Tuesday, March 11, 2014

Clear Last Night

High thin clouds have dominated the sky over the past several weeks, with only a few instances of moderate clarity.

Last night was the first night since I started this project where I both knew what I was doing AND it was clear.  A few high clouds drifted past very quickly during the early part of the session, but other than that it was a very productive evening with a lot of new Jupiter data.

I also got what appears to be some great star data for my consistency testing.  Last week I decided on 20 Orionis as my test target, but when I got started last night I decided that I really needed a star I could actually see in my very primitive 1x "guidescope".  I noticed a faint little star just below Aldeberan, so I pointed the scope at it.  To my surprise, it was a very nice "binary" star.  It turned out to be Theta 1 and Theta 2 Tauri, visual magnitudes 3.84 and 3.4 respectively.  Even with a 0.1 second exposure, the max values were very near saturation, but they seemed to stay within those bounds and the better signal-to-noise I have, the more stable (hopefully)  the photometry is gonna be.

Hopefully either later today or tomorrow I'll calibrate the data and run it through my photometry code to get some numbers.  For now, just a picture:

Figure 1: Theta 1 Tau & Theta 2 Tau, 11 Mar 2014 03:38:34 UTC
This set of data also allows me to better calibrate my pixel scale.  These two stars are 5.62 arc minutes apart, or 337.2 arc seconds apart.  I measured the pixel distance between these two as 129.096 pixels.  That gives me a pixel scale of 2.612 arcsec / pixel.

Ah Jupiter

Last night for the first time I was able to get data for Io.  It was at maximum elongation from Jupiter and just appeared to hang in the same place the entire four hour session I collected data.  Callisto was too close to Jupiter to likely get any decent data.  Europa and Ganymede were on the other side of Jupiter very well spaced apart and far from the planet.  I should get some excellent data from them.

Again, for now, just a picture:

Figure 2: The Jupiter system as seen from Earth 11 Mar 2014 05:15:42 UTC
In total, I have 1600 Jupiter images from last night.  I'm hoping that I got at least a 50% observing efficiency.  So that means about 800 images of good data.  That's a huge amount and I'm very excited to run it through my photometry code to see how the numbers look.  I'm optimistic.

The forecast is still saying partly cloudy tonight, but then a run of clear nights starting Wednesday (13 Mar 2014 UTC) and running at least through Sunday (17 Mar 2014 UTC).  Whew -- so that means I could potentially be seeing a LOT of data and quite a few number of late nights.  Jupiter is pretty much too low to make any reasonable observations after about 08:00 UTC at my location, so that's not too bad.

Circular Aperture Photometry

I now have the software written to do circular aperture photometry and my preliminary look at the 27 Mar 2014 data improves the photometry -- at least by my eyes.  I need to run the numbers to see how consistent they are.  I also need to run this code with the data from 12 and 19 Feb 2014 to see if those values will improve.  Very exciting.

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