Powermate x4 focus

[gthomas]

I've just bought a Televue Powermate 2" x 4 and have been trying it on both a 750mm and 800mm focal length Netwonian in daylight.

Very impressive performance obviously. However, I had to use between 50mm and 90mm of extension on both a 25mm eyepiece and a Canon 450D in order to get any semblence of focus at distances of 400 to 800 yards. Given that the Powermate itself is between 75mm and 150mm in length this seems to be a heck of a lot of extension!

Am I misunderstanding something here? Is this normal with Powermates? Any comments most welcome.

Cheers

Glyn

[John]

They are designed to be used an what is effectively, infinity. 400-800 yards is too close.

[gthomas]

So you're saying that when focussing on Jupiter say, the extensions will not be needed?

Glyn

[gthomas]

Well against all reason and forecast it is actually clear tonight and I can confirm that I need 50mm of extension to focus with both eyepiece and camera. I guess I can live with that,

Just seen my best ever M31 through an eyepiece

Glyn

[alan potts]

It is a big difference 400m to infinity. I focus on a tree top to check the scope finder set-up, I never get scope focus with a long eyepiece, there is not enough backward travel in the drawtube. But the same Ep aways reaches focus on a star with room to spare.

Alan

[gthomas]

Well I've always used the local tree tops for testing purposes before and never had to add extension. Ah well

Glyn