joining the GS Dob club!

[gaa_ian (Ian)]

No problems Janos
You will find the Alt. tension problem can be fixed by putting a keychain ring of suitable strength on the end of the tension spring & attaching that to the attachment point on the base.
A cheap dewshield for the finderscope can be made with a section of postal roll, painted black with adhesive velcro dots inside to give a firm fit.
Lots of good info under Equipment discussions: What mods have you made.

[janoskiss (Steve H)]

gaa_ian,

I'm just studying the collimation instructions in the Orion XT8 user manual:

Your SkyQuest XT comes with a collimation cap. This is a simple cap that fits on the focuser drawtube like a dust cap, but has a hole in the center and a silver bottom.

Do you know what this silver bottom is, and what it is for? (Yes, I know I have a laser collimator but I like to have multiple independent ways of checking things.)

[gaa_ian (Ian)]

Hi Janos
I have read that you can use an old film canister with a hole drilled in the centre to collimate your scope.
I have not tried it my self, my fav. way of collimating my dob is to remove the eyepiece, find a brightly lit wall & centre the secondary mirror in the centre of the primary, using the clips that hold the primary in place as a guide.
Then adjust the secondary by seeing the reflection of my eye in the centre of the shadow cast on the primary by the secondary.
Sounds a bit weird I know, but try it and you will see how simple it is.
I have tested this with a laser collimator afterwards and have found it to be quite accurate, the final test is with a high powered eyepiece & a bright star to check for neat concentric circles.

[Starkler (Geoff)]

One needs to be very careful with laser collimators.

Unless the laser itself is collimated well , it will introduce errors and youll never get an accurate collimation.

Cheshire or barlowed laser technique is easier to get accurate results with.

[gaa_ian (Ian)]

I agree starkler, I found that problem with my "Andrews" collimator, the IC board inside is not secured & even a small amount of overtightening of the "on" screw can muck up the lasers collimation.
In fact I hardly use mine becqause of this fault.
The housing the laser comes in is good quality, but the laser pencil inside is a $5 special

[janoskiss (Steve H)]

Yes, I'm aware of possible laser misalignment mucking things up, and the laser I got is not perfect either, because the spot on the return target moves a little when I rotate the laser in the focuser (and I also saw the keychain laser inside the thing, and needless to say was unimpressed). Still it's better than anything else I have for a very quick alignment. I wish I could loan it to BLiTZWiNG, so he wouldn't have to fiddle so much before getting some decent views. BTW. focuser cap has pinhole in centre, no need for film canister.

[RAJAH235]

Hi Guys,
Janos, DOBs make good drip catchers as well, when you run out of ordinary buckets. Just watch out, when on public/open nights, for those that think it's a rubbish bin tho!

[janoskiss (Steve H)]

Originally posted by RAJAH235
Janos, DOBs make good drip catchers as well, when you run out of ordinary buckets. Just watch out, when on public/open nights, for those that think it's a rubbish bin tho!

Had a good chuckle at that one. Thanks. I'll make sure not to point it near zenith. Maybe the next mod will be a giant label: "TELESCOPE".