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Pal Jr. Restoration

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#1 deSitter

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Posted 01 December 2021 - 01:32 AM

Howdy all!

 

My friend likes to go estate sale-ing and flea-marketing, and I told her always to be on the lookout for scopes and other optics. Well she found this TOTALLY beat up Pal Jr - it was a disaster - god knows how many years of dust on the primary - but strange to say, this probably preserved the coating on the mirror, which has the original sticker on the back. I completely tore it down and refurbished everything. The finder eyepiece has some melted cement from the Sun, but it still works. This is I think a very early copy of this scope. I don't remember seeing one with the clock drive and the eyepiece tray. The drive works perfectly and the leather clutch pad is still in great shape. The only thing that had to be replaced was the diagonal - a silvered prism that was in horrible condition. We ordered a new secondary. The scope has OK optics, I expected a little better from a 4.25" f/10 sphere. But it's her first scope and she loves it!

 

-drl

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Edited by mdowns, 01 December 2021 - 07:22 AM.

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#2 deSitter

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Posted 01 December 2021 - 01:33 AM

,,more

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#3 deSitter

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Posted 01 December 2021 - 01:36 AM

I didn't get any before shots - but it looked like the scope had been in a hailstorm. Someone had scratched their name (JAN) in the tube paint. The screws were all totally rusted. There was 50 or so years of dust on it. But the aluminum tube was in perfect shape. I had to move the mirror forward an inch or so to get focus with modern Plossls. It was great fun to get reacquainted with an old school scope. But it really made me appreciate my modern mounts!

 

-drl

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#4 deSitter

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Posted 01 December 2021 - 01:41 AM

BTW I can't say enough good things about Rustoleum 2x primer. The paint job on the mount and tube came out looking like the scope is brand new.

 

-drl


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#5 deSitter

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Posted 01 December 2021 - 01:47 AM

Any Pal experts? I'd like to know about the variations. Notice this one has the symmetrical pedestal cap - later versions had an offset pivot hole - probably to clear the clock drive - you can see what a tight fit it is here. I was amazed to see that the old drive worked so perfectly! And it was very easy to adjust so that almost no backlash was left. Also notice there is no toe-saver stop to the counterweight - it has to be this far down to balance the scope. If you invert the DEC axis to put the scope closer to the RA axis, the scope doesn't clear the clock drive in all positions, no matter how you rotate it.

 

-drl


Edited by deSitter, 01 December 2021 - 01:50 AM.

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#6 apfever

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Posted 01 December 2021 - 08:41 AM

Can you rotate the drive assembly for more clearance on both the pier and OTA?

 

The DEC housing came in a variety of different lengths and configurations. It seems Edmund had constant modifications as they added a motor or changed the pier cap, and then found the DEC housing needed to be changed for clearance. I honestly think Edmund sent out some one off configurations that did work but were a bit tight for clearance, and then did a modification for the next round.  Here is a link that shows some of the mount housing variations in the RA, and I've seen a few in the DEC as well. I also like the Rustolium 2X and have for years...it's in there.

 

Mount Link

 

You can reverse the DEC housing and add in a custom spacer. It shouldn't be hard to find a nice looking piece of pipe with a friendly smooth inner bore (or smooth one out). This will increase the amount of shaft available for the counterweight. At the same time it will extend the housing support of that funky skinny shaft. No toe guard, drill and tap your own. 

 

Nice job on the scope. If she's happy then awesome. I'm envious of the tray, I never found one. The motor will have a date if it is a Synchron, no date if it is a Haydon.  That is an early scope either way. 


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#7 deSitter

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Posted 01 December 2021 - 09:52 AM

Can you rotate the drive assembly for more clearance on both the pier and OTA?

 

The DEC housing came in a variety of different lengths and configurations. It seems Edmund had constant modifications as they added a motor or changed the pier cap, and then found the DEC housing needed to be changed for clearance. I honestly think Edmund sent out some one off configurations that did work but were a bit tight for clearance, and then did a modification for the next round.  Here is a link that shows some of the mount housing variations in the RA, and I've seen a few in the DEC as well. I also like the Rustolium 2X and have for years...it's in there.

 

Mount Link

 

You can reverse the DEC housing and add in a custom spacer. It shouldn't be hard to find a nice looking piece of pipe with a friendly smooth inner bore (or smooth one out). This will increase the amount of shaft available for the counterweight. At the same time it will extend the housing support of that funky skinny shaft. No toe guard, drill and tap your own. 

 

Nice job on the scope. If she's happy then awesome. I'm envious of the tray, I never found one. The motor will have a date if it is a Synchron, no date if it is a Haydon.  That is an early scope either way. 

Nice! I was going to polish the brass bushings but 1) I was too lazy and 2) I sort of like the old patina, and I'd have to do the spur gear too and didn't want to mess with all that! Good work!

 

-drl


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#8 deSitter

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Posted 01 December 2021 - 09:57 AM

Can you rotate the drive assembly for more clearance on both the pier and OTA?

