New GSO Dob, crappy looking mirror.

[Omnius]

G'day all,
So I went and bought a GSO 8" Dob today, took it home and put it all together. Upon looking at the primary I noticed it is not round, so I wondered if the coating was faulty. I shone a torch down the tube to get a better look and the mirror is very dusty to start with and I also noticed that it has streaks all over it , like some one has cleaned it with a wipe or something. Like streaks on a window after cleaning it. The coating doesn't look like it's failing but just has a straight edge 1/12th around the top of the mirror and only intrudes about the same as the primary retaining clips.

Is this normal for GSO Dobs?

[barx1963]

Did you buy it new? If so who from?

Malcolm

[Omnius]

New From Bintel Melb , the service was great!!

[bojan]

Return it.

[Omnius]

Bugger, that sucks, I have had the worst luck buying astronomy equipment, I am working away for weeks, that's why I bought it today to take it to the excellent dark sky I am at.

[barx1963]

In that case, ring them up and let them know of the issue, but explain you cannot return for a while. Take it with you and use it anyway and return it when you get back.
Just make sure they are aware of what you are doing.
Odds are the views will not be majorly affected, and if they are you will have a point of comparison.

Malcolm

[Omnius]

Well I looked at the department store barska scope I have, it is 7 years old and has failing coating (expected) but does not have the streak affect. I will call Bintel tomorrow from St Arnaud. I am sure they will be accommodating as all I have heard is good things about them from these forums. I have been reading about how GSO use the consumer as the quality control rather than their own QC. Just unlucky I guess.

I will post the out come of this issue.

Cheers Malcolm, I am sure you are right about the performance, it will be a big improvement over my dep store scope (on borrow).

I have been excitingly following C/2012 F6 easily with the 12x60s since it entered the Crux and am loving this hobby.

[Omnius]

I went in to Bintel show them what I saw and in the 8" and 10" on the floor had the same issue but the skywatcher 6" and the gso 12" did not.

I was told it was not an issue and I was probably the 1st customer to shine a bright torch (5w LED) down the OTA.

[Steffen]

I'm surprised you got that advice from Bintel. A brand new mirror should be spotless. There can always be some dust on it, after all, the OTA isn't sealed. But streaks from haphazard cleaning shouldn't be there.

It seems GSO may have a QA issue, but Bintel's response puzzles me most. At the very least they could have offered to clean the mirror for you to be sure there is no other issue there. They do (did?) clean optics as a service, why would they not do this as a matter of course?

Cheers
Steffen.

[DJDD]

I agree with Steffen.



but if 6"/12" are ok and 8"/10" exhibit the streaks wouldn't that mean that there is a problem with the batch rather than normal for a dob?


also, you mentioned in the first post that the mirror was not round. and the mark around the edge. Has it slipped in shipping?





what does it look like with a low power torch? can you see the streaking and other issues?


i have only bought second-hand so some wear and tear was expected.

perhaps the streaking and non-roundedness (is that a word? well, it is now) will not have any impact on your observing but if I bought a new telescope then, unless well-convinced otherwise, I would be unhappy with a mirror that was not round and not clean. some dust, maybe is ok.

[Omnius]

I just tried it with a 1w LED and I can still see it easily.
They did not offer to clean the primary and showed no concern about the straight edge.
I was told they are what they are and you can see the machine marks during a ronchi test, but they come in within tolerances.

yeah I am unhappy but not sure what to do.

[Steffen]

I bought a GSO 8" Dob a while ago with a mirror that appeared well manufactured and perfectly clean. If your mirror is like you describe it I wouldn't accept it. I'd either return the scope or ask Bintel for a replacement mirror (they sell 8" f/6 mirrors by themselves).

Cheers
Steffen.

[barx1963]

It is a good rule not to shine torch down a dob's tube as it always makes the mirror look horrible. At night with a red torch it looks even worse. Having said that, I would be disappointed with the response you had from Bintel. My GSO 12" from andrews had a perfectly clean mirror at delivery. It ain't now, but thats another story!

Malcolm

[asimov]

I'd expect optics in a brand new scope to be perfect. I wouldn't be taking 'NOT a concern' as the required answer. Take it back & stand your ground until you get to pick another one is my advice.