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  #1  
Old 22-08-2006, 07:28 AM
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iceman (Mike)
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DIY: 16" tri-dob - Adventures in Building an Ultralight Telescope

Hi all

Tim Nott (tnott) has kindly written an DIY article on the adventures building his 16" tri-dob. It's a very good read, and well worth a look if you're into ATM. You can read the article on the IceInSpace Projects & Articles page, or directly by clicking on the link below:

16" Tri-Dob - Building an Ultralight Telescope

Thanks to Tim for writing the article!

If you'd like to submit an article or review for the site, please contact me!

Last edited by iceman; 23-08-2006 at 05:48 AM.
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  #2  
Old 23-08-2006, 05:49 AM
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Article uploaded.
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Old 23-08-2006, 05:46 PM
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Astroman (Andrew Wall)
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Awesome scope Tim, that looks a real work of art, cant wait to see it in person. Congratulations to you and your telescope building skills.
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  #4  
Old 23-08-2006, 07:36 PM
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hmmmmm.......that is excellent, rough price???

I would love one of those in a few years time!!
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Old 25-08-2006, 03:44 PM
stringscope (Ian)
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Wow, Fantastic Tim. I am envious.

Regards,
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  #6  
Old 29-08-2006, 05:19 PM
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Quote:
Originally Posted by davidpretorius
hmmmmm.......that is excellent, rough price???

I would love one of those in a few years time!!
Hi David,
The scope cost roughly $3,000 all up, but I did get the mirror with the small chip for $850 Canadian. A commercial premium Dob from Starmaster etc. would probably be more than double this cost, although there may be a Guan Sheng/Lightbridge 16'' truss out before long (I doubt it would have premium optics though).
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Old 29-08-2006, 09:05 PM
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Very nice Tim, looks very professional. We'll have to hook up perhaps for a viewing night when my 16" is complete!
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  #8  
Old 29-08-2006, 10:13 PM
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gaa_ian (Ian)
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That is a great scope, a little easier to move around than our 18" Monster !
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  #9  
Old 30-08-2006, 08:24 AM
Mark Elkington
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Hi Tim, Thanks for the interesting commentary on your dob. A very nice piece of work.

At various meetings of my club, I've had the chance to use 8, 10, 12, 16, 18, 20, 22 and 30 inch dobsonians. There's some agreement that a fast 16 is a sweet spot in terms of light gathering and useability. The 30 inch stays in the shed most of the time (how tragic is that?), the long 18 gives lovely views but requires a rather tedious step ladder, and the bread-and-butter 8s, 10s and 12s often leave you wanting more.

Happy viewing!

Mark
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  #10  
Old 02-09-2006, 01:11 PM
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Rodstar (Rod)
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Lovely looking scope, Tim. One aspect of scope design that is often not given sufficient "weight" in the choices people make, is portability and ease of set up. Seems to me you have nailed it with your design.
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  #11  
Old 03-09-2006, 02:51 PM
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Congratulations on a great work of art, as well as a great article. Very beautiful and very informative.

Steve.
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  #12  
Old 16-09-2006, 09:40 PM
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I had a chance to look through this scope tonight, it performs aswell as it looks, it is really a nice pece of work, its going to take me days to come down from this high. The images through it are nothing short of supurb, drool factor is 9/10.

Well done again Tim. Hope it cleared up for you.
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Old 17-09-2006, 08:03 AM
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Tim

This is a really impressive scope. Just about perfect for bedouin astronomy. I am not sure about the lack of a shroud. I am told that you can tell a slightly less dark background without a shroud. It would be easy to fit one.

I once built a 16 along the traditional kreige obsession design and it really was too heavy for one person. You do need to make a special effort to remove excess weight at this size.

I would really like you to publish a more complete set of plans and instructions so anyone else can copy this design. The 16 inch scope is just about a perfect balance between aperature and portability.
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  #14  
Old 17-09-2006, 10:26 AM
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Wow, you've got me reaching for the router. Thats a great design and well executed. I particularly like the compactness of the tri-dob approach. Getting the CG and altitude axis together is the real challenge of this type of design as you say, and often results in large altitude sectors. Well done.
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  #15  
Old 19-09-2006, 07:19 PM
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Andrew, thankyou for your kind comments - you're welcome to look through it anytime you want as long as you don't get drool on the primary. The Veil and the Eagle nebulae with an OIII filter were particularly exciting.

