Televuw Powermate Barlows

[Grimmeister (Anthony)]

Hello Fellow Astronomers and Ice in Spacers,

I am seeking some guidance from those that have had experience with the Tele Vue Powermate Barlow lenses as I was considering purchasing one for my imaging rig for Astrofest 2012. I would like to know how you all feel one of these would perform in my specific set up.

I have the following set up and I get very nice flat images that are a very wide field of view (I can easily fit 90% + of Eta Carina Nebula in one frame).

Equipment:
William Optics Megrez 90 F6.2 Telescope
William Optics Flattener v4
Canon EOS 600D

With this combination as mentioned I get good flat images, I would however like to include a Barlow in the image train to narrow the field of view and increase the pixels per arc second resolution when trying to image smaller objects such as Galaxies.

I was looking at either the Powermate PMT-2200 (2” 2* Barlow) or the PMT-4201 (2” 4* Barlow).

So a few questions:
A) Should I get a 2* Barlow to double the Focal Ratio and crop the images if required or get a 4* Barlow to get closer to smaller objects?
B) Will a 4* Barlow be too much of an increase in Focal length for my Aperture of scope to feasible for imaging.
C) If I use a 4* Barlow will I still need the field flattener at the new focal length?
D) If I use a 2* Barlow and I use the Field Flattener are they likely to be compatible and still give me a flat field of view?
E) Do you think there is a better alternative out there for imaging that would suit my equipment?

I think that probably covers it and any guidance would be most appreciated (I won’t hold you accountable for your advice)

Lastly thanks in advance for your thoughts and time to comment.

Cheers

Anthony

[traveller (Bo)]

Hi Antony,
I have a 2.5 and a 5X powermate and a T-ring adapter which you will need for DSLR work.
Powermates are different to Barlows and some would say superior. Anyway, let me know if you want to borrow them. I will be happy to post them out to you for a "try before you buy".
Cheers,
Bo

[Grimmeister (Anthony)]

Hi Bo,

That's a very generous offer, but I do not trust our postal service enough to ensure safe transport and delivery of goods like these and they cost far too much to risk it.

I suspect the powermates would be the best option as they are parfocal and apparently return the light path back to the original angle it was received so a field flattener should still do the task it was designed for. I guess now I really need to think about focal length to aperture to see if the 4* would be too much, I don't have much experience here hence some of the later questions.

Cheers

Anthony