Question regarding 10" Dobs

FrostyXIII · #1 21-03-2008, 03:46 PM

Hi everyone,

OK, so I have been floating around these forums lately and asking as many questions as possible regarding the purchase of my main telescope.

I was looking at the Skywatcher ED80 with astrophotography in mind, but then realised that a good mount will cost more than the telescope itself.

Seeing as my budget is $700 to $800, this isn't going to be enough to get into astrophotography.

I figure that I might as well get bang for my buck. So I'm leaning towards a 10" Dob. I don't want an 8" because I used to have one about 2 years ago and sold it due to work commitments.

Anyway, www.andrewscom.com.au website seems to have some good deals with regards to the following, Guan Sheng 10" Dob:

Deluxe Crayford version
Super, super low price!
$449.00 AUD

Guan Sheng GS-880 10"
250mm x 1250mm
Super Deluxe version
Super low price!
$549.00 AUD

Deluxe version includes a right-angle correct image 8 x 50 finderscope, a 2" Crayford style focuser with a 2" to 1.25"adaptor, fan and GSO 9mm and 25mm 1.25" Plossl eyepieces.

Super Deluxe version includes a right-angle correct image 8 x 50 finderscope, 2" Crayford style microfocuser with 10:1 fine focusing and a 2" to 1.25" adaptor, fan, GSO 6mm, 9mm, 15mm and 25mm 1.25" Plossl eyepieces - and a bonus SP32mm 2" eyepiece, too!
So my questions is, which one would you buy? I am assuming most people will say the Super Deluxe version for the fact it has the 10:1 fine focusing?

Obviously there are other 10 " Dobs for sale but seem to be more expensive than this one and don't offer all the extra EP's. E.g. The SW-880 DOB 10"254mm x 1200mm Now $549.00

Is it worth buying one of the other Dobs with a well known brand name or will this one do? Does anyone know if there is any difference with optics etc...?

If there is gonna be a difference in optics with the Skywatcher 10" dob I would rather pay a bit more and go for that.

Also the fact that I am not spending the full $800 just on the scope, means I can afford to by extra accessories. Can anyone recommend any extras I should purchase, that may make life easier while observing? Maybe a better finderscope or certain 2" EP's etc...

Any help is appreciated.

Thanks in advance

Frosty

madtuna (Steve) · #2 21-03-2008, 03:51 PM

From what I understand Frosty (someone please correct me) I think they are pretty much all out of the same factory and just rebadged.
If there is any difference it would only be minor

A mate recently bought the 10" from Andrews and I was so impressed I'm getting the 12"

Kokatha man · #3 21-03-2008, 04:28 PM

Quote:

Originally Posted by madtuna

From what I understand Frosty (someone please correct me) I think they are pretty much all out of the same factory and just rebadged.
If there is any difference it would only be minor

A mate recently bought the 10" from Andrews and I was so impressed I'm getting the 12"

No corrections MT, they're all much of a muchness - in fact, mucher still, being all the same: the only diff I've noticed with some of these "badgings" is that sometimes some of the little bits like finder scope "feet" are slightly tighter or looser by what could be the paint thickness - a SW F/S won't fit in a GSO base or vice versa sometimes: certainly the Andrews cheaper versions are exactly the same as the others.

Solanum · #4 21-03-2008, 04:59 PM

Actually, the Skywatcher ones aren't the same as the GSO/Bintel ones. They probably are slightly better in terms of the mount mechanics and I think the mirror is pyrex (?). However, I doubt that the quality of the mirror shape is any better and I think they only come with a straight through finder by default.

Being as I bought the 10" deluxe GSO dob from Andrews just over a year ago here are my comments in no particular order:

1) The right-angle finder is good (easier to use than straight through).

2) Get the 10:1 Crayford, it makes accurate focussing much easier.

3) The 6 mm plossl has such a small eye lens and so little eye relief that it is almost useless. The surface of your eye has to be almost touching the lens. Seeing is rarely good enough for 6mm with these scope anyway. 8-9 mm eyepieces will get a lot more use.

