What 8" Dob to buy ? [Archive]

desler

04-08-2008, 02:03 PM

Hey Mal,

I've never used a sky-watcher Dob, but after owning both the 8 and 12 inch versions of the GSO, I can say that I have found them both fantastic.

Not to say I haven't had the odd problem, mainly the odd screw loose in the finder scope mount or alt axis bearing. Apart from that, I can't complain.

Later when you add various bits and pieces the box tends to flex a bit and the siction type probelms with fine azimuth adjustment appears to be half the fun.

There are pages and pages on everything from Milk bottle washers to total rebuilds. The funny thing is, we all tend to want perfection. Although I'm not 100% sure, any of us knows what perfection really is!!!!

Which ever choice you make, really depends on your circumstances. But which ever way you go, you'll have lots of sleepless night observing.

Darren :)

Fisherman

04-08-2008, 02:58 PM

Hi Darren,

Your my first reply on this website. Many thanks for your input.
I have read a couple of reports on similar scopes and can get a Skywatcher locally.
The GSO will be an interstate buy as I dont think anyone in WA sells them.
I'm also led to beleive the EP's that come with the Skywatcher are a bit ordinary so an upgrade might be on the cards straight away with that one.

The GSO on the other hands sounds more 'inclusive' of the good bits (but I'm really no expert).

Like all purchases its not easy is it ?

Thanks again.

Miaplacidus

04-08-2008, 03:27 PM

Hi Mal, welcome aboard.

I have had both Skywatcher and GSO newtonians. Any of the chinese dobs will be good enough optically. Really comes down to other features on offer now. A crayford focuser is perhaps the most useful addition, if you can get one included. (Try not to get too hung up on eyepieces...) Can get by without a fan on 8 inches, I reckon.

The tension control handles on the Skywatcher I find do make them easier to carry, and work pretty well to easily fix the scope in altitude. But if ever you want to add encoders for digital setting circles it is harder to do, though not impossible.

You'll almost certainly love whichever you get, up until the moment you decide you need more aperture...

Cheers,

Brian.

ving

04-08-2008, 03:37 PM

to be honest i think kyou'll be happy with either :)

i have a gso and they have changed alot since i got mine. optically i cant complain and i got more than i bargained for... some of the old pros will come here and say "how can you say its great, it mass produced rubbish", alas the are comparing to thousands of dollars worth of gear and for the price you will not find better. my 8" is now mounted on an equatorial mount (tripod). and years down the track i still think it rocks!

erick

04-08-2008, 03:50 PM

Sadly you say "new", so it won't be my Bintel (GSO) which I have to sell soon. And you'd have to come to Melbourne to pick it up ;)

I'm very happy with my Bintel 8", especially after I made various tweaks and improvements since I bought it second-hand. I have since bought a Bintel 12" second-hand and am just as happy with that scope. I cannot comment on the Skywatcher - no experience.

While the eyepieces which come bundled will get you started with exciting views, in both cases I expect that you'll be wanting to move up to better eyepieces in a while. What is really useful and not bundled is a good collimation tool - a Cheshire tool is best (but add a laser collimator, if possible). Also useful is a barlow lens - a 2" diameter, 2 times (GSO make one - the ED).

Cheers
Eric :)

Chippy

04-08-2008, 11:50 PM

Hi Mal,

Welcome aboard!!

Not much in it, but personally, I'd go for the GSO if price is similar. They are coming out with new models, so don't know much about these yet, but I'm happy with mine.

AlexN

05-08-2008, 01:29 AM

Im very happy with my skywatcher 8" dob.. Except no matter how much i water it (get dew on it at least...) It will not grow into a 12" :D

Bundled ep's were not horrible, but not fantastic either... if it will be your first look through a real telescope, they will blow you away...

Eric hit the nail on the head... a Cheshire collimation tool is one of those things that should be bundled with newtonian telescopes, but sadly, they are not... a 2x barlow is also very very useful...

