Collimating 10" GSO Dob..

[barees63]

This will just confirm that your centre spot has been placed accurately (or otherwise).<!-- / message --><!-- sig --><!-- / message --><!-- sig -->

I'm pretty confident about this (my second) center spot, the Catseye kit has a neat acetate precision spotting template, you actually stick the center spot to the template then press it onto the mirror..

Until you crank the mag ...

I'll worry about that later ;-) for now 130x is my limit (I have a $20 barlow but it seems pretty sucky do I don't use it)..

[janoskiss (Steve H)]

I believe the scope should be star tested at higher magnif than you are actually going to use it at.

[Starkler (Geoff)]

Originally Posted by janoskiss

Until you crank the mag ...

My sighttube collimated f6 8" just starts failing the star test at around 400x, on the rare occasions that conditions allow star testing at such high magnifications. It is very fiddly to get it any better, if not impossible, without tracking. But if you're not imaging there is little point.

Yep Steve that the thing. You cant use the star test to align unless you're sure that the star diffraction pattern is exactly in the centre of the fov.
How do you do that and keep it there at +400x without tracking?

What really helps is if your centre donut size is well matched to the size of the illuminated ring from the cheshire. Another option for ultra fine collimation is a barlowed laser setup.

[janoskiss (Steve H)]

.. and the autocollimator. Bird uses it, it must be good!

[barees63]

What really helps is if your centre donut size is well matched to the size of the illuminated ring from the cheshire.

I believe that is the strength of Catseye system, the center spot is precise and exactly matched to the Cheshire ring, also the spot is triangular and each point of the triangle is matched to one of the Primary tilt screws so it's supposed to be easy to figure out which screw to adjust to get the points of the triangle touching the inner ring (it's supposed to be collimated when each point just touches the cheshire ring).

[barees63]

FYI, went out last night with newly collimated scope.. stand out difference for me was 47 Tucanae, up till now I've only ever seen this as a bright hazy blob with a hint of stars.. last night it was "fully resolved" and completely blew me away! I could see countless beautiful stars and a tight core, if this is the difference collimation makes then the pain was worth it!

[Starkler (Geoff)]

Originally Posted by barees63

FYI, went out last night with newly collimated scope.. stand out difference for me was 47 Tucanae, up till now I've only ever seen this as a bright hazy blob with a hint of stars.. last night it was "fully resolved" and completely blew me away! I could see countless beautiful stars and a tight core, if this is the difference collimation makes then the pain was worth it!

Its worth it alright, and next time you do it, it will be so much easier and not painful at all because you now know what to do

Newbies are often terrified of tinkering with their newtonians, but once you know what to do its quite simple. Its a bit like owning a musical instrument, to get the best out of it you have to be able to tune it