Editor: Christopher Michael Dagenbach
Date: December 7, 2008

Instrumentation in Astronomy is the measurement and process of efficiency in the work area. Instruments for Astronomy are devices developed to help astronomers decipher many of the mysteries in the Universe and allow them to see much further and clearer than ever before. The following Instruments that I will be discussing from six different websites that I came across include: Spectroscopy, Sextant, Photometer, Adaptive Optics, and CCD(Charge Coupled Device) Cameras.

Spectroscopy Revolution in Astronomy

Author: Blake Stacey
Date Read: 12/7/08
Audience: Anyone

Description of the website: The website itself contained much information of Spectroscopy and the uses of it. The website gave a thorough explanation of the topic and the topic and was easy to understand. It went on to explain in simple terms how it is used and how to understand the concepts and information behind it and also went deeper for people more acquainted with the topic. Not only did it explain the uses, how the theory works and how it is applied, but it also describes the history of both Spectroscopy and the Doppler effect along with all the steps that led up to both discoveries. It also goes over the nature of light and describes wavelengths.

Spectroscopy: Used with telescopes can shows what chemical properties celestial objects contain. With this information astronomers are able to tell the types of chemicals that stars burn. They can tell this because every chemical burns at a certain color and they can match those colors to the colors seen here that we have burned in those chemicals. By matching these colors we know what elements are inside a star. We could also determine if a star is closing at the end of its life if it is burning elements near iron which means it is nearing the end of the fusion chain. Spectroscopes can see many types of light waves including: visible light, radio waves, microwaves, infrared, ultraviolet light, x-rays, and gamma rays.

Doppler Effect: The Doppler Effect also is used because of Spectroscopy which can show from the length of light waves, from the spectroscope, if the object is moving towards or away from the Earth. These are called Blue or Red shifts which we can make predictions if a star is a binary star system or if a star has a planet moving around it because the gravity from the planet would pull and push the star away from us. This can lead to much more information.

external image doppler.jpg

How the Sextant Works

Author: Mr.Eugene Griessel
Date Read: 12/7/08
Audience: Anyone

Description of the website: The words in the website to my eye got somewhat lost in the messy background but other than how nice it looks the website shares a lot of knowledge about the Sextant itself. It discusses a brief history of how the name derives from the arc at the bottom being one sixth of a circle. It is simply explained on how to use it, what it is used for, and what it can help us discover. It is basically a measuring tool to measure how far an object is from the visible horizon. The information found on the website seems to be accurate and follows the basic themes and information that is covered on similar websites. I although used this website because it not only described the Sextant in detail and its use but it included instructions on how to use one. The website was simple to read and was user friendly for anyone that wished to learn how to use a Sextant or just to know what its purposes were.

Sextant: The Sextant can measure the degrees of an object is above the visible horizon. The Sextant itself has three major components including; a telescope, a mirror, and a moving arm. The arm moves to create a horizon and off the arm can be read the angles. One side of the angled mirror is a mirror and the other side is transparent. Once angled properly you can look through the telescope and line of the celestial body with anything on the horizon. Once this is done you read off the measurements that are shown.

external image sextant1.jpg

Photometers: Measuring the brightness of celestial objects

Author: ASTROLab
Date Read: 12/7/08
Audience: Anyone

Description of the website: I found this website to be very helpful compared to others researched because it was not filled with equations and it was not hard to read. This website was very helpful in explaining what photometers do and how they are used by astronomers and for what purposes. Not do explain what it is and how it is used but they also go over who discovered the beginning development of the photometer and go over the history of who had a hand in the development.
It also goes over luminosity which determines what a photometer reads. Luminosity depends on the temperature, the size of the surface, and the distance it is from the Earth. There could also be other things such as clouds in space that can dim the object. All of this can be factored in to get an accurate reading. Astronomers can also use this to find out its chemical composition to match it to colors of elements burned here on Earth.

A photometer is used to measure and express the brightness of any celestial object. This includes but is not limited to galaxies, stars, and planets. For a star the photometer can determine its age, temperature, and the distance from Earth. Since a photometer measures the luminosity of an object it can also see if that light changes which can determine if a planet orbits in front of it from our perspective. All of this information can be found in the above website.

external image HR_diagram.png

Introduction to Adaptive Optics and Its History

Author: Claire Max
Adaptive Optics
Date Read: 12/7/08
Audience: Anyone

Description of the website: This website is a document made by Claire Max at UC Santa Cruz studying in a Laboratory for Astronomy. Among all other websites he goes over each step from the beginning as if he was teaching it to someone. The includes why it is needed for astronomers to observe, how adaptive optics actually work, using laser guide stars which lasers create artificial stars, and how adaptive optics came to be. He then discusses how adaptive optics works and what makes it possible, along with how telescopes on Earth now compare to telescopes in space with this new technology.

