Definition of Terms
Reflection is the action of light changing direction when it bounces off a shiny surface like a mirror.
Refracting is the bending of light rays when they pass through two substances that have different densities. An example is when a spoon is placed in a glass of water. At the point where the spoon emerges in water, it looks bent.
Catadioptric Telescope is a telescope that uses several mirrors and lenses. This increases the effectiveness of the focal length of the telescope. The word Catadioptric is a derivative of two words, catoptrics and dioptric. Catoptrics is an optical system that uses mirrors while dioptric is an optical system that uses lenses.
Newtonian Telescope was invented by Sir Isaac Newton. He used a concave mirror and a flat diagonal mirror. It is a type of reflecting telescope. Newtonian telescope’s design is copied by most of the amateur telescope makers because of its simplicity.
Cassegrain is a type of telescope that uses several mirrors or lenses which form an image by folding the optics. Light enters through a thin correcting lens and strikes a primary spherical mirror and is reflected in a secondary mirror. It is used mostly with the modern complex telescopes.
Aperture is the diameter on a telescope’s main lens which gathers light.
Focal Length is the distance between the lens or mirror and the point where the light rays come to a focus. The focal length determines magnification.
A telescope has a mirror that reflects light from objects to be observed to form an image. This is the objective mirror.
A secondary mirror or lens is the second mirror that receives light from the main primary mirror. It is usually a relatively smaller mirror. It has a reflecting or focusing mirror element in a reflecting telescope.
The field of view is the area that can be viewed through an optical instrument. For example, it is the area of the sky that is visible when observing through a telescope.
Ritchey–Chrétien telescope at George Mason University
It is a type of Cassegrain telescope with a primary and secondary mirror which eliminates optical errors. Light comes in via a thin aspheric primary lens. A small convex secondary mirror reflects the light through an aperture at the end of the instrument where the image is formed.
Advantage of the Ritchey–Chrétien telescope
The field of view for this telescope is large. This property helps in preventing optical errors.
The disadvantage of the use of Ritchey–Chrétien telescope
This telescope has a serious field curvature. It also suffers severe large-angle astigmatism. The telescope is also quite expensive.
Telescope Observation
Observation Information
Date of observation: Tuesday 13 November 2012.
Time of observation: 7:30 PM.
Weather conditions: The weather was not very clear. It was a bit windy with an approximate temperature of 10o C.
Telescopes: I looked through the main Mason telescope.
Direction telescope was pointed: The telescope was directed towards South East.
Observation Report
I first tried looking for the planets with my naked eye but it was not possible. Without the telescope, nothing much could be observed apart from the planets being bright celestial bodies in the sky. With the telescope, it was very easy and impressive to observe the planets. I saw Jupiter and it was an awesome sight to view. I managed to see what appeared to be the planet’s equatorial bands and its four main moons. The planets appeared to be very bright. They seemed to have shades of grey and white. However, the details about the color of the planet were not very clear. I marveled at how everything was twinkling as I viewed the galaxy through the telescope. I also observed that the striations on Jupiter’s surface are more visible when the magnification factor of the telescope is pushed up.
The synopsis of the presentation at the George Mason University Observatory
I attended a presentation by Dr. Shobita Satyapal at The George Mason University Observatory on Tuesday 13 November 2012. Dr. Satyapal talked about the James Webb Space Telescope. During the presentation, I learned that the James Webb Space Telescope is a big, infrared-optimized telescope that is being worked on by NASA. It is due for launch in 2018. According to Dr. Satyapal, the telescope will be able to locate the first galaxies that were formed during the beginning of the Universe.
He also added that the telescope will provide a connection between the Milky Way and the Big Bang theory. Dr. Satyapal also showed us some images of the telescope under construction. I learned some interesting facts about the James Webb telescope, for example, it is designed to work basically in the infrared range of the electromagnetic spectrum. It will have a sun shield which will be as big as a tennis court. It was interesting to also learn that the James Webb Space Telescope was named after a NASA employee who participated in the Apollo program. The presentation was very informative and interesting.