|
Knightrider,
There is something to remember about plossls - it is a nearly 160 year old design optimized for slower Newts than available today, and it does not use the same exotic glass types available today - there will be some performance "difficulties" compared to many contemporary designs, including modestly priced ones. Even those plossls made to higher standards with really good quality optical glass and the very best coatings, you may notice some aberrations.
Your review of that 25mm HD-60 is a very good one! You've come to recognize the difference between coma and astigmatism, and by your account astigmatism is really well controlled. Coma is not a flaw in the eyepiece, so don't think it is something to dismiss the eyepiece over.
I have no experience with the HD-60 line. But your review is an excellent help if I was looking for info on how that particular 25mm performs in a Newt.
Only other way to round off your review is to try out the same EP in a refractor, namely an apo, as these will be best corrected for chromatic aberration. If you have a friend with say a Skywatcher ED80, that would be good enough. AND if you could also test it in an achro (fast and slow) and an SCT or Mak, then you've hit the review jackpot in covering all the major scope designs. I guess I am fortunate in that I do have samples of most of these scope designs, or easy access to friend's scopes, and this is something I try to do to become familiar with the EPs I use. This experience is what I look to share, or those reviews carried out in similar ways, and never hear-say. Hear-say only fosters ignorance and brand prejudice.
The HD-60 line may be designed optimized for a convex focal plane (refractors, SCT's and Maks), I don't know. Yet your review of the 25mm IN A NEWT is ONLY for that 25mm in a NEWT. Do not make performance calls about THIS 25mm in other scopes, nor assume that the other focal lengths in the HD-60 series will perform the same in a Newt or in any other scope. Contemporary EP design is much too complex for such simple assumptions. Thinking carefully about what you read in reviews can open up a world of really good EPs that are best suited to the scope/scopes YOU HAVE, and that will cover a modest budget all the way to the most exotic.
Alex.
|