Understandable collimation for beginners

asimov (John) · #1 12-07-2005, 05:09 PM

After reading a lot of article's about collimation for reflecting telescope's over the year's, I think this article is the easiest to understand that I have come across to date. Not too complicated, & giving a beginner a good understanding of the step's involved to achieve good collimation.

http://skyandtelescope.com/printable...rticle_790.asp

This next link/article mainly deals with secondary mirror 'off-set', but more importantly... WHY it is thought upon as necessary to do this to get collimation even better.

http://www.fpi-protostar.com/collim.htm

I hope these two article's are of some help, mainly to new-comers of astronomy.

Cheers.

ballaratdragons (Ken) · #2 12-07-2005, 07:53 PM

John,

I have never seen the second site before. Great find!! I am going to use it myself to double check everything.

Thanks.

slice of heaven · #3 12-07-2005, 08:47 PM

AAAARGH not the rulers again!!!

I wonder if he used a centre punch to mark the centre?

asimov (John) · #4 12-07-2005, 08:53 PM

yeah! I hate that idea! Give's me the shudders. The 'circle of paper the same diametre as the mirror, folded twice to give you centre, small hole in the centre of the paper, lay on mirror, mark mirror with texta' trick, I think is more appropriate..

ballaratdragons (Ken) · #5 12-07-2005, 08:57 PM

Only if you are very very careful with the paper!

asimov (John) · #6 12-07-2005, 09:19 PM

My idea is to simply not do it at all. I'm totally paranoid of centre spotting my 12.5"....I'll just continue to star-test to collimate the primary.

toetoe (Peter) · #7 12-07-2005, 10:03 PM

I have been reading a few over the last few days but not seen these ones, thanks John.
My little scope needs to be done so i gotta read up and learn and get it done.

elusiver · #8 13-07-2005, 12:10 PM

i used the paper trick to centre spot my primary. it works well.. cause the folds in the paper kinda make it want to hold a conical sort of shape so really the only part of the paper that really touches the mirror is the centre of it.

there's a good collimation tutorial that's made in flash.. i've got the link at home.. if your a more visual type of person like me it's excellent.. i'll post the link once i get home.

el

Sausageman (Mike Boggan) · #9 24-07-2005, 04:27 PM

Thanks John.
The links will prove invaluable.
I have guy's at work who have been asking me questions like this.
I can now give them references rather than going and fixing problems myself.
Thats a big load from my shoulders.
Thanks again.

Mike

asimov (John) · #10 24-07-2005, 04:56 PM

Think nothing of it Mike..

BLiTZWiNG (Trent) · #11 28-07-2005, 04:17 PM

Nice... if I ever get enough free time to use my scope again I'll probably have to collimate it again... and that was hell for me the first time I did it (and probably for most of those that helped me!)

elusiver · #12 02-08-2005, 10:53 AM

just a quick question.. is there any tricks to collimating solo? or to u just look into the sight tube/cheshire/eyepiece then remember how it looks, quickly move to the back fo the scope turn the knob and then go back and see if it's right? Can experieced guys look at a star test and know exactly which knobs to turn and how much? Been practising star testing and keep thinking there must be another way that someones devised. Like how do those people with those big truss dobs star test collimate? Look in the eyepiece, climb down the ladder, make the adjustments, climb back up the ladder, re-centre the object(cause it would've drifted off by then), then if it still not right repeat.. it'd make for a good workout.. who needs the stair master?

el

slice of heaven · #13 02-08-2005, 11:21 AM

No real tricks with the basic setup El, just experience.
Rob(rmcbp) posted to only use the 2 closest screws, thats a good tip.
I dont use the 'lock' screws,I replaced the springs with heavier ones(I dont know how this relates to the 8"s though,they maybe strong enough), 3 screws makes it easier.
Having a setup that maintains fairly good collimation helps a lot.

There are triangle centre spots available that can fitted with the points directed at the screws for easier orientation.

elusiver · #14 02-08-2005, 01:46 PM

mmm... triangle centre spots.. that's a decent idea. hmmm..

the problem i've got at the moment is i'm kinda fumbling through collimation.. which is why i need an assistant. I don't grasp yet which knobs move the mirror in which direction.. so colliamtion with an assistant at the moment goes a little like "turn that knob.. oh.. no the other way.. ok.. now try the lowest knob.. ook.. no back the other way"

so a triangle centre spot would be great for that. If i was to re centre spot with a triangle.. would it be recommended to remove the old circle centre spot first.. or just place the triangle over it.. if it was to remove the old one.. how would you go about it?

el

slice of heaven · #15 02-08-2005, 02:03 PM

Start with making sure the original spot is centred properly.
I cant see any problem laying the new over the old unless your wanting to use a laser. Then youd need a perforated triangle and remove the spot. The spot is in the shadow of the secondary ,an area of the mirror that is'nt used, any marks wont matter,but just be very careful and take your time.

asimov (John) · #16 02-08-2005, 05:52 PM

I find collimating fairly easy these days. I collimate the secondary indoors in day light. Once it's done right, you shouldn't need to do it again, unless you give the scope a hard knock or something. I did my secondary collimation again just recently again though, after I made my sight-tube. The primary collimation I do indoors initially as well. Just fiddle with the primary collimation screws until the spider looks central in the primary looking down the focuser draw-tube. Then I take it out & do a star-test & finely adjust the primary until the criteria is met as under the rules of thumb for collimating using the star-test.

Starkler (Geoff) · #17 02-08-2005, 06:31 PM

Did my first ever collimation with a barlowed laser today on getting home from work.
Tonight being the first clear night in a while here I'll see how it goes.

asimov (John) · #18 02-08-2005, 06:42 PM

It'll be interesting to hear a report from you Geoff.

slice of heaven · #19 03-08-2005, 10:25 AM

Quote:

Originally Posted by Starkler

Did my first ever collimation with a barlowed laser today on getting home from work.
Tonight being the first clear night in a while here I'll see how it goes.

How did it go????

Starkler (Geoff) · #20 03-08-2005, 10:33 AM

Agh I got interrupted by other matters and didnt get to view last night