Astrophotography – PekDar – Astrophotography Engineering

Rosette Nebula NGC 2237 – Caldwell 49

PekDar — Wed, 18 Jun 2025 13:30:32 +0000

By way of introduction to the Rosette Nebula NGC 2237

In this article, I have gathered in one place the most interesting information about the entire nebula and its selected regions. The information contained in this content is my own compilation based on collected data.

About the Nebula Itself
The Rosette Nebula (also known as Caldwell 49) is an H II region (ionized hydrogen) located near one end of a giant molecular cloud in Monoceros, a region of the Milky Way.

Rosette Nebula – NGC 2237 – Caldwell 49

It has been observed that the nebula has a shape resembling a human skull and is sometimes called the “Skull Nebula.” It should not be confused with the object designated as NGC 246, which is also called the “Skull Nebula.”

Rosette Nebula NGC 2237 – Location

Firmament – Coordinates for the nebula’s reference position (Equatorial (J2000)):

RA, Dec: 06h30m54.6143s, +05d02m57.008s
RA, Dec [Deg]: 97.727560, 5.049169

Rosette Nebula – KStars – location

The nebular complex has the following New General Catalogue (NGC) designations:

NGC 2237 – Part of the nebular region (also used to refer to the entire nebula)
NGC 2238 – Part of the nebular region
NGC 2239 – Part of the nebular region (Discovered by John Herschel)
NGC 2244 – Open cluster within the nebula (Discovered by John Flamsteed in 1690)
NGC 2246 – Part of the nebular region

The cluster and nebula are located 5,000 light-years from Earth and measure approximately 130 light-years in diameter. Radiation from young stars excites hydrogen atoms in the nebula, causing them to emit radiation themselves, forming the emission nebula that we observe. The nebula’s mass is estimated at about 10,000 solar masses.

Observations using the Chandra X-ray Observatory have revealed the presence of numerous newborn stars inside the optical Rosette Nebula and scattered throughout the dense molecular cloud. This stellar formation complex contains around 2,500 young stars, including massive O-type stars HD 46223 and HD 46150, which are primarily responsible for inflating the ionized hydrogen bubble. Most of the ongoing star-forming activity occurs in the dense molecular cloud southeast of the bubble.

There is also diffuse X-ray radiation visible among the stars within the bubble. This is caused by very hot plasma with temperatures ranging from 1 to 10 million K—significantly higher than the 10,000 K plasma temperature observed in H II regions—likely due to shock-heated winds from massive O-type stars.

NGC 2237 Region – Part of the Rosette Nebula

NGC 2237 is part of the Rosette Nebula, a large H II region located in the constellation Monoceros (the Unicorn). It is one of several cataloged nebular regions, alongside NGC 2238, NGC 2239, and NGC 2246.

Key Features of NGC 2237

Type: Emission nebula (part of the Rosette Nebula)
Distance: Approximately 5,000–5,200 light-years from Earth
Size: The entire Rosette Nebula has a diameter of about 130 light-years
Structure: Contains ionized hydrogen gas, which glows due to radiation from nearby young stars

Below is the highlighted entire area encompassing the regions:

NGC2237
NGC2238
NGC2239
NGC2246

Regions: NGC2237 NGC2238 NGC2239 NGC2246

The Role of the Nebula in the Star Formation Process

NGC 2237 is part of a star-forming region, where new stars are born from collapsing clouds of gas and dust. The open cluster NGC 2244, located at the center of the Rosette Nebula, contains young, massive stars that emit strong radiation and stellar winds, shaping the surrounding nebula.

Observations and Scientific Significance

X-ray studies (e.g., using the Chandra X-ray Observatory) have revealed numerous young stars embedded in the nebula.
Infrared observations help detect hidden protostars still forming within dense molecular clouds.
The nebula’s mass is estimated at around 10,000 solar masses, making it an important object for studying stellar evolution and nebular dynamics.

