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Acquired an old Questar Field Model, new to telescopes!

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#1 Seraphim

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Posted 29 May 2022 - 02:24 AM

Hi Forum, 

 

I have as the title suggests acquired a Questar field model and

 

Edit: it appears my post has gone, the joys of mobile browsers! I will retype it later! 


Edited by Seraphim, 29 May 2022 - 02:32 AM.


#2 Seraphim

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Posted 29 May 2022 - 03:34 AM

Hi Forum,

 

Hopefully this is the right place for the "new" scope.

 

So, previously I used a little Celestron Astromaster 70AZ I bought used to take photos of the moon for the kids school project.

 

I have acquired a Questar  Field Model and was hoping the brain trust on the forum could shed some light on it!

 

I put some pictures of it in my gallery, if I am able to share that? 

 

The scope came with the worlds heaviest tripod,  but everything works, it just needs stripping down and cleaning thoroughly.

 

The scope itself isn't in the official case,  and just appearance be the most basic model.  The hand etched number on the bottom is F-CV-2429-88  which I assume is come kind of serial number?

 

There are a few eyepieces  with the scope. Fitted is a 24mm Brandon, and there are 1.5 , 2, ,8 (lens loose on this one), 12, 16 and 32mm eyepieces  in the case. I have no idea what the other items are if anyone can shed some light from the pictures? It also comes with the blue Questar manual (printed 1976 version) which I've read through a little.

 

I set it up and managed to focus in on some birds in the roof a few doors down, the inbuilt 2x Barlow seemed to work, as does focus and the mirror flip to move between through and 90 degree view. I think the lens is a little dirty, and the outside of the above looks as it the finish is poor.

 

The 24mm eyepiece won't come loose from the scope, it unscrews the silver part it is attached to. I am assuming its stuck for the moment as until I know more,  I'll hold off on twisting things in case I damage them!

 

I'd like to see how easy/expensive it is to get the scope into good working order, or if it's not worth trying to recover. From the sound of it, a good condition Questar should give me some good views and I'd like to be able to show the kids the moon and stars in more detail than the Celestron does. 

 

I'm in Australia so am not sure what the options would be for local servicing on this.



#3 Optics Patent

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Posted 29 May 2022 - 07:46 AM

The eyepiece should unscrew from the holder. There’s no downside to using lots of force, but apply the force to the holder’s ring closest to the eyepiece and NOT the smooth cylinder closer to the scope.

The 88 at the end of the serial number is actually BB for premium broadband coatings.

You have a nice collection of eyepieces nearly as valuable as the scope. The 1.5 is a Barlow lens for use with a camera mounted at the rear port with a “camera coupling” that is easy to find used or buy new.

The loose lens in the eyepiece can usually be fixed by gently tightening a ring internal at the bottom of the eyepiece.

Post photos. I suspect that the finish issues are due to the original case foam that degraded and then corroded the aluminum and paint. This can be reduced with some cleaning but not eliminated so don’t try too have and keep it gentle.

Include photos of the optics to assess the cleaning issues. Hopefully the only “dirt” is on the front surface of the corrector because the BB coatings can’t be restored and any internal surface flaws are usually coating failure.

You probably don’t need any service and everything is probably working as well as is can, once you get that eyepiece out. (A small strap wrench should do).

#4 Toddeo

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Posted 29 May 2022 - 08:05 AM

You have a Questar "Field" model with a Cervit mirror(CV) and Broad Band coatings. You have a nice set of eyepieces and both Dankin barlows(1.5x and 2x). The scope should clean up nicely. It is definitely foam case degradation on everything.  The optics look nice-should clean up with very little effort. On the scope tube you can use soapy water and or automobile, very mild scratch remover/polishing compound- then apply auto polish/wax. I've had a few Questar tubes and dew shield clean up beautifully.  You have a very nice set up- ENJOY!!!!!



