Unfortunately not my image: Mercury starting its transit across the Sun today, photo by NASA.

The transit of Mercury across the face of the Sun takes place about thirteen times each century and today was one of those occasions; the next is on 11^th November 2019.  With months of bad weather I’ve been unable to undertake very little astronomy for some time but albeit late, spring actually arrived last week and I took the opportunity to shake-down my equipment and experiment with settings for solar imaging in the hope of capturing Mercury’s transit.  Using a Baader solar filter and both the William Optics GT 81 and Skywatcher 150PL, I have successfully imaged the Sun before.   Of course, inevitably I aspire to a dedicated Lunt or Coronado solar telescope one day in order to image details of the chromosphere and prominences, which are not visible using a white-light solar filter.

Sun spot activity is limited at the moment but the Baader filter and WO GT81 do a reasonable job, although I find achieving focus of the Sun quite difficult.  Using the DSLR I experimented with the field flattener and an alternative basic 1/ 1.25” nosepiece, which produced a preferable result of a slightly larger and sharper image.  I also tried the ZWO ASI 120MC webcam but as I don’t use this very often struggled to get the settings right for any sort of image – I’ll experiment more with that over the summer. I also put EQMOD-ASCOM and the newly acquired gamepad control through their paces which both worked well, so I was ready for the transit – weather permitting.

Last week’s test image of the Sun, with sun spot top left: WO GT81 + 1.25″ nosepiece | 1 / 2,500 sec @ ISO 100

After days of sunshine, albeit with high cloud that has continued to prohibit astrophotography at night, I was nonetheless hopeful of seeing at least some of the transit today.  Notwithstanding, Sods law arrived in the form of a belt of cloud over south east England last night!  Not to be defeated I watched the sky and cloud forecasts which suggested a glimpse of the transit might still be possible.

In hopeful anticipation I set up the equipment just before contact at 12.12 pm BST and shortly afterwards obtained a good view of Mercury as it started its transit across the face of the Sun. For the next three hours I managed glimpses of the planet as it continued its journey.  It is very, very small but forms a distinct, sharp black dot against the background of the Sun when compared to the more diffuse, grey nature of the sunspots.  It was an exciting experience and despite the drawbacks – cloud has now completely covered the sky for the rest of the transit – it was very enjoyable; so what’s the problem?

Despite all my preparation for imaging everything that could go wrong did and I was unable to obtain even a single photograph:

• On setting up the camera and starting to focus the EQMOD-ASCOM tracking stopped and Carte du Ciel froze. Despite re-starting the set-up numerous times the tracking would not work!

• Finally after resorting to the Synscan handset for tracking control, for some completely inexplicable reason I could not get any sort of image on the camera, that otherwise was working OK!

As I have learned many times before, the art of astronomy is patience and persistence but I am very disappointed not to have imaged Mercury during its transit today.  Ironically once the cloud put an end to further activity, I tested the EQMOD-ASCOM tracking once again and it worked fine.  Perplexed does not describe my feelings – oh well, 3-years to prepare for the next transit!

How I felt after today’s imaging!!! The transit view was still very good and I’m grateful for the breaks in the cloud.