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How to adjust the Questar finder mirror

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#1 Optics Patent

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Posted 27 November 2016 - 03:07 PM

Upon acquiring a used 3.5 Field Model, I decided to take it down and clean it up.  This involved removing the finder mirror with its plate for inspection and cleaning, and for re-brushing the mirror bracket which had gained some rust spots.  This is not the official procedure, but just one I figured out for myself.  Being a patent attorney, I rarely have the chance to write up technical explanations, so here goes:

  1. Remove the glue that holds the screws in position.  This was brittle and flaked away on mine, and it picked away using the universal gentle scraper (fingernail) without trouble.  Fresher glue might require a solvent.
  2. SKIP to Step 12*** if not removing the mirror.
  3. If removing the mirror be warned that replacing it is a big pain without some kind of factory fixture I presume exists.  Don't bother removing the mirror unless you need to.
  4. Mark the mirror so you know which way is up.  Mine was offset on the plate, and there was clearly a right way to be sure it's centered on the bracket.  Guess which way I reinstalled mine the first time!
  5. Unscrew the four screws.  There is a bent rectangular leaf spring between the bracket and the mirror plate, and this will "sproing" when one of the screws comes out.  Be careful not to lose anything.
  6. When reinstalling, your first question will be: "Which way did the spring go?"  The answer is first that the long way goes horizontally.  The ends will be positioned between the screw shafts so that the spring might slide laterally, but is constrained vertically. On my reference scope (not the one I was working on), the "belly" (middle) of the spring presses against the middle of the mirror plate ("belly rearward").  But I went the other way ("belly forward"), putting the ends against the plate, thinking that it avoids bending stresses on the mirror plate, and concentrates the forces near the adjustment screw locations.  It's likely that it's easier to reinstall things belly rearward and I would do it this way next time - see the reasons below.
  7. Get out your curse word Thesaurus.  You need three or four very tiny and nimble hands to reinstall without a fixture.  Seriously consider making a fixture with a circular aperture for the mirror, and holding the scope at a 45 degree angle so that the mirror will be facing straight down.  This would be a sheet of material that is narrower than the inside the the bracket and has a hole for the mirror, or otherwise holds the mirror plate in position.  It will extend out so you can hold onto it.  It could be a child's soap bubble wand, for example.  Maybe the factory simply has a cap that goes over the mirror and is removed after install.
  8. Apply a little film of grease to the spring steel, which might be prone to rust, and wants to be able to slide during adjustments.
  9. Position the spring centered laterally and between the screws - a dab of grease sticking the belly to the mirror plate will hold things in place, and is a good reason to do this the "belly forward" orientation.
  10. If you're doing this without a fixture, try installing the two screws on one lateral end, then wiggling the spring in place with a tweezers.  If you're doing this belly rearward, there is a frustrating tendency for the spring's end to overshoot the edge of the mirror plate so you have to start over.
  11. Reclean the mirror you so carefully cleaned when it was out, now that your fat fingers have made it a mess.  Or remove the cap you cleverly used.
  12. ***SKIP TO HERE FOR AIMING.
  13. Tighten all the screws until they resist slightly (gentle, not tight)
  14. Loosen each screw two turns (or pick an amount that's in the middle range for each screw).
  15. Pick a telescope aiming point in the magnified telescope view and center it.
  16. Switch to the finder and note the location of the telescope aiming point.  Remember that the finder should be aimed at a point 3" lower (in order to generate parallel alignment for celestial objects).  This is the simple approach to working in daylight, even with an indoor aiming point across the room.  There's no need for a celestial target and tracking.  If you pick a phone pole a block away the 3" won't make much difference, and if it's a nearer target you should be sure of the offset, perhaps by posting a target with aiming points 3" vertically apart.
  17. To adjust the finder, think diagonally, not X and Y axis.  Don't be tempted to adjust two side screws for horizontal shift, etc.  Each adjustment of one screw requires an opposite and equal adjustment of the diagonally opposite screw.  Loosen first, then tighten the diagonally opposite one - otherwise, you'll be twisting the mirror plate into a potato chip.
  18. When you get close to aligned, while viewing the finder image use your jeweler's screwdriver (or a toothpick to be safer) to successively nudge each mirror plate upper corner to compress it against the bracket (squeezing the spring).  You should see only a minor shift.  On one corner you'll probably get more of a noticeable floppy shift because those two diagonal screws are slightly loose relative to the other pair, and the plate is wobbling like a washing machine with misaligned feet.  Just like you adjust the loose foot of the machine until it snugs against the floor, adjust the loose screw until the wobble goes away (but not so tight that it generates wobble in the other side).  Then repeat and fine tune the aiming until you'[re happy and everything is stable.
  19. I used an old eyepiece with peripheral pointers at the quadrants.  Good enough is good enough for me, as getting the object close to the center of the finder field will put it in view in the magnified view.  If you don't have a clear center point when you use the finder, a small error in alignment won't make much difference in practice.  Those who want more precise aiming can use reticles with crosshairs or a guiding eyepiece, or large circular targets for aiming the finder (with a scope aiming point 3" above the circle's center).
  20. When satisfied, apply a sealant to the screw heads.  Something readily removable like nail polish makes sense to me, as opposed to a version of Loctite of uncertain removability.

