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Equipment Discussions >> Classic Telescopes

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turk123
Carpal Tunnel
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: starman876]
      #5926028 - 06/17/13 05:51 PM Attachment (17 downloads)

Quote:

So will you come out the same color as the mount




Let's put it this way, I'm already pretty grey!


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Chassetter
sage
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Reged: 07/08/09

Loc: New Brunswick, Canada
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5926045 - 06/17/13 05:59 PM

Any one up for a CN pool to see how long until he is in the driveway?
Also, love this thread!

Edited by Chassetter (06/17/13 06:03 PM)


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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Elli Buk Cave 10" Cassegrain [Re: Chassetter]
      #5926209 - 06/17/13 07:39 PM

Looks awesome. My dec worm gear housing is either aluminum or chrome plated perhaps coz the cylinder part is shiny silver while yours looks brass to me. Is that just a trick of the lighting or it indeed a different color from the end cap?

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turk123
Carpal Tunnel
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: dgreyson]
      #5926267 - 06/17/13 08:15 PM

Quote:

Looks awesome. My dec worm gear housing is either aluminum or chrome plated perhaps coz the cylinder part is shiny silver while yours looks brass to me. Is that just a trick of the lighting or it indeed a different color from the end cap?




The end cap is aluminum and the body is brass. I will get a better polish on it now that I have the buffer. Most of the dec housings I've seen have been brass. I'm not sure I've ever seen an aluminum one.


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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5926654 - 06/17/13 11:58 PM Attachment (22 downloads)

here is mine, definitely silver inside and out. Likely plated and yours was not.

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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Elli Buk Cave 10" Cassegrain [Re: dgreyson]
      #5926669 - 06/18/13 12:08 AM Attachment (18 downloads)

here is what it looked like before polishing

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turk123
Carpal Tunnel
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: dgreyson]
      #5928760 - 06/19/13 07:49 AM

Quote:

here is mine, definitely silver inside and out. Likely plated and yours was not.




What year is your cave? Late 70's?


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turk123
Carpal Tunnel
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5928764 - 06/19/13 07:55 AM

I've been researching how to preserve the polished aluminum look of some of the components. What I found is that highly polished aluminum will not hold clear coat very well. It will eventually peal. A lot of the motocycle guys and car guys use this stuff, Glisten PC. It is expensive though but is said to last practically forever. It has a self leveling ability as it dries over several days and can even be polished. I bought some to give it a try. You need the hardener and metal treatment product also. It can go on with a brush and still get a very nice finish.

http://www.por15.com/GLISTEN-PC/productinfo/GPCGG/


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Chuck Hards
Post Laureate
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Reged: 05/03/10

Loc: The Great Basin
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5928825 - 06/19/13 08:56 AM

Tom I've had very good long-term results maintaining a high polish on aluminum by giving it several good coats of paste wax. The trick is to let each coat dry completely before buffing it out, and giving it four to six really good coats.

I polished an old Edmund 8x50mm finder some years ago and it's still shiny. When I get home I'll pull it out and shoot a pic.

Works well on iron and steel as well, but less well on grained texture. You need a high degree of polish for the wax to do it's thing long-term.


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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5929568 - 06/19/13 03:51 PM

Quote:

What year is your cave? Late 70's?




To be honest I have no Idea. I'm sure Cave man could glance at it and give the date to within so many days of the summer or winter solstice but not I. Doing that exceeds my level of competence.

Mine has the circular holes in the legs rather than the struts, thick cast aluminum end rings and the later style rotating rings so late 70's perhaps. Has Astrola on the casting. The tube was an F6 and had a F4.5 mirror mounted in it when I got it. It came with both a finder and a guidescope but those were gone when I found it. Still had the brackets for them though.


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dgreyson
scholastic sledgehammer
*****

Reged: 11/06/12

Loc: South Carolina
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5929571 - 06/19/13 03:54 PM

I've been told that WD 40 preserves a polish but havent tried it. I use bees wax which seems to work just fine.
Dont use parrafin wax.


