Question: Use of existing noise maps

[rainerschoedel]

I am currently learning photutils to benchmark it against StarFinder in Adaptive Optics images.

If I have already a noise map that provides me with the empirically estimated noise for each pixel of an image, is there an easy way to use it? Thanks.

[larrybradley]

@rainerschoedel The star finders in photutils have a threshold parameter, which defines the image value above which sources are detected. Typically, the threshold is defined relative to a background-only noise map, e.g., 3-sigma above the background. That will give you a threshold image, but most of the star finders require threshold to be a scalar float. So you will need to take a mean/median of your threshold image to get a threshold value. The find_peaks function (https://photutils.readthedocs.io/en/latest/api/photutils.detection.find_peaks.html#photutils.detection.find_peaks) is the only one where you can input a threshold image.

[rainerschoedel]

Thank you!

…

On 9. Feb 2022, at 17:15 Uhr, Larry Bradley ***@***.***> wrote: @rainerschoedel <https://github.com/rainerschoedel> The star finders in photutils have a threshold parameter, which defines the image value above which sources are detected. Typically, the threshold is defined relative to a background-only noise map, e.g., 3-sigma above the background. That will give you a threshold image, but most of the star finders require threshold to be a scalar float. So you will need to take a mean/median of your threshold image to get a threshold value. The find_peaks function (https://photutils.readthedocs.io/en/latest/api/photutils.detection.find_peaks.html#photutils.detection.find_peaks <https://photutils.readthedocs.io/en/latest/api/photutils.detection.find_peaks.html#photutils.detection.find_peaks>) is the only one where you can input a threshold image. — Reply to this email directly, view it on GitHub <#1284 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AFRDFOJ37ISPVCLM5CQOSQTU2KHKDANCNFSM5LZLDRSA>. Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. You are receiving this because you were mentioned.