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Astronomical question and answer 230

 

Frank L. Preuss

 

What is now an astronomical table good for?

 

20080801SunNovosibirsk

At the very bottom, below the table, it reads: "Total Solar Eclipse visible in Novosibirsk on 1 Aug"

We had been busy with this eclipse of the sun in answer 207.

So this table then confirms this eclipse of the sun.

There are several details, for example that the day almost lasts 16 hours or that the sun is 151.837 million km far away and that on the next day, on 02.08.2008, it is 0.020 million km closer.

The next table shows that the distance of the moon is 367 507 km. And that is more than the minimum distance of 350 032 km, which we had taken.

20080801MoonNovosibirsk

The times for the rising, Meridian Passing and the setting of the sun and of the moon vary little, since it was new moon, and therefore sun and moon were actually in the same direction. The differences result from that total eclipse was at 17:12, and that there is an exact agreement only at this point in time.

I now want to carry out the calculation of the diameter of the cone shadow with the new data.

For the distance of the sun from the moon we then have
151 837 000 minus
    367 507 =
151 469 493 km.

The distance of the moon from the surface of the earth is then
    367 507 minus
      6 378 =
    361 129 km.

The difference between the radius of the sun and that of the moon was 694 612 km. The inclination of the line is 694 612 / 151 469 493 = 0.0045858211 and y is then 0.0045858211 times 361 129 = 1 656 km. From the radius of the moon,
1 738 km, I now deduct
1 656 km, and then remain for the radius of the cone shadow
   82 km and that gives a diameter of the cone shadow of
  164 km.

This value is smaller than the value, which we had calculated in answer 212, 218 km, and that for that reason, because the moon is now further away.

For the diameter of the shade a value then results, which does not differ in the order from that value, which we had already calculated.

For completion now still two pictures come, which also deal with a solar eclipse, a famous one:

Sonnenfinsternis19190529

"Das bekannteste jener Fotos von der totalen Sonnenfinsternis vom 29. Mai 1919, die Einsteins Theorie zum Durchbruch verhalf."

"The best known of those photos of the total eclipse of the sun of 29th May 1919, which got Einsteinís theory generally accepted."

VerlaufskurveSonnenfinsternis

"Die Verlaufskurve der totalen Sonnenfinsternis vom 29. Mai 1919."

"The curve of the course of the total eclipse of the sun of 29th May 1919."

When one has a look at the width of this shade, then it has about the width of the length of South America and that is more than 8 000 km. And the width of the cone shadow is roughly 200 km.

The above astronomical tables also show that the place of the rising and the setting is quite different between the sun and the moon from one day to the next. With the sun the angle difference is less than one degree, and with the moon considerably more.

The above two tables also make a comparison of the positions of sun and moon possible, how they differ, but also approach each other, and that at new moon, and also how they stand facing each other, at full moon.

If one for example takes full moon on the 17th of August 2008, then the sun sets at 20:56 in Novosibirsk. And the angel deviates by 295 degrees from the north direction, points to the west north west direction. The moon rises at 20:55, therefore almost exactly at the same time, when the sun sets. And the angle is 106 degrees, therefore points in the direction east south east. The difference in the angle is 295 minus 106 = 189 degrees, therefore about 180 degrees, therefore in the opposite direction.

With an eclipse theses values are of course still more concurrent; something like this one could best compare with these tables, when an eclipse takes place directly at the time of the rising or the setting of these two heavenly bodies.

The eclipse of the sun on the 1st of August 2008 in Novosibirsk was at 17:12 and sunset was at 21:30. The eclipse of the sun was therefore more than 4 hours before sunset. And differences result from this:

When one now does not take sunset, but sunrise, then the deviations between sunrise and moonset on 17.08.2008 are (06:06/65o - 06:21/248o = 00:15/183o) already larger, because sunrise was already almost half a day away from the eclipse, 17:12 minus 06:06 = 11:06 hours.

The less these deviations get the more an opposite position is reached, the closer it is to an eclipse of the moon.

Novosibirsk is on the 83rd degree of longitude and in the time zone 7, I believe, and the time zone 7 is determined by the 105th degree of longitude. When this is correct that Novosibirsk is in time zone 7, then it is much more westwards from that midday time, which determines time zone 7. And that would mean that true midday time and the true midnight time are considerably later than 12 o'clock. And that are 1.5 hours. And the Solar Noon on the 01.08.2018 is at 13:34 on the above table and would confirm that Novosibirsk is in time zone 7. I have a map, which shows time zones, and it shows Novosibirsk in time zone 6, and that would then not be wright.

 

This is the end of "Astronomical question and answer 230"
To the German version of this chapter: Astronomische Frage und Antwort 230

 

 

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