Jump to content


Photo

Restoring and Repainting Classic Telescopes

  • Please log in to reply
147 replies to this topic

#1 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 07:47 AM

One of the hardest things to do when restoring a classic telescope is selecting a color to repaint the tube and trim. Essentially two routes can be taken - you can mimic the original colors as much as possible, or you can go in a completely different color(s) making the scope more an expression of your own personal tastes.

Repainting in an original color is harder than you may think. There are just about a zillion shades of white out there, and matching white is further complicated by how white ages over time. The white on your telescope tube today may not be the white it was when it was new 10 to 15 years ago. Some years ago when I was trying to match the "Unitron White" of my #152 4" Unitron for a photo-guide scope rebuilt, I came as close as I could, but still could not get it quite right. Same thing with the repaint of a Takahashi finder scope. It seems like I spent hours at "Auto Zone" going thru all the import whites trying to find something close. I wound up bringing about 4 or 5 cans of different whites home to see what was best. As it turns out I finally found a very close match in the form of Plasti Kote FM 8141. I never did find what I consider a good match for Unitron White. With a complete rebuild of a 3" Unitron I went with Krylon "Ivory", a color I like much better anyway.

Often I like to go in a completely different direction. The disadvantage of doing that is it will hurt the resale value of a scope, particularly something like a Unitron or a Takahashi. Keep in mind however that your "replacement" paint job has to match so well and look so close to the original that if it is not mentioned, it has to completely fool someone into thinking that it is original. I don't recommend deceiving anyone in this way, you have to mention a rebuild or a repaint if that was done. For some purists, a repaint, no matter how good, detracts from the value of a classic scope like a Unitron.

I do think that going in a different direction with a totally different color can be lots of fun if you know the telescope you are repainting is a keeper or if it was bought cheap, strictly as a fixer-upper. In fact I would thoroughly recommend that everyone buy a cheap garage sale telescope or a less than perfect scope from eBay or AstroMart with the intention of fixing it up. Doing this will help you develop some rebuilding skills, primarily tube repair and painting skills. A good looking telescope that has some of your personal effort in it, that draws lots of compliments will give you plenty of personal satisfaction. Restoring telescopes is a hobby unto itself.

Anyway with a current project, rebuild of a Milo 3" f/18.4 refractor, I have been trying to find the equivalent of what I will call "Vespa" Blue-Green to replace the white that originally was the color of this tube. I think I have found a color that I like. See the attached Dupli-Color color chart. There is a color called "Malibu Mist" which comes close to what my "Mind's Eye" envisions as a good color for my rebuild project. Let me know what you think.

http://www.duplicolo...rs/premium.html

I am going for kind of a different retro look and I think this color will do that. I also think it will contrast nicely with the semi-gloss black focuser and objective cell.

The attached photo shows a repainted guidescope used with a Takahashi FCT 76. The guidescope was repainted with the previously mentioned Plasti Kote FM 8141. Not a bad color match in my opinion, but still not a perfect match.

Barry Simon

Attached Files



#2 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 08:17 AM

Here is another picture. It is my Unitron-Edmund. (Scope is a shortened Unitron tube with an Edmund 3" f/11 objective (836 mm f.l.). This tube assembly as well as finder and guidescope were painted using Krylon Ivory.

Barry Simon

Attached Files



#3 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 08:29 AM

Here is still another rebuild. Some may find the Dupli-Color "Metal Cast" Purple Anodized as decidedly non classic for a telescope, however this color really comes into it's own in direct sunlight. The scope, a Celestron Super Polaris C102 is my public star party scope. I call it the "Purple Planet Eater" and it is complete with green laser and "Marvin the Martian". Kids really like it.

Before the rebuild this scope was a beat up gloss black with several tube dents.

