Howie Glatter TuBlug question...

[Marcus10 (Marcus)]

Hi

I have a question about the alignment of the primary mirror using a TuBlug attachment. I'm using a 2" single red beam 635nm Howie Glatter.

When I'm collimating the primary, there are two things which appear in the window of the TuBlug. The first is the donut shape of the primary centre spot marker. The second is a series of red concentric rings. It looks similar to the first picture on the link below.

http://www.dobstuff.com/centerdot.htm

My question is whether the red concentric rings should match up exactly with the centre spot reflection. Currently, when I collimate the primary, I adjust the primary to ensure the donut shape (i.e. the centered marker on the link above) is exactly centered in the hole in the TuBlug window. However, when the donut is centered, the red concentric rings are off centre (again, as in the pic above). Perhaps I am not understanding what I am seeing but should both the donut and red concentric rings be exactly centered over the hole?

I think my scope is accurately collimated as everyone looks accurately adjusted when using a cheshire eyepiece with crosshair. But the issue above is confusing me!

Can anyone help with this?

Thanks

Marcus

[Sarge (Rod)]

Marcus,

I don't know what scope you have, but this link may be of assistance, loads of info.

HOWIE GLATTER’S LASER COLLIMATOR PAGE

http://www.collimator.com/coltext.htm

Rod

[gb_astro]

Marcus as far as I know the displacement of the red concentric rings is not important.
It indicates a bit of slop or misalignment of the Tublug in the focuser.
but apparently this does not affect this barlowed laser technique much.
The Glatter laser and Tublug is a long and heavy combination and I guess it will sag in most focusers.

Centring the shadow of the donut is the important thing.

You should find that you can centre the red concentric rings by
pushing the laser/Tublug around a bit while it is in the focuser.
At the same time you should see that the donut does not move much at all.

gb.

[mswhin63 (Malcolm)]

Originally Posted by gb_astro

The Glatter laser and Tublug is a pretty heavy combination and I guess it will sag in most focusers.

Interesting quote could be the answer to most collimation of some heavy cameras by loading the collimator to match the weight of the camera. This would give accurate collimation once the real thing is inserted.

[Marcus10 (Marcus)]

That is very useful and is an issue that has had me a bit perplexed for a while! Thanks for your help

[gb_astro]

Marcus, for a more detailed answer it might be worth asking
this question over at the Cloudy Nights reflector forum.
I know Howie Glatter himself often responds to questions there.

gb.