Reducing analyzing and reporting asteroid occultation timings

If you used the stopwatch method or the video recording'' method to observe the occultation, then the time reductions are done in exactly the same way as was described in the lunar occupations'' project (see Section 2.1.3). If you used the CCD drift scan'' method, then data reduction consists of translating image position along the star trail into time. This isn't too hard, if you can dredge up memories of the geometry that you learned in high school. Use your image-processing software to...

Nova And Supernova Searches

Stellar explosions are important laboratories for understanding the physics of stars. Before they can be studied, they must be found Since they are relatively short-lived events, finding them requires continual searching and amateur astronomers have demonstrated the necessary skill and persistence to succeed in this endeavor. By conducting a nova or supernova search in a consistent way you can contribute to the effort to understand these events, in three ways. By discovering a newly-exploded...

Reporting your results

The publication that is dedicated to disseminating double-star measurements in the USA is The Journal of Double Star Observations, published by the University Figure 5.7. The close-pair HD 121325 (WDS 13550-0804) is just past the limit of my system's capability. (a) The star images are barely separated in this 3-sec CCD image, making it difficult to place a measuring aperture on one star that isn't corrupted by light from the other star. (b) The intensity profile through the stars shows a...

Comparing your observations with others data

After you've made some measurements of a variable star, you may be curious as to how your observations fit in with other's measurements of your star. This information is also easily available on the AAVSO website, as immediately-downloadable unvalidated data. Unvalidated data has not been subjected to AAVSO's checking and analysis process, and should not be used for formal reports or publication. It represents the sum of all observer reports, as received. When an astronomer requests AAVSO data...

General Principles Of Aperture Photometry

In order to put this into a practical context, we'll go through an example that will explain the procedure for CCD photometry. Then we'll deal with some important details related to image processing, calibration, and measurement. Figure 4.7 is an image of the field of view that contains the cataclysmic variable star V378 Peg'' (except of course when you take your own image, it won't include the arrow to identify the star of interest ). As you probably know, the CCD image is made up of pixels,...

D2 Uncertainty Accuracy Vs Precision

There is an important distinction to be made in evaluating the quality of a measurement the difference between accuracy and precision. These two terms can be roughly explained by considering the ruler vs. the micrometer. Precision relates to the number of significant decimal places in the measurement, or the instrument's ability to reliably and repeatedly read out a measurement. As we have seen, with the ruler you are capable of making a reading to about 0.03 inch, whereas with the micrometer...

Making the observations

Measuring an asteroid's lightcurve uses techniques that are very similar to those used for variable stars. In general, everyone uses differential photometry to track the brightness of the asteroid relative to one or more comp stars. Pretty much everything that was discussed under variable stars'' is also appropriate for asteroid photometry select an exposure duration that will give you a good signal-to-noise ratio without saturating any star images save your raw images in FITS format do not...

B3 Plate Constants

The illustrative example presented in Figure 5.1 was described as if the pixel array in your CCD image formed a perfect representation of the RA-Dec grid of the celestial coordinate frame. That made the explanation simple to follow (1 hope), and isn't too misleading since the more realistic assumptions and corresponding detailed calculations that are actually involved are done by your astrometry-reduction software, not by you. So, in most cases you can treat the astrometry software as a black...

Telescope considerations

Virtually any sort of observing equipment can be effectively used for variable star monitoring. The nature of your equipment will play a role in selecting the stars that you put into your observing program. With my 7 x 50 binoculars, I can follow stars to about magnitude 7.5. With my 16 Dobsonian, stars down to about 14th magnitude are available to me. There are plenty of stars in both magnitude ranges needing regular observation, so you need not be concerned that your equipment is too modest...

Submitting your observations

The central organization whose mission is to gather, analyze, and disseminate variable star observations is the AAVSO. Although it has a North American focus, it is open to all variable star observers, worldwide. Before you can submit observations to the AAVSO, you must request and receive an observer code'' to identify yourself and link all of your submitted observations to your credit. Any variable star observer can request an observer code you do not have to be a member of AAVSO (although if...

Specialpurpose period analysis programs

There are precise mathematical methods to piece together lightcurve segments into a complete lightcurve. One popular algorithm is based on a special application of Figure 4.26. Two nights' asteroid lightcurve data, wrapped to the best-fit rotation period. Figure 4.26. Two nights' asteroid lightcurve data, wrapped to the best-fit rotation period. Fourier analysis. The two readily-available software packages that I'm aware of that implement this Fourier algorithm are Peranso by Tonny Vanmunster,...