Barry Simon

Attached Files



#4 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 08:57 AM

Before painting can begin, the first step in tube repair is fixing major dents. The Milo refractor that I am working on now had major tube dents. Actually these were crush marks caused by the tube not being properly seated in the wood cradle in the wooden box. Looks like the lid was force closed or something fell on it. This fractured the 1/2" thick box top and crushed the tube. These dents were so bad that collimation of the scope was thrown off. I was able to buy the scope used, apparently because the previous owner, who bought it used, didn't have the time or ability to repair it.

While I had dealt with small tube nicks in the past, and had filled in drill holes; I wasn't sure just how to deal with this tube. Replacing it would be next to impossible, and I could not just simply fill in these major depressions in the tube as while that might be cosmetically ok, it did not address the fact that the tube damage had affected optical collimation. I contacted one of those auto body places that do body repair for things like hail damage. I was told that their process would not work on aluminum. Another possibility would be to fabricate a mandrill that had the same o.d. as the tube i.d. and to then force it thru the tube pushing the dents out in the process. This would require that the 2 glare stops be removed from the tube and then replaced exactly where they were. The danger also existed that the mandrill would get stuck in the tube and forcing it out would further damage the tube.

The best solution turned out to be use of a tail pipe expander. This is a device that is used to expand bent tail pipes. It basically works like a big molly bolt that is used to support weight on walls where pictures need to be hung where there is no backing stud to support the weight. Two opposing nuts which come together on a threaded shaft push up metal plates which are held in place with big o-rings. The tail pipe expander is closed at a diameter of about 2 inches or so and fully open at about 3.5 inches or so. This would be perfect for the Milo telescope tube. As the two areas with crush marks were on both ends of the tube were between the tube ends and the glare stops, they were accessible.

See the posted photo of the tail pipe expander.

Barry Simon

Attached Files



#5 Preston Smith

Preston Smith

    The Travel Scope Guy

  • *****
  • Posts: 6051
  • Joined: 24 Apr 2005
  • Loc: Eureka, Pa

Posted 31 March 2008 - 09:01 AM

Very Good Thread Barry!

And timely....

I have been toying with the idea of painting one of my early Tasco's a different color. I have a nearby powder coater who has very reasonable prices (and some exotic color options).

Your purple scope is fantastic. Now I'm REALLY starting to think out of the box.... :question: ;) :grin:

#6 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 09:09 AM

So with the tail pipe expander, the tube dents were removed for the most part. The exterior of the tube was not perfect, but the collimation was much improved as shown in this image.

Barry Simon

Attached Files



#7 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 10:09 AM

While additional collimation tweaking could not be done thru further tube repair, the stellar image now looks ok and I believe I can tweak collimation a bit more thru remounting of the focuser.

The next step in the repair process is cosmetic repair of the tube prior to repainting. To do it right necessitates complete stripping of the tube externally. This can be done for the most part with a good paint remover such as Strypeeze. It may have to be applied several times. A single edge razor plate can be used to scrape off soft paint and once as much paint as possible is removed, any remaining paint can be sanded off. Follow instructions on the can of paint remover and do not do this inside. Try to avoid getting the stuff under your fingernails. If it gets on your skin it will begin to irritate after a half dozen seconds or so. Clean it off as soon as possible, but you will not "melt". Avoid the fumes and keep it away from pets. Don't do anything to really tick off the "significant other".

Once you have a bare tube, the next step is external tube repair if needed. I love to use a product called JP Weld. It is kind of an epoxy type liquid steel. When the resin and hardener are mixed, the white and black colors of the separate components mix to form a battleship gray paste which will cure completely in about 24 hours. For small little nicks and scratches in a tube surface, put just a little bit on the nick or scratch and then spread out, over and into the scratch or nick with a single edge blade pulled across the surface. A small repair like this will be virtually completely dry in under 6 hours and can then be sanded level with the surface of the tube. Remember that the less "extra" you put on the tube, the less "extra" you will have to sand off.

