GSO centre spot. Muy bueno! Very happy!

[janoskiss]

Dear fellow iceinspacers!

Thank you all for advice on collimation and for encouragement to experiment & explore!

I centre spotted the mirror of my new GSO 8" Dob today, collimated it using the "barlowed laser" method of Nils Olof Carlin (S&T, Jan 2003, 121-124 (http://gmpexpress.net/~tomhole/blaser.pdf)).

I just spent over 3 magnificent hours outside with the scope and I am very happy with what I've been seeing. Saturn & the Moon looked fantastic! Jupiter was pretty awesome too!

This scope is one of the best things I ever bought! (one of the best non consumable things anyway)

[iceman]

Well done, nice work.

On a related note, i'm beginning to understand the differences between buying at Andrews and buying at Bintel.

Unless there was a significant design change between mine, starklers and yours, mine already:

1. Had the mirror centre spotted
2. Had the mirror back plate removed
3. Had the 3 rubber holders barely holding the mirror (not pinching)
4. Was collimated

Number 1 and Number 4 they freely advertise that they do once they import their scopes. Maybe they do number 2 and 3 as well because they are good additions.

Is it worth paying extra for those services? For some people it will be. For me, I didn't pay extra, Bintel came down in price. So I'm happy.

[Starkler]

My scope was reasonably well collimated out of the box, but did suffer astigmatism in both primary and secondary mirrors until I loosened the mountings of both.

I'm glad you like the scope Janos :)

[ballaratdragons]

Mike,

You don't explain which one did the better job! Andrews or Bintel?

[janoskiss]

The view through the EP last night made me forget all about a couple of things I wasn't too happy about after having had a close look at the mirror.

There are about half a dozen chips in the glass around the edge of the primary; a couple of them quite big and one of them just grazing the edge of the mirror surface. Also there is a ~2mm spot about 1.5" from the centre, and it does not look like dust or stain but damaged/oxidised coating. I hope it won't grow like they do on silvered mirrors.

[Starkler]

Janos I wouldnt be too concerned about very small chips that arent in the coated area of the mirror, but I wouldnt be happy with a brand new mirror with a damaged coating.

I would call the dealer about it.

[Striker]

What mike is saying Bintel service thier GS Dob before sale....meaning collimating and adding the circle on the primary.....Andrews dont......they sell straight out of the box....but as far as I know....it is cheaper of Andrews then Bintel.....

For me...my local shop would add the primary circle and collimate for nothing anyway.....But I might be lucky.

You obvioulsy pay for the service of Bintel which may suit people anyway....

Janoskiss....that review doesn't sound promising....I would let the retailer know for sure.

[janoskiss]

I don't know if there is much point in hassling Andrews about it. I'm not gonna send the scope back to Sydney for minor flaws that wouldn't be noticeable at the EP. I probably voided the warranty anyway by taking the mirror out!

It's probably a matter of this mirror having just passed quality control. These scopes are very cheap after all. The chips in the glass do not affect the coated surface, and the one blemish on the surface is small. My only concern is that it doesn't grow.

Most GSO Dob owners on these forums seem to have the 10", which have pyrex mirrors, so it'd be much less prone to chipping. The cheap 8" ones have window glass mirrors. Have any other 8" owners here taken out the mirror? How does yours look?

[Nortilus]

I got one but I don;t know enough about all that to take my mirror out. Well not yet anyhow. 'll let ya know when I do.

[rmcpb]

Mine is just right :)

[Dave47tuc]

Janos,
You said the Moon, Saturn and Jupiter were fantastic:D

So a mark on the mirror, maybe not that big a deal!

If it had holes in the coatings as Geoff has said, ring the dealer back. If its just a spot of dirt or something and not very big don't be to concerned. Chips on the edge of the mirror won't affect things to much.

If your happy with the views and by the way you sound you are.
Just get out and enjoy the night sky.:)

Best.

:astron:

[janoskiss]

Thanks Dave,
That's what I figured! :cheers:

[ballaratdragons]

Janos,

Your mirror is not made of window glass.

It is BK7 optical grade glass.

Yes, cheaper than Pyrex, easier to grind and polish than Pyrex, but definately a damn lot dearer and harder than 'window' glass.