Best of luck with which-ever you choose, You'll be impressed either way.

oh, and :welcome: to IIS...

rmcpb

05-08-2008, 09:24 AM

Welcome to IIS Mal.

You have raised the old problem we all face when starting out. As most have said the scopes are pretty equal in quality and it will come down to the extras. A crayford focuser is the biggest improvement you can get at this level, see if you can get a 10:1 model. Some say a right angle finder is better than a straight through one BUT I would only agree if you have ae Telrad or some other device to put you in the right area. You MUST get a Cheshire eyepiece to allow you to collimate the beast otherwise you are waisting valuable photons and resolution. A fan is good but don't stress too much about it if the scope does not have one, its an easy upgrade later.

As for the eyepieces that come with the scope. Relax about them and use the ones supplied for quite a while before getting onto the upgrade path. You can spend lots of money on these and its best to wait till you know what style of eobserving you enjoy most as this will influence the type of eyepiece that you will find best for you and your budget.

Enjoy it as it comes for quite a while, you will love it :)

Fisherman

05-08-2008, 10:44 AM

Morning guys,

I've just come into the office and what a great surprise. Many thanks for the quick replies to my questions. Its really good to get your comments. I only joined up yesterday and you make me feel like part of a 'family' already! Magic.

There were so many interesting and helpful comments there.

I've been using the 'Mk1 eyeball' and cheap binos for a while, but the cheap binos, just don't do it, do they, so reading your comments I figure it's going to be good with either scope on that score.

On the list now:
A Collimation tool - 'Cheshire' eyepiece and/or a laser!
Crayford type focuser.
Barlow lens.
Its beginning to get like fishing tackle already!! :)

Still 'the fifty million dollar question' ..... which brand to go for?

The GSO seems to be ahead a little at the moment and I'm led to believe there's some new models on their way to Aussie. I need to check on that. I've always been a little wary of 'new ones' though??

Would anyone have a link or three to any reviews on either I wonder?

Any more comments would be really welcome so please don't hesitate to post them.

Many thanks again guys.....and yes, clear skys (& good fishing!)

Mal

erick

05-08-2008, 11:00 AM

Reviews? Have a search through here:-

http://www.iceinspace.com.au/index.php?reviews

re Cheshire and/or laser. I reckon you can get away with only a laser, but others say no, definitely have a Cheshire and add a laser if you find it a useful supplement.

UFO

05-08-2008, 01:10 PM

Hi Fisherman,

I am also looking to buy my first telescope and I am also in Perth.
I called andrewscom yesterday and they recommended me to wait for the GSO super deluxe model to arrive. The shipping cost to Perth is around $80-$100. I wonder if they can give us a discount on shipping if we buy one each.
By the way btow is having a Lunar night this Thursday.
http://www.btow.com.au/
You can try the skywatcher then. I really like to go but have other commitment.

Fisherman

05-08-2008, 03:03 PM

Hi Eric,

Many thanks for the advice Eric. The learning curve is sharp but I'm enjoying it immensely. I guess when I finally get my hands on one all will fall into place. Unlike cars you can't stand them side by side and compare them so the knowledge of an experienced stargazer is appreciated.

I used to be into photography many years ago, so the technology does'nt phase me. It's just knowing what's worthwhile and what's sales hype. I guess like many I'm trying to make the right purchase to start with.
"All that glitters ........... " :thumbsup:

Hi Hendi,

I knew there had to be at least one other person out there doing the same...there always is! Thanks for the info re GSO and Andrews. I too have been on their site.
Do you have an email address for them? I could'nt see one so I faxed them a short list of questions last week with no reply?. Maybe they did'nt receive it...who knows. I'm a little surprised that no one here sells GSO but maybe the local market is'nt really there?

Did you get a price and delivery date on the GSO 8" super delux?

