Steve’s Virtual Planet

Great view of Jupiter’s GRS .. Finally!!

This last few months has brought me a lot of joy showing off our largest planet to audiences small and large at Fernbank Observatory. However, the seeing conditions have been anything but ‘astronomical’ all the way through the late fall. In a couple my posts back in October and November, I had described my adventures looking for the GRS. Well, I had a glimpse or two but nothing too … spectacular.

BUT … I finally had a little more luck on December 2nd. I got there early enough to fire up the 36 inch Cassegrain in the done and the 11 SCT outside.  My session went from about 18:25 to 19:30, with the GRS transitting about  19:00. Not only that but I had the shadow of Io out ahead of the GRS as a kind of marker. I kept the Sky View Cafe app running so I could double check my location as the time progressed.

So, after walking back and forth between the 36 inside and the 11 inch outside, I was getting a glimpse of the GRS. It was there but just not very well defined, more of a hint than a real shape. But soon, my persistence started to pay off. For about 15 minutes, the seeing settled down and I was able to get a good view and good definition with both scopes. The oval of the GRS became more defined and I most certainly caught some level of dark orange through the 36 inch. Perhaps I was even picking up a little color in the 11 inch however I was more excited just to see it clearly using the Sky Glow filter, diminished as it was.

The 36 inch was set at 120 power and the SCT 11 was using a 32 mm Plossl giving it a magnification of 87 power. So, the comparison was useful given the seeing conditions overall for the evening. In any case, after attempting to get something (anything!) like a decent view of the spot, those few minutes were memorable.  And it those memories that stargazers long for!

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Galilean Moon Orbital Periods

A common question comes up now and then about the period of the moon’s orbits. I’ve been sort of giving round numbers until recently but I thought I’d better look up the periods to get an exact number. So, off to Wikipedia for this page on Jupiter’s Moons and a chart of all of them! The values have nine significant digits so I thought I’d round them a little so I could remember them more easily. Here they are in the order of decreasing orbital size.

Callisto, the second largest moon, takes a little over 16.5 days

Ganymede, the largest and most massive moon, takes a little over 8 days

Europa, is the least massive of the four and takes about 3 days and 13 hours (so, make that about 3.5 days)

Io, almost twice as massive as Europa, takes about 1 day and 18.5 hours (this would be 1.75 days)

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SVC Tip #2 - Tracking Jupiter moon occulations

As already mentioned on the SVC Tip #1, one of my favorite internet tools is Sky View Cafe.  This tool is very useful for determining the location and position of the moons of Jupiter.

I’ve used the special tab called “Moon/GRS” a number of times in the last few months to document the Galilean moons and to plan my viewing. For my outreach work, I also produce a printout with the orientation of the view set to match the scope being used.

For the evening of November 8, 2010, I had noticed that Europa and Io were going to be ducking out of sight right before the beginning of my planned GRS observation. By “walking” the time setting back and forth, I could determine to the minute when the moons would slide behind Jupiter. So, I made sure I was completely setup and alligned on the planet about 10 minutes before hand. And sure enough, right on cue, Europa slid out of view at 18:19, followed by Io a while later at 18:51. You can see it work for real just by setting the clock back to Nov 8, 2010, 18:00 hours and slowly running the clock forward.

Another useful thing you can do with SVC is get a table of the exact values for these events. Use the “Tables” tab and select “Galilean Moons/GRS” from the first button. Leave the next button set for “One Day”, then click the right hand button “Generate Table”. The example text is shown below.

Galilean moon events (US/Eastern time zone)
GRS transits based on tabular GRS longitudes from 1969-04-01 to 2010-10-01
Interpolated GRS longitude at 2010-11-08 18:00 is 157.5°

2010-11-08 18:19   II. Oc.D.
18:51    I. Oc.D.
19:08  GRS transit
22:09    I. Ec.R.
23:19   II. Ec.R.
2010-11-09 05:03  GRS transit
14:59  GRS transit
16:04    I. Tr.I.
17:10    I. Sh.I.

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Filters for viewing Jupiter’s GRS

Jupiter has been a lot of fun for me this apparition. It’s been higher in the sky than last time and much easier to see right from my driveway through a very convenient gap in the trees. I’ve been able use one of three scopes at home (3 inch refractor, 5 inch Mak & 6 inch Sch-New) and two scopes at Fernbank Science Center (11 inch SCT and the 36 inch Cassegrain). But despite all that aperture and all that glass, the brightness of the planet has made the Great Red Spot (GRS) difficult to see.

