dob base size

[mick pinner]

could the obliging dob owners out there let me know the diameter of the 8-10 and 12" turntables. thanks guys.

[ballaratdragons]

Here you go Mick, all the dimensions you could want for the 12" GS Dobbie.

Aperture / Focal Length Aperture 300mm / Focal length 1500mm
Diameter Secondary 70mm - 23.3% linear obstruction
Primary mirror / substrate Precisely figured parabolical mirror - quality made by GSO
diffraction limited. Mirror substrate: BK-7
Focuser 2" metal focuser. Incl. 1.25" adaptor with brass compression ring
Tube Metal tube - length 145cm - diameter 36.5cm - weight: 19.5kgs
Rocker Box Height 64cm - Diameter 63.5cm - Weight 13.5kgs
Finderscope 8x50 finderscope with metal quick release bracket - multi-coated
Accessories 2" eyepiece TS RK 32mm

[gaa_ian]

10" turntable 555mm, worrks well with wheels !

[RAJAH235]

Mick, My Meade 10" base is 560 mm diam. :D L.

[ballaratdragons]

Mick,

all the dimensions for all the GS models are here:

http://www.telescope-service.com/dobsonians/dobsonians/dobsoniansstart.html

[davidpretorius]

hey mate,

560mm for my 10"

also, we need to be able to add a eq mount (cylindrical bearings)

http://homepage.ntlworld.com/molyned/the_equatorial_platform.htm

we have a thread going, i know you will love.
http://www.iceinspace.com.au/forum/showthread.php?p=41911#post41911
between el's focusser, the stepper motor stuff i am playing with and your buggy, i reckon you will have a good thing for your http://astroshield.com.au/

dave p

[mick pinner]

thank you for the quick response guys, l've been reading the comments and ideas on the tracking and mount ideas for your dobs, in the past some members have voiced concerns about the build quality of their mounts as well as the bearings that they run on, how easy these problems are to fix l don't know as l have had nothing to do with dob set-ups, my point being, if these mounts need to be modified in some ways after they are purchased then have tracking attached, set up on some type of eq mount for polar alignment and then motorized will it by the end be a financially viable alternative to a GEM? l agree to a point that dob mounted scopes are the perfect way for people to get into reasonably large aperture telescope astronomy but it does of course limit what these scopes can be used for without modifications in the future.
At the moment l am having a dob mount made that will hold the tube assembly with tube rings instead of being mounted directly to the bearings, this will allow the tube to be shifted in the rings either forward or backward to counterbalance any accessories such as large eyepieces therefore doing away with magnetic weights etc, it will also allow the mounting of a guide scope in the same way as a newtonian. l am only too willing to assist in any way l can with any ideas someone puts forward. l am convinced that a locally made dob mount that meets the needs of the local astronomical community can be successful but what the end price would be is yet to be decieded, with all the effort you guys are putting in success l think is assured eventually, however when it comes to a final product as we all know we will only get what we pay for.

[slice of heaven]

The dob mount your making Mick, is the base as well or just the alt bearing assembly attatchment with tube rings?
I've checked the clearance between the bottom of the tube and the base and there's only a 45mm gap on the 12". The side supports need to be raised to make it worthwhile.
The standard base is flimsy at best, and extending the side supports without addressing this area is only going to add to this problem.

[mick pinner]

l'm having a complete base made and l am sure it will be a lot more stable than the current models, all the joins are bolted and have steel inserts for the bolts to attach to, l have looked into making a complete dob but at the moment l haven't been able to source the optical tube assemblies at the right price, l am sure that l can supply a base with tube rings at a very good price so if l can source ota's a complete unit will compete favourably with existing scopes.

[netwolf]

Mick, are the tube rings adjustable to suit diffrent appeture OTA's. Also it may be worth while to consider a Split-Ring Equatorial mount design with adjustable OTA rings if possible.

some examples
http://www.jimsmobile.com/old_ngt6_data.htm
http://www.geocities.com/lynol1000/splitring/

some ideas for you.

Ps so many ideas and no talent to make them...

[slice of heaven]

:thumbsup: Mick

[mick pinner]

the tube rings will be scope specific, as for the split ring system if people are going to look towards an affordable dob set-up then they have to be realistic, costs can easily get out of control, one of the things l have encounted since starting this venture is the difficulty in sourcing quality and l emphasis quality products at a realistic price, one challenge is to keep the price in the existing dob range, having said that l will look at the option.

[netwolf]

agreed we do not want it to be overly expensive. would the base you have design be able to take a diffent size ota by changing the tube rings?

[mick pinner]

if it was made to take the largest dob in the GS range the 300 x 1500 then it would be possible to change the tube and ring sizes by the use of spacers between the rings and the bearings, once the prototype is finished l'll post some photos and take any suggestions on board regarding modifications that you guys think maybe necessary to improve the concept.

[netwolf]

Thanks Mick, a common base would be good starting point for a comon platform.