Wesley's Tool-Box

As Pluto moved toward the western horizon, a planet started to come into the telescope's view through the southern window - Neptune. It was the first time I had seen it in person, but seeing as how relatively dim it is compared to other planets (magnitude 7.8), I decided to take photos the same way I do for stars.

Sure enough, it was caught on the photos as a moving bright spot, next to a 6.9-magnitude star called HD 214686. But I soon discovered that it wasn't the only object moving. A faint dot of about magnitude 13 was moving considerably faster than Neptune. Given the brightness, it had to be a small but known celestial object.

Consulting the minor planet database revealed the object to be 303 Josephina, an asteroid from the main belt with a diameter of about 100km. Out of pure coincidence, I had caught a planet and an asteroid together on several photos.


But the surprise didn't end there for me. I noticed that Neptune either had a bump or a small dot next to it. It turned out that it was Triton, by far the largest satellite of Neptune with apparent brightness of magnitude 13.5. Photographs taken a day apart clearly shows its changing position relative to the planet, as well. So thanks to the long exposure photography, I was able to take a planet, a satellite, and an asteroid all at once.

Here's the full version of the final frame of the animation, if you want to see it.

Telescope: Celestron NexStar 6SE
Device: Sony A5000 (prime focus)
Settings: (1500mm) - (f/10)
Filters: None
Location: Naju, Korea

#1: ISO 800 - 20s - 2015-09-10 00:14 KST
#2: ISO 800 - 20s - 2015-09-10 01:12 KST
#3: ISO 800 - 20s - 2015-09-10 02:34 KST
#4: ISO 1000 - 30s - 2015-09-10 23:28 - 23:30 KST (3 photos stacked)
#4: ISO 1000 - 30s - 2015-09-11 00:32 - 00:37 KST (2 photos stacked)

One of the main reasons I decided to buy a new camera was that it would yield a lower-noise photo at high ISO settings, making it better for long-exposure astrophotography. To confirm this, one of the first objects I chose to take photos of was the dwarf planet Pluto.

It moved a little to the east since the last time, already past the ξ2(Xi 2) Sagittarii and not near a particularly bright star. The brightest stars in the animated frames above are only about magnitude 11. Nevertheless, Pluto was discernible when comparing the two frames taken a day apart under a bright monitor. Dimmest stars visible reached magnitude 15, and Pluto itself moved clearly enough to see that it's not a background star.

If you feel particularly bored, you can try picking it out of the full version of the September 10 photo.

Telescope: Celestron NexStar 6SE
Device: Sony A5000 (prime focus)
Settings: (1500mm) - (f/10)
Filters: None
Location: Naju, Korea

#1: ISO 800 - 20s - 2015-09-09 22:09 KST
#2: ISO 1000 - 30s - 2015-09-10 21:44 KST