Laser collimator Vs Barlowed Laser

[Dodge]

Hi guys and girls,

Been playing with my recently acquired laser collimator. I spent what seemed like hours collimating the laser, and I've finally got it as close as I can detect.

Plugged it into my scope (SW Heritage 130P F5) and collimated with the laser, and then tried the barlowed laser method - it's giving me pretty different results.

If I centre the 'donut' on the barlowed laser method, when I replace it with just the laser, the spot is about half way off the target.

Is one method deemed more accurate than another, or is it just suggesting I've not yet perfectly collimated the laser?

I've tried star testing, but with the recent unstable atmosphere it's been a challenge. The airey discs I can detect seem to suggest the laser on it's own was generating close enough results. I've not yet tried star testing with the barlowed laser method.

Cheers!

[John]

The laser collimator needs to be collimated accurately enough so that the laser dot rotates more or less on the same spot at a distance of around 25 feet or so.

You can then use just the laser collimator to adjust the secondary mirror so that the laser dot is right in the "donut" on the primary mirror.

I then add a barlow to adjust the primary mirror tilt. The final test is a star test.

This is quite a useful guide:

Astromart Articles - Barlowed Laser Collimation Made Easy

[Rustysplit]

I find that the barlow/laser combo works great!

[Mr Flibble]

When collimating my scope, the position of the laser doesn't get affected by the use of a barlow - it just gets converted from a dot to a circular smudge.

If the use of a barlow affects the laser position when collimating your scope I would guess that the laser itself is not collimated correctly, or maybe even that you have some play in the focuser?

[Dodge]

When collimating my scope, the position of the laser doesn't get affected by the use of a barlow - it just gets converted from a dot to a circular smudge.

If the use of a barlow affects the laser position when collimating your scope I would guess that the laser itself is not collimated correctly, or maybe even that you have some play in the focuser?

I may not have explained myself well enough - the dot converts to the circular smudge and is still centred on the primary, but if I complete collimation using the barlowed laser, and then just use the laser on it's own, it shows as collimation being out.

The focuser is a helical one, and there's some play in it - but I generally wind it in so it doesn't move whilst collimating.

Perhaps I should have bought a Cheshire!

[John]

I understand that one of the benefits of the barlowed laser method is that it's not affected by collimator play in the focuser.