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Q double Transplant

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#1 JonTeets

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Posted 17 August 2016 - 10:38 AM

... whereby the cervit/broadband optics and control control box of a 1978 Questar Field model are exchanged with those of a 1961 standard.

 

Start by removing the control panel from the field model

 

There are four socket head 3-56 1/4" screws to remove.   You can use 5/64 allen wrench.   These were easy to remove.  The top two screws were stuck on the princess and the top left screw had been stripped a bit.   I used a slightly larger torq bit and some force to remove it.   I was able to buy replacement screws on ebay.  You can also find them from albany county fasteners in various lengths:

 

http://www.albanycou...=3-56&Submit=  

 

 

IMG 3664

IMG 3672

IMG 3673

IMG 3674


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#2 JonTeets

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Posted 17 August 2016 - 10:47 AM

Remove the axial port cap

IMG 3678
 
It's a good idea to keep the parts organized.  I use cheap sauce dishes  (except for the stuff in the background.  pay no attention to that.)  
IMG 3679
 
Now take off the focus knob using the bristol spline wrench that shipped with your Questar.  You'll need to do this or the control box won't come off.   If you don't have said wrench Questar will send you one for several bucks.  You can also get them on ebay.  Search for 0.060" bristol spline L wrench.  You might have to select the size  0.06"  from a drop-down.   
IMG 3682
IMG 3683

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#3 JonTeets

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Posted 17 August 2016 - 10:56 AM

You can see the focus shaft inside the control box.  Note how it screws into the backplane of the OTA.  That helps keep the mirror in place.   The replacement shaft on the princess was threaded all the way out to the knob, but the exterior thread did not match the thread of the backplane.   It was pretty much a replacement fail.  The focus shafts changed sometime in the late '60s, and questar does not have the earlier ones on hand.   It will cost you $180 to replace it if they make one for you.  I opted not to.

 

IMG 3684
 
You can also see the pin that fastens the finder knob to the prism assembly.  
IMG 3686
 
You'll need to hold the spring-arm mechanism in place when you pull the control box off.   I used a modified clay-modeling tool. 
IMG 3687


#4 JonTeets

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Posted 17 August 2016 - 11:00 AM

When the control box is off, you may see some metal shavings in the box or against the OTA backplane.   Over the years the metal grinds, and you might create some when you remove the screws.   

 

IMG 3691
 
Also, beware when you remove the control box, there might be a bit of grease on its edges or on the focus knob.   You don't want to get that on your optics.  
IMG 3692
IMG 3693


#5 JonTeets

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Posted 17 August 2016 - 11:07 AM

Here are a few shots comparing the OTA backplane to that of the 1961:

 

IMG 3697
IMG 3699
 
One thing that stands out is the fit and finish of the 1978 model seems higher overall.   The prism assembly is not only in better shape, as expected, its components seem a bit better and better machined.   
IMG 3700
IMG 3701
IMG 3702
IMG 3703
IMG 3704
IMG 3705
IMG 3706
IMG 3707
IMG 3708
IMG 3709


#6 JonTeets

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Posted 17 August 2016 - 11:11 AM

OK, time to remove those C/BB optics.

 

First, unscrew the OTA.  It's easier to remove the corrector plate of the OTA end is resting on a flat surface by itself.   It also reduces the chance of hurting the mirror or something in the backplane.

 

IMG 3711

IMG 3712

IMG_3720.jpg

IMG_3723.jpg



#7 JonTeets

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Posted 17 August 2016 - 11:17 AM

As it turns out, you probably can't just change the optics (corrector+mirror) between a 1961 f/13 model and a 1978 f/14.4 model.   To do the job right and make sure everything aligns properly, it's best to exchange control boxes, too.   This means that only the OTA base rings and the OTAs stay with a scope (and the fork assembly in then 1961's case.)   

 

So remove the flathead screws to remove the plastic OTA fasteners.   These also adjust the tension for turning angle of the control box relative to the fork assembly, btw.  

 

IMG_3730.jpg
IMG_3739.jpg
IMG_3740.jpg
IMG_3742.jpg

Edited by JonTeets, 17 August 2016 - 11:18 AM.


#8 JonTeets

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Posted 17 August 2016 - 11:18 AM

 

Now, begin removing the optical assembly 
IMG_3744.jpg

IMG_3745.jpg

IMG_3746.jpg

 

One thing to note is that in the '78 optics set, the spring is in the focuser shaft instead of on the baffle tube.  

