Sunday, February 18, 2024

M45 - The Pleiades

 The last in a recent string of clear nights ... but 1st a quick story:

A few years back my family was driving home from a family event on beautiful clear night. Someone remarked how beautiful the stars looked and my mother-in-law said, "oh yes, and you can really see the little Dipper!". I'm driving and trying to contain my inner Sheldon Cooper, we are driving south, there is no way she's talking about the Little Dipper. When we got home and parked the car, I asked her to show me. She pointed directly to the Pleiades. I realized it does in fact look like a min dipper. I politely explained what she was actually looking at and showed her how to find the actual Little Dipper. She was un-impressed. I don't think I ever consciously realized that M45 looks like a mini-dipper before (even though I have observed it for years). Now I often describe it in this way when describing it. Now back to your regularly scheduled blog post.

From Saturday 2/3/2024 through Tuesday 2/6/2024, we had a string of 4 clear nights. Skies weren't amazing, the transparency was not great, but the best opportunity for any astronomy related activity in 2 months or so. i got out to the observatory to image on 2/3/2024. Family and work obligations prevented me from imaging Sunday night or Monday night. Tuesday night was my last chance. The forecast was for clear skies early with the transparency turning poor/clouds around 11. Good news, it gets dark early enough to make imaging under worthwhile. Our Tuesday night imaging group was also in session. I joined from home via Zoom. 

After work, I quickly set up my scope. I had not used my home setup since October 3rd! I started collecting exposures at 7:04 PM. Since we were so close to New Moon, I decided on a broadband target, M45 (a.k.a. The Pleiades or Seven Sisters). Looking to improve on my initial result of this image from 2021. By 9:00 PM the transparency was starting to degrade. I kept imaging until 10:32 but had discard quite a most subs collected after 9:41 PM due to haze/thin clouds. Here's the resulting image. I'm pleased with result but hope to add data to this in the future, hope to pull out more of the faint background dust. 

M45, The Pleiades - from my backyard on 02/02/2024.

Showing the mini-dipper asterism. 

Processing:

All pre and post processing was performed in PixInsight. Pre-processing: Blink & WBPP (2x drizzle integration). Linear Post-Processing: GraXpert, BXT (correct only), SPCC, BXT, NXT, and HT. Non-linear Post-processing: StarXT. Stars: Curves (saturation) and SCNR. Starless: Curves (multiple for brightening, contrast, and saturation), SCNR, LHE (3 kernel sizes), Unsharp Mask, MMT, & PixelMath (to screen stars back in). Integer Resample was used to down sample the image. 

What is it?

Messier 45 is probably the most famous Open Star Cluster in the night sky. It is easily visible to the naked eye. The brightest 6 stars form a distinctive mini-dipper pattern not far from Orion. It is known by many names by different cultures around the world. If you drive a Subaru, look at the logo. Subaru ids the name for M45 in Japan. The cluster contains over 1,000 confirmed stars. The reflection nebula that surrounds the cluster is not associated with the cluster. The cluster is just passing through it and the starlight from the cluster is reflecting it, in the same way our atmosphere scatters the light from the Sun making our sky appear blue. 

Annotated version of the image of M45.

How big is it?

This object has an apparent size of 12 arcminutes (1 degree is 60 arcminutes) on the night sky. It is 16 light-years (ly) in diameter.

How far is it?

It is located about 440 light-years (ly) from Earth in the Constellation Taurus.

How to find it?

This object is easily visible to the naked eye. You won't see the beautiful reflection nebula, but the 6 brightest stars are quite bright and form a very recognizable mini-dipper pattern (asterism). It is not far from the V-shaped Hyades in Taurus. Start with the belt stars in Orion. Starting from the lowest star (Alnitak), extend through the highest star (Mintaka) for about 35 degrees (about 3-1/2 fists). Refer to the finder charts below.

How to use Orion's Belt to find M45.

A finder chart for M45 with a tighter field of view.

Image Details:

Capture Date: 02/06/2024
Location: Eden, NY
Telescope: Explore Scientific ED80 Essential Series Air-Spaced Triplet Refractor
Camera: ZWO ASI2600MC Pro
Filter: none
Mount: Sky-Watcher USA EQ6-R Pro
Exposure: 66 exposures at 120 sec / Gain 100 / Offset 50 / -10°C each for a total exposure of 2 hour and 12 minutes.
Software: NINA, SharpCap Pro, PHD2, and PixInsight


Clear Skies!
Ernie




Saturday, February 10, 2024

A Tale of Two Supernovae ... Part 2

 Saturday Night Turned into Sunday Morning ...

