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Welcome! to CACAO!

CACAO is supporting the Comet Wirtanen Observing Campaign. We've learned alot from supporting:

Show me the pics!

A summary of submitted comet and asteroid images/observations is posted in the Gallery! However, if you want just the CCD images of Wirtanen, then here's the AOP/CACAO Gallery: 46P/Wirtanen list of images.

Where to start...

Image/File Submissions

We are now accepting observations (images, sketches, lightcurves,...) of

  • currently visible comets
  • asteroid Ceres
  • asteroid Vesta

  • any of our past targets
  • UMD asteroids

Please visit the LogBook to find out how to submit your observations.

Don't worry, you won't need to know much about astronomy, comets or asteroids. That's what this site is about!

So, let's get started...

  • If you don't know what an asteroid or comet is or how to find things in the night sky, you'll want to start with the Beginner's Guide.
  • Take the next step and learn about coordinates, magnitudes, and some simple projects in the Intermediate Guide.
  • If you just want to submit your latest observation, go to the Log Book.


Comet Wirtanen Observing Campaign Update

(6 Dec 2018) We are about 10 days from close approach of Wirtanen and I have receieved a number of reports of naked-eye and binocular observations. However, the lightcurve has started to deviate from the Yoshida prediction, suggesting that it might level out around mag 5 (though there is a lot of scatter in the observations).
As the comet has gotten closer, observations are also ramping up. Currently we have word of at least 41 (!) different observing programs from all over the world that are planned in the weeks around close approach. Give the range of wavelength, instrumentation and temporal coverage, this will provide a wealth of data for studying Wirtanen in detail.
CN observations obtained at the Discovery Channel Telescope continue to show rotating jets.

    Dave Schleicher reported on the production rates he measured Dec 3.
  • 46P/Wirtanen (r=1.06 AU; Delta=0.11 AU, 12 sets of data):
  • log Q (OH; Haser) = 27.78 molecules/s
  • log Q (H2O; vectorial) = 27.90
  • log Q(CN) = 25.07
  • log Afrho (5260A) = 1.77 cm
  • Notes: We observe small temporal changes in Q, presumably due to rotation. More surprisingly, there is little variation (~15%) of Afrho with aperture size using aperture diameters ranging from 24 arcsec to 204 arc sec; this is much smaller than usually seen in most comets.

The water production suggests that Wirtanen is behaving as expected compared to previous apparitions.

NASA is also producing a ScienceCast video about the comet. It should be finished in the next few days. I'll send out a notification when it is released.

As always, we'd like to hear from you about results as you observe the comet {Use the Logbook link in the left menu!}.

For more information about the comet, visit the campaign website at
Tony Farnham
for the Wirtanen Campaign

Updated: 10-Dec-2018