[bloodhound31]

Originally Posted by Shiraz

a Powermate is a Barlow with 2 extra lenses that make it telecentric. there is no performance difference in this application, except that a Barlow can give you varying magnification whereas a Powermate is specifically designed so that it doesn't.

If interested in details, this is a good summary on Barlows and telecentric Barlows - http://www.brayebrookobservatory.org...BarlowLens.pdf

With a 618 camera, you need a final FNo of about f28, so you want about a 4x magnification Barlow or Powermate for your scope - just like http://www.astrobin.com/users/FranckIM06/

suggest a 3x Barlow with a short extension - that will allow you to vary the magnification to suit the seeing. If you do get a Barlow, buy a good quality one.

Originally Posted by Shiraz

yep, also fits into this at about 1/3 the price and the same result

http://www.bintel.com.au/Eyepieces-a...oductview.aspx

typical extension tube http://www.bintel.com.au/Accessories...oductview.aspx
but it doesn't work with a Powermate

I see. When you say, "vary the magnification to suit the seeing." What do you mean exactly?

Do you think the televue 3x barlow is good quality?