Barlow technique for collimation

Ok, I’m going to start by assuming that everyone has read the Sky and Telescope article on the Barlow technique for collimation of a Newtonian.

My question is: Can a Powermate be used instead of a Barlow? I have a 2” Powermate but not a 2” Barlow (My laser is 2" kendrick). And I really don’t want a 2” Barlow if this is the only thing I’m going to use this for unless I can pick one up dirt cheap ;-).

Thanks in advance
David Pope

David,

My guess is no. My 2.5x powermate does not work as the laser spot is too small on the mirror to cover the center spot donut thingy. My 5x powermate makes a bigger spot and might work, but my 3x barlow works much better. The reason I'm guessing that the 2x powermate won't work is that it is simialr to the 2.5x powermate in that the lens pairs are telecentric (I don't know what that means, but I did stay at a Holiday Inn Express last night . It probably won't make a big spot on the primary as the laser will not diverge as it does with a barlow.

Apogee sells a 2" barlow for $75. Might be considered dirt cheap. I guess it depends on how expensive your dirt is.

Clear skies,

Tom

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