Comet C/2025 A6 Comet Lemmon on November 2, 2025 with the Fred Hartman Bridge

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Comet C/2025 A6 Comet Lemmon was an excuse to do something I’ve been wanting to do for a long time: go watch the sun set over the Fred Hartman Bridge in Baytown, Texas.  The Fred Hartman Bridge is a gorgeous, yellow, cable-stayed bridge that I always enjoy driving over when I get the chance.  

I had hoped that the bridge would make a great foreground for a comet picture.

We got to our viewing spot early so we could also enjoy the sunset, which did line up beautifully with the bridge.  I met a nice couple there who were also watching the sunset, and I enjoyed chatting with them.

Unfortunately for my comet and star viewing plans, looking west over the bridge is also looking straight into a bunch of brightly lit refineries.  (There is apparently no collective noun for refineries, but I think there should be one.  How about a process of refineries?  Other suggestions?)

So that evening, I could not spot the comet and could barely spot even the brightest stars.  I took a bunch of pictures anyway, but even when it was fully dark, I was limited to 2 second long images.  I did not have much hope that I would be able to generate a picture with visible stars, much less a visible comet.

So I let other astro processing take priority.  

When I finally got around to processing these images, I started with the last 100 frames, and, to my surprise and delight, I could see the comet!  So then I went back and processed all 553 frames of 2 second data, 403 of which (13.4 minutes of data) were usable.  I processed the comet separately from the stars to get as much of it as possible.  Then I overlaid the stars and comet over a single image of the bridge at night and a single image of the bridge at sunset.  

Which do you like better?

Camera geek info stars and night image:

  • Canon EOS 60D in manual mode set 2 second exposure, ISO 800
  • Sigma 24-70 mm f/2.8EX lens, set at f/5.6, 24 mm, manual focus for stars and night version
  • Tripod
  • Intervalometer 

Camera geek info Sunset:

  • Canon EOS 60D in manual mode set 4 second exposure, ISO 100
  • Sigma 24-70 mm f/2.8EX lens, set at f/9, 24 mm, manual focus for stars and night version
  • Tripod
  • Intervalometer 

Frames:

  • November 2, 2025
    • 1 4 second light for sunset
    • 403 2 second lights for stars and comet
    • 31 1/1250 second flats
    • 33 1/2500 second darks from library
    • 57 1 second darks from library

Sh2-206 or NGC1491: The Fossil Footprint Nebula (or, alternately, The Signature Nebula)

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Sharpless Sh2-206, also listed as New General Catalogue (NGC) 1491, is commonly called the Fossil Footprint Nebula.  The portion of the nebula in this image is the “heel” of the footprint; the toes are much dimmer and not in this image.  To me, the most obvious feature of the nebula is the bright scribble that looks like a signature.  So I’d call it the Signature Nebula.  What do you think?

Sh2-206 is an H II region emission nebula, a region of ionized atomic hydrogen.  The H II regions in the Sharpless 2 catalog were “defined not only in terms of the ionized gas but also in terms of the hot stars which are responsible for the ionization.”

Sh2-206 seems to be associated with one bright star: BD +50 886, which is the bright star just under the “signature” in the nebula.  This star is a type O4 star, young, massive, and hot.  It is approximately 9590 +/- 1000 light years away, which is close to the 9850 light years +/- 2000 light years distance for the nebula itself.  BD +50 886 is considered a runaway star with a 2D peculiar velocity (velocity relative to its environment) of 30.5 +/- 3.9 km/sec.  Not only is it ionizing the gas around it to make this nebula, but the “signature” in the nebula may be a bow shock due to the radiation pressure from the star on the local gas and the relative motion of the star and the local gas.

Sh2-206 is located in the Milky Way, approximately 9850 light years away.  The nebula in this image is 25 arc minutes across, so the nebula in this image is approximately 71 light years across.  

In this image, the stars came from images using red (0.47 hours), green (0.29 hours), and blue (0.3 hours) filters, and the nebula came from images using Sulfer ii (6.5 hours of data mapped to red), Hydrogen alpha (1.5 hours of data mapped to green) and Oxygen iii (7.67 hours of data mapped to blue) filters, the standard SHO mapping.  The nebula was processed separately from the stars to maximally enhance it.

