Skywatcher vs bintel vs guan sheng newtonians

[Amaranthus (Barry)]

The Skywatcher now arguably has a (slightly) better focuser. It is a linear power focusser and is lower profile than the GSO one. However, the GSO astrograph includes a mirror fan, and costs less. So it's a toss up.

[knightrider]

I'm looking at a second scope ATM.

I have a 10" Synta which is good, but I am considering a 6" dobsonian as a grab and go.

Are there quality differences between the gso and synta models of this size?

I do believe the synta ones don't put pyrex glass in the 6". And none of the 6" models include a 10:1 focuser...

Anything I should be looking out for?

[Satchmo]

Originally Posted by mental4astro

Looking at the same object, at the same time, the image in the Skywatcher has significantly LESS scatter than the GSO. Black is black, not 'fuzzy grey'.

Alex my 2c - surface ripple causes a very near field scatter to a star image so less ripple might give the impression of sharper star image . Whilst it is a highly technical field ,there is no optical physics around that can attribute a darker sky background to a 'smoother' mirror say between an optically rough mirror of 1/20 RMS ripple at the few mm scale and one of 1/100 RMS ripple. That is nonsense peddled by Zambuto et al . Background sky brightness is acutely sensitive to exit pupil also - it needs to be matched perfectly for a good test and of course the same eyepiece used .

I would guess the improvement in sharpness is down to a better smoother figure , and the better sky contrast is down to better quality coatings that are packed down a lot tighter for less scatter . If you don't believe that al coatings scatter light and lower sky contrast try this test . Grab a large diagonal and compare the sky contrast between looking through a binocular, then get the same view but putting a diagonal at 45 degree in the path in front of the objective. The difference will be tangible.

[mental4astro (Alexander)]

Originally Posted by knightrider

I'm looking at a second scope ATM.

I have a 10" Synta which is good, but I am considering a 6" dobsonian as a grab and go.

Are there quality differences between the gso and synta models of this size?

I do believe the synta ones don't put pyrex glass in the 6". And none of the 6" models include a 10:1 focuser...

Anything I should be looking out for?

When building a scope, mass production or custom, there comes a point where producing a scope costs exactly the same, be it a 4" or 10". In the end, to cut costs it becomes a function of components & care in assembly. At f/8, primary mirror is likely to be spherical as these are cheaper to fabricate. As you've noticed, the 6" has a simple single speed focuser. It also may only have rubber I-rings instead of springs in the primary mirror cell - you'll never be able to properly collimate the scope if this is the case. You NEED to check this out before you make a purchase. At this year's IIS Astro Camp one participant's brand new 6" dob had O-rings, not springs. We also couldn't get the secondary mirror 100% collimated as the spider was placed too high above the focuser. We fixed up their scope as best we could, and the image quality improved markedly - but not to what it should be.

You get what you pay for.

Mark, I didn't think of coating quality also being a factor. Thanks for that

[knightrider]

Originally Posted by mental4astro

When building a scope, mass production or custom, there comes a point where producing a scope costs exactly the same, be it a 4" or 10". In the end, to cut costs it becomes a function of components & care in assembly. At f/8, primary mirror is likely to be spherical as these are cheaper to fabricate. As you've noticed, the 6" has a simple single speed focuser. It also may only have rubber I-rings instead of springs in the primary mirror cell - you'll never be able to properly collimate the scope if this is the case. You NEED to check this out before you make a purchase. At this year's IIS Astro Camp one participant's brand new 6" dob had O-rings, not springs. We also couldn't get the secondary mirror 100% collimated as the spider was placed too high above the focuser. We fixed up their scope as best we could, and the image quality improved markedly - but not to what it should be.

You get what you pay for.

Mark, I didn't think of coating quality also being a factor. Thanks for that

Thanks for your input Alex, it was very informative as I wasn't aware of the lack of springs. How though would I go about checking for springs? Is it just a case of looking at the back of the mirror cell? I can check them that way on my current dob.

Other things I've noted by looking at the information on the sales sites is that the Skywatcher/Saxon/Synta models offer 2"/1.25" focuser and tension control handles for the Alt....whereas the GSO model doesn't seem to offer any of this.

