The next monthly meeting of the East Antrim Astronomical Society will take place on Monday 12th May in the Lecture Theatre at Ballyclare High School, George Avenue (off Rashee Road), Ballyclare, Co. Antrim, commencing at 8PM.

Main Speaker: Mr. Barry Loane (IAA)
Subject: Building a home observatory

Barry Loane is an amateur astronomer from Newtownards, County Down who has designed and built a geodesic observatory. This is a hemispherical dome whose surface is formed out of short rods arranged in triangles which is a very efficient building method and creates a wonderful space-age observatory, an example of which is the Eden Project in Cornwall. He has also built his own grinding machine and is in the process of grinding his own mirror.

Barry will cover the many aspects and considerations of building an observatory and will include his personal experiences and trials in constructing his own.

The following is a basic guide to some of the factors to take into consideration when choosing eyepieces. It is based on my experience but also on conversations with and articles by other observers much more qualified then myself.

Eyepieces Terms

The choice of which eyepieces to purchase is almost as important as which telescope and mount to choose, eyepieces couple to our telescopes to give us our observing experiences and a bad choice of eyepieces will limit the experience as much as a bad choice of telescope. The best advice I can give to anyone contemplating a purchase of an eyepiece is...

Full article now available.

Here is a set of formulae and numbers that I have always wished was in one place.  Now they are.  Enjoy.

f ratio (or focal ratio) = ?

True field of view = ?

Eyepiece exit pupil diameter = ?

Lowest power useful eyepiece = ?

Find out the answers on our Astronomy Formulae article.