HI Polare70,
As you might be aware this is both the technique I employed *and* the object I worked on recently.
(See the M5 APOD
https://apod.nasa.gov/apod/ap190509.html by me from a few days ago)
Another good (I think even better example) of M15 is shown below.
Typically as stars near saturation they tend to lose their nice PSFs (this is especially true for ABG cameras where they become non-linear near the top end).
This becomes an issue when (perhaps) later applying HDRMT on the final combined image after HDRComposition.
So even if stars are not entirely saturated, HDRComposition can still be nice. Just specify a threshold considerably beneath the actual saturation value.
One of the keys is to have really short exposures, for the short data set, since you are just taking care of the absolute brightest offenders in the image- especially in the core of the cluster.
The 60 second exposure is OK...but I suspect even half of that might even be good- but it depends on what values you are getting for the stars (which depends on the camera, filter, telescope...etc etc).
One quick tip if you go down this road is to deconvolve the two images (the combined long and combined short) *before* doing HDRComposition. Trying to do deconvolution on an HDRComposition result is really asking for problems.
-adam
