GSO RC8 collimation with laser and Taka microscope

[philming]

Hi all !

I've got a GSO RC8" (the same as the one sold by different brands), and I usually collimate it using a Takahashi collimation microscope.

The other day, I gave collimation a try with a friends laser (a Baader one, well collimated itself as far as I can tell).

The collimation was perfect with the taka, but was off by a little with the laser.

Someone suggested It could be a problem with the secandary mirror centering.

Can anyone give me some advice on this ? Could it be the case and if so, how do I correct this ?

Thanx for your input and best regards !

[Jessun]

My faint understanding of this is that the laser may well be off after 'traditional' collimation - and you mark where the dot or cross hits back. The laser will then allow for quick re-collimation, or confirmation, in the field for instance after knocking the scope around in transport.

Try a star collimation - the ultimate test - to confirm your efforts at this time. The Tak is probably the second best to an actual star.

Others with more experience may well correct me on this.

/Jesper

[RobH]

Unless your laser is perfectly collimated, and then is absolutely centered in the focuser, which also needs to be perfectly aligned, you will always find the laser to be out. Rotate the laser in the focuser and see if the dot of the laser on the secondary stays in the same place, or if it rotates around a central point. If it stays in the same place, then all is correct with the laser itself and the focuser.

Re. centering the secondary on the GSO scopes....you can't do it. There is no facility for adjustment.

Rob.

[philming]

As far as I can remember, rotating the lase rin the focuser didnt "rotate" the return dot. It stayed at the same decentered place.

[philming]

Sorry can't find how to edit my post.

So that leads me to think either the focuser isn't aligned, but I'm not sure. Hence my post ;-)

[RobH]

Which focuser does it have?

Sounds like the laser itself is collimated.

[philming]

The monorail TS focuser.

[alan potts]

I tried one of these laser things about 3 years back and it was the Baader one. When I put it in my LX 200 it was telling me it was so far out I would be lucky to see the moon with it. I knew of course that this was not the case, I sent it back, in any case for a SC scope it is next to useless but I didn't know that at the time.

Try a star colimation I do on all my scopes and I am sure that there is little or nothing wrong with them. I start with a low power and move up to get it really accurate.

Alan.

[RobH]

The monorail TS focuser.

My RC is a 12 inch truss version based on the GSO optics and built by Astrophad for Ian King......Ian told me not to bother with the TS focuser as both he and Nik Szymanec had run into collimation issues with the unit. I currently have a Moonlite unit, which is fine collimation wise, but a bit puny, so will be replacing it with a Feathertouch one when funds are available.

Rob