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MAS Frequently Asked Questions

MAS FAQ

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 ?

(+) 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 ?

N E P T U N E

At nearly 3000 million miles from the Sun, Neptune orbits once in 165 years. It has therefore not quite made a full circuit of the Sun since its discovery by  J.G. Galle and L. d'Arrest at the Berlin Observatory on 23 SEPTEMBER 1846.

The search for Neptune

The search for the planet was based on mathematical predictions by Le-Verrier and independent calculations by the British mathematician, John Couch Adams (based on slight 'imperfections' in the orbit of Uranus). Neptune is the eighth (and last) planet from the Sun and the smallest of our solar system's gas giants.  Even so, its volume would hold 60 Earths, and yet, owing to its great distance from us its barely discernible as a disk in a telescope except at high magnification.  Neptune had been identified as "planet x" and more recently it was realised that Galileo had seen Neptune in his crude telescope while looking at Jupiter in January 1613, but he had not realised he was seeing a new planet (it would have appeared as a single point i.e. looked like a star).

The background

Sixteen days after Galle and d'Arrest first saw Neptune, the British astronomer William Lassell (who in later life had an observatory at Ray Lodge, Maidenhead) discovered a moon of Neptune and named it Triton.  Triton is Neptune's largest satellite, almost the size of Earth's Moon, and it is the only satellite in the solar system to circle a planet in a retrograde direction -- in a direction opposite to the rotation of the planet.

The voyage

Voyager 2 was launched August 20, 1977 and visited gas giants: Jupiter in 1979, Saturn in 1981 and Uranus in 1986 before making a close approach to Neptune on August 25, 1989 after a 12 year voyage at an average speed of 19 Km per second (about 41,000 miles an hour).

The discoveries

Although Neptune receives only 3/100ths of the sunlight that Jupiter receives, it is never-the-less a dynamic planet with circulating atmospheric disturbances.  The largest feature found by Voyager was the "Great Dark Spot" a huge anticyclone at latitude 22 degrees south, similar to Jupiter's "Great Red Spot".  At about 42 degrees south was a feature called the "scooter" because it moved around the planet in16hrs.  Most of the winds blow westward which is opposite to the rotation of the planet, creating winds of 1500 miles per hour -- the strongest winds in the Solar system.

click here to visit N.A.S.A. and see Voyager's photos of Neptune On 23 Sept 1996 - NATIONAL ASTRONOMY WEEK (and MAS) COMMEMORATED THE DISCOVERY OF NEPTUNE
This note last modified: 26th Jan 2015 10:38.

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

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

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