NGC 2238 Region

NGC 2238 is part of the Rosette Nebula, an H II region located in the constellation Monoceros (the Unicorn). It is an area of intense star-forming activity, where young stars emit ionizing radiation, causing atoms in the nebula to glow.

Compared to other H II regions like the Orion Nebula (M42) and Lagoon Nebula (M8), NGC 2238 is less intensively studied but remains an interesting site for star formation. In terms of brightness, NGC 2238 has an apparent magnitude of about 6, meaning it is visible through small telescopes and binoculars. Regarding size, NGC 2238 is part of the larger Rosette Nebula complex, which has a diameter of approximately 130 light-years.

Star Formation in NGC 2238
Within the Rosette Nebula, including NGC 2238, young, hot stars have formed from nebular material approximately 4 million years ago. These stars emit intense ultraviolet radiation, ionizing the nebular gas and causing it to glow. Additionally, stellar winds from these young stars have blown out the central region of the nebula, creating a distinct cavity surrounded by gas and dust layers—a phenomenon typical of H II regions, where massive stars shape the surrounding material.

Structure and Observations
NGC 2238, like other parts of the Rosette Nebula, is an emission nebula, meaning its gas glows due to ionization from nearby stars.

Methods for Observing NGC 2238

1. Visual Observations

Binoculars: Even a small pair of 50mm binoculars can reveal fragments of the nebula in a dark sky.
Telescopes: To observe larger structures, low magnifications (20–50x) and wide-angle eyepieces are recommended.
Filters: UHC or OIII filters enhance nebular contrast and structure.

2. Astronomical Photography

CCD cameras: Used to capture the nebula in different wavelengths, including H-alpha, which reveals gas details.
Long exposures: Since the nebula is relatively faint, long exposure times and precise telescope tracking are required.
Narrowband filters: H-alpha and SII filters improve nebular detail by isolating specific wavelengths.

3. Infrared Observations

Space telescopes: Infrared studies, using NASA’s Spitzer Space Telescope, allow researchers to examine structures hidden within nebular dust clouds.
Night vision devices: Some nebulae, including NGC 2238, can be observed using H-alpha filters on night vision equipment.

NGC 2239 Region

NGC 2239 is visible from both hemispheres at certain times of the year and has an apparent magnitude of approximately 4.8, making it barely visible to the naked eye but easily observable with binoculars. It lies around 5,000 light-years from Earth and has a diameter of approximately 130 light-years—a fascinating region of space that remains an active birthplace of stars!

Object Coordinates – J2000
Right Ascension: 06h 31m 55s
Declination: +04° 56’ 34”

NGC 2246 Region

This is an H II region, an area where intense radiation from young stars ionizes gas, causing it to glow. NGC 2246 is located approximately 5,000 light-years from Earth and has a diameter of about 130 light-years. Inside, there are around 2,500 young stars, including massive O-type stars, which are responsible for creating the ionized gas bubble.

H II regions form in stellar nurseries, where intense radiation from young, hot O- and B-type stars ionizes the surrounding gas.

H II Region in the Context of NGC 2246

NGC 2246 is part of the Rosette Nebula, which is itself a classic example of an H II region. Young, massive stars in the NGC 2244 open cluster emit powerful ultraviolet radiation, ionizing the surrounding hydrogen gas. This process creates the glowing nebula, making it visible in optical wavelengths.

In H II regions, additional processes influence star formation. Stellar winds and radiation pressure can compress gas and dust, triggering the collapse of clouds and the creation of new stars. In the Rosette Nebula, part of a giant molecular cloud, these processes are actively observed.

The Role of H II Regions in Galaxy Evolution

H II regions play a crucial role in galaxy evolution, regulating star formation and gas distribution. Studying such regions helps astronomers understand the mechanisms that lead to stellar formation and galactic structures.

Specific Star Formation Processes in H II Regions like NGC 2246

1. Gravitational Collapse of Molecular Clouds

H II regions originate from giant molecular clouds (GMCs) made primarily of cold molecular hydrogen (H₂).
Density fluctuations within these clouds can lead to gravitational collapse, forming dense cores, the precursors to protostars.

