood

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Posted 04 June 2020 - 11:13 AM

Mine seems to work best with the 24mm & 16mm eyepieces. The 32mm has a "kidney bean" effect on my eyes which results in blackout areas unless your eye is placed in just the right position.

 

V/R

 

Terry




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