OBSERVER’S CHALLENGE* – JUNE, 2021
by Glenn Chaple
NGC 5746 – Edge-on Barred Spiral Galaxy in Virgo (Mag: 10.3, Size: 7.4’ X 1.4’)
Telescope aperture is a major factor in determining how difficult each monthly Observer’s Challenge is. Under dark-sky conditions, our June Challenge - the 10th magnitude edge-on barred spiral NGC 5746 in Virgo - would be an ultimate test for a common 2.4-inch (60mm) refractor and a piece of cake in a 10-inch (254mm) reflector.
When considering the difficulty of any Observer’s Challenge, you also need to factor in the ease with which it’s located - particularly if you find your way by star-hopping. In this case, NGC 5746 is quite accommodating. It’s just 20 arc-minutes (1/3 degree) west and slightly north of the 4th magnitude star 109 Virginis.
NGC 5746 is a classic example of an edge-on spiral or barred spiral galaxy. It’s comparable in visual splendor to the better-known Messier 104 (the Sombrero Galaxy), NGC 4565 (the Needle Galaxy), and NGC 891 (the Silver Sliver Galaxy). In Stoyan and Schurig’s Interstellarum Deep Sky Atlas, NGC 5746 is labeled as the “Mini Sombrero Galaxy,” All of these edge-ons are bisected by a distinctive dust lane, which appears particularly stunning in deep sky images.
When I viewed NGC 5746 with a 10-inch f/5 reflector at 139X under magnitude 5 suburban skies, it appeared as an elongated 2- to 3-arc-minute-long streak oriented roughly north-northwest to east-southeast. There was no sign of the galaxy’s dust lane. Knowing exactly where to look and resorting to averted vision, I was able to glimpse NGC 5746 with a 4.5-inch f/8 reflector.
NGC 5746 was discovered by William Herschel February 24, 1786. Some 95 million light years away, this huge galaxy spans 160,000 light years.
*The purpose of the Observer’s Challenge is to encourage the pursuit of visual observing. It is open to anyone who is interested. If you’d like to contribute notes, drawings, or photographs, we’d be happy to include them in our monthly summary. Submit your observing notes, sketches, and/or images to Roger Ivester (firstname.lastname@example.org). To find out more about the Observer’s Challenge, log on to rogerivester.com/category/observers-challenge-reports-complete,
NGC 5746 Finder Charts
AAVSO Variable Star Plotter (VSP) Stars to magnitude 14.5. One degree field, North is up
NGC 5746 Images/Sketches
Image by Mario Motta, MD (ATMoB) 32-inch f/6.5 telescope with ZWO ASI6200 camera, 3 hours - 1 hour each Red, Blue, Green. Processed CCD stack, pixinsight, and touch up photoshop. North is up.
(above) NGC 5746, as seen with 10-inch f/5 reflector at 139X under magnitude 5 skies. 0.6° field, South i
(below) For comparison - portion of above sketch showing same area as in Mario Motta’s image.