2. Triggered Star Formation

Young, massive stars emit intense UV radiation and powerful stellar winds.
This UV radiation ionizes the surrounding gas, creating hot (≈10,000 K) ionized H II regions.
Expanding shock waves compress dense gas pockets, triggering new protostar formation.
Dark structures like elephant trunks and Bok globules resist ionization, allowing stars to form within.

3. Internal Processes in Collapsing Cores

Fragmentation of the cloud leads to dense cores.
Accretion feeds protostars, which shine in infrared wavelengths.
Protoplanetary disks and jets emerge, shaping stellar environments.
Once nuclear fusion begins, a protostar enters the main sequence phase.

Observations of NGC 2246 confirm active star formation. Dark collapsing globules, intense X-ray emissions from newborn stars (Chandra X-ray Observatory), and young star clusters like NGC 2244 illustrate the ongoing stellar birth.

NGC 2244 Star Cluster (Caldwell 50)

The open cluster at the heart of the Rosette Nebula, also called Caldwell 50, is a young star cluster in the Monoceros constellation.

Stars in NGC 2244 formed from Rosette Nebula material several million years ago.
Their UV radiation ionizes hydrogen gas, illuminating the nebula.
Stellar winds from these stars create a central cavity, pushing gas outward.

Region: NGC2244

Key Features of the Cluster

Distance: Approximately 5,200 light-years from Earth
Age: Less than 5 million years
Size: The cluster has a radius of about 18 light-years
Brightness: Apparent magnitude 4.8, making it visible through binoculars

Most Notable Stars

HD 46223: A massive, extremely hot O4V-type star, about 400,000 times brighter than the Sun and 50 times more massive. One of the most energetic stars in the region.
- Surface Temperature: Around 40,000 K (Kelvin)
HD 46150: An O5V-type star, 450,000 times brighter than the Sun with a mass of up to 60 times that of the Sun.

These stars emit intense radiation and stellar winds, which shape the surrounding nebula.

Stars: HD46223, HD46150

The Significance of NGC 2244 in Astronomy

NGC 2244 holds great importance in astronomy due to its role in stellar formation processes and its interaction with the surrounding Rosette Nebula. Here’s why astronomers study this cluster:

Young, massive stars: NGC 2244 contains hot, massive O-type stars, some of the brightest and most energetic stars in the universe. They emit intense ultraviolet radiation, which ionizes the surrounding hydrogen gas, making the Rosette Nebula glow.
Impact on the surrounding nebula: The strong stellar winds from stars in NGC 2244 push gas and dust away, creating the central cavity in the Rosette Nebula. This process helps astronomers understand how massive stars shape their surroundings and influence future star formation.
Studies of stellar formation: Since NGC 2244 is a relatively young cluster (less than 5 million years old), it is an ideal target for studying the early stages of stellar evolution. Observations of this cluster help scientists understand how stars form, evolve, and interact.
X-ray and infrared observations: Astronomers use telescopes like Chandra X-ray Observatory and Spitzer Space Telescope to study the cluster in X-ray and infrared wavelengths. These observations reveal hidden young stars still embedded in gas and dust, providing valuable insights into stellar birth.
A window into galaxy evolution: Because NGC 2244 is part of a larger H II region (ionized hydrogen cloud), studying it helps astronomers understand how similar nebulae contribute to chemical enrichment and galaxy evolution.

How Do Astronomers Observe NGC 2244 Using Different Telescopes?

Astronomers study NGC 2244 and the Rosette Nebula using various telescopes that observe different parts of the electromagnetic spectrum. Each type of observation provides unique information about the cluster’s structure, composition, and ongoing processes.

1. Optical Observations – Telescopes like the Hubble Space Telescope (HST) and ground-based observatories capture visible light emitted by stars and ionized gas in the nebula, helping map the cluster’s structure, star distribution, and brightness.

