Discovery — James Dunlop first observed
NGC 6752 from Parramatta, New South Wales, and included it as No. 295 in his catalogue of 1827 (
Dunlop 295). Today Parramatta (aboriginal for "eel-place") is a suburb of Sydney at the end of Sydney Harbour. He used a 9-inch F/12 telescope.
Why the Cartwheel Globular ? — It must be because of this...
NGC 6752 is the
4th brightest globular in the sky at magnitude +5.4, here's the pecking order if you're curious:
+3.7 ω Centauri (NGC 5139)
+4.0 47 Tucanae (NGC 104)
+5.1 M22 (NGC 5565)
+5.4 NGC 6752 +5.6 M4 (NGC 6121)
+5.6 M5 (NGC 5904)
+5.7 NGC 6397
+5.8 M13 (NGC 6205)
NGC 6752 is about 110 light-years across and 14,000 light-years distant. I haven't been there but my friends say the food's great and the locals are very friendly.
Why the weird exposure times on the R, G and B channels ? — Well, I equalised the fluxes on the channels using the full moon as a reference white. Really a waste of time and effort as I ended up using
PhotometricColorCalibration (PixInsight) anyway to merge the channels.
Two telescopes — The luminance data was taken with the bigger scope and ASI294MM Pro with 2x2 binning. Mixing scopes with different scales and cameras is a little tricky. Here the merged image scale is the native scale for the luminance capture.
The solitary background galaxy is
PGC 364450 at magnitude +16.72.
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