4) Check the telescope and accessories carefully, some of the saving with GSO comes from less than perfect quality control (though nothing wrong with the quality of the set-up if you get what I mean). In my case there was glue across the mirror from the centre spot and the coatings on the 15mm plossl was faulty making it unusable.

5) Get a Telrad or similar and use it in conjunction with the finder. It will save you a lot of time when you are trying to find stuff.

6) Get a collimation tool. A combination Cheshire/sight tube will suffice, but make sure the sight tube is of adequate length - the basic Andrews model isn't. Better still a barlowed laser collimator will give you potentially more accurate collimation.

7) The biggest 2" eyepiece you should get is about 32 mm. Larger than that and you'll get vignetting.

8) I'd only bother with a cheap GSO Barlow if you are going to get minimal (hopefully better quality) eyepieces and want to Barlow the smaller one (12-15 mm) for high magnification.

9) If you can save enough money by getting the minimum number of eyepieces to buy a couple of better ones, then do. For longer focal lengths the Televue Plossls are much better than the GSO ones and only $115 from Bintel. At shorter focal lengths the 'ED2' ones are nicer to use, but probably not better quality than the GSO Plossls. Vixen LV's are good and not too expensive ($175).

10) Coloured filters are a waste of time and money. A polarising/variable polarising filter for the moon is a necessity.

11) Use the fan, all the time. Get a decent sized SLA battery and connect that to it so you don't have to waste money on AA batteries.

Solanum · #5 21-03-2008, 05:01 PM

Oh, and 12) a 10" dob is great, it's just light enough to carry around the garden (though you'll want a hand cart to move it more than a few yards), you can see an amazing amount with it, and it won't break the bank.

FrostyXIII · #6 21-03-2008, 05:03 PM

Sounds good to me. Anyone got any ideas about any extra accessories I should purchase?

Is there certain EP's that would work great with a 10" Dob?

What kind of EP's would you go for if you had a 10" Dob and wanted to look at DSO's and planets.

Frosty

FrostyXIII · #7 21-03-2008, 05:12 PM

I posted without seeing some replies.

Thanks for ur feedback guys

Solanum · #8 21-03-2008, 05:15 PM

Frosty, see above for accessories. Here's more comments on eyepieces.

As far as eyepieces go, you have the choice of several cheap eyepieces from 6-30 mm, or a couple of better eyepieces, say 12-15 and 20-25 together with a barlow. I personally prefer not using a Barlow, but if you can get better eyepieces by having fewer and using one, then do so.

A 2" 30-32mm eyepiece is nice for the "wow my head is in the stars" feel, and for finding faint things. But not much use for actually looking at stuff.

An 8 mm is more probably useful than a 6, but you'll want to get to about 6 (either with a 6 mm or barlowed 12mm eyepiece) for planetary viewing those nights of good seeing.

I use my 2nd hand 20mm TV Plossl more than any other eyepiece because I can see more detail in it than I can in my 14mm ED2 or dodgy 15mm GSO Plossl due to it's quality.

If I could have my time again: get the deluxe with 9 and 25 mm GSO Plossls, but see if they'll upgrade the focusser to 10:1 for less than the $100 difference in price then get a new/2nd hand Televue 15mm plossl. You will also want either a good 6 mm eyepice for those good nights I mentioned, or a 2x Barlow. If you can get a better one than the GSO one e.g. Orion shorty, TV Big Barlow etc. I would.

Finally, there is now no end to the accessories/eyepieces you can get, nor the money needed to buy them. I have certainly only scratched the surface myself....

Kokatha man · #9 21-03-2008, 07:26 PM

Quote:

Originally Posted by Solanum

Actually, the Skywatcher ones aren't the same as the GSO/Bintel ones. They probably are slightly better in terms of the mount mechanics and I think the mirror is pyrex (?). However, I doubt that the quality of the mirror shape is any better and I think they only come with a straight through finder by default.

.

Hi again all - I think you'll find that there really is no difference whatsoever between GSO and Skywatcher other than what I commented below. Both use BK7 glass (borosilicate) which is a good quality lens/mirror material.

Andrews do make the claim that their GSO 's are figured to 1/12 wave accuracy, although Don at Bintel has said that Bintel don't make that claim for their GSO's because this may not be substantiated.