Camera geek info:

  • William Optics Pleiades 111 telescope
  • ZWO 2” Electronic Filter Wheel
  • Antila SHO and RGB filters
  • Blue Fireball 360° Camera Angle Adjuster/Rotator
  • ZWO ASI183MM-Pro-Mono camera
  • William Optics Uniguide 32MM F/3.75
  • ZWO ASI220MM-mini
  • ZWO ASiair Plus
  • iOptron CEM40
  • Friendswood, Texas Bortle 7-8 suburban skies

Frames:

  • December 30, 2025
    • 9 600 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
  • December 31, 2025
    • 15 600 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • January 2, 2026
    • 15 600 second Gain 150 Sii lights
    • 30 0.5 second Gain 150 Sii flats
  • January 3, 2026
    • 15 600 second Gain 150 Sii lights
    • 30 0.5 second Gain 150 Sii flats
  • January 31, 2026
    • 9 600 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • February 6, 2026
    • 9 600 second Gain 150 Sii lights
    • 30 0.5 second Gain 150 Sii flats
  • February 21, 2026
    • 84 20 second Gain 150 Red lights
    • 30 0.02 second Gain 150 Red flats
    • 53 20 second Gain 150 Green lights
    • 30 0.01 second Gain 150 Green flats
    • 54 20 second Gain 150 Blue lights
    • 30 0.01 second Gain 150 Blue flats
  • February 28, 2026
    • 2 600 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • March 12, 2026
    • 8 600 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • March 13, 2026
    • 12 600 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • 30 Flat Darks matching flat durations from library
  • 30 Darks matching light durations from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Narrowband Normalization
  • Image Blend

M33 The Triangulum Galaxy and its H-II Regions

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Messier 33, the Triangulum Galaxy, is a galaxy in the same local group as our own Milky Way.  M33 is located approximately 2.74 million light years away, and it has an apparent visual size of 60.26 by 35.48 arcmin, so it is approximately 48 by 28.3 thousand light years across.  It is classed as a flocculant (fluffy, with less well-defined arms) spiral galaxy – in this image, one set of arms curve up from the right side and a second set of arms curve down from the left side.  

Because, by galaxy standards, M33 is relatively nearby (in the same local group as our own galaxy), we can see a lot of detail in it.  In fact, we can see the same kind of things in it that we see in our own galaxy – Hydrogen II (H-II) star forming region nebulas, supernova remnants, and even planetary nebulas.  

Most obvious in this image and in the black-and-white Hydrogen alpha (H-alpha) image are the enormous, bright, young H-II star forming region nebulas.  These are all clouds of atomic hydrogen ionized and lit up by the young, massive, star clusters that formed within them.

The brightest H-II star forming region in M33 is NGC604 in the innermost arm to the lower left of the main image.  It has an apparent visual size of 2 by 1.2 arcmins, so it is approximately 1600 by 950 light years across.  This region contains 200 massive, young, hot O-type and Wolf-Rayet stars that are about 3 million years old as well as an older population of stars that are 12 million years old.  This region may have hosted a sequence of star forming events, where one set of stars forming triggered the formation of the next set.  

The second brightest H-II star forming region in M33 is NGC595 at the top left of the galaxy core.  It has an apparent visual size of 1 arcmin, so it is approximately 800 light years across.  It contains about 250 type OB stars and 10 Wolf-Rayet stars with an approximate age of 4.5 million years old.

The third brightest H-II star forming region in M33 is NGC588 in the top of the second arm to the right.  It has an apparent visual size of 30 by 50 arcseconds, so it is approximately 400 by 665 light years across.  It contains a young star cluster that is about 3.5 million years old.

I started working on collecting data on M33 at the end of 2024/start of 2025 using my smaller 73 mm “Z” telescope, but I did not end up with sufficient data for a good image.  When I was imaging Comet Lemon with “Z” last fall, I collected more data while I was using that telescope and finally collected enough.