[inertia8 (Australia)]

Correct, it would appear that Synta has upgraded their 6" to include the improvements made to 8" and above models, whereas GSO is still showing the spring tension and 1.25" crayford focuser

[Steffen]

GSO Dobs haven't had spring Alt tensioners for many (5+) years. They have the best and smoothest Alt tension adjustment mechanism of all current mass-produced Dobs. They also allow for rebalancing of the tube, in case you use heavy accessories at either end.

Cheers
Steffen.

[glend (Glen)]

Just to add further to Steffen's remarks, the GSO Alt bearng are real steel roller bearing assemblies and very smooth and the resistance is easily controlled by the large knurlled nobs. I have disassembed them in he past to add encoders, which is not hard to do, and can vouche for the quality. The tube balance slider is graduated to insure bilateral accuracy and is easy to adjust but the tube has to be out of the base to do so. Some people like to bag GSO scopes, (but never their owners) as but they are the best value performers in the market and mirror qualiity is outstandng - for their price.

[knightrider]

Lots of good points here. From what I can see (not what I've experienced, because I haven't seen one of this size in person) the 6" GSO retains the alt tension spring and doesn't have the balance slider...? Please correct me if I'm wrong.

The synta's focuser although 2"/1.25" is rack and pinion, not crayford....EDIT: I'm not sure if this is true now, I've read from another site it is a crayford...?
I'm certain that the quality of the mirrors of both of these in 6" would be more than adequate for visual use.

[Steffen]

Originally Posted by knightrider

From what I can see (not what I've experienced, because I haven't seen one of this size in person) the 6" GSO retains the alt tension spring and doesn't have the balance slider...?

Good point. TBH, I didn't think the 6" GSO Dob was still made. I thought Lee Andrews hasn't had them on his website for a while, but it seems he does. Also, I see that Bintel have them on their site, and the picture shows the old Alt bearing. Maybe it's old stock?

Cheers
Steffen.

[knightrider]

Originally Posted by Steffen

Good point. TBH, I didn't think the 6" GSO Dob was still made. I thought Lee Andrews hasn't had them on his website for a while, but it seems he does. Also, I see that Bintel have them on their site, and the picture shows the old Alt bearing. Maybe it's old stock?

Cheers
Steffen.

Perhaps. I noticed they're no longer listed on the GS site also. Bintel & Andrews still have them, although the image on Andrews looks more like an 8" used to depict the 6".

I've made a correction on my other post. I've seen on Astro Pete's the Synta 6" does use a Crayford focuser, whereas I've read on another it's a rack & pinion. I'm not sure what to believe.

I have access to inspect a Synta at an Aus Geo store, but unable to inspect a GSO model personally. I suppose an email to the supplier would go a long way to answer some questions.

[jak001]

First post here

I’m looking into getting an 8” dob as a starting point. I’ve been reading over the past few days about which brand to get, but I’m still confused.

What I understand so far;
Synta (Skywatcher + Saxon) have better OTA construction but a worse focuser and base

GSO has worse OTA construction but better focuser, base and collimation knobs.

Points of confusion;
Is the differences in OTA construction between the two brands just splitting hairs, or is it something that a beginner would realistically notice?

Are the flaws in GSO’s OTA fixable by tinkering like outlined in this article http://www.iceinspace.com.au/63-206-0-0-1-0.html (from 2005) or are they more fundamental flaws in resent years?

[barx1963 (Malcolm)]

Hi Jak
Both brands are generally OK. GSO have really improved their product in recent years with an excellent focuser and the collimation system is much better with knobs which don't need tools and I believe heavier duty springs.
From what I have seen the Skywatcher focusers can be a little confusing as they have separate adaptors for 2" and 1.25" which often causes confusion.
Most people find that the differences are minimal, either brand will serve as an excellent introduction to visual astronomy.

Cheers

Malcolm

[glend (Glen)]

There is nothing wrong with GSO OTA construction. Keep in mind that everything is built to a price point and in general you get what you pay for, until you get to the point where your just spending money on a brand name or exclusivity. GSO scopes are excellent value for money but do not have the Televue mystic.

[jak001]

cool, thanks for help guys