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My first exoplanet observation!


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That's a little optimistic I think. What is preventing the error bars getting smaller and the number of data points getting larger - exposure time ?. 

A great effort nevertheless

What do you think contributes to the underlying variation - detector noise or sky variations? 

Very interested.

Regs

Mike

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Thanks everyone, Its my first attempt and I hope I can look back on this one in a year or so and know what I was doing wrong. It sure is tricky, the depth of the magnitude drop is only 0.0135 mag.

if anyone has any advice as to how I can improve I'd much appreciate it.

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What do you think contributes to the underlying variation - detector noise or sky variations? 

This is a good question and I need to figure it out to improve the data collection before I can submit it. All the data was captured remotely too which adds to the challenge :-)

The main factors causing the noise were (I believe)

  1. Constant focus changes
    1. The capture system was configured to capture 1min exposures continuously and only focus if the HFR was above a threshold (1.2pixels). However for some reason it decided to focus after every frame! This caused focus variations. I threw away any frames with poor focus and found that including these made the data much worse.
  2. Poor tracking. 
    1. Related to above. During focus, guiding is suspended and I only set a 10sec delay after focus. Once focus is finished it needs to get the guide star back in track but the exposure may have already started by then. Again, any frames with bad tracking were dumped.
  3. Exposure time.
    1. 60sec exposures were used. For this 13.7 mag star this resulted in a peak of about 7000 which is a bit on the low side but still in the linear range. I think a longer exposure may be better.
  4. Calibration
    1. I used darks that were 1 month old. Currently working on automating capture of darks to happen straight after the schedule is finished.
  5. Filter
    1. I used a Luminance filter. I'm not sure if this is the correct one and reading up on it I'm still not sure. Maybe a red filter could be better?

Its unfortunate about the focus and tracking. It was a perfectly timed event, the airmass was never above 1.1 for the entire capture.

 

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 What is the basis of the error bars, from the photometry software? 

They were added automatically and I dont yet understand how they are derived. Currently studying this :-)

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Given the star is relatively bright, I'd try turning off focusing to average out the noise and even de-focus slightly as long as diffraction spikes don't suck the phone out of the disk. It won't affect the photometry as long as all the star is in the measurement radius.

Mike

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Thanks for the suggestions. I'll try the no-focus approach although my SCT suffers from focus drift due to temp changes. Maybe less frequent focus.

Will also play with moving average. Maybe there is better data buried in there somewhere :-)

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Congratulations! This is very interesting and fascinating. Noisy data, may be, but look at what you have done! Recall that this was an impossible task for an amateur barely a few years ago. Well done!

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On 17/12/2016 at 21:12, Cinco Sauces said:

Congratulations! This is very interesting and fascinating. Noisy data, may be, but look at what you have done! Recall that this was an impossible task for an amateur barely a few years ago. Well done!

An impossible task for the professionals a few decades ago!

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