I combined several paths of processing to make this image.  I used only the 30 second Red Green Blue (RGB) data (about 26 minutes per color) to generate the RGB stars.  I used all the RGB data (4.5 hours of red data and 2.6 hours each of green and blue data) to generate an RGB image of the galaxy.  I processed the Hydrogen alpha (H-alpha) data (8.3 hours of data) by continuum subtracting a starless red from the starless H-alpha, then processing and stretching the resulting image.  I processed the Oxygen iii (Oiii) data (6.6 hours of data) by continuum subtracting a starless blue from the starless Oiii data and then processing and stretching the resulting image.  The continuum subtraction removes the “starlight” from the broader-band stars from the H-alpha (or Oiii) data to leave just the H-alpha (or Oiii) sources.  I stretched the H-alpha and Oiii separately to retain some detail in the very bright H-alpha emissions from the NGC604 H-II region as well as detail in the RGB galaxy.  Finally, I used NBColourMapper to add the H-alpha as red and the Oxygen iii as turquoise to the RGB galaxy.  

It is amazing to me that we can see star forming regions in other galaxies.  Our universe is still under construction!

Camera geek info:

  • 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
  • William Optics Uniguide 32MM F/3.75
  • ZWO ASI220MM-mini
  • ZWO ASiair Plus
  • iOptron CEM40
  • Friendswood, Texas Bortle 7-8 suburban skies

Frames:

  • November 23, 2024
    • 229 60 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
  • December 19, 2024
    • 99 60 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • December 20, 2024
    • 28 60 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
  • December 31, 2024
    • 185 30 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
  • January 1, 2025
    • 46 30 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
  • January 23, 2025
    • 24 60 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
  • October 9, 2025
    • 68 60 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
    • 71 60 second Gain 150 Green lights
    • 30 0.02 second Gain 150 Green flats
    • 69 60 second Gain 150 Blue lights
    • 30 0.02 second Gain 150 Blue flats
  • October 10, 2025
    • 61 60 second Gain 150 Red lights
    • 53 30 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
    • 64 60 second Gain 150 Green lights
    • 52 30 second Gain 150 Green lights
    • 30 0.02 second Gain 150 Green flats
    • 64 60 second Gain 150 Blue lights
    • 52 3 second Gain 150 Blue lights
    • 30 0.02 second Gain 150 Blue flats
  • October 12, 2025
    • 49 180 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • October 18, 2025
    • 50 180 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 73 60 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
  • 30 Flat Darks from library matching flat lengths
  • 30 Darks from library

Processing geek info:

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

C/2025 A6 Comet Lemmon Tail Dynamics on October 31, 2025

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On October 31, 2025, my husband and I returned to Sargent, Texas for another opportunity to view and image Comet C/2025 A6 Lemmon.

I use an iPad to set up and watch the images from my telescope, and I was absolutely amazed to see the comet tail changing from frame to frame.  When I processed the comet into a single image, the changes in the tail smeared out.  So I made a movie.  

This movie was made with 14 frames of data using 1 minute each of red, green, and blue data, so 42 minutes worth of data.  The data was taken over about 45 minutes, so the faster sections of the movie are sped up by a factor of 970, and the slower sections of the movie are sped up by a factor of 388.  

In the movie, you can see knots in the comet’s tail near the comet’s head moving towards the left away from the comet’s head, but you can also see the further-out tail moving up to consolidate.  I think it’s absolutely amazing you can see so much change in the comet’s tail over this short a period of time.

Camera geek info – telescope:

  • 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
  • Sargent, Texas Bortle 4 skies

Frames – telescope:

  • October 31, 2025
    • 14 60 second Gain 150 R lights 
    • 30 0.05 second Gain 150 R flats
    • 14 60 second Gain 150 G lights 
    • 30 0.02 second Gain 150 G flats
    • 14 60 second Gain 150 B lights
    • 30 0.02 second Gain 150 B flats
    • Matching darks and flat darks from library

C/2025 A6 Comet Lemmon on October 31, 2025 using three different focal lengths

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On October 31, 2025, my husband and I returned to Sargent, Texas for another opportunity to view and image Comet C/2025 A6 Lemmon.

I initially set up my camera with a 24 mm lens (very wide field, 53 deg by 35 deg) looking towards the sunset to capture the color gradient (I love these deep colors!).  Then, after it got dark, I took a series of images (about 29.47 minutes worth) to capture the stars and the comet.  By October 31, the comet was moving further away from us, and if you compare the October 31 picture with the October 26 picture, you can see that the comet appears smaller, dimmer, and further to the left (west) relative to the stars.  It also appears to have a hook in its tail.

