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DAWN LUNAR ECLIPSE IN CANBERRA - A TWILIGHT TRIFECTA

Total Lunar Eclipse, pre-dawn hours Saturday July 28th

Joseph Cali

The eclipse
In the Eastern Australian time zone, the penumbral eclipse began at 3:15am local, and the partial eclipse began at 4:24am Saturday morning. Totality started at 5:30 am which coincided by a few minutes with the beginning of the darkest part of twilight called astronomical twilight. The totally eclipsed moon faded into the brightening twilight over the next 93 minutes. On Saturday morning in Canberra, sunrise, moonset and the end of totality all coincidentally occur within about 10 minutes of each other between 7:02am and 7:13am. I wondered if, at sunrise/moonset, the still totally eclipsed Moon would be visible with brightening skies, atmospheric extinction all taking their toll, though this is difficult to predict.  I have seen one eclipse similar to this in 2011.  It was a beautiful sight as the orange eclipsed Moon contrasted with the brightening blue sky.   The temperature on Saturday was -2C. In the dark, your body radiates a lot more heat to the sky so I wore a freezer suit that I use for cold weather observing that kept me very comfortable for the 2.5 hrs I was out.

This diagram shows the relationship between altitude and azimuth of the eclipse, contact times and twilights.  





Weather Forecasts
This week, weather prediction models were very unstable all week indicating their forecasts are unreliable. In the Canberra region, I find that the ACCESS model works best east and south of the ACT, averaging predictions of GFS and ACCESS works best directly over the ACT, and the European model 50-100km  northwest of the ACT where my dark site is located. On Tuesday, the prediction was for clear weather . On Wednesday cloud models were predicting a complete cloud out, and Thursday, the prediction was for clear weather in the southern ACT and cloudy in the north. By Friday night the forecast was again looking good as were the skies.  I skipped the penumbral eclipse and stayed in bed until 10 mins before the partial eclipse began. It takes about 8 mins to drive to the lookout. 

I decided to avoid the crowds on Mt Stromlo and go to a secluded location. I observed from near Shepherds Lookout NW Belconnen, ACT, at the junction of the Molonglo and Murrumbidgee Rivers and about 5 mins drive from my home. Location : 35°14'58.2"S 148°58'21.4"E   Perfect clear weather, -2C temperature.

At these temperatures, the river valley often forms fogs in winter.  I took the risk of being fogged out for the chance of getting foreground river valley fog in my night-scape image.  My gamble paid off and I'm really pleased with this nightscape taken just minutes after the beginning of astronomical twilight with my Pentax K5 and wide angle lens. I set the camera to shoot 10 stop auto brackets driven by an intervalometer.  I didn't need to touch the camera.




I took more nightscapes during subsequent stages of twilight. My experience was like that of many other photographers, the lighting became progressively more difficult as the eclipse and twilight progressed.

I also shot a telephoto sequence with a Pentax K1 and Pentax DA* EDIF 300mm ƒ4. I was using a fixed tripod and so ISO's were kept high to maintain the shutter speed shorter than 0.8s so that Earth rotation did not blur the image. I have roughly pegged magnitude limits using Starry Night Pro for my own records.
 






This camera image just managed to capture totality in the civil twilight sky.  The Moon slipped behind the Brindabella Mountains just after this image was taken 20 mins before time of Moonset for an ideal horizon and 18 minutes before sunrise.



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