Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Restoring a '59 Cave 10" f/7.1

  • Please log in to reply
70 replies to this topic

#51 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted 09 December 2018 - 03:37 PM

Consider Rustoleum self-etching primer before you paint with your chosen finish coat.  Cave usually did not primer and his paint peels off.  

 

Think hard before you remove the large "altitude bolt" if the polar axis angle matches you latitude.   If the angle is correct no need to remove it.   You can paint with it in place.

 

Secondary holder is a "backplate"  as you call it and a shroud.  There should be 3 small screws at 120 degrees at the base of the shroud which screw into the backplate.  Your pic shows one of the screw holes.  Remove screws and then pull the backplate away from the shroud.  It may be stuck from age but it should yield.

Thanks, Kent. Yes, I figured those adjusted the tension on the inner ring, and I loosened them to see if I could get it to rotate any easier. I will certainly take your advice and not remove the inner ring. I will use the primer before going any further, thank you. The altitude bolt looks pretty rusty, but it looks fairly close to my latitude. I'm thinking it will be a bit off because of where the person lived, so I may have to adjust it. I was originally thinking from some of the other threads that I would need to completely disassemble everything, but I think not. 


  • Mr Magoo likes this

#52 Mr Magoo

Mr Magoo

    Mercury-Atlas

  • *****
  • Posts: 2598
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 09 December 2018 - 04:03 PM

Thank you, Jon and Kent. Yes, I had taken the small 120 degree screws out but it's not budging a bit. I'll work more on it now that I know what the inner ring looks like and how far it goes into the shroud. 

The secondary holder on my Meade RG had this problem. The shroud had "welded" itself to the plate with corrosion. I tried heat, cold, and solvent trying to remove it. In the end I had to destroy that plate carefully to remove it. The plate was made out of the poor alloy Meade used and it just crumbled into pieces when I went at it. 



#53 Geo31

Geo31

    Voyager 1

  • *****
  • Posts: 10275
  • Joined: 28 Jan 2013
  • Loc: Willis, TX

Posted 10 December 2018 - 12:19 AM

Apfever's post confused me on this. Looked it up and that is what I found that the gel coat is applied to the fiberglass. So it either has a gel coat or something else. What is the other finish? I saw a how it is made show where they build a fiberglass boat and the gel coat was sprayed in the mold first. 

I’m not sure the question.  Gel coating can be applied either way.  If a part is made in a mold, you apply the gel coat to the mold and then the resin/mat (or prepreg) to the mold.


  • Mr Magoo likes this

#54 Mr Magoo

Mr Magoo

    Mercury-Atlas

  • *****
  • Posts: 2598
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 10 December 2018 - 05:48 AM

Thanks, Kent. Yes, I figured those adjusted the tension on the inner ring, and I loosened them to see if I could get it to rotate any easier. I will certainly take your advice and not remove the inner ring. I will use the primer before going any further, thank you. The altitude bolt looks pretty rusty, but it looks fairly close to my latitude. I'm thinking it will be a bit off because of where the person lived, so I may have to adjust it. I was originally thinking from some of the other threads that I would need to completely disassemble everything, but I think not. 

The rotating  rings are also meant to be run dry with no lubricant. The one I have was stuck with old grease. Grease will just attract dirt. I polished and waxed the race on my other scope before putting it back together. It turns very nicely with the new PTFE plugs.You need to adjust the set screws so that the tube is concentric with the inner piece for it to turn smoothly also. 


  • steve t and TOM KIEHL like this

#55 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted 10 December 2018 - 10:42 PM

The rotating  rings are also meant to be run dry with no lubricant. The one I have was stuck with old grease. Grease will just attract dirt. I polished and waxed the race on my other scope before putting it back together. It turns very nicely with the new PTFE plugs.You need to adjust the set screws so that the tube is concentric with the inner piece for it to turn smoothly also. 

I got the chance to work on the rings today and got them off. All the tips proved quite helpful. The track is free of grease but could use some cleaning. Where does one get new PTFE plugs? I see now that tightening the nuts pulls the pressure down onto the PTFE (what does that stand for?), thereby increasing tension. Instead of nuts, wouldn't knobs work better?

