M65 - Leo Triplet
Leo Triplet: M65, M66 and NGC3628 - Click here for full resolution image.
M65 (R.A.: 11h 20m 01.13s, Dec: +12º 58’ 44.4”) is a galaxy in the constellation Leo at a distance of 43 million lightyears from Earth. Nearby galaxies are M66 and NGC3628 and the three together are often referred to as the Leo Triplet. All three galaxies have more or less similar visual magnitude of about 8.9-9.3 and can be easily seen with a modest telescope.
M65 is highly inclined, tilted about 14º from edge-on to our line of sight. Neighbouring galaxy M66 is seen more heads-on and is classified as an SAB(s)b spiral galaxy, indicating its deformed elliptical nature with bright bulge in the core. In fact, its deformed nature resulted in the galaxy being included in the Halton Arp Atlas of Peculiar Galaxies as Arp 16. M66 is the brightest of the three galaxies.
NGC3628 is the faintest of the three galaxies and is seen completely edge-on. Its orientation with the marked dust-lane through the center has given it the nickname hamburger galaxy. With an apparent dimension of 14 x 4 arcmin, it is the largest of the three.
All three galaxies are not only visibly close together. There galactic distances are relatively short and they have interacted significantly over time. The many deformations in the spiral arms and dust clouds are indications of that. In NGC3628 the gas rotates in opposite direction from the stars, probably also related to galactic encounters.
Sky Plot (click to enlarge)
5º FoV + scope display (click to enlarge)
Planning
The Leo Triplet is a typical object for ‘Galaxy Season’, or late winter, early spring. During the months of March and April the galaxies are well above the southern horizon for significant parts of the night. Each galaxy in itself is worth a picture, but they are relatively small and would require quite some magnification power. The three galaxies together make for an exciting composition that can be nicely captured within a Field of View of around one degree. During the planned observation, the moon was low or even absent for most of the night.
Visibility charts showing altitude at 22:00h throughout the year (left) and throughout the session on April 5, 2018 (right).
Conditions
All images were taken from the backyard in Groningen, The Netherlands (53.18, 6.54), during one session on April 5, 2018. Even though it was already April, temperatures were just above the freezing point. Humidity was fairly high being in the low 90’s.
This was the very first night out with a dedicated astrocamera, an auto-focuser and accompanying telescope-mounted headless computer. All this new equipment meant a lot of getting used to, but it turned out easier than originally anticipated
Capturing
The image was captured using the Takahashi TOA-130 in combination with the ASI1609MM-Pro camera. The Field of View of about 1 arcmin was ideal for a target like the Leo Triplet. Little attention was paid to field rotation and/or framing. As long as all three galaxies were in the frame, it was considered sufficient.
Like for a typical galaxy, exposures were made using Red, Green, Blue and Luminance broadband filters. With no experience on best exposure times, exposure was just set to 60s per frame, with the gain set at ‘unity gain’, or in the case of this camera 139. Exposure could probably have been a bit longer, but 60s turned out ok.
Technical Details
Telescope
Mount
Camera
Filters
Accessoires
Software
Takahashi TOA-130 + 35 flattener, Sesto Senso
10Micron GM1000HPS, Berlebach Planet
ZWO ASI1600MM Pro, cooled to -30 ºC
Astrodon 1.25” LRGB Gen2 E-series mounted, ZWO EFW 8-position
Fitlet2 (Linux Mint 18.04)
KStars/Ekos, INDI Library, SkySafari, PixInsight
Frames
The image was captured using Astrodon 1.25” Gen3 E-series True balance LRGB filters. No correction was made in exposure time between RGB and L images to compensate for the more limited bandwidth of the RGB filters. Also no balance was applied between the combined RGB and L time. Below are the frames listed taken in each session that made it to the final image.
Image
This was the first image taken with a dedicated astrocamera. A total exposure of 1.1h. For a first image a great success. Compared to later images a pretty short overall exposure.
After processing the image and a little crop to straighten the edges, the final image has a resolution of 4656 x 3520 pixels, or 16.4 Megapixels. It covers a field of view of 1.01 degrees horizontally. The rotation was 55 degrees, meaning north is pointing to the top-right.
Annotated image showing other deep sky objects, stars brighter than mag. 11 and the image’s orientation.
Processing
This being one of the first images taken, not much was recorded on the overall processing workflow. Bias, Dark and Flat frames were recorded and used for calibration of individual frames. After calibration and stacking, processing was performed mostly along the lines of what was described in the book ‘Inside PixInsight’ by Warren Keller.
This image has not been published on Astrobin.
