Saturday, July 26, 2014

Rho Ophiuchi at Canyon of Eagles

This evening was another Austin Astronomical Society members-only star party at Canyon of Eagles. I went with the goal of trying to re-image the Rho Ophiuchi Nebula. My last attempt, in August 2013 using the same camera and lens, was a disappointment due to image noise.

This time, I used my homemade cooler box and made sure I took a series of dark frames. My ISO and aperture settings were the same as last year, as was the total integration time. However, in an attempt to further reduce noise, I halved the individual exposure times to 300 seconds, enough to detach the histograms from the black-point. With an ambient temperature of about 85F, I was able to cool the camera enclosure down to a steady 66F. The noise had the same diagonally-banded characteristics but at a lower level. This allowed me to boost the shadows more before the noise became problematic. All image acquisition control via Astro Photography Tool.

I am considering purchase of an adapter to connect my QSI-540ws directly to the Canon lens; there is still no comparison between the noise level of the astronomical camera and a DSLR.

Rho Ophiuchi - Canon 60Da / Canon EF 70-200mm f/4L - 28 x 300s, ISO-800, 200mm, f/4.
Thanks to Dave and Ed, my neighbors for the evening, for sharing visual views through the large Dobsonian.

Saturday, July 12, 2014

Highland Mall Purple Martin Roost

After Danielle saw a post on the Birds of Texas Facebook page, we drove down to the Highland Mall in Austin to see the Purple Martin Roost that occurs here each summer. According to members of the Travis Audubon Society, which leads field trips to the mall, tens of thousands of martins roost in a few trees as they stage for their migration down to Brazil. The cluster of trees in which the martins are roosting this year is circled below

We arrived in the parking log behind Jack in the Box on the north side of the mall around 7:30 PM. Initially, we saw martins arriving in small group, swooping over our heads. This gave me some practice photographing birds in flight such as this female Purple Martin.

Canon EF 100-400mm f/4.5-5.6L - 400mm, f/7.1, 1/320s, ISO-400
As sunset approached, the waves of birds became larger and larger. Per the suggestion of the Travis Audubon Society, many spectators were sporting umbrellas to keep off the droppings. At sunset, the birds began to settle into the roosting trees. Unlike the spectacle of Mexican Free-tailed Bats, the birds do not stream like smoke trails. Rather, they circle and swoop in bunches, not nearly as tight as Starlings, but still very impressive. Especially so as I realized that these were Purple Martins which I have only ever seen in small groups.

Single frame extracted from iPhone 5 movie
Single frame extracted from Canon 60Da movie
This short video clip does not do justice to the number of birds. Next time, I need to bring a wide-angle lens!

After dark, we moved up closer to the roost for a better view and were able to stand right next to the low trees. Wow, it was like a solid wall of birds - each new arrival trying to find a spot to roost was greeted by irate neighbors staking out their spot. The air was thick with the smell of droppings which covered the ground below.

Canon EF 100-400mm f/4.5-5.6L - 135mm, f/8, 1/100s, ISO-800, (Flash)
Canon EF 100-400mm f/4.5-5.6L - 400mm, f/16, 1/100s, ISO-800, (Flash)
I notice that some of the birds have orange mouths and some pink mouths. I have read that baby martins have bright orange mouths that serve as a beacon for the parents to drop food into in their dark nest cavities. I wonder if the orange-mouthed bird below is a juvenile.

Canon EF 100-400mm f/4.5-5.6L - 400mm, f/8, 1/100s, ISO-800, (Flash)

Canon EF 100-400mm f/4.5-5.6L - 285mm, f/16, 1/100s, ISO-800, (Flash)
Canon EF 100-400mm f/4.5-5.6L - 285mm, f/16, 1/100s, ISO-800, (Flash)
On the whole, an amazingly social bunch of birds to tolerate such close proximity. They eventually began to settled down for the night as we and the last of the spectators packed up around 9:30 PM.

Western Kingbirds Bickering in Flight

While waiting for the Purple Martin roosting event at the Highland Mall in Austin, I saw this pair of Western Kingbirds fighting their way across the parking lot. They remained in this relative position with the scruffy looking upper bird harassing the lower bird.

Canon EF 100-400mm f/4.5-5.6L - 250mm, f/7.1, 1/1600s, ISO-400
Canon EF 100-400mm f/4.5-5.6L - 250mm, f/7.1, 1/1600s, ISO-400
I am not positive of my identification, but settled on the Western Kingbird based on the yellow belly, pale gray head with lighter throat and, especially, the white edge on the tail.

Tuesday, July 1, 2014

Rock Wren at Lake Georgetown

This is the second time we have seen this bird just below the dam of Lake Georgetown. Though we are east of its normal zone, we are fairly certain that this is a Rock Wren based on appearance and call. Sibley shows our location as rare for this bird.

Canon SX-50 HS - 215mm, f/6.5, 1/320 sec, ISO-640

Canon SX-50 HS - 215mm, f/6.5, 1/320 sec, ISO-800