Televuw Powermate Barlows

[Grimmeister]

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 (http://www.williamoptics.com/telescopes/megrez90_features.php)
William Optics Flattener v4 (http://www.williamoptics.com/accessories/flattener4_features.php)
Canon EOS 600D (http://www.canon.com.au/For-You/EOS-Digital-SLR-Cameras/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:D)

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

Cheers

Anthony

[traveller]

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]

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