Barlow or Ep for power?

[caleb]

Hey everyone, its big news at IIS as my scopes back in action.

Now, what I'm looking for is some more power. I have a 10mm & 20mm Plossl ep but I also have a dodgy plastic 2X barlow to make 200X power.


I'd like to add that I'm considering a DSLR to connect via a T-mount so this is where the barlow would come in.
So Should I buy an ep around the 4-6mm mark or a high quality 2-3X barlow?

[Gallifreyboy]

The televue powermates although expensive will do everything you want and be better quality for astrophotography than a barlow. There is even an adapter for the powermate available that screws in and acts as the T mount for the DSLR.

[caleb]

So this is an eyepiece? And how much is this adapter, are they available for 6mm.
Actualy, to think of it 6mm won't go great with an SLR and a lens..

[Gallifreyboy]

The 1.25" powermate are 2.5X and 5X, I can't link to the Bintel page for you but there is a lot of info, prices and theory on powermate there

[astro744]

Have a look at http://www.televue.com/engine/page.asp?ID=237 and http://www.televue.com/engine/page.asp?ID=42

for notes on various imaging methods and on Powermates.

A Powermate is a 4 element Barlow and is available in 2x & 4x (both 2") and 2.5x & 5x (both 1.25").

If you use a Powermate for imaging you do not need an eyepiece. Just get the appropriate Tele Vue Powermate T adaptor and connect direct to DSLR. A Powermate for visual does need an eyepiece and works similar to a Barlow with some advantages the main one being the cone of light the eyepiece sees remains the same as if there was no Powermate. Eye relief is maintained and there is no vignetting that can happen with some short Barlow and eyepiece combinations.

Note using Powermates extends the focal length of your telescope significantly to increase image scale. It is used for planetary imaging and Lunar close-ups.

Eyepiece projection photography can acvhieve the same by using an eyepiece inside an eyepiece projection adaptor which has 1.25" barrel at one end and T thread at the other. The eyepiece sits inside and the magnification factor is determined by the eyepiece focal length used and the distance from the eyepiece to the film plane. Note the eyepiece overall diameter has to be small enough to fit inside the projection adaptor and this usually means using a Plossl or Ortho type of eyepiece which are ideall since they are usually very sharp on axis.

[Matt Wastell]

I do not have the technical background but a good Powermate will allow you to still use all of your current eyepieces - I know that my Powermate x2.5 is far superior to any barlow that I have owned and they are a must for imaging planets.
Buy the Powermate.

[Ian Robinson]

Very short focal length eyepieces while nice , are hard for some people to see through .... exit pupil and eye relief ???

I'd be inclined to use a medium length nice quality eyepiece and a good quality barlow to get the extra magnification if I wanted it.

Imaging .... I've never tried imaging via an eyepiece .... you do realise that the eyepiece has to produce an image that's sharp and has a very large radius image plain at the registry distance of the camera ....

It's doable but hardly useful IMO as you are limited to the brighter objects - moon, some planets and not much else unless you've a good solar imaging energy rejection filter and or a very narrow bandpass Halpha filter say.