Advice on new big Dob purchase

[JoeBlow (Joe)]

Hello,

I was wondering if anyone can give me advice for my next telescope purchase. Currently I have a 12" GSO dob which has served me for the past 7 years.

Recently my family acquired some land in rural NSW. It's blessed with the darkest skies that I have personally seen. To make the most of it I have decided in the near future to purchase a new dob with the largest aperture that I can handle/afford.

I've set the following strict criteria:

- 16" or greater diameter
- Total cost (incl shipping, tax, etc) for scope less than $10,000 (preferably much less!)
- Does not require a ladder to reach the eyepiece, however a small step stool is fine.

I would also favor something made from quality durable materials and construction as I expect this scope to last me for many years, maybe decades to come. And prefer that at most only minor modifications required to make it usable. However I totally understand that I wont be getting anything premium with my budget. Portability will not be a problem as the scope will permanently remain on the property.

So far I have considered the following scopes:

- Meade Lightbridge 16" $2200
- GSO 16" $2000
- Discovery 17.5" f/4.1 ~$5000 shipped from USA

Can you recommend any other brands from Australia or overseas?

Initially I was set on either the Lightbridge or the GSO, but I'm having concerns over their quality, especially the long term durability of their parts and mechanics. I also heard they can easily lose collimation during normal movement, particularly the GSO, is this a common problem?

I would prefer a scope that is a bit rugged and possibly last decades without needing to be rebuilt, hence why I'm considering a discovery, they seem much higher quality than Chinese manufactured scopes, though not premium either.

Also would you recommend a solid tube dob, such as the discovery Split-Tube PDHQ, over a truss design? I would believe they are more solid and hold collimation better. Do they have any other advantages/disadvantages over a truss type?

Thanks,

Joe

[glenc (Glen)]

The mirror in my GSO 16" is very good.
The mirror mounting springs are weak.
I suggest you buy a GSO and spend a bit of money improving it.
Springs, shroud, heaters etc

[Suzy]

Hi Joe,
Have you considered SDM?
There's a number of forum members here who own these telescopes and Peter Reed from SDM is also a member here who's extremely helpful to deal with and a great guy. I've bought stuff from him as well.

He makes quality custom built telescopes in the 16"-40" range.

http://www.sdmtelescopes.com.au/about.html

[mental4astro (Alexander)]

Hi Joe,

Regarding some of your questions:

* Holding collimation depends first on the quality of the primary mirror cell - If it is under engineered there'll be flex; if it uses sprins and they are undersized, they won't hold their position; if it is a truss scope and the entire OTA isn't rigid, then there will be flex issues and so collimation problems; if the secondary holder isn't held securely then again there will be issues. Many large mass produced Newtonians, from 10" up, be they solid tube or truss or strut, commonly have weak primary mirror cell springs.

* Where will you be keeping your scope at on the property. Unless these conditions are dry, regardless of the build quality of the scope, it will deteriorate, structurally and optically alike. Keeping it in a shed without any from of protection from big fluctuations in heat, damp, condensation, etc, it just won't last.

* Size is a concern. There are real practical reasons why mass produced big dobs stop at 16" - start going larger and there are both significant structural issues for the scope, are very heavy, and to keep both feet on the ground require very fast mirrors that are very expensive and difficult to make.

Glen has mentioned getting a GSO 16". These are very good quality wise for the money. Yeah, sure you can get a "better" primary, but are you doing research or enjoying the experience. A GSO will throw up a very good image. The other thing you can do is purchase the GSO and have a new scope built with the optics. You won't find cheaper good optics, and the new structure will not only perform better from considered design, but will last longer too. Alas the rocker box on all these mass produced dobs is made from terrible quality particle board that will distort when the poor seals in the melamine starts leaking dew into it.