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turk123
Carpal Tunnel
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: dgreyson]
      #5929830 - 06/19/13 06:23 PM

Quote:

Quote:

What year is your cave? Late 70's?




To be honest I have no Idea. I'm sure Cave man could glance at it and give the date to within so many days of the summer or winter solstice but not I. Doing that exceeds my level of competence.

Mine has the circular holes in the legs rather than the struts, thick cast aluminum end rings and the later style rotating rings so late 70's perhaps. Has Astrola on the casting. The tube was an F6 and had a F4.5 mirror mounted in it when I got it. It came with both a finder and a guidescope but those were gone when I found it. Still had the brackets for them though.




If you have the rings for a 80mm guide scope I would love to buy them. I found a Meade 80mm. X 1200 and have been searching high and low for rings. PM me. It sounds like yours is late 70's. Cave started doing bizarre stuff to get the scopes out. Sad part of the history


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turk123
Carpal Tunnel
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: dgreyson]
      #5929844 - 06/19/13 06:33 PM

Quote:

I've been told that WD 40 preserves a polish but havent tried it. I use bees wax which seems to work just fine.
Dont use parrafin wax.




I've read quite a bit about polished metals and preserving the finishes. WD 40 works quite well with exposed steel, but must be maintained or the rust comes back. My thoughts are, if I can get the Glisten PC to keep a shine on the counterweights, the $350 cost to chrome them is gone. I love the look of the natural machined surface (grooves) but I am worried about the long term upkeep. If one of you buy this cassegrain off me one day, for $6000 I would hope the finish would hold up. What? ?

Edited by turk123 (06/19/13 06:34 PM)


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Chuck Hards
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Reged: 05/03/10

Loc: The Great Basin
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5929934 - 06/19/13 07:41 PM

Tom, here's the old Edmund aluminium-tube finder that I polished and buffed, then gave 4 or 5 coats of an automotive paste wax with a carnauba base. It's been at least 8 years and it's still shiny. It hasn't been outdoors, just kicking-around in the shop waiting for a scope to be mounted on. But 8 years with no tarnishing is still pretty good.

These originally came with a grey wrinkle finish, then later they switched to a gloss red. This one was an early grey edition.





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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5930010 - 06/19/13 08:33 PM

Quote:

If you have the rings for a 80mm guide scope I would love to buy them. I found a Meade 80mm. X 1200 and have been searching high and low for rings. PM me. It sounds like yours is late 70's. Cave started doing bizarre stuff to get the scopes out. Sad part of the history




I dont want to sell them as I'm using them but I will be glad to strike a mould off one and cast you a pair in Zinc alloy if no one else has a ready pair of original ones to sell. I havent any spare aluminum at the moment, but mine are pot metal anyway I think. You can drill, tap and finish up the castings yourself easy I should think. I have the correct brass thumb screws. The Cave catalog seems to show the same rings on both a 60mm and an 80mm guidescope, so not much ajustment latitude with an 80mm.


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starman876
Postmaster
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Reged: 04/28/08

Loc: VA
Re: Elli Buk Cave 10" Cassegrain [Re: dgreyson]
      #5930060 - 06/19/13 09:06 PM

A lost art making castings. I learned how to do it in sand over 50 years ago and never made another casting. What do you use to melt the metal. I know aluminum has a low melting point compared to most metals. I am sure Turk and I would love to make some castings.

