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The upcoming Mercury Transit 05/09

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cpmalo87's picture
The upcoming Mercury Transit 05/09

I am planning to record contact times during the upcoming transit.  I wonder if any vsoers are making similar plans?  It might be interesting to compare transit durations between observers at very different lattitudes (N. vs. S. America?) in the hopes of computing a reasonably good parallax If nothing else, it may have educational value.  I believe that some investigators collect amateur data like this from widely spaced observers, but can't remember details.  Any thoughts/interest?

DFR's picture
That's a great idea. I don't

That's a great idea. I don't know if the precision of the observations would allow precise computations of parallax or anything else, but it would be a fun experiment to try. I'm in Ontario, Canada where the entire transit will occur when the sun is above the horizon. If enough others commit from across a wide enough baseline, then we could at least see what we could do with the observations.

(I had intended to research the subject before posting here, primarily in ALPO Mercury Section, but I'm about to depart on a road trip and so won't be able to look into details until next week. Maybe other interested observers have experience/information/time to research the situation.)

The entire transit will be visible from eastern North America, most of South America, and western Europe and transit is already in progress at sunrise for observers in western North America.


Roger Pieri
From Western Europe

It should be entirely visible from here, Burgondy, France, if weather permits. We are several from the SAB planning to observe it. I will be pleased to participate to such tentative. Such observation would need an accurate timing of the images as it is usual for phemus... occultations from asteroide or so. Anyhow it will be very depending the weather, very bad for months up to now !

Clear Skies !


HRHA's picture
The upcoming Mercury Transit 05/09


Would anyone have a tutorial that could be used for recording their observations on this Mercury transit?  Or, perhaps a an easy to follow tutorial on solar observing in general?  



sfy's picture
The upcoming Mercury Transit 05/09

Hello Rodney,

there is some information on observing the transit on the BAA web site:


cpmalo87's picture
always use a proper filter...

Hi Rodney,

Here is a good site from Fred Espenak to start with concerning a general overview of the transit:

Of course you should (as I'm sure you know)never directly observe the sun. The only really safe way to observe the sun with a conventional telescope is to use a neutral density solar filter designed for solar viewing. These fit over the objective.  Never use a 'solar eyepiece' unless you want to destroy your scope or your eyesight. Baader sells relatively inexpensive filter material which can be used to make a homemade filter cell.  They sell two types: one for visual viewing and another for photographic use.  They also give instructions for constructing a safe filter cell:



SGQ's picture
Transit of Mercury: absolute timing in/egress for solar diameter

The transit of Mercury is a good occasion to measure accurately the diameter of the Sun up to 0.01".

I am preparing a tutorial which will appear soon on arxiv, following made for Venus. The draft is here

Basically the data should be a video or a sequence of photos of Mercury in ingress and in egress.

The timing of the photos should be as accurate as possible, after the choice of the images will be made when reducing data. Do not hesitate to send me your comment and your data over the email:

cpmalo87's picture
Ingress might be a problem


Thanks for your reply, Prof. Sigisimondi.  This is a very good collaborative opportunity. Obtaining Egress timings shouldn't be much problem for us here if the weather allows. If you don't mind, I have a few questions from our small team of amateur astronomers here:

1) Ingress is predicted to occur here at our location in eastern Arkansas (US) only ~7 minutes after sunrise.  Will accurate egress timings for our location be of any value if we miss ingress? 

2) If not, a second option would be to use video from the Malincam network. Hopefully, there will be a video of ingress from a station <100-200 KM east of us.  Would combining an ingress timing with our egress timing from such a location introduce too much error to be of use even if good GPS coordinates are given for both?

3)  If the answer to 1) and 2) above is no, then should we simply plan to travel east to a fixed location where we can view the entire transit in order to obtain useful data?


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