First light - Revelation 12" Dob.

Im in Swords, if thats close enough.

Glad you are happy with it

I look forward to getting the 8" version

I've read recently that collimaters (lasers, cheshires and others) are ok for getting you close, but unless they are extremely well made, you're wasting your money.Cheers

Dave

Hi Dave,

I bought a laser collimator from telescope house web and after managing to completely cock up my collimation I phoned up and was told they are only for rough alignment. So I wasted my money and made my scope worse. I could see the atrificial star design of collimator being useful though.

Simon

Simon - that's what I read recently.

Its a shame that 'laser collimaters' are seen by beginners as the end to their collimation problems.

There may be laser collimaters out there that are precision made and could possibly help with the initial alignment. But then if ou stick a precision instrument into a non-precision focuser (which face it, unless your paying many thousands for your scope, it is unlikely to be precision machined and assembled), your pretty much onto a loser.

As an example, it turns out that an old polar scope I had fits perfectly into my (precision machined) astrophysics mount. Cool I thought... But its clear that the polar scope is not machined to the same standards as the mount - it can't be calibrated and is a tad wobbly in the screw threads. However, I couldn't afford the precision machined AP polar scope (about 300 dollars if I recall).

But - and here's the hopeful bit - the polar scope gives me a pretty good rough alignment then I just do the drift method - voila - good polar alignment.

So what's this to do with collimation? The same principle really. You can do the rough primary/secondary alignment using a cap that fits into your eyepiece holder (focuser). You drill a small hole in the center of the cap and align the mirrors using the central dot on the primary (which most scopes seem to have these days). The crucial collimation is done using stars - artificial or otherwise. I read the other day that a good artificial star for collimating during the day (in a shed or the house) is to shine a torch on a christmas tree bauble situated about 20-30 feet away. But I know manufacturers are supplying other "artificial" stars - at a price...

The start test at night is the ultimate test though.

Cheers

Dave McD

I assume thats what they mean when they use Polaris. When I focus in and out, the top right corner of the star becomes flat. Its definitely not circular anyway. Where do I get a cheshire?

Polar alignment (in the Northern Hemisphere) relies on Polaris for an initial rough polar alignment. But since Polaris is not exaclty at the celestial pole, you need to adjust the mount - usually by the drift method or you can use sophistcated software.

Of course, good polar alignment only helps if your mount has motor drives to move it at sidereal time And polar alignment really only applies to equatorial mounts.

Precise polar alignment is really only required for long exposure astrophotography.

As for the cheshire, I'd leave it for now. I've never used one so I'm not sure how much use they are - I've certainly heard that they can help. But for the price, I'm not sure you'd get better results than with a cap-with-a-hole and a star test...

A flat edge to a star definately sounds like miscollimation anyhow. But it can be soreted out with a bit of tweaking.

Cheers

Dave