Thursday, June 18, 2020

made a plan

Environment Canada painted a downward picture. It looked like the weather was getting volatile. Probably classic summer conditions, hot in the day, stormy in the afternoon. The other astronomy weather tools were not very good either. No rows and rows of blue like a few days ago.

Still, I was optimistic. And the idea of doing some science was in my brain. I looked closely at the sky assessments after midnight for Friday and Saturday. The after-midnight rule-of-thumb...

Reviewed some of the numbers, imaging with the C8 and the 40D. 

I found that a separation of 14" was no trouble. And I remembered that I had the 2x, the PowerMate, suggesting that I could get to 7". Without the doubler, I saw that the field was around 35' in width. 

I wondered about the faintest visible objects. I found in a 20 second exposure I could see magnitude 12.1, 11.9, and 12.0 stars. I checked the airmass for a particular shot. Whoa: 4.6! I had lost 2 magnitudes! So mag 14 was possible. [ed: Later I recalled the general rule that a camera adds 1 to 2 magnitudes and the C8 theoretical limit is 14; so maybe 16 is possible?]

Reviewed the Washington Double Star database (at Georgia State). Found HJ 2799, an entry that is almost 200 years old! Wow. ST3P showed this as a single, HD 142979. 15". Good, doable. Oh oh, with a mag 18 companion. Not at candidate for the backyard; maybe BGO?

Wasn't finding a lot of good "neglected" candidates... So I considered the unmarked doubles I had seen near recently viewed targets. Briefly I ruminated on T Cyg but then I settled on pairs near Pallas. A check of the position looked rather good! The area would be at an elevation of about 55 degrees at 1:00 AM and would reach the meridian at 3 AM. There were lots of known doubles in the area that I could use for calibration. And, again, the weather looked decent overall after 1. And it looked like I could capture over two nights, good for improved data quality.

Reviewed my workflow notes for double star measurement with a DSLR...

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