 

I'll be happy to update this with suggestions or corrections, or to hear where my blind amateur effort might be misguided.


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#2 Les Aperture

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Posted 28 November 2016 - 06:08 PM

20. "Sally Hansen" brand clear finger nail polish works great; inexpensive and can be found most anywhere.


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#3 Optics Patent

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Posted 28 November 2016 - 06:26 PM

Even cheaper than Sally Hansen is whatever your wife already has on hand. Or, to be nonsexist, whatever your spouse has on  hand.



#4 Optics Patent

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Posted 22 January 2017 - 03:33 PM

I have updated the formerly-challenging installation process after I just installed my second mirror using much more sensible.  This process assumes you have already removed the mirror bracket from the telescope.  Below is the full process with all the changes:

  1.     Remove the glue that holds the screws in position.  This was brittle and flaked away on mine, and it picked away using the universal gentle scraper (fingernail) without trouble.  Fresher glue might require a solvent.
  2.     SKIP to Step 12*** if not removing the mirror.
  3.     If removing the mirror note that replacement is easy, but requires some care and a simple fixture you can make.
  4.     Mark the mirror so you know which way is up.  Mine was offset on the plate, and there was clearly a right way to be sure it's centered on the bracket.  Guess which way I reinstalled mine the first time!
  5.     Unscrew the four screws.  There is a bent rectangular leaf spring between the bracket and the mirror plate, and this will "sproing" when one of the screws comes out.  Be careful not to lose anything.  Now, your mirror is our for cleaning, or re-coating.  I was happy with Jeff Decker at majestic-coatings.com who did it for $25 including shipping.
  6.     When reinstalling, your first question will be: "Which way did the spring go?"  The answer is first that the long way goes horizontally.  The ends will be positioned between the screw shafts so that the spring might slide laterally, but is constrained vertically. On my reference scope (not the one I was working on), the "belly" (middle) of the spring presses against the middle of the mirror plate ("belly rearward").
  7.     Make a fixture out of a small box.  Two slots 10mm wide by 40mm long, separated by a 25mm bridge.  These dimensions are not critical, you just need to get the legs of the bracket to dangle down into the slots, straddling the bridge. Practice installing the bracket into the box fixture to be sure you have the dimensions right.  Weight the box for stability with nuts and bolts inside.
    1 Setup
  8.     Cut a strip of optical cleaning paper to drape over the bridge into the slots.  The mirror will rest face down on this strip.  Apply a dot of grease to the back of the mirror plate.
    2 grease
  9.     Rest the belly of the mirror on this to squeeze out any excess that you should remove with a Q-tip. The grease will help the spring stay in place.
    3 spring
  10.     Now, you'll move the mirror and spring setup aside to another cleaning sheet, and you'll drop the bracket into position. Set up a bright flashlight to shine parallel to the assembly so you'll be ready for the next step.  Insert two screws into diagonally opposite corners of the bracket.
    4 lighting
  11.     Carefully position the mirror under the bracket with the screw, without dislodging the position of the spring.  Nudge the spring as needed to align it. View through the two open bracket holes to align with the mirror plate holes.  When aligned, press down on the bracket to compress the spring.  Verify the holes remain aligned and maintain pressure (farther down than you think, you don't have to bottom out but you probably can) and use your jeweler screwdriver to turn the screw to engage the threaded hole in the mirror plate for a few turns.  Don't release the pressure on the plate before you turn the other screw.  You may release the pressure and exhale.  Install the other two screws.  Remove assembly from fixture.  Visually verify that the spring hasn't crept out. 
