Quote:
Originally Posted by Rodstar
Hi Phil, I am interested to see what others have to say in response to your post as I am contemplating purchasing the longest focal length Delos (17.3mm).
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Hi Rod,
I am not quite sure why you need to consider this eyepiece, unless you are also changing other things.
Am I correct in assuming you own a 13mm ETHOS and a 20mm T5 Nagler?
If so, in your scope (20"/F5 FL = 2550mm) these eyepieces give you the following True Fields of View and magnification
13mm ETHOS = .51 degrees TFOV @ 196X
20mm Nagler T5 = .64 degrees TFOV @ 128X
If you purchase the 17.3mm DELOS with its 72 deg AFOV it will give you
TFOV = .49 degrees @ 147X
Consequently you gain nothing in terms of TFOV. It gives a slightly reduced TFOV compared to your 13mm ETHOS at lower magnification, thus contrast and detail will be slightly reduced compared to the 13mm ETHOS. I can understand however that 147X may be a more usefull magnification for you under variable seeing conditions than the 196X of the 13mm ETHOS, which may not always be useable.
I think in your case the 17mm ETHOS would be a better choice, but this then bumps heads with your 20mm Nagler in terms of TFOV.
Maybe you need a lengthy discussion with SWMBO and tell her you should sell the 20mm Nagler T5 and buy the 17mm and 21mm ETHOI to go with your 13mm ETHOS
Cheers,
John B