Is there a difference between a Lightbridge and a GSO 16" - no. Other than some structural differences, optically they are pretty much the same for quality and collimation hold. As with any mass produced scope there will be those samples that are exceptional and those that are poor. But on a whole they are just as good as the other. Oh, and the rocker box of the Lightbridge is made of the same stuff as the GSO's are.


# A new player is coming soon onto the Australian market for custom built scopes. They will be offering ultra light dobs from 10" to 20", using materials such as carbon fibre for the poles and primary mirror cell components, that are totally Australian built and original in design. I can't say more than this right now, but keep and ear to the ground...

[Deeno]

Have a look at the 14" Orion.
http://www.bintel.com.au/Telescopes/...6/catmenu.aspx

Better build quality than the GSO or lightbridge.

I too am looking to upgrade to maybe a 16".

[Rodstar (Rod)]

Hi Joe,

To pick up on Suzy's comment, I have been absolutely delighted with my 20" SDM scope. I have enjoyed using it for over 6 years, it is everything I could have ever hoped for, and continues to perform flawlessly. I would never look back now at a lower grade telescope.

There are numerous observers who are very happy with the lower quality scopes you mention in your list, but like most things (unfortunately), you get what you pay for.

Alexander raises a good issue regarding size/portability. Fortunately, the SDM scopes are built with a wheelbarrow design, so you can leave the scope fully set up in storage, and wheel it into position in 20 seconds, no fuss. Much easier than the 10" LX200 I used to battle with! Obviously transporting such a scope offsite involves some logistics, but such issues are easily overcome. I have a trailer for the parts, and the mirror box snugly fits into the boot of my car (Honda Odyssey).

As for storage, mine has happily lived in my backyard garage all these years without any issues.

An SDM scope would be a little over your budget, unless you were to pick up one second hand. Occasionally they come up for sale - if so, you could do a lot worse.

Perhaps before you make such a major purchase you should have a look at (and through) the options. If you go to any major star party on the Eastern seaboard of Australia, you will have the chance to observe through any of the scopes discussed in this thread.

Good luck with whatever you choose.

[glend (Glen)]

Having recently researched scopes for my purchase I kept hearing that the Lightbridge and GSO were identical optically, and GSO supplies both their mirrors. If this is so then there is nothing between them. Given that there are local suppliers that hold GSO stock in the size you want, at a very reasonable price, you will save money by picking something that doesn't involve being priced on the new exchange rate and has already landed here (ie shiping cost savings). Andrews Communications prices are very good for what you get and then you can go from there. There are also improvements to the Andrews supplied GSOs in this latest shipment, including much larger and easier to use Altitude adjustment knobs, and the right angle finderscope.

As far as the ability to hold collimation is concerned, replacing the springs with the ones from Bob's Knobs seems to take care that.

As to base construction, I don't see this as a big issue because the base is easily upgraded when required. Is this scope going to sit in an observatory? If so the base may not be an issues for many years. Its not hard to simply use the base components as patterns for building a quality base of marine ply or even strip laminate. You can also buy base kits from the US from places like the Dob Stuff Shop

http://www.dobstuff.com/index.htm

that seem pretty nice. I'd tend go agree with the advice below to buy good optics, and the GSO is very good for most amateur visual observation for it's price, and upgrade other bits as required. Put the money you save towards the observatory and other accessories.

Typical upgrades your going to need would be, a leveling base, setting circles, inclinometre, etc. even if you stay with 'Push to' operation.

Finally, in my limited experience I find that the best investment bang for your $ is to get very good eyepieces which make a big difference in observation quality.

I will be waiting for news on the Australian built ultra -light 20" Dobs.

[The Mekon (John Briggs)]

Joe,

I reckon you need to keep the FL at 2000mm or less.
Hence 16"f5, 18"f4.5 or 20"f4. I chose 18"f4.5 and it is a perfect fit of portability and aperture. It will even wheel through the back door of my garage! At this FL the average person only needs a milk crate to reach the eyepiece when scope at the zenith.

