GSO 6" Imaging Newtonian - f/4, looking for opinions

[SamAndrew]

I've had a search and can't seem to find much written about this scope;

Has anyone got one or used one ? or got any opinions of how good it is ?

I'm thinking of this as an alternative to the SW ED80 for imaging.

Thanks

[ollypenrice]

My opinion is that super fast F ratios are much to be desired - and much to be avoided if you don't want to pay someone an awful lot of money to get the engineering right. There is no free lunch in this game. Those who enjoy tinkering, and are gifted at it, can tickle these cheap fast systems into doing something useful. I wouldn't touch them with a long pole but that's because I like imaging. If I liked adjusting optics I might feel otherwise.

My own alternative to the ED80 would be, and was, pretty expensive. There are nice imaging refractors now that offer alternatives, however.

Olly

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/22435624_WLMPTM#!i=1793644788&k=r8HTK72

[SamAndrew]

Thanks for the thoughts Olly, however I already have an f/4 newt so I'm not too concerned about adjusting the optics.

Epic pictures by the way

Out of interest, your 20" dob can't be much slower than f4 surely ? altho I guess it's not so important for visual use.

I'm basically just trying to make sure this scope isn't a lemon with a crappy focuser or some other massive problem; provided it performs similar to it's bigger brothers it should be good.

Looks like I might be the first one to review this scope judging by the lack of response.

[johnrt]

There are quite a few folks who have the 8" version and have been left quite unimpressed with it out of the box.

But as Olly rightly says, if you're one for adjusting the primary mirror cell, tinkering with flocking, upgrading the focuser etc etc etc then if can be turned in to a good imaging scope.

[Macavity]

I own a Telescope Service 8" / F4 "Photo-newt", which I believe has it's origins with GSO. I suspect I am not the only one. There have been comments on those - A certain amount of controversy too? <G> But the (budget) PRICE was a motivation / necessity, for me. Other variants on a theme exist... by Altair Astro... the Skywatcher Quattro even, each having slightly different features - Extra baffling, different focussers, steel or carbon fibre OTA etc.

Theoretically(!) an F4 scope requires "twice" the collimation accuracy of an F5. And coma becomes greater. But I suspect the "technology" of adjustment is not THAT different from standard, popular F5 Dobsonians. Whether it is equal to the task might be moot. My "inner physicist" winces slightly, but a lot of people use fast(er) F5 Newtonians, as a matter of course.

I have fitted "Bob's knobs" to the secondary, and intend to replace the primary springs(?) at some stage. The TS variety of my 8" has a rather nice TS/GSO "Monorail" focusser. I was sufficiently impressed with these latter to buy the SCT version for a Skywatcher Maksutov - And share a motorised focusser control as my "standard".

My retrospective. An F4 "photonewt" may not be strictly required if, like me, your ambitions are limited to smaller chip (video) astronomy. The extra back-focus is useful (obligatory) for full-frame DSLR use, but may be less so otherwise. I have used a focal reducer with my Watec, to get to F2.8, via the additional in-focus! <G> The size of the secondary is a consideration - Visual use is not totally excluded, but the shadow of the latter limits eyepieces to f>20mm - There is the Coma question...

One could go on? LOL. But these instruments are short and light. For unguided VIDEO work, an HEQ5 has proved adequate. A small (six foot wide) observatory, weight limits - a personal health limitation for me? But "Different strokes" etc.

[SamAndrew]

Interesting, I've been looking into it a bit more closely,

On the TS website, the 6" scope is under the GSO section, but actually described as a TS imaging newt rather than GSO, quote " This telescope will be manufactured from GSO for Teleskop Service."

It comes with the TS monorail focuser instead of the standard crayford fitted to the GSO scopes, so hopefully this is adequate.

I'll see what else I can find about this focuser; Macavity is positive about it so that's a start

[Macavity]

The Monorails are perhaps the best part. But basically a BAR fitted along the drawtube, with "double bevels"... Bit like this: <===> . Housed within similarly shaped members, containing small ball bearings. There is essentially zero up & down play. A slight sideways freedom when fully free to move, which goes away, in normal use, by tightening a thumb screw. Even in tighter setting, sufficiently free (lubricated) to be moved easily manually or by the smallish motor for focussing...

We'll see if this initial limited usage (good impression) lasts.

[Mike Hawtin]

Hello Sam

I have the 6" F4 and if you are not comfortable doing major surgery to the scope then I suggest you avoid it. The major issue is the small size of the secondary which is also not offset and the excessive back focus which produces a fully illuminated field of about 6mm diameter!! In order to increase the field diameter I have moved the focuser 50mm along the tube. This scope needs a 75mm flat, not the 63mm provided, with a 63mm flat you really do need to offset it and reduce back focus to an absolute minimum. There were other minor niggles but then the scope is cheap as chips and my expectations were not that great.

