Quote:
Originally Posted by SkyWatch
Hi John: I notice your scopes are all pretty fast, and you are right- that can make a big difference. I use mine with my refractors: a Stellarvue 70ED (f6) and a Tak TSA 102 (f8).
You have some nice scopes there!
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Hi Dean,
The predominant aberration I noticed with the 3-6 Nagler zoom was field curvature. Referring to my testing notes on a single bright star (Achernar) when used in my 10"/f5.3 newtonian (without paracorr), I recorded, "The star image bloated in size from 60% of the way off axis, but stayed circular to the field stop". This indicates straight field curvature as a result of the scope / eyepiece interaction. A newtonian has minor inherent +ve field curvature and based on what I observed I believe the 3-6 Nagler zoom also has inherent minor +ve field curvature. The 2 positive field curvatures compound and manifest in the observed field curvature. A refractor on the other hand has inherent -ve field curvature and when an eyepiece having slight +ve field curvature is used in a refractor the two cancel out and give a flat field view. Consequently the 3-6 Nagler will perform superbly in a refractor, less so in a newtonian. Whilst I haven't tried it with the 3-6 zoom I am sure that using a paracorr, which has inherent -ve field curvature, with the 3-6 zoom would result in a nice flat field view when used in a newtonian. This is the case with the 14mm and 20mm Pentax XW's which both have +ve field curvature. Aside from the field curvature and the shorter eye relief the 3-6 Nagler performed very well.
Tomorrow when I am at my notebook pc I will attach to this post the testing notes and scores on all 5 eyepieces when used in my 10"/f5.3 newtonian when aimed at a single bright star only (Achernar). The scores are not indicative of each eyepieces performance on any other target type, or in any other telescope. I can't do it at the moment from my tablet as I need to convert the file from excel to pdf format.
Cheers,
John B