FAQ on Discovering SOHO "Sungrazers" using just a computer, an internet connection and some time.
What is SOHO? SOHO (Solar and Helioscopic Observatory) is a project of international cooperation between the NASA and European Space Agency (ESA). The spacecraft was launched on December 2, 1995 to provide continuous surveillence of the Sun's activity at many wavelengths. The spacecraft has gained the reputation of being the most prolific comet finder in the history of astronomy as it has discovered more than 420 comets in just under six years. Most of the comets were first spotted by amateurs around the world who downloaded SOHO's real-time images to their home computers. Anyone with Internet access can take part in the hunt for new comets. SOHO Homepage: Which type of comets to expect in SOHO images? More than 90% of the SOHO comets belongs to Kreutz family of Sungrazing comets. What all data is available to search for SOHO comets and where is it? The images from C2 and C3 coronagraphs of the LASCO (Large Angle and Spectrometric Coronagraph) instrument of SOHO are used to hunt for SOHO comets. Usually new C2 images arrive 3 times in an hour and C3 images arrive two times in an hour. Useful Data:
What is the difference between C2 and C3 cameras?
Which images to prefer, C2 or C3? Bright comets are first visible in C3 images, while some faint comets only become visible when they enter C2 images. You decide which images do you want to spend most of your time on. How to hunt for comets in the SOHO images? The most common technique is to blink/animate (in a loop) atlest 4 images taken consecutively and carefully look for anything moving w.r.t the stars in them. There are a lot of random cosmic-ray artifacts present in the images as the SOHO is sitting outside Earth's atmosphere, so make sure you can differentiate between a real object and such artifacts. A comet will appear to move equal interval in equal interval of time, will not be moving very fast, will remain constant in brightness and shape or vary predictably and will be visible in all consecutive frames. You should not be in a hurry, it can take weeks before you discover your first comet. More information about artifacts in SOHO images is available at SOHO LASCO Comet Finders' Page. Where to look for in an image to maximize the probability of locating a comet? Since more than 90% of the SOHO comets belongs to Kreutz family of Sungrazing comets, We should look where their trajectories are expected. Kreutz expected trajectories: http://www.ph.u-net.com/comets/c2paths.htm Chances of finding a comet elsewhere in the field are very little. How to animate/blink images? Simplest way is to save the images you want to blink in a common folder and run them in a slideshow using commonly available ACDSee image viewer. Delay can be adjusted from the 'Options' dialog box. Otherwise programs like Ulead GIF Animator or Adobe ImageReady can be used to produced an animated GIF file. I think I have found a comet, now what?
How to find the X and Y coordinates of a pixel in an Image? Open the image in Adobe Photoshop or ImageReady. X, Y coordinates of the pixel at the position of the mouse pointer are visible in 'Info' window (top left corner of the image is 0,0). Info window shows the coordinates in one of the many units (Pixels, Inches, Centimeteres ...), to view it in Pixels, left-click on the '+' sign that appears in info window and select 'Pixels' in the menu that appears. The ACDSee version 2.3 (which I have) does not show X, Y coordinates What all information is needed to report a discovery?
Remember that an object should appear in at least 4 consecutive frames to be considered real. Sample Report: ----------------------------------------------------------------------- A possible Kreutz comet in real-time images. Brief Description: The object is faint and condensed, a faint tail also visible. Date Time Tel Position YYYY/MM/DD (UT) (Col, Row)* 2002/05/12 23:50 C2 (431,1021) 2002/05/13 00:06 C2 (436,1013) 2002/05/13 00:26 C2 (445,999) 2002/05/13 00:50 C2 (454,982) * Coordinates mesured in 1024x1024 images, (0,0) is top-left corner. ----------------------------------------------------------------------- Will I get to name my discovery? You will be given credit as the discoverer but the comet will be named after the spacecraft, something like 'SOHO, C/2002 C5'. Is there a mailing list of SOHO comet hunters? Yes! Here is one: http://groups.yahoo.com/group/sohohunter References:
Author: Vikrant Narang Member, Amateur Astronomers Association of Delhi FAQ Last Updated on: 05/25/2002 http://www.oocities.org/vikrant_narang/soho_comet_hunt_faq.html |