Examples of telescopes:

Hubble Space Telescope (HST)
Very Large Telescope (VLT) – ESO
Keck Observatory

2. Infrared Observations – Infrared telescopes like the Spitzer Space Telescope and James Webb Space Telescope (JWST) allow astronomers to detect young stars hidden within gas and dust clouds. Infrared wavelengths penetrate dust clouds, revealing ongoing star formation.

Examples of telescopes:

Spitzer Space Telescope (NASA)
James Webb Space Telescope (JWST)
Infrared Astronomical Satellite (IRAS)

3. Obserwacje w promieniowaniu rentgenowskim – Chandra X-ray Observatory bada wysokoenergetyczne promieniowanie rentgenowskie emitowane przez gorące, młode gwiazdy w NGC 2244.
Pomaga w identyfikacji gwiazd neutronowych, czarnych dziur oraz procesów związanych z silnymi wiatrami gwiazdowymi.

Przykłady teleskopów:
Chandra X-ray Observatory (NASA)
XMM-Newton (ESA)

4. Obserwacje radiowe – Radioteleskopy, takie jak ALMA i VLA, badają chłodne obłoki gazu i pyłu, które mogą być miejscem narodzin nowych gwiazd.

Przykłady teleskopów:
Atacama Large Millimeter/submillimeter Array (ALMA)
Very Large Array (VLA)
Green Bank Telescope (GBT)

Dlaczego używa się różnych teleskopów?
Każdy zakres promieniowania elektromagnetycznego dostarcza unikalnych informacji o NGC 2244 i Mgławicy Rozeta:

Światło widzialne → Struktura mgławicy i rozmieszczenie gwiazd.
Podczerwień → Ukryte młode gwiazdy i procesy formowania.
Rentgen → Gorące, masywne gwiazdy i ich wpływ na otoczenie.
Radio → Chłodne obłoki gazu i pyłu, z których powstają nowe gwiazdy.

Pomagają w analizie składu chemicznego mgławicy oraz dynamiki gazu.

Podsumowanie

Mgławica Rozeta dostarcza cennych informacji o procesach ewolucji gwiazd i wpływie masywnych gwiazd na swoje otoczenie, co czyni ją jednym z najważniejszych obiektów badań w astrofizyce.

Bibliografia:
https://en.wikipedia.org/wiki/Rosette_Nebula
https://www.nasa.gov/image-article/rosette-nebula/
http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+2237
https://theskylive.com/sky/deepsky/ngc2239-object
https://theskylive.com/sky/deepsky/ngc2246-rosette-b-object

http://cdsportal.u-strasbg.fr/?target=NGC%202238%20
http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NGC%202238
http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+2237
https://ned.ipac.caltech.edu/cgi-bin/objsearch?extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES&objname=NGC%202238
https://pl.wikipedia.org/wiki/NGC_246

PGC 13696 (UGC 2838) – The Galaxy Behind the Pleiades. Deep Sky Range Test

PekDar — Sat, 21 Jan 2023 15:30:08 +0000

PGC 13696

Beyond Aesthetic Astrophotography When imaging the M45 cluster (The Pleiades), most attention is focused on the bright blue stars and the surrounding reflection nebula. However, for an engineering-minded astrophotographer, the real challenge lies deeper. Just next to the star Electra lies an object that serves as an ultimate test of optical performance and sky transparency – the spiral galaxy PGC 13696, also cataloged as UGC 2838.

Technical Data and Reality

The brightness of this galaxy is approximately 17 magnitude (B). It is an object well beyond the visual reach of most amateur telescopes (even 10-12 inch apertures under average skies).

Type: Spiral Galaxy (Sc)
Distance: ~315-330 million light-years (based on redshift z ~ 0.022)
Apparent Size: approx. 1.0′ x 0.2′

PGC 13696 Spiral Galaxy – crop

Cosmic Perspective

Looking at this image, you are witnessing a drastic contrast of time and space.