Picking up where we left off in part 1, we removed the L-eXtreme filter from the imaging train because we planned on imaging a broadband target, and the dual-narrowband filter would detrimentally impact the results. Dual-narrowband filters are effective for emission nebulae like H2 regions, supernovae remnants, and planetary nebulae but are not recommended when imaging targets like galaxies, star clusters, and reflection nebulae. Since we changed the imaging train, we took a second set of flats to be used with this target. It was after midnight at this point, and we agreed to image to 1 am. We opened the roof and slewed the telescope to Virgo, which was rising above the eastern horizon. Our target was a recent supernova that had occurred in the Galaxy NGC 4216. The supernova was discovered on January 4, 2024 by Japanese astronomer Koichi Itagaki, who has discovered 170 supernovae! This supernova has a designation of, SN 2024gy. 

We imaged until the agreed upon time of 1 am. We ended up rejecting the last few subs (short for sub-exposure) as the image quality was degrading due to the poor transparency. Had to be some very high thin cloud or haze, even though the sky looked clear, guiding, focus, and image quality indicated we were losing the skies. We managed to collect 7 subs at 180 sec each. The supernova, the dust lanes in NGC 4216, and many smaller background galaxies were visible in the individual exposures. Here is the resulting image: 

SN 2024gy in NGC 4216 captured on 2/4/2024 from the BMO.

An annotated version of the image indicating the location of supernova SN 2024gy.


An animated GIF of SN 2024gy in NGC 4216

Processing:

All pre and post processing was performed in PixInsight. Pre-processing: Blink & WBPP. Linear Post-processing: GraXpert, BXT (correct only), Color Calibration, BXT, NXT, & Histogram Transformation. Non-linear Post Processing: SXT. Stars: Curves (saturation) and SCNR. Starless: Curves (contrast & saturation), SCNR, LHE (3x's), Unsharp Mask, MMT, and PixelMath (to screen the stars back in).

Magnitude Estimate:

Disclaimer: I'm not an experienced variable star observer. There is a decent probability that the following methodology is flawed.

The BAA had our monthly meeting for February on 2/9/2024. After the meeting, I joined the Astrophotography breakout room, and we discussed estimating the magnitude of the supernova from the images we collected on 2/4/2024. This ended up as a fun activity for the small group of us left in the meeting. Since imaging supernova SN2023ixf in M101 in May of 2023, I've made an effort to try to learn how to estimate the magnitude of the supernova from my images. I recently joined the AAVSO and managed to cobble together and idea on how to estimate the magnitude of the supernova from stars with known magnitudes in the same field of view. The manner in which we captured images was optimized for "pretty pictures" not photometry, but the value we ended up with is pretty close to other reported values of the supernova from the same date. 

One of the other members generated a star chart from the AAVSO website. This chart depicted stars in the field of view, of which several were labeled with known magnitudes. It took some trial and error to the chart correct so it matched the field of view of our image. The first chart was off, we had used RA & Dec coordinates from Sky Safari. When we used RA & Dec coordinates from The Sky X, it finally matched the image. We think the difference may be the epoch used by each software (J2000 vs. Jnow). We visually estimated the brightness to be somewhere between 13 and 15th magnitude. Another member pulled a light curve from the AAVSO website. This light curve was compiled from member reports and indicated that the magnitude was around 13.5. We identified a star in the field with a known magnitude of 13.1. I took one of the calibrated and debayered individual sub exposures and extracted the RGB channels in PixInsight. The image was still linear, only a display or screen stretch was applied. Using the green channel, we measured the flux of the known star and the supernova using PixInsight's Dynamic PSF process. We put the resulting values into this formula:

Mag(supernova) = Mag (star) - 2.5Log(FluxSN/FluxStar)

We came up with a magnitude of 13.4 which closely matches reported values!!!! 

What is it?

SN 2024gy is a Type 1A Supernova in the Galaxy NGC 4216. It was discovered on 1/4/2024 by Japanese astronomer Koichi Itagaki. Type 1A supernovae occur when a White Dwarf syphons material from another star that it is in a binary pair with. Once the White Dwarf reaches 1.4 times the mass of the Sun, it goes Supernova. This type of Supernova is used as a standard candle and is important in determining the distance to objects in the universe.

Annotated image of the field of view.

How far is it?

It is located about 45 million light-years (ly) from Earth in the Constellation Virgo.

How to find it?

SN  2024gy is located in the Galaxy NGC 4216 which is located in the Constellation Virgo. Refer to the Finder Chart below. The tiny red rectangle in the center of the image marks the position of NGC 4216. It is very near M86, in the bowl of Virgo.

      Finder Chart for NGC 4216. 