For larger dents, the process is basically the same, you just have to use more and it takes longer to cure. With larger repairs, you want to keep the JB Weld from running. Do that by keeping the area you are repairing level, so the product cannot easily run out of the repair. There may be a tendency to see small bubbles in the JB Weld when you are using more of it; pop these with a straight pin. The JB Weld will seek it's own level, filling in any holes. After the stuff is cured and sanded the next day, sanding may reveal a small hole as you sand down a bubble that has not popped; fill this in with a little more JB Weld until the repair meets your expectations. This stuff is strong and hard, it has been used to repair cracked transmission cases. It sands very well and it takes paint very well.

After the tube has been cosmetically prettied up, you should prime first using a good primer recommended for use with whatever paint you want to use. I would first sand the tube with about a 200 grit paper before priming. For painting a tube I will typically run a broom handle or rug pole thru the tube, suspending the pole in the center of the tube by packing balled up newspaper around it. The pole is suspended between two garbage cans or anything else that may work that will allow me to turn the tube with the pole after several passes of the spray paint. >>>>>>>>Spray - right to left, and immediately back over the same area going left to right, turn the tube slightly and repeat, overlapping slightly with each turn. Follow recommendations for the right distance. Keep the spray can agitated to avoid spitting paint. The paint may spit when the can is close to empty. Follow temperature recommendations for painting. Avoid windy days. Go for a glossy wet look, but avoid overpainting and creating runs. Only experience and mistakes will help you here. When it looks right, turn the tube to see if there are any areas where you perceive the primer shining thru, if so, spray those areas one last time. Stay with the tube about 10 minutes turning the pole, this will help you avoid runs. (Also avoid days when there is a lot of airborne stuff flying around, pollen, dust, etc. If your next door neighbor is cutting his yard, don't paint.)

The paint has to cure, and you want this to happen in a dust free safe place. I once left a tube suspended on it's pole between two lawn chairs. I went inside and while looking outside saw a crow land on the freshly painted tube. He felt it made a good perch. This ruined the paint job, I had to start all over again!

Find a place to suspend the tube in your "Man Cave" or hobby area. No sense in ticking off the wife, or having her try to move something and messing up the paint job or getting wet paint on her clothing.

To be safely handled by hand, paint takes awhile to completely cure. A lacquer (most automotive colors) can be safely handled and used in 24 hours or less. An enamel takes a lot longer. While an enamel may look cured and you can carefully handle a tube with direct contact, the paint is still not completely cured. A tube like this will scratch easily, just try it with your fingernail. Avoid putting an enamel painted tube in a cradle at this point, the felt in the cradle will leave marks in the paint.

How long does it take enamel to cure? Perhaps weeks to fully cure, maybe a bit longer. You can help it along on small parts such as finder tubes, and short focus refractors that are about 4" and smaller. Do this by letting the paint cure on it's own for about 24 hours. At that point you can make a suspension system for the tube using bent coat hangers, threaded rod, etc. so that you can hang the painted part in your oven for curing. The key is no painted surface should come in direct ocontact with another surface. Suspend in oven and bake for one hour at about 150 degrees. Have the oven vent on to pull moisture out of the oven. When the buzzer goes off, turn the oven off and open the door. Let the part stay in place until cool enough to handle. This process drives moisture out of the paint and cures it. It also tends to make a painted part look glossier in color and deeper. A part cured like this can be used right after curing.

Unfortunately large parts cannot be oven cured. A hair dryer can help, as can direct sunlight. If you can, just keep a tube off to the side, and let it cure by itself for the next month. Avoid the tendency to use such a tube too soon, patience has it's rewards.

Here is a photo of a JB Weld patched tube prior to sanding, priming and painting.

Barry Simon

Attached Files



#8 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 10:28 AM

2nd shot of the whole tube.

Attached Files



#9 rwiederrich

rwiederrich

    Goldfinger

  • *****
  • Posts: 12617
  • Joined: 17 Nov 2005
  • Loc: Gorst Washington(center of the Universe)

Posted 31 March 2008 - 10:32 AM

One of the hardest things to do when restoring a classic telescope is selecting a color to repaint the tube and trim. Essentially two routes can be taken - you can mimic the original colors as much as possible, or you can go in a completely different color(s) making the scope more an expression of your own personal tastes.

