Wanted: Source for New Large Aperture (>18") Dobsonian Telescope

[mtoma...@comcast.net]

Can any of you recommend a manufacturer of a large aperture (>18”) Dobsonian telescope? I had been hoping to purchase a 20” Obsession “Classic” telescope this year, but Obsession no longer makes this model.  I confirmed that directly with Dave Kriege of Obsession Telescopes.  He recommended its 22”“Ultra-Compact” ‘scope.  But even its website states that the “classic” design is more stable than the “ultra-compact” design.

I suppose that I should have attended last week’s Cal-Star event.  In the drone video that one of you posted, I saw several large aperture telescopes constructed similarly to how Obsession used to make its “classic” telescopes (i.e., wooden box-in-box base, robust secondary mirror / focuser assembly).

I prefer a Dobsonian with factory-installed digital setting circles and “Go-To” capability.  (I primarily will use this ‘scope for stargazing with the public and with friends.  Neither audience has the patience for me to star-hop to find objects.  I have no plan to do astrophotography.) Size and weight of the ‘scope are not limiting factors for me.

Incidentally, are any of you on this forum owners of Obsession’s 22” “Ultra-Compact” telescope?  Any regrets?

Any suggestions or recommendations will be greatly appreciated.  Thanks in advance.

Mark Tomalonis

(Without a telescope since spring 2020.  It’s killing me.)

[ma...@astrospotter.com]

Many TACos have large dobs from Star Structure.    https://starstructure.com/     

These guys START at 20"

These are high quality instruments respected by many members of this list

Marko

[John Pierce]

On Fri, Oct 15, 2021 at 12:20 PM mtoma...@comcast.net <mtoma...@comcast.net> wrote:

Incidentally, are any of you on this forum owners of Obsession’s 22” “Ultra-Compact” telescope?  Any regrets?

a guy in the Santa Cruz club has one that he frequently brings to outreach events...    I have had a 20" f/5 Obsession "Classic" setup right next to it several times.     the UC seems jiggly, and is prone to windmilling in the breeze, and takes longer to assemble and break down for transport.   OTOH, it fits in a Honda Fit, I don't think the Classic would, it fits in the back of a Tacoma, and would easily fit in a mid or full sized SUV or van with the back seats folded or .removed.

[Pawan Singh]

I have been using UC 22 for a few years. It is a pretty good scope. It fits in my Toyota Prius and that was a requirement for me. 

I would not recommend a UC22 with ServoCat. It is great as a push-to scope. With ServoCat, the cables can be a pain if they come off.

There will be a slight collimation drift from vertical to horizontal positions. You may or may not tolerate it. If you cannot, you should not get UC22. If you can, you can collimate at 45 degrees and it works pretty well.

Some suggestions if you do go UC22 route:

1. If you do not need to fit in Prius and have vertical clearance, get the bearings which do not fold.

2. Get 4" secondary instead of regular 3.5" secondary.

3. Get 360 degree baffle for the UTA.

BTW - if you are looking for a used one, you can have mine :-) I am looking to go down in size to 16" so that I do not need a ladder! UC22 is a F4.2 and I only need to go 1-3 steps - but even that can be a hassle if you want to observe for 3-4 hours.

[Alan Agrawal]

Hi Mark,

I can highly recommend Starstructure.  I have a 24” f3.3 and it has served me well.  Its a welded aluminum scope, IMHO its the best structure for Dobs 20” or larger on the market.  Mike Zammit, who makes the telescopes and is owner of the company is incredibly knowledgeable and helpful.  

Good luck!

Best,

Alan

On Oct 15, 2021, at 12:25 PM, mtoma...@comcast.net <mtoma...@comcast.net> wrote:



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[Alan Agrawal]

PS, while I have tremendous respect for Dave K. at Obsession, I would pass on the 22” UC : a close friend has one, and the mirror is great, but he often spends the night trying to get his goto pointing to work better.

Best,

Alan

On Oct 15, 2021, at 2:56 PM, 'Alan Agrawal' via The Astronomy Connection (TAC) <sf-ba...@googlegroups.com> wrote:



[Andrew F. Pierce]

I sold my 18 inch UC, it was too fiddly

 

    Andrew Pierce   

    Woodside Corporate Center

    2055 Woodside Road, Suite 110

    Redwood City, CA 94061
    Phone:  (650) 843-1900
    Email:  api...@pierceshearer.com

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[Julien Lecomte]

I tried a UC22 at CalStar last week (not sure whether it was Pawan’s, I am not good with names) and while it is not as stable as a more traditional dobsonian, it seemed perfectly useable to me. I briefly explored the heart of the Perseus galaxy cluster with it.