 

I also tried using the boat cleaner recommended earlier and it cleaned and shined the fiberglass (can you see the spot? lol), but none of the yellowing disappeared. I'm going to look up the 3M, but the tube is so yellow I'm not sure it will clean. It's hard to get a good color shot, as it tends to photograph whiter than it is.

 

Guy

Attached Thumbnails

  • 20181210_153313.jpg
  • 20181210_154325.jpg

Edited by Guy Earle, 10 December 2018 - 10:43 PM.

  • steve t and Bomber Bob like this

#56 Mr Magoo

Mr Magoo

    Mercury-Atlas

  • *****
  • Posts: 2598
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 10 December 2018 - 11:46 PM

I got the chance to work on the rings today and got them off. All the tips proved quite helpful. The track is free of grease but could use some cleaning. Where does one get new PTFE plugs? I see now that tightening the nuts pulls the pressure down onto the PTFE (what does that stand for?), thereby increasing tension. Instead of nuts, wouldn't knobs work better?

 

I also tried using the boat cleaner recommended earlier and it cleaned and shined the fiberglass (can you see the spot? lol), but none of the yellowing disappeared. I'm going to look up the 3M, but the tube is so yellow I'm not sure it will clean. It's hard to get a good color shot, as it tends to photograph whiter than it is.

 

Guy

PTFE (Polytetrafluoroethylene) is Teflon. You can order virgin teflon rod from McMaster-Carr. https://www.mcmaster.com/ptfe-rods A 12" stick is more than enough.

 

On my RG the 5/16" rod was tough to get in the 3/8" threaded holes. You really don't want it tight in the holes or else it will not release freely for adjustment. I think on my Cave I'm doing now I will try 1/4". I used a flat tip set screw when I put it back together so as not to deform the end of the rod making it hard to move freely. 

 

The set screws put pressure on the rod and the nuts just lock them into place. The set screws seem to be fine. Once you get them set right. They won't need adjusting for a long time. It's not like it is doing a lot of spinning round and round. 


  • Guy Earle, steve t and Geo31 like this

#57 apfever

apfever

    Aurora

  • *****
  • Posts: 4662
  • Joined: 13 May 2008
  • Loc: Colorado

Posted 11 December 2018 - 02:45 AM

Did you try soap and water on the OTA?  


  • Guy Earle likes this

#58 PiSigma

PiSigma

    Vanguard

  • *****
  • Posts: 2439
  • Joined: 14 Oct 2009
  • Loc: North Carolina

Posted 11 December 2018 - 09:48 AM

The McMaster-Carr part number you need is 8546K35, 5/16" PTFE rod. This same rod can also be threaded to 5/16"-24 for the mirror centering screws in the cell.

Attached Thumbnails

  • IMG_5085sm.jpg

Edited by PiSigma, 11 December 2018 - 09:48 AM.

  • Mr Magoo, steve t, KentTolley and 4 others like this

#59 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted 11 December 2018 - 10:22 PM

Did you try soap and water on the OTA?  

I feel awkward admitting that I have not. But I only tested a small spot with the marine cleaner wax. I'll be trying the soap and water and the 3M product in the coming week.


  • Mr Magoo likes this

#60 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted 11 December 2018 - 10:26 PM

The McMaster-Carr part number you need is 8546K35, 5/16" PTFE rod. This same rod can also be threaded to 5/16"-24 for the mirror centering screws in the cell.

I'm seriously impressed with the knowledge you all have over what size screws and bolts the scope takes. And after all these years I never heard Teflon called PTFE before, proving there's always something to learn. I've had 1/4" sheets of it for years, using it for side bearings and ground boards. I've never used them in this application before. When the first one fell out I wondered what it even was, and guessed it was hardened plastic because of the transparent appearance, not even remotely looking like the Teflon I use.



#61 Mr Magoo

Mr Magoo

    Mercury-Atlas

  • *****
  • Posts: 2598
  • Joined: 05 Nov 2005
  • Loc: Indiana

Posted 11 December 2018 - 10:35 PM

The McMaster-Carr part number you need is 8546K35, 5/16" PTFE rod. This same rod can also be threaded to 5/16"-24 for the mirror centering screws in the cell.

