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BARLOW LASER COLLIMATION


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Has anyone used the above method on a Skywatcher Heritage 130p, I have tried using a Tal 3 x barlow but only got a red glow on the face of the Antares type laser collomator. When looking inside the tube it appears that the centre mark ring is reflective, so no shadow shows on the laser screen. Is the only answer to replace the centre ring.

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I dont think your meant to see a shadow on the laser screen, just the returned laser beam. You then use the collimation screws to move that returned beam to the centre of the laser screen and hey presto.

When you look in the tube you should also see that the red dot is hitting the mirror. It should dit inside the mirror centre mark. If the laser beam is not a nice dot onthe mirror (but rather a large splat) then I would ditch the barlow as a laser will be accurate enought without it.

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I have used this method and the return shadow is seem on the laser face but this might depend on the focal length. with my 1600mm focal length 12" dob it used to basically fill the angled 'screen'.

when trying it, make sure the laser is diffused and covers the donut. then try moving the collimation bolts around and little and you may then see the dark shadow of the donut on the laser face.

if not then you may have to create a small circle of card with a 3mm or so hole in the centre and put it in the end of the barlow. you can see the shadow on that but I never needed to do this and found it a bit tricky.

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It may be that the 3x barlow is the issue by diffusing the return beam so much that the donut shadow is lost. I use a 1.6x barlow with my 10" F/4.8 and it works fine - the shadow of the donut is projected onto the angled face of the laser collimator which allows fine adjustment of collimation.

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agreed John, I think that supports my suggestion about focal length too as it effectively trebles rather than doubles it?

I think so Shane - we are saying the same thing in slightly different ways :)

To tms48:

It might be worth investing in a cheap 2x barlow for this purpose - optical quality does not matter much here.

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