Wesley's Tool-Box

As Saturn now rises before midnight, it becomes possible to see the planet well above the horizon before it disappears into the morning sky. Seeing that the weather was getting good, I decided to wake up early and see it for myself for the first time this year. I bought a new Celestron NexStar 6SE telescope some time ago and I could use it to pick it out of the southern sky with relative ease.

Unfortunately, one of the collimator screws on the telescope is stuck, preventing full calibration. I attached my DSLR to take some photos, but it did not come out well. So instead, I made a couple of quick shots using my iPhone 6 Plus through the eyepiece, which for some reason came out looking slightly better.

Not to waste the opportunity, I then took out my SX50 HS and photographed Saturn as I've done since two years ago. The result was the best the camera has produced so far, I think.

[Left]
Device: Canon SX50 HS
Settings: 1200mm (2x enlarged) - ISO 160 - 1/30s - f/6.5
Filters: None
Time: 2015-03-23 05:35 KST
Location: Naju, Korea
20 photos stacked with RegiStax 6.1.0.8

[Right]
Telescope: Celestron NexStar 6SE + 25mm eyepiece + 2.5x barlow
Device: iPhone 6 Plus (afocal)
Settings: 29mm - ISO 125 - 1/10s - f/2.2
Filters: None
Time: 2015-03-23 06:02 KST
Location: Naju, Korea

When Venus is visible in the evening sky, a crescent Moon can be found nearby roughly once a month in the west. The clouds and fogs cleared up yesterday evening, and I was able to see the two objects above the unfinished skyline of Naju Bitgaram City. A yellowish layer of smog is seen lingering on the horizon in the photo, but this was gone by the morning.

Device: iPhone 6 Plus
Settings: 29mm - ISO 500 - 1/4s - f/2.2
Filters: None
Time: 2015-03-22 19:29 KST
Location: Naju, Korea

When I last looked at the comet C/2014 Q2 Lovejoy about three weeks ago, it was near its peak apparent brightness due to its proximity - it passed the closest to Earth just 3 days ago and shined at a magnitude of 4. The comet had now moved away, making its closest approach to the Sun two days before this observation. It was still relatively easy to capture it on the camera, as it's only dimmed back to magnitude 5.

The comet had moved to the constellation Andromeda. 59 Andromeda was below the comet, just outside the enlarged photo. The bright star directly above the comet in the enlarged photo is a magnitude 6.6 star called HR677 or HD 14272.

Some issues now complicate its observation other than the slow dimming. From where I observe, the western and northern sky is lit up with light pollution from the center of the city. And these days, constellation Andromeda is in the western sky, already starting to head toward the horizon after sunset. So I have to observe it in the early night, just when the area of the sky is not too brightened one way or another, at around 9 to 10 PM. The dimmest stars in this photo is around magnitude 12, so I think it was a success.

Device: Canon EOS 450D + Tamron 18-270mm Di II VC PZD
Settings: 432mm - ISO 400 - 30s - f/6.3
Filters: None
Time: 2015-02-01 22:29-22:39 KST
Location: Naju, Korea
8 photos stacked with RegiStax 6.1.0.8

I wanted to revisit my thought that the DSLR (Canon EOS 450D) would take better deep-sky photos than a P&S (Canon PowerShot SX50 HS). The latter has a much more powerful zoom lens, so maybe it could help overcome the limitations of the small sensor. 450D's APS-C sensor has 13.3 times the area of the 1/2.3" sensor used in the SX50 HS.

After some trial & error, I found that my iOptron SkyTracker, once properly calibrated, could be usable even at a focal length of 1200mm (35mm equivalent) if the exposure time is 30 seconds or less. So I decided to take photos of the beautiful Orion Nebula at the maximum zoom of both cameras.

The 450D was able to take a low-noise photo of the nebula with nice-looking colours. But the limit of the zoom was apparent. Also, under the below-freezing temperatures (it was around -2C) the infinity focus of the lens shifted further out after about an hour.


With the SX50 HS, the resulting photos were expectedly more grainy in general at full resolution. I felt that the ISO 100 setting on SX50 HS would still yield a grainier photo than 450D's ISO 400 setting. But the super-zoom lens and stacking were able to make up for this. After taking the photos at the maximum zoom and reducing the size, the photos still had more details than that of the 450D.

Judge for yourself with the two photos above. I should note that even when stacked, 450D couldn't get much more details out.

I guess the SX50 HS is still quite alright after all. Oh, and the focus was more or less stable during the similar long session under below-freezing temperatures. I think 450D needs a better zoom lens... or a real telescope to make it fulfill its potential.

[#1]
Device: Canon EOS 450D + Tamron 18-270mm Di II VC PZD
Settings: 432mm - ISO 200 - 120s - f/6.3
Filters: None
Time: 2015-02-01 21:46 KST
Location: Naju, Korea

[#2]
Device: Canon SX50 HS
Settings: 1200mm - ISO 400 - 30s - f/6.5
Filters: None
Time: 2015-01-31 23:12 KST (23:12-23:49)
Location: Naju, Korea
10 photos stacked with RegiStax 6.1.0.8

Stars in the sky slowly move together in the sky due to the Earth's rotation. So the long exposure astrophotography involves using a star tracker to negate this motion. However, objects closer to Earth like the other planets tend to move slightly differently, and the change in position is noticeable over the course of a few days, as I've shown with the asteroids.

This movement is especially pronounced with the comet C/2014 Q2 Lovejoy these days, as it passed by Earth recently to approach the Sun. This 12-frame animation shows the comet moving through the sky over a 27-minute period, at an interval of roughly 2.5 minutes. These are from the images that were used to make the stacked image of the comet in my earlier post.

Device: Canon EOS 450D + Tamron 18-270mm Di II VC PZD
Settings: 432mm - ISO 800 - 30s - f/6.3
Filters: None
Time: 2015-01-10 21:39 KST (21:25-21:52)
Location: Naju, Korea