Foreground (Electra and dust): The light from the Pleiades stars traveled to us for “only” 440 years. The stars themselves are young, formed about 100 million years ago – back when dinosaurs ruled the Earth (Cretaceous period).
Background (PGC 13696): The light from this faint “fuzz” began its journey towards us over 300 million years ago. This corresponds to the Carboniferous period on Earth – long before the first dinosaurs appeared, when our planet was covered in giant ferns and forests that we mine today as coal.

In the cropped image, the elongated shape of the galactic disk and the faint structure of the spiral arms are clearly visible. Capturing this object so close to a bright star like Electra (3.7 mag) is challenging due to glare and the need to maintain high dynamic range. It requires precise calibration with Flat frames to extract the faint signal from the background sky noise.

Every time I look at such distant objects, I realize what the average life time of a human being is on a cosmic time scale.

A piece of time, how small.

Technical information
Date: 12.2020
Composition: APP
Processing: APP, RawTherapee, GIMP + add-ons (Linux)
Summary exposure: 6h
Calibration frames: Darks, Bias, Flats

The Leo Triplet (M66 Group) – A Gravitational Dance of Three Galaxies

PekDar — Tue, 03 Jan 2023 11:31:36 +0000

The Leo Triplet – A Cosmic Laboratory

Is more than just a popular astrophotography target in the spring sky. It is a textbook example of tidal interactions between galaxies. Located approximately 35 million light-years from Earth, the group consists of three large spiral galaxies: M65, M66, and NGC 3628, all fitting within a single field of view, creating a spectacular frame.

Source: https://en.wikipedia.org/wiki/Leo_Triplet

Detailed Object Analysis

M65 (NGC 3623): In contrast to its neighbor, M65 appears “calm.” It is a tightly wound spiral that, despite the proximity of other objects, has maintained a relatively intact disk structure, although a trained eye might spot a slight warp at the edges.

M65 – is an intermediate spiral galaxy about 35 million light-years away in the constellation Leo, within its highly equatorial southern half. It was discovered by Charles Messier in 1780. With M66 and NGC 3628, it forms the Leo Triplet, a small close group of galaxies. The galaxy is low in dust and gas, and there is little star formation in it, although there has been some relatively recently in the arms. The ratio of old stars to new stars is correspondingly quite high. In most wavelengths it is quite uninteresting, though there is a radio source visible in the NVSS, offset from the core by about two arc-minutes. The identity of the source is uncertain, as it has not been identified visually, or formally studied in any published papers.

To the eye, M65’s disk appears slightly warped, and its relatively recent burst of star formation is also suggestive of some external disturbance. Rots (1978) suggests that the two other galaxies in the Leo Triplet interacted with each other about 800 million years ago. Recent research by Zhiyu Duan suggests that M65 may also have interacted, though much less strongly. He also notes that M65 may have a central bar—it is difficult to tell because the galaxy is seen from an oblique angle—a feature which is suggestive of tidal disruption.

Source: https://en.wikipedia.org/wiki/Messier_65

M66 (NGC 3627): The largest and brightest of the group (9.0 mag). The image reveals a clear asymmetry in its spiral arms. This is a direct result of gravitational “tugging” by its neighbor, NGC 3628. The core is offset, and the dust structure is disturbed – evidence of a turbulent dynamic past.

Huge amounts of dust and numerous bright star clusters are found along the galaxy’s vast spiral arms.

Four supernovae have been observed in this galaxy so far: SN 1973R, SN 1989B, SN 1997bs.

Source: https://en.wikipedia.org/wiki/Messier_66

NGC 3628 (The Hamburger Galaxy): Seen perfectly edge-on. Its most characteristic feature is the massive dust lane cutting across its equator. This galaxy has suffered the most from the gravitational encounter – its disk is visibly puffed up and distorted at the extremities. The NGC 3628 – also known as the Hamburger Galaxy or Sarah’s Galaxy, is an unbarred spiral galaxy about 35 million light-years away in the constellation Leo. It has an approximately 300,000 light-years long tidal tail. Along with M65 and M66, NGC 3628 forms the Leo Triplet, a small group of galaxies. Its most conspicuous feature is the broad and obscuring band of dust located along the outer edge of its spiral arms, effectively transecting the galaxy to the view from Earth.