IMG_3747.jpg

 

I had hoped that the Field model's mirror had been fixed in place, but it was not the case.  It could actually rotate.  I'm not sure if this is by design or if it had actually rotated, but this mystery remains.  It has obvious ramifications for calibration.
IMG_3749.jpg

 

There is an arrow pencilled into the edge of the mirror.  Presumably it should be aligned with something.  
IMG_3750.jpg

 

It isn't aligned with the top of the Q.  
IMG_3751.jpg

 

Gently pull the mirror and the outer baffle casing off of the inner baffle.   In order to be able to do this, you will need to screw the focus knob in even further so that its thread completely exits the backplane.   Alternatively, you could slip the focus rod off of mirror assembly arm, but as I was transplanting the focus arm, too, I opted to unscrew it now.   
IMG_3752.jpg

 

There is a serial number on the back of the mirror.   It matches a number on the corrector plate, but it does not match the serial number of the Q itself.  
IMG_3753.jpg

IMG_3754.jpg

IMG_3755.jpg

 

Put the mirror assembly somewhere safe.   I put a lid on this tupperware container and set it aside.  

 

IMG_3756.jpg


Edited by JonTeets, 17 August 2016 - 11:29 AM.


#9 JonTeets

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Posted 17 August 2016 - 11:42 AM

Now, on to the corrector plates.   I'll remove the princess' first.   When I first tried to collimate Ralph, I used cardboard cut in a circle to protect the corrector while I removed the retaining ring.   Some cardboard residue landed on the corrector, making a mess.   I've wrapped the cardboard in a cloth of the kind I use for cleaning my glasses.   I have another one under it for placing the corrector when it's out.  

 

IMG_3763.jpg
IMG_3764.jpg
 
Here's the optical spanning wrench I purchased on eBay  (thanks DAVIDG for the pointer, one among many.)
IMG_3765.jpg
 
Ok, more grease, this time on the backplane side of the OTA's threads.   And it marked my glasses cleaner, which I had to flip.  I also used a lot of paper towels, changing my work surface as I kept finding grease.  
IMG_3766.jpg
 
The damaged corrector.  
IMG_3767.jpg
 
with its (unnecessary?) protector in place.
IMG_3768.jpg
 
The flathead notch in the synthane retaining ring
IMG_3771.jpg
 
Use the flathead side of the spanning wrench for this
IMG_3772.jpg
IMG_3773.jpg
 
It appears the corrector had been damaged when someone tried to pry the retaining ring off with... idonno, a screwdriver?  Gah!  
IMG_3775.jpg
 
If at first you don't succeed...
IMG_3776.jpg

Edited by JonTeets, 17 August 2016 - 11:45 AM.


#10 JonTeets

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Posted 17 August 2016 - 11:47 AM

The synthane retaining ring unscrewed a little bit, but in the end, I had to pull it out rather than screw it out.   The threads were shot.   

 

Again, with the modified clay-modeling tools:

IMG_3778.jpg

IMG_3779.jpg

Edited by JonTeets, 17 August 2016 - 11:48 AM.


#11 JonTeets

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Posted 17 August 2016 - 11:52 AM

And the ring is free.  Note the spacer?   Maybe it's just the remains of tape the mothership used to retain the corrector in place as they tightened the ring, no spacing intended.   There's a notch in the Field model's metal retaining ring, but no tape.

IMG_3783.jpg
 
The new retaining ring is metal and has a small hole for the spanning wrench rather than a flathead.   Kinda makes you wonder how many lenses were scratched over the years before this technological advance was figured out and disseminated.   
 
IMG_3791.jpg


#12 JonTeets

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Posted 17 August 2016 - 11:54 AM

And the corrector plate is out.   

IMG_3795.jpg
 
Note the pencil line in the edge.  Presumably this should be aligned with the arrow in the mirror.   
IMG_3798.jpg

Edited by JonTeets, 17 August 2016 - 11:54 AM.


#13 JonTeets

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Posted 17 August 2016 - 12:07 PM

I took similar steps to remove the Field's corrector plate, but being far more cautious.   Unfortunately, more an hour of trying to work the retaining ring free proved fruitless.  I resorted to liquid wrench.   If you do use it, make sure to create inner and outer dams to protect the corrector plate and the OTA.   The ring came out in short order.   You don't need much.   It still managed to strip some of the baffle's ink.    

 

IMG_3819.jpg


#14 JonTeets

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Posted 17 August 2016 - 12:10 PM

In the end, I had two control boxes, two rings and two backplanes.