Repainting in an original color is harder than you may think. There are just about a zillion shades of white out there, and matching white is further complicated by how white ages over time. The white on your telescope tube today may not be the white it was when it was new 10 to 15 years ago. Some years ago when I was trying to match the "Unitron White" of my #152 4" Unitron for a photo-guide scope rebuilt, I came as close as I could, but still could not get it quite right. Same thing with the repaint of a Takahashi finder scope. It seems like I spent hours at "Auto Zone" going thru all the import whites trying to find something close. I wound up bringing about 4 or 5 cans of different whites home to see what was best. As it turns out I finally found a very close match in the form of Plasti Kote FM 8141. I never did find what I consider a good match for Unitron White. With a complete rebuild of a 3" Unitron I went with Krylon "Ivory", a color I like much better anyway.

Often I like to go in a completely different direction. The disadvantage of doing that is it will hurt the resale value of a scope, particularly something like a Unitron or a Takahashi. Keep in mind however that your "replacement" paint job has to match so well and look so close to the original that if it is not mentioned, it has to completely fool someone into thinking that it is original. I don't recommend deceiving anyone in this way, you have to mention a rebuild or a repaint if that was done. For some purists, a repaint, no matter how good, detracts from the value of a classic scope like a Unitron.

I do think that going in a different direction with a totally different color can be lots of fun if you know the telescope you are repainting is a keeper or if it was bought cheap, strictly as a fixer-upper. In fact I would thoroughly recommend that everyone buy a cheap garage sale telescope or a less than perfect scope from eBay or AstroMart with the intention of fixing it up. Doing this will help you develop some rebuilding skills, primarily tube repair and painting skills. A good looking telescope that has some of your personal effort in it, that draws lots of compliments will give you plenty of personal satisfaction. Restoring telescopes is a hobby unto itself.

Anyway with a current project, rebuild of a Milo 3" f/18.4 refractor, I have been trying to find the equivalent of what I will call "Vespa" Blue-Green to replace the white that originally was the color of this tube. I think I have found a color that I like. See the attached Dupli-Color color chart. There is a color called "Malibu Mist" which comes close to what my "Mind's Eye" envisions as a good color for my rebuild project. Let me know what you think.

http://www.duplicolo...rs/premium.html

I am going for kind of a different retro look and I think this color will do that. I also think it will contrast nicely with the semi-gloss black focuser and objective cell.

The attached photo shows a repainted guidescope used with a Takahashi FCT 76. The guidescope was repainted with the previously mentioned Plasti Kote FM 8141. Not a bad color match in my opinion, but still not a perfect match.

Barry Simon


Barry..great thread. I needed to find the exact color of my 6"f/15..the one my father built. So I took several parts and had them color scanned. I got both greens matched.

You mentioned in your post..everything I did...great post.

Except my tube was 8 ft long, and 7" in diameter. After it spent 2 days on its rotating jig under heat lamps. I made a rotating jig so I would not have any drips form as the thicker apoxy paint dried. It then spent a week standing upright in my (vaulted) cieling livingroom.

Great post.

Rob

Attached Files



#10 RRavneberg

RRavneberg

    professor emeritus Rest in Peace 19xx-2009

  • *****
  • Posts: 634
  • Joined: 02 Dec 2005
  • Loc: Columbus, OH

Posted 31 March 2008 - 10:40 AM

The issue of restoring is always an interesting one. When a friend and I reworked two Fecker Celestar 6 Maksutovs recently, we opted to do a 21st century renovation of the instruments rather than a mid-20th century restortion. That meant doing everything in the spirit of the original (e.g., no digital setting circles, Telrads,radical changes).

Paint was obviously a major problem, as the Feckers used a speckle finish that was difficult to match. So we did our best with what was available.

Our goal was to restore two unusable instruments to top performance without compromising the original design, not to put something in a museum display.

Every restoration project will have to approached differently and on its own merits. This was just what we did.

