Got APOD-lucky with this image!

Please click the "Original" thumbnail on the right to bring up the actual image in full resolution.

This image of the south-western end of the Andromeda Galaxy features the giant star cloud NGC 206, right of centre, and spans about 30' on a side, at a plate scale of 0.47”/pixel. It combines just over 47 hours of exposures in my CDK24, with about 15 hours in luminance, 16 hours in Ha (3nm-narrowband), and 16 hours in RGB filters. The data were collected over the course of 18 nights from the end of August through to the middle of October of 2022. I actually devoted almost 82 hours of telescope time to get this image, but applied a fairly aggressive set of cuts in order to select subs of higher quality, including strong cuts on the FWHM of the star-disk profiles, especially in the luminance channel. My goal was to try to get the sharpest possible final image, while still integrating enough to get a deep image with rich colours.

Selecting Revision "J" will bring up the image annotated with labels for 64 objects in this region of M31 that I identified as representatives of seven different astrophysical categories: red, yellow, and blue supergiant stars, globular clusters, Cepheid variable stars, supernova remnants, and planetary nebulae. More information on these objects is given below, including links to their SIMBAD database listings. Motivated by the rich panoply of objects in this image, I've (shamelessly!) borrowed my title from the spectacular "Panchromatic Hubble Andromeda Treasury" (PHAT), published in 2015, which covered about 1/3 of the Galaxy (in the other direction), and resolved over 100 million stars. 

I originally posted the image as processed using conventional deconvolution, which was before Russell Croman's amazing BlurXTerminator (BXT) became available, and I later reposted the image after redoing the processing with BXT: the result with BXT is now labelled as the "Original" version. BXT produced a significant increase in resolution, even though I used fairly modest settings, and for comparison, I've included the image with conventional decon (all other processing steps the same) as Revision "K".

On the order of 100,000 stars in this region of M31 have been individually resolved (with many more just below the resolution threshold), including outside of the brightest part of the disk. This is supported by a detailed comparison with another HST image that covers the same end of the galaxy, and that used Halpha data taken with the 4m Mayall Telescope at Kitt Peak; the faintest resolved stars in my image clearly match stars in the Hubble image throughout the field (in all of the many small regions that I compared in detail), while the pattern of fine granularity in my image, caused by stars that are below the resolution threshold, also closely follows the more finely-resolved stars in the Hubble image. Furthermore, I estimated the limiting magnitude of well-resolved stars at about 24 (based on rough photometric comparisons with several red supergiant stars), which is about the apparent magnitude of red giant stars at the distance of M31. This is consistent with being able to resolve a very large number of very faint stars, especially in the yellow central regions of the galaxy, where red giant stars are tightly packed, resulting in the much denser granularity in those parts of the image.

To identify some representative examples of other astrophysical treasures that are resolved in this image, I rifled through large catalogues of seven distinct object categories, selecting from among the brightest members of each: 18 supergiant stars of the three colour types, 15 Cepheid variables, 17 globular clusters, 6 supernova remnants, and 8 planetary nebulae (many more objects of each type are plainly resolved, but this seemed like more than enough labels!).

Each object is listed below with a link to its SIMBAD entry, and each of the category headers contains a link to a paper on the corresponding catalogue. Objects in each category are numbered sequentially in order of increasing RA (which runs from bottom-to-top in this image). The magnitude range of the displayed objects in each category is given, except for the supernova remnants.

Red Supergiants (Visual magnitudes mV ranging from 17.9 to 19.3)
R1, R2, R3, R4, R5

Yellow Supergiants (mV: 16.7-18.2)
Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8

Blue Supergiants (mV: 17.0-18.1)
B1, B2, B3, B4, B5

Globular Clusters (mV: 14.2-17.5)
This list includes many examples of blue globular clusters (extragalactic globulars have a wide range of characteristics, including bi-modal red/blue colour distributions, and are the subject of intensive investigations). 
G1, G2, G3, G4, G5, G6, G7, G8, G9, G10, G11, G12, G13, G14, G15, G16, G17

Cepheid Variable Stars (period-averaged mV range: 19.5-20.6)
This list is taken from one of several seminal papers on Cepheid variables in M31 published  by Walter Baade and Henrietta Swope in the early 1960s.
C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15

Supernova Remnants
Note that a pair of dashes is used to bracket the physical extent of each remnant, based on SIMBAD values for their major/minor axes (which happen to be about equal in this set).
S1, S2, S3, S4, S5, S6

Planetary Nebulae (mV: 19.7-21.0)
P1, P2, P3, P4, P5, P6, P7, P8

Side note about M31 Cepheids: Several years ago I ran a fairly ambitious student project, at my university's observatory, which measured the light curves of 17 Cepheids (on the other side of M31 relative to the image above). We used the light curves to determine the distance to the galaxy, with an estimated uncertainty of only 10%, and in agreement with the accepted value. The study was published in the Journal of the Royal Astronomical Society of Canada, and a PDF of the article is available here (the PDF opens with the cover and table of contents of that journal issue, followed by the article).