Due to the presence of an x-shaped bulge, visible in multiple wavelengths, it has been argued that NGC 3628 is instead a barred spiral galaxy with the bar seen end-on. Simulations have shown that bars often form in disk galaxies during interactions and mergers, and NGC 3628 is known to be interacting with its two large neighbors.

Source: https://en.wikipedia.org/wiki/NGC_3628

Engineering Challenge

The Tidal Tail The main challenge in processing this data is not just showing the galaxies, but preserving detail in the dark dust lane of NGC 3628 while avoiding overexposure of the M65 and M66 cores. Deep exposure (long integration time) allows, under favorable conditions, the capture of the faint “tidal tail” extending from NGC 3628 – a stream of stars ripped from the galaxy by the gravity of M66 approximately 800 million years ago.

Technical Summary

The image demonstrates the morphological diversity of spiral galaxies depending on their inclination angle relative to the observer: from “face-on” (M66), through an intermediate angle (M65), to “edge-on” (NGC 3628).

Lights taken at 14/15-3.2020 near Bielsko-Biała city.

Composition: Astro Pixel Processor v1.8,
Processing: GIMP v2.10.30 + plug-ins (Linux),
Lights: 44 x 180[s] ISO-800,
Darks: 15 ISO-800,
Bias: 20 ISO-800

Merope Nebula (NGC 1435) – The Physics of Blue Dust in the Pleiades

PekDar — Sat, 13 Aug 2022 07:30:57 +0000

A Lighthouse in the Fog

This image reveals a fragment of one of the most dynamic regions of the M45 cluster (The Pleiades). While the bright stars draw the eye, the key engineering and physical object here is the matter surrounding them – The Merope Nebula (NGC 1435). The smaller stars visible in the frame, identified as HD 23463 (spectral type K2) and HD 23479 (type B9), serve as excellent reference points for analyzing the density and structure of the surrounding dust clouds.

The Physics

Why Blue? This area is a textbook example of a reflection nebula. Unlike emission nebulae (which emit their own light, typically red from H-alpha hydrogen), here we observe a scattering mechanism.

Carbon and silicate dust grains act like billions of microscopic mirrors.
Light from the nearby, powerful star Merope (just outside the frame or at the edge) is scattered.
Shorter wavelengths (blue) are scattered much more efficiently than red ones (a phenomenon identical to what gives Earth’s sky its blue color).

Image and Structure Analysis

Stars HD 23463 and HD 23479 appear to be “suspended” in a delicate mist. In reality, the Pleiades are currently “passing through” an unrelated cloud of interstellar dust with a relative velocity of about 11 km/s. In the image, note the filamentary structure of the nebula. These filaments align with magnetic field lines and are shaped by the radiation pressure of nearby B-type giants. Capturing these subtle striations required high local contrast and precise denoising to avoid destroying detail in the shadows.

Star HD 23463

Look into the enlarged corner photo the star one above is orange. Distance from earth: 432.24 light years. The star surface temperature is estimated in the range of 3700–5200 [K]. It does not belong to the constellation Taurus, its close on its border. Invisible for the naked eye, you need binoculars or a telescope to see it.

Star spectral class: K2 – its mass relative to the sun is 0.45 to 0.8 . So, it is “smaller” than our sun. The number of stars of this class is in the 12%, of the main sequence, so when we look on the sky, these stars occur quite frequently. When we look at the spectrum of a star, we will notice that these types of stars, have significant metal lines, where in astronomy we call metal with element heavier than helium.

Star HD 2347

It is a variable, eruptive star, blue in color. Distance from earth: 440.76 light years. It is estimated that its surface temperature is in the range of 7,500 and 10,000 [K]. For comparison, our sun has a surface temperature of around 5.770 [K]. So, it can be even twice as hot as our sun.

The spectral class of the star: A – The mass relative to the sun is 1.4 to 2.1 times greater. This type of stars only quantitatively feeds 0.6% of the main sequence. They are clearly visible in the sky. Sirius and Vega belongs to the type A main sequence stars.

