Jupiter, Mars, and a red spot I could not quite see
January has been generous with planets. Jupiter sits high in Taurus in the evening, not far from the Pleiades and the V of the Hyades, and Mars reached opposition on the sixteenth in Gemini, rising as the Sun sets and glaring orange all night. Venus is a lamp in the south-west after sunset. On a clear evening you can stand on the back step and point at three planets without moving your feet.
Last night was clear from about 19:30 until cloud came over at 22:10. Temperature −1 °C, seeing unsteady at first and better later, which is the usual order of things.
Jupiter
At 70× it is a small, bright, slightly flattened disc with two obvious dark belts and all four Galilean moons strung out in a line. That much is easy. What I wanted was the Great Red Spot, which I have read is possible in a small telescope when it is facing us and the air is still. I spent forty minutes on it. There were moments, perhaps three or four seconds each, when the southern belt seemed to have a notch or a paler hollow in it. I cannot honestly write that I saw a red spot. I saw a place where a red spot might reasonably be.
Part of the trouble is that the spot is not as red, or as large, as it was in the drawings in the books I grew up with. It has been shrinking for well over a century. This NASA Goddard clip is the clearest explanation I have found of how its size has changed, and why it also wobbles and stretches over shorter periods:
It is about two minutes long and worth watching twice: once for the animation, and once for the comparison of the spot across the decades, which is the part that explains my evening. I find it reassuring, in a petty way. If it was still the size it was in my childhood books, I would have no excuse.
Mars
Mars at opposition is the brightest it will be for a couple of years, and through the 70 mm it is still tiny: an orange disc smaller than Jupiter by a factor of three or so. At 70× it boiled in the low air. I waited for it to climb, came back at 21:40, and on a few steady moments thought there was a brighter patch at one edge, which would be the northern polar cap. I am about seventy per cent sure. The colour, at least, is beyond doubt.
Notes for next time
- Check when the Great Red Spot crosses the middle of the disc before going out. I did not, and that is the most likely reason I failed.
- The 28× eyepiece is better than 70× when the seeing is poor. A small sharp image beats a large soft one.
- Mars gets higher later. Look at it last, not first.