Looking for feedback: Guan Sheng GS-980 12" Newtonian Dobsonian

[Deimos]

Hi all,

I'm looking at purchasing a Guan Sheng GS-980 12" Newtonian Dobsonian (http://www.gs-telescope.com/refl.asp?sort=3) from Andrews Communications (http://andrewscom.com.au/site-content-section-10-guansheng.htm) in Sydney (I'm based in Brisbane). I'm leaning towards the Deluxe-Crayford edition due to the 2" focuser and the cooling fan on the primary mirror.

I tried e-mailing Andrews with questions about them Friday morning but didn't got a response - either they are very busy or their e-mail's broken.

I've seen that there have been two favourable (http://www.iceinspace.com.au/index.php?id=41,272,0,0,1,0) reviews (http://www.iceinspace.com.au/index.php?id=41,273,0,0,1,0) of the smaller GS-880 10" units, but haven't seen any discussion about their larger 12" brethren.

Has anyone here got any feedback, good or bad, regarding these 12" units? (First-hand knowledge only, please!)

I'm wanting to use this for astrophotography, hence the 2" focuser - my current Newtonian has a 1.25" focuser which occludes a large portion of the photo frame on my Konica Minolta. I'm aware of drift issues, which is why I've lined-up a wood butcher, err carpenter friend, to make a two-sector equatorial mount (http://home.wanadoo.nl/jhm.vangastel/Astronomy/Poncet/) for me (I'm doing the electronics, though).

Thanks and kind regards,
Deimos.

[Deimos]

Oops, that was the Dutch version. Here is the English version of the two-sector equatorial mount (http://home.wanadoo.nl/jhm.vangastel/Astronomy/Poncet/e_index.htm)! :doh:

[mickoking]

G,day Deimos,

I own a 300mm (12") gso Dob with all the goodies. It is a fantastic unit, but I use mine for purely visual work.

[ballaratdragons]

Hi Deimos,

I am the owner of a GS 12" Dobbie from Andrews Communications. I have owned mine for about 16 months. It gets regular use.

The Scope: The scope itself is very good value, and the quality of the optics is suprisingly good for the price. The Tube assembly is remarkably well made with no ill-fitting components. The tube is able to take decent knocks without leaving any marks. The support rings at each end are very solid and prevent the Tube going out of round.

The Altitude bearings, although made of plastic, are very functional and work well. The supplied Crayford Focuser is very good quality and glides like silk. The supplied GS finderscope is a decent size with clear cross-hairs, and a solid, easily interchangeable bracket. The bracket mount is able to take many accessory finders as it has a standard guage dovetail (GS, Orion, Saxon, etc).

The secondary mirror holder (also plastic) is very well designed and simple to adjust. The Spider vanes are fully adjustable in every direction and are nice and thin, and have good mountings.

The Primary Mirror is mounted in a well made Cell with easy adjustment for collimation. Some GS models don't leave much of a gap between the cell and the mirror to help the cooling fan do its job, but the 12" has a larger gap than the others, assisting in taking advantage of the fan to blow cool air onto the mirror back.

The quality of the paint on each scope seems to differ. Many have complained about their GS tubes rusting. Whereas mine gets wet (and iced up) on almost every occasion and yet it has no rust anywhere.

The tension springs work well, but I have found them easier to use (and to prevent busted knuckles) by turning them upside down.

The Rocker box is reasonable quality but can suffer from moisture. It is made of chipboard but does have a good quality finish to it, and is easily assembled. The Azimuth Bearings work smoothly, but often the centre bolt can be a hassle until adjusted correctly.

Weight-wise the 12" can be a fairly heavy beast depending on how far you have to carry it. I find mine OK to carry around, but many people use a trolley to make the job even easier.

The fan is a great addition as it assists in faster cooling of the mirror. I also use mine when the mirrors start to fog. The air circulating blows the dew out of the tube.

There are many alterations that can be done to improve the action and ease of use of these GS scopes, and they are covered in many places in this site.

Observing: On first impression you cannot help going 'WOW!'
The extra light gathered by the 12" is amazing after using smaller scopes. At low power, Galaxies seem to jump into the eyepiece (at a dark site).

Nebulas are clearly seen and Orion Nebula shows Green & Pink colour. Wide-angle starfields seem to go on forever resloving faint stars not normally in the FOV of smaller scopes.

At higher powers the 12" shows great detail in almost all objects.

Mounting: it is also possible to mount the 12" onto other mounts but this can be a very expensive exercise if you cannot build your own EQ or fork mount. The expense is due to the shear weight and size of the 12". It is heavy for an EQ mount, plus add the weight needed in the counterweights and it certainly adds up. I was fortunate to be given an old EQ mount built to carry up to a 16" scope. I restored the mount and added motors. I notice you say you are building a mount. Make sure you over-build it!