Mike

[SamAndrew]

Thanks Mike,

I did think 63mm seemed a bit small, but then I thought maybe everything scales down with a smaller scope.

Hmm, it's a shame it need's major surgery, I don't see why they build it to such a budget, I'd happily pay twice the price if it worked out of the box.

Have you got any results from yours yet or is it still work in progress ? I'll hold off and see how you get on.

[Macavity]

The thing that confuses me is this vague (advertising) notion, UK and German dealers select / specify a "special" subset(?) of GSO scopes that actually... work?

Certainly the back-focus of my GSO / TS / Modern Astronomy: 8" / F4 is considerable? But Kudos to EACH of the aforesaid dealers especially the latter! Also true (see above) there is little "scope" for introducing the canonical "secondary offset" in even the 8" version? Is the secondary size adequate? Good question! Curiouser and curiouser...

We are all "right" to some approximation? The consumate imager who doubts the worth of a £400 fast scope, the VIDEO astronomer (me!) who thinks it's a "good thing" for his particular application / budget. The casual readers of this thread, who are baffled (ahem) by the whole thing...

[ollypenrice]

Our 20 inch is F4.1 but visual only, at which it's pretty good and newly imprvoved with a better secondary.

I have tried the 8 inch F4 with a CCD rig and found it unsatisfactory. I didn't get as far as worrying about the collimation because it could not hold the camera at right angles to the light path. Something was sagging, I think the tube itself being the problem.

Another owner I know is rebuilding one and keeping only the optics.

In imaging the need for good orthogonality and collimation is far greater than in visual use I think, but watch me catch it from the visual buffs now!

I hope I'm not a 'posh telescope snob' of some kind. I have a ZS66 and a second hand Pronto, both very cheap, and have imaged with them enjoyably.

Olly

[Mike Hawtin]

Have you got any results from yours yet or is it still work in progress ? I'll hold off and see how you get on.

Sam, no results I'd care to share atm, I need to strengthen the focuser/tube connection as I suspect it's sagging a bit and then look at fixing the primary more securely, perhaps with silicon as it needs recollimating when it's moved to different parts of the sky. Just as a matter of interest the other minor issues were:

1 No provision to prevent lateral movement of the mirror in its cell.

2 Inadequate focuser, the 10.1 reducer is unusable due to lack of feel in its operation, it is very bouncy and it's not just this particular example either as the identical one on my 6" RC is the same but at F/9 focus is a good deal less critical.

3 One tube ring needed its hinge drilling out to provide clearance as the two halves did not match up when clamped being offset by about 4mm consequently stressing both the tube and the ring itself.

4 The bottom tube reinforcing ring/outer cell casting arrived loose and to tighten it up it is necessary to remove the main mirror cell to gain access, not something newcomers to the hobby would care to do I suspect.

I am not a difficult customer, past experience has taught me that very little astro gear works straight out of the box and I come to expect that I will have to fettle and tweak as a matter of course but this little scope is a major project in its own right.

Hope this helps

Mike

[SamAndrew]

They're really not doing their reputation any good selling scopes in this condition; they should really discontinue it and then redesign it.

I'll have to cross this off the list for now, I'm not after a major project as an imaging scope. It appears then that a refractor is the only way to go for a wider field of view; time to go do some more research.

Depending on what I find I may start a thread titled:

Equinox 80 with Moonlite vs TS 80/480 Triplet with 2.5" focuser

[Mike Hawtin]

It could be worse, the 6" Boren-Simon Power Newt Astrograph is based on this scope and they are asking $1,800 for it, imagine how you would feel if you paid that much for it.

Mike

[ollypenrice]

It could be worse, the 6" Boren-Simon Power Newt Astrograph is based on this scope and they are asking $1,800 for it, imagine how you would feel if you paid that much for it.

Mike

Ah, but it uses only the optics, surely, and not the tacky mechanical parts? I haven't seen a Boren-Simon but Harel Boren's images are outstanding, thoroughly world class on difficult dark targets.

TS do a 'Supernewt' (Catatonia has one) which is cheaper than the Boren-Simon but needed an enormous input of effort to get into optical fettle.)

You can buy fast corrected Newtonians (from ASA, Orion Optics and Takahashi) but they dont't come in with 'two zeros' price tags.

Cheap and fast do not go together in optics...

