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 ?
Collimation is the process of aligning your telescopes optical components so that they 'line up' perfectly. Although all telescopes will be collimated in the factory, only the glass lenses will be glued and sealed into place. The mirror components will be aligned using locking screws, however because the mirrors of Newtonian are much thicker than the lenses in a refractor, expansion and contraction as the temperature changes means the mounting has to be allowed to 'give' a little (otherwise the glass would crack).
Over time this expansion and contraction can lead to the mirror moving and becoming out of alignment. It is also quite possible for the optical components of a reflecting telescope (Mirror / flat / eyepiece) to become misaligned during transportation (although a small misalignment might not be noticeable, large miss-alignment makes it impossible to focus correctly (stars always appear as 'donuts').
To correctly collimate really needs a laser collimation tool - and since incorrect adjustment of the mirror mounting collimation screws can make things worse very quickly you need to be quite careful
Collimation is not a task for most beginners, however quite a few MAS members have the required tool and will be only too happy to assist at one of our meetings. We also hold 'Telescope Workshops' at least once a year for the public where your telescope will be checked and collimated (if necessary) by our members without charge.
If you purchased your telescope from a specialist retail supplier, most will be quite happy to help you with some free 'after sales service', however watch out for the commission hungry salesman who will try to convince you to purchase an over-priced collimation tool. A collimator can be found for about half the retail price on eBay/Amazon - and even less if you are prepared to wait whilst one is shipped direct from the manufacturers (all of whom are in China :-) )
This note last modified: 5th Feb 2015 22:05.
(+) 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 ?