Attached Files



#11 rwiederrich

rwiederrich

    Goldfinger

  • *****
  • Posts: 12617
  • Joined: 17 Nov 2005
  • Loc: Gorst Washington(center of the Universe)

Posted 31 March 2008 - 10:44 AM

The issue of restoring is always an interesting one. When a friend and I reworked two Fecker Celestar 6 Maksutovs recently, we opted to do a 21st century renovation of the instruments rather than a mid-20th century restortion. That meant doing everything in the spirit of the original (e.g., no digital setting circles, Telrads,radical changes).

Paint was obviously a major problem, as the Feckers used a speckle finish that was difficult to match. So we did our best with what was available.

Our goal was to restore two unusable instruments to top performance without compromising the original design, not to put something in a museum display.

Every restoration project will have to approached differently and on its own merits. This was just what we did.


I love to restore....
Great paint job, and great application.

Rob

#12 Awesomelenny

Awesomelenny

    Soyuz

  • *****
  • Posts: 3987
  • Joined: 02 May 2004
  • Loc: Long: 81.42 W Lat: 41.21 N

Posted 31 March 2008 - 11:05 AM

Hi Barry,

Excellent article here. In fact, many of the steps you detail here were also mentioned on the Yahoo Unitron Telescopes forum, which you founded and moderated. It was yours that I adopted and learned how to restore the telescopes that I have done.

You mentioned using Krylon's Ivory White on the shortened f/11 telescope. In your opinion, was this a very close match to the aged Unitron color? :question:

As you may know, I restored a 4 inch Unitron from what would have been a trash heap. I used Rust Oleum High Gloss White. That was really white! I was thinking of just lightly sanding that surface with a 400 or 600 grit sandpaper and applying a few coats of a enamel that would most closely match the Unitron white scheme. But that's maybe a later on project.

#13 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 11:21 AM

Hi Barry,

Excellent article here. In fact, many of the steps you detail here were also mentioned on the Yahoo Unitron Telescopes forum, which you founded and moderated. It was yours that I adopted and learned how to restore the telescopes that I have done.

You mentioned using Krylon's Ivory White on the shortened f/11 telescope. In your opinion, was this a very close match to the aged Unitron color? :question:


No, not at all, the Plasti Kote FM 8141 would be a better match for a "new condition" Unitron. I went with the Ivory color because I liked it. Kind of reminded me of the early 90's/mid 90's TeleVue Genesis color. The Ivory is a creamy look color and gives the telescope richness. The Unitron photo that I have posted above does not really show the Ivory color well, the photo makes the Unitron look whiter than it really is.

Barry

#14 Clive Gibbons

Clive Gibbons

    Mostly Harmless

  • *****
  • Posts: 16724
  • Joined: 26 May 2005
  • Loc: Oort Cloud

Posted 31 March 2008 - 02:35 PM

Lots of great info and advice, Barry! :waytogo:

Gosh, that purple planet eater is an eye-catcher!! :cool:

#15 jwaldo

jwaldo

    Smart Mime

  • *****
  • Posts: 3923
  • Joined: 26 Apr 2004
  • Loc: Simi Valley, CA

Posted 31 March 2008 - 05:22 PM

Barry,

Great how-to! It'll come in handy if I ever work up the courage to repaint my 6333 :)

#16 jwaldo

jwaldo

    Smart Mime

  • *****
  • Posts: 3923
  • Joined: 26 Apr 2004
  • Loc: Simi Valley, CA

Posted 31 March 2008 - 05:22 PM

Barry,

Great how-to! It'll come in handy if I ever work up the courage to repaint my 6333 :)

#17 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 05:52 PM

Jim,

Nice avatar. Funny how a fair number of people who are amateur astronomers are also model railroaders. Here is part of my collection, and Espee (Southern Pacific) is a major player in my collection.