Argonavis, the main design basis was from Mel's website:
http://www.bbastrodesigns.com/tm/tm.html
Some others have printed the plans out from this website and modified them to suit their particular needs. I do have the workings from my cad programme, but they only suit my mirror's size, focal length, thickness, weight, etc. Almost every ATM telescope is different. Also, I had to modify some parts once they were cut - the top ring was slightly too small to avoid vignetting because I followed Kriege/Berry's recommendation of 1/2 a degree field of view, instead of the 1.25 deg.view possible with 7mm exit pupil eyepiece in this scope. I also found that when I was putting the parts together that I had to cut out a section from the flex-rocker to allow free movement of the mirror box (how embarrassing!). Having said this, I'm happy to email the cad plans to anyone that wants them (you need emachine shop to open them), but the text required to exlplain them would fill an entire book.

For those wanting to use this design, I recommend doing as I did, as I explain in the article:

"The design of my telescope was basically a modified version of Mel’s “Tri-Dob” and was finalised with a combination of theory and practical tips from Mel’s website, The Dobsonian Telescope, as well as help from the Amateur Telescope Makers Chat Group (http://astro.umsystem.edu/atm/search.html)."

Andy Martyn's spreadsheet (email me) or Newt is also vital for optical parameters. Any further info required just let me know.

Tim

PS: Mel Bartels and some other experienced telescope makers really don't see a shroud as necessary on a dob (esp. at a dark site), as long as it is properly baffled:
http://www.bbastrodesigns.com/tm/ul-dobs.html
I think I have worked out a method in theory though, involving spiraling springy wire around the tube like air conditioning tubing, then pulling a shroud over the top....hmmm.
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Old 24-04-2008, 06:22 AM
ssjoe66
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What a nice coincidence...

Tim,

I'm new on the site, looking for info on the 16" Dobs and found your project.

Here's where history, written by those who make history, makes the difference.

Excellent and beautiful job on this telescope. I'm very impress, and hope I could share some knowledge on the very near future.

Keep Going!!!

José
Orion SkyQuest XT10 Classic
Burgess Planet Hunter 80mm
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  #17  
Old 26-04-2008, 02:03 AM
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Quote:
Originally Posted by tnott View Post
PS: Mel Bartels and some other experienced telescope makers really don't see a shroud as necessary on a dob (esp. at a dark site), as long as it is properly baffled:
http://www.bbastrodesigns.com/tm/ul-dobs.html
I think I have worked out a method in theory though, involving spiraling springy wire around the tube like air conditioning tubing, then pulling a shroud over the top....hmmm.
On the little 8" truss dob I built for my sons, it has an exposed secondary like
your design but slightly different. The thing I found most annoying was when
you look through the EP your mouth is pointing right at the secondary mirror
and unless you continually held your breath it would fog up all the time. In
the end I got sick of doing that and made a shroud. The difference in
performance as well as ease of use not having to hold our breathe has made
it a pleasure to use.

Btw, on another note, are you intending to add an Argo Narvis system to
this design? I'm about to start my next scope and hope to be ordering bits
around the end of this month, so I'm also looking at compact designs.

regards,CS
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  #18  
Old 26-04-2008, 07:05 PM
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As mentioned in the article, I use an Astrosystems secondary dew heater to avoid the problem of the secondary fogging up. It is a great device which measures the temp. of both the ambient air and the diagonal and only puts in just enough heat to avoid dewing. The primary never dews up.

As it happens, I am currently installing Argo Navis and Servocat Junior onto this scope. In a way it almost seems a pity because it moves so well manually. I have had to retrofit a central point of rotation to the Azimuth and am using 2 tangent arms to get the Altitude pivot point.

I am also 1/2 way through making a shroud, using elastic cord to fill the gaps left by the 6 poles. I would only use this when at a public night to stop kids dropping pizza on the primary. I have tested the scope with a temporary shroud around the scope at a dark site and it has not improved the contrast. The secret here is the positioning of the (flocked) baffles.

Had an issue with flexure in the top ring leading to the secondary going slightly out of collimation when moving from horizon to zenith. Have solved this by reinforcing the top ring with aluminium tubing bent into rings. See photo from Snake Valley camp last month.

Will post an update when completed. The scope continues to provide outstanding images of hundreds of objects!
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  #19  
Old 26-04-2008, 07:29 PM
CoombellKid
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Quote:
Originally Posted by tnott View Post
As it happens, I am currently installing Argo Navis and Servocat Junior onto this scope. In a way it almost seems a pity because it moves so well manually.
I bet it does, having the altitude and azimuth bearing working so close to
each other also helps. It is the single most thing that I like about this design.
Apart from the portability feature. Pitty you cant make the truss poles
shorter, you could fit the whole thing into a suitcase.

Please keep us posted on the Argo Navis installation

regards,CS
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