The tiny inner planet Mercury will be seen passing across the Sun (transit) on 9th May, 2016. Although the event will happen fourteen times this century, the next one visible from India will be in 2032. Hence the 2016 transit is a great opportunity to catch this mini-eclipse and also for us to utilise for astronomy outreach.
Start transit : 16:30 IST → 1/4th transit : 18:30 IST → Mid transit : 20:30 IST → End Transit : 00:32 IST
What will we see?
Path & important times of the Transit for Indian observers.
The event starts at about 4:30 pm and is visible all over India. The first contact occurs at 16:32 IST; however the entrance of the dot may go unnoticed since the contrast at the edge is not sufficient enough. Within minutes the planet Mercury will appear as a tiny dot on the Eastern limb of the solar disc and will become identifiable. Watch out for other sunspots too that may be present.
Mercury will appear as a dot on the solar disc moving roughly from East to West. For an Indian observer this would mean that Mercury will move from the "top" towards the "bottom" of the Sun as it moves towards the western horizon.
As the dot moves inwards the center of the Sun's image, the visibility will improve. Mercury will be at a quarter of its path in front of the Sun at about 18:30 IST. The central point occurs at 20:27 IST when the sun would have set long for us in India.
The best opportunity to view the transiting Mercury is after an hour into the event, when the effect of atmospheric absorption is still not strong enough. The transit continues beyond the sunset. Hence it should be safe to try to look for it or photograph it on the setting Sun. However the size of Mercury being small, recognising it as a black dot requires extra effort. A magnification tool (binocular / telescope) is definitely needed unlike in the case of Venus in 2012, which was strikingly noticeable as a fairly large spot.
In India, we will catch only the initial part of the transit before sunset. Most of Central and South India will see up to the initial 1/4th of the transit and North and West India will see the initial 3/8th of the transit. The Eastern part of India will see the initial 1/8th of the transit only. This translates to 2 hrs, 3 hrs and 1 hr respectively. Discounting the last hour (haze, clouds, dust, landscape etc), that gives us 1, 2 and 0 hrs respectively. This is what we will have to work with and make the best of.
In addition, it is obvious that since Mercury is only 1/158 of the Sun's apparent diameter, a telescope with a magnification of 50x or more is needed to watch this event. See below for help with this.
Sharing the Transit
If you have a small telescope, know how to project the Sun's image, and have access to a public location from where the western sky can be seen clearly, try and set up an observation by inviting the local community to come and watch the Transit with you. Join us in a nationwide effort to share this spectacle with all people. Please use the form linked below to register your event.
Register your event in a nationwide effort to share this spectacle with all people.
Warning: It is very dangerous to observe the Sun through any unfiltered optical system (lenses, binoculars, telescopes & even your bare eye). This may cause serious eye damage and even blindness. The transit observation also involves looking at the sun and hence all the precautions that apply to the observations of Sunspots and Eclipses apply here too and are essential.
* Good quality "Eclipse goggles" (without any tiny holes in them!) may be used, but Mercury will be very hard to spot with the naked eye.
* A better arrangement will be to put Mylar sheets or commercially available Solar filters in front of the objectives of the binoculars / telescopes that you are using. The magnification provided by binocular should suffice to show the event.
* Projections with small telescopes, similar to those done for solar eclipses, would be ideal. We recommend this method as it can give you larger images and they can also be shown to many people.
Here are some more resources about safe viewing methods and accessories :