Telescope Reviews: Shadow transit of Io on Jupiter August 20th

Around about a quarter past eleven in the pm, I opened my front door to see if Jupiter or anything was visible. Nice surprise, the sky was clear. Debated with myself if I should carry out the heavy LX90 or take a peak with my 8 inch DOB. Hmmmm …………. What to do? Figured I would check the seeing with the dob, it is just easier to move out of my study.

Oh brill !!! , some banding, enough to observe, longer seconds of clarity than I had noticed on previous occasions. A dark dot was very obvious in the equatorial region, not being a planetary observer the names of the banding layers do not freely come to mind. This was a sketching opportunity I never had before. Hmmmmmmmmmmm……………….. What to do? Will I set up the LX 90 as I was curious what it would offer me or stick to the scope I had in the moment?

Checked out observing software to see which Jovian moon it was.
Thinking that those pesky clouds were most likely going to descend any moment I opted to sketch what I had in view and not waste time setting up another scope. Maybe I could get a comparison sketch later if the weather held. My sketch pad had three 80 mm circles from a moon drawing project that had not see the dark of night for months due to cloud. That will have to do I reckoned, need to get something on paper fast.

22:40 UT Jupiter 19 degrees
200 mm / 8mm TVP eyepiece / FL 1200 mm /150 X to my eye /no filters / same info for all sketches.

In my view Jupiter was only approx 10 mm in diameter, not much point in drawing something so
small in the same scale as I am viewing it, up scaling is the only way to go about this.
So I sketched the planet to fill the full 80 mm circles (even though Jupiter is not a circle) and observed as much detail as I could.
The seeing was about 2/3 and up and down on either side of 3 for brief seconds and milliseconds
during the course of the first sketch.

23:20 UT Jupiter 20 degrees, getting windy, haze from time to time.
WOW !!! The Jovian satellite Io was galloping along, in its apparent motion east to west.
The shadow of the satellite was very clearly round and dark against the paler bright zone.
The north and south polar areas of the planet offered very little detail to me.
The bands that appeared white on the planet were very contrasting with the other darker bands.
Within the darker bands I noticed some variations in tone and with the constantly changing seeing I also noticed variations in structure as well, but not enough to sketch detail as I would have liked. The scope shaking from time to time in the wind did nothing to help.

23:40 UT Jupiter 21 degrees the shadow is moving closer toward the preceding limb of the giant planet. A short while later I began to notice that Jupiter seemed to be developing a dint in its limb visually speaking. I did not take note of that time exactly as I did not want to take my eye of the ball, literally.

(Mental note to self, record fast moving events by voice in the phone to have a date and time record, or have giant illuminous watch within eye flick distance, or both)

23:45 UT give or take a few minutes I observed the shadow changing shape, becoming crescent shaped as it grew closer and closer to the limb. I realized that the shadow was in effect showing me the limb the total disc of Io !!! Planetary observers correct me if I am wrong on this observation.

Jupiter had developed a pimple on its otherwise unblemished curving limb by 23:45 UT
At 23:54 UT Io had cleared the Jovian disc and was clearly visible all by itself in space.

My last observation was at 00:01 UT as Io had moved away by at least it own diameter again from the preceding planetary limb. Hazy and more windy then, end of story.

Dee