when to collimate?

[algol]

so i've had my scope sice end of feb and i've recently noticed that when out of focus the secondary seems to be a little off center, i have been told that if done correctly saturn should show a hint of cassini and i should be able to correctly resolve m13 etc.

so is it time to collimate?

also as this may be my first time doing this maybe post stories of your first efforts, especially any mistakes so i can avoid them

[barkis]

A star test is the best way to judge your optical alignment. If you scope is of a shortish focal length, the the secondary mirror will be offset a bit in a direction away from the focuser.

The best advice is to make very small adjustments when collimating. Judge any change an adjustment makes before making another.

Ron.

[geoff_k]

Algol

Ron is right - take it in small steps. I assume you have a centre spot on your main mirror as this helps a lot. I use a Cheshire eyepiece and to back it up a laser collimator as well.

Take a look at this website - very useful advice for collimation.

http://andysshotglass.com/Collimating.html

Geoff

[Whippy]

i have been told that if done correctly saturn should show a hint of cassini and i should be able to correctly resolve m13 etc.

Not necessarily. Your seeing conditions will dictate what you will be able to see at any given minute, let alone any given night especially when you're talking about trying to use your scope towards the limits of what you'll actually be able to see with it.

Tony..

[aries]

I am no expert as to Collimation, but one thing I can put forward,

is that, when you have released the Locking screws of the Primary Mirror,

and then carried out the very minor adjustments needed to get everything in line, Please be aware of not overtightening them afterwards, as a pinched mirror

can give you some weird and wonderful results, and in some cases, irreparable damage to the mirror itself.

My first Collimation of my little Newt was a step into the unknown, but there are many members who will guide you through any steps you may be apprehensive about, and now, I can approach it with confidence, and using the guidance

I recieved from them, achieve a satisfactory result on a relatively lower class

scope. Once you have performed your first Collimation, and noticed the improvement, you will wonder what all the fuss is about............

(unless you have a refractor or SCT!)

HTH

Nick.........

[jakey]

I had a nightmare in collamation and I am not sure I will ever do it again. The worst part for me was the secondary mirrror, one turn too much and it slides down the tube.

[The Warthog]

Ok, take a deep breath. This isn't easy, but it isn't impossible, and any primate with a forebrain and opposable thumbs can learn to do it. Even me.

First of all, your secondary should be offset from centre a little, away from the focuser. Don't worry about the exact measurement; it is the thing least likely to be the problem. It should however, be opposite the focuser, not moved up or down the tube. It should also be square to the focuser, but they are usually shipped from the factory at least square to the focuser and in the right position.

There should be a dot in the centre of the primary. If there isn't, take the primary out and put a dot in the centre of the primary.

Using a Cheshire collimator, or afilm canister with a hole in the centre of the cap, and the bottom cut off, look at the secondary mirror and, if necessary, adjust it so the primary mirror is centred. This will be when you can see all the mirror clips at the edge, or just past the edge of the secondary. From here on, leave the secondary alone.

Now, using the three adjusting screws at the back of the primary, adjust two of the screws a quarter turn at a time, until the reflection of your eye in the primary is in the dot in the centre of the primary. That's all you have to do, however, that part of the job will drive you crazy, so start early in the day, and if things go bonkers, take a breath, back off the screws and try again.

Use only two of the screws to make adjustments, if you run out of adjusting room on one of the screws, then you'll have to use the other two, but that hardly ever happens.

Once you get it lined up, you're done. Now, have a drink.

Do the whole operation with the tube level or pointed slightly down, so that anything you drop will roll out the front of the tube. If the secondary holder falls apart, take all the bits out of the tube, and carefully reassemble them. Mark one of the spider vanes so you get it back in the right way.

And as to when should you do it, you should do it when you check and find that the telescope is out of collimation.

This is, after all, easier than rebuilding a carburetor, and I have seen primates without detectable forebrains do that.

Hope this helps.