May 28, 2020

Observing from the ‘Hood’: Good Targets for Bright Skies.

If you’re like us here at Astroguyz HQ, you find yourself in the ‘burbs under increasingly brightening night skies. But you want to use that shiny new Christmas telescope, right? What follows is a list of objects that you can view tonight from the comfort of your backyard, can of beer and barbeque in hand. This list also serves as a peek at our star party faves, which can frequently occur under less than optimal skies; [Read more...]

Event of the Week: Happy Winter Solstice!

Brace yourselves; the Winter Solstice is upon us this week. This is the point at which the Sun reaches its lowest southerly declination and begins its long march northward. This makes for shortened days and long nights in the northern hemisphere and the reverse in the southern. Of course, its not the Sun that’s moving, but the Earth with its 23 degree 26′ minute tilt that causes this variation. Several cultures mark this celestial turn of events, not the least of which is modern day Christmas, which is fixed on December 25th, the solstice date on the old Roman Calendar. Modern reform by Pope Gregory gave us an offset solstice that falls on or around the 21st each year, and will eventually move by one day every 3,000 years. The solstice is always a good time to check out any local chance alignments at sun rise or sunset, as well as note the length of shadows cast at local noon. The precise timing of the winter solstice this year is Monday, December 21st at 5:47 PM Universal Time. Merry Saturnalia/Christmas!


This week’s astro-term is the Chandler Wobble. This is one of the many complex movements of our planet that causes the complex motions of the Earth’s axis to shift slowly. But unlike larger effects such as our friend, the precession of the equinoxes, the Chandler Wobble is much more subtle. First discovered by Seth Carlo Chandler in 1891, this movement amounts to 0.7 arc seconds or about 15 meters of axial shift over a period of about 433 days. This wobble is caused by the “sloshing” motion of Earth’s fluid core and even the drag created by the friction of our oceans. Think of the Earth as a sort of egg with a liquid center dragging us about  as we orbit about the Sun. This amount can vary (it was greatest in 1910) and is enough that modern off the shelf GPS devices can measure it and must take it into account. It can also cause the poles, equator and lines of longitude and latitude to change perceptibly. Along with the drag created by our Moon and Sun, the Chandler Wobble is also responsible for variations in Delta T, causing an occasional tweaking of our clocks by the addition or subtraction of an occasional second!

Astro Event of the Week: December 22nd-28th, 2008: A Christmas Meteor Storm?

The Ursids are the meteor shower that you’re not watching, but should be. A lesser shower, it typically produces around less than 10 meteors per hour right around Christmas time. This year, however, there may be two reasons to give the Ursids notice; one is that the Moon is a waning crescent, and presents less interference than its ill placed Full version during the Geminids early this month, and second, its progenitor, Comet 8P Tuttle, made a close (0.25 AU!) pass by the Earth on January 2nd of this year… could an Ursid outburst be in the offing? Reports of up to 100 meteors are not unheard of from this shower. Its peak is the night of the 22nd/23rd but of course, watching on either side of these dates may produce some surprises. Merry Christmas, Hanukah, Solstice, or what ever your holiday may be and keep an eye out for this elusive shower!

The astro-term of the week is circumpolar. In astronomy, an object is circumpolar if it stays above your local horizon 24-7. At the Earth’s equator, nothing is circumpolar; at the North and South Pole, everything is. At only a few degrees from the rotational North Pole, the radiant of the Ursid meteor shower is circumpolar for observers in the northern hemisphere.

View your own Star of Bethlehem.

    Over the years, much ink (real and cyber) has been spilt over the astronomical origins of the Star of Bethlehem. Biblical references are scant in regards to what the wise men may have seen; we know that the star “went before them…” every morning until it lay over the manger; the rest was history. But what was it?

[Read more...]