The Seventh Planet
|Apparent size:||3.7 arc seconds.|
|Diameter:||51,118 km (4 Earth diameters).|
|Distance:||2825.2 million km (157 light minutes or 18.9 astronomical units).|
|Image date:||2020- 11-25|
It was a moonlit night but the sky was clear so, despite the poor sky conditions, I decided to first check out the Moon and then have a look at Uranus.
Uranus orbits the Sun every 84 years, which means it moves slowly across the starry background at an average rate of just over one degree every three months.
It’s not much more than a dot in the image, approximately 0.001% of an angular degree in diameter as seen from Earth. When your target is only about twelve pixels across, it makes it very hard to produce a worthwhile image.
This shot was assembled from a 200 frame SER video file, stacking the best 20% of frames in Autostakkert, then cropped from 4944 x 3280 px to just 800 x 800 px – about 3% of its original size,.
I left my duo band Ha filter in the scope, although I wasn’t sure if that was a good idea or not. Probably not, because I seemed to get a bit more yellow and red than I would have expected.
Next time I shoot Uranus maybe I’ll over-expose it and look for its Moons. Five of the twenty-seven satellites are feasible targets between magnitude 13 to 15. The rest are too faint for my humble ‘scope but this is what they would have looked like:
|SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.|
|Field flattener; 2x Televue Powermate. ZWO Duo-band Hα (656nm) and OIII (500nm) filter.|
|SkyWatcher EQ6-R Pro mount; ZWO ASI120 guide camera.|
|Imaging camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).|
|Software: EQMOD, PHD2, SharpCap, Gimp.|
|Observatory location: 34° South.|
Images © Roger Powell
I’m a founder member of Macarthur Astronomical Society