It was hard to be precise, but sitting appears to be 47" and standing 69" give or take an inch.
Erik Chuck, 44"
Deloy _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
Chuck, Why not invert the scope on the Gerrish mount and put the mirror on the high end. That way you can use any focal length and make the whole thing somewhat height adjustable. I don't think the photons have a particular aversion to traveling down instead of up, although CERN may change that any day now. Brent _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
On 9/25/11, Brent Watson <brentjwatson@yahoo.com> wrote:
Chuck,
Why not invert the scope on the Gerrish mount and put the mirror on the high end. That way you can use any focal length and make the whole thing somewhat height adjustable. I don't think the photons have a particular aversion to traveling down instead of up, although CERN may change that any day now.
Hi Brent, good to hear from you! I'm honestly not seeing much practical advantage to inverting it other than swapability, the stand would assume petty tall proportions even with a short-focus scope. Keeping it pointing down is the most compact arrangement. It should work fine with the f/5 doublet.
To elaborate, Brent, the flat and it's yoke won't be a small assembly. I'm wary of cantilevering it at the top end of a long OTA for several reasons. Vibration is one concern, the other is that the only way I can aim this thing will be with digital setting circles. The DEC encoder will be on the flat yoke. Keeping it close to the ground will allow easy access if needed. I also don't want to have to lift that assembly up high since it won't be a lightweight. Also with the entire assembly using a short-focus scope, it can be made much more compact and easier to transport. An advantage to going with the mirror on top is that a diagonal would then need to be used in the focuser, making a total of 2 reflections and a left-right correct image, but still inverted. No big deal at all, since SCT users deal with left-right reversals all the time. But I'm sticking with the compact, original idea. My pockets aren't very deep these days. :o(
The other disadvantage of the inverted mount is that an additional mirror may be needed when the sun is high. So many trade offs, and everyone makes them differently. That's why the world is interesting. From: Chuck Hards <chuck.hards@gmail.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Monday, September 26, 2011 1:59 PM Subject: Re: [Utah-astronomy] Gerrish mount To elaborate, Brent, the flat and it's yoke won't be a small assembly. I'm wary of cantilevering it at the top end of a long OTA for several reasons. Vibration is one concern, the other is that the only way I can aim this thing will be with digital setting circles. The DEC encoder will be on the flat yoke. Keeping it close to the ground will allow easy access if needed. I also don't want to have to lift that assembly up high since it won't be a lightweight. Also with the entire assembly using a short-focus scope, it can be made much more compact and easier to transport. An advantage to going with the mirror on top is that a diagonal would then need to be used in the focuser, making a total of 2 reflections and a left-right correct image, but still inverted. No big deal at all, since SCT users deal with left-right reversals all the time. But I'm sticking with the compact, original idea. My pockets aren't very deep these days. :o( _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
On 9/26/11, Brent Watson <brentjwatson@yahoo.com> wrote:
The other disadvantage of the inverted mount is that an additional mirror may be needed when the sun is high. So many trade offs, and everyone makes them differently. That's why the world is interesting.
You've called attention to a drawback of the Gerrish, namely, the entire sky just isn't accessible in any version of the mount, without additional mirrors. Fortunately the ecliptic is, as is most of the DS "Good Stuff". Really, I like Bruce's ADA mount at SPOC. Full equatorial, and to accomodate different users, the entire intstrument is raised or lowered. It's essentially a motorcycle lift with a telescope instead of motorcycle. My ultimate plan for my own Gerrish is a heated backyard observatory, for winter use. But with Erik and Deloy's help, it can serve chair-bound observers for a season or three, before I scrape the funds for the observatory together.
participants (4)
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Brent Watson -
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