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Red Hot New Concept OTA's

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#51 Astrojensen

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Posted 12 January 2013 - 08:26 AM

BTW, I am impressed with the new OTAs. It's about time someone tried to do something serious to make a lightweight big achro. I've thought a great deal about making one with a traditional truss tube, with a centerpiece that attached to the mount and two ends with the objective and focuser that each attached to the centerpiece with truss tubes. The bad thing about this is that the truss angles become very narrow, if the centerpiece is not quite a bit larger than the objective, in which case the center of gravity sits quite far from the fulcrum at the RA axis, meaning you need a lot of counterweights or a very long counterweight shaft.

I also thought about making a single-pole refractor, much like the one Keith Lawson has made, but I didn't follow up on it in detail and thought that it would have problems if I wanted to attach a shroud, which is almost a neccesity in my climate, or so I thought at the time. Your solution is more elegant and also more solid.


Clear skies!
Thomas, Denmark

#52 jgraham

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Posted 12 January 2013 - 08:49 AM

How does the weight compare with a carbon fiber tube?

Just wonder'n

#53 Astrojensen

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Posted 12 January 2013 - 09:06 AM

I think the weight might be comparable, but carbon fiber tubes are quite expensive in the sizes we are talking about here. They are also not collapsible, unlike the new ISTAR tubes.

Looking at prices for newtonian carbon tubes at Teleskop-Service, I'd estimate that a raw carbon fiber tube for a 6" f/12 newtonian might be around $1000 and that one for a 8" f/12 could be $2k. I could be wrong, though.


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Thomas, Denmark

#54 opticsguy

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Posted 12 January 2013 - 10:18 AM

First; very impressive scope, nice design and I certainly want one.

Second; Not at all an original design when you look at the single element loooong focus refractors way back in the late 1600's (Hevelius' 140 foot telescope).

Thirdly, I would be very concerned with dew on the lens, a definate problem in my area.

Fourth; I want one. :-)

#55 ISTAR Optical

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Posted 12 January 2013 - 01:53 PM

Dew shields are being designed for these scopes and they will become available this year. We have two versions to test before we decide.
cheers,
Ales

#56 mikey cee

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Posted 12 January 2013 - 05:43 PM

I see this thread was been removed from "Refractors" forum. Well too bad but take a peek here folks! http://www.istar-opt...0-12/index.html I believe anyone going to this effort in redesigning refractors to this extent is truly more interested in the hobby than in making a buck! I mean there must be less innovative and easier ways to make money off of amateurs in this hobby. When Istar got my attention as a customer they truly did make a believer out of me and I'm one picky SOB that is hard to impress! :waytogo: Mike

#57 ATM57

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Posted 12 January 2013 - 06:14 PM

Hey, thanks for the honorable mention. Cool. Yes, this was an Istar 8" F/8.8 lens. Super performer. I never had any issues with lens cooling, body heat problems or contrast issues. Properly designed/placed baffles will work quite well despite how the scope looks from the outside. An eyeball look through the focuser reveals only the light from the lens. If interested I can show a photo shot through the focuser with the scope aimed at a bright wall with the scope outside in the sunlight and the only thing you can see is the light from the lens. This scope was a lot of fun to build and use.

The new Istar design should work quite well. It looks like someone spent the time to "get it right". Good design, nice machine work, well baffled and light weight. If I had one I would put it through it's paces and give a detailed report (hint, hint) ;)

#58 ISTAR Optical

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Posted 13 January 2013 - 05:01 AM

Keith, is that you? Great talking to you after so many years (3 I think since you were one of our very first customers for larger lens). Anyhow, I looked at many tubeless refractor designs including yours. Me and our master optician spent countless hours discussing different options but the bottom line is this. If you put baffles in places exactly as you explained (what counts is what you see at the focuser end.. no matter what anyone else will argue with(. This is the reason I posted photo from the focuser so people can see that all you see is the lens up front.. everything else is filtered off by the cross-sections/baffles. What ever remaining stray light must enter the remaining 30 percent (overall scope length) which is a fully enclosed tube with its own set of baffles.
The bottom line is, when we tested the TCR tubeless sceletal scope against fully enclosed old fashioned scope and found no difference, I can say that Im happy and I achieved all what I hoped for. From incredible over 50 percent OTA weight reduction (the main objective)to unchanged resolution. Recently we even round out that now the ballance point is shifted heavliy towards the FOCUSER, not towards the lens as one would expect.... read more at our web site (not sure if I can openly advertize our web site here on CN Vendor forum...) but Im sure people will find it.
cheers,
Ales

#59 ATM57

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Posted 13 January 2013 - 02:49 PM

Hi Ales,

It is interesting to read the comments of those who have never used a refractor designed this way. Their lack of experience causes them to question the validity of such a design. As an "end user" of an open refractor I know that, if well designed, the scope works quite welll. I can say just by looking at your design that you guys have done your homework. Great looking scope! When you take these scopes out to astronomy gatherings it will shut the mouths of the naysayers. There are a lot of advantages to the open design. Keep up the innovative work. It's nice to see something new and affordable in the refractor realm :)

#60 BillP

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Posted 13 January 2013 - 03:11 PM

Ales,

What iStar optics is this new design going to be available with?

-Bill

#61 ISTAR Optical

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Posted 14 January 2013 - 08:44 AM

Hello Bill,

we will build these TCR truss/semi tubed on any scope larger than 140mm and with F/8 and higher. To give you a few examples: Asteria TCR 180 F8 R35 SLIM, Asteria TCR 180 F12 R35 SLIM, Phoenix TCR 204-8, Asteria 204 F8 R35 SLIM, Asteria 204 F12 R35 SLIM and so on up to 250 F11 R35 model which has been ordered by one customer recently.
cheers,
Ales

#62 ISTAR Optical

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Posted 14 January 2013 - 09:08 AM

You are absolutely correct. Thanks God that some of the guys with more open minds do realize these advantages even without looking thru one themselves. Only basic knowledge of optics or even just common sense is what one neeeds to make a sound decision. We will definitely show these in public and I cant wait for first customers so they can do this job for us.. on much bigger scale. I do not argue with any hard core disbelievers, I simply let the course of time and hands on experience to prove them wrong. I know one thing, this is definitely a step back to 1600 century design style.. People including most manufacturers will simply repeat one design over and over. The idea behind is: if it works why fix it.. well, I can not agree. Things can usually work better even if they "work well" now.. Franky, I would not go public with some weird design if I was not more than sure that it works at least as well as closed tube design... I know that I would be eaten alive if I did... have a great day, stay in touch. I wont be able to get on line much during my upcoming trip abroad. Due back in my office by end of February 2013,
cheers,
Ales

#63 ISTAR Optical

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Posted 16 January 2013 - 12:01 PM

Hello Bill,
we will produce these for CLASSIC ACHROMATS?
150 F12 (now produced)
150 F15
204 F/8,8
and for R30 and R35 special doublets
150 F12 R35 SLIM
180 F8 R30
180 F8 R35 SLIM
180 F12 R35 SLIM
204 F8 R35 SLIM
204 F12 R35 SLIM
220 F9 R35 SLIM (F-ratio MAY change on this one)
250 F11 R35

possibly APO Triplet 160 F12
that would be it for some time, but enough for anyone to choose the right one I believe,
cheers,
Ales

#64 ISTAR Optical

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Posted 16 January 2013 - 12:04 PM

Johny,
TCR scopes will have both front and rear dew shield style attachments, we have the design layed out, now sourcing for the right materials. So people can choose what works best for their own environment
cheers,
Ales

#65 zjc26138

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Posted 16 January 2013 - 01:26 PM

I want the TCR 180 F/8 R30. Gotta start saving now. :)

#66 ISTAR Optical

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Posted 17 January 2013 - 04:10 AM

We are designing these as we speak and lenses are also being done. We will have few sets of the original R30 doublets (about 40 percent heavier lens) but to off-set this, we will offer the finished OTAs in TCR construction with an appropriate discount. The new R35 SLIM doublets are now produced in following configurations
150 F5 R35 SLIM
150 F8 R35 SLIM
150 F12 R35 SLIM
180 F8 R35 SLIM
180 F12 R35 SLIM
204 F8 R35 SLIM
204 F12 R35 SLIM

we have an inquiry from one observatory/astronomy club for 230 F20 R35 SLIM, if there is anyone else interested, let me know. Producing two sets will be considerably less expensive than one single lens,
best regards,
Ales

#67 ATM57

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Posted 17 January 2013 - 02:29 PM

Yeah, I'm looking at the 204 F/8.8. R30 or R35 SLIM would be a plus but funding would dictate the choice. They say dreams can come true :grin:

#68 swisswalter

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Posted 17 January 2013 - 04:56 PM

That would be my choice too

#69 ISTAR Optical

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Posted 27 January 2013 - 02:34 PM

Hello Bill,
here is list of scopes to be produced in TCR (combination of truss with baffles and enclosed tube with baffles at the focuser end) and all these will also be made with our all new and completely redesigned R35 SLIM (thin, low weight, better working version of 3 year old R30 doublets)

150mm F5
150mm F8
150mm F12
180mm F8
180mm F12
204mm F6 classic achromat
204 F8
204 F9 classic achromat
204 F12
220 F11
220 F15 classic achromat
250 F11

thank you again for asking and stay in touch,
cheers,
Ales






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