Click on the image for a larger viewThe image above is of Comet Garradd as it went by the globular cluster M71 in the constellation Sagitta back on August 26, 2011. This is the brightest comet in the sky right now, easily visible with a pair of binoculars, but with a couple of provisions. You need to view it away from the city lights and you need to know exactly where to look. Because comets are constantly on the move, you will need a star chart for the evening that you go out into the countryside. Click here to get some printable star charts for the next 6 months (courtesy of Sky and Telescope magazine) as it heads closer to the sun. Comet Garradd will be visible for quite a long time, so there should be no excuse of not having enough time to see it.
Are you wondering why the comet is green? One of the few green objects in the night sky, the color is caused by the Sun's ultraviolet light striking the cyanogen gas surrounding the star-like nucleus of the comet making it glow. The tail is composed of gas and dust, pushed away from the nucleus, by the pressure of light particles from the sun.
The globular cluster, M71, looks to be fairly close to the comet, but not really. At the time of the picture, the comet was about 130 million miles away from Earth. M71 is 13,000 light years away. To make it easier to compare the difference in distances, lets convert the comets distance in miles to light years. Light travels 186,000 miles per second. Dividing 130 million by 186,000 gives about 700 seconds. Now you can really see the difference: Light takes about 11.6 minutes to get from the comet to our eyes, but from where M71 is located, it takes light 13,000 years to travel from where it is located.
- Date Taken: Aug 26, 2011
- Location: ASKC Dark Sky Site
- Telescope: 190mm, f/5.3 Maksutov Newtonian
- Camera: Q453 CCD (similar to QHY8)
- Exposure: 30 minutes (consisting of 15 - 2 minute shots)
- Calibration: 20 Bias, 20 Flats, 1 Dark
- AutoGuider: Q-Guider with 50mm Finderscope
- Mount: Parallax Instruments HD 150C
- Capture Software: Nebulosity
- Calibration Software: Nebulosity
- Final Processing Software: Photoshop CS3