[JoeBlow (Joe)]

Thanks to everyone for your replies! They have been helpful.

I have had a look at SDM telescopes, they look awesome and undoubtedly premium class scopes. But unfortunately even a 16" would be above my budget. The new Australian ultra lights sound very interesting, but I'm assuming they too are premium scopes with a premium price.

I only wish there existed some dob telescope makes that are one or two steps above in quality over the mass Chinese produced scopes, while being a lot more affordable compared to a premium class telescope make. There doesn't seem to be much middle ground.

Originally Posted by mental4astro

Hi Joe,
* Where will you be keeping your scope at on the property. Unless these conditions are dry, regardless of the build quality of the scope, it will deteriorate, structurally and optically alike. Keeping it in a shed without any from of protection from big fluctuations in heat, damp, condensation, etc, it just won't last.

I plan to keep it in a shed. For protection I was thinking of insulating the shed and fully covering the scope when not in use. Would this be enough protection?

Have a look at the 14" Orion.
http://www.bintel.com.au/Telescopes/...6/catmenu.aspx

Better build quality than the GSO or lightbridge.

The Orion looks good. If they had a 16" version it would have been at the top of my list at the moment. But a 14" is not much of an upgrade over a 12".

I understand that optically there is no difference between the GSO and Meade, but are there any mechanical reasons to prefer one over the other? If not, I'm prepared to pay an extra $200 for the Lightbridge because I find it looks much cooler than the GSO .

Also have people here had much experience with Discovery Telescopes? I could possibly order a split-tube 17.5" f 4.1 for about $3700 AUD (not incl. shipping & taxes). Are these scopes worth it? A search on the web indicates there will be a very long waiting time, but that's fine with me if it's an above average scope.

In the meantime I will continue with some more research and keep a look out for a second hand quality scope. I'm not in any hurry.

If all else fails, my fall back position will be a 16" Lightbridge or GSO, I admit overall they are not that bad at all. I was just hoping that for a little more money there may have been something a little more special and better quality out there, while less than premium in quality and price.

[Deeno]

Originally Posted by JoeBlow

Thanks to everyone for your replies! They have been helpful.




The Orion looks good. If they had a 16" version it would have been at the top of my list at the moment. But a 14" is not much of an upgrade over a 12".

But, there is!
http://www.telescope.com/Telescopes/...9/p/102659.uts

You would have to talk to the dealers to have one bought in.

Like you I'm thinking about a Lightbridge. With the intension of building a new base and sorting out its colimation and thermal issues.....

[sn1987a (Barry)]

My experience doing just that...

Bought a Lightbridge 16 a few years ago from Bintel. @$3000 at the time
Didn't like the views, never quite focused properly, heavy as f%#! so I...

Bought a Mark Suchting 16 f4.5 mirror for it $3400 roughly (love it, its a great mirror I'll never sell)

Protostar secondary $300 to $400 with shipping
Feathertouch Focuser again $300 to $400
A few other bibs and bobs, springs, shroud, dew heater, weights ect. mostly from scope stuff.

Rebuilt the base using ply, changed it to allow passage through a standard doorway and added wheelbarrow handles.

Just recently added ServoCat Jr and Argo Navis for goto and tracking. @$1800 all up including shipping, customs and GST.

Its now a pretty good scope and now only needs some svelting.

Would I do it again knowing what I do now.....? Nahh!

I'd save a deposit and pay Peter Read at SDM to build one. By the time it was ready you will have saved enough to pay the rest off.

There's a reason you hardly ever see them up for sale second hand. Invest in quality. My 2cents

[atman (Mark)]

There is a Skywatcher 16" goto - I don't know enough to comment on its quality - for about $3700.

But it's on my bucket list for when I upgrade from my 8" dob.

[Marke (Mark)]

If you are just a little handy you can put your own together as I have done in the ATM forum , it's not for everyone but very satisfying and not to painful.

