ED80 Field of view with Powermate

[dugnsuz (Doug)]

Hi all,
Just purchased a 2" 4x TeleVue Powermate from an IIS member (thanks Lars).
Intend to use it for visual and imaging work. I've ordered the T-ring attachment from Bintel and will be ready to go soon.

Question is at 4x the prime focus of my Skywatcher ED80, what FOV will I obtain and what objects will be best for imaging?
Will I be moving into planetary territory?
Cheers
Doug

[[1ponders] (Paul)]

It depends on the camera you are using Doug. But using a 4x powermate I assume you are going to be doing planetary/luna imaging with a ToUcam or similar? 3.8x5.1 arcmin would be the field of view with a pixel Resolution of 0.48.

It would be too slow for Deep Sky stuff at f/30

[dugnsuz (Doug)]

Originally Posted by [1ponders]

It depends on the camera you are using Doug. But using a 4x powermate I assume you are going to be doing planetary/luna imaging with a ToUcam or similar? 3.8x5.1 arcmin would be the field of view with a pixel Resolution of 0.48.

It would be too slow for Deep Sky stuff at f/30

I'm kind of walking backwards into a dark room with this one I think!!
I'll be using a pentax DSLR with it.
Doug

[[1ponders] (Paul)]

Then you would want a focal reducer not a "focal lengthener" though it would be handy for the moon for closeups of craters. Even then it is unlikely that you would do a better job than using a webcam.

The upside is you would have a larger field of view @ 21.7x32.5 arcmin (assuming your chip is 15.2mm x 22.7mm and has 7.4 micron pixels)

[[1ponders] (Paul)]

For DSO using the Skywatcher (native f ratio f/7.5?? and with canon 300D, FOV = 86.7 x 130.1 arcmin and pixel resolution of 2.54 arcsec/pixel (pretty ideal actually)) using a meade/celestron 6.3 FR will reduce your f ration to f4.7 and increase your FOV to 137.7 x 206.5 arcmin with a pixel resolution of 4.03 arcsec/pixel (oversampling but not a real problem, better to oversample than undersample which would happen with the powermate with DSOs)

[dugnsuz (Doug)]

Originally Posted by [1ponders]

For DSO using the Skywatcher (native f ratio f/7.5?? and with canon 300D, FOV = 86.7 x 130.1 arcmin and pixel resolution of 2.54 arcsec/pixel (pretty ideal actually)) using a meade/celestron 6.3 FR will reduce your f ration to f4.7 and increase your FOV to 137.7 x 206.5 arcmin with a pixel resolution of 4.03 arcsec/pixel (oversampling but not a real problem, better to oversample than undersample which would happen with the powermate with DSOs)

Where does the focal reducer go in the optical chain?
? screw into silver focus tube before visual back?
Cheers
Doug

[[1ponders] (Paul)]

You get an Orion Prime focus adapter from Bintel ($59 https://www.bintelshop.com.au/Images/Stock/7182X.jpg ) screw the 2" silver barrel out and then screw it into the female side of the FR. Then screw the male side of the FR into your camera T adapter and attach your T adapter to your camera and away you go. Remove the 1.25" adapter that is in your focuser tube and the Orion 2" tube slips straight in.

[[1ponders] (Paul)]

You will find though that the stars around the edge of the field of view will be triangular, but you will reduce your imaging time for a particular object by about 1/2 for any given ISO setting. It will also appear smaller

[JohnG (John)]

I havn't tried it yet but I have one of these:

http://www.williamoptics.com/accesso...r_features.htm

It is supposed to be good for up to 90mm scopes, got it for the 66mm field guidescope but thought it might also be usefull for my SW ED80 in my field setup as well.

Like I said, havn't tried it yet.

Cheers

[[1ponders] (Paul)]

I look forward to a review John. While the SCT reducers are "ok" a dedicated refractor reducer that doesn't cost the earth would be a nice addition to the image draw.

[JohnG (John)]

Hi Paul

I think it was about $140 something US, it has both the SCT flange for the WO 66SD and a 2" nose for standard focussers, it is a dedicated refractor reducer/flattener, I like the distance to film plane specs for a DSLR.

Cheers

[[1ponders] (Paul)]

It's very tempting John. I just checked the site out $149 with the Aus $ at 0.86 atm it is very tempting.

[dugnsuz (Doug)]

FYI Frontier Optics has one in their clearance section for $150AU.
Go get it!!!!!
Doug

[JohnG (John)]

Originally Posted by dugnsuz

FYI Frontier Optics has one in their clearance section for $150AU.
Go get it!!!!!
Doug

That is the previous model, has been replaced by the one in the link I provided.

Cheers

[dugnsuz (Doug)]

Thanks JohnG,
New model looks a nicer piece of kit too
Cheers
Doug