I also have spoken to BTOW re 'Skywatcher' and was aware of the Thursday night viewings but this week it looks like I might be tyed up to.
Also without knowing what the GSO looks, feels and performs like I wonder if I could draw a meaningful comparison from looking at one without the other. So far everyone seems to rate both highly, but I detect a leaning towards GSO.

Have you made your mind up for the GSO against a Skywatcher?
If so and I go that way to I would certainly be interested in the possibility of doing a deal on freight etc.

Let me know your thoughts,

All the best ...clear skys ( & good fishing)

Mal

ving

05-08-2008, 03:18 PM

g'day Mal...

tight lines mate! ;)

UFO

05-08-2008, 03:31 PM

Hi Mal,

I most likely will be getting the 8" GSO super deluxe which is $429.
The person that I talked to didn't know when it will arrive. He haven;t seen one but he said the colour will either be white or grey (not that matter to me).
Yes I am interested in saving on shipping cost too if they can give us discount.

Fisherman

05-08-2008, 04:06 PM

Hi Hendi,

Any particular reason you did'nt pick the Skywatcher?

Mal

UFO

05-08-2008, 11:45 PM

Hi Mal,

Basically because the super deluxe GSO has more/better features and eyepieces for the same price as Skywatcher.

FromAndrewscom website:
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!
That's five high quality eyepieces included (not just two or three)!!

I will try to visit btow this Thusrday night to try their Skywatchers.

Fisherman

06-08-2008, 09:43 AM

Hi Hendi,

Yep, I'm thinking that way too. If you do get over to 'BTOW' tomorrow night I hope the weather holds out and the sky presents something to test the beast on.
Other than the obvious mechanical integrity i.e. ease of focus and movement etc I would'nt really know how to test/push the scope optically.
Hopefully you have a few good ideas in that department Hendi.
Be good to have an 'Eric' on the job would'nt it?

Please let me know what your impressions are.....

Clear skys (& good fishing), :thumbsup:

Mal

PCH

06-08-2008, 10:02 AM

Hi Guys,

I agree with Hendi regarding the GSO if it comes with a right angle finder. This was a must for me when I bought mine (Meade LB 12") as the position you have to get into to see thru a straight finder would be most uncomfortable much of the time.

But, as a previous post mentioned, it's best to use the RA finder in conjuntion with a red dot finder or similar. This really works a treat and you can home in on anything in seconds within a very short period of practice time.

Cheers :thumbsup:

Fisherman

07-08-2008, 09:32 AM

Morning chaps,

PCH,

Yep, I can understand the goodness of a RA finder for sure. Thanks for your thoughts on that.

Hendi,

My investigations say that the 'new' 8" GSO's are a while away...maybe late October?

Skywatcher 8" arrival 15 August. I'm told they now have a Pyrex mirror to!

One thing I've come to realise is that buying a scope in WA takes a lot of patience.
If you get there ...good luck tonight,

Mal :thumbsup:

UFO

07-08-2008, 12:04 PM

Hi Mal,

Yes, Andrewscom changed their info on the 8" GSO yesterday.
Now it will be Oct/Nov and the price has gone up from $429 to $499.

It makes Bintel price more attractive ($429).

I actually posted similar question on the day as you so I running 2 threads:doh:
http://www.iceinspace.com.au/forum/showthread.php?t=34608

Do you know what comes with the 8" Skywatcher? 10:1 focuser, right angle finder etc? When I called BTOW they said the 8" is over $500.

hikerbob

07-08-2008, 01:27 PM

I got the older model (non collapsable) 12" Skywatcher from Andrews. Service was great and that was when delivery was free. It's a gem but could be improved on. The straight through finder is a pest and I've swapped the tension handles for some furniture adjusting bolts as I was often knocking the scope off target when looking high in the sky.

At home I use a laser pointer for most of my finding activities (Argo Navis is still a way off yet unless unforseen fortune comes my way). The laser works remarkably well in conjunction with The Sky software.

