Saturday, January 24, 2015

Jupiter Triple Transit

Last night was the publicized "triple transit" where the shadow of three Jovian moons were visible simultaneously on the surface of Jupiter. In this case, Io, Callisto, and finally Europa. What a stroke of fortune that all of the recent rain and overcast skies cleared for the show as today it is overcast again. As usual, seeing was not very good at my site but did improve between first test shots at 23:00 and beginning of the triple at 00:28.

I created the image using a movie with about 2000 frames taken on 2015-01-24 at 00:38 CST. The movie was captured on a Canon 60Da using its handy VGA Movie Crop mode that gives a 1:1 pixel ratio image (no compression, no downsampling) at 60 fps. I connected the camera through a Televue 5x Barlow to a TMB-130ss refactor giving an effective focal length of 4550mm. Since the camera generated a MOV file, I extracted the individual frames to BMP images using IrfanView 4.36 and then imported them into RegiStax 6 for alignment, stacking, wavelet sharpening and color alignment. I imported this processed image into Photoshop CS6 and further tweaked the saturation, contrast, and brightness as well as adding labels. The moon and shadow positions shown are based on simulation in SkyTools 3.

Given the quality of the raw movie frames, I am surprised that I was able to extract recognizable images of not only the shadows but also of the moons that caused them. The disk of Io was particularly challenging and shows up subtly as a yellower disk region. I was not able to see this disk in any single raw frame.

Monday, January 19, 2015

Backyard Visitor

Today, Danielle relayed an interesting experience. She was eating lunch when our Labrador suddenly started barking at the backyard window. She looked out and saw a bird take off which she first thought to be a large dove. Then, she looked in the tree and saw this Sharp-Shinned Hawk. It might be a second year immature bird based on the eye-color which is supposed to transition from yellow to red. She got a few quick shots with the Canon SX-50 before the hawk then flew down towards the window. She did not see it come back up, so in a few minutes, she went outside to see if it had gotten hurt or had caught something. She did not see the hawk but a few sparrows took advantage to fly out from behind the flower pots behind which they had been hiding.

Saturday, January 17, 2015

Comparison of Canon 400mm prime and 100-400mm zoom

The images below are from a test of our two birding lenses, the Canon 400mm f/5.6L USM prime lens and the Canon 100-400mm f/4.5-5.6 IS USM (Mk I) zoom lens. The tests were shot from positions 2ft apart of a stationary target 20ft away. The log target has fine details similar to a bird.
Test images were taken with the same Canon 7D II camera set to fine resolution center AF and exposed at f/5.6, 1600sec, ISO-800. Both shots were taken on a tripod with a cable release but mirror lockup was disabled. IS was turned off on the zoom lens. The CR2 images were imported into Photoshop CS6 with the default conversion parameters. Same 100% crop was applied to both images but no further processing performed. Images were saved as a single highest resolution 8bit JPG at original resolution. Both contrast and resolution are clearly superior in the prime lens. Though this difference is not critical for frame-filling subjects, it is noticable on tight crops of small birds.

Wednesday, January 7, 2015

Comet C2014/Q2 Lovejoy

Terrible astronomy weather this week and for the foreseeable future. However, this evening, on the day of closest approach, I manged to get about an hour of viewing with sort of clear skies. I set up a 70-200mm f/4L lens at 200mm with a QSI-540 and took four 5min frames in each of RGB colors. I used the comet head as a guide-star for tracking. In retrospect, these frames were too long to get sharp stars in the star-aligned frame. A length of 120s would have been better.  I also had some difficulty getting a usual median-combine operation on the comet-aligned frames to eliminate the stars. I had to do a lot of manual cleaning but was still left with messy streaky noise.

Friday, January 2, 2015

Whooping Crane in Williamson County

On a report of another rare bird in the county, we went in search of a lone Whooping Crane mixed with a flock of Sandhill Cranes. It was reported in north east Williamson County, in the area of County Road 420.  Fortunately, finding a flock of cranes is pretty easy once you get to the right spot. All told, we saw several hundren sandhills and, sure enough, found the lone adult whooper.

Sunday, December 28, 2014

Using Image Stabilization on a Tripod

I had been taking lightly the recommendation that Image Stabilization (IS) be turned off on my Canon 100-400mm f/4.5-5.6L IS lens when using on a tripod. After having many soft pictures, I did another side-by-side test on a real subject.

The images below were taken of a snowy egret at about 50ft with camera mounted on a tripod. In both cases, I used back-button focus in AI Servo mode. Before each shot, I unfocused the lens, let AF acquire focus on the feather detail, and let the IS settle for a second before taking the shot. The effect of using IS when "not needed" is pretty dramatic. What I am still uncertain of is what constitutes "not needed".  I have taken slow tripod shots where the IS slightly improved the shot. Is it "tripod and fast shutter" or "tripod or fast shutter" that requires turning off IS.

Sunday, December 14, 2014

Red-Shouldered Hawk Pair

As we prepping the trailer this morning, we head the cry of a hawk nearby. A Red-shouldered Hawk flew in over the house and perched on a dead tree across the road. As we watched and took pictures with our grab-and-go SX-50, a second hawk flew in an perched below. They stayed for a few minutes and then flew back over the yard towards the river again. I wonder if this is the same pair we saw mating here last year. We never did see the establishment of a nest.

Canon SX-50 - 215mm, f/7.1, 1/320 sec, ISO-100

I had not used this little camera in a while. Even at low ISO, I was amazed to see how grainy the images were. The color fringing against the backlit sky were also pronounced.