Collimating: how often?

[Spiney (Steve)]

Well I received my 12" Dob on Monday after ordering it from Andrews on the previous Friday, talk about quick, and after spending ages I think I have it pretty well collimated. I took it out of the house on a trolley and tweaked the primary mirror again before a brief viewing session, bloody clouds.
My question is how often do you have to collimate the secondary mirror as this was the difficult part. The primary was dead easy. Do you find that the secondary pretty well stays put and it is the primary that needs most of the attention?

[wavelandscott (Scott)]

You should check collimation before each use...

Generally speaking, with a "tube" reflector after you get the secondary set up properly it most likely won't need much adjustment unless you put the scope through some sort of traumatic experience...

The primary will probably be the place to make your adjustments each new time you go out...

But, do follow, the whole checking process each time.

Also remember that collimation can and does change as the temperature of your mirror changes...it is best in my opinion to let the scope/mirror cool before doing the "final tweak" collimation prior to viewing.

After a time or two, the whole process will only take a few minutes and will become second nature to you.

Good Luck and Happy Viewing!

[Starkler (Geoff)]

Originally Posted by Spiney

Do you find that the secondary pretty well stays put and it is the primary that needs most of the attention?

Yep. With a fixed tube dob the secondary shouldn't shift unless you move it yourself. Still it doesn't hurt to check occasionally with the sight tube.

[Spiney (Steve)]

Thanks guys.
I'll always check the secondary at the same time as the primary, its just that I was hoping that the secondary would not need as much attention as the primary. I only move it from the shed to the observing position which is about 10 metres so with any luck adjustments should only be of a minor nature. Haven't done a star test yet that should show how crappy my collimation is.
Although when viewing for the first time at objects like the lagoon nebula, M4 and M7 they looked pretty good too my untrained eye.

[wavelandscott (Scott)]

Like many things in this hobby, the more your practice, the better you get at it (observing details, collimation, star hopping etc.)...

Sounds like you are headed in the right direction!

[bathurst77]

I have a 10" dob (Andrews GSO). I dont have a clue how to collumate it, or what tools (if any are needed). Im kinda afraid to mess with it.

One thing I did do was put casters under the base so I can roll it around easily. makes it a bit wobbly but its very handy.

[Spiney (Steve)]

Bathurst77,
Have a look at this site www.andysshotglass.com and it should steer you in the right direction. As a complete beginner I found this site very helpful. I also googled the word "collimation" and looked at a few other ideas on collimating and between them I think I succeeded in the end.

Wavelandscott, thanks for the encouragement. When these clouds clear I'll be heading out to align my new telrad and then I should really be able to find what I'm actually looking for!

[astro_nutt]

Hi Bathurst 77
Castors, (the lockable one's!) on the base is not a bad idea..I have seen, however, a trolley-base specially made with 3 heavy-duty braked rubber castors as well as screw-down lockable feet to keep it stable...and don't worry about collimation too much..it's not that hard to do..just time consuming the first time you try it..and like the others say..just a tweak for fine tuning after a trip!
Cheers!

[DougAdams]

Originally Posted by Spiney

Do you find that the secondary pretty well stays put and it is the primary that needs most of the attention?

I owned the GSO 12" for about 8 months and found the secondary stayed put, and the primary would shift even during use! The primary springs were rather "undernourished"

[astro_nutt]

Hi DougAdams...
I've been to Bunnings Warehouse and found a rather good spring section..might be worth a trip for something beefier!
Cheers!