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I attempted some more "extreme" daylight observations today including a daytime observation of the planet Uranus! Transparency was not too bad (good for this time of year) so armed with the C8, 220x and a GOTO I started looking late in the afternoon with the Sun up around 5 degrees from the horizon.
Jupiter was a spectacular sight with obvious cloud detail and all 4 Galilean moons visible. IO and Europa, mag 5.6 and 5.9 respectively, were rather easily visible possibly due to proximity to the planet itself. After locating Ganymede, I then moved onto spot Callisto at only mag 6.4. I would never have though I would be able to see something at mag 6.4 with sun shining brightly against the side of my face!
With the Galilean moons under my belt I then moved onto something more challenging - Uranus. Uranus being lower in the sky, non-stellar and not located near a bright object was going to be tough. To ensure I got accurate Goto I star hopped down from Jupiter in the sky to various stars of around mag 4. These stars were all clearly visible, and I could centre the star and update the Goto pointing. My first attempt failed to find Uranus but I hopped across to a mag 5.5 star and found it, then a nearby mag 5.9 star and also found that. Perhaps because the sun was getting lower, on my second attempt the planet Uranus was finally visible (with the sun a calculated 2.7 degrees above the horizon!). In the daytime sky the Planet's tiny limb darkened disk seem to give it a vague diffuse appearance - it was visibly non-stellar.
As the sun neared the horizon I then slewed back to Jupiter. How faint could I go with the sun still up. Well I succeeded in getting a mag 7.1 star just before the sun touched the horizon, and then a 7.4 star as the sun was setting!
Don't ask me why the fascination with seeing stars by daytime, but it is certainly a "cool" experience. I also find the star colour seems to be more obvious in daylight, perhaps because colour sensitive vision is fully activated and perhaps because of the contrast against the blue sky.
Terry
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