Imaging Cadence for Exoplanets

Affiliation
American Association of Variable Star Observers (AAVSO)
Sun, 11/07/2021 - 19:21

Hi:

I'm about to start testing myself and my equipment for exoplanet work. So far in my reading and in going through the tutorials, I have not come across any guideline for determining how far apart to space the individual image captures. I'd appreciate any input on how to go about determining this.

I assume that the 'pre-transit' and 'post transit' 30-60 minute periods could have a pretty similar image spacing but it seems the 'transit entering', 'transit' and 'transit exiting' phases might want more frequent images - not sure.

Any help and suggestions would be welcome.

Cheers

Gary

Affiliation
American Association of Variable Star Observers (AAVSO)
Imaging Cadence for Exoplanets

Hi Gary,

Best practice would be to take as many image captures as possible, limited of course by the exposure time and download time of each image. Then, multiple data points can be "binned" if necessary by an analysis program such as AstroImageJ. The general practice then is to "bin" a number of images that constitute an equivalent cadence of 180 minutes.

Hope this helps,
Dennis

Affiliation
American Association of Variable Star Observers (AAVSO)
Binning Data Points

Thank you Dennis.

Ok, so, if we have 5 hours for the overall transit period and my exposures are 20 seconds each (hypothetical), I’d have nearly 900 images (less a few to account for the download time) for the entire transit - do I have that correct? Equally- spaced images throughout. 

Also, I understand binning pixels but is there somewhere that I can learn what it means to ‘bin’ data points and how to do that? 
thank you for your help!

Gary
 

Affiliation
American Association of Variable Star Observers (AAVSO)
Binning Data Points

Hi Gary,

Yes, to use your example, let's say download time is 10 seconds per image, this would imply a cadence of 30 seconds per image for each of 600 images. A program such as AstroImageJ then has an option for binning the differential photometry data for n observations (note; this is not pixel binning, but rather averaging of the differential photometry results of n images).

Dennis