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Cyberseeker
2012-Mar-20, 10:52 PM
As a general rule, a solar eclipse can only be seen by day and a lunar eclipse by night. :cool:

I have a question concerning how late into the day a solar eclipse can be seen. Can it be seen in the evening twilight? If so, how late? 6pm? 7pm? 8pm maybe?

Perhaps someone on this forum might be able to help me with an example of such a late solar eclipse.

Cyberseeker

Swift
2012-Mar-21, 01:26 AM
A solar eclipse can be seen any time the sun is in the sky.

My photo of a sunset, partial eclipse (http://www.bautforum.com/attachment.php?attachmentid=12236&d=1236489911). It is a little hard to see, but there is tiny "bite" out of the sun on the bottom edge. It got to about 20% by the time it set, at least at my location.

Here is a much more dramatic photo (http://apod.nasa.gov/apod/ap100715.html) (not mine unfortunately) from APOD in 2010.

Centaur
2012-Mar-21, 01:47 AM
As a general rule, a solar eclipse can only be seen by day and a lunar eclipse by night. :cool:

I have a question concerning how late into the day a solar eclipse can be seen. Can it be seen in the evening twilight? If so, how late? 6pm? 7pm? 8pm maybe?

Perhaps someone on this forum might be able to help me with an example of such a late solar eclipse.

Cyberseeker

Welcome to the discussion group, Cyberseeker.

The rule is not merely “general”; it is absolute. A solar eclipse occurs when the Moon appears in front of the Sun. Obviously that can only be observed during the time between the observer’s local sunrise and sunset. Not only can it not occur at night, it cannot occur during either evening or morning twilight. The Sun must be above the local horizon for a solar eclipse to be observed. Of course while witnessing a solar eclipse there would be a resemblance to being in twilight.

Romanus
2012-Mar-21, 02:04 AM
Here's a track map for a fairly typical eclipse, a solar eclipse for November 3, 2013:

http://eclipse.gsfc.nasa.gov/5MCSEmap/2001-2100/2013-11-03.gif

If you click on the Google Map version of that eclipse path (and I do recommend it), you'll see that the western end (off the U.S. East Coast) of it is at local sunrise, and the eastern end (in the Horn of Africa) at local sunset. The peak eclipse is around local noon in the Gulf of Guinea. This is because the speed of the Moon's shadow is much faster than the Earth's rotation at the surface, so it kind of slices across the lit hemisphere from sunrise to sunset.

tony873004
2012-Mar-21, 02:34 AM
Here's a picture I took from San Diego in 1992. It's about as close as you'll get to an "evening" solar eclipse. If you live in New Mexico or Texas, you'll get a chance to take a similar picture on May 20 this year.
http://orbitsimulator.com/sunset/1024fs_eclipse92.JPG

Cyberseeker
2012-Mar-21, 02:40 AM
Thanks for the answers so far. As you can see, Im not an astronomer. :o

Hypothetical question for you. Im told by a friend who lived for some years in Spain that during the summer it could be daylight till 10pm. Let us say that a full solar eclipse came along at 9:30 pm in summertime; would it be visible as a solar eclipse?

chornedsnorkack
2012-Mar-21, 08:18 AM
When the Sun is eclipsed in "twilight", i. e. the whole Sun is below horizon, the weather may be slightly darker than normal but it would not be conspicuous what the reason is.

But obviously, at every solar eclipse, the path of the eclipse should cross the terminator of Earth twice.

So, you should be able to see solar disc intersected by both horizon and Moon.

astromark
2012-Mar-21, 09:38 AM
Thats a very nice shot 'Tony873004..'

utesfan100
2012-Mar-21, 03:07 PM
Thanks for the answers so far. As you can see, Im not an astronomer. :o

Hypothetical question for you. Im told by a friend who lived for some years in Spain that during the summer it could be daylight till 10pm. Let us say that a full solar eclipse came along at 9:30 pm in summertime; would it be visible as a solar eclipse?

Ecclipses only occur when the line of intersection between the plane of the moon's orbit and the plane of earth's orbit is pointed towards the Sun. Presently, this only happens in May and September.

If we wait a few millenea this may precess into a summer-winter configuration.

grapes
2012-Mar-21, 04:00 PM
Ecclipses only occur when the line of intersection between the plane of the moon's orbit and the plane of earth's orbit is pointed towards the Sun. Presently, this only happens in May and September.

If we wait a few millenea this may precess into a summer-winter configuration.What is this about? :)

The moon's orbit precesses fairly "rapidly", and the NASA eclipse page http://eclipse.gsfc.nasa.gov/ lists last year's eclipses in Jun/Jul and Nov/Dec; this year's in May/Jun and Nov.

Cyberseeker
2012-Mar-21, 04:12 PM
Ecclipses only occur when the line of intersection between the plane of the moon's orbit and the plane of earth's orbit is pointed towards the Sun. Presently, this only happens in May and September.

If we wait a few millenea this may precess into a summer-winter configuration.

