One the gazillion little data that you need to have, in order to adjust the telescope mount in order to track celestial objects correctly, is the altitude of the location you are setting the gear up.
So here is a handy website that helps you determine the altitude of a given location
http://www.altitude.nu/
Seems quite accurate.
The famous M101 Galaxy!
Technical details :
Contains: NGC 5477, NGC 5473, M 101, NGC 5457
Imaging telescopes or lenses: Sky-Watcher 80ED Pro Black Diamond
Imaging cameras: Canon 350D
Guiding telescopes or lenses: Sky-Watcher 80ED Pro Black Diamond
Software: Pleiades Astrophoto PixInsight
Resolution: 1016×936
Dates: July 24, 2014
Frames: 30×243″ ISO400
Integration: 2.0 hours
Darks: ~10
Flats: ~30
Bias: ~30
Avg. Moon age: 26.86 days
Avg. Moon phase: 7.86%
Bortle Dark-Sky Scale: 2.00
Temperature: 22.00
RA center: 210.790 degrees
DEC center: 54.363 degrees
Pixel scale: 4.405 arcsec/pixel
Orientation: -89.651 degrees
Field radius: 0.845 degrees
Click HERE to get a full forecast for Athens sky.
