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Updated list of premium Dob makers in the USA?

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14 replies to this topic

#1 RadioAstronomer

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Posted 23 May 2020 - 02:04 AM

Hello,

I will be in the market for a premium custom made Dob in the 12"-14.5" size soon. I have seen lists of Dob makers in CN, but they seem to be outdated.

Broken links, websites that have not been updated since 2006, Teeter is no longer in business etc. 

Any ideas of who besides Obsession and New Moon is building Dobs in the USA? I'm interested in makers that provide the whole package, mirror + structure.

Thanks!

Kacper

 



#2 BradFran

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Posted 23 May 2020 - 04:15 AM

Check this thread:

https://www.cloudyni...></span></span>



#3 RadioAstronomer

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Posted 23 May 2020 - 04:28 AM

Thanks that is exactly what I was looking for. I did not see that thread.



#4 waynel

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Posted 23 May 2020 - 02:37 PM

I think that New Moon and Obsession are two of the best options. Check out my comparison here:

 

https://www.cloudyni...-obsession-125/



#5 Starman1

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Posted 25 May 2020 - 02:05 PM

I don't know about New Moon Telescopes, but I don't care for the small UTA, small secondary mirror and small diameter poles on the Obsession.

 

All that being said, the Obsession scopes work fine in the field, especially with lighter or smaller focal length eyepieces.

It is a lot less expensive than a New Moon telescope, too, which could be important.

And a lot less expensive than a Waite Renegade, another possibility.


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#6 Starman1

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Posted 25 May 2020 - 02:07 PM

I think that New Moon and Obsession are two of the best options. Check out my comparison here:

 

https://www.cloudyni...-obsession-125/

Do either Obsession or New Moon Telescopes make standard classic dobs any more?



#7 rowdy388

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Posted 25 May 2020 - 02:17 PM

My New Moon is the classic design but no, they are no longer an option. I don't

get the overwhelming popularity of hybrid and ultralight designs myself. The classic

design has its benefits too.


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#8 Markovich

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Posted 25 May 2020 - 08:10 PM

Do either Obsession or New Moon Telescopes make standard classic dobs any more?

Pretty sure Dave still offers the 12.5"- 18" models in the Classic form.



#9 Markovich

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Posted 25 May 2020 - 08:12 PM

I don't know about New Moon Telescopes, but I don't care for the small UTA, small secondary mirror and small diameter poles on the Obsession.

 

All that being said, the Obsession scopes work fine in the field, especially with lighter or smaller focal length eyepieces.

It is a lot less expensive than a New Moon telescope, too, which could be important.

And a lot less expensive than a Waite Renegade, another possibility.

I think thats the crux, once you stop worrying about specs, you'll find that the Obsession is a tried and true scope with outstanding performance in the field.



#10 waynel

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Posted 25 May 2020 - 08:51 PM

My New Moon is the classic design but no, they are no longer an option. I don't

get the overwhelming popularity of hybrid and ultralight designs myself. The classic

design has its benefits too.

I don't see the downside to a new moon hybrid with the full UTA.


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#11 George N

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Posted 26 May 2020 - 10:26 AM

Do either Obsession or New Moon Telescopes make standard classic dobs any more?

Depends -- on how much money you are willing to spend!  cool.gif 

 

Obsession still lists the 12.5, 15, 18, and 20" (F/4 only) Classics on the website. Last year a guy with a new 18 Classic said he was told that more than 80% of Obsession sales are now the UCs.

 

NMT has "officially" only built the Hybrid design for the past few years - single ring UTA, or 'classic' UTA, rotating truss/UTA or not - metal poll or carbon fiber poll ( remember, with NMT the polls are an articulated single structure ). Unlike Obsession, NMT will at least consider making customer-desired changes to the design - and in at least one case I know of (since I use it) he was willing to make a special 'classic style' 12.5" designed for use by people in a wheel chair. Customer request is where the 'classic' UTA option came from. People wanted them - altho Ryan himself sees no advantage over his single-ring design. For those who think it won't hold collimation - all I can say is - I and several others tested one (20-inch F/3.4) extensively - it DOES hold collimation. Ryan went thru several different design and material changes to get there. The classic UTA does look a lot cooler! Ryan will be the first to tell you that going with such a light-weight structure "has to result in some compromise" - but personally, I have not seen a significant problem with the Hybrid design - especially if that is the only way to get to the aperture wanted.