I think I had better give some added detail. Here is everything I know about it. :)

Date: February 25, 5BC
Time: 20:31 (8:30 pm)
Timezone: GMT + 2
Latitude: 31:46
Place: Jerusalem
Type: Total Solar Eclipse


The historical reference concerns the death of Herod the Great as recorded by Josephus (17:6:4) I think late February would be early springtime. Whats the chance of this eclipse being a few minutes prior to sunset?

Centaur
2012-Mar-21, 04:16 PM
Im told by a friend who lived for some years in Spain that during the summer it could be daylight till 10pm. Let us say that a full solar eclipse came along at 9:30 pm in summertime; would it be visible as a solar eclipse?

Yes, if the Sun were actually above the horizon at 9:30 pm. However, I have my doubts about the Sun setting in Spain at 10 pm, unless Spain were on a special daylight savings time of multiple hours. I suspect that your friend meant it was twilight until 10 pm.

utesfan100
2012-Mar-21, 04:17 PM
What is this about? :)
Apparently it is about several orders of magnitude underestimate of the precession of the lunar orbit.

So it will take a few dozen years to get back to a summer ellipse, like we apparently had a few years ago.

Centaur
2012-Mar-21, 04:22 PM
Ecclipses only occur when the line of intersection between the plane of the moon's orbit and the plane of earth's orbit is pointed towards the Sun. Presently, this only happens in May and September.

If we wait a few millenea this may precess into a summer-winter configuration.

As grapes notes, the precession of the lunar nodes is much more rapid. It goes through a full cycle in 18.6 years. In fact, after 9.3 years the nodes will have completely reversed, with eclipses occurring during the same months as nine years earlier. You may be confusing this process with the precession of the equinoxes, which takes about 25,800 years.

grapes
2012-Mar-21, 05:18 PM
Apparently it is about several orders of magnitude underestimate of the precession of the lunar orbit.

So it will take a few dozen years to get back to a summer ellipse, like we apparently had a few years ago.More like half a dozen. :)

Jens
2012-Mar-22, 12:01 AM
The historical reference concerns the death of Herod the Great as recorded by Josephus (17:6:4) I think late February would be early springtime. Whats the chance of this eclipse being a few minutes prior to sunset?

I'm not sure how you get that. Not knowing much about it, I looked around a bit and there are references to a lunar eclipse. Did you mean solar? Also, you're talking about historical materials that are not necessarily very precise.

Cyberseeker
2012-Mar-22, 02:34 AM
I'm not sure how you get that. Not knowing much about it, I looked around a bit and there are references to a lunar eclipse. Did you mean solar? Also, you're talking about historical materials that are not necessarily very precise.

Josephus was a Roman historian and generally pretty reliable. Herod's reign is well documented in history and his death occurred shortly after an eclipse early 4BC. Commentators usually cite a partial lunar eclipse 13th March 4BC. However, there was also a full solar eclipse 25th Feb 4BC. I am considering the possibility that Josephus wrongly reported the former when in fact it was the latter.

'Just a theory of mine and that is why Im asking here if an 8.30pm solar eclipse was possible in early spring?

Centaur
2012-Mar-22, 06:17 AM
I think I had better give some added detail. Here is everything I know about it. :)

Date: February 25, 5BC
Time: 20:31 (8:30 pm)
Timezone: GMT + 2
Latitude: 31:46
Place: Jerusalem
Type: Total Solar Eclipse


The historical reference concerns the death of Herod the Great as recorded by Josephus (17:6:4) I think late February would be early springtime. Whats the chance of this eclipse being a few minutes prior to sunset?

There was no eclipse on BC 5 FEB 25. At 20:31 UT+2 at Jerusalem the 92.5% illuminated waning gibbous Moon was 148 west of the Sun and 7 above the eastern horizon after having risen at 19:54 UT+2. The Sun had set at 17:34 UT+2.

Centaur
2012-Mar-22, 06:34 AM
Josephus was a Roman historian and generally pretty reliable. Herod's reign is well documented in history and his death occurred shortly after an eclipse early 4BC. Commentators usually cite a partial lunar eclipse 13th March 4BC. However, there was also a full solar eclipse 25th Feb 4BC. I am considering the possibility that Josephus wrongly reported the former when in fact it was the latter.

'Just a theory of mine and that is why Im asking here if an 8.30pm solar eclipse was possible in early spring?

Now I see that you have changed the year from 5 BC to 4 BC. Argh!!! Indeed, there was a total solar eclipse on BC 4 FEB 25. The total eclipse was only visible in the South Pacific Ocean, South America and the South Atlantic Ocean off the coast of South America: http://eclipse.gsfc.nasa.gov/SEsearch/SEsearchmap.php?Ecl=-00030225 . Jerusalem was not even in the zone for a partial eclipse. FYI: 4 BC was the astronomical year -3; the difference due to historians not recognizing a year zero while astronomers do.

There was a partial lunar eclipse visible from Jerusalem on BC 4 MAR 13 during the hours after midnight. The umbral phase would have begun at 01:30 UT+2 and ended at 03:48 UT+2. This is based on an assumed Delta T of 9912 seconds, which could be off by several minutes. The maximum coverage by the umbra was 36% of the lunar diameter.

Cyberseeker
2012-Mar-23, 05:47 AM
South America? Well, that settles my little theory doesn't it?

But thanks for the conversation and all the good help. :D