    5 align
  12.     ***SKIP TO HERE FOR AIMING.
  13.     Carefully drive all the screws until they offer only the slightest resistance. Reinstall bracket on scope.
  14.     Loosen each screw two turns (or pick an amount that's in the middle range for each screw).
  15.     Pick a telescope aiming point in the magnified telescope view and center it.
  16.     Switch to the finder and note the location of the telescope aiming point.  Remember that the finder should be aimed at a point 3" lower (in order to generate parallel alignment for celestial objects).  This is the simple approach to working in daylight, even with an indoor aiming point across the room.  There's no need for a celestial target and tracking.  If you pick a phone pole a block away the 3" won't make much difference, and if it's a nearer target you should be sure of the offset, perhaps by posting a target with aiming points 3" vertically apart.
  17.     To adjust the finder, think diagonally, not X and Y axis.  Don't be tempted to adjust two side screws for horizontal shift, etc.  Each adjustment of one screw requires an opposite and equal adjustment of the diagonally opposite screw.  Loosen first, then tighten the diagonally opposite one - otherwise, you'll be twisting the mirror plate into a potato chip.
  18.     When you get close to aligned, while viewing the finder image use your jeweler's screwdriver (or a toothpick to be safer) to successively nudge each mirror plate upper corner to compress it against the bracket (squeezing the spring).  You should see only a minor shift.  On one corner you'll probably get more of a noticeable floppy shift because those two diagonal screws are slightly loose relative to the other pair, and the plate is wobbling like a washing machine with misaligned feet.  Just like you adjust the loose foot of the machine until it snugs against the floor, adjust the loose screw until the wobble goes away (but not so tight that it generates wobble in the other side).  Then repeat and fine tune the aiming until you'[re happy and everything is stable.
  19.     I used an old eyepiece with peripheral pointers at the quadrants.  Good enough is good enough for me, as getting the object close to the center of the finder field will put it in view in the magnified view.  If you don't have a clear center point when you use the finder, a small error in alignment won't make much difference in practice.  Those who want more precise aiming can use reticles with crosshairs or a guiding eyepiece, or large circular targets for aiming the finder (with a scope aiming point 3" above the circle's center).
  20.     When satisfied, apply a sealant to the screw heads.  Something readily removable like nail polish makes sense to me, as opposed to a version of Loctite of uncertain removability.


#5 Optics Patent

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Posted 28 March 2017 - 10:50 AM

Tip: If your scope has older Bristol-drive screws holding the mirror bracket to the control box, because you will not have straight tool access to two of them you will have to unscrew them by 1/6th turns, removing and reinserting the tool for each.  It's a slow process and risks a tool mis-insertion along the way and screw damage.  One solution for this is to order Questar's current Allen screws they now use instead of Bristol (I think the switch-over happened in the 1980s).  These enable the use of a ball end (Bondhus) 2mm Allen wrench that can drive at an angle, greatly speeding up the process for re-installation, and for future service.  The side benefit is that those Bristol screws are irreplaceable, and will be useful for you or a friend to replace missing or damaged Bristol screws in a restoration project.  The only present alternative for a missing Bristol screw is to replace it with an Allen (making screw damage likely from tool mistakes - replacing all Bristols with Allen is more sensible).