Recently, I asked several of my fellow star gazers about using filters for Jupiter’s GRS. I had tried several suggestions from the Lumicon filter guide and another related article on SciAstro. However, this year the GRS has not been very prominent so even the “standard” selections for these filters wasn’t much help. One of my colleagues suggested using a SkyGlo filter, which I had actually seen a reference to in an article somewhere (just do a Google search on Jupiter Sky Glow Filter). It was a DUH moment but I remembered immediately. So, I would be using that filter on the next opportunity and comparing to the earlier attempt. All the trials below were using a 5 inch Maksutov in my suburban driveway.

GRS viewed with yellow #12 and yellow-green #11 filters is not a big difference. I tried these on Halloween 2010 when the seeing wasn’t all that great anyhow, so perhaps the test was not conclusive.

I’ve seen recommendations for the Blue #80A and Dark Blue #38A in several places, including the link below.  I think my 5 inch Mak is too small to use these effectively since it darkens the image quite a lot. So, I tried these the next time I had a good chance to catch the GRS, on Nov 8, 2010.

Using the Orion Sky Glow filter gets much better results, although on this occasion, it was still quite a challenge. The seeing has not been real good this season here in the big city. So, one has to work really hard to get the desired view. So, I am hoping for perhaps one more chance to get the GRS from my driveway early enough in the evening before the “giant pine tree mask” gets in my way to south!

Here is some more information from someone who should know. Damian Peach gives these recommendations on his web site :

I highly recommend the use of coloured filters for observing Jupiter. These can be easily obtained from many suppliers. For Jupiter the most useful filters for the visual observer are Red and Blue. Smaller scopes (less than 20cm aperture) may prefer Orange or Light Blue. Filters worth considering are Wratten #25 (Red), #21 (Orange), #38A (Dark Blue) and #80A (Light Blue.)

See my Sky View Tip #1 for more on how I tracked the GRS on Halloween, 2010. Check some of my other posts with further tips on using using Sky View Cafe.

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Viewing the Lunar Straight Wall (archived)

I just happened to notice an event on my 2010 observing calendar a few months ago, something about a “Lunar Straight Wall”. Hmm, I had not heard of that one before, probably because I had not paid too much attention to the finer details of our moon. But since this event corresponded with a normal Thursday open house down at Fernbank Science Center, I decided to use the 36 inch scope and try to find this wall.

Well, good grief, I found it alright!! Can’t miss this thing if you’re looking anywhere near Mare Nubium. It’s quite prominent as an almost straight line. However, it turns out that it is easy to see ONLY on the first day past 1st Quarter, about 8 to 8.5 days phase. That’s why its in the calendar every month. I just had not noticed before. But is one of the best examples of a linear fault, also called a rille. The reason why it’s only listed around this time is because of the shadow that it casts when struck with the sunlight at just the correct angle. For the rest of the month, it’s virtually hidden because it no longer creates a good shadow.

I have found several references online, like the one below from Wikipedia. The link has an image of the feature. The Lunar Straight Wall is also known by it’s Latin name Rupes Recta.

Wikipedia - Straight Wall
“Rupes Recta is a linear fault, or rille, on the Moon, in the southeastern part of the Mare Nubium at 22°06′S 7°48′W / 22.1°S 7.8°W / -22.1; -7.8. The name is Latin for “Straight Fault”, although it is more commonly called the Straight Wall. This is the most well-known escarpment on the Moon, and is a popular target for amateur astronomers.

When the sun illuminates the feature at an oblique angle at about day 8 of the Moon’s orbit, the Rupes Recta casts a wide shadow that gives it the appearance of a steep cliff. The fault has a length of 110 km, a typical width of 2–3 km, and a height of 240–300 m. Thus although it appears to be a vertical cliff in the lunar surface, in actuality the grade of the slope is relatively shallow.”

I’ve now had two convenient views, one on April 22, 2010 and another on October 15, 2010. The first view was a novelty and I was able to show the feature to a number of visitors that came to the observatory that night. On the second occasion, I set up a Meade DSI I camera on a separate refractor to attempt to get some images. I just kept snapping images in the hope of getting the escarpment to slowly come into view as the moon’s terminator advanced. But the images did not show any of the rille as it must have been a little past the optimum time. I could see it fairly well in the 36 inch at 125 power but the contrast was not good enough to also see it in the images.