#5 JamesMStephens

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Posted 29 May 2022 - 09:33 AM

I've used Flitz polish on my Questar's base, it's completely non-abrasive and recommended for other surfaces, and it leaves a thin carnauba wax finish.  You don'y have the base (since you have a Field Model), but Flitz should work on the other surfaces.

 

Jim

 

https://tinyurl.com/bdd2dcsn



#6 Gregory Gross

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Posted 29 May 2022 - 02:02 PM

Having had a look at your photo gallery, I have a few additional comments:
 
The "CV" in your serial number F-CV-2429-BB indicates that your scope has a primary mirror made of Cer-Vit, which was a material with greater thermal stability that Questar used from the late 1960s until it switched to Zerodur in the early 1980s.
 
The "2429" in the S/N is the production number. Using data posted in the files collection of the Questar User Group along with other information, I built up a few serial number tables in an effort to enable folks to determine roughly when their scopes were made. A production number of 2429 would put this scope's production year around 1978 or so.
 
This photo shows a number of accessories:

  • Camera coupler: that little part alone runs well over US $200 new. If you're interested in getting into more proper photography with your Field Model, you may consider getting something like a small mirrorless camera and an adapter. I use a Canon M200 and a Fotasy M42-to-EOSM adapter with my Questar, and I have tons of fun taking photos of everything from astronomical objects to wildlife in the backyard.
  • Attached to the camera coupler looks to be the shortest of the three extension tubes that would have come with the set. Have a look at this page for an illustration.
  • 2x and 1.5x photographic Barlow lenses that I believe are meant to be used with the camera coupler.
  • It also looks like you have an eyepiece mounting ring, which allows you to do eyepiece projection photography by mounting an eyepiece inside the extension tubes.
  • A straight-through roof prism Questar image erector.
  • Off-axis solar filter. The mirror-like filter near the pick-off finder mirror is a solar filter that is meant to be engaged when using your scope for solar observing. Be sure to check to see if all the solar filters are in good enough condition to be used, and, if so, be sure to have that finder solar filter flipped into position.
  • A nice set of Questar Brandon eyepieces.

You noted a blue telescope instruction booklet. Definitely read it thoroughly. It'll answer a lot of questions. There is also would have been a second-part matching booklet on using a camera with a Questar. It doesn't sound like you have that second part. While written during the days of film photography, it'll answer a lot of questions about connecting a camera to your scope and what accessory does what. There is a PDF copy of that instruction booklet posted at the Questar User Group that I noted above. Membership to access it is required but is free.
 
That's significant because that's the year that Questar switched their placement of the secondary mirror spot (the mirrored surface behind that painted spot in the middle of the corrector lens at the front of the scope) from the outside surface of the lens to the inside surface. Kind of a long story as to why Questar did that (the short version is that patent constraints were responsible for the initial design), but your Field Model likely has the more recent design. I could be wrong, but if I'm eyeballing your photos correctly, it looks like you indeed have that more recent design.
 
If you should decide to clean that front corrector or any other optical surface, easy does it. Use something like a soft camel hair brush made for camera lenses and gently sweep off any gritty dust. Then use an optical cleaning solution and either sterile cotton balls or PecPads. Don't contact that painted spot with your optical cleaning solution, as you may ruin the finish. Cleaning optics is a topic in and of itself. Having a little dirt on the optics is far, far better than scratching or otherwise damaging the optics. When in doubt, leave it alone.

 

You may consider contacting Questar for servicing options. I'm not sure what the implications are for international shipping, but they deal with customers all over the world, so you won't be the first international customer they've done business with.
 
Have fun with your new (to you) scope, and let us all know how things progress!


Edited by Gregory Gross, 29 May 2022 - 02:04 PM.


#7 Optics Patent

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Posted 29 May 2022 - 09:51 PM

Photos make it look like you have a very nice setup. I’ve had several examples of the degraded black anodizing like that and you can make it a little better but it won’t get a lot better. Go east and accept it as part of the history. One of the repair threads linkages in my bio will have a post with a link to the product that conceals bright scratches in black anodization. (Aluminum Black by Birchwood Casey).

