SPA Aurora Section

Recording Auroral Observations

When aurora is present details should be taken of the forms present and the position in the sky where they appear. Measurements of the display's extent in altitude and azimuth should be made. This can easily be estimated using a clenched fist held at arms length as a measure of 10°. Polaris is a convenient reference point being at 0° azimuth and at an altitude equal to the observer's latitude. Alternatively, observers can make a simple alidade from a protractor with plumb line attached. Such a device will return more accurate results and avoid the difficulty of locating the true horizon, which, due to local landscape features, will lie a few degrees below the apparent horizon. If possible, try to measure the following angles...

Azimuth: A measure of a feature's extent around the horizon from west (270°) through north (0°) to east (90°).

Altitude: A measure of the vertical extent of an auroral form above the horizon with the horizon 0° and the zenith 90°. Two altitude measurements should be taken...
h: A measure in degrees of the highest point on the base of an auroral feature above the horizon.
/: A measure in degrees of the top part of a display above the horizon.

Often, measurements of / only will be possible as base features can lie below the horizon.

Altitude and azimuth coordinates should not be confused with the RA and Declination positions quoted in astronomical texts - these are simply the location of an object in the observer's sky at a particular time.

Making Reports

When observing aurora, the following details should be included in reports along with your name and correspondence address...

DATE: Always use the double date convention. That is, 1991, November 8-9 refers to the evening of the 8th to the morning of the 9th.

TIME: Timings to the nearest minute should be made when significant changes to a displays appearance or position occurs. Universal Time (UT) should be used. Since UT is the same as GMT, UK observers must remember to subtract 1 hour when British Summer Time is in operation (UT=GMT=BST-1 hour).

LOCATION: The place where observations were made. If this happens to be a remote location, latitude and longitude positions should be supplied.

Results should be presented in a format similar to the following example...

    UT    h   ae   Azimuth  Feature  Brightness     Notes 
 
    2315  6   14  320-030     qHA       2           Green, diffuse. 
    2345  8   25  315-040     aRA       3           Red ray tops. 
    0005  6   15  320-035     mHP       2           Green. 
    0015  -   10  330-020      N        1           Fading.

Auroral Photography

The aurora makes an excellent subject for astronomical photography, with 35mm format widely favoured amongst amateurs. Cameras require a 'B' setting with a cable release facility to allow timed exposures. Fixed firmly to a sturdy tripod the camera should be pointed at the brightest part of the aurora. Using a fast film - colour slide gives best results - of ISO 400 and a lens setting of f2 the following exposures may be used as a rough guide...

    Aurora Brightness Level.           Exposure (seconds) 
              1                         30-60 
              2                         20-30 
              3                         10-20 
              4                         Less than 10

Created by Michael Oates Last modified 3 February, 2001

DATE:	Always use the double date convention. That is, 1991, November 8-9 refers to the evening of the 8th to the morning of the 9th.
TIME:	Timings to the nearest minute should be made when significant changes to a displays appearance or position occurs. Universal Time (UT) should be used. Since UT is the same as GMT, UK observers must remember to subtract 1 hour when British Summer Time is in operation (UT=GMT=BST-1 hour).
LOCATION:	The place where observations were made. If this happens to be a remote location, latitude and longitude positions should be supplied.