glenm
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Posts: 31
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Hello!
Jan 8, 2011 8:23:45 GMT -5
Post by glenm on Jan 8, 2011 8:23:45 GMT -5
I don't know how I missed this,doh! Nice idea. I have built two OTA's using Istar lenses. The first was a 6" f/10 and the second was a 4" f/12. No doubt you may have seen them on CN. At the moment I am working on a 6" f/8 OTA,which I'm making from GRP. Feel free to ask any questions. Regards to all. Glen. Attachments:
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Jan 8, 2011 9:34:51 GMT -5
Post by Watcher3 on Jan 8, 2011 9:34:51 GMT -5
Welcome aboard Glen! Glad you found us. I really love your scope builds. I think you will be a much valued contributor for the first time builders, (like me). I think we have a good contingent of experienced builders now, and Ales will be joining us soon. This should be a great place for anyone contemplating an ISTAR lens or scope to come for information. Thank you for adding your expertise, and don't forget to spread the word so those in need can find us!
Joe
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Jan 25, 2011 19:24:03 GMT -5
Post by jimcurry on Jan 25, 2011 19:24:03 GMT -5
Beautiful scopes, Glen. I remember the first CN postings about these. How do you polish your aluminum to get such a high gloss finish? Are they clear coated to prevent oxidation?
Jim
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glenm
Full Member
Posts: 31
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Hello!
Jan 27, 2011 18:18:04 GMT -5
Post by glenm on Jan 27, 2011 18:18:04 GMT -5
Sorry for the late answer Jim,been a little busy.
I used a product called Solvol Autosol. I tried all the different polishes available but nothing came anywhere near Solvol Autosol. I used to use tons of it when I was a biker in my younger days.
When first applied there is a chemical reaction which turns the aluminium Black,even more so when using a pan scrub for the first 'hard' polish. This can be buffed off with a rag. Solvol leaves a protective barrier which is very good indeed.
I used my 6" for 6 months with no tarnish showing at all.I did use latex gloves to handle the OTA. The reason for this was not the finish but it gave me a good grip on the 35lb OTA and certainly made handling easier with my dodgy back.
Not sure if you can source this German product in the states. If you can't get hold of any just let me know and I'll get a tube off to you.
Regards. Glen.
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Jan 29, 2011 1:13:10 GMT -5
Post by jimcurry on Jan 29, 2011 1:13:10 GMT -5
Glen: Before I even think about using Solvol what do you use to get a smooth finish. You know, get rid of all the micro scratches from manufacturing or even the saw cuts at the ends of the tube.
Jim
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Jan 29, 2011 10:45:34 GMT -5
Post by mikey cee on Jan 29, 2011 10:45:34 GMT -5
It's called elbow grease. Unfortunately there is no substitute. ;DMike
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glenm
Full Member
Posts: 31
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Hello!
Jan 29, 2011 15:23:10 GMT -5
Post by glenm on Jan 29, 2011 15:23:10 GMT -5
Glen: Before I even think about using Solvol what do you use to get a smooth finish. You know, get rid of all the micro scratches from manufacturing or even the saw cuts at the ends of the tube. Jim Hi Jim, Mike is right,it can be hard work. I found a very good source for my tubes. They come in very good condition. A nylon pan scrub is usually enough and then final polishing with a cloth and different digits On the 6" f/10 OTA I had to use 600 grit wet and dry because the tube was a little worse than the lengths I have bought recently. The tubes come in 2.5 metre lengths and then I cut them myself with the paper and hacksaw method. I suppose the only way to remove deep marks would be to draw file it and then wet and dry. Micro scratches,just depend what you mean by micro. The tubes I make are not like a mirror. I suppose they are 6 foot scopes. They look good from 6 foot away. Regards. Glen.
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Oct 16, 2012 13:38:01 GMT -5
Post by johndaniel on Oct 16, 2012 13:38:01 GMT -5
Glen, you said you had a good source for aluminum tubing. Where would that be. I am designing my first achro and am trying to find out as much as possible about construction and materials. Thanks, JohnDaniel
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Oct 16, 2012 15:36:44 GMT -5
Post by mikey cee on Oct 16, 2012 15:36:44 GMT -5
John we all buy our tubing from Hastings Irrigation. Click on "Industrial Tubing" then click on "Small Miscellaneous Tubing". I've ordered twice with no hitches. You must however sand like heck because it's the nature of the beast. Parallax Rings sells tubing but they just drop ship Hasting's tubes at a hefty markup. The price may seem high to some but there just isn't many choices. But it's an investment to me not a cost....damn sight cheaper than a Nagler and way more important by a long shot!! ;D ;D Mike
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Oct 16, 2012 17:59:46 GMT -5
Post by criverside on Oct 16, 2012 17:59:46 GMT -5
Hi Mike, I sand where I can, but for small deep dings I use a High quality auto body putty, after all the tubes aren't that thick walled to begin with, you dont want to remove any more metal than you have to. For large dents, with care and a few simple techniques, you can remove the ugliest dents, and if you make it worse you can always invoke the ATMs hypocritical oath, and say "thats the way it came".
About Hastings prices, they are very fair, I haven't priced tubing from my local metal supplier, but based on his prices for other material, Hastings is cheap--------Craig
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Oct 17, 2012 13:07:15 GMT -5
Post by johndaniel on Oct 17, 2012 13:07:15 GMT -5
Thank you Mike. I checked out Hastings and they are pretty cheap. Looking at what they offer, which wall thickness would you suggest for 6" f/10-15 achro? Thank you again for your help. JohnDaniel
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Oct 17, 2012 16:52:34 GMT -5
Post by mikey cee on Oct 17, 2012 16:52:34 GMT -5
John they have only one size wall thickness for the 7" O.D. size. They had more when I built my Jaegers 6". It was .064" 35 years ago. Just a short time back when I started my Istar 10" F/11 R30 I bought some 10" O.D. with .064". I'm of the opinion any thickness will do because these tubes are tough. If you have to fabricate a countercell or have one already made that will take a 6" O.D. tube I'd go for it. That's my preferance or the 7" because my cell slipped inside of it. Some claim because of keeping tube clearances larger like say 8" O.D. they can keep tube currents out of the optical path. I think the whole tube is filled with warm air and I therefore don't buy into that logic. Mike
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Oct 18, 2012 18:54:31 GMT -5
Post by johndaniel on Oct 18, 2012 18:54:31 GMT -5
I have an observing question, and that is, what would be the best f/# for a 6" acro for observing and imaging the planets more specificly Jupiter and Mars. I am torn between the f/10, 12 or 15. I also have to consider size (length). Thanks, JohnDaniel
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Oct 18, 2012 19:25:36 GMT -5
Post by criverside on Oct 18, 2012 19:25:36 GMT -5
Hi John, Join the club John, everyone wrestles with that issue in a planetary refractor, optically you want the performance of a 6" f/15 but the tube is "very" long and requires a larger mount. Usually you end up trading a little optically for a tube you can handle. Have you thought about going down to a 5" Or even 4". A 5" f/12 ( maybe even a R30 ) is a manageable scope and very good size for the planets. Hope this helps---Craig
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Oct 19, 2012 12:56:18 GMT -5
Post by Ales - iStar Optical on Oct 19, 2012 12:56:18 GMT -5
Guys, dont forget about ISTAR R30 Anastigmatic doublets. You achieve F15 performance with approx. F11 lens, AND much better resolution and much smaller spot size. The tubes sizes of these R30 systems are much more compact. Just something to think about... cheers, Ales
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