Galaxy M33 in Triangulum

Object Details:

Designation: Messier 33, NGC 598      Constellation: Triangulum
Visual magnitude:   +5.8                        Apparent size: 62′  x 36′
Diameter:   50,000 light years.             Distance:  2,800,000  light years

The Triangulum Galaxy (M33) is an unbarred pinwheel type galaxy which sits about 15° from the Andromeda Galaxy (M31).

At magnitude 5.8, M33 is technically a naked eye object in a perfect dark sky – which is something I am never likely to experience. I certainly would not see it from here in SW Sydney, looking through the murk and light pollution of Greater Sydney to my north.

Here’s a daytime telephoto picture, looking towards Sydney from The Australian Botanic Garden, which is situated between my home and the observing site I use with Macarthur Astronomical Society. Sydney is about 40 km away and Sydney Harbour Bridge is the arch at far left:


Sydney glows a lot at night – but I digress.

M33 is the third largest galaxy in the Local Group, after M31 and the Milky Way. It is closer to M31 than it is to the Milky Way and I understand it to be interacting with M31. It is possibly even a satellite of it and the two may well eventually merge. Hard to tell, I would have thought, because everything in astronomy happens really slowly – but professional astronomers are so darned clever they seem to be able to figure hard stuff out.

The number of stars in the four largest galaxies of the Local Group are estimated as :

Andromeda Galaxy: 1 trillion.
Milky Way: up to 400 billion.
Triangulum: 40 billion.
Large Magellanic Cloud: 30 billion.

I didn’t know that.

An interesting  list of all the known galactic bodies in the Local Group (not including globular clusters) can be found  >here<, which is where I pinched this fascinating pictogram of the objects in the Local Group:


Also in the field of view according to this annotated overlay:
NGC 588, NGC 592, NGC 595,
NGC 603, NGC 604, IC 132, IC 133, IC 134, IC 135, IC 136, IC 137, IC 139, IC 140, IC 142, IC 143.

Technical Details:

Image & Processing:

Date:  2019-10-23.
Exposure:  43 x 143 sec   = 100 min.
Gain:  210 > 230 > 250.

Location:  outer suburban
Conditions:  clear sky, no Moon
Sky brightness:   0.24 e/pixel/sec . 

Image acquisition:  SharpCap.
Method: Live stacked.
Darks: 6x

Image post-processing:  GIMP.
Cropping: yes.


Telescope: SkyWatcher Esprit  Type: 120 triplet refractor
Focal: 840 mm F/7 Mount: SkyWatcher EQ6-R Pro
Camera: ZWO ASI 071 MC Pro
Type: CMOS 28.4mm 16 Mpx
Optical aids: Flattener: Y; filter: LP Guiding: Yes
Polar aligning: QHYCCD PoleMaster Polar Error: 3′ 45”

Geek Log, for my records:

[ZWO ASI071MC Pro]
Debayer Preview=On
Output Format=PNG files (*.png)
Capture Area=4944×3284
Colour Space=RAW16
Hardware Binning=Off
Turbo USB=40
Frame Rate Limit=8 fps
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=53
Cooler Power=49
Target Temperature=-10
Auto Exp Max Gain=300
Auto Exp Max Exp M S=30000

Auto Exp Target Brightness=100
Mono Bin=Off
Anti Dew Heater=On
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=C:\Users\Roger\Desktop\SharpCap Captures\darks\ZWO ASI071MC Pro\RAW16@4944×3284\143.3s\gain_210\dark_6_frames_-10.0C_2019-10-23T10_03_19.fits
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1

Images © Roger Powell

2018-03-10 Telescope & Roger


    1. Thanks for reading, glad you liked the link. Whilst always treating Wikipedia cautiously, its numerous astronomy pages are generally well written and factual.


    1. Thanks Paul.

      I agree but even more astonishing is the ability of scientists to extract information embedded in that ancient light – chemical content, redshift, wavelength, polarisation etc.

      Liked by 2 people

  1. Good results for being on the southern hemisphere and under light pollution. Even here, at latitude 60N, with M33 culminating at 60 degrees altitude, it is a very difficult visual object if the sky is not dark. From a dark place though, it is a wonderful experience to see its fuzzy patch with the naked eye.

    Liked by 1 person

    1. Thanks for your comment Hernán. I would love to spend a whole night imaging this object from a truly dark sky – and picking it out visually as well. At this time of year here in Sydney the viewing time available is not very long.


    1. Thanks for the links, Jim. Some nice images from the 20″ SCT, you are fortunate to have the opportunity to use it. I’ve been trained (twice!) to use our local WSU telescope (16″ SCT) but have never been offered the opportunity to actually use it….

      Liked by 1 person

  2. As always these are so informative, thank you. On another note, are you in danger from the fires near Sydney that I am reading about?


    1. Thank you for asking, Fran.

      Yes, there are scores of bushfires burning in Queensland, Western Australia and in particular my home State of New South Wales. Fortunately none in my vicinity but here in the Greater Sydney Region we were warned of “Catastrophic Fire Danger” today. We are already in a “Drought Emergency”, so we will have a difficult summer ahead.

      What is really frightening is that our bushfires are becoming more frequent and are higher in intensity – but our political leaders continue to dismiss the reality of Climate Change. 🥺

      Liked by 1 person

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