A UC is not a perfect scope (there is no such thing in the market, you’d have to build it yourself) but it is great at what it does: extremely compact and extremely large. Tradeoffs…

- Julien

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[Jeff Gortatowsky]

The UC22 is flawed as I have pointed out on the Facebook group. But worse, the dentist does not give a crap and keeps making them. 

Most complain about collimation which is odd. I have never had that issue. But the drive mechanics and assembly are shite. And its not ServoCats problem.

It is the overall design, and terrible mechanical tolerances.

Find a used classic. I'd trade my driven UC-22 straight across for a driven 20inch anything (Classic, Starmaster, etc). Or sell in Socal for 10.5K which is loss of almost 4K

Lesson learned. :(

Jeff Gortatowsky... California

"Religion, together we will find a cure.", R. Dawkins

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[ma...@astrospotter.com]

I don't know the UC22 but it is rather flimsy lookin.   Anyway, listen to Jeff G here as he knows a thing or two about telescopes and big dobs.

In realated news I LOVED the usage of   'shite' and googled it (yes I know, not a REAL word ... yet).    It is a common alternate spelling apparently from Ireland, those boys are not known for being always 'proper'.   Anyway, I typically type    5#1T    that is totally odd but 'readable'.    

Good one Jeff!

Marko

[Matt Tarlach]

If you are open to buying a used scope, 20" Classics turn up on the market fairly often. There was one in San Francisco a few months ago. It needed recoating and some fiddling, but was fundamentally sound and in cosmetic condition too - under a layer of dust. It probably won't be long until another pops up within a day's drive - and a "Wanted" ad might get immediate results.

Matt T

[Robert Jardine]

Hi Mark, well, this is not exactly what you are looking for, but maybe it will suit you.

I have one of the world's best telescopes.  Really.

And I'm about ready to sell it (reason: I'm getting old, my eyes aren't so good anymore, and neither is my memory.

The one "mismatch" with this scope is that it is strictly push-to; I don't think it could take any kind of go-to system.

It is possible that you could attach setting circles to it, but I kinda doubt it.

The scope was a very innovative design of Albert Highe -- he is a quite famous telescope designer and builder,

and he is also a Taco.  You may have seen some of his earlier scope designs around -- several Tacos have them;

I have personally owned four of them.

This one is a 20" f/4.  The mirror is excellent.  The outstanding feature (for me) is that a person only 5'9" can easily

and comfortably look through the eyepiece without a ladder. Most 20"  aperture and even 15" scopes require at least 

a one-step ladder.

So, as I say, this scope doesn't exactly fit your criteria. But I thought it might be worth considering.

If you are interested, you could come by and take a look at it.  I live in Cupertino.

On Fri, Oct 15, 2021 at 12:20 PM mtoma...@comcast.net <mtoma...@comcast.net> wrote:

--

[Vishal Kasliwal]

Hi Robert,

       May i ask how much you are planning on selling your scope for? I too am in the market for a large Dob - I was thinking of going to 24", but 20" is also just fine and if Mark isn't keen on yours, i might be.

Best,

Vishal

PS: D idn't we meet at Dinosaur Point once? I think we looked at the Orion Nebula through your scope with my 21mm Ethos.

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[Jamie Dillon, DDK]

Vishal, you're right, I was there when we were looking at M42 in Joe Bob's scope with your eyepiece.

For the record, Jardine isn't kidding, that 20" is a remarkable telescope.

[Les Niles]

5’9”? I’m curious, how do you get a 20” f/4 to give feet-on-the-ground views to someone much shorter than Lew Alcindor?

  -Les

On Oct 22, 2021, at 4:30 PM, Robert Jardine <rlj...@gmail.com> wrote:



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[Jamie Dillon, DDK]

Hey Les. It's an Albert Highe design, that's how.

[John Pierce]

I don't know if this scope does it, but I've seen a few where the diagonal is not 45 degrees, but instead 22 degrees, and the focuser is midway up the truss structure and angled funny.

On Fri, Oct 22, 2021 at 7:03 PM Jamie Dillon, DDK <ngc1...@gmail.com> wrote:

Hey Les. It's an Albert Highe design, that's how.

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[Julien Lecomte]

I remember looking at, and talking to Albert in his garage about one of his scopes that had an angled focuser, i.e. it was pointing slightly downward. Very ingenious! I don’t know whether that is the scope that Joe Bob now owns, but it was quite something! Every single one of Albert’s scopes, including their children and grandchildren (mine might be considered a grandchild of Albert’s) are fantastic and worth a lot of money. You’ll have to pry mine from my cold dead hands :)

- Julien

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[Robert Jardine]

Yep, that's my 'scope. And it is a great one!