[Blair]

Originally Posted by JoeBlow

Hello,


I've set the following strict criteria:

- Does not require a ladder to reach the eyepiece, however a small step stool is fine.


Joe

This may be totally on the stupid side of the scale but if height is of concern, and you have a farm, why not lower the scope? Dig a nice hole in the ground with concrete walls and floor or whatever and place the dob base in there so the eye piece is lowered by the depth of the in the hole. With even a moderate hole it wouldn't make it impossible to use at lower angles and be close enought to the scope at all times. Just a wild thought.....after a few Saturday beers....

If it dosen't work you have a 'outside telescope time' dunny

[JoeBlow (Joe)]

Originally Posted by atman

There is a Skywatcher 16" goto - I don't know enough to comment on its quality - for about $3700.

But it's on my bucket list for when I upgrade from my 8" dob.

Those thin looking struts on the Skywatcher frighten me a little. Also I've heard it said that truss is more favorable over strut, but don't quote me I'm definitely no expert.

Originally Posted by Marke

If you are just a little handy you can put your own together as I have done in the ATM forum , it's not for everyone but very satisfying and not to painful.

Thought I would think something like that is interesting and satisfying, I don't think I have the skills. I would require a lot of mentoring.

Originally Posted by Blair

This may be totally on the stupid side of the scale but if height is of concern, and you have a farm, why not lower the scope? Dig a nice hole in the ground with concrete walls and floor or whatever and place the dob base in there so the eye piece is lowered by the depth of the in the hole. With even a moderate hole it wouldn't make it impossible to use at lower angles and be close enought to the scope at all times. Just a wild thought.....after a few Saturday beers....

If it dosen't work you have a 'outside telescope time' dunny

lol I have to admit the thought has crossed my mind for a second in the past, then became disappointed when I realised it's not a practical solution haha.

Originally Posted by Deeno

But, there is!
http://www.telescope.com/Telescopes/...9/p/102659.uts

You would have to talk to the dealers to have one bought in.

Looks like it's a new product. I guess Bintel will probably have them within the next year or so. My guess is it will initially retail for about $4000!! Double a GSO!

I wonder if you can get one without all that goto stuff and save a bit of coin? plus I consider it cheating!!! haha , but seriously a big part of the enjoyment of this hobby for me is finding something myself, I compare it very closely to fishing.

[skysurfer]

I have a (modded) 40cm GSO Dobson with a more sturdy and narrower rockerbox (62x62cm) from plywood rather than the original particle board one and stiffer springs in the mirror cell.
I bought this scope second hand in a very good condition.
It has roller bearings (the original as well) which results in a very smooth motion, much better than the Orion XT-10. So keeping an object in the field even at high power (200x) is easy.

[FJA (Faith)]

A few years ago I had a GSO (branded Revelation here in the UK) 12" Dobsonian and found that, while the optics were decent, I had to do a few mods to get it to work as I wanted it to. Chief among those was changing the primary mirror cell springs from the existing, very weak, ones to a heavy duty set, changing the collimation bolts and getting a set of 'Bob's Knobs' for both the primary screws and the secondary ones. All this made collimation much easier and I wasn't having to re-align the mirrors two or three times each session.

I now use an 18" Dob from UK scope maker David Lukehurst, which is excellent in every respect, but - obviously - that's not going to be a practical option for an Aussie. Australia's custom-made SDM scopes look really good and, if your budget stretches to it, go for a premium model like SDM.

[GrahamL]

The kits Marke mentions and there a few available
http://www.astrosystems.biz/telekits.htm
http://astrosky.homestead.com/index.html
http://www.dobstuff.com/
are mostly ready to assemble with a little work, the atm section here is
has quite a lot of helpful builders who stop by to.


Does Peter still have the second 18" primary still on hand?

great value as the cheaper commercial offerings are sooner or later you will have to do some work on them , some of the great mods people launch into are easily no more difficult than assembling a kit scope.

good luck