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jason.p

Why Dob?

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I disagree wholeheartedly. I have a 102mm (4") Mak and M42 was neither faint nor wispy when I observed it at 130x a few nights ago. Admittedly I was using a 10mm Delos and I live in the greenbelt.

Fair point ... But I bet the 10" would be spectacular in your area :-)

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Or a 80mm ED and camera and see all the lovely colours and details, not just a greenish-grey smudge.  :evil:  :grin:

google is your friend for that, even if its raining :smiley:

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The only thing about your base is that it may get in the way, and that brace might limit how far you can position the tube for balance. The bearings are on the small side for use with no friction brake. These are not negative criticisms btw, just trying to say what might cause observing issues.

OOUK's tube can be turned in the rings in seconds, no fuss at all. If you can make that base, you can make one like Moonshanes, not sure if the pictures of them are still on here.

At times I sit "under the dob" with my legs under the front of the tube, there are a lot of good observing positions with these things.

Yes, i accept all your points, esp the frame getting in the way. I've made a few tweaks and it spins a bit smoother but still a bit jerky. Actually it worked better than i thought but obviously nowhere near as good as a "proper " one. I think I've gone as far as i can with this "design " and have decided to put the tube back on my Tal 2 mount which is motorised (the Eq5 isn't )

and have a dabble with some basic ap. I just can't help fiddling around, esp trying to make something out of nothing!

Thanks again for you observations.

Jason

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The only thing about your base is that it may get in the way, and that brace might limit how far you can position the tube for balance. The bearings are on the small side for use with no friction brake. These are not negative criticisms btw, just trying to say what might cause observing issues.

OOUK's tube can be turned in the rings in seconds, no fuss at all. If you can make that base, you can make one like Moonshanes, not sure if the pictures of them are still on here.

At times I sit "under the dob" with my legs under the front of the tube, there are a lot of good observing positions with these things.

http://stargazerslounge.com/topic/181536-12-f4-orion-optics-ota-on-home-made-dob-base-my-latest-project/

http://stargazerslounge.com/topic/101507-16-f4-orion-optics-uk-dobsonian-project/

http://stargazerslounge.com/topic/105895-home-made-dobsonian-base/

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Thanks for posting these Shane, great work on those bases/bearings,it would be nice if these were pinned or linked in the DIY, IMHO. These small footprint dob mounts get right out of the way when observing and the increased bearing dia on moonshanes design would be a big asset.

Jason, if you get puttering around and have some plywood, why not give one of these a go?

I'm thinking back now... I'm pretty sure mod John uses this design too...?

Edited by jetstream
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Yes, i accept all your points, esp the frame getting in the way. I've made a few tweaks and it spins a bit smoother but still a bit jerky. Actually it worked better than i thought but obviously nowhere near as good as a "proper " one. I think I've gone as far as i can with this "design " and have decided to put the tube back on my Tal 2 mount which is motorised (the Eq5 isn't )

and have a dabble with some basic ap. I just can't help fiddling around, esp trying to make something out of nothing!

Thanks again for you observations.

Jason

I'm glad you didn't take it the wrong way Jason, you did very well in your build and now if you get a chance maybe want to try another one. It doesn't have to be fancy plywood etc or perfect. 

But then again maybe you have decided you prefer something other than a dob - finding something that works for you is my motto. :smiley:

Edited by jetstream
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That the Dob mount is cheap is obvious and one of its advantages.

But it is also a good visual mount. It needs no meridian flip, you never need to rotate the tube to get to the EP, it is naturally well damped, it is highly portable, it is totally reliable. There are two ways in which it can be motorized (EQ platform or dob driver) and given GoTo for those who so wish.

As an imager I have to have EQ mounts in my life but in visual use give me alt-az any day, manual or driven. I like both driven and freehand observing in different ways.

The secret ingredient for our Dob is Turtle Wax.  :grin:  No really, anything else is less.

Olly

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That the Dob mount is cheap is obvious and one of its advantages.