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[Robert Jardine]

On Fri, Oct 22, 2021 at 6:48 PM Les Niles <l...@2pi.org> wrote:

5’9”? I’m curious, how do you get a 20” f/4 to give feet-on-the-ground views to someone much shorter than Lew Alcindor?

  -Les

Turns out, it is simple: you can just tilt the angle of the secondary mirror. That's what Albert did. AVAIK, nobody ever thought of that before.

Just do the ray tracing, and you can prove that the image is not altered.   

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[John Pierce]

On Sat, Oct 23, 2021 at 12:49 PM Robert Jardine <rlj...@gmail.com> wrote: 

Turns out, it is simple: you can just tilt the angle of the secondary mirror. That's what Albert did. AVAIK, nobody ever thought of that before.

Just do the ray tracing, and you can prove that the image is not altered.   

I would think optimally, you would want a secondary thats ground at that angle so its still 'circular' as seen from the eyepiece, and the beveled edges are perpendicular with the  primary.   That secondary will also need to be somewhat larger to compensate for the increased distance to the focal plane, at least if you want to fill a low power eyepiece.

 

[mukund....@gmail.com]

Is Albert still making scopes? I've seen some very fine examples of his work and have always been curious. 

[John Pierce]

AFAIK, no, he's no longer able to, and made his last quite awhile ago.

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[Les Niles]

Ah, thanks, that makes sense.  I’ve seen much larger scopes with tilted diagonals, where the eyepiece ends up halfway back toward the primary.  Those take a really big diagonal, and the eyepiece ends up at an awkward angle.  The 20” f/4 wouldn’t need to be nearly so radical.  Nice.

  -Les

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[Robert Jardine]

I have a great 20" Albert High constructed scope that I'm willing to sell.

This is really a innunusual  scope. Good mirror and great, innovative construction.

In order to avoid  using a step-ladder, this scope uses a tilted secondary (that is, not oriented perpendicular to the main tube).

This  design sends the light out of the tube and down on a diagonal.   Much more comfortable than viewing up on a ladder.

It also disassembles nicely to fit in the back of a small SUV or a station-wagon.

Bob Jardine

On Fri, Oct 15, 2021 at 12:20 PM mtoma...@comcast.net <mtoma...@comcast.net> wrote:

--

[Tim Lorz]

Hi Robert,

What would your asking price be for that 20"?

Thanks and clear skies! 

Tim 

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[Jamie Dillon, DDK]

I've looked at a lot of things thru that 20" of Joe Bob's, it's razor sharp with mondo contrast, definitely an Albert Highe scope. A serious telescope.

[Jeff Gortatowsky]

Joe Bob... and the price is right? Contact me.

Jeff Gortatowsky... California

"Religion, together we will find a cure.", R. Dawkins

On Sun, Mar 20, 2022 at 3:55 PM Jamie Dillon, DDK <ngc1...@gmail.com> wrote:

I've looked at a lot of things thru that 20" of Joe Bob's, it's razor sharp with mondo contrast, definitely an Albert Highe scope. A serious telescope.

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[John Pierce]

On Fri, Oct 15, 2021, 12:20 PM mtoma...@comcast.net <mtoma...@comcast.net> wrote:

....

I suppose that I should have attended last week’s Cal-Star event.  In the drone video that one of you posted, I saw several large aperture telescopes constructed similarly to how Obsession used to make its “classic” telescopes (i.e., wooden box-in-box base, robust secondary mirror / focuser assembly)

Cal star spring is April 28th, hasn't happened yet. At least one of those drone videos that has been posted is mine from four or five years ago and right near the launch is an Obsession 20-in classic F5 which belongs to the Santa Cruz astronomy club and is set up as part of my camp next to a white fiberglass trailer and a white f250 long bed with shell.

I totally concur that the obsession classic is a more stable scope than the ultra compacts. It also sets up faster. But it's heavier and takes more room. I used to carry it around in a Tacoma pickup with a fiberglass shell it fits just fine along with a couple of motorcycle ramps to roll it into the truck, but the 7 ft step ladder required for the 20 inch F5 needed a roof rack on the Tacoma because the bed wouldn't hold it. I now carry the whole mess in the F-250 long bed which is more than big enough, but that's about the biggest pickup truck you ever want to drive.

[Jeff Gortatowsky]

The UC's are not very good mechanically as I have documented ad-nauseum on the net. And the service? Non-existent. 

Jeff Gortatowsky... California

"Religion, together we will find a cure.", R. Dawkins

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[ma...@astrospotter.com]

Me thinks we no be seeing Jeff on an endorsement of the UC anytime soon.   ;-)