Wesley's Tool-Box

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

Since my last observation of the Comet C/2014 Q2 Lovejoy, I waited for the sky to clear up again so that I can try shooting with a star tracker (iOptron SkyTracker) installed. The opportunity came on the night of January 8. Annoyingly, all the attempts to take long exposure photos failed. I first thought the tracker may be faulty, but later I realized that the image stabilization on the camera lens was negating the tracker's movement.

I vowed to not make the same mistake again, and two days later, I went out to take photos of the comet once more. The southern sky was dark enough to let me barely see the comet with my naked eyes, so my hopes were up. And indeed, I finally got the results I wanted - much improved photos of the comet using the 30-second exposure (longest possible on Canon 450D other than bulb mode) setting. The green glow was now evident, and the center of the comet was shining brightly.

For the reference, the comet had moved to near the constellation of Taurus - the large version of the photo shows the magnitude 5 star 40 Tauri on the far upper left. Also, under the camera settings I used, the darkest stars were around magnitude 12, which is the most sensitive I've gotten out of my astrophotography attempts so far.


After taking the photos of the comet, I felt that it would be nice to point the camera at another object since the tracking setup was already in place. As the sky at my location was especially dark in the east and the south, I decided to take a look at the Orion Nebula inside the Orion constellation, which was in the east, going south.

Alas, due to being out for more than an hour in the below-freezing coldness, the infinity focus of the lens wasn't working quite right anymore and the fog on the lens was getting bad. So I took some measures to mitigate these issues somewhat and was able to salvage several shots before heading home. Luckily, those shots came out looking fine.

Device: Canon EOS 450D + Tamron 18-270mm Di II VC PZD
Settings: 432mm - ISO 800 - 30s - f/6.3
Filters: None
Location: Naju, Korea

[Comet]
Time: 2015-01-10 21:39 KST (21:25-21:52)
12 photos stacked with RegiStax 6.1.0.8

[Nebula]
Time: 2015-01-10 22:26 KST (22:07-22:31)
7 photos stacked with RegiStax 6.1.0.8

Australian amateur astronomer Lovejoy's 5th comet, C/2014 Q2, is coming closest to Earth on January 7, 2015, and it has been getting brighter in the recent weeks. On a clear dark sky, it's currently bright enough to be seen with a pair of binoculars, as its magnitude is around 5. The sky at Naju cleared up last Friday night, so I went out to take some photos of this comet.

When I took the photos, the comet was near 60 Eridani, a 5.0 magnitude star in the constellation Eridanus, which made it easier to position the camera by hand. You can see the C/2014 Q2 as a fuzzy, slightly green ball here. The faint star above the comet is TYC 5899-440-1, a 9.6 magnitude star. The faintest stars in the photo are around magnitude 10.0.

This was the first time I used my Canon EOS 450D DSLR to take celestial photos since the Venus transit of 2012. The job was relegated to SX50 HS in 2013, but unless I'm taking photos of the planets or satellites, I felt that the larger sensor would work better, so I took the 450D out of storage for this session. It seems to have paid off. I had to resort to a relatively short (2.5 seconds) exposure because I didn't use the star tracker this time, but I still had good results.

Device: Canon EOS 450D + Tamron 18-270mm Di II VC PZD
Settings: 394mm - ISO 1600 - 2.5s - f/6.3
Filters: None
Time: 2015-01-02 22:48-22:51 KST
Location: Naju, Korea
14 photos stacked with RegiStax 6.1.0.8