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Some Asteroid photometry and animation

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#1 Lukey

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Posted 17 April 2021 - 10:42 AM

Had a very interesting session doing some photometry on asteroids last night.

 

You can usually observe their rotation by a dip in the magnitude over a period of time. The more irregular ones show the greatest fluctuation. I noticed that asteroid 1727 Mette is well-placed in Serpens and has a fast rotation of about 3 hours, and I managed to capture 5 hours-worth of images. It's just a small object about 5-8 km in diameter and is a Mars-crosser asteroid, orbiting every 2.52 years.

 

Here is a light curve I prepared using data from the photometry program Muniwin. It's derived from 100 x 3 minute exposures, binned 2x captured with an Atik383L+, Omegon RC cam.

Once Muniwin had processed the data it came up with this strikingly obvious rotation curve, with its magnitude ranging by about 0.35 magnitudes over a period of 3 hours, matching the official rotational data with a peak at around 23:37 and another at 2:32. As usual with asteroid magnitude curves, there are two peaks and troughs per rotation. There are a few binary asteroids, like Antiope, which behave like eclipsing binaries when lined up correctly, so I hope to capture that some time. Times are British Summer Time (1 hour ahead of UT)

 

51121647210_2660f0f982_h.jpg

 

 

Here's a capture of the whole field, with the position of Mette at 22:24 and 2:57 highlighted. Based on two 5 x 3 minute exposures. The brightest star here is magnitude 7.8 and the field of view is 38.5 x 29 arc minutes.

 

51121647200_1b74f3f1b6_h.jpg

 

 

And here's an animation of 9 cropped frames over the session, 15 minutes apart

 

51120856686_91da0e85d8_o.gif


Edited by Lukey, 18 April 2021 - 06:40 AM.

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#2 moxican

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Posted 17 April 2021 - 11:36 AM

That is fantastic. What scope did you use?


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#3 Lukey

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Posted 17 April 2021 - 11:39 AM

That is fantastic. What scope did you use?

Thanks! It’s an 8” f/8 Ritchey-Chretien.


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#4 Aquat0ne

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Posted 17 April 2021 - 04:55 PM

Great stuff. Love the animation too.
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#5 jlecomte

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Posted 17 April 2021 - 06:54 PM

Hi, what software did you use to generate the light curve? I dabbled in AstroImageJ, but it seems to have a hard time with moving targets like asteroids. Thanks!


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#6 Lukey

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Posted 18 April 2021 - 03:37 AM

Hi, what software did you use to generate the light curve? I dabbled in AstroImageJ, but it seems to have a hard time with moving targets like asteroids. Thanks!

The data to analyse the photometry was a program called Muniwin, but the light curve was done using Excel.  Muniwin can export the photometric data as a text file, which I imported into Excel and played around with the graphs. Muniwin creates a light curve too, so you don’t need to go to that bother, but I like the flexibility and varieties of graphs available in Excel. 


Edited by Lukey, 18 April 2021 - 03:39 AM.


#7 BinaryField

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Posted 19 April 2021 - 01:38 PM

Hi, what software did you use to generate the light curve? I dabbled in AstroImageJ, but it seems to have a hard time with moving targets like asteroids. Thanks!

I'm not sure if you're aware of this, but there are some special instructions to use AIJ with moving objects. I've experimented with it only a little bit myself, but it seemed to work for me.

 

http://astroimagej.1...ield-td240.html


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