Powermate 2x with a big refractor & CCD?? Is it going to work?

[Tim]

So here's the plan:

150ED > Flattener > 2x Powermate > OAG/Filter Wheel/CCD

Extending the length behind the PM is unlikely to affect things much going on Televue's info ( http://www.televue.com/engine/TV3b_page.asp?id=53&Tab=_app )

But I am wondering about getting the PM in the right place behind the flattener. The distance between the flattener and the CCD is meant to be 100mm.

It will make the Esprit 150 f14 with a focal length of 2100mm. I have certain targets in mind that I am keen to try out with this config, but want to get it as flat as possible.

Any thoughts or experiences with a config like this?#

Thank you

Tim

[michael.h.f.wilkinson]

Given the nature of this telecentric lens, I would guess that putting the PM between the flattener and CCD would not affect curvature that much. Difficult to be sure. Maybe trial and error is the only way.

One other thing: If you take a C11 with 0.7x reducer you end up with much the same focal length, but FAR faster. What is wrong with using that?

[Tim]

There's nothing wrong with the C11 I have at f7, but there is a LOT of glass in front of the CCD and two mirrors too. I am interested to see how sharp the view is in comparison. I am also thinking about becoming a one scope family with the Esprit 150 as the Daddy.

How much slower in real terms would f14 be than f7? The step to f7 from f10 didn't seem to make much difference over long exposure times from what I could see.

Besides, I like to be different

[michael.h.f.wilkinson]

F/7 is four times faster than F/14, and an 11" scope tends to be a lot sharper than a 6".

[RikM]

I get much better detail with my 10" Newt compared to my 6" version of the same.

You realise you've opened the reflector vs. refractor box