#8 Seraphim

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Posted 30 May 2022 - 08:19 PM

Thank you to everyone who has given me a lot of food for thought! I will see if I can take some better photographs on the weekend of the lenses and inside of the scope itself. 

 

First tasks would be to obtain suitable camera cleaning products  and to do the gentlest of exterior cleans as well to see what condition the outside is in, and to get hold of  a strap wrench to release the 24x eyepiece from the tube. 

 

Hopefully once thats done I'll be able to post some more images, and see as well if the coatings etc. are still in good condition. 

 

Thanks again!


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#9 Seraphim

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Posted 19 June 2022 - 07:58 PM

Finally got to try out the Questar on a clear night June 14th "Supermoon". Put the images up in a new gallery folder, they're nothing compared to what some people put up on here but I'm pleased at how they came out. The tiny moon is via the finder. 

 

Took me 3 minutes to realise I'd left the lens cap on, thought it was broken! I know!  The questars point of genius is the one eyepiece for both the sighting lens, the main eyepiece and the 2x barlow through 1 eyepiece. Absolute brilliance! Once I'd taken the lens cap off (!) I managed to get the moon in focus using the 24mm eyepiece and took a handheld image of the moon using my phone, But I also have a Nikon DSLR and will be buying a t mount adaptor to go on to the scope, as it came with the camera coupler and the 1.6 and 2x barlows.  

 

I couldn't see any damage to the coatings but will also take some images 'down' the scope to post so the expert eyes here can let me know if the internal systems seem good. Focus knob, internal Barlow lens, and 90 degree prism movement mechanisms all seem to work well without any effort, but I will be trying to source a decent pelican style protective case for it as the old case it came in isn't designed for it so it is just wrapped in towels. Not tried to clean it yet either!! very wary of trying to 'force' anything, it's amazingly well engineered! Its a bit like the Gransfors Bruks of telescopes!

 

 

 

Flicking over to the internal barlow I couldn't work out why the image just 'whited out' until I realised that it was at an effective 80x magnification so the moon more than filled the objective!. 

 

Through the eye the image was a lot shharper than the photo I was able to take, although I could see a mark on it which I think  is on the eyepiece. 

 

Also, finally able to remove the 24mm, took the silver and eyepiece part  to the local DIY store to get a strap wrench, and on showing them what I needed to do, undid it by hand after all that!  So also have a choice of the lenses that came with it and will be trying those out and also looking for some dark sky sites nearby once I have checked out and bought some lens cleaning materials from my local camera store and fitted the camera coupler!  Thank you everyone for your comments and knowledge, I'm looking forward


Edited by Seraphim, 20 June 2022 - 12:40 AM.

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#10 Gregory Gross

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Posted 19 June 2022 - 08:41 PM

Very nice — thanks for sharing your experience with us!

 

I also have a Nikon DSLR and will be buying a t mount adaptor to go on to the scope…

Bear in mind that the Questar camera coupler has M42 x 1.00 thread pitch. If I’m not mistaken, T-mount threads have a 0.75 thread pitch. I think you’ll want something like this. Could someone with a Nikon DSLR confirm that that’ll work? I’m not sure if an intermediate adapter ring is necessary.

 

Also check out this camera threading article by Rob Pettengill.



#11 Optics Patent

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Posted 20 June 2022 - 10:20 AM

I'll repeat my constant advice:  If threads fit but get tight after ~3/4 turn, you have the wrong thread pitch and it will destroy it to force it.  Wishing harder doesn't help either.


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#12 Seraphim

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Posted 21 June 2022 - 08:47 PM

I'll repeat my constant advice:  If threads fit but get tight after ~3/4 turn, you have the wrong thread pitch and it will destroy it to force it.  Wishing harder doesn't help either.

Thanks, Yes i'm always cautious of forcing anything, especially if its this well engineered, anything other than a perfect fit means its the wrong thread/size!  Will take some more measurements and take along the parts to the camera specialist to ensure I get the right part!  




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