The Deer Lick Group and Stephan’s Quintet
NGC 7331, also known as Caldwell 30, is an unbarred spiral galaxy about 40 million light-years away in the constellation Pegasus. NGC 7331 is the brightest galaxy in the field of a visual grouping known as the Deer Lick Group. The other members of the group, NGC 7335, 7336, 7337 and 7340, lie far in the background at distances of approximately 300–350 million light years. The galaxy appears similar in size and structure to the Milky Way, and is sometimes referred to as "the Milky Way's twin". However, they differ, as unlike the Milky Way, the central bulge in NGC 7331 is rotating in the opposite direction to the rest of the disk.
The five galaxies of Stephan's Quintet are also known as the Hickson Compact Group 92 (HCG 92). Although called a "quintet," only four of the galaxies are truly close together and caught up in a cosmic dance. The fifth and leftmost galaxy, called NGC 7320, is well in the foreground compared with the other four. NGC 7320 resides 40 million light-years from Earth, while the other four galaxies (NGC 7317, NGC 7318A, NGC 7318B, and NGC 7319) are about 290 million light-years away.
October 25, 2025
I’m really getting into the swing of things with the AT115EDT. To keep testing it, I decided to spend some decent integration time on NGC 7331 (and a couple hours on M33 at the end of each night… I’m going to see how much time I can accumulate on M33 this season.) I’ve had 3 good nights of generally good to excellent guiding (generally .5” RMS and lower), and I was able to collect about 10 hours with the Astronomic L-3 for overall signal, and about 6 hours with the Triband Filter for color (maybe I should just switch to mono!). I was nervous about a meridian flip without a pier extension, but I simply stop guiding with 8 mins until the meridian and wait until 8 mins after the meridian to flip and that has worked fine. This target in particular has the camera right down near the tripod leg before and after a flip (maybe only 2 inches or so from it with 8 minutes to go to the meridian). I don’t think it would actually make contact under my normal meridian flip settings (with 5 mins before and after the meridian), but I’d rather be safe than sorry!
Once again, I have found it hard to push color (saturation and chrominance) with only a UV-IR cut filter, so collecting some Triband data and blending the two images 50/50 in pixel math helped quite a bit with that. I tried ratios of 65/35 and 35/65 UV-IR/Triband, and the 65/35 blend gave me a bit more of some faint IFN and faint signal on the edges of the galaxies, but less color, while 35/65 gave me more color, but less of the faint IFN and faint signal around the edges of the galaxies, so I felt that 50/50 was the best mix.
Technical Details
Imaging Telescope: Astro-Tech AT115EDT
Imaging Camera: ZWO ASI533MC Pro
Mount: Sky-Watcher EQ6-R Pro
Filter: Astronomik L-3 Luminance UV/IR Block 2", Antlia Triband RGB Ultra Filter 2”
Accessories: Antlia OAG and Filter Drawer Assembly, Astro-Tech AT115EDT .8X Reducer, ZWO ASIAIR Plus, ZWO EAF
Software: StarNet, PixInsight, BlurXTerminator, NoiseXTerminator, SetiAstro Star Stretch, SetiAstro Statistical Stretch, Siril, ZWO ASIAIR
Guiding Camera: ZWO ASI174MM
Imaging Dates: October 19, 21 and 24, 2025
Frames (gain 101.0) f/4.9 -10c: 200x180” UV/IR (10h), and 120x180” (6h) Triband
Integration Time: 16h
Darks/Flats/Dark Flats: 30/30/30
Bortle Dark-Sky Scale: 5.00
September 26, 2024
Part two of first light with the new telescope. I’m really excited about the new scope as it has opened up a whole new world of more distant targets to chase, due to the longer focal length. This galaxy would have been nothing more that a small smudge on my RedCat, so I’m excited to be able to resolve more details of more distant targets! That said, this target clearly needs much more exposure time, as there’s quite a bit of noise within the galaxy itself. I went light with noise removal on the galaxy to try to preserve details, but it’s clear some more imaging time will be necessary to reduce the noise.
Technical Details
Imaging Telescope: Orion Optics IDEAL 8
Imaging Camera: ZWO ASI533MC Pro
Mount: Sky-Watcher EQ6-R Pro
Filter: Antlia Tri-band RGB Ultra Filter - 2” Mounted
Accessories: ZWO ASIAIR Plus, ZWO EAF
Software: PixInsight, Photoshop, NoiseXterminator, Starnet, BlurXterminator
Guiding Telescope: SVBony SV106 60mm Guide Scope
Guiding Camera: ZWO ASI174MM
Imaging Dates: Sep. 24, 2024
Frames (gain 101.0) f/4.9 -10c: 60x180” (3h)
Integration Time: 3h
Darks/Flats/Dark Flats: 30/30/30
Bortle Dark-Sky Scale: 5.00