I've dealt with Bintell on some smaller stuff and have been very impressed with the service, both times I've ordered via the web and had phone calls to confirm that I had the order right (did you really want two of those?).

Once I got settled with the scope I gained the impression that I might have been better served by spending a bit more and getting some of the accessories first up (stuff the GSO has already) but I don't think thats a biggy.

The skywatcher is great for the money and has given me many hours of pleasure. I'm hoping that Skywatcher (or someone else) brings out a retrofit flexitube kit. The idea of being able to shrink a hot water system sized telescope down to drum size for transport is very appealing and feedback so far suggests that the flexitube is rigid enough.

Bob

Fisherman

07-08-2008, 03:28 PM

'Goodaye' Hiker Bob & UFO,

Skywatcher 8" features. I'm told a 10:1 Crayford focuser, a Pyrex mirror (not mentioned in the website?), 9x50 finder scope (straight through!), 25mm and 10mm EP's. $499. No freight charge as in Perth. ( but... they talk badly of the other brand when I know there probably as good. Poor selling...I don't like that.)

I just spoke to a chap at 'Bintel'. re their BT202.
They are a rebadged GSO with full instructions, 10:1 Crayford Focuser, R/A Finderscope, 15mm and 9mm Plossi EP's, and a moon filter and they reckon they do a 'pre delivery check!'
He was full of practical and helpful advise and very plesent to deal with. The freight cost though is $85 unfortunatly but their scope price is very good, as you mentioned UFO.

I'm waiting for a reply to an email from one other retailer?

Thanks for the info Bob, all very interesting :)

Getting close now ............very close :thumbsup:

(Good fishing)

Mal

dannat

07-08-2008, 04:02 PM

Mal, i personally think if you are starting out there is something tobesaid for buying local - just in case you need advice
Also getting a don shipped isn't cheap & can add up.

RE the ep's he gso might have more and be slightly better but just about all ill upgrade to something better anyway if they continue to observe

i think most place a high emphasis on the focuser, usually crayford with 10:1 fine focus being sought after: i have a regular crayford 1:1 & i get by with focus fine & don't think i will upgrade - seeing as how they both have 10:1 i would personally prefer local

PCH

07-08-2008, 04:40 PM

Yeah, - but BTOW will more than match on price if you tell him you've got a better price elsewhere. He's keen to do business wherever possible like all of them. :thumbsup:

UFO

07-08-2008, 05:00 PM

Hi Mal,

I also called Bintel this morning and he gave me the same freight cost $85 which pretty good for a big item 4000kms away. He also said it includes insurance.
They also check and laser collimate it before shipping.

Taken into account freight cost for Bintel they are basically the same price.

Another option is to ask Andrescom if they can supply the 8" GSO with RA find and 10:1 fine focus but I think the price will be pretty similar.

I wonder if anyone here has tried or own both GSO and Bintel. It would be great to have their opinion as to which one we should go for.
I personally wouldn't think we will need too many advise from the sellers except when buying it. We have enough people on this forum that can help us.

A couple more questions:
According to what I can find here pyrex is not that important for 8" reflector? Perhaps someone can clarify?

Plossl Eyepiece is better than no Plossl? Is this so? Why is it?

Who are the guys http://www.telescopeshop.com.au/Dobsonian_Telescopes/Skywatcher_Dobsonians/
They are in Myaree.

wavelandscott

07-08-2008, 06:37 PM

The Bintel and the GSO come from the same manufacturer (GSO)...I do not know if they use the same QA/QC standards or not but assume that they do.

As near as I can tell, the difference is that Bintel take each GSO scope out of the box, inspect/collimate it and put a Bintel sticker on it in their store...(I may be missing a few steps) but they do add value by checking things out before the box gets shipped to you...so at least when it leaves the store you know that there is/was a working scope inside.