Another alternative is a tracking platform.

Transport: Definately something to think about when considering a solid tube telescope of this size. Many cars cannot accomodate the size of the 12" if you intend to have passengers. There are ways to get it to fit into most cars, but it can be a very tight squeeze. Mine fits into my Ford sedan but I cannot fit a passenger when I do. The tube just fits across the back seat and the base on the front seat, or alternatively I lay the front seat down and lay it front to back and place the base on the other side of the back seat. Again- no passengers!

On Delivery: When mine arrived at my door it was very well packed with 2 solid cardboard boxes and Styrofoam inserts to prevent damage. When unpacked there was no damage to any parts.

Overall: I am personally very pleased with my GS 12" Deluxe Dobbie. I enjoy the large light gathering capacity, the smoothness of the Crayford Focuser, the quality of the overall product and the ease of collimation.

It is not a research grade instrument, but for the price it exceeds expectations.

I hope this has helped. :thumbsup:

Below: These pics show the bulk of the 12"

Pic 1. The size of the 12" on its Dob mount.

Pic 2. The size of it up on a large EQ mount. (my daughter is 5'4" tall for comparison)

[ballaratdragons]

As for Astrophotography using the GS12" have a look at the work from Paul Mayo (PhotonCollector) at his site here: http://www.skylab.com.au/pmsa/

[davidpretorius]

fully concur with Ken!!

I have a dob driven GSo 10" and have been very very happy with the jupiter images i have got at very high mags (1600x)

BUT, if I had my time again, I would get the same as Kens.

I do not find Kens to be way too big, it is still transportable and the eyeball views on galaxies etc blow my 10" away.

If you can move it, then get it. Go the extras ie fans, 2" crayford etc.

I believe my next scope will be the 16" light bridge which will get a fairly heavy mod done to it for tracking with a dob driver II.

If you are into DSO astrophotography, the eq platform will be fine for short exposure, but as Ken has put a link to, you will need a heavy duty eq mount for longer stuff like Paul Mayo

[janoskiss]

I don't think the mirror in mine is brilliant, but certainly very usable: a lot of light gathering power, and much more detail on planets than the 8" is capable of.

Star test is far from textbook though, and at powers much over 200x bright stars do not focus to a clean disk. I have just been checking it out in good seeing at high altitude (well high for Oz at 1400m). Another example of this scope I have seen (Barb & David's) seems to have a better figured mirror.

So I think you can expect a bit of variability in quality of the optics with these scopes. But we are talking about a big 12" mirror for around $600! You cannot expect it to perform like hand-figured ones costing several $1000.

FWIW, I would not consider using this scope for astrophotography. But as you can see from Ken's post, where there is a will ...

[iceman]

It all depends what you mount it on. Paul Mayo uses it VERY successfully!

[Wombat_In_Space]

I cant add much more to what Ken has said about the 12" I have had mine for 14 months it was bought from Andrews as well, I have had no signs of rust in the tube I took the Delux option as well.

My scope has traveled a lot of Km since getting it 2 Snake Valley astro camps and lots of weekends up at Kens place in the dark sky, it takes me about 5 mins to collimate when I get it out of the car or trailer.

As Ken said it is a big scope to carry, the OTA comes in just under 25Kg.

[Deimos]

Thanks for your feedback mickoking, ballaratdragons, davidpretorius, janoskiss, iceman and Wombat_In_Space.

Transporting the OTA shouldn't be too much of a problem - getting around in a Tarago I can fold down the back seats and the passenger-side middle seat giving me a 2,100x500x800 space to put things in and still have three passengers.

The photos on Paul Mayo's site are most impressive, especially for an EOS 300D. Gives me something to aim for ... especially since the EOS 400D has just been released. :)

I'll try the EQ platform mentioned originally, but what's involved in making your own EQ mount besides 100kg of steel?

[Deimos]

Well, I hadn't heard anything back from Andrews in the e-mail by 10:30 today (impaient, aren't I?) so I gave them a ring and waded through the questions I had.

I've got one on the way now and it should be arriving at work Tuesday or Wednesday. Freight charge sucked a little - $90.00! Ouch!

Spent the rest of my day hassling my boss with "is it here yet?" on a regular basis (if you knew my boss you'd sympathize with us - he's bouncy enough before he gets on a sugar high), but luckily for him (and me) some other toys I'd ordered arrived to satiate me - night blades for my RC helicopter!

Thanks again everyone for your feedback. It made my decision a lot easier.

