M33, Triangulum Galaxy

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Jared Willson Senior Member • Posts: 1,363
M33, Triangulum Galaxy

After lots of internal debate on what to do with my private observatory, I reached the difficult decision that I would close it down and move my telescope to a remote, hosted location. I just got tired of having to disassemble and re-assemble every year with fire season. The observatory in Napa and been threatened by fire eight of the last twelve years, and actually burned down once.

So, I drove the telescope to Deep Sky West in New Mexico last week and put everything together. Thank goodness, it all worked properly.

Here is my first LRGB image taken from New Mexico...

About the Object

The often overlooked Triangulum Galaxy is the second nearest spiral galaxy to our own Milky Way after the more famous Andromeda galaxy. It lies at a distance of roughly 3.1 million light years in the constellation, you guessed it, Triangulum. It is generally considered the most distant object routinely visible to the naked eye, though it requires very dark skies to see it. It is thought to be a satellite galaxy to Andromeda. M33 was one of the first "spiral nebulae" (now known to be spiral galaxies) identified by Lord Rosse in 1850.

In the upper portion of the galaxy in this image note the prominent, red star forming region. This HII region (ionized Hydrogen) is one of the largest known. It spans a whopping 1,500 light years. It is similar in structure, though much larger than, the famous Orion Nebula in our own Milky Way.

M33 is approximately 60,000 light years across which makes it about half the diameter of the Milky Way. In terms of mass, it's roughly one tenth the size of the Milky Way and contains approximately forty billion stars. Unlike many spiral galaxies, there is no central "bulge" with a heavy concentration of stars. The nucleus of the galaxy is an HII region--ionized hydrogen--that includes a ultra luminous x-ray source that is the strongest in our local group of galaxies. If there is a black hole at the center of M33, it is not as massive as most. Estimates put the upper limit at 3,000 solar masses.

About the Image

This image was captured using a 305mm diameter Riccardi-Honders reflecting telescope. This is a relatively fast astrograph at f/3.7 (1,124mm focal length) and it has a well corrected, flat field with a 50mm imaging circle.

The telescope was mounted on an Astro-Physics AP1100GTO AE mount. This mount is unusual in that it has absolute encoders that can determine where the mount is pointed physically to extremely high precision. When combined with a solid pointing model for the night sky (which takes into account things like flex of the optical tube under gravity, lack of orthogonality of the two axes, imperfections in polar alignment, atmospheric refraction, etc..), the mount can track to an accuracy of 1/20,000th of a degree over the duration of a typical sub exposure without the need for guiding.

The camera used was a QHY600 Pro cooled, monochrome camera. Separate exposures were taken through 50mm square red, green, blue, and luminance (clear) filters to allow the creation of a true color image. The camera was cooled to -10*C in order to reduce thermal noise in the image. The QHY600 contains the same sensor as a Sonly A7RIV mirrorless camera, just without the Bayer filter array.

The image consists of 170 separate 3 minute exposures stacked on top of each other in an effort to improve signal to noise ratio. Four hours of luminance and one and a half hours each of red, green, and blue data were combined. The software used to control the equipment was NINA (Nighttime Imaging 'N' Astronomy). APCC was used to build and enable the mount's tracking model. All calibration and post processing was performed in PixInsight.

M33, Triangulum Galaxy

Thanks for looking!

 Jared Willson's gear list:Jared Willson's gear list
Leica Q2 Leica SL2 Hasselblad X1D II 50C Leica SL 90-280mm F2.8–4 Hasselblad XCD 30mm F3.5 +8 more
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