 

If someone is comparing the two brands - price is certainly a consideration - as is delivery time. Unless something has changed - Obsession builds from a stock of finished parts - so delivery time is pretty short (but also the main reason you can't get changes to the design). About 2 months ago NMT also posted on FaceBook that, since Ryan is now the main 'home schooler' for their daughter (as wife works full time) - delivery of NMT will be slower. Hopefully that will change soon.



#12 stargazer193857

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Posted 26 May 2020 - 11:09 AM

The single ring can compact much better than a full UTA. A nesting UTA required a bigger mirror box.

Full tube baffles can be made. Focuser and ring rigidity are the questions.

I've read claims that single rings have shown flex, but which manufacturers? Also, a flange could be added that goes into the mirror box. I doubt the flange is needed for a well made truss.

I also recall Jon's dobstuff structure flexes more than he liked. He blamed the poles, bit I doubt those 2" poles flex 1/100 enough to notice. I think the rings and their joints are flexing.


The biggest design challenge I see is how to mount the focuser rigidly.

Edited by stargazer193857, 26 May 2020 - 11:45 AM.


#13 Starman1

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Posted 26 May 2020 - 11:35 AM

The single ring can compact much better than a full UTA. A nesting UTA required a bigger mirror box.

Full ring baffles can be made. Focuser and ring rigidity are the questions.

I've read claims that single rings have shown flex, but which manufacturers? I also recall Jon's dobstuff structure flexes more than he liked. He blamed the poles, bit I doubt those 2" poles flex 1/100 enough to notice. I think the rings and their joints are flexing.


The biggest design challenge I see is how to mount the focuser rigidly.

Correct, but flexure there can be reduced by curving the plate the focuser is attached to.

And flexure of the ring itself can be reduced by making it a lot thicker, with a sandwich structure to reduce flex.

After all, a 1.5" thick single ring doesn't reduce the compactness of the design when it is stowed away in the car.

Still, focuser base flexure is a significant problem with all single ring designs with 3+ lbs in the focuser.

 

But:

--contrast will suffer without great modification of the design when set up

--protection for the secondary is minimal, against dew, or damage

--a single ring necessitates longer poles, meaning more flexure and sag unless larger and heavier poles are used.

--the ultralight upper will lower the altitude axis, providing less baffling and protection for the primary mirror

--the shorter mirror box will make boundary layer fans harder to engineer and install.

--installing finder scopes is a lot harder.

 

So I have to ask why a single ring?  What problems are solved with a single ring design that would not be solved by a short 2-ring design like the ES dobs?

It seems to me that a single ring design just causes a lot more problems than it solves.


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#14 stargazer193857

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Posted 26 May 2020 - 11:59 AM

The spider ring is the only one that needs to be deep, if any do. That might only be a plywood trait. The rest of the UTA can be narrower, so it nests into the mirror box without getting too wide.

The point of the single ring is to not have a UTA stored next to the mirror box I the car.

As for focuser board flex, attaching to the truss poles seems to be the way. That does mean longer poles though.

Finder scope space is another issue, although readily seen in the final product whether it actually is an issue.


I'd like a retractable few shield that unrolls and stores inside the UTA.

Edited by stargazer193857, 26 May 2020 - 12:00 PM.


#15 Starman1

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Posted 26 May 2020 - 02:23 PM


The point of the single ring is to not have a UTA stored next to the mirror box I the car.

 

Having a double ring does not preclude the stacking together of rocker box, mirror box and UTA.




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