New Jupiter Impact

Earlier today Australian astronomer Anthony Wesley reported a new impact site on Jupiter just as the sun was rising at his location. His image can be seen on his webpage. The time stamp on the image is Universal Time (UT). Renowned amateur observer Christopher Go has also captured a short video of the event which can be viewed on his site. There has not yet been a confirmation that there are leftover signs of the impact but observers are gearing up to try. To do this we need to know when the impact site is visible, according to Christopher Go the event occured at longitude 343 (System II). With this information we can calculate future observation opportunities:

6/4 5:04 15:00
6/5 0:56 10:52 20:47
6/6 6:43 16:39
6/7 2:35 12:30

All of the times in the table are transit times (UT). Practically the impact site is visible for a couple of hours on either side of the listed times. Unfortunately this does not work out well for viewing from my location in California - the time here is UT-7 hours so this gives the following local times for the transit:

6/3 10:04pm
6/4 8:00am 5:56pm
6/5 3:52am 1:47pm 11:43pm
6/6 9:39am 7:35pm
6/7 5:30am

The first opportunity at 10:04pm tonight (6/3) will not work because although the event is facing us Jupiter does not rise until 2 am and so is below the horizon! The following morning (6/4) the impact site will be visible from ~6am onwards and Jupiter will be high in the sky but the sun will have risen and be too bright. The first real chance is not until the morning of 6/5 from ~2am onwards as Jupiter is rising. This may be too long after the event for anything to continue to be visible.

Sky Fever

For various reasons it's been too long since I was out observing under a good dark sky. John Masefield's poem "Sea Fever" came to mind and so without further ado, my butchered version:

Sky Fever

I must go out to the dark sky, to the Milky Way in the sky,
And all I ask is a tall 'scope and a star to steer her by,
With observers lists and a red light and coffee by the pint,
For a long night at the eyepiece until the grey dawn breaking.

I must go out to the dark sky, for the call of the nebulae
Is a wild call and a clear call that may not be denied;
And all I ask is an inky night with the deep sky calling,
And the dark lanes and the bright stars, and the clusters gleaming.

I must go out to the dark sky, to the vagrant observers life,
To the snake's home and the coyote's home where the day sun's like an oven;
And all I ask is a merry yarn from a laughing fellow-rover,
And quiet sleep and a sweet dream when the long nights over.

With Apologies to John Masefield

Station Fire Moon

Over the last few days thousands of photos of the Station fire have been posted on the internet by many people. I have myself posted photos to Facebook of the fire that burned behind JPL on Friday night and some of these have been picked up and reposted elsewhere by others.

Astronomers have been hearing about the imminent danger that Mt. Wilson has been in and every night for the past few nights I have periodically stepped outside into my back yard and peered up to see if the antenna towers are still visible. Usually the peak has been swathed in clouds of smoke completely invisible from Pasadena but tonight when I stepped out they were still visible. The moon, shown in the photo I took this evening, was also up and is a bright orange, typically only seen during an eclipse and referred to as a blood moon by some cultures. These days we know that the orange colour we see tonight is due to light scattering from the large amounts of smoke and ash in the atmosphere that have been catching at our throats for the past few days but historically a blood moon was thought to foretell coming disaster and destruction.

Tonight is expected to be the night when the fire will make it's assault on the historic observatory on Mt. Wilson. The weather today has been much better for fighting the fire and the defences on Mt. Wilson have been buttressed as much as possible during the day. A good account of the measures taken can be found on the Los Angeles Time L.A. Now blog. However as I look up at the mountain and then at tonight's blood moon I can't help but shiver. On this night our hopes and prayers are with the fire fighters that have remained on the mountain overnight to defend our history.

Mars Hoax

It's the time of year when the 'Mars as big as the moon' hoax will be doing the rounds. The Old Town Sidewalk Astronomers have been combating this myth since 2005. The composite image above (click the image to enlarge it) has two images of Mars pasted to the left of the moon - the images were taken by myself and are at the same scale. The large image is the size Mars was during it's close approach to Earth in August 2003. The small image is the size Mars was in June/July of this year - a close approach occurs every 15-17 years. Mars is never any bigger than it is shown here ie it is never the size of the moon.

