* Astronomy

Keep both eyes open when observing with a telescope.

How can we exactly measure the apparent field of view of an eyepiece?

Knowing the actual field of view (FOV) for an eyepiece can be very helpful when planning an observing session. The apparent FOV depends on the eyepiece design, and sometimes that, and the FOV, is not always known - but can simply be determined by using a stopwatch.

Locate a star close to the celestial equator and place it at the eastern edge of the field of view in the eyepiece. And simply time how long it takes for the star to drift across the field of view (passing through the center of the eyepiece) and disappear. (Remember to turn off your telescope motor drive/tracking).
Enter the measured time into the following equation:

FOV = T x 15.04 x Cos(delta)

T = Drift time in minutes
Cos(delta) = The star's declination (For stars near the celestial equator, Cos(delta) = 1)

Ed ~ Simply, (For stars near the celestial equator); Time x 15 = FOV

Quick and Dirty Polar Alignment

EQ mounts must be at least approximately aligned with the north celestial pole. For Northern Hemisphere observers, this is located within about ½ degree of Polaris, the North Star. Thus, for visual use, the EQ mount can simply be pointed at Polaris.
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Tip for today:
Use Sorbothane Sport Heel Pads or shoe insoles to reduce tripod vibrations. 
Sorbothane is an elastomeric vibration-absorbing material used to dampen vibration in turntables or for shoe insoles, but they are excellent for reducing telescope tripod vibrations. Thin Sorbothane pads can be sandwiched between hard plastic or metal and placed under one, or more, tripod foot.

Suitable Sorbothane HI-FI isolation feet or rings can also be used.

Sorbothane is a proprietary, visco-elastic polymer. Visco-elastic means that a material exhibits properties of both liquids (viscous solutions) and solids (elastic materials).
Sorbothane is a thermoset, polyether-based, polyurethane material. Sorbothane combines shock absorption, good memory, vibration isolation and vibration damping characteristics. In addition, Sorbothane is a very effective acoustic damper and absorber.
Absorbs up to 94.7% of impact energy, then reforms to its original shape. Sold in a 12" x 12" x 1/8" sheet. For use by scientists, designers and experimenters
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Meade - vibration isolation pads, set of 3

$49.95
Meade's set of three vibration isolation pads typically reduce telescope tripod vibration times to less than one second, allowing undisturbed viewing sooner. Telescope vibrations are caused by windy conditions, ground vibrations (from people walking near the scope or nearby traffic), an unsteady mount or tripod, or even the simple act of touching the scope to focus.
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