I own instruments of both badging and as I said, almost identical with most accessories, and I would be skeptical about one having any appreciably difference re quality control superiority over the other; or other claims to being "better."

That said, the Andrews 10" are the cheapest scopes around, especially if they're still offering free freight.

As for ep's, I believe barlows are a valuable addition to your ep armoury to extend your magnification range: my ep selection is for multiple instrument useage but suits the GSO 10" dob very well - the core useage ones being a 26mm GSO 2" "widey" that is more than adequate for low power wide field "gazing" and Vixen LVW 17mm and Nagler T6 11mm's complimented by a TeleVue 2x barlow. These are "top-flight" ep's but you could do just (almost) as well by getting Baader Hyperions and an ED barlow to have a good power range - others will have far more experiential knowledge of these alternatives.

I'd agree with most of Solanum's recommendations except to say that for me (and many others) the combo sight tube/chesire collimator is the way to go - but I'm not going to be drawn into any arguements there; you'll find plenty of them in the IIS threads....!

Cheers, Darryl.

Solanum · #10 21-03-2008, 08:18 PM

I wasn't sure about the pyrex, but they aren't the same scope. Skywatcher dobs are made by Synta in China, not GSO in Taiwan. The mount is different (has adjustable tension on the alt), and in the ad in the current AS&T they come with a straight through finder as standard, not right-angle.

I agree that there is unlikely to be any significant optical differences though.

By the way, my Astro Systems barlowed laser collimator isn't an ordinary laser collimator used with a barlow (does that make any sense?!). I would agree that a Cheshire sight/tube is fine and a standard laser can only do part of the collimation that a Cheshire can do. Just make sure the sight tube is long enough to focus on the cross hairs, which the Andrews one I bought isn't.

dannat (Daniel) · #11 21-03-2008, 08:52 PM

Frosty - sorry to throw another spanner at you - but have you checked the freight cost from syd - melb. Because bintel has their 10" on sale for 599 at the moment with the 10:1 others have suggested but you are unsure about - in fact I suggest you go in and talk to roger about it. You can look at the scopes there and then decide. (they are in burke rd camberwell)
One other point - I suggest it does not matter how many cheap ep's you get in the deal, sooner or later (sooner if you look thru someone else's) you will want to upgrade ocular's(ep) anyway
have fun - deciding

dannat (Daniel) · #12 21-03-2008, 08:55 PM

Frosty - on second thoughts why don't you buy the 10" dob in the classifieds at the moment - it looks better than the average dob, and is slightly cheaper

Kokatha man · #13 21-03-2008, 08:55 PM

No argument on different manufacturing bases Solanum - but it seems to me that there's still a moot point as to whether any of these places actually make (discernably) different gear: it's like the tooling and everything is allmost identical except for the guy that sticks the name tag on at the end of the line!

I changed my other scope (SW) over to a RACI (GSO) finder and found that it fit the mount "shoe" fine: but the SW f/scope holder wouldn't be accepted by the GSO shoe and the original GSO scope's f/scope and holder was too loose in the SW shoe.....??!!??

Who knows what machinations go on in these companies; they make scopes etc for Meade et al and I'm sure there's international/political/financial considerations/connections as well as the obvious "cloning" practices of industry.

Yes, I know that you have a barlowed laser collimator which is appreciably different from a laser collimator - as I said I'm not going to be drawn into any this versus that device stuff; suffice to say that I get excellent results from my device, and the only thing I would possibly add to it is a Cats-eye unit.

As for the Andrews chesire, I gave that to erick and he seems to think it's great: I won't describe what I thought of it!

With the Orion combo tool I possess, there seems to be some sort of expectation that the sight-tube cross-hairs will come into sharp focus as seen visually (not the reflection) - this is really rarely true and some (like Erick) find this incredibly disconcerting - however it is of absolutely zip/zero/ nada consequence with regards to achieving excellent collimation!

Cheers, Darryl.

Kokatha man · #14 21-03-2008, 08:59 PM

Excellent advice dannat - ignore our waffling and check out the "tweaked" one, or see Roger at Bintels!