I took additional data with an 85 mm lens (15 deg by 10 deg field of view), about 7.6 minutes worth.  I cropped this image, so it is an even smaller field of view, and again the tail appears to have a hook in it.

All of the pictures with the camera were taken using just a tripod (no tracking mount), so I had to do a fair bit of processing to remove the star trails in the data (BlurXterminator is a great tool for this), and I had to process the comet separately from the stars to keep it from smearing since is moving relative to the stars.

Finally, while I was taking pictures with the camera on a tripod, I was also taking pictures with my small telescope with a 430 mm focal length and a 1.8 by 1.2 degree field of view, about 42 minutes worth.  Of course the comet and the tail are obvious here, and the field of view is too small to see any further out hook in the tail.  What is not obvious in this integrated image is that there was a knot in the comet’s tail that was obviously moving between frames, which I find amazing.  It’ll take a movie to show that, which is my next project.

Which version do you like the best?

Camera geek info – 24 mm sunset image:

  • Canon EOS 60D in manual mode set 8 second exposure, ISO 800
  • Sigma 24-70 mm f/2.8EX lens, set at f/3.5, 24 mm, manual focus
  • Tripod
  • Intervalometer 

Frames – 24 mm sunset image:

  • October 31, 2025
    • 221 8 second lights
    • 30 1/2500 second flats
    • Matching darks and dark flats from library

Camera geek info – 85 mm night image:

  • Canon EOS 60D in manual mode set at 8 second exposure, ISO 800
  • Canon EF 85 mm f/1.8 lens at f/2.8 manual focus at infinity
  • Tripod
  • Intervalometer 

Frames – 85 mm night image:

  • October 31, 2025
    • 57 8 second lights
    • 31 1/2500 second flats
    • Matching darks and dark flats from library

Camera geek info – telescope:

  • 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
  • Sargent, Texas Bortle 4 skies

Frames – telescope:

  • October 31, 2025
    • 14 60 second Gain 150 R lights 
    • 30 0.05 second Gain 150 R flats
    • 14 60 second Gain 150 G lights 
    • 30 0.02 second Gain 150 G flats
    • 14 60 second Gain 150 B lights
    • 30 0.02 second Gain 150 B flats
    • Matching darks and flat darks from library

Abell 7 Planetary Nebula

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When we travel to the glorious dark skies of Dell City, Texas, I try to image objects that I won’t be able to easily image from my light polluted Bortle 8 driveway.  I also try to pick a challenge object – one that needs a lot of time even from the Bortle 2 – 3 skies of Dell City.  In November 2025, my challenge object was Abell 7, a planetary nebula.  Even in 10 minute images with the Ha and Oiii filters, I could not see the nebula.  However, after integrating 10.3 hours of Ha and 8.2 hours of Oiii data, I was able to see and process Abell 7.

Abell 7 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 1680 light years away, and it has an apparent size of 12.733 arcminutes, making it about 6.2 light years across.  It’s estimated to be 20,841 years old based on the expansion of the nebula, which is “ancient” for a planetary nebula.

I find these small nebulae beautiful and fascinating. Each has its own unique structure.  This one has Hydrogen Ha emissions (mapped to red) and Oxygen Oiii emissions (mapped to blue).  Much of the nebula is purple, so it has both Ha and Oiii emissions.  The strongest Ha regions are on opposite sides of the nebula.  There is a variation in intensity – the center and the outer rim are both dimmer than the brighter middle ring.  It also appears to me to be clumpy or fuzzy, which is not surprising given its age.

In addition to the nebula, there are several background galaxies in this image.  I didn’t spend much time collecting RGB data, so there’s not a lot of detail in the galaxies.  The most prominent one in the image is just above and to the left of the nebula.

In this image, the stars and galaxies 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, galaxies, and stars were processed separately to maximally enhance the nebula and galaxies.

Camera geek info:

  • 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
  • William Optics Uniguide 32MM F/3.75
  • ZWO ASI220MM-mini
  • iOptron CEM40
  • Dell City, Texas Bortle 2-3 dark skies

Frames:

  • November 9, 2025
    • 12 600 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
    • 14 600 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • November 10, 2025
    • 60 30 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
    • 60 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
    • 19 600 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
  • November 11, 2025
    • 20 600 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • November 12, 2025
    • 13 600 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
  • November 13, 2025
    • 8 600 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
    • 9 600 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • November 14, 2025
    • 10 600 second Gain 150 Ha lights
    • 30 1.0 second Gain 150 Ha flats
    • 6 600 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
  • 30 Flat Darks from library
  • 30 Darks from library

Processing geek info:

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

Sh2-236 IC410 NGC1893 The Tadpole Nebula

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Sharpless Sh2-236 is commonly called the Tadpole Nebula since it appears to contain a tadpole (or two – depending on how you interpret the two white-pink objects near the center of this image).  How many tadpoles do you see? 

This image shows HII region Sharpless Sh2-236 (the whole image) (also cataloged in the Index Catalog of Nebulae as 410 (IC410)), the open cluster NG1893 (stars in the blue region), and the two “cometary globule” tadpole nebulae numbered Simeiz (Sim) 129 and 130.

Sh2-236 is an H II region emission nebula, a region of ionized atomic hydrogen.  The H II regions in the Sharpless 2 catalog were “defined not only in terms of the ionized gas but also in terms of the hot stars which are responsible for the ionization.”

The young open cluster NGC1893 contains five O type stars, short-lived, hot, massive stars that ionize the surrounding molecular cloud.  One of the stars is theorized to be 4 million years old; the others, 2 – 3 million years old.  Between these O-type stars and the two cometary globules are smaller, younger stars that are 1 – 2 million years old that appear to have an age gradient with older stars closer to the O-type stars and younger stars closer to the cometary globules.  The O-type stars are theorized to be causing triggered star formation in the globules – as the ionization and shock wave from the O-type stars hit the initial clumps of material that are the tadpoles, “radiation driven implosion” caused the clumps to form stars.

The tadpoles are believed to be denser clumps of material.  The tails are theorized to be formed from ionized gas from the edge of the tadpole closest to the O-type stars flowing along the magnetic field away from the O-type stars.  The more tadpole-like nebula, Sim 129, is on the far side of the nebula from us and is theorized to contain young stars.  Sim 130 is on the near side of the nebula closer to us and is theorized to contain “incipient stars” – the earliest stage of star formation, so the stellar evolutionary stage in the two tadpoles is different.  I am always amazed when I realize that our galaxy is still under construction!

Sh2-236 is located in the Milky Way, approximately 10500 light years away.  The square “box” of the nebula in the first image is 60 arc minutes across, so the nebula is approximately 183 light years across.  

I collected the frames for this image under the fantastic dark skies of Dell City, Texas.  When we go out there, I generally try for some easier targets and a more difficult target – this was one of the easier targets.  I need far less time than I do for images from my light-polluted driveway, but it was something of a guess to know whether I’d taken enough data to end up with a good image.  In this image, the stars came from images using red-green-blue filters with about 17 minutes of data each, and the nebula came from images using Sulfer ii (4.1 hours of data mapped to red), Hydrogen alpha (4.3 hours of data mapped to green) and Oxygen iii (4.25 hours of data mapped to blue) filters, the standard SHO mapping.  But after doing that mapping, I used Narrowband Normalization to shift the colors so that it wasn’t overly green and to enhance the reds and blues.  The nebula was processed separately from the stars to maximally enhance it.

Camera geek info:

  • William Optics Zenith Star 73 III APO telescope
  • William Optics Flat 73A
  • ZWO 2” Electronic Filter Wheel
  • Antila RGB and SHO filters
  • ZWO ASI183MM-Pro-Mono camera
  • William Optics Uniguide 32MM F/3.75
  • ZWO ASI220MM-mini
  • ZWO ASiair Plus
  • iOptron CEM40
  • Dell City, Texas Bortle 2 – 3 skies

Frames:

  • November 12, 2025
    • 17 300 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
    • 14 300 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 15 300 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • November 13, 2025
    • 17 300 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
    • 18 300 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 15 300 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • November 10, 2025
    • 18 300 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
    • 19 300 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 19 300 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • November 11, 2025
    • 34 30 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
    • 35 30 second Gain 150 Green lights
    • 30 0.02 second Gain 150 Green flats
    • 35 30 second Gain 150 Blue lights
    • 30 0.02 second Gain 150 Blue flats
  • 30 Flat Darks matching flat durations from library
  • 30 Darks matching light durations from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Narrowband Normalization

C/2025 A6 Comet Lemmon on October 26, 2025 Tail Motion Movie

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One of the things that really impressed me when I was imaging Comet C/2025 A6 Lemmon on October 26, 2025 was that the tail changed from frame to frame.  There appeared to be a “knot” that moved along the tail away from the comet head.

It’s taken me a while to figure out how to make a movie of this motion.  One challenge was that since it was just after sunset and the comet was near the horizon, the background level changed from frame to frame.  I realized that I could use Local Normalization and generate normalized files that helped with the varying background a lot.  I also started with separate red, green, blue data that had to be aligned using CometAlignment to make RGB images and then re-aligned with CometAlignment with the original green positions to show the comet motion with respect to the stars.  I ended up making two sets of images: one aligned to the green frames at each time step to show the comet motion relative to the stars, and one with all the frames aligned to the comet to show the comet tail changes. 

This movie was made with 15 frames of data using 1 minute each of red, green, and blue data.  The comet showed this much motion over about 45 minutes!  

Cool!

Camera geek info – telescope:

  • 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
  • Sargent, Texas Bortle 4 skies

Frames – telescope:

  • October 26, 2025
    • 16 60 second Gain 150 R lights 
    • 30 0.05 second Gain 150 R flats
    • 15 60 second Gain 150 G lights 
    • 30 0.02 second Gain 150 G flats
    • 17 60 second Gain 150 B lights (16 for stars)
    • 30 0.02 second Gain 150 B flats
    • Matching darks and flat darks from library

C/2025 A6 Comet Lemmon on October 26, 2025 using three different focal lengths

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I finally had some time over my Christmas break to process (some of) my comet data, including the wide field images I took on Sunday, October 26, 2025 from the darker (Bortle 4) skies of Sargent, Texas.  

I miscalculated the direction of the comet motion and initially set up the camera with a 24 mm lens (very wide field, 53 deg by 35 deg) looking towards the sunset to get a lovely gradient of color.  Then, after it got dark, I took a series of images of the stars, about 13 minutes worth.  I didn’t take more data because I decided to move the camera to get a better framing.  The comet is in this image, but I had to circle it because it is so dim and doesn’t have an obvious tail.  You can see that it is below a triangle of stars, the Serpent’s head in the Serpens Caput (Serpent Head) constellation.

I took additional data with the 24 mm lens with a better framing, about 33 minutes worth.  I didn’t take more data because I wanted to switch to a different lens.  Happily, the comet is clearly visible in this image; no circling needed!  And the triangle of stars is still visible as well.

I took additional data with an 85 mm lens (15 deg by 10 deg field of view), about 11 minutes worth.  I cropped this image, so it is an even smaller field of view, again with the comet clearly visible along with the triangle of stars above it.

All of the pictures with the camera were taken using just a tripod (no tracking mount), so I had to do a fair bit of processing to remove the star trails in the data (BlurXterminator is a great tool for this), and I had to process the comet separately from the stars to keep it from smearing since is moving relative to the stars.

Finally, while I was taking pictures with the camera on a tripod, I was also taking pictures with my small telescope with a 430 mm focal length and a 1.8 by 1.2 degree field of view, about 45 minutes worth.  Of course the comet and its tail is amazingly obvious here, and I could see its tail changing over the course of the evening.  I’m working on making a movie of that, stay tuned!

Which version do you like the best?

Camera geek info – 24 mm sunset image:

  • Canon EOS 60D in manual mode set at f/8, 10 second exposure, ISO 400
  • Sigma 24-70 mm f/2.8EX lens, set at 24 mm, manual focus
  • Tripod
  • Intervalometer 

Frames – 24 mm sunset image:

  • October 26, 2025
    • 80 10 second lights
    • 30 1/2500 second flats
    • Matching darks and dark flats from library

Camera geek info – 24 mm night image:

  • Canon EOS 60D in manual mode set at f/2.8, 20 second exposure, ISO 400
  • Sigma 24-70 mm f/2.8EX lens, set at 24 mm, manual focus
  • Tripod
  • Intervalometer 

Frames – 24 mm night image:

  • October 26, 2025
    • 100 20 second lights
    • 30 1/2500 second flats
    • Matching darks and dark flats from library

Camera geek info – 85 mm night image:

