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=List and explain the different types of observing and be able to use each type.=

There are four different ways of observing variable stars. There is visual, photometric, remote/CCD, and spectroscopy.

**(Taken from the [|AAVSO] website)**

 * 1) Find the field using an atlas or star chart. Look up and locate the field or region of the sky in which the variable is located. This is where knowing the constellations will be very helpful. Take out your "a" or "b" scale chart and orient it so that it matches what you see in the sky.
 * 2) Find the variable. Look at the "a" or "b" chart and pick out a bright "key star" that appears near the variable. Now look up and try to find this same star in the sky. If you cannot see the key star with your unaided eye (due to moonlight or other adverse conditions), use a finder scope or a very low-power, wide field eyepiece and point the telescope as closely as possible to the position in the sky where the key star should be. Verify that you have spotted the correct key star by identifying fainter telescopic stars near it, as shown on the chart. Now progress slowly, "star-hop," in the direction of the variable, identifying star configurations as you go, until you become very familiar with the field. It will take many glances -from the chart, to the sky, then through the finder scope, and back again-until you reach the star configuration in the immediate vicinity of the variable. Take your time to ensure proper identification.
 * //Second continued, Find the variable (using setting circles).// If your telescope is equipped with fairly accurate setting circles (regular or digital), this may be your choice for finding variable star fields. Before starting, ensure that your telescope is properly aligned. The 2000 coordinates which appear at the top of the chart should then be used to "dial" in the variable. The variable may not be immediately apparent. Even though it might be in the field of view, you will still need to identify the stars in the immediate vicinity of the variable for positive confirmation.
 * 1) Find the comparison stars. Proceed with making an estimate of its brightness by comparing it with other stars of fixed, known brightness. These comparison stars are generally located near the variable on the chart. Find them through your telescope.
 * 2) Estimate brightness. To estimate the magnitude of a variable star, determine which comparison star or stars are closest in brightness to the variable. Unless the variable is exactly the same brightness as one of the comp stars, you will have to interpolate between a star that is brighter and a star that is fainter than the variable itself.
 * 3) Record your observations. Include name and designation of the variable, the date and time of your observations, the magnitude estimates for the variable, magnitudes of the comparison stars used to estimate, identification card used, and notes on the conditions which might effect seeing.
 * 4) Prepare your report. There is a very specific format for reporting your observations and there are several ways to submit your reports to AAVSO Headquarters. The preferred and by far the easiest way to submit observations to Headquarters is through the AAVSO website. There, you will find a system called [|WebObs], you first have to be a registered user to use this site, that takes your observations and automatically submits them to the AAVSO. When you submit observations online, WebObs will automatically format them to AAVSO specifications.



**__Photometry__**
The photometry way of observing involves the use of a stellar photometer. A stellar photometer is an electrical device that measures the amount of light received from a single star. This process is called photoelectric photometry. "Photoelectric photometry is a means of measuring starlight. Star light is extremely feeble. Photoelectric photometers are sensitive enough to measure individual photons. Filters can be used to determine the color (UBV) of the star light." ([|Photoelectric Photometry])

To observe a star, you take the instrument and point it at your variable star. You record the readout of the amount of light that you receive from the star. Next, you do the same thing for the comparison star(s). You do this a couple of times to make sure that your readouts aren’t deceptive. It’s a very simple process.

Photon Counting Astronomical Photoelectric Photometer System



**__Remote/CCD__**
CCD stands for charge coupled device. A CCD is a digital camera. You can take exposures lasting several minutes with a CCD. CCDs will allow you to see things that you missed when you were using just your eyes. (__Observing Variable Stars__)

