Observations and Sketches of the Shrinking of GRS
Posted 11 March 2013 - 11:18 AM
Since I posted this yesterday I changed my web page so all of the sketches can be seen simply by scrolling up and down. This makes it easier to compare how the GRS has changed over time:
I was watching a TV program recently about Jupiter and it mentioned that Jupiter's Great Red Spot (GRS) is shrinking in length. I had heard this before but it got me wondering if I had seen and recorded this phenomena during my telescopic observations of the planet since 1973.
In looking back at one of my earliest observations and sketches of Jupiter in 1973 with a 60mm refractor the GRS looked elongated to me:
The same held true with Jupiter in 1974 when I was using a 4.25" reflector:
The GRS had faded to a dim gray color in 1976 but the Red Spot Hollow was noticeably elongated when I observed it with a 6" reflector in early 1977:
During my observations of Jupiter in the 1980's the GRS had a more oval shape to it:
My more recent sketches of Jupiter show the same thing:
So it seems likely I was recording the decreasing length of the GRS from 1973 until today. This is because leaving aside differences in the telescopes and magnifications employed over the years they all show the same trend in the data.
To verify this I went I went to the Sky and Telescope website and came across a couple of articles that discussed how the GRS has been shrinking in length since the late 1800's. In the late 1800's it was almost 35 degrees wide. However by the time Voyager 1 and 2 visited Jupiter in 1979 it had shrank to 21 degrees. The height of the GRS has remained approximately the same.
It confirmed also that between 1975 and 2010 the GRS has been shrinking in length from around 24 degrees to around 15 degrees. So my observations were accurate.
It was a good thing I made sketches over the years as without them I may not have realized how much the GRS has changed over time if I had just taken notes.
Posted 11 March 2013 - 01:24 PM
Posted 11 March 2013 - 02:37 PM
Posted 11 March 2013 - 07:54 PM
Posted 12 March 2013 - 08:42 AM
Thanks for the very kind words. After watching the TV show I started going back through my old astronomy log books and was surprised how much the GRS has shrunk over time.
I had no idea when I first started sketching at the eyepiece in 1973 that someday the sketches could show pronounced changes to the GRS.
Posted 12 March 2013 - 08:54 AM
Thanks for the very kind words.
Thanks for your suggestion about putting the drawings side by side. I changed my web page so all of the sketches can be seen simply by scrolling up and down. This makes it easier to compare how the GRS has changed over time:
Posted 12 March 2013 - 08:59 AM
Thanks for the very kind words. I changed my web page so all of the sketches can be seen simply by scrolling up and down. This makes it easier to compare how the GRS has changed over time.
Posted 13 March 2013 - 09:10 PM
That is an interesting change in the shape and size of the GRS. I have some sketches that go way back, I should pull them out and have a look.
Thanks for posting and very interesting.
Posted 20 March 2013 - 04:09 PM
Thanks. I would be interested in seeing your sketches.
Posted 21 March 2013 - 12:31 AM
Here is one from 1980 and I did draw the GRS elongated. I would not consider this good evidence since I did not sketch Jupiter with reliability before about 7 years ago.
Posted 13 April 2013 - 12:15 PM
I recently came across a sketch of Jupiter and the GRS made by Étienne Léopold Trouvelot of Jupiter on November 1, 1880 using the U.S. Naval Observatory 26" refractor:
I noticed that even accounting the larger aperture he was using compared to mine the length GRS back then was significantly longer than what I recorded:
Posted 13 April 2013 - 09:55 PM
The drawings by Trouvelot are fine ones. He was a gifted astronomical artist of the late 19th century. I am sure his drawing are faithfully accurate.
Posted 14 April 2013 - 04:03 PM
Thanks, I added a link that shows some of his other astronomical sketches that include lunar ones as well.
Posted 15 April 2013 - 10:55 PM
I am familiar with some of these but not all of them. The one of Mare Humorum is especially good.
Here is a solar sketch he did that I posted on ASOD a while back (April 29,2007). http://www.asod.info/?p=125
His planet sketches and that one of Jupiter with the great red spot are very special.
Posted 28 April 2013 - 02:05 PM
Thanks for the link, the sketch shows a lot of fine detail.
With regards to his comet sketch I had read that sometimes observers back then would make a sketch of a comet through a telescope and then add the observatory in the foreground.
So the resulting sketch is not what they see with the unaided eye.
Posted 29 April 2013 - 01:27 PM
Just came across your site. Lots of great information there. This is some of the info I have been looking for. I just started sketching Jupiter in the past month and I am trying to learn more about the planet. Nice Work. I will be spending more time reading on your site.
Posted 01 May 2013 - 11:39 AM
Thanks for the kind words about my website, I try to add new material as time permits.
There are some of my Jupiter sketches on the Introduction to Planetary Sketching page:
Also on the Jupiter Nomenclature page:
And on the Jupiter Sketches and Observations page:
I observed Jupiter last night but the seeing wasn't very good.
If I can answer any questions for you let me know.
Posted 01 May 2013 - 12:00 PM
I am enjoying reading your posts. I also tried at Jupiter last night and had little luck. Very Windy here.