  • Canon EOS 60D in manual mode set at f/2.5, 6 second exposure, ISO 800
  • Canon EF 85 mm f/1.8 lens at f/2.5 manual focus at infinity
  • Tripod
  • Intervalometer 

Frames – 85 mm night image:

  • October 26, 2025
    • 110 6 second lights
    • 30 1/2500 second flats
    • Matching darks and dark flats from library

Camera geek info – telescope:

  • 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
  • Sargent, Texas Bortle 4 skies

Frames – telescope:

  • October 26, 2025
    • 16 60 second Gain 150 R lights 
    • 30 0.05 second Gain 150 R flats
    • 15 60 second Gain 150 G lights 
    • 30 0.02 second Gain 150 G flats
    • 17 60 second Gain 150 B lights (16 for stars)
    • 30 0.02 second Gain 150 B flats
    • Matching darks and flat darks from library

Sh2-184 NGC281 The Pac-Man Nebula (or, alternately, the Spouting Whale Nebula)

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Sharpless Sh2-184 NGC281 is commonly called the Pac-Man Nebula for obvious reasons – it looks like the video game character Pac-Man with its round shape and open mouth.  Yet I also see a spouting whale – same big mouth but with a tail and spouting water out of its blowhole.  Can you see it?

I made two versions of this – one “square” with the frame that is missing the stars in the upper right corner, and one “surfing the waves” angled one that has a complete starfield.  Which version do you like better?

This image shows HII region Sharpless Sh2-184 (the whole image) and the open cluster IC1590 (stars in the blue region).  

Sh2-184 is an H II region emission nebula, a region of ionized atomic hydrogen.  The H II regions in the Sharpless 2 catalog were “defined not only in terms of the ionized gas but also in terms of the hot stars which are responsible for the ionization.”

The young open cluster IC1590 is about 3.5 – 4.4 million years old.  Among other stars, it contains four O type stars, short-lived, hot, massive stars that ionize the surrounding molecular cloud. 

The massive stars are believed to be triggering star formation in the surrounding H II region by ionizing, heating, and compressing gas in molecular cloud in which they formed.  In the periphery of the open cluster, Young Stellar Objects (YSOs), young, low-mass stars deeply embedded in parent molecular cloud, are found that are 1 – 2 million years old and 0.5 – 3.5 times the mass of our sun.  I am always amazed when I realize that our galaxy is still under construction!

Sh2-184 is located in the Milky Way, approximately 10110 light years away.  This image is 50 arc minutes across, so the image is approximately 150 light years across. 

I collected the frames for this image under the fantastic dark skies of Dell City, Texas.  When we go out there, I generally try for some easier targets and a more difficult target – this was one of the easier targets.  I need far less time than I do for images from my light-polluted driveway, but it was something of a guess to know whether I’d taken enough data to end up with a good image.  In this image, the stars came from images using red-green-blue filters with 30 minutes of data each, and the nebula came from images using Sulfer ii (3.33 hours of data mapped to red), Hydrogen alpha (3.5 hours of data mapped to green) and Oxygen iii (3 hours of data mapped to blue) filters, the standard SHO mapping.  But after doing that mapping, I used Narrowband Normalization to shift the colors so that it wasn’t overly green and to enhance the reds and blues.  The nebula was processed separately from the stars to maximally enhance it.  As always, I like color, so I leaned into the rich colors.

What do you think of the colors?  What do you think of the alternate name?

Camera geek info – Narrowband:

  • William Optics Zenith Star 73 III APO telescope
  • William Optics Flat 73A
  • ZWO 2” Electronic Filter Wheel
  • Antila RGB and SHO filters
  • ZWO ASI183MM-Pro-Mono camera
  • William Optics Uniguide 32MM F/3.75
  • ZWO ASI220MM-mini
  • ZWO ASiair Plus
  • iOptron CEM40
  • Dell City, Texas Bortle 2 – 3 skies

Frames:

  • November 8, 2025
    • 11 300 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
    • 11 300 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 11 300 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • November 9, 2025
    • 9 300 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
    • 9 300 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 8 300 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • November 10, 2025
    • 60 30 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
    • 60 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
  • November 11, 2025
    • 22 300 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
    • 16 300 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 21 300 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • 30 Flat Darks matching flat durations from library
  • 30 Darks matching light durations from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Narrowband Normalization