On the enlarged photo it is below, right next to the HD 23463 star.

HD 23463 and HD 23479 – crop

Main sequence stars: https://en.wikipedia.org/wiki/Main_sequence

Diagram Hertzsprunga-Russella: https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram

Technical information

Location: 12.2020
Composition: APP
Processing: APP, RawTherapee, GIMP + add-ons (Linux)
Summary exposure: 6h
Calibration frames: Darks, Bias, Flats

IC 1805 (Heart Nebula) – H II Region and Stellar Wind Sculpting

PekDar — Sat, 16 Jul 2022 17:05:00 +0000

Anatomy of a Giant

IC 1805, commonly known as the Heart Nebula, is in reality a vast star-forming region (H II region) spanning nearly 2.5 degrees across the sky (equivalent to five full Moons). Located approximately 7500 light-years from Earth in the Perseus Arm of our galaxy, this nebula is a classic example of the interaction between young, massive stars and their parent gas cloud.

The brightest part of the nebula (a knot at its western edge) is separately classified as NGC 896, because it was the first part of the nebula to be discovered. The nebula’s intense red output and its morphology are driven by the radiation emanating from a small group of stars near the nebula’s center. This open cluster of stars, known as Collinder 26 or Melotte 15, contains a few bright stars nearly 50 times the mass of our Sun, and many more dim stars that are only a fraction of our Sun’s mass.

The Engine

Melotte 15 The key to understanding this image lies at the very center of the nebula. The bright open cluster visible in the core is Melotte 15. It contains several ultra-massive O-type stars (with masses reaching up to 50 times that of the Sun). This is not a peaceful neighborhood. These stars emit powerful stellar winds and intense UV radiation.

Excavation: The stellar wind has literally “blown out” the gas from the center of the nebula, creating the characteristic void around the cluster.
Ionization: UV radiation strips electrons from hydrogen atoms in the surrounding cloud. When these electrons recombine (drop to lower energy levels), they emit photons at a specific wavelength – primarily the H-alpha line ( $656.28 \text{ nm}$ ). It is this physical process that accounts for the deep red color dominating the image.

Dust Structures and “Elephant Trunks” Contrasting with the bright hydrogen plasma, dark lanes of interstellar dust (silicates and carbon) are visible in the image. Note the pillar-like structures (often called “elephant trunks”) pointing towards the center. These are denser pockets of gas and dust that are resisting the destructive force of the stellar wind from Melotte 15. Inside these dark cocoons, processes of gravitational collapse are still ongoing – new stars are being born there.

Technical Aspect

Capturing IC 1805 required a camera sensitive to the H-alpha band or a modified DSLR/Mirrorless, as standard infrared cut filters in consumer equipment block most of the signal from this object. Due to its enormous angular size, this image required either short focal length optics or a mosaic technique.

On the left side of the photo you can see an interstellar dust (grey, dark grey).

The photo is the result of combining two different photo sessions but in the same location. The frame is not proportional, it is too wide. However, I didn’t want to crop it because of the interstellar dust revealing on the left side of the frame. Personally, I liked this photo very much and I think it is better than the previous one, which was made only from one photo session.

IC 1805 – Heart Nebula

Source: https://en.wikipedia.org/wiki/Heart_Nebula

Technical information

Date: 12.2020
Composition: APP
Processing: APP + RT + GIMP + add-ons (Linux)
Total exposure time minus defective light frames: 4h 36min.
Lights: 276
Calibration frames: Flats, Bias, Darks

IC 1848 (Soul Nebula) – Westerhout 5 and Triggered Star Formation

PekDar — Sat, 16 Oct 2021 14:10:11 +0000

A Ghost in the Radio Telescope

To the modern astrophotographer, this object is known as the “Soul Nebula” due to its shape accompanying the nearby “Heart”. However, to science, it is primarily Westerhout 5 (W5). It was first cataloged in the 1950s by Dutch astronomer Gart Westerhout, not with an optical telescope, but with a radio telescope. W5 is a strong source of radio emission, indicating the presence of vast amounts of ionized gas, invisible to the human eye but perfectly captured by modern sensors in the Hydrogen-alpha band.