__NMSO observing process at Jordan Hall__
Information taken from [|New Mexico Skies Observatory Document]:


 * 1) Get an account with the NMSO site. (Dr. L should already have this for you.)
 * 2) You should obtain a few different targets that you wish to observe.
 * 3) Gather information about the star, such as its coordinates and other star identifiers. A good site to find other star identifiers is http://simbad.u-strasbg.fr/simbad/. Also, obtain sky charts and/or obtain a star atlas.
 * 4) Sign up for a time that you wish to observe. Remember that New Mexico Skies is in a different time zone. [|http://12.196.245.92] is the site where you will sign up for times.
 * 5) Go to your night of observing at Jordan Hall with Dr. L or another adult associate.
 * 6) Sign on to your account at your time of observing. You can sign on a little earlier than your scheduled time.
 * 7) Type in either the coordinates, name of your star, or another star identifier and click on the button ‘slew to’ to get to your variable star.
 * 8) Set up your camera
 * 9) Your camera settings should initially be:
 * **Frame type: Light** (this is the proper setting for taking an image of an object)
 * **Filter: default** (this is where you change filters one at a time**)**
 * **Binning: 2 x 2** (Note: if you use any other binning setting, you will need to change your exposure lengths accordingly and your images will not be reduced from the library of reduction frames)
 * **Delay: 5** (or 10 seconds to allow the telescope to settle down after slewing)
 * **Field of view: 100**
 * **Subframe: not checked**, i.e. off
 * **Reduction: Bias, Dark, Flat** //__(Note: this is the library of photometrically accurate reduction frames, available only for images binned 2x2)__//
 * **Group: Imager**
 * 1) The “Fast (small) Previews” box should be checked
 * 2) **Check the box “Set as my defaults” and click Submit**
 * 3) Set exposure time in seconds, the number of images you want to take, and if you want, you can center your target.
 * 4) If you wish to create a color image go to ‘change settings’ and start with these filter settings.
 * Try starting with these settings*:
 * Filter: Luminance
 * Number of images: 5
 * Length of each image: 3 minutes
 * Filter: Red
 * Number of images: 3
 * Length of image: 2 ½ minute
 * Filter: Green
 * Number of images: 2
 * Length of each image: 2 ½ minutes
 * Filter: Blue
 * Number of images: 1
 * Length of each image: 3 minutes 45 seconds
 * The ratio of color imaging time for this camera/telescope combination should be:
 * Red-1.5, Green-1, Blue-.75. You can achieve this by balancing the lengths of exposures and/or the number. Be careful not to double the ratios if you change both.
 * Note that the exposure time for each of your luminance images will depend on the brightness of your object.
 * 1) Eleventh, take as many images as you want. You can obtain these images the next day by going to **ftp://12.196.245.92/with your User Name here.** You can then download these images and place them on your desktop and/or right click them to enter your destination.

**__Spectroscopy__**
"In spectroscopy, incoming light—such as that from a star—is passed through a grating or a prism that splits the light up into its constituent wavelength, or colors. Normally, a very bright, hot star will emit a continuous spectrum of light that spreads like a rainbow across the electromagnetic spectrum. In the case of lower density gas masses such as nebulae, however, the light will be emitted only at certain specific wavelengths defined by the elements found in the nebula—hydrogen atoms, for example—generate vivid yellow lines at characteristic wavelengths. The spectra will thus consist of a collection of bright lines in an otherwise dark background; this is called an emission spectrum. Similarly, if a star is surrounded by a cooler atmosphere, the atoms in the atmosphere will absorb certain wavelengths, leaving dark lines in what would otherwise be a continuum. This is known as an absorption spectrum." ([|Astronomy Spectroscopy])



"Scientists study absorption and emission spectra to discover the elements present in stars, galaxies, gas clouds, or planet-forming nebulae. By monitoring the amount by which spectroscopic lines shift toward red wavelengths or toward blue wavelengths, astronomers can determine whether objects are moving toward or away from the Earth. This technique, based on the Doppler shift, is not only used to help astronomers study the expansion of the universe, but to determine the distance or age of the object under study. By studying the Doppler shift of stellar spectra, astronomers have been able to monitor faint wobbles in the motion of stars that indicate the presence of a companion star or even of extrasolar planets." ([|Astronomy Spectroscopy])

References: http://www.hposoft.com/Astro/PEP.html http://imagine.gsfc.nasa.gov/docs/science/how_l1/spectra.html http://www.aavso.org/publications/manual/chapter2.shtml http://www.aavso.org/publications/manual/chapter6.shtml http://science.jrank.org/pages/582/Astronomy-Spectroscopy.html [|NMSO Instructions.doc] __Observing Variable Stars__ by Gerry A. Good