But it is also a good visual mount. It needs no meridian flip, you never need to rotate the tube to get to the EP, it is naturally well damped, it is highly portable, it is totally reliable. There are two ways in which it can be motorized (EQ platform or dob driver) and given GoTo for those who so wish.

As an imager I have to have EQ mounts in my life but in visual use give me alt-az any day, manual or driven. I like both driven and freehand observing in different ways.

The secret ingredient for our Dob is Turtle Wax.  :grin:  No really, anything else is less.

Olly

There are definite advantages to alt-az mounts sometimes!

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I'm glad you didn't take it the wrong way Jason, you did very well in your build and now if you get a chance maybe want to try another one. It doesn't have to be fancy plywood etc or perfect. 

But then again maybe you have decided you prefer something other than a dob - finding something that works for you is my motto. :smiley:

I think i would like to have a go at another one, having a look at Moonshane 's threads and appreciating all the advice in this thread has got me thinking . The biggest problem i see is adapting the 200p tube to sit in the trunions(?) Any ideas?

The more I think about it the more I want to have a go!

(Oh dear.......... looks like I may have to apply for membership of the Dob squad)

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I think OOUK makes the tube rings that can be used, they are very handy- maybe some others would know better about this. davelloyd used a OOUK base/rings/bearing for his SW OTA I think.

Edited by jetstream

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If you look at my 6" dob build you can use the standard rings.

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For me the dob is the best aperture bang for buck. My 10 inch manual dob was under £500. I have a 16 inch goto dob as well. I have no idea what kind of goto equatorial mount I would need for that but what a heft it would be to lift it onto the mount and what sort of price would that mount be?!

I have an SCT and refractors too. I like using them all, they all have their plus points. I observe with my 60mm frac on summer hols. I don't get to use the 16 inch dob that much, most of my observing is solar with the refractors and safety solar filters.

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If you look at my 6" dob build you can use the standard rings.

Thanks for that. I assume the design with a single standard ring is also ok for the 8 inch, or bigger. When i was doing my own design i dismissed the idea of using a single clamp because i assumed the tube would not be held rigidly enough or might distort. I could have saved myself some trouble!

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Look at post 70 in the 6" thread

In the end I used both rings attaching top and bottom of the bearings

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Being a 9-stone weakling I've made wooden dobsonians that are lighter and easier to manage than the equivalent metal-monster versions. My present 8inch weighs 12.5 pounds, the Optical Tube Assembly weighs only 11 pounds.  Haven't tested it in a strong wind yet but it has a very low rocker box and thus a low centre of gravity  Was it not Hamlet who said; 'Who would Fardles bear, to grunt and sweat under a heavy Dobsonian' ?   

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Was it also Shakespeare that said "a large scope in any other format would not move in altaz sweet"

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Look at post 70 in the 6" thread

In the end I used both rings attaching top and bottom of the bearings

Sorry, missed that part. Think i'll have a go. I'll have to find another ring. I used the other one as a rotation stop on the other tube.

It will be an interesting project as the bard said " the course of big dobs never did run smooth"

(Sorry, best i could do)

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I miss the tracking at high powers I had with an EQ5 (and drives). The dob can make my back ache if I don't sit down. However I did own the 200p EQ5 with the 250px and found the dob was used most of the time. The simplicity of it won over. I would go back to an EQ if I got into imaging

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... Why not Dob?

(for visual - particularly DSOs)

Simple, effective, elegant, intuitive design when well executed.

A cheap eq platform offers tracking for high power planetary views. Truss designs facilitate portability in large aperture scopes.

But then again, I'm biased ;)

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... Why not Dob?

(for visual - particularly DSOs)

Simple, effective, elegant, intuitive design when well executed.

A cheap eq platform offers tracking for high power planetary views. Truss designs facilitate portability in large aperture scopes.

But then again, I'm biased ;)

+1

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I have just built a dob base for non used 200p and I am converted.

Set up time 25 seconds.

Kids (under 5) can use it easily

Cheap as chips to build the mount

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