Image of the day

Captured by
Robert Gendler


My Account

New to Astromart?

Register an account...

Need Help?

Which Dob would YOU get?

Started by lintonius, 03/15/2005 06:41PM
Posted 03/15/2005 06:41PM | Edited 03/15/2005 06:42PM Opening Post
Gentleman, (and ladies),
I am thinking about adding another Dob to my arsenal. I've only been observing for a year and a half, but I took to it like a fish to water (or perhaps like a bird to the sky grin ) I started with an 8" LX-90, but recently added a 12.5" Dob (old Discovery primary) in my quest to gather more DSO light. I love the 12.5", but here's my dilemma:
I've had the opportunity to view through an 18" Obsession a couple times and I've come to the conclusion that it would be my ultimate scope (realistically speaking). Not too big, but big enough. And not too hard to set up and/or transport.
Enter Floyd and his 14.5" Starmaster. wink Now I'm considering getting one of these instead based on the reputation of the Zambuto mirror. What do you think? Will I still be craving the 18" aperture? Or will the Zambuto factor make up the difference? :S
Your opinions are appreciated.
Posted 03/15/2005 06:49PM #1

I have a 16" Starmaster w/Zambuto primary and it is a fabulous scope. That said, for your question, a great 14.5" scope under very good seeing will not outperform a great 18" dob. If you were comparing similar apertures, I would say go with ZOC. This is not because other guys can't make mirrors as good as Carl, but because I have never heard of anyone getting a ZOC mirror that was not superb. However, even if a 14.5" mirror were perfect, it would not outperform a darn good 18" mirror. In reality, the 18" Obsession would probably have a great mirror.

Do consider how much you are willing to transport and setup, though. I love my 16", but it is the most I would want to handle alone.


Randy Roy
Posted 03/15/2005 06:52PM #2
hmm, the old aperture jump question again . . .

I vote for 18" or even 20". The jump from 12.5" to 14.5" will be real but subtle to the eye.

Might I suggest a 24" F4.3 Starmaster? Now there's a big hunk-o-glass, and you only need a 4-step utility ladder to use with it.

Yep, or maybe one of those 28" F3.8 Starstructures being made . . . and use the SAME ladder. Nice!

Food for thought!

Posted 03/15/2005 07:48PM #3
Hi Linton,
As I said before in private, the 18" will outperform the 14.5" almost always. A 24" would outperform an 18" in almost any situation.
Aperture always rules as long as the optics are of good quality. Yes, there are those that say that a smaller scope will perform better under certain atmospheric conditions.
But, aperture also means size, weight and height. This means that you must have a larger vehicle to transport it and that you will have to lift heavier components for assembly. This may require you to have help for assembly and disassembly. It also will mean that you may have to use a ladder to view.
You must think about these things and be sure that this is what you are willing to do. If you find that it is too much, be aware that you will likely loose money when you sell it. Note the ads for the larger scopes and the prices for them almost new! It really can be a costly mistake.
If you really want a larger scope. Then I suggest that you ask your friend let you assemble the scope and put it away after a full night's viewing. This will allow you to experience everything about using the scope. It is always harder to put it away than to put it together! 8)
I love to look through a large scope. It is very satisfying and a pleasure. But I have tried to put together a 20" by myself and was not able to do it without straining my back. This is the reason for my owning the 14.5". If I could handle an 18" I would probably own one.
Hope you find what you are looking for in the end.
I keep hearing past conversations with people about aperture fever and climbing up and then finally done the ladder until you find your comfort zone. This is reality and you see it all the time. No one in our club takes out there scopes over 16" with and frequency. I have only seen one of the two 17.5" scopes in the last three years and it only two time. The 20.3" scope has been out maybe 3-4 times in these three years. Even the 16" is many times not there and is being left at home for a 14.5" scope that he owns.
Not trying to make any waves or cause any argument, just trying to show both sides of the story. wink

