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dobsonian mount for 300PDS ?

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#1 drago

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Posted 09 October 2013 - 12:45 AM

Hello!
Maybe anyone has already done to building dobsonian mount for sky-watcher 300pds OTA (12") ?
thinking about buil;ding that dob for these OTA.
think, plywood is a good material for that, but maybe anyone can say, what thickness is optiimal? 18 - 21 mm ?
i be happy for any suggestions and advices.
thanks

#2 eyepiecedropper

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Posted 09 October 2013 - 05:26 PM

Hi, I´ll post some pics tomorrow. But be warned, it´s rather crude. No fancy notches. 15mm plywood. But it works nicely without backlash and motions are smooth.The az bearing is a lazy susan turntable unit out of plastic with some inherent friction. No overshooting. The alt bearing has a diam. of 400mm with belt strap on Teflon. It works surprisingly good, but all in all i would´t use it as reference ;-)

Regards, Martin

#3 drago

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Posted 10 October 2013 - 12:44 AM

ok, thanks, i be waiting.
looking also on some russian and english projects, and think as alt bearing try use a rollers wheels.
15 mm plywood not too thin \ flimsy?
i thinking about 18mm laminated from both sides. think a regulate alt friction like on a serial "skywatcher" dobs - via tighten construction and add friction via that...
sorry for my bad english...

#4 eyepiecedropper

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Posted 11 October 2013 - 10:20 AM

Hi, the dimensions:

alt bearing diam 360mm
groundboard 500x500mm
clearance between side parts: 400mm
thickness of plywood: 15mm (you can see that i stiffend the open end of the box with 20mm square pipe)
distance between ground board and center of alt bearing: 680mm, that gives you a clearance of 170mm between scope and ground board.

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#5 eyepiecedropper

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Posted 11 October 2013 - 10:21 AM

next pic

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#6 eyepiecedropper

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Posted 11 October 2013 - 10:22 AM

last one:

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#7 Pinbout

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Posted 11 October 2013 - 10:56 AM

i be happy for any suggestions and advices.



love the astrogoods design concept with his clamshell rings.

#8 drago

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Posted 11 October 2013 - 01:21 PM

eyepiecedropper:

Danke shon! :)
i see, you not using azimuth bearing at all? what observations can possible without az axis? :-O
and why groundboard is 50x50 cm, if clearance between walls is only 40 cm?

#9 eyepiecedropper

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Posted 12 October 2013 - 04:43 AM

hi, as i said: this thing works, nothing more. usually all of my scopes are eq-mounted.
the az-bearing is a turntable unit.
http://ecx.images-am...41djLlBOYhL.jpg

You want to build a nice looking one:

http://www.deepsky-b...ckerbox-GSO.htm
http://www.astrotref...TOPIC_ID=152694
http://www.astrotref...TOPIC_ID=106315
http://www.astrotref...unde-Teil1.aspx
http://dobstuff.com/...omrockerbox.htm

Regards, Martin

#10 eyepiecedropper

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Posted 12 October 2013 - 06:42 AM

some instructions:

http://stellafane.or.../rockerbox.html
http://www.instructa...scope/?ALLSTEPS

#11 drago

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Posted 13 October 2013 - 05:16 AM

thank you!






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