 

IMG_3831.jpg
 
Which were exchanged
 
IMG_3832.jpg


#15 JonTeets

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Posted 17 August 2016 - 12:12 PM

I'm looking forward to the clouds clearing so I can compare Princess CBB's (far left) optics to Ralph's (on the far right) standard set.   

 

Family Picture

Edited by JonTeets, 17 August 2016 - 12:19 PM.

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#16 JonTeets

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Posted 17 August 2016 - 12:13 PM

There are more pics of the operation here:

 

IMG 3662
Album: Transplant
124 images
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#17 Paul Schroeder

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Posted 17 August 2016 - 12:54 PM

Thanks for taking the time to share all of this!  It's a really impressive project -

 

Best regards,

 

Paul


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#18 Joe Eiers

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Posted 17 August 2016 - 01:02 PM

Bravo Jon!

You're creating something that will be the ultimate restoration guide for many Questars that are doomed to uselessness.  This needs to be a sticky!  Thanks so very much, I know how much trouble this is to create.

  Joe


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#19 JonTeets

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Posted 17 August 2016 - 09:14 PM

A break in the clouds.  Not much of one, and it's moon-washed and poor seeing, but enough for my purposes.   

 

I took the princess out and let her cool down.   It wasn't much as the outdoors and indoors have held at around 70 for a few hours.   

 

I aimed her at Arcturus, got her in focus to prove it could be done, then I took her out of focus quite a ways.  I centered Arcturus's blob in the FOV.   It was asymmetrical -- one side was squeezed in more than the other.   I began turning the OTA in small increments, then re-centering and adjusting the focus to get the image back to the same size it was.  Turning the OTA moves the corrector plate out on its threads which shrunk the image size.   The image got more asymmetrical at first, then improved until it was as circular as I could get it.  I'll adjust the corrector plate tomorrow so that the OTA can be oriented properly when the scope is collimated.      

 

The image was a bit better, but not great.  Arcturus didn't focus into the nice tight airy disk I'm used to seeing with Ralph.  With seeing being poor,  I'm not sure what fuzziness is the scope and what's the seeing.   I didn't take Ralph out for comparisons yet as it was just a break in the clouds.  It's wet on the deck, which meant no AC clock drive, so I had to fight vibration and recentering a little, too.  I can't wait to get them both out side by side at full strength.     

 

The image was brighter than Ralph's, I could tell that from the star field around Izar.  I was only working with a 16mm Brandon, and seeing's poor so there was no chance of a split, but I was looking for a star I normally need averted vision for with Ralph and I didn't need to work as hard to find it.   

 

Izar cast a ghost, something that never happened with Ralph or the Field, for that matter.  I'm not sure why, but it occurred to me that the mirror and/or the corrector may not be sitting flat.  I didn't take any special steps to ensure they weren't.   I'll have to figure out how.  It's also possible the the OTA is off-center.   There was certainly some wobble in it as I turned it.  It's not as snug screwing in as the Field's is.    Or maybe I screwed up the prism's alignment...   I need to get some kind of bench testing going.  

 

Even with the issues, it was nice to spend some time observing again.   The RA and dec controls are very nice now and I didn't have to think about them at all, they just responded as I'd come to expect with Ralph.  

 



#20 Joe Eiers

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Posted 18 August 2016 - 08:07 AM

Thanks for the report, I'm looking forward to hearing more.  Glad it cleared for ya.

Joe



#21 JonTeets

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Posted 20 August 2016 - 12:27 PM

I took a closer look at the Princess today to see if there was anything obvious causing the fuzziness and ghosting.  

 

There were a few things that needed improvement:

 

1)  Far more of the baffling black ink on the edge of the corrector had been lost than I had noticed the other day.   I added it back with a black sharpie.

 

2)  The corrector plate was ever-so slightly loose, allowing a little bit of wobble.  I doubt this contributed much as the star test eventually showed circles as I rotated the OTA.   I reset it and made sure the retaining ring is holding it in place.

 

3)  A couple of the screws holding the OTA to the fork arms were slightly loose.  I'm not sure if I hadn't tightened them down or if they had worked loose the other night.  They didn't introduce any play that I noticed at the time.   My eye was never at the eyepiece when I was moving the scope with the OTA, though.   Anyway, they are fairly tight now.   

 

4) The OTA does indeed shift a little bit when it isn't screwed in all the way.  I added 3 masking tape layers (just over 1 mm high) along the base of the ring the OTA screws into so that the play goes away when the "N" on the moon map is centered above the eyepiece.  I'll need something more permanent, but this will do for now.    I adjusted the orientation of the corrector plate to account for this so the scope should remain collimated.  