 

You can buy those screws anywhere, and searching "screw #3-56 1/4" stainless allen" will get you a lifetime supply (100) on Ebay for ten bucks.  Or message me and I'll send a few.

Incidentally I'll pay $1 (or trade 10 matching Allen screws) per Bristol screw from a Questar in undamaged condition (and will send any to CN friends on request at no charge - in the spirit of restoration of as many Questar scopes as possible).

 

There is a temptation when (if) I sell an older but not historic early vintage scope to first harvest its Bristols and then honestly advertise it as: "All Bristol-drive screws have been upgraded to modern stainless steel Allen screws to facilitate service with modern tools, and to be consistent with current Questar factory practices". 



#6 Optics Patent

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Posted 22 July 2017 - 02:20 PM

I just did a recorded mirror install and have a couple new tips:

1. If you are installing Bristol screws and want to avoid the slow process of turning them 1/6 rotations at a time you MIGHT be able to cheat with a 2mm ball end bondhus Allen wrench for most of the easy travel but ONLY IF the screw is freely and easily rotating.

2. For more accuracy when aiming use the highest power eyepiece you have.

3. When adjusting the finder image, the image will move diagonally "toward" the screw that you are screwing in, and away when you unscrew.

Edited by Optics Patent, 22 July 2017 - 02:22 PM.

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#7 bmwscopeguy

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Posted 11 October 2017 - 08:02 PM

Hi Ben,

 

I have also found that a Torx head driver, can't recall which # will engage the Bristol flutes without slippage. Unless the screws are seized, the Torx will get them out without marring the Bristols.

 

Cheers

Malcolm



#8 Optics Patent

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Posted 11 October 2017 - 09:39 PM

Good idea. Like a soft wood toothpick an undersized tork wrench will turn loose screws. Careful not to damage

#9 Optics Patent

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Posted 17 May 2018 - 12:10 PM

For mounted scopes, this is probably an obvious but very handy position for positioning the scope when applying the nail polish to the screws.  First remove the entire eyepiece holder.  Be careful because you're nearly touching the dew shield to the base.  45 degrees isn't reachable, but it's close enough.  Also good for picking at the glue in the first place.

 

This 1972 did not rotate on the barrel axis a full 180 (only about 45 in either direction) so I had to swing it through the fork. 

 

IMG 5149
 
For unmounted barrels, an improvised padded box as a cradle works, but a tripod mount and rotating the barrel 180 can do it.
 

 


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#10 Rick McNelly

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Posted 24 April 2020 - 02:58 PM

Thanks for the instructions Ben,

 

Aligned mine today on a far away tree, and it’s pretty close now with my highest mag eyepiece, the 12mm.  We’ll see how it works at night.


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#11 Orion68

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Posted 25 April 2020 - 12:29 PM

My 1981 Questar Standard finder mirror view is quite a bit off center and I'm trying to build up the nerve to adjust it, using your very helpful instructions.

 

If my goal is to only adjust the mirror aiming, do I need to remove the mirror bracket from the control box, or can I just adjust the screws that attach the mirror backing plate to the bracket?

 

Thanks.


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#12 Optics Patent

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Posted 25 April 2020 - 04:31 PM

No need to remove. The instructions tell you where to skip ahead. Simply put it’s:
1. Remove adhesive
2. Fiddle with screws
3. Apply adhesive.
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#13 NC Startrekker

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Posted 25 April 2020 - 04:31 PM

My 1981 Questar Standard finder mirror view is quite a bit off center and I'm trying to build up the nerve to adjust it, using your very helpful instructions.

 

If my goal is to only adjust the mirror aiming, do I need to remove the mirror bracket from the control box, or can I just adjust the screws that attach the mirror backing plate to the bracket?

 

Thanks.