Barry Simon

Attached Files



#18 Pedestal

Pedestal

    Skylab

  • *****
  • Posts: 4437
  • Joined: 11 Mar 2006
  • Loc: Smoggy Bottom, Baytown,Texas

Posted 31 March 2008 - 06:01 PM

Barry, can powder coating be done after an epoxy (JB Weld, etc) repair? I would have thought the repair would show through?
Hubert

#19 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 06:29 PM

Barry, can powder coating be done after an epoxy (JB Weld, etc) repair? I would have thought the repair would show through?
Hubert


All I know about powder coating is what I read on line. (The Wikipedia article seems pretty detailed.) Your question is best answered by an outfit that does powder coatings. As the JB Weld would have different properties than would the aluminum (if a refractor telescope tube) the adherence may be different. Check first with the outfit doing the coating for you.

Barry Simon

#20 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • Posts: 2788
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 31 March 2008 - 06:49 PM

Sometimes a repair may be just a simple touchup of a small scratch or chip. If paint is going to be applied on top of paint, a slight difference in color may become very noticeable. Paint tends to yellow with age so even with using the same exact paint, there could be a color difference. You always want to mix your paint well to ensure consistency.

Another consideration is just how compatible one type of paint is with another type. If you are using an enamel touch up you can use it over enamel and lacquer with good results, and with so-so results over an acrylic water base paint. Acrylic can be applied over itself and also over enamel and lacquer with good results. However lacquer presents more problems if used over anything but itself. When used over enamel and acrylic it tends to have a solvent type effect on those paints. The touch up area might skin, or wrinkle. Bottom line, know what you are painting over and know what you are painting with.

Also use a primer compatible with whatever top coat you are using.

If you have a paint chip that is not too large, the best way to deal with that is to have the chipped area facing up and with a very fine brush or toothpick, place a drop of paint in the center of the chipped out area. If fluid enough, a drop of paint should transfer from the brush or toothpick to the center of the chipped out area when that area is touched with the toothpick or brush; it should then spread out, filling the chip. You are filling the chip with paint. If the depression is deep, just put in a few drops and come back later to repeat the process. The paint will settle as it dries. It may take a few sessions to fill the hole. You can paint cure in the oven about a day after the final application. Once the paint is cured, you can very lightly sand the edges with very fine sandpaper. Follow this with rubbing compound and then maybe another session in the oven as the rubbing or polishing compound will soften the paint. Sometimes this can be done so well that the repair is very difficult to find.

Barry Simon

#21 rwiederrich

rwiederrich

    Goldfinger

  • *****
  • Posts: 12617
  • Joined: 17 Nov 2005
  • Loc: Gorst Washington(center of the Universe)

Posted 31 March 2008 - 07:34 PM

Jim,

Nice avatar. Funny how a fair number of people who are amateur astronomers are also model railroaders. Here is part of my collection, and Espee (Southern Pacific) is a major player in my collection.

Barry Simon


Barry..... :smirk:

My train collection spent its time on the rail, on my large layout.

Man your collection is beautiful....

All my trains are stored away...for another day.

I'm green...an I try never to be green.

Rob :bow:

#22 alvin58

alvin58

    Vostok 1

  • *****
  • Posts: 120
  • Joined: 15 Apr 2006
  • Loc: North Shore Lake Superior

Posted 31 March 2008 - 09:33 PM

I have been having a debate with myself since last year. I have the paint match for my Sears 60mm Discoverer and was planning to repaint, flock tube interior and go through the mount to tighten it up. Would I be doing a diservice to the original or this is an acceptable procedure for these old guys?(As this one needs it) Allen

#23 jwaldo

jwaldo

    Smart Mime

  • *****
  • Posts: 3923
  • Joined: 26 Apr 2004
  • Loc: Simi Valley, CA

Posted 31 March 2008 - 10:17 PM

I'm certainly on the fence about repainting (concerns about paint match, paint quality, and safely removing the stickers and whatnot), but I DID go through and re-grease and tune up the mount. I even Loc-tited the declination-axis-retainer nut :whistle:

#24 Preston Smith

Preston Smith

    The Travel Scope Guy

  • *****
  • Posts: 6051
  • Joined: 24 Apr 2005
  • Loc: Eureka, Pa

Posted 31 March 2008 - 10:31 PM

Barry, can powder coating be done after an epoxy (JB Weld, etc) repair? I would have thought the repair would show through?
Hubert


Do not use JB Weld. Use Lab-metal:

http://www.alvinproducts.com/Products/ Alvin Products: Lab-Metal

It has aluminum pigment in it for current to pass through it (so the powder coat will bond).

