Collecting eyepiece data

Need some here,

I seem to be putting together a pretty big quality eyepiece collection so far. I want to compile some relevant detailed information on each eyepiece I currently own, either in the form of a database and/or individual sheets for each.

What short of "specific data" should be included on the form for each eyepiece, what kind of comparisons or evaluations, if any should, I included? I suppose I am asking what sort of data will be useful down the road to myself and others. Since I am new to this hobby and still in the beginning learning stages, I want my information to be useful. I am not concerned how much time this will take either.

-JWW:

I have a personal spreadsheet, as do many others I'm sure.

Included are:

focal length (mm)
apparent field of view (deg)
eye relief (mm)
weight
barrel size (1.25" or 2")
price
type

If you know your telescope focal length and aperature, you can then calculate:

focal ratio = telescope focal length / telescope aperature

magnification = tele focal length/eyepiece focal length

true field of view = apparent field of view / magnification
(Note this equation is approximate but good enough for selecting eyepieces)

exit pupil = telescope aperature (mm) / magnification
or
exit pupil = eyepiece focal length / telescope focal ratio

Some rules of thumb:

magnification > 50x aperature in inches are difficult to achieve due to atmospheric conditions and quality of scope. This is the same condition as exit pupil less than 0.5mm.

Exit pupil > 7mm can be problematic for telescopes with central obstructions like newtonians and SCT's.


There is a large downloadable eyepiece database on the CloudyNights site.

Mike

James,
Here are a couple of links to get you started. The first is the Tele-Vue eyepiece spec sheet. I wish all makers would publish this data. It will give you an idea or the sort of data you may want.
The second is the Tele-Vue eyepiece calculator and calculates the performace for every current Tele-Vue eyepiece for your instrument. I have print-outs of the calculator results for each of my scopes.

http://www.televue.com/engine/page.asp?ID=144

http://www.televue.com/engine/page.asp?ID=107

Hope it helps,
Bob