That is the one I ordered, but for some reason it would not fit in the threaded holes without me using a mallet. 



#62 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted 11 December 2018 - 10:35 PM

The secondary holder on my Meade RG had this problem. The shroud had "welded" itself to the plate with corrosion. I tried heat, cold, and solvent trying to remove it. In the end I had to destroy that plate carefully to remove it. The plate was made out of the poor alloy Meade used and it just crumbled into pieces when I went at it. 

I got home late today but I did manage to get the secondary mirror out. I bought a can of Blaster (my god that stuff stinks), and a few careful light sprays and I was able to remove the back plate of the shroud. Curiously, the secondary has a strange shape and even a signature that I can't quite make out. It's definitely 1.83" as I have another from my old 12.5" f/6 years ago.

 

Also, I contacted Majestic about coatings, and their price was very reasonable. However, they only offered 91-92% visual aluminizing. I've always had enhanced in the 96-97%, and don't want to use less than my old mirror from Nova/QSP. So I am going to use Spectrum Coatings mainly because our St. Pete Astronomy Club has had a mirror lab for a long time, and has worked with them for years with great success. This Saturday the lab will help remove the old coatings for both the primary and secondary and test the mirror, so I'm very, very curious to find out some details. 

 

Guy

Attached Thumbnails

  • 20181211_220610.jpg
  • 20181211_220615.jpg
  • 20181211_220558.jpg

  • Mr Magoo, steve t and Augustus like this

#63 Compressorguy

Compressorguy

    Vanguard

  • *****
  • Posts: 2034
  • Joined: 14 Mar 2009
  • Loc: Clayton, NC

Posted 12 December 2018 - 02:46 AM

Very nice scope by the way and enjoying your post on it. Can’t wait to see it completed. I believe the mirror inscription reads “1/20 wave” referring to its optical quality—surface figure and flatness.


Edited by Compressorguy, 12 December 2018 - 02:54 AM.


#64 KentTolley

KentTolley

    Messenger

  • *****
  • Posts: 400
  • Joined: 26 Mar 2012
  • Loc: Southern California

Posted 12 December 2018 - 11:00 AM

On the tube, can you sratch off that big black smudge with your fingernail?

I have a secondary with that cut-off on the back.  It is to allow attachment to a single stalk holder.  

Attached Thumbnails

  • rsz_20181212_081006.jpg

Edited by KentTolley, 12 December 2018 - 11:15 AM.

  • Guy Earle likes this

#65 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted 12 December 2018 - 01:17 PM

On the tube, can you sratch off that big black smudge with your fingernail?

I have a secondary with that cut-off on the back.  It is to allow attachment to a single stalk holder.  

Kent,

 

I'm going to try and clean it later today if I get caught up with work. If. That makes total sense about the stalk, but I could never use a single-vane. I'd be so nervous of it falling down on the primary.

 

Guy



#66 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted 15 December 2018 - 12:00 AM

Okay, just a quick update post regarding the OTA: I got the 3M restorer and shocked.gif bow.gif waytogo.gif

 

I cleaned the whole OTA with soap and water first, then used the mid-grade marine cleaner and wax I had previously purchased on the lower section to test the results. I was shocked how much nicer the tube looked already, then I decided to try the 3M about an hour ago (thank you Amazon Prime). The small test spot quickly turned into the whole section between the rings and the worst portion near the focuser. Stuff that did not come clean with the cleaner/wax came right off with the 3M restorer! There are some cuts into the OTA here and there, but by-and-large 98% of the dirt and streaks are coming off. And the OTA is a shade lighter, so I will go back over it once I finish the whole tube. It's almost as if the tube has a very even, soft cream color to it, and I'm wondering if that truly is age or by design. There's a bit of different shading where the connecting bars were between the rings, but overall the color is very even. It's late, but I'll post pics this weekend.

 

Also, I soldered a new power cable and with the flick of the old rocker switch the bulb lit and the motor started buzzing. I let it go for 20 minutes and compared, and she's definitely working!

 

Tomorrow I am going to the SPAC mirror lab to strip and test the mirrors, hopefully polish some more of the OTA later in the day, and post some pics.

 

Thanks again for all the input from everyone here.

