Wesley's Tool-Box

I tried the Baader Moon & Skyglow filter early this morning to photograph comet C/2013 R1 Lovejoy with my Canon SX50 HS as I mentioned yesterday. It has some interesting effects to the photos.

It does tone down the white noise as intended, but the background turns from black to dark blue. The tail doesn't really become more bright because it's a filter that blocks certain wavelengths, not some sort of a booster. But due to slightly lower noise it's easier to make it more visible with post-processing.

For reference, the bottommost star in the cropped photo above is HR 4572 (HD 103799; HIP 58287), a 6.6 magnitude star in Ursa Major.

Settings: 243mm - ISO 1600 - 6s - f/5.6
Time: 2013-11-21 05:32 - 05:36 KST
Location: Suwon, Korea
15 photos stacked with RegiStax 6.1.0.8

A picture of a comet does not seem complete without a tail, and this was not apparent in my first attempt. A long-exposure photo is needed to bring this feature out, but three problems get in the way. One, stars move, so unless I have an expensive tracker installed, I would get streaks instead of dots, especially at high zoom. Two, Canon SX50 HS limits maximum exposure to 1 second for any settings beyond ISO 80. Three, light pollution whitens out long exposures.

The camera's limitation would need to be overcome first to determine how much I can push the other two issues. To do this, I ran CHDK on my camera, a hack that provides more features and removes limitations on top of the default firmware. I was able to easily take photos with 1-minute exposure at ISO 6400 with this. Sadly, this would yield a milky, unusable photo caused mainly by light pollution.

I experimented with the zoom and exposure settings, and determined that a 4-second exposure at ISO 2500 and around 10x zoom yielded not too much whitening or streaking of stars, while just about bring the tail of the comet into view. You can glimpse the tail shooting out at 11 o'clock direction. The noise makes it harder to discern it at 100% size, though.

For reference, the bright star at 1 o'clock direction of the comet is 57 Ursa Majoris (HR 4422; HD 99787), a 5.3 magnitude star in Ursa Major.

By the way, I did try to photograph comet ISON (C/2012 S1) with the same method, but the severe light pollution near the horizon basically washed any possible detail away. I should put the Baader Moon & Skyglow filter on next time if it can reduce this. If it works, then maybe I could catch the tail of comet Lovejoy better, although I still don't have much hope for comet ISON.

Settings: 278mm - ISO 2500 - 4s - f/5.6
Time: 2013-11-20 05:01 - 05:02 KST
Location: Suwon, Korea
25 photos stacked with RegiStax 6.1.0.8. Click the photo for 2x size.

While the popular media is focused on covering comet C/2012 S1 ISON, there are several other comets that are visible with amateur telescopes right now. One of them is slightly brighter than ISON at the moment - C/2013 R1 Lovejoy, and both are visible to the naked eye if you live in a really remote place. Lovejoy is around 5.3 magnitude, while ISON is around 6 as of this writing.

Comet ISON doesn't rise too high above the horizon before the sunrise washes its view away, so the light pollution in my area is prone to getting in the way of the view as well. In contrast, comet Lovejoy rises up quite high, so it would be in a relatively clear view. So for my first attempt to photograph a comet using my Canon SX50 HS, comet Lovejoy was set as the target.

When I got out to take its pictures, the comet was getting out of Leo Minor and moving westward to Ursa Major. I tried to locate it with Star Walk app on my iPad, but the comet was nowhere to be found, wasting a full hour. So I consulted CalSky instead and it said that it was actually a bit higher up. I searched for the comet there instead and immediately found it.

I set the camera to its most sensitive setting - ISO 6400 at 1-second exposure, and it barely recorded the fuzzy ball. Interestingly, the "bright" star next to it, HD 94456 (HIP 53360), was merely 7.4 magnitude. The 9.2 magnitude HD 94233 (HIP 53216) looked similar in brightness. This meant that the camera would at best only be able to record comets that are visible to the naked eye. I guess photographing comet ISON may be quite a bit more challenging.

On the upside, this sighting posts the upper limits of SX50 HS astrophotography at about 10 magnitude. This should be enough to photograph Uranus, Neptune, and Saturn's moon Titan.

Settings: 1200mm - ISO 6400 - 1s
Time: 2013-11-18 05:14 - 05:15 KST
Location: Suwon, Korea

Photo 1: 05:14, Reduced to 12.5% size, 21 photos stacked
Photo 2: 05:15, Reduced to 50% size, 27 photos stacked
Stacked with RegiStax 6.1.0.8. Click the photo for 2x size.