David Cotterell Toronto, Ontario "If an observer actually sees an object, there is no point in referring to a formula to find out whether he ought to see it; and if he fails to detect it, no formula will ensure his success." - W.H. Steavenson 8" f/15.5 TEC Maksutov - 16" f/5 Teeter/Zambuto Dob - TEC 140 - AT 65EDQ APO Refractor - Astro-Physics Mach 1 GTO Mount - iOptron ZEQ25 mount - Discmount DM6 - Canon 60Da
DreamCatcher Dobservatory/AstroTech 16" dob.
G11/Gemini-2/OPWB Canon 60D (unmodified) with 18/55mm kit lens and "nifty fifty" lens Assorted M42 screw mount lenses (28mm thru 300mm) Celestron 102GT refractor (Costco special) 8/10 inch astrograph someday. DeepSkyStacker 3.3.2 StarTools 1.3 http://www.astrobin.com/users/StarGale/ http://everettastro.org/
WO Megrez 120 ED on GP Mount
WO ZenithStar 80 ED II on Porta II
10" Meade LightBridge/Paracorr
Orion ED 100 on Polaris Mount
Astro-Tech 8" f6 Dob
Bushnell Ares 5
Meade 226 2.4" f11.7
SpaceScope 2.4" f15
Quote:My dob's zenith eyepiece height is 78".
Jeff Morgan - Wile E. Coyote School of Telescope Making
Quote:Quote:My dob's zenith eyepiece height is 78". You might want to reconsider the requirement of reaching zenith.Firstly, how much time do you really spend at zenith? If the answer is more than "very little" you picked a very fortunate latitude to live at! Creating a limit of say, 80 degrees only creates a very small "hole" in the sky for you. Anything in that hole doesn't spend very long there. And you avoid the awkward motions of "Dobson's Hole".True it will only gain you a couple of inches - but compared to a Stardust chair, the standard model CatsPerch chair gains you 12". Add the two together and you are just about where you said you wanted to be, and for a very small sacrifice.
Homemade 14.5" f4.3 Truss Dobsonian
"I'd like to remind you at four in the morning my world is very still, The air is fresh under diamond skies, makes me glad to be alive." Randy Bachmann "Blue Collar"
“A mind is like a parachute. It doesn't work if it is not open.” ― Frank Zappa
Quote:I don't have an adjustable observing chair yet, but noticed that if the chair is only a couple inches to short that my back really tenses up trying to reach the eyepiece. So, don't be satisfied with almost large enough.Gale
Quote:Trigonometry tells me the sin of 80 degrees is 0.985 which yields an eyepiece height of 76.8". 1.2" difference....Using the zenith height is a convenient simplification only...Dave
Quote: I am asking for suggestions, designs, etc. for an observing chair which has a seat height of at least 44".
-DannyMy warehouseMy Channel
Clear Skies,Bob One 'scope at a time... "Onward! Ever forward, never straight!" - T. McMahon
I'd rather be driving my .
16"F4.5 meade Starfinder Rebuilt into Truss Dob, with refigured primary. Equatorial Platform 8"F6 Homebuilt dob Orion 4.5" Starblast Meade ETX-60 www.mnastro.org
Quote:Creating a limit of say, 80 degrees only creates a very small "hole" in the sky for you. Anything in that hole doesn't spend very long there. And you avoid the awkward motions of "Dobson's Hole".
Quote:Jon, I agree with your point about viewing near the zenith. My SErvo-cat actually makes observing up there much easier than manual. It tracks for me so I do not have to worry about the difficulties of "Dobson's Hole."
6'' Orion SkyQuest f/5 12.5" Astrotel truss dob f/3.3 20" Super FXQ Starmaster William Optics 80mm ZenithStar ED II 1850/2500 Observing sessions grand total for 2013, 49. So far in 2014, 11
Quote:I've done some math, too.Scope Angle Actual focuser height at center of opening.90 (Zenith)---------7880----------------77.570----------------75.560----------------71.550----------------67.540----------------6130----------------53.520----------------45.5MY focuser is mounted to tilt up a bit so the actual eyepiece height will be slightly higher than above if I use long ones like Ethos. But I doubt it would be even 1/2 inch... Also, this effect only comes in to play when the scope is pointed very low...