It is extremely easy to do.  Just as simple as aligning any other finder. I guess what gives most pause is removing the drops of adhesive over the four screws and reapplying afterwards. But don't let that get in the way. Again, easily done. 


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#14 Orion68

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Posted 25 April 2020 - 07:59 PM

Thanks Ben & Alan. I'll give it a go!

 

Hoping that it also sharpens up the view in the finder, it's a touch mushy.


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#15 NC Startrekker

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Posted 26 April 2020 - 04:58 PM

Thanks Ben & Alan. I'll give it a go!

 

Hoping that it also sharpens up the view in the finder, it's a touch mushy.

waytogo.gif


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#16 Optics Patent

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Posted 26 April 2020 - 08:41 PM

The mirror adjustment won’t affect image quality.
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#17 Orion68

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Posted 27 April 2020 - 12:09 PM

The mirror adjustment won’t affect image quality.

Good to know. Thanks Ben.



#18 Rick McNelly

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Posted 28 April 2020 - 01:23 PM

My alignment didn’t work well on stars last night, so I realigned it again today.  This time I went to a river park and used a distant radio tower as a target for the 12mm.  Would be easier to do with crosshairs, but I checked several targets after the alignment and think it’s good now.


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#19 Rick McNelly

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Posted 28 April 2020 - 01:26 PM

Thanks Ben & Alan. I'll give it a go!

 

Hoping that it also sharpens up the view in the finder, it's a touch mushy.

 

Mushy finder sounds like the finder isn’t focused.  More info here if you are unfamiliar with it:

https://www.cloudyni...inder-focusing/


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#20 Orion68

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Posted 01 May 2020 - 10:14 PM

Mushy finder sounds like the finder isn’t focused.  More info here if you are unfamiliar with it:

https://www.cloudyni...inder-focusing/

Good thought. When I first got the scope the eyepiece holder/diopter was stuck all the way in one direction and boy was it jammed.  I was able to free it up and it is fine now. My problem may be inside the control box, but I don't know enough about the construction to be sure.

 

Both the image through the finder and the main scope are just a little soft. It is entirely possible it is my old eyes, so may not be the scope at all. My first Q was a 1962 and the images through both finder and main scope were incredibly sharp. But, that was a few years back.

 

The star test reveals good, but not perfect collimation. That would explain the soft view in the main scope but not the finder. I'll do more testing this summer and see if I can get it sorted.


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#21 Rick McNelly

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Posted 02 May 2020 - 04:37 AM

Good thought. When I first got the scope the eyepiece holder/diopter was stuck all the way in one direction and boy was it jammed.  I was able to free it up and it is fine now. My problem may be inside the control box, but I don't know enough about the construction to be sure.

 

Both the image through the finder and the main scope are just a little soft. It is entirely possible it is my old eyes, so may not be the scope at all. My first Q was a 1962 and the images through both finder and main scope were incredibly sharp. But, that was a few years back.

 

The star test reveals good, but not perfect collimation. That would explain the soft view in the main scope but not the finder. I'll do more testing this summer and see if I can get it sorted.

 

I’ve had to clean the finder lens and mirror.  My Q is a duplex and I’ve learned to me mindful of my fingers when mounting/unmounting the Q from it’s base.

 

Hope it’s not your eyes.  My Optometrist had concerns for Glaucoma during a recent eye exam.  I’m scheduled for some kind of test at the end of May.


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#22 Orion68

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Posted 02 May 2020 - 11:02 AM

I’ve had to clean the finder lens and mirror.  My Q is a duplex and I’ve learned to me mindful of my fingers when mounting/unmounting the Q from it’s base.

 

Hope it’s not your eyes.  My Optometrist had concerns for Glaucoma during a recent eye exam.  I’m scheduled for some kind of test at the end of May.

I haven't cleaned the finder mirror yet, I'll be careful to keep my fingers away from it one it gets cleaned up. Thanks and best of luck with your tests at the end of the month Rick.


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