# Astronomical Calendar 2018 Pursued

You can still see Mars close to Jupiter by getting up tomorrow morning.

And (I wish of course I could have timed this a day earlier, but…) you can find the second instar of Astronomical Calendar 2018 by clicking on the tab above.

I have improved the appearance and added some more kinds of event – so far, conjunctions of the planets with each other and with the prominent stars and clusters, and events of the first four asteroids.  More later.

And, to test whether I can set pictures in, I’ve done so – using tomorrow morning’s picture.  I think you will find you can see it more sharply in the PDF than in the blog.

Some have asked whether the online Astronomical Calendar will develop into a printed book.  No.  No more of that prodigious annual struggle and expense.

Instead, I hope to make a group of smaller books, with charts and more, for the astronomical years ahead.  The first, whose title may be A Longer View: Uranus, Neptune, and Pluto, is almost ready.

## 8 thoughts on “Astronomical Calendar 2018 Pursued”

1. Anthony Barreiro says:

I’m curious why the times for some events are reported to the minute, while others are reported to the hour. The Julian dates all seem to have the same number of significant digits. Idle curiosity.

1. For some, such as eclipses and the Moon’s phases and nodes determining them, precision to the level of the minute matters; for others, such as superior conjunctions and meteor showers, it would be spurious precision. In the unlikely case that you really want to know the time of Pluto’s stationary moment to the minute, you could multiply by 24 the difference between the last three figures of the Julian date and .5. (The Julian date at the beginning of a UT day ends with .5.) The Julian dates are all given to the same number of digits so that subtraction will be true.

1. Anthony Barreiro says:

Thanks Guy. That’s a lot of arithmetic! I understand that Julian dates are useful for measuring elapsed time over long time frames, but they’re unwieldy.

1. Astronomers are interested in them because all calculation of dates is done by using them (conveting to calendar dates only at the last stage, if at all). They can be shown by omitting the first three digits and explaining that it’s understood that “245” should be put at the front, and maybe that’s what I’ll do.

2. John Goss says:

Mars and Jupiter were hard to separate at 5:30 a.m. Blurry eyes and cold weather!

3. Brian Davis says:

I greatly appreciate this Astronomical Calendar 2018!