#25 Telescopeman54

Telescopeman54

    Vendor - Trapezium Telescopes & Services, LLC.

  • *****
  • Posts: 1715
  • Joined: 16 Aug 2007
  • Loc: New Hampshire

Posted 01 April 2008 - 01:51 AM

Barry:

That was very interesting and very informative. You have some unique answers to common problems.

Since I used to be a partner in a body shop I would chose to use other methods of repairing tubes. The exhaust pipe expander it a good idea for small tubes. Once a larger tube is distressed, though, it is more difficult. I have a 6" f/15 refractor that was on loan to a friend while I was in Iraq. A violent wind storm came up and knocked the entire thing over. The tube has some pretty nasty dents. They will be removed by the old "hammer and dolly" method. This is where I take a bodyman's dolly and various hammers and work the metal back into the proper shape. Once you've done this to a lot of fenders and doors on cars it gets to be pretty easy.

Eventually, I will have the tube so close to perfect again that it will be impossible to find the repair areas. Of course, any very minor imperfections will be fixed with spot putty and not epoxy. If any areas need that much material then the repair just isn't done well. My partner and mentor came from the old school where if you had to fill it you had to go back and do it right! I should point out that this is not a criticism of your workmanship. It's just that when we built show cars that cost thousands of dollars we were much more particular about such things. That training becomes a habit over time. After all of the metal work is done, a good coat of Zinc-Chromate primer will be laid down using an air powered spray gun. Zinc-Chromate is superior in its ability to bond to aluminum when compared to regular primer.

The finish is only as good as the preparation. It is not normally necessary for rougher grades of sanding material. On some automobiles, where custom made curves or shapes are built with body filler, or fiberglass, a 60 or 100 grit would be needed. With telescope tubes I don't think I've ever used anything more coarse than 320 grit. Actually, I start with 400 or even 600 grit wet and dry. I use a sanding block at all times. Using one's fingers can lead to an uneven finish since the skin on your hands and fingers is pliable and will mold into small imperfections.

Normally, 600 grit is about the finest that one should use when preparing for primer. The secret, as I mentioned, is in the preparation. Laying down primer, as well as top coats, should be done with a nice fine coat. It is not a good idea to try and cover everything in one session. Lay down a mist coat and let it dry for about 5 minutes. Then another and if necessary, another, then a final coat. Once the primer has dried for about an hour (The temperature has a lot to do with drying time.) you can wet sand the tube. This is where patience and quality start to show. Use a garden hose or a bucket of water to soak the wet and dry paper. Again 600 is a very good choice. Sand the primer gently and keep wetting the paper. The water will carry away the small particles of primer that are being removed by the sanding medium. When the primer begins to show through ever so slightly it is time to stop sanding. Wash the tube and let it dry. Repeat this entire process several times until the primer is built up to a point where none of the tube or earlier paint show through. Let everything dry for as long as necessary.

Top coats are an interesting item. With the huge steps forward in enamel paint it is quite possible to get a very good coat with one painting session. Lacquers on the other hand, are a very time consuming process as well as expensive. That type of paint is best left to someone with a lot of experience in a body shop, so, I will not cover it.

Enamel can be laid down just as was the primer. However, there is no wet sanding involved between coats. Each coat should be done within about 10 - 15 minutes of the last. Some paints will allow up to an hour between coats, but, that just leaves room for a distraction to take you away from the work. After that happens you may need to wait as much as a week before you can continue!

