Wesley's Tool-Box

I've recently bought a motorized equatorial mount called iOptron SkyTracker, which enables the camera to track the stars at the same speed as they move in the sky. This is useful for photographing faint objects through long exposures. But since the light pollution in the city sky hinders long exposure photography in the first place, I was unsure whether this would be of much use.

To see that the mount works as intended and is still useful under an uncooperative sky, I decided to try photographing two kinds things - asteroids and galaxies. For asteroids, the two brightest, Vesta and Ceres, were chosen. They were close to each other while moving in the constellation Virgo, between Arcturus and Mars, in the southern sky around midnight. Ceres is also a dwarf planet, so I would be photographing two types of celestial body at once.

For three nights (April 21-22, 23-24, and 24-25), I photographed the area just above Zeta Virginis (a.k.a. Heze) to catch the movement of two objects. The SkyTracker mount was used on the first and third night because the sky was clear, but the second night was riddled with fog in the lower sky, hindering the view of Polaris which is needed to calibrate the mount. So I had to take the photo using only the camera on high-ISO, (relatively) short exposure settings.

Two things became evident in this round of photographing. One, Vesta (magnitude 5.7) and Ceres (magnitude 7.0) could be clearly seen moving towards west each day. Two, the SkyTracker mount did an excellent job tracking the stars and the asteroids, producing images far better than using camera only. The second night's photo had small streaks, despite having only 10 seconds of exposure. Here are the full resolution photos used for the animation.


Device: Canon SX50 HS
Filters: None
Location: Suwon, Korea

#1: 121mm - ISO 80 - 300s - f/5.0 - 2014-04-22 00:05 KST
#2: 121mm - ISO 1600 - 10s - f/5.0 - 2014-04-24 00:07 KST
#3: 119mm - ISO 80 - 300s - f/5.0 - 2014-04-24 23:19 KST

Shortly after watching the MetOp-A satellite flare, I pointed the camera vertically up for a test of how long I could leave the shutter open before the light pollution whitened things out. In the process, the entirety of two constellations, Urga Major and Leo Minor, were caught in the resulting photo. The Big Dipper makes up the bottom portion of the Ursa Major.

If you click on the image for the full resolution version, the star trails are noticeable. I'll be trying out a star tracker I recently bought to see if this can be effectively eliminated. Too bad the weather these days are generally cloudy.

Device: Canon SX50 HS
Settings: 24mm - ISO 80 - 60s - f/3.4
Filters: None
Time: 2014-04-08 21:31 KST
Location: Suwon, Korea

Launched in 2006, MetOp-A is the first European operational meteorological satellite, which is in a polar orbit. It currently serves as the backup of the MetOp-B that was launched in 2012. They also exhibit flares, although relatively less frequent and dimmer compared to the Iridium fleet.

This photo is a first for me in many aspects. It's the first time I did a long-exposure capture of a satellite flare. Previous ones were done in burst shots, then later animated and/or composited. It's also the first time that I used SX50 HS to capture a flare. iPhone 5S is better at burst shots, but not long exposure. Finally, this is the first non-Iridium flare that I caught in a photo.

The satellite moved downward in the northern sky, below the bright Polaris visible on the left side of the photo. If you click on the photo for a larger version, you can see most of the constellation Ursa Minor / Little Dipper covering the top part.

Considering the light pollution, this observation suggests that the satellite needs to be at least -1.0 magnitude at maximum, and be more than 30 degrees above horizon to make a noticeable streak in the photo. I guess that explains why I couldn't catch Tiangong-1 space station on photo several months ago.

Device: Canon SX50 HS
Settings: 45mm - ISO 200 - 15s - f/4.0
Filters: None
Time: 2014-04-08 21:26:38 KST
Location: Suwon, Korea
Max Magnitude: -2.2

While I have observed the International Space Station (ISS) making a pass in front of the Sun before, it was at a resort far away from home. Yesterday, I had the good fortune of witnessing a pass right at home. My daughter Celine wanted to help out, so I let her set up the equipment and we went to the parking lot to start photographing. We took the photos of the Sun together, and in three of the frames, the ISS was found crossing in front of the Sun. Here is the composite of the three frames set against the stacked 32 frames I shot in 14 seconds while attempting to capture the transit, both in the annotated and full version.

The last frame was really lucky, as it was taken just before ISS got out of the Sun's disk - 0.1 seconds late and we would have ended up taking two frames instead. SX50 HS's regular burst mode takes a photo every 0.43 seconds, so given the transit time of less than a second, this was the best outcome I could expect.

I do wish the fast burst mode, which can take a photo every 0.077 seconds, could take more than 10 photos at once, though. The transit prediction from CalSky is pretty accurate, but local clock error and human reaction delay can creep in. So I would need it to last at least five seconds or so. I should either wait for Canon to make a superzoom camera that can shoot longer bursts, or install an iPhone 5S, which can do 0.1-second burst shots for several minutes, on a telescope. I'm saying this because I missed the Moon - ISS transit on Saturday while using the fast burst mode.


Anyways, here's the animated version of the transit that illustrates the movement quite well. Come to think of it, this sort of pass would be hard to see in person with binoculars - ISS is tiny and moves quite fast, so unless the Sun is magnified really big, it'd be hard to notice.

Device: Canon SX50 HS
Settings: 1200mm - ISO 500 - 1/1250s - f/6.5
Filters: Baader AstroSolar Safety Film
Time: 2014-03-23 08:57 KST
Location: Suwon, Korea
Base photo: 32 photos stacked with RegiStax 6.1.0.8 (08:57:10 - 08:57:24)
Animation: 5 photos (08:57:16.8 - 08:57.18.5)

Sun is measured to be the most perfectly round sphere occurring in nature. But as the Sun sets over the horizon, it looks more "squished" than usual due to atmospheric refraction. This photo was taken when the Sun's altitude was merely 3.27 degrees.

You can still see the sunspots just fine - AR11960 (top; "sunspot 1960") and AR11959 (bottom; "sunspot 1959") are visible at the lower area. The light blemish at the lower right edge is the AR11957.

Device: Canon SX50 HS
Settings: 1200mm - ISO 80 - 1/40s - f/6.5
Filters: Baader AstroSolar Safety Film
Time: 2014-01-26 17:25 KST
Location: Suwon, Korea
79 photos stacked with RegiStax 6.1.0.8