ISS, The Moon, and a Comet

   This evening, December 27th, weather permitting, the International Space Station should be visible as it travels across northern mid-latitudes of North America. From my location near Kansas City Missouri the ISS will appear over the west-northwest horizon at approximately 6:13 pm CST, and be visible above my local horizon for 6 minutes before it disappears below the south-southeast horizon. Along the way it will reach a maximum altitude angle above the southwest horizon of 42 degrees; pass between two stars of the ‘Summer Triangle’, Altair and Vega; pass above the Planet Mars and Comet Finlay, and below the nearly first quarter Moon. At its greatest brightness the ISS will be between 1st and 2nd magnitude, brighter than the stars of the Big Dipper.

   Much of my information for the ISS comes from NASA’s ISS Sightings web site. From there you may tailor the predictions very specifically for your location. I then use an Astronomy program on the PC and also one on my Kindle to see the path it will follow and what if any other celestial objects it may pass. Read a little more about viewing the ISS and Iridium Flares, as well as suggestions for taking pictures of these Earth orbiters.

   The slideshow below shows the ISS at 1-minute intervals. Since this event is after sunset I have touched up the graphics – brightened and re-colored to make the scene more visible.

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Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

December Perigee Moon

24dec-perigee    Our Moon orbits around the Sun with the Earth and from our perspective on the Earth the Moon appears to circle around the Earth, however in reality the Moon orbits the Sun together with the Earth*.

   The 2.8 day old waxing crescent Moon reaches perigee this month on Wednesday December 24th at 16:42 UT (10 am CST). At that time the Moon will more or less be at a distance of 28.6 Earth diameters (364,797 km or 226,674 miles) from the Earth.

Click on graphic to see it full size.

Click on graphic to see it full size.

   Wednesday evening the waxing crescent Moon is near Mars and Comet Finlay (16P).

   
   
   *Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

   
   
   
[centup]
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

A Comet, the Moon, and Mars

       And no, this is not the first line in a joke sentence ending with “walk into a bar!”
       Seriously Comet Finlay (16/P), a regular visitor to the inner solar system has been reported to have significantly brightened from 11th magnitude to between 8th and 9th magnitude. According to reports the comet is typically at around 11th magnitude as it approaches perihelion, December 27th. So at 8th or 9th magnitude this puts the comet at a brightness within the reach of large aperture binoculars – at least 10×50 or larger. 25 mm with 8" DobsonianAnd certainly within the reach of telescopes.
       On the 24th the comet will be passing very close to Mars as we view them from Earth. This is a line of sight effect not one where the comet literally and physically comes close to Mars. This should be a fine pairing of celestial objects, especially when viewed through the eyepiece of a telescope as shown in this simulated view using a 25 mm eyepiece with an 8″ Dobsonian telescope.
    finlay-ani   Prior to the 24th you can follow the comet in real time on an interactive star map at the The Sky Live web site. This is a really useful web site for tracking more than just comets. The display may be set to a Planetarium, star chart, or a Live Position mode. With the Planetarium setting you can adjust the date and time and view the comet’s motion relative to the constellation and stars in the background.
    Click on graphic to see it full size.

    Click on graphic to see it full size.

       On December 24th, shortly after sunset local time, look for the thin waxing crescent Moon to be just off to the right from Mars and the comet.

       
       
       
    [centup]
    Caution: Objects viewed with an optical aid are further than they appear.
       Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.