There is more information about Mars and the Mars hoax on the Old Town Astronomers website http://www.otastro.org/Mars2005/.

Jupiter Impact Update

The Old Town Sidewalk Astronomers had some excellent views of Jupiter Saturday night through my 8 in SCT and Jane's 7 in refractor. The impact site was clearly distinguishable and we watched it rotate across the disk. We finished the evening with a quick look at the other blue planet, Neptune.

I've had a number of requests about future times for viewing the impact site. Here are the best transit times from tonight onwards for Pacific Summer Time - remember the site is visible for about 1 1/2 hours either side of these times.

7/28/2009 1:33 AM
7/30/2009 3:11 AM and 11:03 PM
8/1/2009 4:49 AM
8/2/2009 0:40 AM
8/4/2009 2:18 AM and 10:10 PM
8/6/2009 3:56 AM and 11:48 PM

All times calculated using the excellent Astromist application for PDAs available from astromist.com.

Viewing Jupiter's Impact Site

So you want to see the impact site on Jupiter that was recently discovered by Australian amateur astronomer Anthony Wesley and are wondering how. You need a suitable telescope and to be looking at the correct time when the impact site is facing us.

Let's start with the when can I see it question:

This weekend there will be a couple of good opportunities to see the Jupiter impact site from the West coast with amateur telescopes. Jupiter will both be up and the impact site will be facing towards us.

The impact site is at longitude 216 deg (CMII longitude system) and the iceinspace site has conveniently calculated transit times for the next few days. A transit time is when the impact site is directly facing Earth. AS Jupiter takes ~10 hours to complete one rotation there are several times per day:

2009 Jul 24 05:16 ( 216°) 15:12 ( 216°)
2009 Jul 25 01:08 ( 216°) 11:03 ( 216°) 20:59 ( 216°)
2009 Jul 26 06:54 ( 216°) 16:50 ( 216°)
2009 Jul 27 02:45 ( 216°) 12:41 ( 216°) 22:37 ( 216°)
2009 Jul 28 08:32 ( 216°) 18:28 ( 216°)
2009 Jul 29 04:23 ( 216°) 14:19 ( 216°)
2009 Jul 30 00:15 ( 216°) 10:10 ( 216°) 20:06 ( 216°)
2009 Jul 31 06:01 ( 216°) 15:57 ( 216°)

These are UTC so have to be converted to Pacific Time by subtracting 7 hours. The next few opportunities together with the altitude of Jupiter (how high it is in the sky) are:

Friday night: the best time is 4:03AM Sat morning (altitude 29 deg)
Saturday night: the best time is 11:54 PM (altitude 37 deg)

Saturday night is the best option as the altitude is higher. Jupiter has a ~10 hour day so viewing is good ~1.5 hours either side of these times, provided Jupiter is above the horizon.

So now we know when to look but what do we need to look with?

The impact site on Jupiter is ~1/100th the diameter of Jupiter or <1 arcsec across. This is about 1/6000th the size of the moon.

To see this you need a telescope with a resolution of 1 arcsec or better and suitable atmospheric viewing conditions - the strong color contrast between the dark mark and the planet will help however. A telescope of 5 1/2 in (138 mm) diameter or larger has enough resolving power. You will also need to have enough magnification.

The rule of thumb is that a magnification of 50X per inch of aperture is typically the maximum possible. This means that for a 6 in diameter telescope the maximum usable magnification for a well collimated telescope under good atmospheric seeing conditions is ~300X. The eyepiece needed to get this magnification is found by dividing the telescope focal length by the magnification. Thus for my telescopes I get these results:

Takahashi FC76 refractor
Diameter: 76 mm
Focal Length: 600 mm
Resolution comment: too small to reoslve impact site
Max Magnification: ~150x
Eyepiece focal length for max.mag: 4 mm


Celestron C8 Schmidt Cassegrain
Diameter: 203 mm (8in)
Focal Length: 2032 mm
Resolution comment: Has sufficient resolution
Max Magnification: ~400X
Eyepiece focal length for max.mag: 5mm

Meade 12in Lightbridge
Diameter:304.8 mm (12 in)
Focal Length: 1524 mm
Resolution comment: Has sufficient resolution
Max Magnification: ~600x
Eyepiece focal length for max.mag: 2.5 mm

So I will be using my SCT to try to view (image actually) the impact site as the combination of aperture and focal length is best for this object.

