M67, Colin McGill

M67

M67, Colin McGill

M67

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Description

M67, old open cluster in Cancer.

Had some fun constructing the Herzsprung-Russell diagram. Also loaded the HR diagram from Johnson and Sandage (1955) - Ap.J. 121, pp 616-627, for comparison.

For those of you who have asked how this is done:

I used the FWHMEccentricity tool in PixInsight on each of the master R, G and B images. This tool has the option to produce a CSV file containing the parameters for a Moffat fit to each star: x and y location, X size, Y size, rotation angle, amplitude and background.

I found the definition of a Moffat function in the PixInsight documentation (the Dynamic PSF tool), then used Wolfram Alpha to integrate the expression over X and Y to get the total flux from the star For Beta = 4, the standard fit, turns out its A * (Sigma X * Sigma Y) * Pi/3.

With this, I then created an index for each star based on its location: i+NX * j to allow me to match up stars from each colour.

I used ImageSolver to get the exact co-ordinates of the frames and AnnotateImage to label the Tycho stars in the image. I found one that wasn't saturated and looked up its magnitudes in Vizier.

From there, I just used Excel to plot the data.

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M67, Colin McGill