A simple stargazing tip

[cantaresg]

Without a starmap on hand, or when the stars are so unfamiliar that the common signpost are no where in sight, how do you find your way around the sky? Here is a simple trick, though it is probably not applicable to many experts here who are so well versed with the sky.

To begin, you need to know the horoscopes pretty well, for example, the horoscope of Pisces falls between 19 Feb - 20 Mar. Why is this important? In astrology, horoscopes are also known as sun signs. This is because, in ancient Greek, it was observed that during this period of time, the sun is observed to be "housed" in the constellation of that sun sign. So with this knowledge, we will be able to know the location of the sun relative to the sky just by knowing the date and the horoscope now.

However, there is one little trouble. In the past, the first horoscope is in Greek astrology is Aries. This is because during the vernal equinox, which is the day when the length of daytime is equal to the length of night time, the sun is in Aries. That's why until now, the point is still known as the First Point of Aries. However, due to the precession of the Earth, the sun is actually "housed" in Pisces during the vernal equinox. Thus, using horoscope to judge the position of the sun in the sky is not as accurate now.

However, we can still obtain a rough estimate of the position of the sun. All we need to do is to "subtract" one horoscope, meaning if this is the month of Virgo, the sun is actually housed in Leo, the horoscope before Virgo.

So how is this useful? If we know the time at which the sun sets (which in Singapore, it is about 7.20pm), we can estimate the position of any zodiacal constellation in the sky. There are 12 zodiacal constellation in the sky, each spans an approximate 30 degrees across the sky. So by knowing the zodiac that is setting, the position of any other constellation can be approximated.

Take for example, this is the month of Virgo, thus the sun is in Leo now. Hence, at 7.20pm, Leo is approximately setting, and Virgo can be found at about 30degrees above the horizon, libra at about 90 degrees above the horizon, and Scorpio is at the Zenith. At the same time, the 6th constellation from Leo, which is Aquarius, is in the rising position. Thus, if you know how the rest of the sky is relative to the zodiac, this provides a quick way to guestimate the rising time and setting time of any constellation in the sky.

[weixing]

Hi,

There are 12 zodiacal constellation in the sky

There are actually 13 constellation that the ecliptic pass through. The one missing in the horoscopes is Ophiuchus.

each spans an approximate 30 degrees across the sky.

Please note that this is not always correct as some of the zodiacal constellation occupy more of the ecliptic and some occupy less. Also, not all zodiacal constellation are of the same size... some are very big and some are quite small.

Anyway, the best way is to learn a few well known and easy constellation and start learn other constellation near it.

Have a nice day.

[jermng]

Thanks. I still find it easier to recognize 'patterns' (constellations) than to memorise the zodiacs and their time periods ..

[Airconvent]

very interesting tip! I could put it to good use if only I can remember the sequence of the horoscope!...but otherwise a useful thing to remember for a newbie. thanks!

[cantaresg]

Yes, I am aware of the presence of the "13th Zodiac", and that the time taken for each Zodiacal constellation is different. But nonetheless this is a useful technique for quick approximation.

I had started stargazing the same way as most anyone did. But recognising the brightest constellation like Orion and used them to guide around the sky. But at some point of time, I find that it becomes useful if I am able to estimate the rising time or setting time of various constellation and use that to provide a guide to the rest of the sky.

This technique has its weakness, and probably those who are too familiar need not do this at all. But for a start to astronomy, this is another quick method to access the sky as well. Incidentally, I devised this method on one of the stargazing sessions some 10 years back.

[cantaresg]

Oh... and it is not necessary to remember the dates either. Just know that from one sign to another, it is roughly 20th of this month to 20th to next month.

[kochu]

A real "retrograde" method in the age of "My Sky" and "Sky Skout".

Kochu/11-9-07
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[zong]

cool tip.. but i guess alot of people here don't need it.

But it's always good to learn more isn't it? Impress the newbies so that they want to join and learn.. haha..

Cantaresg, do continue these interesting tips coming!

[weixing]

Hi,

cool tip.. but i guess alot of people here don't need it.

Hee... hee... I got very bad memory and my English is not good... can't even accurately pronounce "Refractor" and "Reflector", so can't remember most of those constellation name... :oops: :oops: Anyway, I always bring my star charts with me when going observing... don't leave home without it...

Have a nice day.

[cantaresg]

I had mentioned that experts here probably won't need the tip right? Hehe. but it is true that this is one of the tricks that I pulled in the past to attract newbies. Imagine how amazed they are when you pull out your fingers, fiddle a bit, and you can "predict" the positions of some common constellations even before they rose? I remembered there was instances when there are students who asked me where is Orion, and I pointed towards my feet, knowing that Scorpio was right overhead with the Sun. haha...