M33 - Triangulum Galaxy in Ha and Ha-RC (Red Continuum)
Ha / Ha-RC

M33 in H-Alpha (mouse-over to see Red Continuum subtracted image, click on image for full resolution)


M33 in H-Alpha minus Red Continuum (mouse-over to see HII regions labels, click on image for full resolution)


NGC 604

NGC 604 Theberge Observatory(full resolution 1.15 arc-second/pixel) vs Hubble Reference

Apparent dimension: 1.93' x 1.2'



This H-Alpha image of the Messier 33 or Triangulum Galaxy highlights the numerous HII regions of this galaxy. Most noticeable is NGC 604 on the upper left which is M33's largest and brightest HII region. The Ha image is the result of a total of 6 hours of imaging aimed at capturing the H-Alpha emission light of this galaxy.

The H-Alpha minus Red Continuum image is the result of subtracting the RedContinuum image resulting from 2.5 hours of imaging (10 x 15 minutes) M33 at a wavelength of 645 nm, from the H-Alpha image taken at a wavelength of 656 nm. This subtraction was done in Photoshop using "Difference" as layer combine mode, and a curve to adjust the subtraction.

The last image is a crop of NGC 604 in H-Alpha with the Hubble version next to it as a reference to identify the features visible.


Imaging Session

  • Date: November 21, 23 and 25, 2011
  • Target Coordinates (J2000) : RA = 01h 33m 54s, Dec = +30:39:00 (J2000)
  • Exposure: H-Alpha: 24 frames x 15 minutes/frame, Red Continuum: 10 x 15 minutes/frame, all unbinned at -20C
  • Camera: SBIG ST-10XME with AstroDon H-Alpha (656 nm x 6nm) and Red Continuum (645 nm x 5 nm) filters
  • Equipment: Takahashi FS-152 f/8 on Takahashi NJP mount
  • Guiding: external guidescope MiniBorg 60mm f5.4 and Meade DSI Pro unbinned
  • Observatory control and automation software: CCD Commander V1.6, Maxim DL V4, FocusMax V3.4
  • Location: Theberge Remote Observatory, Robosky, Orangeville, Ontario

M33 HII Regions Catalogue (ref: "An Optical Study of M33" by J. Boulesteix et al., Astronomy and Astrophysics, vol 37, 33-48, 1974)

The table below provides a detailed catalogue of over 369 distinct HII regions that have been compiled by J. Boulestix and his colleagues. Note that only those HII regions within the field of view of my imaging rig are shown in the mouseover image above.

  • Column 1: Reference number for each HII region
  • Column 2: Intensity ranging from 1 (faint) to 4 (extremely strong) on a logartihm scale
  • Column 3: Reference number in Aller's catalogue (1950)
  • Column 4: Reference number in the thermal radio continuum catalogue by Isreael and van der Kruit (1974)
  • Column 5 and 6: RA and Declination (1950 coordinates)
  • Column 7 and 8: Position in the galactic plan
  • Column 9: Apparent size in arc-seconds

M33 HII Regions Catalog part 1

M33 HII Regions Catalog Part 2



© All images on this site are copyright Serge Théberge