M95 - First Light Remote Observatory
M95 Galaxy - Click here for full resolution
Messier 95 is a barred spiral galaxy about 33 million light-years away in the zodiac constellation Leo. It was discovered by Pierre Méchain in 1781, and catalogued by compatriot Charles Messier four days later. The galaxy has a morphological classification of SB(r)b, with the SBb notation indicating it is a barred spiral with arms that are intermediate on the scale from tightly to loosely wound, and an "(r)" meaning an inner ring surrounds the bar. The latter is a ring-shaped, circumnuclear star-forming region with a diameter of approximately 2,000 light-years. The spiral structure extends outward from the ring. A Type II supernova, designated as SN 2012aw, was discovered in M95 in 2012. M95 is one of several galaxies within the M96 Group, a group of galaxies in the constellation Leo, the other Messier objects of which are M96 and M105.
source: Wikipedia
NGC/IC:
Other Names:
Object:
Constellation:
R.A.:
Dec:
Transit date:
Transit Alt:
NGC 3351
n.a.
Galaxy
Leo
10h 43m 58s
+11º 42.2’
20 Mar
65º S
Conditions
M95 is a typical spring galaxy with best visibility around March to April. This was the first target imaged from the Remote Observatory at IC Astronomy in Spain. The sky here is around bortle2, and weather conditions were pretty good during the sessions where the images were taken. After around 04:00h it would get below the 30° altitude and not really worth imaging anymore. There was quite some experimentation going on with the equipment, so data from the first two sessions were not used.
Equipment
With this being the first image taken from the remote observatory, this was also the first time this rig was used in its full configuration. Earlier, components have been used during testing and earlier imaging, but now everything was working together. A somewhat smaller galaxy like M95 is an ideal target for the long focal length of the Planewave CDK14. In combination with the full-frame Moravian C3-61000 Pro, the Field of View was very generous to frame this target. Also this was the first time that the acquisition software Voyager was used in some all-night imaging. For this image no dragscript automations were used. The on-the-fly menu with an imaging sequence worked well for some mainly manual runs.
Telescope
Mount
Camera
Filters
Guiding
Accessoires
Software
Planewave CDK14, Optec Gemini Rotating focuser
10Micron GM2000HPS, custom pier
Moravian C3-61000 Pro, cooled to -10 ºC
Chroma 2” LRGB unmounted, Moravian filterwheel “L”, 7-position
Unguided
Compulab Tensor I-22, Windows 11, Dragonfly, Pegasus Ultimate Powerbox v2
Voyager Advanced, Viking, Mountwizzard4, Astroplanner, PixInsight 1.8.9-2
Imaging
There has been quite the debates recently on forums discussing the benefits of LRGB vs RGB imaging. Typically I would use LRGB imaging for a broadband image, but I have to say that in recent images the luminance did not seem to add a whole lot more detail to the image. So for imaging at this dark site, with a large aperture, I decided to give RGB imaging a go. During the first two sessions an exposure of 180s was used. But in looking at the images, it appeared that there was a lot more headroom for even the brightest stars before they would show any sign of clipping, so I decided to increase to 300s, which overall gave a better image. The very small pixel-scale (0.3 arcsec/px) might be contributing to the fact that it appears hard to really blow any highlights out.
The overall field of view was a bit too large for this relatively small target, so I decided to apply a small crop in the shown at the top. The full resolution version though contains the complete field of view of the full-frame image. Having changed from 180s to 300s basically meant that quite a bit of data was not used. Overall only about 9h of exposure time made it to the final image.
Resolution
Focal length
Pixel size
Resolution
Field of View
Image center
9576 × 6388 px (61.2 MP)
2563 mm @ f/7.2
3.8 µm
0.30 arcsec/px
45' 8.8" x 31' 4.2"
RA: 160.9913676354
Dec: 11.70446858836
Processing
All images were calibrated using Darks (50), registered and integrated using the WeightedBatchPreProcessing (WBPP) script in PixInsight to R, G, B images. At this point the flat panel had not been installed yet, and no flat-calibration was performed. The individual colour channels were combined to give the first RGB image
GraXpert was used to remove gradients from the RGB image. With no flat calibration it was a bit of a question how this would work out, but the results were very good. At this point I also noticed that GraXpert seems to be doing a first colour calibration as well. The usual green background that remains with linked-stretching is largely gone after GraXpert processing. Unfortunately there was no way I could plate solve the image using ImageSolver in PixInsight. This process can be a bit tricky to use from time to time, but usually with some tweaking of parameters it is possible to solve the image. No matter what I tried, I never could get image solver to work on this image. Therefore instead of the now common SPCC, the traditional Colour Calibration method was used with regions of interest defined for the white reference (center of the frame with the galaxy) and the background. BlurXTerminator (BXT) did a great job with deconvolution. Besides tightening the stars, especially the structure of the galaxy showed some impressive details after BXT had been applied. Somehow my impression of BXT is that it enhances smaller pixel-scale images more than large pixel-scale images. And that the latter can get quite a bit better with drizzling (lowering the pixel-scale). Stretching was done in a couple of mild steps using GHS.
The overall quality of the image was very nice, with beautiful star shapes and colours all the way into the far corners. And lots of detail everywhere. It was a pleasure scrolling around the image and start looking for dozens of little galaxies dotted around the area. For example, see some beautiful little gems in the top left corner with nice detail and color:
Some beautiful little gems tucked away in the corner
And they have a proper PGC catalogue number too.
The image was very malleable and responded very good to processing. There was quite some headroom in dynamic range between the galaxy signal and the background. So for the most part all good news. The only part that is still confusing is the shape of the brighter stars. Besides the typical 4 diffraction spikes, it looks like there are some in-between spikes in them as well. In preparation of this rig I had read about the shroud bending in too much and causing such in-between spikes. For that reason shroud spreaders were added, but these in-between spikes are still there. I’ve checked the optical path, but can’t think of anything that could cause this. If anyone has an idea where these in-between spikes come from, I would love to hear about it. If possible I’d like to get rid of them.
Most brighter stars have in-between spikes, besides the regular pattern of four spikes. Unclear what is causing this. The shroud is being pushed to the side using shroud spreaders especially designed for this telescope.
To finish the processing, the non-linear image already looked pretty good, but adding some saturation and contrast helped to make the image pop a bit more. And finally NoiseXTerminator was used to iron out the mild noise that was visible in the background. The galaxy was a bit lost in the full-frame image, so cropping in to a slightly smaller field of view helped to focus on the galaxy a bit more. And BackgroundNeutralization was used to make the background a bit more similar to all the other images.
Processing workflow (click to enlarge)
This image has been published on Astrobin and has received Top Pick nomination.