Adaptive Optics: Because of our atmosphere astronomers have many problems when trying to observe space. Our atmosphere has air turbulence which makes it so that star light is stretched out making them look like large blobs. This blurring of stars makes even the most expensive telescopes in the world look not much better than a regular telescope bought at Walmart. This is why scientist sent telescopes into space to retrieve better images. Blurring caused scientist to come up with adaptive optics which would eliminate turbulence and give astronomers here on earth non-blurred images while researching. In a short explanation telescopes use a star close to a galaxy they are trying to observe and light from both objects are then calculated in a computer and the turbulence it then factored out of the image which leaves astronomers with a clear picture of both the “guide star” and the galaxy. All of this information and more can be found on that website listed above.

external image keck_adaptive_optics_images600x317.jpg

Charge-coupled device

Author: Wikipedia
Date Read: 12/7/08
Audience: Anyone

Description of website: I searched for many different websites that would explain CCD’s and their use in astronomy but in the end I resorted to use Wikipedia. I had only one other site that explained CCD’s in any detail and their uses but I chose Wikipedia because it contained specific details and thoroughly explained everything whereas the other source did not. The site goes over everything including CCD’s, the history, their uses, and it even explains in more detail how they operate and function than any other site that I came across in my search. Although Wikipedia can be edited by anyone I feel that from what I read on other sites all of the information found on this site was viable and that it out classed all of the other sites that I found that tried to explain and describe CCD’s.

CCD’s: A CCD stand for a charge coupled device which is used to create images of objects in space with more accuracy, definition, and faster. Before CCD’s were around astronomers used film and plates to make images of objects throughout the universe which took hours to do so having to expose it to light. Not only did it take longer but the images were nowhere near as effective as a CCD. In short CCD’s are little pixels on a piece of silicon that can absorb many protons compared to anything else and electrically charge the pixels to create more defined. Astronomers take several photos with the CCD’s with closed and open shutters. The closed shutter pictures can then be removed from open shutter pictures. This is used to remove disturbances like infrared light or anything else that may distort the picture.

external image a4310_ccd3_g.jpg

Edited by Chris Thomson__ on 12/07/08

Instrumentation is used to observe stellar objects with greater precision, and also to predict future projections. most of the most rudementary instruments are items such as:
external image MyAstrolabe.gif
the astrolabe is an ancient device that dates back to the 15th and 16th century it was used to predict the star patterns.
also used is the sextantA sextant is an instrument generally used to measure the altitude of a celestial object above the horizon. Making this measurement is known as sighting the object, shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical or aeronautical chart. A common use of the sextant is to sight the sun at noon to find one's latitude. See celestial navigation for more discussion. Held horizontally, the sextant can be used to measure the angle between any two objects, such as between two lighthouses, which will, similarly, allow for calculation of a line of position on a chart. This website was very informative and was good for information even though it was wikipedia which i believe is still a credible site. it is good for reference because it is constantly corrected by scientists of at least people who know something about it
external image sextcaptain1.169144704_std.jpg

Around 1730, an English mathematician, John Hadley (1682–1744), and an American inventor, Thomas Godfrey (1704–1749), independently invented the sextant. The sextant provided mariners with a more accurate means of determining the angle between the horizon and the Sun, moon, or stars in order to calculate latitude. this site is good as well because the man who wrote it was doing a project as well and did his homework as well.

Two men independently developed the octant around 1730: John Hadley (1682-1744), an English mathematician, and Thomas Godfrey (1704-1749), a glazier in Philadelphia. While both have a legitimate and equal claim to the invention, Hadley generally gets the greater share of the credit. This simply reflects the central role that London and the Royal Society played in the history of scientific instruments in the 18th century. Those outside the social circles within London and the Royal Society did not get the historical attention they deserved.
http://en.wikipedia.org/wiki/Octant_(instrument) Another wikipedia reference, it was backed up by several other cross references about the history and uses of the octant. I recommend it to other users.

external image 180px-Oktant.jpg

Celestial navigation is the process whereby angles between objects in the sky (celestial objects) and the horizon are used to locate one's position on the globe. At any given instant of time, any celestial object (e.g. the Moon, Jupiter, navigational star Spica) will be located directly over a particular geographic position on the Earth. This geographic position is known as the celestial object’s subpoint, and its location (e.g. its latitude and longitude) can be determined by referring to tables in a nautical or air almanac.
The measured angle between the celestial object and the horizon is directly related to the distance between the subpoint and the observer, and this measurement is used to define a circle on the surface of the Earth called a celestial line of position (LOP). The size and location of this circular line of position can be determined using mathematical or graphical methods (discussed below). The LOP is significant because the celestial object would be observed to be at the same angle above the horizon from any point along its circumference at that instant.
An example illustrating the concept behind the intercept method for determining one’s position is shown in the Figure below. (Two other common methods for determining one’s position using celestial navigation are the longitude by chronometer and ex-meridian methods.) In the image below, the two circles on the map represent lines of position for the Sun and Moon at 1200 GMT on October 29, 2005. At this time, a navigator on a ship at sea measured the Moon to be 56 degrees above the horizon using a sextant. Ten minutes later, the Sun was observed to be 40 degrees above the horizon. Lines of position were then calculated and plotted for each of these observations. Since both the Sun and Moon were observed at their respective angles from the same location, the navigator would have to be located at one of the two locations where the circles cross.
In this case the navigator is either located on the Atlantic Ocean, about 350 nautical miles (650 km) west of Madeira, or in South America, about 90 nautical miles (170 km) southwest of Asunción, Paraguay. In most cases, determining which of the two intersections is the correct one is obvious to the observer because they are often thousands of miles apart. As it is unlikely that the ship is sailing across the Pampas, the position in the Atlantic is the correct one. Note that the lines of position in the figure are distorted because of the map’s projection; they would be circular if plotted on a globe.
This page was very wordy and overall correct and easy to read. it was informative and yet time consuming. it is good references for those who have time to read the whole idea.