[SIZE="Large"][/SIZE][COLOR="Blue"][/COLOR] Floyd Blue grin
Amateur Imager
Posted 03/15/2005 08:41PM #4
Howdy Howl! grin
Absolutely! Your opinion does not need to be "what I want to hear" to be appreciated. I want to hear differing points of view, in order to help me make my own best-informed decision. Yes-men need not apply. wink
I have heard many "aperture retrograde" stories already. That 20" story is sad. Maybe you should have tried their 18". It IS the most popular Obsession. If you want to give it a try, I promise to buy it in 6 months for $3,000 less. Sorry, just kidding.
Thank you for your input.
Posted 03/16/2005 09:19AM #5
Hi, Linton,
Here are some random thoughts:
A lot depends on your age and physical strength and fitnees.
Michelle Stone, of Plettstone Telescopes, moved from an 18 to a 15 because she says you can see almost as much and it is much easier to handle.
On the other hand, the diehard members of TAC, The Astronomy Connection, seem to favor 18 inch scopes, but they are people who observe at 9000 feet in midwinter, they are real enthusiasts. But some of them do have socpes in the 14 to 15 inch range.
A Johnsonian popup 18 inch would be very much lighter than any other model.
The 16 inch Starmaster is the largest SM makes that does not require a ladder, even at zenith.
The 14.5 inch SM is a hybrid design, somewhat faater to put together than most truss scopes.
You rarely find a 14.5 inch SM owner sellling because it is too large. You often find larger scopes for sale becasue they are too large.
The mirror box on the SM is slighter larger than the one on the Obs, but the SM permits you to remove the mirror easily and carry it separtely. Since the mirror is the heaviset part of the scope, this is a big advantage.
Your comment that a 12 is in the enighborhood of an 8 (which most people would disagree with), leads me to believe you have aperture fever very seriously and want a really large scope.
. Nevertheless I would lean toward a 14.5 or 15, or a Johnsonian 18, unless your are young, strong and fit and energetic.
Of course you can put the socpe on wheels and roll it in and out of your garage, regardless of sixe, but trnsporting it to dark sky sites is another matter.
Good luck with your decision.
Bill Meyers
Posted 03/16/2005 04:37PM #6

Hi Linton,

I agree with what everyone is telling you except for one thing. To say a 14.5" scope will show you almost as much as a 18" just isn't true. Maybe if you have bad eyesight or are not very experienced. To me there is a big difference. I would say try before you buy.
Posted 03/16/2005 04:54PM | Edited 03/16/2005 04:55PM #7
I'm retrograding.....had a 14.5 Obsession and a bit of aperature fever, bought a 16" Nightsky, well built, beautiful, flawless motions and optics. I'm now ordering a different structure to shave around 30 pounds of weight and 5-6 inches off the heigth at zenith. It seems as I grow older and time is more important, ease of use, convenience and safety have hit me. A 16" with the right structure could give 14.5" portability and weight, the same EP heigth at zenith and the aperature you crave. Not to start a flame war, but my mirror is a Pegasus from John Hall, I'd place it close to the Zambuto or Royce.
My 2 cents. Good luck, you are fortunate to be in a nice position to have to make this difficult decision.
PS!!!!This means viewing on the ground....flatfooted if you are 5'9" or more!!!!!!!!!!
Posted 03/17/2005 12:02AM #8

I've owned a lot of dobs from 6" to 18". I've had the 6" the longest, and will always have one. Its perfect for carrying outside for those quick observing fixes. But when I go to a dark site, I invest the time to set up the 18". I also really enjoy a 12-1/2" scope, especially my ultralight.

With a 12-1/2" scope, you won't run out of observing targets in your lifetime. Larger scopes will provide an even longer list of objects you'll never see. Showpiece objects are marginally better.

If you don't get out to a truly dark site almost every New Moon, you probably are kidding yourself. Keep what you have and don't buy anything else. But if you are serious about getting out often to remote dark skies, then consider buying a larger scope.

If you didn't already own a scope, or are planning to sell the 12-1/2", I'd recommend buying the largest you can easily transport and use. Don't underestimate the importance of size and weight. Astromart ads contain a lot of larger scopes that were too much a challenge for their owners.

Despite the Zambutto optics, consider that Starmaster scopes are larger and heavier than others of the same aperture. Don't be fooled by the Zambutto hype. Carl's mirrors are good, but so are those of plenty of other manufacuturers who charge far less money. You won't see a difference.

But, if want to keep the scopes you have, I recommend the next step up be the square root of 2 times the diameter (e.g. from 12-1/2" to 18"). Any smaller step doesn't provide enough difference.

I wouldn't agonize over the decision. If you get a good deal on Astromart, you'll probably get your money back when you sell. The danger lies in paying new price for the wrong scope. Buy used, try for a while, and sell what you don't find useful.

Posted 03/17/2005 09:28AM #9

Good optics are great, but for faint fuzzies, nothing replaces aperture. If you can afford the 18" and can move it from place to place, get the 18" Starmaster. It is an amazing piece of equipment and the optics are stunning.
I've had the privilege of using one here in Ottawa a few times and if I could afford it, I wouldn't hesitate.

Clear skies,

Jean Dorais
Ottawa, ON