 

I convinced myself that the mirror assembly was not off-axis.  The tangent arm attached to the back of the mirror which the focus shaft attaches to and turns within does not appear to wobble with respect to the mirror.   While the mirror can rotate around the baffle if enough torque is applied, it does not wobble.  The outer baffle is very snug to the mirror and to the inner baffle.   If they weren't I think it would show up as something more dramatic than ghosting at the eyepiece.   The focus shaft is also very snug and moves smoothly.  

 

I have another mount/tripod on the way so should be able to do a shootout against Ralph soon.   It will be good to eliminate  different seeing conditions and worse -- my memory -- as means of muddling the comparisons.   


Edited by JonTeets, 20 August 2016 - 12:30 PM.


#22 DAVIDG

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Posted 21 August 2016 - 08:43 PM

 Your fuzziness is most likely caused because the spacing between the corrector and the primary are different in the '78 vs the '61. In the '61 the secondary spot is located on the front of the corrector and in the '78 on the back. The optical designs are not the same and the  position between the primary and corrector are different. With the incorrect spacing you'll get spherical aberration and the also not the correct baffling of stray light.  

   In the '61 optics with the  spot on the front of the corrector you can also form an image off the back surface of the corrector with the incorrect spacing and I believe that is what your seeing as the ghost.

 

                         - Dave 


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#23 JonTeets

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Posted 23 August 2016 - 07:22 AM

The answer turned out to be rather embarrassing, something I should have noticed earlier.   I had my 1969 out which is now well-calibrated thanks to the new metal retaining ring.   I was getting nice views as seeing was pretty good.  After a while, the fuzziness crept in.  I should be more specific on what I mean by fuzziness.   The background, rather than the usual black, or the slightly sky-washed background of the finder and low magnifications, seemed to have dim dark greyish clouding between the stars.  The stars began to smear a bit, getting small fat spikes, of all things, without jumping around as is the case with bad seeing.   On the moon it took the form of a smearing out of the details.  Again, not like the broiling of bad seeing, and not uniformly defocused like I've seen on a big '80s dob. 

 

Turns out it was dew.  It took some time to develop on Ralph as I had the dew shield extended.   It was likely nearly immediate on the '61 because it doesn't have a dew shield.   This is what I get for my years of observing in Arizona, insensitivity to dew.   I also realized how seldom I touch the OTA.  I usually move the scope to a new target with my hand on the control box while I'm squatted behind the scope sighting across the OTA to line it up.   Then I move to the finder and the control knobs.  

 

You are right that the '61 optical train is a different length than the '78's.   I replaced nearly the entire train because of the difference.   The only parts that remain from the '61 are the ring which the backplane, control box and OTA attach to, and the OTA itself.   I measured carefully -- the distance between the ring and the corrector plate shelf is the same in both scopes.   The length difference is entirely accounted for by where the baffle, spring and focus shaft allow the mirror to range.  As that stayed with the optics set, after the transplant all the optical components of the '78 are in the positions they were before the transplant, just attached to a different OTA and ring.   I hope that makes sense.  

 

I have a flat, Ronchi screen and a few other components from the Dick Parker Stellephane video on auto-collimation on the way.  I'll follow the Dynamax thread (and others) to test the Qs as a system.   


Edited by JonTeets, 23 August 2016 - 08:28 AM.


#24 DAVIDG

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Posted 23 August 2016 - 08:13 AM

 When you test your Q by double pass be sure to test it in green light by either using a green LED or look through a green filter. The reason is that these Mak design especially the older version with the spot on the front of the corrector do have chromatic aberration. As the label states it is APO like corrected.  So you'll  see a bit of color in white light and it softens the Ronchi lines. When you test in green light were the optics were designed to have the best correction you should get nice straight and sharp Ronchi lines. 

 

                    - Dave 


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#25 JonTeets

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Posted 29 August 2016 - 10:34 PM

The ghosting is gone.  It didn't come back after ZBB got a little dew on her, so I think that's probably down to the baffling.  

 

Most of the fuzziness is gone, but not all of it.  The stars are back to looking like Q airy disks, and the cloudiness is mostly gone, but still perceptible.   It could still be dew.  We've had it every night.   I think I kept it at bay one night, but I can't fully rule it out yet as the cause.   

 

The only good seeing night we've had I had Ralph out, so I still haven't been able to get a good image at any higher magnification than that provided by the 16mm EP.   The forecast is good for late this week, so I'm looking forward to doing a side-by-side, finally.   There's also a star party, so maybe I'll have some help.    

 

I'm still waiting on some of the parts for testing.  I got some to build an interferometer, too.  


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