Thursday, August 21, 2008

light, shadow, clouds (Toronto)

Tried to spot a moon shadow on Jupiter this evening. No joy.


I was up and running, in front of the house, at 9:00 PM. Had a few visitors early on. Katie was a little bashful but her Mom encouraged her to seize the scientific opportunity. We elicited a "Wow!" Joy. Jupiter looked good. The cloud bands were easily sighted. The four moons, and a couple of field stars, put on a good show. Unfortunately, all the outside school lights were on. Huh. It's still summer vacation!

I sketched the view while using the 18mm eyepiece although I got the scale wrong. Io was about 1 planet-width (pw) away at the time.

Image edited in Fireworks. Colours reversed. View not corrected; shown as sketched, mirror-reversed. Bottom-right arrow indicates direction of drift.

The seeing was not great. Was it the atmosphere? Or my telescope tube still settling? At 111x power, the view was not satisfying. It was colourful, would go in and out of focus. Nothing like the last sidewalk viewing, about a month ago.

9:38 PM. Over the next minute or so, Io lined up below Callisto, forming a line perpendicular to their orbital plane. Io is moving fast. It is harder to detect movement in Callisto.

There is almost a perfect equilateral triangle with the outer moons and a field star (HR7128) south of Jupiter.

The shadow position will be interesting. I don't know where to expect it. I assume it will be coming from across the opposite side. It always reminds me of the scale of the solar system, how far we are far the Sun... But isn't Jupiter near its opposition? So then the shadow should be close, no? But Callisto is almost 1 pw away. Hmmm. I'm a little confused.

All the free astronomy software that I use does not show or simulate Jovian shadows...

Here comes the Great Red Spot! There have only been a couple of moments of excellent seeing. I can see the GRS on the opposite side of Io and Callisto.

10:01 PM, 66%, 20.1°C. The seeing is poor. More shimmering, the airy disk around the moons is jostling and wavering. I cannot see any shadow on Jupiter's disk. Io is a ½ pw away now.

The view is getting worse! The contrast is dropping! What the hell?

I packed up.

10:23, 67%, 20.2°. From the backyard, I can see clouds! High, thin clouds. Everywhere! Drag.


Eyepieces, the 36 and 26, need cleaning again.


The base was oriented better this time. I used my compass to find true north. Surprised by the angle, compared to the sidewalk. It looks like the house itself is almost exactly north-south. I could use it as a guide in the future.


Stupid search lights south of here... On the lakeshore?

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