How much value you place on that is up to you to decide. Additionally they are knowledgable and as mentioned earlier helpful with advice (they helped teach me to collimate my scope at their shop before I left for home with my first scope). That is not to say other shops aren't helpful too...but I have dealt with them and experienced their helpfulness on many occassions.

For an 8 inch scope used in Australia the Pyrex/not Pyrex debate is probably a bit much...either way the mirror mass needs to get to/near ambient temperature for the "best" views...as the temperature drops at night either will require time to catch up. That is why the high end astro-photo folks using reflectors often invest in active cooling systems. I've found a fan is enough for my own uses.

Are the co-efficient of expansion/contraction (or whatever it is called) different between the two materials, yes I am sure that they are. Is one better than the other...on a big mirror maybe, but I'm not sure I'm sufficiently skilled to notice the difference on an 8 inch mirror. Either will need sufficient time to cool...depending on where they are stored and what the temperature difference is (storage to ambient) this is likely to take more than 15 minutes in either case.

Plossl is an eyepiece design...there are many other design types. The plossl design can and does come from different manufacturers...each with their own set of QA/QC systems... The best design may be dependent on the scope you intend to use it and the purpose you have in mind. People can and do write books comparing/contrasting the advantage and disadvantages of the different eyepiece designs. Again that debate often gets above my needs. In general terms, a plossl is a pretty good all around eyepiece design that when matched with appropriate QA/QC at the manufacturer level are often good work horse eyepeices...

My two cents...Clear Skies,

erick

07-08-2008, 08:38 PM

My experience of the plossl design is that once you get down to 10mm focal length or lower, the eye relief becomes a very small distance and you'll have your eyeball pushed very close to the eyepiece. 15mm and above are fine - I love my 20mm Televue plossl. So for these shorter focal lengths, it's worth comparing other designs, eg. the Vixen LV, the various non-plossl Televue, the Pentax and lots of others.

UFO

08-08-2008, 12:09 PM

Thanks guys for the info.

Mal,
I went to the lunar night. The place (car park) was pretty bright.
They only have the 10" Dob and it was good.
The price that he quoted you for the 8" does not include 10:1 fine focus.
The next 8" stocks will arrive on the 15/08 as you mentioned.

Personally I find that telrad will be of a very good help for a beginner like myself. Even aiming at the moon is not that easy:shrug:
Also I find the telescope movement is not as smooth as I thought it would be. But I probably will learn to make small movement easy enough.
I think a right angle finder will be more comfortable to use.

erick

08-08-2008, 12:31 PM

They are relatively cheap scopes with most money in the optics, not in the mount. But fairly straightforward to improve the movement for the average home handyperson.

Fisherman

08-08-2008, 02:46 PM

Hi UFO,

I think from what I hearing, telescopes are like many other products being sold these days, especially comparatively low priced imported ones. There are a lot of variables from model to model and it's buyer beware for sure !

I did beleive the Crayford focuser on the Skywatcher 8" was a 10:1?
I'm sure I was told that.

It's does seem a little surprising that a new telescope is possibly required to be modified to operate in an efficient way, when by its very design purpose this surely would have been part of the design requirements.

I guess you get what you pay for though. I would'nt be suprised if they were all (same models) a little bit different in that regard to.
Friction can vary with temperature.
The 10" would be heavier than the 8" maybe making it a little stiffer?
Is the base bigger to compensate for the extra weight ...I wonder?

To quote Eric "to improve them is fairly straighforward" ......but after spending $500 do you want to?

The million dollar question is, will the GSO be any better in that regard?

I'm hoping to get over there this weekend to have a look.

Many thanks to all for throwing in there thoughts on this one to....

Have a good weekend,

Clear Skys... (Good fishing)

Mal :thumbsup:

bmitchell82

08-08-2008, 06:50 PM

Like it was said before, yes that is the million dollar question but look at it this way, it has only been in relitively recent times that ameture astronomers like ourselfs have been spoiled for decent size apperatures for decent prices. now if your where to get a 8" Newt on a decent GEM or Alt/Az your price jumps about 1500 ish maby less maby more add in good GO TO electrics.... you get what im saying.

