How does MaximDL calculate centroids?

Discussion in 'General' started by Don, Aug 1, 2017.

  1. Don

    Don Standard User

    Joined:
    Nov 16, 2015
    Messages:
    22
    I am writing a technical paper, and would like to clarify the calculations that MaximDL uses to report centroid values. The Information window suggests it is a simple moment (center of gravity), but the FWHM fits a curve. Does the centroid calculation use only pixels values and distances, or is there some curve fitting, too? The centroids appear very good, even better than some other programs that do fit curves, so maybe MaximDL uses some hybrid. I don't need to know the details, I just want to finish my paper with the correct interpretation.

    Thanks,
    Don Bruns
     
  2. Doug

    Doug Staff Member

    Joined:
    Sep 25, 2014
    Messages:
    6,269
    It uses a simple moment. The trick to getting a good measurement is an appropriate choice of threshold level, and rejecting pixels that are in the noise floor.

    FWHM does use a fitted Gaussian, but the calculation is independent of the centroid calculation.
     
  3. Don

    Don Standard User

    Joined:
    Nov 16, 2015
    Messages:
    22
    Thanks Doug. I'll edit my paper.
     
  4. Bob Denny

    Bob Denny Cyanogen Customer

    Joined:
    Oct 12, 2014
    Messages:
    746
    Location:
    DC-3 Dreams, SP, Mesa, Arizona +1 480 396 9700
    Make sure you're referring to Aperture mode in MaxIm. If it is Astrometric then you are relying on PinPoint's detection and centroid algorithms (there are 3 available plus Sextractor behind the scenes).
     
  5. Don

    Don Standard User

    Joined:
    Nov 16, 2015
    Messages:
    22
    Hi Bob,

    Yes, Aperture mode. I am also referring to Visual Pinpoint in the paper, as well as Astrometrica. The other two programs I tried did not work nearly as well as these three.

    Don
     
  6. Bob Denny

    Bob Denny Cyanogen Customer

    Joined:
    Oct 12, 2014
    Messages:
    746
    Location:
    DC-3 Dreams, SP, Mesa, Arizona +1 480 396 9700
    Ok just making sure, since the same three centroid methods available in visual pinpoint are also available in MaxIm

    And hi Don! Best wishes on your awesome project!
     

Share This Page