Delta-T is the difference between Dynamical Time (TD),
the uniform time system based on atomic clocks, and Universal
Time (UT), the slightly irregular system based on the earth's
rotation. It is widely used in astronomical formulae.
Guide uses observed values of Delta-T for dates from 1620 to
the present, and a formula to approximate values before 1620.
(Our knowledge of the earth's rotation, and hence of UT, is
limited for medieval and ancient dates.) For dates in the
future, it uses a separate formula that makes some assumptions
about how the rotational speed will vary. It shows the value
used for Delta-T in the Quick Info section.
Benoît
How does guide compensate for leap seconds?
We do need to know the leap seconds elapsed to convert from T1 to UTC. Yes?
I have not updated guide in years(15 yrs?). So how do I input leap seconds in guide?
On 8/23/2017 4:07 PM, Luc Desamore luc_desamore@yahoo.ca [guide-user] wrote:It could have something to do with limb effect (real vs mean limb)
Luc
From occult 4.3.2.0 : (with limb effect)
S O L A R E C L I P S E P R E D I C T I O N for 2017 Aug 21
East Longitude - 88 6.00
Latitude 37 4.10
Altitude 0 m.
TT-UTC 69.2 secs Prediction basis: DE430
UT1-UTC 0.2 secs ▲T [= TT-UT1] 68.9 secs
Event UTC P.A. alt. Differential Corrections
h m s o o A B C
First Contact 16 55 6 293 61 2.10 -0.59 -0.03
Baily beads @2nd 18 23 1
Second Contact 18 23 9.5 120.9
Maximum Eclipse 18 24 30 64 2.06 -1.25 -0.01
Third Contact 18 25 49.3 293.4
Baily beads @3rd 18 25 56
Last Contact 19 50 23 114 54 1.62 -1.68 0.01
[2nd and 3rd contacts are based on the lunar limb derived from LRO LOLA]
Magnitude at Maximum Eclipse 1.013
Magnitude (diameter ratio) 1.031
_______________________________________________________________________________
without limb effect :S O L A R E C L I P S E P R E D I C T I O N for 2017 Aug 21
East Longitude - 88 6.00
Latitude 37 4.10
Altitude 0 m.
TT-UTC 69.2 secs Prediction basis: DE430
UT1-UTC 0.2 secs ▲T [= TT-UT1] 68.9 secs
Event UTC P.A. alt. Differential Corrections
h m s o o A B C
First Contact 16 55 6 293 61 2.10 -0.59 -0.03
Second Contact 18 23 11 122
Maximum Eclipse 18 24 30 64 2.06 -1.25 -0.01
Third Contact 18 25 50 286
Last Contact 19 50 23 114 54 1.62 -1.68 0.01
Magnitude at Maximum Eclipse 1.013
Magnitude (diameter ratio) 1.031
On 2017-08-23 20:40, bob davis bob@bobsbits.net [guide-user] wrote:So I am chasing down an anomaly of the timing...
I was at
37.06769 -88.10091
which is down to a 1.112 meter
Nasa google maps showed totality begging at.
and guide8.0 showed the following:
I timed it at:
13:23:08
I wonder if it has something to do with leap seconds?
-- Bob Davis 9 Meadow Lane Exeter NH 03833 603-778-0781-- bob davis 9 Meadow Lane Exeter NH 03833 603-778-0781