Build up each coat in thin layers. Remember to start the spray off of the end of the tube, carry it across the entire tube and only after the spray fan has left the tube should you stop spraying. Repeat as often as necessary. If light coats are done with care and allowed to partially dry for about 10 - 15 minutes each, there is virtually no chance to have any runs developed. Any run in the paint means that you laid it down too heavily on the last coat.

If you need to have an special color, a trip to a body shop supply house is the best bet. They can mix and match colors that don't even show up in the chip books. By the way, do not be afraid to look through some of the very old chip books from DuPont and Ditzler. Did anyone realize that the paint used by Astro-Physics is the exact one used on the 1986 Corvette? Yep! Check the chip charts against your A-P and see for yourself!

As mentioned by Barry, paint does age. It is exposed to the sun, oxygen, moisture, pollution and all kinds of things that can change the color. If an exact match is needed for a repair job then finding the closest match is mandatory. Once it is close then the paint technicians at the supply house can use their expertise to adjust the mix until it is a dead on match. It may take some time, but, it can be done. I did exactly this on an old telescope. It took us several days, because of drying time for the paint, but, we eventually wound up with an exact match. There was no way to tell which was the original paint and what had been repaired. Oh, yes, paint DOES change its tone when it dries. That is one of the things that the paint technician should consider when mixing the paint.

I am one of those people that like to have some spice in astronomy. I've painted OTAs some very interesting colors. Barry, you weren't the first one with a purple OTA! I did that to my 1965 Jaegers OTA about 7 years ago! I have also painted an RV-6 in a nice blue metallic and an Edmund 4-1/4" in an Emerald Green Metallic! (I think that green was left over paint from my 1972 Dodge Polara!) Heck! I even painted a Celestron 80 with Kameleon Paint! That stuff is expensive! It is about $375.00 PER PINT and that does not include the thinner or hardener!! I will attach some pictures for everyone to examine.

The next thing is finishing the touches. With modern enamels a clear top coat is easy. The same techniques need to be used to avoid getting runs in the finish, but, once it has dried the color coat is safe for a long time. In the days of lacquer paint it was necessary to paint and wet sand as many as 20 color coats then do the same with the clear coat! It was a big pain and a lot of work. However, until enamel paints matured, that was the only way to get that deep lustrous finish that actually had a sense of depth to it visually.

Barry mentioned that enamel paints can take a longer time to dry than is apparent. It's not actually a drying time as much as it is a curing time. The paint surface can dry quickly. However, the thinners that are in the paint below the surface need to leach out and that takes time. Heat, as he mentioned, is a great way to accelerate the process. It used to be, and in some cases still is true, that if your car needed to have paint work done, you would be advised to not wax it for 90 days! Also, the only way to wash it was with cold running water and nothing more for that time period. That is because the paint needed to cure. Now, most shops have huge baking ovens to solve this problem. Still, unless you can put the entire tube, or whatever, into an oven and let is sit for up to six hours, it will need to cure. Again, temperature and humidity are an issue here. Since I haven't a large enough oven for big tubes, I hang them in a corner where the won't be disturbed and leave them alone for several weeks, even months, before I put them into service. This is the only way that I have been able to get the hard finish that I wanted and that wouldn't take an impression from the felt in tube rings when they were tightened down. I am now working on building a large and long baking oven just for OTAs such as the one for my refractor.

One last little thing that many people over look is trim. It's done with cars and boats. Why not with a telescope tube? I've done some nice simple lettering and pin striping on a few tubes. It was just basic stuff and was done with special tape because I have just never been able to paint straight lines by hand. Again, check the pictures and you will see some of that gold trim.

Barry, I almost forgot to mention something. Try the Rustoleum Appliance White spray bomb for the Unitron. I think that it will be about the closest match you will find. I'm pretty certain that the finish on the old Unitrons was the same stuff that was used on washing machines and dryers! LOL

OK! I've just about written a book! What can I say? This caught my attention and it is something that I do and do well. I guess it kind of takes me back to the days when cars were cool and unique and we hadn't a care in the world!! LOL

Clear skies to all and thanks for letting me carry on a bit.

Steve Forbes

Attached Files








Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics