Sh2-274 Abell 21 Medusa Nebula

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Sh2-274 or Abell 21 or the Medusa Nebula is a planetary nebula – the gases expelled from a red giant star before it becomes a white dwarf, lit up by that star.  It’s located in the Milky Way, approximately 1930 light years away, and it has an apparent size of 10.25 arcminutes, making it 5.75 light years across.  Given the amount of time it would take to reach that size, it is considered to be an “ancient” planetary nebula.  

I find these small nebulae beautiful and fascinating. Each has its own unique structure.  This one has a Ha rim and an Oiii interior and has filaments (the filaments are probably the source of its nickname, the Medusa nebula).

In this image, the stars came from images using red-green-blue filters, and the nebula came from images using Hydrogen alpha (mapped to red) and Oxygen iii (mapped to blue) filters.  The nebula was processed separately from the stars to maximally enhance it.

I had hoped to get enough data on this one the last time we enjoyed the dark skies in Dell City, Texas, but there were a lot of high clouds that limited the amount of data I collected there.  So I collected more data from my driveway at home until I had almost 7 hours of Ha data and 6.7 hours of Oiii data.  

Camera geek info – Narrowband:

  • William Optics Zenith Star 73 III APO telescope
  • William Optics Flat 73A
  • ZWO 2” Electronic Filter Wheel
  • Antila HO and RGB filters
  • ZWO ASI183MM-Pro-Mono camera
  • ZWO ASiair Plus
  • iOptron CEM40
  • Friendswood, Texas Bortle 7-8 suburban skies
  • Dell City, Texas Bortle 2-3 dark skies

Frames:

  • January 24, 2025
    • 14 60 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
  • February 15, 2025
    • 100 30 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
    • 98 30 second Gain 150 Green lights
    • 30 0.02 second Gain 150 Green flats
    • 60 30 second Gain 150 Blue lights
    • 30 0.02 second Gain 150 Blue flats
  • February 20, 2025
    • 19 60 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
    • 5 60 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • February 21, 2025
    • 68 60 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
    • 30 60 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • February 22, 2025
    • 48 60 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
    • 32 60 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • April 7, 2025
    • 131 60 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • April 8, 2025
    • 130 60 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • April 10, 2025
    • 72 60 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • April 11, 2025
    • 133 60 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
  • April 12, 2025
    • 137 60 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
  • 30 Flat Darks from library
  • 30 Darks from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • NBColourMapper
  • Generalized Hyperbolic Stretch

Capturing Comet C/2025 F2 SWAN

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In late March 2025, a new comet, C/2025 F2, was found in imagery from the Solar Wind Anisotropies (SWAN) camera on the Solar and Heliospheric Observatory (SOHO). 

Orbit images Courtesy NASA/JPL-Caltech.

The Jet Propulsion Laboratory (JPL) has a great orbital dynamics viewer where you can see its orbit relative to the planets.  It’s quite fun to play with!  C/2025 F2’s orbit is very parabolic and nearly 90 degrees out of the ecliptic plane.  It is coming in from north of the ecliptic plane, will loop around the sun near Mercury’s orbit on May 1, 2025, and then head back out to the outer solar system south of the ecliptic plane.  So it’s visible from the Northern Hemisphere in the early morning now, but as it approaches the sun, it will get more and more difficult to spot, and it will be more visible from the Southern Hemisphere on its outgoing trajectory.

“Now” was the best time to see it from the Northern Hemisphere, and we have had a nice string of days with clear skies, so last weekend, it was time to go comet hunting!  

I used the JPL Horizons System to predict the comet location and motion so that I knew where to point my telescope and I knew how long the images could be without “smearing” the comet – 15 seconds for my telescope and camera combo.

I loaded up my gear, and my husband and I drove to our favorite early morning comet viewing site in Bacliff, Texas.  By the time I had everything set up, the comet was above the horizon.  My preprogrammed location contained a small, fuzzy object which looked like a comet on the first try!  I was really delighted that everything worked on the first try; this has not always been the case in the past.  I spent some (probably too much) time trying to get it positioned better in the frame and started imaging.  It was brighter in green than in red and blue which, with its fuzziness, confirmed to me that it was likely a comet.  I couldn’t see a tail in my single images.

I set up my regular camera to see if I could get some wider field images.  Given what I ended up with in the telescope images, I do not think the comet will be visible in the wider field images.

Both my husband and I tried to find the comet with binoculars, with no luck at all.  

We finished the morning with a lovely sunrise and breakfast.

Processing comets is still a big challenge for me, with more steps than processing a nebula.  I mostly follow the excellent process outlined by Adam Block in his Comet Academy.  Blinking through my frames, I could see the comet moving across the sky, another sure indicator that I had captured the right object!  After aligning, integrating, and stretching the comet images, I could see a faint tail that stretched all the way across the field of view (about 2 degrees with this telescope and camera combination), but the background noise was brighter than it was.  I tried several methods to make the tail visible, and the one that worked the best was to “murder the background” as Adam says in one of his videos.

I’m probably not going to get another chance to capture this one, but I enjoyed getting to see it at least once.  Has anyone else tried to go out and capture this one?

Camera geek info:

  • William Optics Zenith Star 73 III APO telescope
  • William Optics Flat 73A
  • ZWO 2” Electronic Filter Wheel
  • Antila RGB filters
  • ZWO ASI183MM-Pro-Mono camera
  • William Optics Uniguide 32MM F/3.75
  • ZWO ASI220MM-mini
  • ZWO ASiair Plus
  • iOptron CEM40
  • Bacliff, Texas Bortle 6 suburban skies

Frames:

  • April 12, 2025
    • 47 15 second Gain 150 Green lights
    • 30 0.02 second Gain 150 Green flats
    • 45 15 second Gain 150 Blue lights
    • 30 0.02 second Gain 150 Blue flats
    • 50 15 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
  • 30 Flat Darks from library
  • 30 Darks 

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Generalized Hyperbolic Stretch

M46, two Planetary Nebulas, and the Joy of Discovery

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Messier 46, also numbered New General Catalogue (NGC) 2437, is an open cluster, a cluster of about 500 stars that formed from the same molecular cloud and are similar in age, estimated to be 251.2 million years old.  M46 is located in the Milky Way, approximately 4930 light years away, and it has an apparent size of 25.3 arcmin, so it is approximately 36 light years across.  

I chose to photograph this open cluster not only because it is a Messier object I haven’t imaged yet but because there is a planetary nebula in front of it, so I was getting to image two objects at the same time. 

But when I processed the image and removed the stars, I got a surprise.  There wasn’t just one planetary nebula – there were two!  I was delighted and felt the joy of discovery.  I hadn’t known there was a second planetary nebula there, and yet there it was!  I immediately used PixInsight to annotate the image to see if the small planetary nebula was known, and of course it had already been discovered.  But it was still super fun to find something unexpected in my image.

The planetary nebula I had been intending to image, NGC 2438 or PK 231+04.2, is located in the Milky Way, approximately 1377 light years away, and it has an apparent size of 1.173 arc min, so it is approximately 0.5 light years across.  Because it had a different relative motion relative to us than M46, it is not considered to be part of the open cluster.  Before I learned that, I had thought it would be cool if it were part of the cluster and that possibly (since cluster stars are generally of similar age) multiple stars in the cluster could generate visible planetary nebula at the same time.  Wouldn’t that be a sight to see?

My surprise planetary nebula, Minkowski M1-18 or PK231+0.41, is located in the Milky way, approximately 14500 light years away, and it has an apparent size of 0.507 arcminutes, so it is approximately 2.1 light years across.  So further away and larger than NGC2438.

In this image, the stars came from images using red-green-blue filters, and the two nebulas came from images using Hydrogen alpha (mapped to red) and Oxygen iii (mapped to turquoise) filters.  The two nebulas were processed separately to maximally enhance each, which means that they are more equal in brightness in the image than they are in reality (M1-18 is much dimmer).

Have you felt the joy of discovery lately?

Camera geek info – Narrowband:

  • Williams Optics Zenith Star 73 III APO telescope
  • Williams Optics Flat 73A
  • ZWO 2” Electronic Filter Wheel
  • Antila SHO and RGB filters
  • ZWO ASI183MM-Pro-Mono camera
  • ZWO ASiair Plus
  • iOptron CEM40
  • Friendswood, Texas Bortle 7-8 suburban skies

Frames:

  • November 23, 2024
    • 135 60 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
  • December 19, 2024
    • 97 60 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • December 20, 2024
    • 89 60 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
  • December 31, 2024
    • 100 30 second Gain 150 Green lights
    • 30 0.02 second Gain 150 Green flats
    • 100 30 second Gain 150 Blue lights
    • 30 0.02 second Gain 150 Blue flats
    • 100 30 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
  • 30 Flat Darks from library
  • 30 Darks from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • NBColourMapper
  • Generalized Hyperbolic Stretch

NGC 2237: Rosette Nebula: Natural Palette vs SHO Palette

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The Rosette Nebula, also numbered New General Catalogue (NGC) 2237 or Caldwell 49, is an emission nebula.  It is a large star-forming region containing the NGC2244 (Caldwell 50) star cluster in its center.  The star cluster was made from the gases in the nebula and contains some massive type O stars, which in turn produce radiation and stellar wind that blow away and light up the nebula around them.  The stars in this cluster are young, less than 5 million years old.  The Rosette Nebula is located in the Milky Way, approximately 5200 light years away, and it has an apparent size of 1.3 degrees, so it is approximately 120 light years across.    

When we visit the lovely dark skies of Dell City, Texas, I try to collect data on some challenging objects that I don’t think I can do from my light-polluted driveway.  I’m not always successful in meeting the challenge (super dim objects take a lot of hours of data to image), so I also try to collect data on some brighter objects so I know I’ll come home with some nice images.  The Rosette Nebula was my choice for one of my “sure it will be nice” images from our last trip. 

I think it is a stunning nebula.  I processed the data using two different palettes, ending up with three different versions.  The first palette, a “natural” palette, maps H-alpha (which is red) to red, Sii (which is also red) to a more pink color, and Oiii (which is blue) to purple/blue.  I tried different weightings/emphasis of the colors and ended up with one version where the nebula center is more blue and one version where the nebula center is more purple.  The second palette, the “Hubble” palette or SHO palette, maps Sii to red, H-alpha to green, and Oiii to blue (and then cuts out most of the green).  I also tried different weightings/emphasis of the colors, and I ended up with one version I liked the best.  I like the colors in the “natural” palette, but I think the Hubble palette does a better job of showing off the details of the nebula.

Which version do you like the best?

Camera geek info – Narrowband:

  • Williams Optics Zenith Star 73 III APO telescope
  • Williams Optics Flat 73A
  • ZWO 2” Electronic Filter Wheel
  • Antila SHO and RGB filters
  • ZWO ASI183MM-Pro-Mono camera
  • ZWO ASiair Plus
  • iOptron CEM40
  • Dell City, Texas Bortle 2-3 dark skies

Frames:

  • October 9, 2024
    • 135 60 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • October 10, 2024
    • 129 60 second Gain 150 Ha lights
    • 30 0.2 second Gain 150 Ha flats
  • October 11, 2024
    • 27 60 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
    • 26 60 second Gain 150 Green lights
    • 30 0.02 second Gain 150 Green flats
    • 25 60 second Gain 150 Blue lights
    • 30 0.02 second Gain 150 Blue flats
  • October 12, 2024
    • 129 60 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • 30 Flat Darks from library
  • 30 Darks from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Generalized Hyperbolic Stretch

The Creation of NGC6888 the Crescent Nebula

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NGC6888, also called the Crescent Nebula, is an emission nebula around a Wolf-Rayet Star, WR136.  It’s located in the Milky Way, approximately 5000 light years away, and it has an apparent size of 18 x 12 arcminutes, making it 26 x 17.5 light years across.  It’s estimated to be 30,000 years old.

Although it may seem similar since it is a nebula around a star, the Crescent Nebula is not a planetary nebula, and its ultimate ending will be very different from a planetary nebula.  Planetary nebulae occur when an intermediate mass star, 1 to 8 solar masses, expands into a red giant, sheds its outer layer, and shrinks to a white dwarf.  The high temperature and wind from the white dwarf ionizes the shed outer layer, making the beautiful nebulae.  The Crescent Nebula was made by a massive star, estimated to initially be <= 50 solar masses.  When it was a main sequence star, fusing hydrogen early in its life, its solar wind blew a bubble in the gasses surrounding it.  When it became a Red Super Giant, its slow solar wind filled the bubble with its outer layer, estimated to be 25 solar masses worth of material. And when the star collapsed into a super hot Wolf-Rayet star, now about 21 solar masses in size, its fast solar wind compressed the red super giant and Wolf-Rayet material into ionized filaments and clumps.  Eventually, the Wolf-Rayet star will fuse its matter creating heavier and heavier elements until it reaches iron, when it will implode and create a supernova.  

Visually, the nebula appears to have an outer Oiii “skin” and a “clumpy” Ha interior.  The Oiii skin is the boundary between the main sequence bubble and the Wolf Rayet shell, and the clumpy Ha interior is the red super giant material compressed by the Wolf Rayet shell.  A “blowout” in the Oiii skin can be seen in the lower right in the blue Oiii in this image.  The Interstellar Medium (ISM) – the cold low density gas between stars – may have been less dense in this direction, allowing the Oiii skin to blow out in this direction and not in other directions where the ISM is denser.   

I used data from my driveway in Friendswood, Texas with suburban Bortle 7 – 8 brightness skies (lots of light pollution) to make this image.  In order to capture the detail in this nebula and the outer Oiii shell, I needed a lot of data: 12.4 hours of Ha data and 15 hours of Oiii data, plus an hour of RGB data for the stars, taken over ten nights.

This is a narrowband image, mapping Oiii to blue and Ha to red.  My goal was to capture both the details in the Ha and the outer Oiii shell. 

Some people think this looks like a cosmic “brain.”  What do you think?  Isn’t our galaxy beautiful?

Camera geek info – Narrowband:

  • Williams Optics Zenith Star 73 III APO telescope
  • Williams Optics Flat 73A
  • ZWO 2” Electronic Filter Wheel
  • Antila HO and RGB filters
  • ZWO ASI183MM-Pro-Mono camera
  • ZWO ASIair Plus
  • iOptron CEM40
  • Friendswood, Texas Bortle 7-8 suburban skies

Frames:

  • July 4, 2024
    • 104 60 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
  • August 2, 2024
    • 95 60 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • August 8, 2024
    • 215 60 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • September 7, 2024
    • 247 60 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • September 12, 2024
    • 237 60 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
  • September 13, 2024
    • 198 60 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • September 17, 2024
    • 133 60 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
  • September 19, 2024
    • 271 60 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
  • September 20, 2024
    • 143 60 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • September 21, 2024
    • 17 60 second Gain 150 red lights
    • 20 60 second Gain 150 green lights
    • 20 60 second Gain 150 blue lights
    • 30 0.05 second Gain 150 red flats
    • 30 0.02 second Gain 150 green flats
    • 30 0.02 second Gain 150 blue flats
  • 30 Flat Darks from library
  • 30 Darks from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Generalized Hyperbolic Stretch
  • NBColourMapper

Post-Solar-Swing Comet C/2023 A3 Tsuchinshan ATLAS 

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Comet C/2023 Tsuchinshan ATLAS looped around the sun on September 27, 2024 and started on its path back towards the outer solar system.  For a few days, it was not visible because it was too close to the sun.  But it was predicted to become visible again around October 11, and it would be the closest to the Earth on October 12, 2024. 

We were in Dell City at the time and staked out a sunset viewing spot with a long view to the west. 

We made our first attempt to see the comet on October 10, 2024.  The comet should have been barely above the horizon at sunset, and unless it was truly extraordinary, we were unlikely to be able to see it.  We were treated to a lovely sunset, but we could not spot the comet.  I had told myself this was a dry run, so I wasn’t too disappointed.  And, when we returned back to our B&B, we were treated to a rare viewing of the northern lights from Texas.

We made a second attempt to see the comet on October 11, 2024.  The comet was supposed to be higher above the horizon at sunset than the day before.  There were low clouds in the sky.  We saw a lot of “fake comets” – bright airplane contrails.  Eventually my husband found the comet with his binoculars – success!  I started taking pictures, but I hadn’t used the right settings, and when I discovered that later, I suspected that the data would not be usable.  I was right – I can see a moving smudge in the images, but it’s not good enough for PixInsight to comet align the images (and there aren’t enough stars in the images for it to star align them).

We made a third attempt – third time is the charm! – on October 12, 2024.  The comet was supposed to be more than 10 degrees above the horizon at sunset, and it had been the closest it would be to the Earth, 0.47239 AU or 70668538.14 km, just nine hours earlier.  This time there weren’t any clouds.  And this time we could easily find the comet and see that it had a huge tail!  Given my experience the night before, I made sure I was using good camera settings, and I could see the comet and its tail in single images.

I used PixInsight to stack 50 images (8.3 minutes of data) to make this final image – my first post-solar-swing image of C2023 A3.  Isn’t it beautiful?

Today, on this day of Thanksgiving, I am most thankful for my family and friends, near and far.  But I’m also thankful for all the wonder to be found in this universe we live in, and particularly for this comet.  Happy Thanksgiving!

Camera geek info:

  • Canon EOS 60D in manual mode, 4 second exposures, ISO 800
  • Canon EF 85 mm f/1.8 lens at f/11 manual focus at infinity
  • Intervalometer
  • Tripod
  • Dell City, Texas Bortle 2-3 dark skies

Frames:

  • October 12, 2024 
    • 50 10 second lights 
    • 31 0.01 second flats
    • 31 0.01 second flat darks
    • 30 10 second darks

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXterminator
  • NormalizedScaleGradient

Comet Hunting Tailgate Party: C/2023 A3 Tsuchinshan ATLAS from Dell City, Texas

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Our last visit to Dell City, Texas ended with a fun event: going comet hunting with new friends. 

I knew from comet hunting with my husband the previous evening that C/2023 A3 Tsuchinshan-ATLAS would be visible in the early evening sky.  But this time, I wanted to image it over the Cornudas Mountains to the west of town.  I also wanted to have a view over the flat fields to the mountains and the sky above – which I could find by driving just a few blocks north of the center of town.

I invited some new local friends to join us, and they came in a pickup truck loaded with lawn chairs.  It was a comet tailgate party!

We had a great time visiting while we watched the sky as Venus appeared, followed by some bright stars, followed by the comet.  We could see it naked eye!  We could even see the comet’s tail naked eye!  It was pretty impressive.

It’s taken me over a month to learn how to and successfully process these pictures.  Each picture used one set of images for the comet, stars, sky, and foreground/mountains, but each part was processed separately.  The earlier pink picture where the comet is higher in the sky was made from 120 4 second shots (8 minutes of data).  The later orange picture where the comet is lower in the sky was made from 75 10 second shots (12.5 minutes of data).

One of the things I tried to do while processing was to make sure that all the fuzz around the comet and the anti-tail were real and not processing artifacts.  You can use the sliders below to compare the final images with the comet-only portion to see that, if anything, the final images show less fuzz than what was in the data.  (The comet-only data was calibrated, blur exterminated, star exterminated, comet-aligned, stacked, dynamic background extracted, and stretched.)

Comet C/2023 A3 4 second Comet Only and Final images
Comet C/2023 A3 10 second Comet Only and Final images

This event is high on my list of “coolest astro things I’ve seen.”  And I’m glad I had such a great group of folks to share it with.

What cool things have you shared with friends recently?

Camera geek info:

  • Canon EOS 60D in manual mode, 4 second and 10 second exposures, ISO 800
  • Canon EF 85 mm f/1.8 lens at f/8, manual focus at infinity
  • Intervalometer
  • Tripod
  • Dell City, Texas Bortle 2-3 dark skies

Frames:

  • October 13, 2024 
    • 120 4 second lights for pink image with higher comet
    • 75 10 second lights for orange image with lower comet
    • 30 0.01 second flats
    • 30 0.01 second flat darks
    • 30 4 second darks
    • 30 10 second darks

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXterminator
  • NormalizedScaleGradient

Comet C/2023 A3 Tsuchinshan ATLAS with M5

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Comet C/2023 A3 Tsuchinshan ATLAS put on quite a show after it rounded the sun and passed by the Earth on its way likely out of our solar system.  With an orbital eccentricity greater than 1, its orbit appears to be hyperbolic, meaning it’s not coming back unless something perturbs its orbit.

In this picture, you can see the comet’s bright nucleus and coma, its long dust tail, and its anti-tail, but not a separate ion tail.

When comets travel close to the sun, solar radiation heats up the comet nucleus, and it outgasses. Outgassing delivers both gas and dust to the region around the nucleus, forming a coma, a (temporary) atmosphere around the comet.  The solar radiation and solar wind act on this coma to push the gas and dust away from the sun to form a tail.  Three separate tails can be visible: the ion tail, the dust tail, and the anti-tail. The ion tail, also called the gas tail or type I tail, is the tail formed by the ionized gasses pushed away from the comet, and it points away from the sun.  The dust tail, also called the type II tail, is the tail formed by the dust pushed away from the comet, and it stays more in the comet’s orbit and appears to curve away from the gas tail.  The anti-tail consists of the larger dust particles that were not pushed as much and remained in the comet’s orbit.  The anti-tail appears to point towards the sun, and it is only visible when the Earth passes through the comet’s orbital plane near the time when the comet passed by the sun.  Because of these special conditions to see the anti-tail, it is not observed with most comets.

Another item visible in the image is M5, a globular cluster in our galaxy.  It is the large bright “star” to the right of the comet nucleus.  Because this image was taken with an 85 mm lens, and M5 was sorted to the “stars” image in my processing, it just appears to be a large bright star.  I suspect with some additional processing, I could have made it look fuzzier, though there aren’t a lot of pixels at this scale.  The Messier objects are “fuzzy” objects that comet-hunter Charles Messier made a list of because they weren’t comets – so it’s fun to see one next to a comet.  M5 is 24,500 light years away from Earth and has an angular size of 23 arc-minutes, making it about 165 light years across.  It’s thought to be one of our galaxy’s older globular clusters, at 13 billion years old.

Processing this image was tricky for several reasons: 1) it was made from images taken with a camera on a tripod, so the sky was moving in each frame, 2) the comet was moving relative to the sky, and 3) the images were taken at dusk, when the sky gradient is also changing in every image.  I benefited greatly from following the methods and advice in Adam Block’s Comet Academy.  One additional trick I used was to run BlurXterminator in correction only mode on all the registered images as my first step since the 4 second tripod images had visible star trails. 

Getting to this image has taken almost a month of watching videos, learning new tools, and trying various tool combinations and settings.  Some of these steps had to be run on each individual image – all 233 of them – meaning some processing steps took many hours.  After all that work, I am happy with the results.

I started with this image because I thought it would be the easiest of my set of C2023A3 comet images to process … the other images are from darker skies in terms of light pollution but closer to dusk and include a foreground.  But the comet was brighter!  I’m really looking forward to processing them and sharing the result!  Hopefully they won’t take a month each to process!

Camera geek info:

  • Canon EOS 60D in manual mode, 4 second exposures, ISO 1600
  • Canon EF 85 mm f/1.8 lens, manual focus at infinity
  • Intervalometer
  • Tripod
  • Pearland, Texas Bortle 7-8 dark skies

Frames:

  • October 15, 2024
    • 233 4 second lights
    • 30 0.0025 second flats
    • 30 0.0025 second darks

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXterminator
  • StarNet2
  • NormalizedScaleGradient

M31 Andromeda Galaxy Astrophotography Learning Curve

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The first object that I got a satisfactory image of with my tracking mount and telescope and DSLR was M31, the Andromeda Galaxy, from the dark skies of Dell City, Texas in October 2022.  My first image, above, was a 3 minute long exposure.  I was so excited to have a good image that I took a picture of my camera’s viewfinder to send the picture to people.  

When I came home to Friendswood, Texas, I did some experiments to see if I could get the same results.  It was not a surprise when the answer was “no” – my home skies are much more light polluted – I expected to get a completely white screen and was surprised when I could still see a hint of the galaxy.

I started to learn how to use PixInsight, a powerhouse astrophotography processing tool, in the winter of 2022.  I learned enough to be able to stack 18 3 minute images to make my Christmas card photo and the picture I am still using as my computer background at work.

I’ve learned a more about astrophotography processing since then, most notably adding Russ Croman’s excellent BlurXterminator, NoiseXterminator, and StarXterminator tools to my toolbox and learning a ton from Adam Block’s videos.  So I reprocessed the data above using my current knowledge and toolset.

Finally, in October 2024, we were back in Dell City, and I collected new M31 data using an astrocamera and red, blue, green and hydrogen-alpha filters.  I had to learn more in order to be able to merge the Ha data into the RGB data.  Luckily, there are Adam Block’s videos!  One new trick I had to use was “continuum subtraction” – removing the background red from the stars from the Ha data.  

Sometimes, when other things aren’t working out (comet processing), it’s good to step back and see how far you’ve come. I’ve learned a lot over two years … and I’m looking forward to learning a lot more!

What are you learning about?