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Brent
member
Reged: 11/18/04
Posts: 63
Loc: NE Missouri
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Does anyone use a binoviewer with their Questar 3-1/2? If so, is it "worth it" (do the advantages oughtweigh the added inconvenience)? And which binoviewers would you recommend?
thanks in advance,
Brent
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CharlesStG
sage
Reged: 01/01/06
Posts: 243
Loc: Kansas USA
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Brent, I have a Denkmeier binoviewer which I have used with my 3.5 Q. I find that for daytime terrestrial viewing it works very nicely and on very bright objects for astronomy, such as the moon and solar. However, I find the images too dim on anything else for astro and follow the general rule that you typically want 5" of aperture to use binos with pleasure on the heavens. Using my custom Meade-Terabeam 5" Mak, the binoviewer comes into its own for astro. That's been my experience. Also, with a Questar 3.5, you will want a counterweight to balance the heavy weight of any binoviewer and even then, you risk squashing the spring disks at the base of the forks which could result in wobble to your mount. Hope this helps.
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Charles
2X Meade/Terabeam ETX-125 variants w/DDII Control
A few more Meade ETX-125AT UHTC
Just one APM/TMB 80/480 LZOS Super APO, FT Focuser
Working on 8"f/12 D&G folded bino-refractor
Denk binoviewers until work is done on above
Still working on elevated observatory/spaceship
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Brent
member
Reged: 11/18/04
Posts: 63
Loc: NE Missouri
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Charles,
This helps very much. Thank you.
By the way, how easily are the spring disks squished? Would mounting a substantial camera (say a Leica M6 with 90mm f/2) be ill advised? I do have a counterweight for piggyback photography. Thanks again.
Brent
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CharlesStG
sage
Reged: 01/01/06
Posts: 243
Loc: Kansas USA
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Suk Lee, could you answer this question for Brent? I don't know what it would take, quite honestly. The Q should be designed to take some load, how much is uncertain.
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Charles
2X Meade/Terabeam ETX-125 variants w/DDII Control
A few more Meade ETX-125AT UHTC
Just one APM/TMB 80/480 LZOS Super APO, FT Focuser
Working on 8"f/12 D&G folded bino-refractor
Denk binoviewers until work is done on above
Still working on elevated observatory/spaceship
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Suk Lee
Post Laureate
Reged: 10/07/03
Posts: 4344
Loc: Pleasanton, CA
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Hi Brent and Charles. The Leica M6 is a pretty beefy camera, like the Nikon F3 I mounted on my Q (prime focus). With the F3 I had to hang the counterweight WAY out on the end of the velcro arm thingy.
After only a relatively few sessions (less than a season's worth of shooting) I squished the disks. A 90mm f2 is a pretty hefty chunk of glass (and boy, that must be a NICE lens), my guess is that it would also do a pretty good job on those springs. 
Suk
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http://www.siliconvalleyskies.com
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Suk Lee
Post Laureate
Reged: 10/07/03
Posts: 4344
Loc: Pleasanton, CA
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Oops, hold on, the M6 is a rangefinder, right? I was thinking of the R6 SLR. Maybe you could get away with the M6...
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http://www.siliconvalleyskies.com
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Brent
member
Reged: 11/18/04
Posts: 63
Loc: NE Missouri
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Thanks, Suk. I think I must give it a try, don't you?
I am a little surprised that the springs would squash so easily on a telescope that is touted so much for astrophotography. I wonder how many sets of springs Hugh Entrop went through.
Thanks again,
Brent
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Suk Lee
Post Laureate
Reged: 10/07/03
Posts: 4344
Loc: Pleasanton, CA
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Um, well, Questar did a tremendous job marketing the Q, but it's not really a great general prime astrophotography platform. At F14 or so, and a T-stop of 16 or so (T-stop is actual light throughput vs the theoretical f-stop) it's really photographically slow.
I would definitely try the piggyback though... I wonder how that lens will do wide open, then stopped down 1 f-stop. Don't be disappointed if even a mighty Leica lens has aberrations wide open at the edges - astrophotography is the ultimate test of a lens...
Cheers,
Suk
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http://www.siliconvalleyskies.com
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Brent
member
Reged: 11/18/04
Posts: 63
Loc: NE Missouri
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Suk, thanks for the response. A few years ago, I used the 90 in question, wide open, piggybacked on a TV Pronto which was mounted on an alt-az mount with slow motion controls. I used Ektachrome 1600, since I could only hand guide for a minute or two before worrying about field rotation issues. At least I was shooting in Utah's high desert, so sky conditions were good. The exposures were wonderful. The slide I did of the M43 region clearly shows Bernard's loop. I don't recall any edge problems--certainly no egregious ones.
I was traveling back to Utah this summer, so I was wondering if I should try it again, this time with the Questar's tracking capabilities.
regards,
Brent
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Clive Gibbons
Mostly Harmless
Reged: 05/26/05
Posts: 12084
Loc: Oort Cloud
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Quote:
Charles,
This helps very much. Thank you.
By the way, how easily are the spring disks squished? Would mounting a substantial camera (say a Leica M6 with 90mm f/2) be ill advised? I do have a counterweight for piggyback photography. Thanks again.
Brent
Hi Brent.
The most load I've ever piggybacked on my Q3.5", was a 135mm f/3.5 lens, with 2x teleconvertor, on an Olympus OM-1.
The Q's drive handled that for approx. 2 minute exposures, without any slippage.
Have fun! 
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A few telescopes of dubious value.
Understanding wife and three curious cats.
"Semper ubi sub ubi"
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