[janoskiss]

Deimos, I am not sure you appreciate what a great big beast of a scope a 12" Dob is if you think $90 freight charge is too high...

[Deimos]

Nah, I've seen a couple of Celestrons in the flesh so I've got a fair idea. After reading in one of the GS-880 reviews that it took nearly two weeks for theirs to turn up (the other was only two days) I didn't expect it to be coming up so quickly.

$90.00 is definitely a fair price. It's just that initial "woah" when you consider that's 10% of the unit cost. :)

[Deimos]

Well, I got a call from reception this morning to say a package had arrived for me there. "Yippee!" I thought, "it's here!"

Though it's a start, it was only an Express Post parcel from Andrews that contained a GSO 8x50mm Correct-Image Right Angle finder scope, a pair of Andrews 10x25 fully coated binoculars and what I'm assuming to be a 1.25" Moon Filter (unlabelled).

I'm eagerly awaiting the remainder. I suspect I'm going to become suddenly sick and have to go home when they arrive! :lol:

[Deimos]

Woot! The scope arrived yesterday afternoon, but I stayed at work until "normal" home time. With a pair of big boxes [photo 1,2] sitting behind me a number of people were prompted to come ask questions. :) I was surprised to find a few had telescopes at home as well.

The OTA box had some serious damage with bits and pieces dinged, torn or missing [photo 3]. Whilst the OTA tube and primary mirror survived unscathed, the spider vanes were bent awfully [photo 4] due to the weight of the secondary mirror assembly dragging them down after a (really heavy) knock. The vanes were even bent "around the bend" where they attach to the secondary mirror assembly with rivets. After pulling the whole assembly out and spending a while trying to straighten them (they're really soft metal, almost like aluminium) I refit it all and did manage to collimate it OK. Haven't done a star test yet, though (I am reading up on how to do that this morning).

I spent a few hours last night looking at the limited field of view from my unit's balcony and surprising myself with the number of double stars I hadn't noticed before. My Telrad almost instantly found a second home at the business end, too [photo 5]. I'm glad I bought a second base for it when I purchased it!

I'm eagerly awaiting this Saturday night when I head up to Mount Kent Observatory (http://maps.google.com/maps?f=q&hl=en&q=-27%C2%B0+47%27+52.00%22,+%2B151%C2% B0+51%27+19.00%22+%28Mount+Kent+Obs ervatory%29&z=16&t=h) near Toowoomba for the AAQ field night (http://www.aaq.org.au/field.htm)! :)

If anyone's interested, I also took a bunch of pictures as I was unpacking and scanned the double-sided instruction sheet as well.

Have fun, everyone!

[davidpretorius]

bugga about the delivery knocks, make sure the supplier knows that it arrived badly!

nice piece of equipment!!!

[Deimos]

It's a really nice scope, I'm really happy with it. I drove it down to a friend's place at Thorneside tonight (down by the bay and away from most of the lights). Surprisingly it fits across the back seat (with about 20mm to spare). We spent the evening looking at star clusters and such with many wows all round! :)

Yes, the shipping problems were unfortunate. I got a response from the supplier tonight and they'll be passing the issue along to Guan Sheng.

[mickoking]

Welcome to the 300 Dob club :thumbsup: your going to have a ball with it, deep sky thrills.

Congrats on your purchase.

[rogercrespo]

Hello everyone,

nice to hear that you have a 12" GSO! I'm happy with mine!
I live in Portugal(europe).

Here you can see mine with some modifications(setting circles, 5 fans, power supply and wheels):

17396


Here you can see how i transport it:

17399


Good luck on yours!


Roger

[dcnicholls]

I bought a GSO 12" back in 2003 before they added the Crayford focuser and the fan. I wrote up an article about it for the CAS "Southern Cross", but as the subject of GSO 12's comes up from time to time, I though it might be useful to make it available in PDF form in case anyone was interested.

In particular it describes how I modified the azimuth mount to improve it over the old vinyl clad chip board it used to come with. My first experiment was to sadwich the roller bearing between two laminex disks, then I replaced the bearing with a conventional Ebony Star and Teflon bearing.

In December 2003 I sent a copy of the article to Lee Andrews, who sent it to Jim Sheng, and I was quite amused to see subsequent GSO scopes come with two steel disks sandwiching the roller bearing. No royalties paid, alas :(

The Ebony Star and Teflon bearing is a better (smoother) bearing than the steel disks and roller bearing that current GSO (and Lightbridge) scopes come with.

And the fan is definitely a very important addition if you have one of the older pre-fan scopes - you can mount a DSE PC fan on the GSO mirror cell with strong rubber bands and it works well.

The PDF? For the moment it's at http://www.dcnicholls.com/misc/gso300.pdf

DN
Canberra