Thursday, 21 April 2016

Transit of Mercury 2016 May 9

On the 9th of May (this year) there will be a rather rare event. The planet Mercury will transit the face of the Sun. This does not happen every time Mercury passes between the Earth and Sun. The distances and sizes are very large.

Mercury, even when closest to Earth, is a mere 11 arc seconds in size. For comparison, the Sun is half a degree (30 minutes or 1800 seconds) in size. In addition, the inclination of Mercury's orbit is 7 degrees meaning that it misses the solar disk by up to 14 times the size of the Sun. (More Mercury facts available at:

After this transit of Mercuy, the next one will be in 2019 then we wait until 2032. There are only 14 transits of Mercury this century. Here is a list of Mercury transits.

Okay, so a transit of Mercury is rare. But is it spectacular? Well, to be honest, no it isn't. You need a telescope to see it. And at that, a safe solar telescope with either a good solar filter or set up for projection. The picture below is one taken through a small telescope. Mercury is the little dot (shadow) on the edge of the Sun on the bottom right of image.

Mercury Transit - Questar prime focus

Thus I cannot say it is worth getting too worked up about unless, like me, you marvel at the ability of science to predict such things and our ability to see it. These are things that only came about in the past couple centuries. People have not been watching Mercury transit the Sun for many generations and you could end up being the first ever in your family to have seen one. If you have the right gear, then by all means get set up for it (if clear and you are on the right side of the Earth - check the transit visibility map here) and share the experience with others. For real geeks, here is an online Mercury transit calculator with great details from your (or a specific) location.

For us, the transit will be visible in the morning hours which works out best. We have the clearest sky in the morning and should be able to see the entire transit. The problem will be clouds over the hills to the East of us, if any.

Sunday, 17 April 2016

New Website of Note, EclipseWise

There is a great new website containing eclipse summary information for centuries of eclipses by retired NASA eclipse expert Fred Espenak named EclipseWise. Click here to visit.

Fred Espenak used to maintain the primary and very popular website for NASA's eclipse prediction service and now has taken it private, so to speak. Books and more are for sale there to help support his effort (passion).

Just this past week I was updating some of the Javascript utilities for his webpage. A new utility will be presented soon to list cities able to view an eclipse event. The cities are presented in geographic groups and you can add you own city to the list for display (private entries are not saved, at this time).

For those that do not know Fred Espenak, he is a long time guru in the eclipse chasing game. He has seen well over an hour of totality. His presentations about eclipses and his experiences are in high demand and well attended. And he has written some excellent books about eclipses and eclipse chasing that you can find at his web site. One of his earliest publications was a detailed set of tables and maps for eclipses up to the year 2035 that has served as my travel guide since the late 1970s. More recently he produced a canon of eclipses spanning a millennium. That tradition continues although now he has teamed up with others to create awesome books for each major eclipse. Click here to see the 2017 eclipse book, highly recommended!

Sunday, 10 April 2016

More web page work, plans for 2017

I added a link from the summary page for upcoming eclipses to the larger map format instead of just the local circumstances. The larger map provides an option for locating an eclipse position by name in addition to coordinates or picking it on the Google Map.

2017 Eclipse Track - bigger map
Another change to the eclipse-chasers web site is the color of the timing for totality duration in the eclipse chaser summary. The color is changed for each five minutes of totality duration seen. At one minute of time the colors go bold as well. If you don't like the color scheme, please let me know. I selected the colors kind of at random and based on how well they showed up against a white screen. Your input is always appreciated.

***2017 Update***
We have been researching options for the 2017 eclipse, as I am sure many others are doing as well. There are numerous resources on the Internet and it can be quite overwhelming to read all the ideas and plans people have been making in anticipation of the eclipse. Although I do find it even more amazing that a lot of people still do not know about the eclipse! Even those living right in the central path of the shadow.

Last week I thought we had a solution in Casper Wyoming but it turned out the hotel had the wrong year for the reservation. We cancelled that opportunity and began an earnest search for another option. Some of the hotels indicated they will not take reservations until one year in advance. I suppose they know they will get a flood of phone calls.

So where are we going? That is a good question. We are still giving serious thought to Wyoming if a place can be found to sleep the night before on the central path. Our second choices vary quite a bit from Nebraska all the way to South Carolina. The reasons vary just as much from good transportation options and accommodations to friends and family located near or in the main shadow path. The thought process continues forward but so far there is nothing concrete in the planning.