Sept 20-21, 2022
While prepping for my HAL talk last month I stumbled across the fact that the Astronomical League has a Jupiter Observing program among its offerings. It's a program whose objectives I've certainly met over the years, but thought it would be fun to officially claim the prize.
One task is to collect a series of observations on the 4 bright Galilean moons and interpret your data to characterize the moons and their orbits. You need a couple of sessions spanning over two hours, and this evening's clear skies (and an added bonus of a Ganymede transit) was a nice opportunity to meet some of the program's requirements. I decided to use the 80mm Vixen refractor since it is easier to set up and more than adequate for recording the bright moons.
By 10:30 I had Jupiter centered in the eyepiece. Ganymede's large and stark shadow is not hard at all to pick up on, even in this small aperture. While I could have simply sketch the moon positions, I opted for a set of video images at 30 minute intervals as a better approach.
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| Galilean Moons, with Ganymede in Transit |
When I finished the first capture I did a quick processing to see what I had. I was actually a little surprised at the detail on the planet using such a small aperture. It led me to wonder just how much detail could I get using the Vixen if I tried?
Since I needed to wait a half hour to make my next capture I decided to explore the question. I popped in the Meade 2x short Barlow and brought the Region of Interest (ROI) as tight as I could. This smaller capture area allowed the frames-per-second rate to go from 96 to 286, increasing the chances of leveraging those microseconds of steady seeing into a nice photo.
Next day I set to work running the video capture through my workflow - PIPP, Autostakkert3!, and Registax6 to produce a final image. Although the details are puny compared to what the 10" Cyrus reflector produces, they are pretty amazing given the aperture. Not only do we get the major bands, but features such as festoons in the NEB, Ganymede's disk as it begins to egress, and even Oval BA can be clearly identified in the tiny image.
Would one suggest an 80mm refractor as a good instrument for planetary exploration? Not really - but it clearly has a lot more to offer compared to what you'll see behind the eyepiece when you team it up with computer assisted planetary imaging. Visually it takes a little effort for me to discern Oval BA using the 10" with a suitable filter. Snaring it in a capture using a telescope with 3 inches of aperture is really quite a testimony to the high-contrast quality that refractors offer as well as the power of using the lucky imaging technique. If you use a similar scope as your main tool for exploring the night sky you might consider adding on a planetary video camera and discover for yourself the enjoyment of capturing features that you'll likely never see visually.
