Thursday, January 21, 2016

Comet Calatina (akaComet C/2013 US10 Catalina)

Well, after about a three month hiatus, the skies cleared just enough on the morning of January 20, 2016 for me to capture Comet Catalina, just before the break of dawn (5:30 am to 6:30 am).

In the process of locating the comet a south-to-north satellite crossed just west of the comet (which is faintly in the lower right hand corner). What is interesting is the satellite track is fairly flat and straight until it passes the center of the image and then becomes progressively wobbly as it nears the lower right hand corner. This is not an artifact of the digital camera but is the rotation (flipping over and over again) of the satellite itself! I have photographed many satellites (quite unintentionally) and never have I seen this effect. (Taken with a Canon T3i, 135mm, 12 seconds @ ISO 12,800 set at f/5.)
Click on the photo for a larger image to view...

Also, in my search for the comet the International Space Station (ISS) passed closely (just not as closely) to the comet as well ! The three bright stars are part of the "handle" of the "Big Dipper" (aka Ursa Major). Yes, they have names! From top to bottom Alioth, Mizar (notice the little star just to the right of Mizar, it is Alcor, part of Mizar's triple star system) and Alkaid. The "bowl" of the Big Dipper is out of sight towards the top of this image. Can you spot the greenish blue comet? (Hint: near the top center of the photo, just right of the ISS trail.) Taken with a Canon T3i, 50mm, 22 seconds f/4 at ISO 12800. Click on the photo for a larger image to view...

Finally I was able, by steps, to increase the telephoto zoom lens until I was able to center Catalina in the screen. Then I set up my hand intervalometer to capture 60 - 1 second images using the Canon T3i set at 250mm, f/5.6 @ ISO 12,800.  The seeing (air quality) was not all that good with a lot of frozen moisture in the air (and some thin ice clouds all around) so capturing any kind of tail was nearly an impossibility. However there does seem to be a faint tail pointed away from the comet in the "10 o'clock" position. Click on the photo for a larger image to view...

While this image is nothing to "write home about" the amazing thing is that it was shot with a stationary camera (Canon T3i) on a tripod UNGUIDED. This is a "stacked" image made up of about 60 - 1 second exposures using the program "Deep Sky Stacker." The purpose of a lot of short exposures instead of one long exposure is that it minimized the graininess of high ISO settings (like this one pushed to ISO 12,800) and it decreased "sky glow". "Sky glow" can easily overwhelm faint details when one uses longer exposures (see the ISS photo above and compare it with this one... the ISS image was 22 seconds and the comet photo above is the equivalent of 60 seconds!) There is always a certain amount of ambient light in the night sky, most caused by human over-lighting of their property, and some caused by the refraction of light from the Moon or the Sun (just below the horizon.) So taking lots of "subs" (photos with insufficient exposure to bring out the subject matter) is the way to go!

UPDATE: The following image was created from 10 - 9 sec images @ ISO 1600 with a Canon XTI and a f/2.8 55mm zoom lens at about 3 am Dec. 19, 2016, stacked with Deep Sky Stacker. See if you can locate the comet (click on the image for a much larger display)! One thing is for sure, it is in a hurry! It moved a great distance in just one 24 hour period!

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