Art. –Nr. TV-NAG-31
TeleVue Nagler 31mm Typ 5
Very good, just not perfect very close to the edges.
x-axis: distance from optical axis in °, y-axis: resolution in arc minutes
Apparent Field of View:
According to the definition of apparent field of view the angle is 82°. However, if you are going to calculate the true field of view by using the formula true field of view = apparent field of view / magnification you have to use 73° as high distortions are typical for these type of eyepieces.
Very good contrast.
Extreme cushion distortion towards the edges. Orange to brown colors very close to the edge.
Comfortable eye relief, but you have to stay at the correct position with your eye, otherwise kidney beaning occurs.
Solid and accurate manufactured. Pentax is somewhat more “noble”, but TeleVue is giving you the impression of an eyepiece to be used for the next 1000 years.
The apparent field of view is very impressive. Additionally the image quality if very good over the whole field of view (just the last few degrees are not perfect), and you can use it with fast telescopes also. However, these pros are to be paid by a mighty cushion distortion. Simply spoken the magnification increases towards the edges, and therefore the true field of view is somewhat less than expected if not looking into the details.
The choice between the Pentax XW30 and this eyepiece is simply up to you: If you would like to have the again increased field of view and if you do not find distortion annoying, then you will choose the TeleVue.