So i look at it this way, get the best optical setup i can afford (re 10") if it sits on a milk crate and then i have to actually use my head and build something so it works ... so be it. The thing is that the main parts that i cannot build (have no idea) i can buy, anybody can go to bunnings and buy 50 bucks worth of tools and 100 bucks of materials to hitch up a mount... and should i mention the added enjoyment of saying to your family friends... I did this...

To emphisise my point further, i have taken part in the EWB challange recently, and their main point was everything must have a price value attached. eg... If you brought something out of the box that worked first time every time, would you value it as much as something that you have had to work for? or was added for free would you appriciate it as much as if you had to put it there.??

Thats my 2 bobs worth.... but on the upside, i get to play with curtin universitys gear! read Mead 200LXR 12" with SBIG Cam Laptops Series 5000 eyepeices a 40mm Hand grenade.! :D ahhh to have a institution willing to part with $$$...

Fisherman

12-08-2008, 10:17 AM

Hi Brendan,

yep... I understand what your saying and it can be good for many reasons to modify gear to suit.

In this case the decision is simple. It's one or the other.

There both value on the optics front.

Sounds like your spoilt rotton with the Mead 12" and all the fruit ;)

Its great to get so many educated opinions on the subject through the website. I've learnt alot.

UFO....didnt get to BTOW's at the weekend. His business hours are quite restrictive for me. He must be doing really well to only open when he does.
I might open a telescope business in WA :lol:

How are you going?

Mal (Good fishing) :thumbsup:

UFO

13-08-2008, 12:29 PM

Hi Mal,

Yes, they close on Monday and Tuesday too.
I am still not sure. Maybe I'll wait for the new GSO 8" but I might change my mind in the meantime.:whistle:

Fisherman

14-08-2008, 12:49 PM

Hi UFO,

I had a look at the 10" Skywatcher yesterday.
Looks a good, solid scope.
The Crayford focuser on that one is'nt standard is it (Bintell!).
It has a vernier knob adjustment which was explained as "really unnessasary".

The other extra was a 'laser red dot finder'. Which apparently makes life a lot easier finding objects in the sky. Another $80 or so . Yep...can live without one I'm told but ...................

I liked the general solid feel to it though and the adjustable altitude control looks good.

Being unable to look at a GSO with spring /friction control makes me wonder how good that could be ?.

Is there anyone out there that's got one of these and can tell me whats it performs like?

The turntable movement considering the weight I thought was'nt bad either.
So I'm told it can be improved on with a little work.

I wonder how good the GSO is on that count ?

Anyway, the 8" Skywatcher's should be in Sydney now and here by Tuesday.
I think they will be here when their here! ;)

They 'may' also have R/A finders but won't know until they arrive and seen.
Imagine dealing with a supplier and your not sure whats going to arrive? 'LOL'

I will hang fire till I see the 8" Skywatcher.

Mal :thumbsup:

UFO

14-08-2008, 07:15 PM

Hi Mal,
I was also told the same thing about the 10:1 fine focuser.
To be honest I probably can survive without one.
If you are still thinking about the 10" maybe you want to consider the collapsible skywatcher from andrewscom.

hikerbob

14-08-2008, 10:11 PM

Mal, I've used red dot finders and they can be good but a laser pointer is a lot better.

I've not used one but a lot of people seem to rave about Telrads as a finding device. They seem to be in the mid $70's (plus postage). From what I've read a better option than a red dot finder but I'm not speaking from personal experience. On the other hand what people really rave about (again I've not used one but have seen them in action) is the Argo Navis - unfortunately somewhat more money.

