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Tom Schumann
member
Reged: 02/07/07
Posts: 23
Loc: Wake, Virginia
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Hello All,
What is the best way to measure the height of a Orion Atlas/EQ6 GEM above the base? I am trying figure out the height for wall/pier height measurements in a dome observatory. Should I measure to the center of the OTA or to the lowest point of the light path? Also, I have seen that one should measure with the scope facing south, is that the correct way?
Thanks in advanced!
Tom
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 EXPLORA-DOME II (Early Bird Committer)
Orion Atlas 10 EQ-G Reflector
"Award Winning" Orion SkyView Deluxe 6 EQ Reflector
Orion Stratus Eyepieces
Orion UltraView 10x50 WA Binoculars
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Galaxyhunter
Pooh-Bah
Reged: 01/02/06
Posts: 1253
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Tom, You need to figure out the object that you want to see which is the farthest South (neg DEC) & then use that DEC # and set your scope(mount) at the Meridian. That will be the lowest point of the Mount/OTA. Then the lowest point in the light path is what you would want to use for your wall clearance.
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Carl
My lousy skies at Hawkeye Observatory
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Mirzam
super member
Reged: 04/01/08
Posts: 118
Loc: Lovettsville, VA
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My approach was to make the walls a few inches taller than my eye level--this blocks out any low level surrounding lights. In my case the maximum pier height was determined by the scope clearance wrt the roof trusses when the observatory was closed. I pointed the scope due south and horizontal and arranged the pier height to make sure that the top of the OTA had several inches of clearance from the roof structure.
For a scope with eyepiece located on the back end (SCT or refractor) this method provides the ability to see objects that are near the southern horizon.
On the other hand if you are using a newtonian, a lower wall height at least on the south, would be part of the design. (roll off to the north; rather than east and west as in my case)
Jim
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SometimesKen
professor emeritus
Reged: 07/15/05
Posts: 505
Loc: Bad Moon Observatory
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Measure down from the lowest useable horizon and take into consideration, height to hatch opening + ring height + wall height.
For my horizons & a Exploradome - wall height 54" + ring height 7" + distance to lower hatch 10" (I think) = 71" from floor to slot opening. That blocks the street lights and gives me everything I could see from my location.
Also take into consideration how you like to observe, sitting or standing at the eyepiece? For imaging it really doesn't matter.
Good Luck
Ken
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As the setting sun / melts below the horizon / the stars applaud her bow. ~W. Terrance~
Bad Moon Observatory - February 1, 2007
39° 54' N - 74° 09' W
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Tom Schumann
member
Reged: 02/07/07
Posts: 23
Loc: Wake, Virginia
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Thanks for the info guys!
The wall height will be kind of fixed, I think. With the door/wall height of about 48" (I don't think I can bend over much lower than that) and the ED II horizon estimated at about 28" gives me a wall height of around 76". 15 degrees to the horizon is what I would like to shoot for, and the pier to wall distance should be about 70".
So 76" - (70" x Tan(15°)) gives me a floor to pier height of about 57 1/4" minus whatever I figure out for the mount base to light path distance.
I would like to be seated to view, but with a high wall like this and a 10" reflector - it looks like I will be standing on a ladder.  or getting a refractor
Heck I have a whole year to figure this stuff all out.
Tom
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EXPLORA-DOME II (Early Bird Committer)
Orion Atlas 10 EQ-G Reflector
"Award Winning" Orion SkyView Deluxe 6 EQ Reflector
Orion Stratus Eyepieces
Orion UltraView 10x50 WA Binoculars
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