How do you efficiently collimate an SCT?

[arad85]

I'm spending an increasing amount of time collimating my SCT - probably as I'm a bit, well... you know . I'm finding it really difficult due to the seeing conditions I have here most of the time. Does anyone have any experience of artificial stars for collimating SCTs or can suggest any other method that works which

1) Doesn't involve wasting imaging time at night

2) Can be done without seeing making my Airy disks look like a bunch of wobbly jelly...

TIA

[Merlin66]

Not really!

I have the 12", 10" and 8" SCT's to collimate occasionally ( not a regular requirement)

A webcam and a real star are the best method.

I have artificial stars but geting them far enugh away from the telescope is a problem, then you get thermal currents from the ground anyway...

Don't take that long to do, maybe 5 to 8 mins and they stay in collimation for a LONG time. (I've fitted Bob's knobs to all my SCT's)

[arad85]

Thanks,

Yup Bob's Knobbed here too... I can't quite seem to get mine perfect (to my liking). Can't quite get the spot centrak and the rings to be equal. There always seems to be one section of the ring that is not quite "right", even although the central spot looks in the middle.

[Merlin66]

A couple of "rules" NEVER collimate with a diagonal and use the highest power to get the tightest image.

A webcam and barlow will make things much easier to see, measure and adjust.

Get close enough to focus so that the central dark area is almost lost.....

Oh and always finish focusing in the same direction (minimise mirror movement between images)

[arad85]

Ahh... collimating with my WO diagonal in place. But surely you should do it with it in place if you're observing

Will give the Barlow/webcam method a go next time...

Ta

[Merlin66]

Collimate the optics of the telescope first... then see what difference if any the diagonal makes. Remember you'll probably image etc without the diagonal. Some are OK, others can and do affect the collimation.

One less variable....