 

The DEC housing came in a variety of different lengths and configurations. It seems Edmund had constant modifications as they added a motor or changed the pier cap, and then found the DEC housing needed to be changed for clearance. I honestly think Edmund sent out some one off configurations that did work but were a bit tight for clearance, and then did a modification for the next round.  Here is a link that shows some of the mount housing variations in the RA, and I've seen a few in the DEC as well. I also like the Rustolium 2X and have for years...it's in there.

 

Mount Link

 

You can reverse the DEC housing and add in a custom spacer. It shouldn't be hard to find a nice looking piece of pipe with a friendly smooth inner bore (or smooth one out). This will increase the amount of shaft available for the counterweight. At the same time it will extend the housing support of that funky skinny shaft. No toe guard, drill and tap your own. 

 

Nice job on the scope. If she's happy then awesome. I'm envious of the tray, I never found one. The motor will have a date if it is a Synchron, no date if it is a Haydon.  That is an early scope either way. 

Does the single-stalk finder bracket tell anything about the date? Next time I'm up there I'll check the motor. Surprised I didn't do that already. Also - the finder was black. I preferred white for the body.

 

-drl


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#9 PawPaw

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Posted 01 December 2021 - 10:03 AM

Does the single-stalk finder bracket tell anything about the date? Next time I'm up there I'll check the motor. Surprised I didn't do that already. Also - the finder was black. I preferred white for the body.

 

-drl

Wonderful find......and I agree on leaving some patina.   Two things stand out for me dating this as an early mode.  The single finder bracket and the fact the OTA bolts onto the saddle.   Also the black finders predate the white ones.  My Pal Jr. also has bolts permanently mounted in the OTA but mine has two finder brackets and the white finder.   As Apfever stated the circular tray on the mount is a rarity.  I have seen one over my years.

 

Cheers

 

Don


Edited by PawPaw, 01 December 2021 - 10:05 AM.

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#10 steve t

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Posted 01 December 2021 - 11:13 AM

Great find and restoration. 



#11 clamchip

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Posted 01 December 2021 - 11:26 AM

Looks great! I love seeing a Pal Jr all restored like you did.

They seem to be well used when found, a good sign!

I'm surprised its not better than just OK.

White tube and a single stalk finder mount puts it around the

end of the 50's very early 60's, the motor cover may have a 

date except I don't recognize that motor.

Robert

 

post-50896-0-11105800-1432935439_thumb.jpg



#12 DAVIDG

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Posted 01 December 2021 - 12:12 PM

 Very nice job !  I really enjoy mine and it  is one of my favorite scopes.  A 4.25" f/10 spherical mirror with an optically flat diagonal falls into  the "sweet spot" of optics with a wavefront of a true 1/8 wave. The issue I have found on testing at least 20 of the rectangular diagonals  is they are nowhere near optically  flat. Most test at 1/2 wave or worse. Even many of  the modern replacement test poorly as well.  It took me awhile before I found a good one for my Palomar Jr. The original diagonals that were made from a WWII binocular prism that were sawed  in half then the hypotenuse coated maybe very good optically thou. In a prism  the hypotenuse needs to be very flat since the light is  bent by total internal reflection in a high index material ( the glass) so the tolerances in flatness are much greater.  

   The other interesting issue I found is that the mount is light enough that the vibration from the clock drive shake the images at high power  I don't see it when the scope is setup on my driveway but if I set it on grass it shows up at high power.  It is interesting to watch as I turn the clock drive on and off while observing Jupiter or Saturn at high power. The planetary image goes from razor sharp to slightly fuzzy and I have repeated it many times over many days. It is like putting your reading glasses on and  off.  If you didn't start out by having the drive off and observing at high power then turning it on you would never notice it or just think the seeing was a little soft that night. I have two complete clock drives and it  does it with both so it is not a bad motor.  I'm going to fill the pier with some sand to see if that will add enough weight to damp the vibrations.  

 

                  - Dave 

 

4.25 palomar jr.jpg


Edited by DAVIDG, 01 December 2021 - 03:27 PM.

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#13 PawPaw

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Posted 02 December 2021 - 08:27 AM

The other interesting issue I found is that the mount is light enough that the vibration from the clock drive shake the images at high power  I don't see it when the scope is setup on my driveway but if I set it on grass it shows up at high power.  It is interesting to watch as I turn the clock drive on and off while observing Jupiter or Saturn at high power. The planetary image goes from razor sharp to slightly fuzzy and I have repeated it many times over many days. It is like putting your reading glasses on and  off.  If you didn't start out by having the drive off and observing at high power then turning it on you would never notice it or just think the seeing was a little soft that night. I have two complete clock drives and it  does it with both so it is not a bad motor.  I'm going to fill the pier with some sand to see if that will add enough weight to damp the vibrations.

 

My original "medium duty" mount that came with my Pal jr does not have a clock drive which is why I usually mount mine on the "heavy duty" version with tripod legs and motor.  Luckily Edmund designed their saddles to match the bolts on their early OTA's.  I can tell even without the motor drive their is a big difference on how quickly the tremors settle between the two mounts.   I must have been lucky on the original diagonal that came with mine as DPAC tests show it to be an excellent flat.  

 

Don

 

 

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