Forwarded Message regarding observations of Alpha & Gamma Orionis:

... While observing an ~ 600 foot high TV tower from ~ 3000 feet away through my kitchen window near Falls Church, VA, I timed - employing WWV & CHU - several emersions from occultation of Alpha & Gamma Orionis arising therefrom from about 1995 Nov. until 1999 Jan. Subsequent reductions of these observations allowed me to determine the pseudoinertial period of rotation of the Earth upon its axis, to a precision of ~ 2 ms / rotation, as distinct from the equinoctial about 8.3 ms shorter! ..."

J.N., Falls Church, VA.

SRG Comment:

Since the position of Sirius is essentially in the general direction of Alpha Orionis, it is possible that the result of the above observations could closely match our Sirius data. The difference in the observer's latitude should have no significant effect on the actual time difference, which has been determined in each case between Earth's "pseudoinertial" period of rotation, as Mr. J.N. refers to it, and the equinoctial rotation. The observations indicate that variations in Earth's rotation period are due to oscillations of the axis of rotation.

Unfortunately, Mr. N. did not mention the exact date and time of the observation period. In an effort to compare the data more precisely, we offer three specific measurements of Sirius during the period Oct/Nov 1995 to Jan/Feb 1999. The various time differences (from 6.28 ms to 8.75 ms) in relation to the equinoctial period seem to confirm that his careful observations are indeed correct. The apparent discrepancies between these individual observation periods, starting in November 1995, are also noticeable in the following diagram at http://www.siriusresearchgroup.com/graphic2.htm.

The calculations below show the daily time difference, as compared to the constant time difference between the mean solar day and the mean sidereal (equinoctial) day [i.e. 86400 s minus 86164.0905382 s = 235.90946 s], for the specified transit periods:

1995

30.10. 07h 39' 06''

a) 2594 s ÷ 11 transits = 235.818 s

10.11. 06h 55' 52''

b) 2125 s ÷ 9 transits = 236.111 s

19.11. 06h 20' 27''

c) 3304 s ÷ 14 transits = 236 s

03.12. 05h 25' 23''

1998/1999

20.12. 04h 17' 27''

d) 5665 s ÷ 24 transits = 236.042 s

13.01. 02h 43' 02''

e) 2597 s ÷ 11 transits = 236.091 s

24.01. 01h 59' 45''

f) 2832 s ÷ 12 transits = 236 s

05.02. 01h 12' 33''

In each case the daily difference with respect to the "constant 235.90946 s" is then divided by the number of transits, whereby (+) means longer and (-) means shorter than equinoctial time (86164.0905382 s):

a) + 0.09146 s ÷ 11 = + 8.31 ms

b) - 0.202 s ÷ 9 = - 22.41 ms

c) - 0.09054 s ÷ 14 = - 6.47 ms

d) - 0.132 s ÷ 24 = - 5.51 ms

e) - 0.181 s ÷ 11 = - 16.5 ms

f) - 0.09054 s ÷ 12 = - 7.55 ms

* * *

The following is the calculation of the mean transit period of Sirius (total time elapsed between first and last transits divided by the total number of transits):

I.

10.11.95 06h 55' 52''

13.01.99 02h 43' 02''

Elapsed time interval: 3 × 365 days (mean solar day of 86400 s) plus one leap day plus 64 days minus the difference of 15170 s on the last day of measurement. It follows,

100,208,830 s ÷ 1163 = 86164.08426 s (i.e. 6.28 ms shorter than equinoctial)

II.

10.11.95 06h 55' 52''

24.01.99 01h 59' 45''

Elapsed time interval: 3 × 365 days plus one leap day plus 75 days minus the difference of 17767 s on the last day of measurement. It follows,

101,156,633 s ÷ 1174 = 86164.08262 s (i.e. 7.92 ms shorter than equinoctial)

III.

10.11.95 06h 55' 52''

05.02.99 01h 12' 33''

Elapsed time interval: 3 × 365 days plus one leap day plus 87 days minus the difference of 20599 s on the last day of measurement. It follows,

102,190,601 s ÷ 1186 = 86164.08178 s (i.e. 8.75 ms shorter than equinoctial)

Additional Comment:

At the beginning of January, when the Earth is in its perihelion it is also between Sun and Sirius, as well as Orion. During that time it appears that significant deviations occur in Earth's period of rotation, causing it to be shorter than its equinoctial rotation. For that reason it was found that transit times taken from April 1993 to April of the following years reflect a more uniform measurement, as no significant oscillations were observed during this particular month. Of course, the longer the observation period the more accurate the result will be. As the graphics on our website show, it is very likely that a measurement from November until January, for example, would actually represent an observation period from one maximum of an oscillation to that of another.