Eyepiece Technical Database (fixed links)

Given many recent discussions about EP technical data I like offer here a spreadsheet with data about EP that I do or have owned. It is similar to Televue's eyepiece specifications found at http://www.televue.com/engine/page.asp?ID=144.

It allows to exactly answer questions like:
How does the field of view of EP xx compare to YY ? Which fits more into its field of view ?
Does EP xx show all of Pleiades in my scope ?
Is EP xx parfocal with yy ?
I have EP xx and with that I have 10mm focuser in-travel left. If I buy EP yy, will it still come to focus ?

I'd appreciate any suggestions to improve this as I'm sure many users will need more explanations how to use this data.
Or how to measure their own eyepices to add to this list.
Attached is a picture of the spreadsheet, the .xls file itself can be found at http://home.comcast.net/~ad7ic/EP_data.xls

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Here is an example how to measure FPloc, the location of the focal plane of an EP, which I use in my spreadsheet. This might also help to understand how to use this number to predict how much focuser travel any other EP in the database will need.

First set up your scope, so that you can focus it on something. Anything will do, so this can be done in daylight and with a very close in object. Use a diagonal as needed.
Tape a metric scale to the OTA of your scope, so you can read the location of a mark on the drawtube (moveing part of the focuser) with it. In my example I stick a post-it note on the diagonal, since this moves just like the drawtube.
Now we calibrate the setup - by useing an EP for which FPloc is know. E.g for any Televue EP, FPloc is listed as Dimension F at http://www.televue.com/engine/page.asp?ID=144.

Now, after focusing with this known eyepiece, adjust the mark to point to the correct FPloc for this EP. In my example, the TV 3-6mm zoom has FPloc=+6.2mm, so I point the mark to point 6mm outward of the red 10cm mark, which I use as my reference.
Then exchange the EP and re-focus. The mark now points to the FPloc of the new EP. Instead of many words I just like to refer to the two insets in the attached picture giving examples for different EP with different FPloc.
One final word of caution: When changeing from 2in to 1.25in EP an adapter might be used that extends a bit outside of the 2" barrel. This has to be accounted for by moveing the mark by the amount of this extension. Or better recalibrate the setup with a known EP of the same barrel size.

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