WAITING FOR THE SHADOW

SOLAR AND LUNAR ECLIPSE OBSERVING

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"Eclipse on Top of the World"
The March 20, 2015, Total Solar Eclipse

Introduction Sun/ Moon
Rise/ Set 
Sun Altitude
Eclipse Day
Orientation- corona
Sun's axis
EQ mount alignment
Sky at totality  Photographic Information Power & Batteries Further reading



Orientation of the corona, camera and mount alignment


The two diagrams show the orientation of the corona  with respect to the local horizon  at Longyearbyen during totality.  Both diagrams take rotation of the Earth and  tilt of the sun's  axis into account.  [Source :Joe Cali]  




Source Starry night Pro 6. Extra graphics, axis lines and labels added by Joe Cali in Photoshop.











Equatorial Mount Alignment


Magnetic Declination  Longyerben

D, the magnetic declination (sometimes called the magnetic variation), is the angle between the horizontal component of the magnetic field and true north. It is positive when the compass points east of true north, and negative when the compass points west of true north. Declination is given in degrees and its annual change is in degrees per year.
The value of magnetic declination should be added to a magnetic compass bearing to yield the true north bearing.  

Latitude    78.25o N
Longitude    15.63o E

Magnetic declination   
Australian Geomagnetic Reference Field Computation
Requested: Latitude 78o 15' 00", Longitude 15o 40' 00", Elevation 100 km, Date 2014/03/20
Calculated: Latitude +78.2500o, Longitude +15.6667o, Elevation 100.00 km, Epoch 2014.2137

Location is outside the AGRF area. A global field model has been used.

Magnetic Field Components

Date is outside global field model limits. Above application does not extend to 2015.  An extrapolation (below) has been calculated and applied by Joe Cali.

D=0.2999*YEAR-597.47  =  (0.2999 x 2015)-597.47 = + 6.828o

Magnetic declination = +6.828o

Magnetic north is 6.828o east of true north

Source http://ga.gov.au



Equatorial Mount Set up and Alignment
At the north pole, an alt-az mount is an equatorial mount. In Longyearbyen, an alt-az mount or tripod head inclined at 12o
will follow the sun with the movement of a single axis.

If you bring an equatorial mount or device to Svalbard, check that it can be set up at these extreme latitudes. Most commercially
manufactured  equatorial mounts have a maximum latitude of 65o without special modification.

The polar alignment jig below when combined with a bubble level and orienteering compass allow rapid polar alignments
in 1-2 minutes more than good enough for a solar eclipse.  Each jig is made for a particular location, the angles on the jig allow
elevation to be set with a simple bubble level and the azimuth to be set with magnetic declination correction built in to the jig.
In Longyearbyen, magnetic north is 6.8o east of true north. It will only work if you point the arrrow north and use it on the
east side of the mount. Used on the west side or pointing south, it will apply the magnetic declination correction in the wrong sense.

Print it out and mount it on a piece of 6mm thick foam core cut its outline exactly.  I use removeable double sided tape to attach a
bubble level to the jig. Yes an inclinometer will do the same thing but every little gadget you pack adds some hundreds of grams to the
weight you have to carry.  In Longyearbyen, this may involve truding up hills covered in soft snow,

Use the left and right sides with a compass to align azimuth and top and bottom with a bubble level to align altitude.
Alternatively use the bottom and left side with bubble level to align on a polar axis flange.









 

Using the jig and a compass to set the azimuth of the polar axis.  The jig takes the compass away from
magnetic metals and components in the mount and applies the magnetic declination correction to point
the polar axis true north.


Using the jig and a compass to set the altitude of the polar axis.
A simple line level attached to the jig using double sided tape is




Introduction Sun/ Moon
Rise/ Set & Twilight 
Solar Altitude
and Azimuth
on Eclipse Day
Orientation- corona
Sun's axis
EQ mount alignment
Sky at totality  Photographic Information Power & Batteries Further reading