Tuesday 30th April was sunny all day, the last patches of cloud drifting away to the north in late afternoon. After my previous encounter with humidity and moonlight in Kentmere, it looked like a good opportunity to test this new dark site.
This is how my setup looks. Just me, a layby and the EQ3-2 equatorial mount. At 9.30pm the Sun has already set, but I wanted to leave plenty of time in case it clouded over and I had to dash to another location. It will be another couple of hours before the Sun is 18 degrees below the horizon, the offical end of astronomical twilight.
These unprocessed frames with the Sun only 15 degrees below the horizon show what a difference that makes to long exposures.
Two frames of 4 minutes each, stacked as layers in Photoshop. PANSTARRS is in the centre, moving from Cassiopeia to Cephus. The settings of ISO 800 and 240 seconds were inspired by Fred Espinak’s version, using pretty much the same kit. I guess the difference in our results is an indication that, even on a good night in Kentmere, conditions in Arizona are better. The thousands of stars in the bottom left corner (Cassiopeia is in the Milky Way) become so indistinct through our 80% humidity that they look like background glow, and any attempt to eliminate them damages the rest of the picture. On the other hand, it could just be that Fred is much better at this than I am.
With the 300mm lens, the optimum aperture is f/5.6 so I have wound the ISO up to 3200 to compensate. Four minutes tracking with the 300mm lens is quite satisfying, with the stars showing no sign of trail.
PANSTARRS is passing close to two nebulae, Cederblad 214 and NGC 7822, between Cassiopeia and Cephus. While neutralising the background, I notice that I have caught some nebulosity in Cederblad 214 – that’s the reddish glow to the right of PANSTARRS.
The comet itself still has two distinct tails. The ion tail points away from the Sun (towards one o’clock in this photo) and the dust tail trails behind the comet (towards nine o’clock in this photo).
Before packing up, I can’t resist an attempt at a five-minute frame. The tracking seems to hold up well, which promises much for future sessions.