NPL 30mm for fast scope?

[mark81]

Hi all,

The ES 24/68 I have been using in my ST80 over the last few months was borrowed from a friend and has now gone back 

I need to pick up a new low power EP for about £50 and was wondering if NPL 30mm would be any good?  I do like the BSTs but fancy trying out something different...

Thanks 

Mark

[John]

I've owned and used the Vixen NPL 30mm a fair bit. It seemed to work quite nicely with my F/5.3 dobsonian as I recall although there was a little field edge astigmatism showing. Nothing too distracting though. Depending on the darkness of your skies, you might find that the exit pupil of 6mm that the 30mm NPL gives in your ST80 shows a paler background sky than the 24mm / 68 degree eyepiece did.

I compared the NPL 30 with the Baader Classic 32mm sometime back. I preferred the Vixen of the two:

 

[Piero]

Mm..I bought one for my TV60 in the past, but unfortunately it didn't work well at all. There was a considerable amount of astigmatism and the last 30% of the field was simply 'washed'. It was fine on axis instead.

Now, whether mine had an issue, or the eyepiece doesn't work well in short telescopes (the TV60 has a f.l. of 360mm which causes a fair amount of field curvature), or a combination of the two, I have no idea. What I saw was astigmatism though, not field curvature, as there was no way to focus the stars far off axis.

Shame because the eyepiece is comfortable and light. The front lens is large too. 

Personally, I would use that eyepiece only with long slow telescopes.

[Louis D]

1 hour ago, Piero said:

Mm..I bought one for my TV60 in the past, but unfortunately it didn't work well at all. There was a considerable amount of astigmatism and the last 30% of the field was simply 'washed'. It was fine on axis instead.

Now, whether mine had an issue, or the eyepiece doesn't work well in short telescopes (the TV60 has a f.l. of 360mm which causes a fair amount of field curvature), or a combination of the two, I have no idea. What I saw was astigmatism though, not field curvature, as there was no way to focus the stars far off axis.

Shame because the eyepiece is comfortable and light. The front lens is large too. 

Personally, I would use that eyepiece only with long slow telescopes.

My 32m GSO Plossl does better than that as can be seen in my recent photographic field comparison below:

Admittedly, I'm using a TSFLAT2 field flattener ahead of my 2" GSO dielectric diagonal on my AT72ED to flatten the field to near perfection for eyepieces that focus at the shoulder.  The Rini MPL below it is a 5 element design with no field stop.