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MAS Frequently Asked Questions


MAS Frequently Asked Questions

Frequently Asked Questions about astronomy (see also MAS Beginners page)

This page answers many commonly asked questions about astronomy. If you have a question on a subject any not covered here, please help support this page by using our on-line enquiry form (requires Java Script to be enabled).

Much of the material here has been taken from topics presented at out monthly meetings. If any member has subject they would like to present for 15-20 miniutes as a 'second half' topic, please contact the Meetings Secretary (to contribute directly to this page, please contact the Webmaster

(+) 0001 How do I find a local Astronomical Society ?

(+) 0002 How is Star brightness measured ?

(-) 0003 What are the Constellations ?

The Constellations The stars you see in the night sky are positioned more or less at random. However the human brain is always looking for patterns .. so from the earliest civilization, observers have 'grouped' together the brighter stars as 'constellations' and imagined them as 'shapes' marking out their gods, heroes, animals or other objects of myth and legend. Each such constellation had a meaning or 'story' associated with it. Different cultures saw different shapes and thus formed different 'stories'. In the Northern hemisphere, Western world, our cultural heritage traces back to the ancient Greeks and so the shapes and names of our constellation are based on 3rd century BC Greek mythology, as noted by Ptolemy who named 48 different constellations. Our names for the Southern hemisphere constellations were generated much later (in the 17th century) by Mayer and Hevelius. Most are names of birds or scientific instruments like Tucan, Octant, Sectant, and even 'Microscope' ! Whilst most of the brighter stars were 'always' linked together to form the major constellations, dimmer and more isolated stars and the boundaries between constellations were rather imprecise for a long time. At the end of the 19th century there were 100 different constellations ! In 1922 the IAU revised all boundaries are removed some constellations. The official number is now 88. From our latitude (52 N) a number of constellations are circumpolar (i.e. far enough North in the sky as to be visible throughout the year) These are: Auriga, Camelopardalis (Cam), Cassiopeia (Cass), Cepheus (Ceph), Draco (Dra), Lynx (Lnx), Perseus (Per), Ursa Major (Uma), and Ursa Minor (Umi). Parts of Her, Lyra,  Cyg, And, Aug can also be seen all year round,   The southern most first magnitude star seen from our latitude (52 N) is Formalhaut in Pisces Austrinus. Below and to the right of Canis Major is the constellation of COLUMBIA (The Dove) and in the spring the stars of Centaurus just pop above the horizon The largest in area is Hydra (at 1302 sq deg), the 2nd Virgo (1294), the 3rd Ursa Major (1279), down to the 88th Equuleus (71) and 89th Crux (68). There are 12 'Zodiacal' constellations (these are the ones associated with the nonsense belief of 'Astrology', an ancient pseudo-religious system that claims your life and personality are 'fixed' by the stars (and planets) that WOULD have been behind the Sun ('the Sun is in') on the date of your birth 2200 or so years ago when this garbage was written down (precession of the Earths orbit, unknown to the 'Astrologers' at the time, means that their nonsense Zodiac based system is now some 30 degrees out = see link at end). One very well promoted claim is that Astrology can 'reveal your future' when 'performed' by some confidence trickster who 'casts' your 'horoscope' in exchange for large amounts of money (and avoids the Law on Fraud by claiming that they are being paid 'for entertainment only'). If you really want to upset an Astronomer (and hear a lot more like this), ask him or her for their 'Star (Sun) Sign' .... ). For what it's worth, these are the 12 'Zodiacal' constellations :- Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, (Ophuchus) Sagittarius,  Capricorn, Aquarius, Pisces. The Milky Way (the stars seen when looking toward the center of our galaxy) runs through Cas, Per Aur, and down into Canis Major, through the southern sky, and up though Scorpio, Sag, Aquila and Cygnus. Identification. In our light polluted sky's it's actually quite easy to make out the major constellations (since only the brightest stars are visible). Starting points are the well known ones - Ursa Major, Cassiopeia, Orion and the 'Summer Triangle' (Cygnus). The best way to learn for most is to install Stellarium (on a laptop) or Google Sky Map (on a tablet), 'turn on' the constallation lines and labels and look up at the sky ! The constellations visible during the year change as the Earth orbits the Sun (and the night side 'points' in a different direction) The 'most visible' constellations looking South at Midnight :- December   (Winter)    Taurus (and the Pleiads), Orion, Gemini, March         (Spring)    Cancer, Leo, Virgo June          (Summer)  Bootes, Hercules, Scorpio Cygnus, Lyra September  (Autumn)   Andromeda, Pieces, Pises Austrinus
This note last modified: 5th Feb 2015 22:05.


(+) 0004 What is the shape of the Earth ?

(+) 0005 What equipment do I need to start astronomy ?

(+) 0007 What telescope should I buy ?

(+) 0008 How much Magnification can I get ?

(+) 0013 What are Equatorial and Alt Az mounts ?

(+) 0100 How do I use my first telescope ?

(+) 0109 What is a finder ?

(+) 0110 What is an eyepiece ?

(+) 0111 What is a Barlow ?

(+) 0112 What is a focal reducer ?

(+) 0114 What are Nebular filters ?

(+) 0116 How do I use Setting Circles ?

(+) 0120 What is collimation ?

(+) 0125 How can I safely observe the Sun ?

(+) 1030 How can I take photos of the stars ?

(+) 1033 How to take photos of the Aurora ? - (Northern Lights)

(+) 1035 How to calculate FOV for prime focus ?

(+) 1036 How do I calculate FOV for Eyepiece projection ?

(+) 1037 How do I use a Raspberry Pi camera for astrophotography ?

(+) 1038 What is Star trailing ?

(+) 1039 How can I take photos of Meteors ?

(+) 2100 What is Universal Time (UTC) ?

(+) 2114 What are AUs Parsecs and Light Years ?

(+) 2115 What is Bodes Law ?

(+) 3010 When was Neptune discovered ?

(+) 4000 How do I update Stellarium with new Comet data ?

(+) 5000 How To build the MAS (Raspberry Pi) photoframe ?