Dobs Mount for C8-NGT

Wanna make a scope? Or better still, grind a mirror yourself. Or, you have some good tips in making a really useful accessory? This is the place to show what your hands can do...
ggodetucsamoht
 
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Re: Dobs Mount for C8-NGT

Postby ggodetucsamoht » Thu Aug 22, 2013 12:33 pm

Gary wrote:
ggodetucsamoht wrote:Infact i am more than happy if anyone can get the whole scope from me and i can go for 10" instead..haha


Post a thread in Buy & Sell and state your price. I suspect you may have potential buyers since shipping a 8" inch solid tube dob from overseas will cost quite a bit.


That's will be marvellous. After i get to know someone who own a 10" dob and looking thru it does amaze me by alot hence i am letting mind to run wild now for upgrading to a 10" or even 12 instead....

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Re: Dobs Mount for C8-NGT

Postby ggodetucsamoht » Thu Aug 22, 2013 12:39 pm

cloud_cover wrote:Falling backwards as in going beyond Zenith? Then that would be because your tube is backward heavy. I see you have both a Telrad and a 50mm finder (total about 2lbs) bolted on to the top of your scope. When horizontal this makes very little difference but when vertical because the moment of force from the tube itself is almost zero (weight x perpendicular distance from pivot) while that from the Telrad/Finder is significant.
3 solutions:
1. Remove one of the finders. Truthfully you don't really need 2 kinds of finders. Or buy a much lighter red dot reticle and /or a 30mm finder (both on sale by ian, I believe)
2. Add counterweights to the opposite side of the tube. Sounds like you only need to weight out the finderscope
3. Increase the stiction of the bearings. This may require roughing up the bearings a bit or applying some friction material such as felt. Disadvantage is that thick material may cause some settling when coming to the end of a motion, resulting in not quite pointing where you want to, similar to backlash.

Hope it helps! :)



Thanks for informative advice.....

1) problem solve which i tried out by removing the 9x50 finder.

2)YEs, i am now thinking of adding counter weight to the opposite side of the tube from the big finder. I am still stuck in the situation of dunno how to add a proper weigh system as i have no intention of drilling on the OTA.

3) Previously i use felt to contact with the PVC cap but it seem not as smooth, change over to 100% plastic contacts with the teflon it somehow satisfy Gary uses. I dont own or have a single experience handling on a dobsonian scope hence i can only get feedbacks from user like him to tell me if my Dobs mount is a Go or a No Go.......

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Re: Dobs Mount for C8-NGT

Postby Gary » Thu Aug 22, 2013 12:56 pm

@ggodetucsamoht - Only managed to try manually find and track objects with your dob in wide low-powered views so far. Very smooth so far. But the real test of the smoothness and dampening of the DIY is via high-powered planetary tracking. You can give it a try and see at what high magnifications, manual tracking becomes too frustrating.
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"The importance of a telescope is not how big it is, how well made it is.
It is how many people, less fortunate than you, got to look through it."
-- John Dobson.

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Re: Dobs Mount for C8-NGT

Postby cloud_cover » Thu Aug 22, 2013 1:11 pm

Its a lot of factors but teflon is the most popular "lubricant"
My 14" uses Teflon pads and a sort of slightly rough almost formica like material to interface. Result is decent stiction but very smooth movements. Gary has previously tried manually tracking mine at 450x, smooth enough. On this aspect its a lot fo experimentation and trial - and-error :)
DON'T PANIC

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Re: Dobs Mount for C8-NGT

Postby Gary » Thu Aug 22, 2013 1:28 pm

cloud_cover wrote:Its a lot of factors but teflon is the most popular "lubricant"
My 14" uses Teflon pads and a sort of slightly rough almost formica like material to interface. Result is decent stiction but very smooth movements. Gary has previously tried manually tracking mine at 450x, smooth enough. On this aspect its a lot fo experimentation and trial - and-error :)


Your nice collection of wide-field eyepieces made that even easier. :)
http://www.astro.sg
email: gary[at]astro.sg
twitter: @astrosg


"The importance of a telescope is not how big it is, how well made it is.
It is how many people, less fortunate than you, got to look through it."
-- John Dobson.

ggodetucsamoht
 
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Re: Dobs Mount for C8-NGT

Postby ggodetucsamoht » Thu Aug 22, 2013 1:54 pm

cloud_cover wrote:Its a lot of factors but teflon is the most popular "lubricant"
My 14" uses Teflon pads and a sort of slightly rough almost formica like material to interface. Result is decent stiction but very smooth movements. Gary has previously tried manually tracking mine at 450x, smooth enough. On this aspect its a lot fo experimentation and trial - and-error :)


Ohhh, you are also having a dobs with you then it is my pleasure to give your dobs a visit and do some molest on it. I have the source to get that formica materials just that it dont sells in loose piece but sell in so long roll.
I will be doing another dobs mount and see if the new one works better.

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Re: Dobs Mount for C8-NGT

Postby Gary » Thu Aug 22, 2013 1:59 pm

ggodetucsamoht wrote:Ohhh, you are also having a dobs with you then it is my pleasure to give your dobs a visit and do some molest on it.


Oh yes. He definitely has a dob. :) Check out his first light report under Milky Way skies: viewtopic.php?f=1&t=11821&p=80927

So welcome to the club!

[smilie=cheer.gif]
http://www.astro.sg
email: gary[at]astro.sg
twitter: @astrosg


"The importance of a telescope is not how big it is, how well made it is.
It is how many people, less fortunate than you, got to look through it."
-- John Dobson.

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