Cheers
Bob

Fisherman

15-08-2008, 10:02 AM

Hi guys,

I managed to get a look through an 8" Skywatcher Dob, a Mead Casegrain and a Skywatcher refractor last night. The conditions were'nt perfect as there was lots of stray light around.
The moon was like a 100 watt light bulb against the many 5 watters making it even harder!
It was interesting to say the least...and the moons craters very large and clear.

It was'nt a competition but other than it's inability to track the planets automatically the Dob won hands down for me.....

Beautifully simple, very clear optics and value for money, just about sums it up for a beginner like me.

The standard Crayford focuser, although not perfect, worked well enough. The EP's being used were not the standard ones but not super expensive ones either.

Bob, I saw a Telrad on one of the scopes. The owner was happy with it and I cought see the red sighting circles even near the moon. (just!)
The standard finders cross hairs were difficult to see against the night sky. I wonder if that could be modified?
Also without an R/A on the finder you had to be a contortionist to go to high altitudes. My back hurts!

UFO ...I will be happy with an 8".

So all in all, it was a very interesting hour .......

Mal :thumbsup:

erick

15-08-2008, 11:04 AM

8" dob preferred - Yes!

Once you've used a 10:1 Crayford, you won't go back to standard - try to get one with whatever you buy.

Telrad or simpler red dot finder (last can be as cheap as $39) - both a form of "unit finder" or "1x finder" - both very useful items - Telrad is more sophisticated - susceptible to dew without some shielding.

Straight through finderscope - "my back hurts!" Welcome to the club! Yes, there are ways of providing some illumination of the crosshairs - usually involves add a dew shield to the front of the finderscope and illuminating the inside with a red led or two, thereby making the view of the sky a little lighter, against which the crosshairs become visible.

Right angle finderscope - yes, very good, but strongly recommend it is used in conjunction with a unit finder so you get into the right part of the sky before you look into the finderscope. There is a way of directing the straight through (by keeping both eyes open - one of the sky and one on the view through the finderscope). This cannot be done with a right-angle.

(Using a laser pointer is great, I do, but (1) laser law adherence and care needed wrt planes etc., (2) astrophotographers will come and hit you with bricks at a star party for ruining their image, and (3) dead batteries and you are lost, finderscopes always work.)

Happy purchasing!
Eric :)

NeilW

15-08-2008, 11:39 AM

Hi all,

Do you know just what the "adjustable tension" on Andrew's new GSOs is or does, and is it useful?

Thanks

Neil :)

PCH

15-08-2008, 02:48 PM

Hi Neil,

most brands of dobs have some way of implementing this. All it means is you can adjust the 'slackness' of a) the declination angle of the ota, and b) the effort needed to push the scope around in a circle on it's mount.

As an example, the more things you install at the focuser such as heavier eyepieces or a binoviewer (these are terrific :D), you'll need to tighten up the declination setting a bit, or the focuser end of your new toy will just hit the deck - :P. So yes it is very usefull !!

Hope this helps :thumbsup:

NeilW

15-08-2008, 03:13 PM

Thanks Paul, that's very helpful, and it's convinced me to wait a couple of months until Andrews get that model in...:thumbsup:

UFO

15-08-2008, 03:15 PM

So it is nothing new. Even the old model has one?
I thought it had something to do with reflector adjustment.

And if you like to add red dot finder (designed for paintball rifles):
http://www.dealextreme.com/products.dx/category.910
http://www.dealextreme.com/products.dx/category.914

Fisherman

15-08-2008, 04:11 PM

Hi Guys,

Many thanks for all the info and 'the good oil' Eric.

Re The tube vertical and horizontal friction adjustment.

To my knowledge :

The 'GSO' has a spring either side of the tube that pulls it down and against some friction material thus stopping it flopping over...' all very techinical' but I guess it must work! (I beleive they've sold hundreds of them.)

Can someone varify this or have I missed somthing?

The new model (on its way!) has adjustable tension handles to acheive this.