FrostyXIII · #15 22-03-2008, 03:22 AM

Hi guys,

Thanks for all the info, it is making the decision a whole lot easier. I think I'll go into the Bintel store and take a look at the scopes myself and then decide. I was going to go to a few stores around melbourne but Bintel seem to have good prices etc.

Thanks again!

Frosty

CoombellKid · #16 22-03-2008, 05:32 AM

Quote:

Originally Posted by Solanum

1) The right-angle finder is good (easier to use than straight through).

I dont entirely agree with your statement. A RA finder is a damn pain to use
by itself for the purpose of star hoping on a dob, unless you also have a telrad.
A straight through finder although harder on the neck is alot easier and quicker
when using the two eyed approach. Which is kinda like having a telrad on
one eye and a straight through finder on the other at the same time without
having to chop and change. I guess this is in the end subjective to the user.

I have terrible neck problems... but I still prefer a straight through finder.

regards,CS

Kokatha man · #17 22-03-2008, 12:36 PM

Quote:

Originally Posted by CoombellKid

I dont entirely agree with your statement. A RA finder is a damn pain to use
by itself for the purpose of star hoping on a dob, unless you also have a telrad.
A straight through finder although harder on the neck is alot easier and quicker
when using the two eyed approach. Which is kinda like having a telrad on
one eye and a straight through finder on the other at the same time without
having to chop and change. I guess this is in the end subjective to the user.

I have terrible neck problems... but I still prefer a straight through finder.

regards,CS

I allways keep both eyes open - reckon it's the best way (for me) to view; and I've a straight through finder and a Telrad (next to it) on my dob; but can't work out how I could use (say) my left eye for scoping the finder and my right for the Telrad.

Maybe when Matt Lovell delivers my Telrad "riser" I could put this on the left side of the finder and achieve this: problem is my focusser's there! And I find the finder allmost superfluous for star-hopping; much prefer a very low power, wide field ep in the scope and just use that and the Telrad.

Anyways, as stated, personal preference is the final arbiter with everyone.

Cheers, Darryl. (ps - haven't got it yet, but I'm sure the "riser" will be a real benefit - they come in various heights and many people don't know they exist.)

Solanum · #18 22-03-2008, 02:35 PM

Quote:

Originally Posted by CoombellKid

I dont entirely agree with your statement. A RA finder is a damn pain to use
by itself for the purpose of star hoping on a dob, unless you also have a telrad.
A straight through finder although harder on the neck is alot easier and quicker
when using the two eyed approach. Which is kinda like having a telrad on
one eye and a straight through finder on the other at the same time without
having to chop and change. I guess this is in the end subjective to the user.

I have terrible neck problems... but I still prefer a straight through finder.

regards,CS

Well, as a beginner myself, I find the right angle easier because, 1) I don't have to get down on the floor to look through it and 2) the image is the right way up.

Everyone has their own preference and I guess these may well change as one gets more experienced too.

Solanum · #19 22-03-2008, 02:37 PM

Heh, I think this thread has taught Frosty one thing, there is never a "correct" answer in astronomy!

ausastronomer (John Bambury) · #20 22-03-2008, 04:22 PM

Quote:

Originally Posted by CoombellKid

I dont entirely agree with your statement. A RA finder is a damn pain to use
by itself for the purpose of star hoping on a dob, unless you also have a telrad.
A straight through finder although harder on the neck is alot easier and quicker
when using the two eyed approach. Which is kinda like having a telrad on
one eye and a straight through finder on the other at the same time without
having to chop and change. I guess this is in the end subjective to the user.

I have terrible neck problems... but I still prefer a straight through finder.

regards,CS

I agree 100% here with Rob's comments. On a smaller type dob which you use standing or sitting only, without a Telrad fitted, a straight through finder is the best option. The reason being you can sight along the axis of the finder with one eye, which you cannot do with a RACI. On my 18" Obsession, which needs small steps, I find a TELRAD/RACI combo works best as the eyepiece on a straight through finder gets into awkward positions from the step stool.

BTW, the quality of the GSO Optics are at least as good if not better than the Synta (Skywatcher) Optics.

Cheers,
John B