Laser collimator

[ecosse]

How easy is Collimation really with a laser collimator? Watched a couple of videos on you tube and it looks like it only takes a few mins. I currently have a Cheshire and a cap made from an old camera film tub but I'm still having a bit of trouble getting my newt lined up! Would I benefit from a laser?

Also I'm going to possibly be buying a 200p dob at the end of the month so I would like something easy to collimate it with

[nicnac]

i have the cheshire and a hotech for fine tuning

it is easy when you get used to it, have you read AstroBabys guide to collimation?

[ecosse]

Yeh I was reading the guide while trying but I'm not really seeing the same as what the guide shows. If the laser is as easy as the you tube videos make out, seems like it may be the way forward for me

[malc-c]

I use a Hotech and it is as simple as it is in the video... couple of minutes and the jobs done

[ecosse]

Who sells the hotech in the uk? Are the other laser collimators like the ones that flo sell just as good?

Also I'm sure I saw somewhere that the laser collimator has to be collimated aswell? Is this hard to do?

Thanks for the replies

[John]

Who sells the hotech in the uk? Are the other laser collimators like the ones that flo sell just as good?

Also I'm sure I saw somewhere that the laser collimator has to be collimated aswell? Is this hard to do?

Thanks for the replies

The lower cost laser collimators may need themselves to be collimated - this webpage outlines a simple procedure:

Laser Collimator Collimator

I've not heard that the Hotech's need this so I guess you get what you pay for with collimators, like everything else

I use a low cost laser that has now been collimated and it works well enough. I always do the final checks and adjustments using the star test though.

[swamp thing]

Laser collimation is extremely quick and easy, the videos are pretty accurate.

The whole process of collimation is an Astro myth that it's even slightly difficult. In short, a monkey could do it.

It normally takes me under a minute to collimate either of my (fast and supposedly difficult) Dobs.

In fact finding the tools to do it in my untidy van takes longer.

Setting up a GEM I find considerably more time consuming.

Regards Steve

[umadog]

Yes, good tools certainly help. Bad tools make things worse.

Collimation isn't hard but it can be a little confusing when you're learning it from a book or the internet. It makes more sense if someone shows you. Also, many of the the guides aren't sufficiently clear as to why you're doing certain things. They're just a series of instructions. Understanding makes things easier.

I like recomending these two posts because they explain the "why" in a good amount of detail:

http://www.cloudynights.com/ubbthreads/showflat.php?Cat=0&Board=reflectors&Number=3033065

http://www.cloudynights.com/ubbthreads/showflat.php?Cat=0&Board=reflectors&Number=3532750

The latter link discusses the autocollimator a lot. This is a nice tool because it's very accurate (better than a laser, actually) and provides a lot of information. The down-side is that it can be a little confusing to use it at first. What's also nice about the latter link is that it tells you what each of the tools (including lasers) can measure. Your scope is collimated when the secondary is rounded as viewed from the focuser and when any two of those four errors have been minimised through a process of measurement and tweaking. Once two have been minimised the other two are automatically taken care of.

The Hotechs will come collimated but in principle they could, like any laser, become uncollimated. You should always check if something looks funny.

[ecosse]

Thanks for the advice guys I shall give that link a read later on after work

[steppenwolf]

Also I'm sure I saw somewhere that the laser collimator has to be collimated aswell? Is this hard to do?

It is absolutely true that the collimator must itself be collimated but this is often a simple process. Personally, I wouldn't trust the manufacturer to get it right straight out of the box and the one I bought came with self collimating instructions and the Allen key for doing it.

You need a cradle to hold the thing for testing while you rotate the collimator watching for movement on a distant wall. The laser is adjusted until you can rotate it in the cradle and get zero movement of the dot on the wall. Here's my cradle:-

[Stephen]

It is absolutely true that the collimator must itself be collimated but this is often a simple process. Personally, I wouldn't trust the manufacturer to get it right straight out of the box and the one I bought came with self collimating instructions and the Allen key for doing it.

You need a cradle to hold the thing for testing while you rotate the collimator watching for movement on a distant wall. The laser is adjusted until you can rotate it in the cradle and get zero movement of the dot on the wall. Here's my cradle:-

That's positively high tech! Mine is a plank of rotting wood with five nails bashed into it at random angles .....

[ecosse]

That looks and sounds fairly straight forward. Nice crafty rig you got there

Like like I will be investing in the hotech then when I buy my new scope

[ecosse]

Just ordered the baader laser from flo, the hotech one was a bit pricey for me just now so I Will see how I get on with this one

[umadog]

Good stuff. Note the use of the barlowed laser method for adjusting the primary. This is the preferred way of doing things because it doesn't require the laser to be collimated. The laser only needs the be in collimation for the first adjustment, the focuser axial alignment, which is where you're adjusting the secondary to hit the primary. Since the tolerance for that is fairly large, a small laser misalignment is no problem. The tolerance for the primary adjustment is more stringent, however. A slightly mis-aligned non-barlowed laser could throw you off. Particularly because the light is travelling twice the distance for the primary alignment compared to the secondary alignment.

http://www.catseyecollimation.com/Newtonian%20Axial%20Tolerances.pdf

[ecosse]

Thanks for that tip and the link both very helpful

[malc-c]

That's why the Hotechs are a little more expensive, they come factory set and don't need collimation.... and because they self centre and are not affected by the two retention screws that normally hold the eyepiece in place

[Moonshane]

Laser collimation is extremely quick and easy, the videos are pretty accurate.

The whole process of collimation is an Astro myth that it's even slightly difficult. In short, a monkey could do it.

It normally takes me under a minute to collimate either of my (fast and supposedly difficult) Dobs.

In fact finding the tools to do it in my untidy van takes longer.

Setting up a GEM I find considerably more time consuming.

Regards Steve

Steve

this sums up my feelings re collimation. if it looks good down the eyepiece and the stars are round and the views sharp then people should stop worrying and get observing. I even check the collimation of my 6" f11 before each use. every now and again the primary needs a tweak. even the 16" f4 is not hard.

to the OP, make a collimation cap - i.e. something that fits the focuser and has a 2mm hole in the centre. you can use this to set the primary pretty accurately and the use the Cheshire on the primary adjustment.