Televue Powermate or Explore Scientific Focal Extender

[Aussie Dave]

Hi all. I'm heading down the road of buying a 1.25" Televue Powermate or a 1.25" Explore Scientific Focal Extender.

I'll be using it for imaging lunar and planetary with a Celestron Nexstar 8i SCT. The camera that I'll be using will be the ZWO ASI174mm.

I've been reading up about both of them for some time now and both seem to be a good investment but consensus leans towards the Televue Powermates which will cost a little more. I'm looking at the 2.5x 1.25" Televue Powermate or the 2x 1.25" Explore Scientific Focal Extender.

I have a few questions...

Will I notice a big difference in imaging using a 2.5x 1.25" Televue Powermate or a 2x 1.25" Explore Scientific Focal Extender to a standard 2x 1.25" Barlow? I've found standard Barlow's to be useless so I guess I have already answered my question here.

Should I be looking at a 3x or 4x Powermate or Focal Extender or will that be pushing the optics too far?

Are the 2" Powermates or Focal Extenders better for imaging than the 1.25"?

 

Any comments, suggestions, examples will be greatly appreciated, thanks.

 

 

[michael.h.f.wilkinson]

I have both the TeleVue 2.5x PowerMate and the Meade Series 5000 2x TeleXtender, which is apparently (near) identical optically to the ES Focal Extender. Both perform very well in my Celestron C8. Both are better than standard Barlows, in particular in keeping image scale near constant irrespective of filter wheels etc in the optical path. The 2.5x PowerMate is a better match for the ASI174MM because F/25 better matches the fairly large pixels of the ASI174MM. Under poorer seeing I might switch to the 2x TeleXtender, but that is mainly used with my ASI224MC for planetary imaging. On the moon, you can get some spectaular results with the  2.5x PowerMate, ASI174MM and C8:

[michael.h.f.wilkinson]

Forgot to add: I have a 3x TeleXtender as well, but that spends rather more time in the case. It is of some use in lunar imaging with the APM 80mm F/6, where I get a useful F/18 which matches the ASI224MC well, but in the C8 I haven't used it very much. I might use it on Mars with the ASI174MM, but I am not at all sure it will get more detail than the 2.5x PowerMate. A 4x or 5x are way over the top for the C8

[Aussie Dave]

Cheers Michael. It's strange as some people using a 2X Barlow and much smaller scope get much better results than myself without using a Barlow. A good example of that was recently posted in the Small Scope Lunar Challenge thread.

I think I'll be happy with either and will get better results to work with.

I've been using extension tubes without a diagonal recently which seems to be working well but would like to do higher magnification work without degrading image quality.

[Aussie Dave]

7 minutes ago, michael.h.f.wilkinson said:

Forgot to add: I have a 3x TeleXtender as well, but that spends rather more time in the case. It is of some use in lunar imaging with the APM 80mm F/6, where I get a useful F/18 which matches the ASI224MC well, but in the C8 I haven't used it very much. I might use it on Mars with the ASI174MM, but I am not at all sure it will get more detail than the 2.5x PowerMate. A 4x or 5x are way over the top for the C8

I was thinking of the 3x but I don't think conditions here would justify buying one. I don't want it sitting for the rest of it's life in an EP case. I'm thinking 2.5x max and as you say it would be better suited for the ZWO ASI174MM with the C8.