Where to look for Jupiter?
If you need help finding Jupiter there are several resources:
Sky and Telescope interactive sky chart
Space.com monthly star chart


and many others online.

Good luck and Clear Skies.

The Twitter Phenomena

I've been using Twitter for a while and several things have converged to cause me to put my thoughts on Twitter in a blog. The first was a request from a professional society of which I am a member for thoughts on using Twitter, the second was a request from my employer on using Twitter in the workplace and the third was a comment by a reader on NPR to Scott Simon that Twitter was the CB radio of the time. I think this analogy is wrong but will discuss that later.

What is Twitter?
Twitter is an electronic messaging service that limits you to a message, called a tweet of 140 characters or less. When you send a tweet, it goes to anyone who has chosen to follow you and when anyone you have chosen to follow sends a tweet you receive it. In this way it is like CB radio in that tweets are broadcast however unlike CB Radio you only hear the people you have chosen to follow. You can send tweets directly to individual members, effectively making them private and there is a way to see all messages that mention your Twitter name. Twitter has a sister site, Twitpic, that enables tweeters to upload pictures for others to see. The key reason for the Twitter explosion is that clients exist for most cell/mobile phones. Twitter can be thought of as a variation of Instant Messaging &/or an RSS agregator for cell phones.

How do I use it?
For Twitter I have a split personality. One personality is my professional personality and the other is my personal life.
I work for JPL which requires that all public communication be approved before release. This means that I almost never tweet about my work except in the most general sense or when doing so in an official capacity as happened at our recent open house. However I use Twitter in place of an RSS agregator to get news from organizations of relevance to my professional activities. Such organizations include the House Science and Technology Committee, The National Academies Press, my employer's official tweets (multiple tweeters) and professional societies such as the Optical Society of America.
In my personal life I follow a number of friends and tend to tweet about items of interest to me ie mostly my girls, astronomy, archery, photography and nature. Most of the people I know socially are not on Twitter at this time.

Privacy issues
I'm not in the mass-media business, my friends and I use Twitter as a convenient mobile messaging service and so I have developed a few strategies to control who can read my tweets.
The most important tool on Twitter is the ability to block people so that even if they want to follow you they can not see your tweets. I always look at the profile of a new follower. Unfortunately, given the recent hype about Twitter, some are clearly just trying to promote themselves or dodgy schemes or look to be collecting information - these I immediately block from following me. I never start following someone who starts following me unless I know them personally. I give people I don't know who start following me a grace period to see if their tweets are of interest, if they are I will eventually follow them. This provides me with considerable control over who reads my tweets. It should be noted that anyone can read my public tweets by looking at my page on Twitter I therefore try to be careful as to how much personal information I divulge.
Twitter has a feature called "Trending Topics" and this used to contain interesting items when I first joined but with the explosion of membership it only shows lowest common denominator topics which are almost never of interest to me. It seems that whenever you put the mass into media it results in the same types of tabloid topics independent of the medium amd this presumably is what the NPR listener was referring to when he made the CB radio comparison. However the ability to control which tweets you see and who can see your tweets puts a simple filtering screen on this noise and clutter so you only see what interests you. Incidentally whoever comes up with a good algorithm for capturing the definition of "interesting" on a personal level and then implements it successfully in a general search engine can count me in as a user of their services.

The Future?
The popularity of Twitter is based on its ready availability on cell phones so that it is effectively everywhere - as an example I can now tweet over a 3G connection from the middle of the Mojave desert several miles from the nearest paved road at one of my favorite dark sky astronomy spots. The 140 character limitation is a key to Twitters success in that by forcing short communications it encourages frequent communication - look at the prior posts in this blog to see how hard I find it to get free time to type my thoughts these days :)
As cell phone data connections and applications get better I'm sure something better will come along but for now Twitter works for mobile, everywhere communication.