In any case, I hope to try again when I can next set up my camera on one of my scopes. If I can spend more time during the course of a longer night’s viewing, my hope is to get a good sequence of images to catch the wall at just the right point. More on that in a future post, hopefully.

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Visit to Lowell Observatory

My wife and brother-in-law and I spent time in Arizona in May of 2009, mainly to see the Grand Canyon. We stayed in Flagstaff for most of that time since it was also near Sedona, Meteor Crater and some other “Grand” sites around northern Arizona. As wonderful as the five days around the Canyon was though, the trip to the Lowell Observatory in Flagstaff was a special treat.

This was my first trip to a truly historic observatory, although there are several on my list for the future (Yerkes, Palomar, etc). The site is very accessible, just up on a ridge overlooking the town of Flagstaff, barely a 10 minute drive from the downtown strip and Route 66. Since the city has long been aware of the significance of light pollution, the light ordinance there makes for a very decent sky view.

Entering the facility up on Mars Hill and getting into the visitor center felt like walking on hallowed ground. Once getting tickets, you are shown a documentary film about the site, its history and the discoveries made there, especially by Percival Lowell and Clyde Tombaugh. There is a small museum on the site where many of the instruments are on display, including the blinker used by Tombaugh to discover Pluto.

Of course, when you’re at an observatory you want to observe through the telescope. And it was a beautiful clear night with very good seeing conditions. I stepped into the observatory and was greeted by Brian Skiff, one of the research assistants who has been there since 1977. He checked the sighting on Alvin Clark 24 inch refractor since the scope clock drive was out of action.  And I stepped up to the most gorgeous view of Saturn I’ve ever had. It was still twilight not too long after sunset and the planet popped right out at me with four of it’s moons all off to one side - Titan, Rhea, Tethys and Dione!! I guess the view was something 120x to 150x, but it was just wonderful.

Brian and I spoke for a short time while I just stood there like a kid at Christmas, staring up through the dome. Soon after my first look I waited and got another peek before the crowd arrived. This time I got my first view of Enceladus out on the left side just past the ring system (Mimas might have also been visible that night if it weren’t for it’s close proximity to the rings).

In any case, the view was still amazing and entire experience breath taking. When you visit all the way from Georgia, There is nothing quite like those clear Arizona skies!

Here are several photos from Lowell Observatory.

Steve speaking with Brian Skiff at the Alvin Clark 24 inch refractor.

Looking skyward with the Alvin Clark 24 inch

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Galileo’s Universe at Stone Mountain M.S.

Steve gave another presentation in the Galileo’s Universe series on Sep 24. He visited the 6th grade science classes at Stone Mountain Middle School. Science teacher Ms. Madeline Hill was the host and the event was held in the school’s media center.

The students had already been studying Galileo and other scientists of the Renaissance and this presentation was a way of bringing to them further insight to the importance of their work, 400 years ago.

As Steve explained to the students and teachers:

“’Galileo’s Universe’ is not just about Galileo himself, but it’s a story of how modern astronomy got started. More importantly, it’s also the story of how modern science began. That’s why this subject is such an important part of the whole history of science.”

Steve’s opening remarks:

Question time:

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Globe at Night Update #1

I’ve been accumulating GaN data for the past week or so. I have been relaying on the more qualitative technique published by the GaN web site. This uses the belt of Orion and the remaining stars of the constellation as magnitude indicators. I now have some data from around the Atlanta area, both at home in Chamblee and also at Fernbank Science Center.

Clouds and weather have impacted at least 5 days and the seeing has been fair to poor most nights. But I still get mag 3 or 4 in the city area. More to come in the coming week. I plan to do another round in the second half of March.

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Galileo’s Universe Part 2 - Planetarium Program at Fernbank

“Galileo’s Universe - The Birth of the Modern World” will premier at Fernbank Science Center this Fall.

“Galileo pondered the features of the moon, the phases of Venus, the moons of Jupiter, and much more. We will take an in-depth look at Galileo’s observations and accomplishments. How did Galileo’s work complement and further the work of Copenicus, Kepler, Brahe, and Newton?”

This planetarium program will be of the to commemoration of the International Year of Astronomy at Fernbank. The currently planed dates are from November 5th to November 21st.

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Galileo’s Universe - Presentation at Agnes Scott College

Steve will again present his talk entitled “Galileo’s Universe” at Agnes Scott College as part of the Open House Lecture Series. The talk will be held at the Agnes Scott Observatory at 8:00 PM on Friday, November 13, 2009.

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