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turk123
Carpal Tunnel
*****

Reged: 07/09/10

Loc: N.E. Ohio
Re: Elli Buk Cave 10" Cassegrain [Re: dgreyson]
      #5930215 - 06/19/13 10:27 PM Attachment (10 downloads)

Quote:

Quote:

If you have the rings for a 80mm guide scope I would love to buy them. I found a Meade 80mm. X 1200 and have been searching high and low for rings. PM me. It sounds like yours is late 70's. Cave started doing bizarre stuff to get the scopes out. Sad part of the history




I dont want to sell them as I'm using them but I will be glad to strike a mould off one and cast you a pair in Zinc alloy if no one else has a ready pair of original ones to sell. I havent any spare aluminum at the moment, but mine are pot metal anyway I think. You can drill, tap and finish up the castings yourself easy I should think. I have the correct brass thumb screws. The Cave catalog seems to show the same rings on both a 60mm and an 80mm guidescope, so not much ajustment latitude with an 80mm.




I'm in only if you document the process and let me do an article on the cave website! Soon I will have another article about casting parts and it will amaze you to see what someone has created. (Sorry I can't divulge yet!) But if you are willing to make the parts, I would be happy to pay materials and labor.

Are your rings like these from my Cassegrain?


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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Elli Buk Cave 10" Cassegrain [Re: turk123]
      #5930253 - 06/19/13 10:46 PM

No, not like yours. Mine have a more slender, elegant looking rounded "Bead" ringing the mounting ring and the Base is hollowed out. See the finder scope ring on page 4 of the Cave accessory catalog, it's an identical, larger version than that. The Guide scopes are above the finder on the same page.
Guide scope rings page 4

Actually, rings like yours would be a lot simpler to cast in a one sided mould. make it a little deeper for shrinkage and sand the top side flat. Because of the beaded ring, I'd have to make a two piece sand mould. One like yours could be machined out of thick stock.


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Datapanic
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: Elli Buk Cave 10" Cassegrain [Re: dgreyson]
      #5930287 - 06/19/13 11:03 PM

Depends on when the rings were made - when I bought the 75' 8" f/7 Lightweight Deluxe, I also order Guidescope Rings that look just like the ones Turk has pictured. I also have the kind Gregg describes but for a finder, not a guidescope - the difference being that guidescope rings have a much shorter stem to keep the weight of the guidescope as close to the OTA as possible because, in order to get proper tube balance, tube weights of equal and usually even more weight than the guidescope would need to be added. The reason Cave's mechanics recommended mounting the guidescope on the rotating rings was that you avoided having additional tube weight issues to get things right.

The stock tube weight that Cave provided was about 1 or 2lbs, which was not enough to completely balance a tube, but close enough. Usually, somewhere between 4 to 6 pounds are needed to balance it all out.

One trick on the Newtonians to see if you have a balanced tube with rotating rings is to point the tube straight up with the finder and focuser lined up with the most weight furthest out and balance it on the RA shaft with the main counterweights on the Dec Shaft. The RA Clutch should have just enough friction to engage the drive. Then, rotate the tube 180 degrees - it should still be balanced. Most cases, it wont be balanced but the OTA can be rotated to some position where there's a happy medium. Ideally, no matter where the tube is pointed and what the rotation is on the rings, you shouldn't have to mess with tube weights or the main counterweights at all


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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Elli Buk Cave 10" Cassegrain [Re: starman876]
      #5930295 - 06/19/13 11:09 PM

Quote:

A lost art making castings. I learned how to do it in sand over 50 years ago and never made another casting. What do you use to melt the metal. I know aluminum has a low melting point compared to most metals. I am sure Turk and I would love to make some castings.




Zinc has a low enough melting point to use an electric hotplate and a cast iron skillet, Aluminum takes a little more heat. I have a Thermolyne Muffle furnace I use for melting Aluminum, but it's size limits how much metal I can melt. As long as you have a pattern and dont burn yourself or catch things on fire, it's a forgiving process you can remelt and do over till it suits you. Very labor intensive so mass production is out as far as I'm concerned. Casting metal is the poor mans substitute for machining.

One can cheaply make a large flower pot furnace out of everyday parts and use charcoal briquettes to cast aluminum if you dont happen to have a muffle furnace. You can hurt yourself pretty seriously so I dont advise the unready to mess with it. Dont cast metal on a wooden patio deck for instance, no.


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