New Nirvana focal length - 13 mm

[Ags]

Looking forward to reading your thoughts. 

[Louis D]

1 hour ago, Mr Spock said:

Done. I'll do a full review of them once they arrive and get some use 👍

Way to take one for the team!

[Mr Spock]

Arrived this morning. Usual speedy service from FLO 👍

First impressions only - full review to come later. Build quality appears quite good, excellent for the price.
In the 102mm on solar.
The 16mm is susceptible to field curvature. You have to refocus to get the edge in focus, but, it is sharp right to the edge when focussed. This field curvature isn't evident when using the x2.5 Powermate however, so, it's probably the scope.  Nice, sharp views though.
The 10mm is just as sharp, and with no field curvature - so sharp right to the edge - nice!
Both eyepieces revealed granulation. They are a lot better than I was expecting. Not bad at all and definitely good value for money. I don't have anything of this focal length in my 'collection' but the 16mm gave images just as good for sharpness and contrast as the 17mm LVW,

As with Naglers, you can't really get the whole field of view in, you have to move your eye around. Eye positioning is fine for this type of eyepiece with a little blackening if you move your eye too far.. Some kidney beaning was evident with the x2.5 Powermate though.

The only real disappointment is they aren't par focal - close, but not quite. The fine focuser need a one fifth turn inwards from the 16mm to the 10mm. 

[Ags]

That's what I remember from my N16 - very strong field curvature, much more than a wider eyepiece like an ES 24/68 would show. I could see the issue in a Mak, so I blamed the eyepiece.

Pleased to hear the 10 mm at least does not exhibit this - I'm tempted to replace my rather bulky Speers WALER 4.9 and 13.4 mm with the Nirvanas.

Edited September 17, 2022 by Ags

[Don Pensack]

The 16mm biggest aberration at the edge is astigmatism., even at f/10.

The center is sharp but this deteriorates fairly quickly outside the center 25%.

Edge stars appear defocused, but cannot be accurately focused because of astigmatism in the star images.

I tried it in f/5.75 (coma corrected) and f/7.  It was better at f/7, but I think it is better in scopes >f/10, like Maksutovs or Classical cassegrains.

Edited September 17, 2022 by Don Pensack