Introduction

The foundations of astronomy were laid by a cast of dedicated observers, craftsmen, and thinkers, many of whom were, in a sense, amateurs. Their scientific efforts were driven by a thirst for knowledge and the joy of discovery, and they funded their research from resources provided by their non-astronomical day jobs. Galileo built his own little telescopes, and saw things that no man had seen (and few had imagined), while scheming for a salary increase for his job as professor of mechanics....

The standard BVR photometric system

In the introductory section of this chapter, I mentioned in passing that the star Vega is the fundamental reference star of most photometric systems it is not just a magnitude-zero star'', it is the definition of magnitude-zero brightness.* The brightness of every other star in the sky the ones we know as 3rd magnitude'' or 8.5 magnitude'' was determined by measuring their brightness relative to Vega (either directly, or indirectly), and applying the fundamental magnitude equation If you like...

Absolute vs differential photometry

The discussion above implicitly assumed that the comp star'' was in the same image as the target star, and that we were happy to monitor the brightness of the target relative to the comp star. In some cases, we might not know the true magnitude of the comp star, but that's OK since the variation of the target is completely described by its light curve relative to the comparison. Since we determined the magnitude difference between target and comp stars, this method is called differential...

Matching telescope and CCD

There is a uniquely astrometric concern regarding the choice of telescope and imager the telescope's focal length must be long enough that the star images are larger than a single pixel. This is because accurate astrometry requires that the star images be wellsampled, as illustrated in Figure 5.2. The rationale for this sampling requirement is not too hard to understand. If you have a tiny star wallowing inside a large pixel, you can't tell where in the pixel the star is located. Hence, your...

Software packages for photometry

Doing the four steps (select aperture size, measure star + sky'', measure sky-only, and subtract to get star-only) for two or three stars on each image, and then repeating for several images, is a tedious and error-prone process if you do it manually. Happily, all of the most popular astronomical image-processing software programs include routines that automate most of these steps. CCDSoft (Software Bisque), AstroArt (MSB Software), MaximDL (Diffraction-Limited), MPO Canopus (BDW Publishing),...

Project M Separation And Position Angle Of Binary Stars

Binary stars provide important laboratories for determination of a variety of fundamental stellar properties. The widely-spaced visual binaries'' are particularly important because we can hope to observe their orbital motion, thereby measuring the star's paths around their common center of mass. That information can be used to determine the masses of the two stars. It is one of the very few unambiguous, direct ways of determining stellar mass. It thus provides an important anchor to...

Automating Your Meteor Observations

The meteor studies described in the previous sections require you to stay up pretty much all night, several nights in a row. Doing that for a well-known meteor shower can be a fun holiday from your normal schedule. Doing it in search of suspected (but not certain) sparse meteor showers will soon test your endurance, and may begin to interfere with your other activities (such as being wide-awake at work in the morning). So, after you've done a bit of this sort of science, you may wonder if you...

Radio Meteor Monitoring

Meteors don't cease their activity just because it's cloudy, or the Sun is up in the sky. The background flux of sporadics continues 24 hours per day, and there are meteor streams whose orbital geometry makes them most active during our daytime hours. Obviously, you can't see them visually with the Sun in the sky. It turns out that you can detect them using radio. Shortwave radio signals travel in straight lines, in the same sense that light waves do any single photon moves in a straight line...

Rainy Day Science Perusing The Professional Literature

Any amateur astronomer who is pursuing research activities will want to gain a bit of exposure to the professional studies that are being done in your area of interest. You will find it quite valuable to see the types of data that the professionals are using, the ways in which they display their results, and the conclusions that they draw from the data. There are two fine resources available to help you in this regard the internet, and the library. On the internet, the NASA Astrophysics Data...

Equipment needed

Visual comet hunting requires only the most fundamental equipment in the amateur astronomer's kit Your telescope, with an eyepiece giving you approximately a 1 degree field of view. (Optional) a planetarium program with a deep database of comets, asteroids, and deep-sky objects. Internet access (for use of the Minor Planet Center's databases to check any candidate objects). And, of course, the visual observing skills that you have learned and exercised over plenty of nights under the stars the...

Meteor And Fireball Photographicvideo Networks

In Section 1.3, I described the technique for plotting meteor paths onto a star chart, to determine their radiant positions (and possibly identify new radiants). Suppose that two observers, separated by 20 miles or so, were to observe and plot the same meteor. Theoretically, their plots would display the parallax of the meteor, which would enable them to determine its trajectory. Careful measurement of the starting and ending points of the trail would show the meteor's height at its start and...