1. Date & time (JD or UTC yyyy/mm/dd hh:mm:ss):
2. Location (0.5 degree accuracy is enough):
   Latitude: , longitude: (or get them from Geolocation).
3. Chart:
   Name of the variable star, or AAVSO chart ID:
   Limiting magnitude: , FOV [arc minutes]:
   Chart orientation: North up, West to the right (binoculars & terestrial instruments) South up, East to the right (Newtons, refractors & SCTs) North up, East to the right (scopes with diagonals, view from above) South up, West to the right (scopes with diagonals, lateral view)
   
4. Brightness estimate as (A (brightness steps) V (brightness steps) B)
   

   Bright star

   steps

   Variable

   steps

   Dim star

   (+) Add row

5. Without considering extinction, brightness of V is:
   unknown
   Air mass for variable star V is unknown
   
   For the airmass values above, you should not need to correct for extinction.
6. Extinction coefficient (K)
   Use value:
   Or compute it from observations (using this method):
   Argelander comparisons Paired comparisons
7. Considering extinction, brightness of V is:
   unknown

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Extinction-O-Meter - an HTML & JavaScript utility to apply differential extinction corrections to brightness estimates.
(source code available at <https://bitbucket.org/herr_alien/extinction-o-meter>)

Copyright 2015 Herr_Alien <garone80@yahoo.com>

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see <https://www.gnu.org/licenses/agpl.html>.