Equinox 80 + TV Powermate ???

[OzDave]

Hi,

I'm thinking about getting a Televue Powermate for use with my Equinox 80. The intended purpose would be to image smaller targets like globular clusters, which would normally be lost in the wide field of the Equinox 80.

I'm wondering if a x5 Powermate is likely to work with this scope or is this just wishful thinking?

My other scope is a Skymax 127, which has 3x the focal length of the EQ80. It would theoretically be better for the smaller targets, but I don't think the optics are as good as the EQ80 and the focuser is pretty difficult to use.

So would a Powermate help me, or should I really be looking for a different scope for this kind of thing?

David

[RT65CB-SWL]

Hi OzDave,

Personally I think the TeleVue 5x Powermate is overdoing it with your scope. What eyepiece(s) are you using?

I have a TeleVue Ranger (70mm), and it too is a wide field refractor. I have used my AstroEngineering 4x Imagemate with my TeleVue 8mm Plossl and it is to much.

I still beleive in the 50x per inch.

[OzDave]

Hi, this is not for observing, it's for imaging smaller targets. So it's a camera I'd be attaching rather than an eyepiece. Maybe the 50x rule still applies here?

Maybe I'd be better off with a larger aperture Newt for targets like M56.

David

[Dave Smith]

I used a 5X powermate with my 102mm refractor (f8.8) using a SPC900 webcam and it was fine. I am hoping to use it with my DMK21 for the Moon.

Dave

[Dave Smith]

Have you seen John's pics with a 5x barlow and an 80mm scope?

http://stargazerslounge.com/imaging-lunar/114699-sept-21-22-lunar-fun.html

Dave

[jgs001]

The problem with something like that on deep sky, you need longer exposure times anyway (you can get away with this sort of thing on lunar and planetary as they are really bright anyway). With a x2 barlow, for instance, with the same setup, you need to quadruple the exposure time (I think I'm remembering this correctly). So with a 5x barlow, you need to multiply the exposure time by a factor of 25 to get an equivalent exposure (all other settings being equal). I have imaged some globs with a 2x barlow on my C80ED and used 5 minute exposures, and that worked, but only because I'm able to track for long enough. Bear in mind that as you increase the effective focal length, you also increase the need for accurate tracking.

Thanks Dave

[OzDave]

Hmmm, ok, so maybe I'd want to limit it to a 2x or 3x barlow as otherwise the exposure times will get excessive. I can probably cope with 5 minutes guided.

But it sounds like if I want to get more resolution to resolve the cores of the globs, I'm going to need more focal length, but more aperture to go with that to compensate. Perhaps I should be considering something like a SW 250P DS Newt?

David

[jgs001]

but... then you'd also need a bigger mount, I'm not sure the eq3-2 would cope with a 250 newt... I'm not sure my heq5 would.... and you'd also want an MPCC to correct for coma.

[OzDave]

Yep, this is all true. I am planning to upgrade to a HEQ5 anyway, assuming this will cope.

For now, I guess I'll give my 2x barlow a shot on the EQ80 and see how that goes while I dream up an excuse to buy a 3rd scope and perhaps a way to get it smuggled in.

David

[jgs001]

Good luck smuggling in a 250mm monster

If it works, please do tell how you managed it. The 2x should work, and you can always drizzle the image in DSS to increase the scale a bit.