 

Guy


  • Mr Magoo, sgorton99, steve t and 1 other like this

#67 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted 15 December 2018 - 10:21 PM

Update pics:

 

Today we stripped the primary and secondary and the SPAC mirror lab tested it out. I knew a fair bit about the mirrors 20 years ago, but have forgotten the details. They did say that it was extremely smooth and was a very good mirror, probably 1/6th wave (I know there are multiple wave formats, but as I understood the mirror performed quite well). I've attached photos so you all can see n the next post.

 

The RA motor hummed to life after I soldered the new power cord. I grinned when I flipped the toggle switch and the little light went on. I took reference pics 20 minutes apart and the worm gear (as well as the other two) had changed positions. Can this scope be moved without damage to the motor, or do I need to shut it off (I've owned and built dobs for 20 years, so sorry if that sounds like an entry level question)?

 

And lastly, I can't say enough about the 3M fiberglass restorer. Just check out the before and after pics for the proof. 

 

Cheers,

 

Guy

Attached Thumbnails

  • Screenshot_20181215-105219_Gallery1.jpg
  • 20181215_1012381.jpg
  • 20181215_1233241.jpg
  • 20181215_1302061.jpg
  • 20181214_1721131.jpg

Edited by Guy Earle, 15 December 2018 - 10:23 PM.

  • sgorton99, steve t, TOM KIEHL and 2 others like this

#68 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted 15 December 2018 - 10:22 PM

Here are the screenshots during the testing:

 

 

Attached Thumbnails

  • 20181215_1255371.jpg
  • 20181215_1257101.jpg
  • 20181215_1319221.jpg

  • steve t, TOM KIEHL and Bomber Bob like this

#69 TOM KIEHL

TOM KIEHL

    Aurora

  • *****
  • Posts: 4826
  • Joined: 17 Nov 2012

Posted 15 December 2018 - 10:47 PM

Okay, just a quick update post regarding the OTA: I got the 3M restorer and shocked.gif bow.gif waytogo.gif

 

I cleaned the whole OTA with soap and water first, then used the mid-grade marine cleaner and wax I had previously purchased on the lower section to test the results. I was shocked how much nicer the tube looked already, then I decided to try the 3M about an hour ago (thank you Amazon Prime). The small test spot quickly turned into the whole section between the rings and the worst portion near the focuser. Stuff that did not come clean with the cleaner/wax came right off with the 3M restorer! There are some cuts into the OTA here and there, but by-and-large 98% of the dirt and streaks are coming off. And the OTA is a shade lighter, so I will go back over it once I finish the whole tube. It's almost as if the tube has a very even, soft cream color to it, and I'm wondering if that truly is age or by design. There's a bit of different shading where the connecting bars were between the rings, but overall the color is very even. It's late, but I'll post pics this weekend.

 

 

Thanks again for all the input from everyone here.

 

Guy

Very nice job on the tube , Guy ! looks great ! Lots O Work there , if done by hand ..waytogo.gif waytogo.gif



#70 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted Yesterday, 07:40 AM

Hey, Tom. Thanks, yes, all by hand. I tried using a car polisher but that was scrapped immediately and instead just cuts of cloth and elbow grease. I'm really shocked how well it is cleaning up. Fiberglass tubes are great, way lighter and smoother than any sonotube I've worked on.

Guy

Edited by Guy Earle, Yesterday, 04:05 PM.

  • Mr Magoo, steve t, TOM KIEHL and 1 other like this

#71 Guy Earle

Guy Earle

    Sputnik

  • -----
  • topic starter
  • Posts: 26
  • Joined: 19 Jun 2006

Posted Today, 02:10 PM

So do you all have a recommendation for a replacement focuser? I've looked at the Scopestuff, which is very nice (I have a Moonlite on my 16"), but I'm thinking since the old is a tall, rack-and-pinion, I probably need to keep the same unless I use an extension tube (I'm not drilling new holes to move the primary).

 

OPT has one, but it looks way cheap on design. I should have picked up an old Edmund Scientifiic I saw on the Classifieds, but I'd like to put a 2" focuser instead. 

 

Thoughts?

 

Cheers,

 

Guy




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics