Powermate vs Glass Path Corrector for Binoviewing

[niallk]

Hi,

The last time I was out, I was really dismayed to find that I couldn't reach focus in my recently acquired 15" (although I realistically understood that this would be the likelihood).

While I had started Googling aluminium tubing suppliers to make a second set of trusses, I decided to try out my binoviewer in my 2.5x PM to see if it would work next time I was out.  I had been thinking about it, and suspected that it just might work...

So last night, just before I wrapped up, I destroyed my night vision and went inside and got my binoviewer + 15mm plossls, and put into the PM (no GPC).  Targeted Jupiter and ... BINGO!! focus   Delighted!

Just wondering if many people out there use a PM instead of a GPC for binoviewing in a Newtonian??

I'm not sure if any/what potential drawbacks are involved.  The image looked reasonable to me, but I seemed to have a little bit of thermal effects in the binoviewer - it came from a warm room, and I had to head inside to the family so didn't get to let it cool down.  I also have two of the 'cheapest standard issue with a new scope' SW 25mm eps - and they too focused (heresy: I get great views in the bino with these ~Eu25 eps!  Fantastic on the moon in my 250px).

Anyway, just thought I'd ask - and I guess there is also the possible suggestion that someone buying a binoviewer for a Newt (I originally got it for my 250px) - you just might be able to save Eu85 on a GPC if you have a PM!

I'd certainly welcome comments from people if they've gone down this path - eg any gotchas.  The TV link below seemed to suggest to me that physical distance in the binoviewer could be tolerable given the way a PM works - the 'Magnification vs Focus Position from Top Surface' graph...

Cheers,

-Niall.

http://www.televue.com/engine/TV3b_page.asp?id=53&Tab=_app#.VOMIHrHFJD8

[JED-E3]

Hi, yes I use a 2.5x powermate with t adapter screwed directly onto my Baader maxbright binoviewers, it allows me to reach focus with my 12" Revelation dob and gives great planetary views. As you say the magnification is something less than 2.5x probably nearer 2x.

James.