Barlows with wide view ep's for DSO's ?

[alowen]

Hi, my limited understanding is that wider ep's (25mm 30mm) give a lesser magnification. So for DSO's, 32mm ep's are popular, can you x2 barlow these to magnify them further ?

Thanks

Al

[alowen]

Anybody

[NGC 1502]

Hi Al, yes you can barlow a 32mm ep.

I have a 32mm TV plossl. However, when barlowed ( TV 2x ) the edge

of field is vignetted ( field stop not visible/looks fuzzy ) and the eye relief

is uncomfortably long. Better than too short eye relief, but it's hard to hold

your eye in the right place. It's why TV make the powermate, that sorts those

issues.

But it works if you can live with those problems.

HTH, Ed.

[alowen]

Thank you for that, it kinda makes sense. So basicaly, if you want to observe DSO's with any decent clarity you need a big scope and a wide field eyepiece ???

Makes sense now

Al

[RobH]

Hello Al.

I mostly use big 2 inch eyepices, my main one being a 26mm, and use a televue 2 inch barlow with it to double the power.

I find it very comfortable to use that way, no squinting down a small hole, and the eye relief works well, and there isn't any significant vignetting.

The amount of eye relief you need increases as you age, so this works nicely for both myself and my wife, being in our early 50's.

Cheers

Rob

[pvaz]

My wide field also haves extensive eye relief when barlowed. The solution was a powermate (sort of). However they are expensive and unless you are using expensive EPs, its cheaper to buy a 2nd EP.

[dph1nm]

The amount of eye relief you need increases as you age

Why? I know the maximum pupil diameter shrinks. but why would this affect eye relief?

NigelM

[RobH]

No idea, I'm not an optician, but I've read that it does on many occasions, and I have certainly noticed the truth of this from experience.

Maybe someone will come along and explain, I'd be interested to know too.

Rob

[pvaz]

Why? I know the maximum pupil diameter shrinks. but why would this affect eye relief?

NigelM

On my Nagler 31T5 it goes to twice, or more, the eye relief. I need to keep my eye about 2.5 to 3cm away from the lens and in line with EP axys so it won't blackout. I could never get along with it.

As I already had a 2" 2x TV Bigbarlow I got an addon for it, called panoptic interface that makes it work as a 2" 2x powermate.

The powermate also mantains the same focus point. So when you insert it the EP stays focused without adjustment.

But, as I said before, unless the powermate costs less then the final result, you will be better with individual EPs as it causes less stress on the focuser and generally provides a better view.

I only got mine cause with it's value I obtain a 15.5 Nagler and a 5mm Ethos, so it's a very large price difference to getting 2 EPs of similar quality.