The 'Skywatcher' uses two rotating handles, one either side of it tube mount to adjust this tension. Works well enough...I've tried it.

I can't understand why all of them were'nt designed like this in the first place !

Have a great weekend all -

Tomorrow is good day for fishing,

Mal :thumbsup:

erick

15-08-2008, 06:00 PM

Mal, the GSO has two plastic trunions either side as the altitude bearings. They are a relatively smooth plastic. When in place, each sits on two small pieces of teflon, fixed to the base, against which they (and therefore the whole tube unit) can rotate so the tube moves in the altitude direction.

The two springs just pull the plastic and teflon harder together, thereby increasing the friction to try and stop an unbalanced tube unit (due to heavy eyepiece) from moving under its top-heavy weight - or vice-versa if a really light eyepiece.

One note, don't leave the finderscope off - its weight is expected to be found there in the design.

Fisherman

19-08-2008, 09:27 AM

Hi Erick,

But does it work or is it like so many things we purchase these days, ends up being modified to work as it really should have done in the first place?

A while ago I worked in the wholesale market place. Products we sold came and went. Quite a few times the model before the latest, the one we just sold out of or the one that was lasts years colour and no one now wanted was so much better than the new, you beaut 'priced right' one! When the market place realised that and the retailer stopped selling them we all looked forward to the next 'improved' one with the 'extra bits and pieces' Maybe, just maybe, they might forget how good that old model was and stop comparing !! :lol:

Mate, I dont want to get off the subject so tell me what you really think of that mechanism?

Mal :thumbsup:

erick

19-08-2008, 10:01 AM

In that case Mal, you'd better buy an SDM or an Obsession. :)

I've had my hands on one or two GSO dobsonians of some age and possibly not great maintenance, and they were a horrible movement to my touch, particularly Az - far too much "stiction". Probably dust and muck got into the base. I move a new one in the showroom and it feels guite good. (But operation out in the cold/wet can be quite different to warm/dry of indoors.)

I preferred to improve mine. I'm a tinkerer. No problem for me that I take something I bought and make it better - I regularly do that. I like getting improved performance out of something I bought for a mediocre price by using a little bit if ingenuity, effort and a few parts.

Fisherman

19-08-2008, 11:16 AM

Hi Erick,

thanks for the reply.

As yet I dont know anything about those two scopes but I guess they're probably the 'Roll Royces' on the market and priced acordingly.

I don't mind tinkering myself. It's good fun but at times I've modified things to the extent that I should have really bought the 'other one' in the first place even though it was maybe 20% more expensive.

Mal :thumbsup:

erick

19-08-2008, 11:32 AM

Yes, SDM - ballpark AUD7,700 for a 15"; Obsession - ballpark USD3295 for a 12.5" (plus shipping). That's what one would pay for very good quality movement in a dob - "off the shelf". That's a big difference compared with the Chinese 12" and 16" dobsonian scopes.

Fisherman

19-08-2008, 03:08 PM

Hi Erick,

I thought they would be pricey.
What about floating the base on a 'bath of mercury'. :)
Sounds weird I know, but I saw this on an antique many moons ago.
(I also beleive the stuffs poisonous so dont lick your fingers !) and where would you get it ?

I'll be happy with a Chinese one !

Mal :thumbsup:

Brian W

19-08-2008, 10:56 PM

Being the very happy owner of a Meade 8" LightBridge I humbly suggest taking a look at one. Nothing against the others but why limit yourself to two options?
Brian

sikfish

20-08-2008, 12:16 AM

Howdy,

I tried to get the 8" Skywatcher from BTOW who kept telling me it was coming and never did (after me chasing them up a number of times). Also the price they eventually offered was not compeditive. I ended up buying from York and it arrived in a week for $399 delivered and I am very happy. I think the whole thing about buying local is good - but only if the locals get their act together! Anyway just my opinion, it seems we need some competition here in WA.

Mike