      Image Details:

      Capture Date: 02/04/2024
      Location: Beaver Meadow Observatory (North Java, NY)
      Telescope: Celestron 14" Edge HD w/0.7x Reducer
      Camera: ZWO ASI2600MC Pro
      Filter: none
      Mount: Astro Physics AP-1200
      Exposure: 7 exposures at 180 sec / Gain 100 / Offset 50 / -10°C each for a total exposure of 21 minutes
      Software: NINA, PHD2, and PixInsight


      Clear Skies!
      Ernie


      Thursday, February 8, 2024

      A Tale of Two Supernovae ... Part 1

       Saturday Night at the Observatory

      It has been several months since we have had a clear night. It was clear Saturday night 2/3/2024 into Sunday morning 2/4/2024. Our Astronomy club’s imaging group assembled at our Dark Sky Observatory. We call ourselves the Tuesday Night Imagers, but Tuesday night can be any night of the week.  We put my camera (ZWO ASI2600MC Pro) on the club’s Celestron 14” Edge HD Telescope which is on an Astro Physics AP-1200 mount. An Optolong L-eXtreme Dual-Narrowband filter was used to target specific wavelengths of light.

      The imaging team (for the club's equipment) was our Observatory Director (Dan), a member named Mike, and me. Our target was Messier 1 (M1) a.k.a. The Crab Nebula. M1 is a supernova remnant located in the constellation Taurus. We lost some time at the beginning of the night getting things running. The Observatory had not been used (due to poor weather) since mid-December. Programs and drivers needed to be updated and we needed to fine tune the Acquisition software for this new Telescope/Camera combination. We started to acquire images at 8:40 PM and imaged until 11:30 PM when we lost M1 to the Muck near the horizon and the trees. We closed the roof and took our flat frames. Mike removed his camera from the Tele Vue NP-10is that rides on the mount with the 14" Edge HD. We replaced it with an eyepiece to keep things close to balance so Dan and I could go after one more target. We'll cover that in part 2.

      We did encounter an issue with aberrations (spikes) on our stars. We were unable to resolve the issue Saturday night. Dan and Mike returned to the observatory Monday evening, and I joined them via Zoom. After some troubleshooting, we believe the issue is caused by the Celestron Dew Heater Ring. Even with the Star spike issue, we managed to collect 13 usable subs at 600 sec each for a total exposure of 130 minutes. Here is the resulting image:

      M1, The Crab Nebula from 2/3/2024, HOO version. BAA Tuesday Night Imagers.

      Processing:

      I did all pre and post processing in PixInsight. Pre-processing: Blink & WBPP. Linear Post-processing: GraXpert, BlurXTerminator (correct only), Spectrophotometric Color Calibration, BlurXTerminator, NoiseXTerminator, and Histogram Transformation. Non-Linear Post-processing: StarXTerminator. Starless: Narrowband Normalization (two methods as described below), Curves (Multiple iterations to increase brightness, contrast, and color saturation), SCNR, Local Histogram Equalization, Unsharp Mask, and Multiscale Median Transform. Stars: Curves (to increase color saturation) and SCNR. PixelMath was used to screen the stars back in. 

      I tried to different methods in the Narrowband Normalization process. Method 2 which produces an HOO result and Method 1, which produces a result that simulates the Hubble or SHO palette. The image above is the HOO version. I prefer this version. Here is the simulated SHO version:

      M1, The Crab Nebula, simulated SHO Version. BAA Tuesday Night Imagers.

      What is it?

      M1 is a supernova remnant. Humans observed the Supernova when it occurred in 1054. It was recorded by Chinese astronomers, and it appears that the event is also depicted in Petroglyphs in Arizona and New Mexico. The Chinese astronomers referred to it as a "Guest Star". it was visible during the day for 23 days and was visible at night for 653 days. The supernova also left behind a stellar remnant known as a Pulsar. The Crab Pulsar rotates 30.2 times per second. The nebula is expanding at a rate of 1,800 km/sec.

      Annotated image of M1, The Crab Nebula. 

      How big is it?

      This object has an angular distance of 6 x 4 arcminutes (1 degree is 60 arcminutes) on the night sky. The object is 13 x 11 light-years (ly) across. 

      How far is it?

      It is located about 6,300 light-years (ly) from Earth in the Constellation Taurus.

      How to find it?

      This object is relatively easy to find. It's very close to the bright star Zeta Tauri in the constellation Taurus. Refer to the finder chart below. This is a great visual target. It can be seen in binoculars and small telescopes. Dark skies help as it is it can get lost in light polluted skies. Larger aperture helps significantly. Although visible in smaller instruments, I believe it is far more interesting to observe in large aperture scopes. Nebula filters can aid in viewing this object.

          Finder Chart for M1.

          Image Details:

          Capture Date: 02/03/2024
          Location: Beaver Meadow Observatory (North Java, NY)
          Telescope: Celestron 14" Edge HD w/0.7x Reducer
          Camera: ZWO ASI2600MC Pro
          Filter: Optolong l-eXtreme 
          Mount: Astro Physics AP-1200
          Exposure: 13 exposures at 600 sec / Gain 100 / Offset 50 / -10°C each for a total exposure of 130 minutes (2.2 hours)
          Software: NINA, PHD2, and PixInsight


          Clear Skies!
          Ernie

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