Olly

[Mike Hawtin]

Olly, follow the link, it looks to be exactly the same ota with the addition of a primary cooling fan and of course the Astrosysteme 2" X.73 Reducer Corrector.

POWERNEWT TELESCOPE | 6inch

Mike

[SamAndrew]

It looks like you're basically paying a huge premium to buy the same scope with the mirror mounted properly and a properly sized and orientated secondary (plus the ASA reducer), it even looks like the same focuser.

scope with reducer 1800$ = £1110

ASA reducer = £705

therefore scope = 1100 - 705 = £395 , maybe that's not such a big premium to pay if it actually works.

[Macavity]

Strange, indeed... I can see no external physical difference between the review 8" Boren Simon at $2199 and the (my) TS version at £400. OK, you get the (sophisticated?) focal reducer (F4 -> F2.8) - The mirror purports to be "1/12 wave". But even then? But I then probably wouldn't / couldn't pay ~£2000 for anything! I sense one can be forgiven for a modicum of confusion re. this whole area...

At £400 the price of the TS (GSO) components almost exceeds the total -- Monorail focussers are about €200 now. <G> Had I a workshop and fewer real-world perturbations, I'd be trying to make a half-decent OTA for my 8" / F4. There seems little "magic" about the construction of mass-produced Newts?

No accusation of snobbery from me. (Sorry if that was perceived). Precisely as you say, Olly, some people want to observe (image) rather than mess about modifying (rebuilding!) a scope. I have no answer to the question: Do budget scopes prompt people to "aspire to..." or to "expire from..."? LOL. Personally no scope has ever discouraged me. Not even my original 30x30 1960's type refractor. Still "cherished" somewhere at the back of my wardrobe...

[Astroscot2]

Its interesting reading this thread, After seeing the 6" powernewt Ad a number of weeks back I emailed TS on whether the 6" GSO could be used with my ASA reducer, oddly TS have always responded quickly to any questions, however in this case there has been no reply ?

Newts need tinkering regardless of the mechanics or price tag, some of the most impressive images ive seen recently have been taken through them and I sort of see a swing towards small fast well corrected newts for imaging in the future.

[Mike Hawtin]

It looks like you're basically paying a huge premium to buy the same scope with the mirror mounted properly and a properly sized and orientated secondary (plus the ASA reducer), it even looks like the same focuser.

scope with reducer 1800$ = £1110

ASA reducer = £705

therefore scope = 1100 - 705 = £395 , maybe that's not such a big premium to pay if it actually works.

Sam, I don't think you are getting anything other than the original scope plus the reducer/corrector and perhaps a cooling fan (not sure about that though). The secondary is the same size with no mention of offsetting and the primary cell appears identical.

Mike

[SamAndrew]

Its interesting reading this thread, After seeing the 6" powernewt Ad a number of weeks back I emailed TS on whether the 6" GSO could be used with my ASA reducer, oddly TS have always responded quickly to any questions, however in this case there has been no reply ?

They must get a few questions about the ASA reducer, I also asked them a few weeks ago if it could be made to work with a Quattro, they did respond within a day.

I sort of see a swing towards small fast well corrected newts for imaging in the future.

Indeed, looking at the baby power newt, this could be the perfect scope if it works

[SamAndrew]

Sam, I don't think you are getting anything other than the original scope plus the reducer/corrector and perhaps a cooling fan (not sure about that though). The secondary is the same size with no mention of offsetting and the primary cell appears identical.

Mike

They talk about lots of effort in design and testing, so they must have changed something, I'll send them an email and see what they say

[Astroscot2]

They must get a few questions about the ASA reducer, I also asked them a few weeks ago if it could be made to work with a Quattro, they did respond within a day.

Indeed, looking at the baby power newt, this could be the perfect scope if it works

On a side note, Bern at Modern Astronomy has a small batch of these ASA correctors in stock if your looking for ultra fast newt without AG prices ;-)

[SamAndrew]

On a side note, Bern at Modern Astronomy has a small batch of these ASA correctors in stock if your looking for ultra fast newt without AG prices ;-)

Yes I am interested in getting one for the Quattro, but Ideally I would like to try before I buy :S

I think I would need a lower profile focuser

I'll drop them an email and see if they've got any advice.

[Astroscot2]

Hello Sam, I just recvd mine, the 2Korr were out of stock for some time last year due to ASA waiting on a lens. Bern was a great help in dealing with ASA for me and in the process he now has a small batch I beleive. I was lucky enough to be able to borrow one last year and try on my CT10, I had to shave 1mm off the 2" adapter to allow enough in-focus however with the new corrector its not nessesary for some reason.

Its expensive but worth it I say.