IC 1848 Soul Nebula is a vast, beautiful emission nebula located in the constellation Cassiopeia. It is often paired with its neighbor, the Heart Nebula (IC 1805), forming the famous “Heart and Soul” complex. Stretching over 100 light-years, the Soul Nebula’s distinctive glowing structures are sculpted by the intense radiation from young, hot stars that have formed within it. Due to its striking appearance, IC 1848 is a popular and rewarding target for astrophotography, particularly when using narrowband filters (e.g., $H\alpha$ , $OIII$ , and $SII$ ).

IC 1848 – Sould Nebula – reduced stars brightness

6000 light years away from Earth and is located in the Perseus Arm of the Galaxy in the constellation Cassiopeia. It is an emission nebula showing glowing ionized hydrogen gas.

IC 1848 (also OCL 364) is also used to describe the open cluster associated with the Soul Nebula, that highlights the nebula. Its brightness is 6.5 magnitude.

The Soul Nebula is related to the Heart Nebula (IC 1805). Both mentioned nebulae, cover an area of approximately 300 light-years. They both emit bright red light from hydrogen emmision.

Structure: Cosmic Bubbles

Looking at the image, you are not seeing a flat patch, but three-dimensional cavities. This nebula consists of giant bubbles carved out of the interstellar medium.

The Center: Massive stars of the IC 1848 cluster reside here.
The Mechanism: Their stellar winds and radiation “clear” the space around them, pushing material outward.
The Edges: It is there, at the boundaries of these bubbles (visible as brighter, high-contrast rims in the image), that the gas is compressed.

Triggered Star Formation This image documents a process of “generational relay”. The pressure exerted by massive stars from the center compresses the gas at the nebula’s periphery. Within these compressions, gravitational collapse occurs, leading to the birth of new stars. Particularly in the eastern part of the nebula (often called the “Head” or “Embryo”), astronomers have identified numerous EGGs (Evaporating Gaseous Globules) – dense gas cocoons where protostars are still forming, shielded from the destructive UV of their older neighbors.

Photographic Challenge

IC 1848 is an object of lower surface brightness than the neighboring Heart Nebula. It requires longer integration time to bring out the subtle dust structures inside the “bubbles”, not just the bright rims. A key step here is separating the nebular signal from the dense star field of the Milky Way in Cassiopeia (star reduction) to emphasize the gas structure.

IC 1848 – Soul Nebula

Source: https://en.wikipedia.org/wiki/Westerhout_5

Technical information – photo tips

Date: 12.2020
Composition: APP
Processing: APP + RT + GIMP + add-ons (Linux)
Total exposure time minus defective light frames: 4h 36min.,
Lights: 238
Calibration frames: Flats, Bias, Darks

IC 1805 – Heart Nebula

PekDar — Fri, 01 Oct 2021 16:06:37 +0000

7500 light years away from Earth and is located in the Perseus Arm of the Galaxy in the constellation Cassiopeia. It is an emission nebula showing glowing ionized hydrogen gas and darker dust lanes.

Dimmed stars I’ve made with GIMP software.

IC 1805 – Heart Nebula – dimmed stars

Source: https://en.wikipedia.org/wiki/Heart_Nebula

Technical information

Date: 12.2020
Composition: APP,
Processing: APP + RT + GIMP + add-ons (Linux),
Total exposure time minus defective light frames: 4h 36min.,
Lights: 238,
Calibration frames: Flats, Bias, Darks

Melotte 15 – The Ultramassive Stars Driving the Heart Nebula (IC 1805)

PekDar — Sat, 25 Sep 2021 12:50:23 +0000

The Heart in the Heart The Melotte 15

Melotte 15 cluster is the energetic core of the vast emission complex IC 1805 (the Heart Nebula). Rather than being just a collection of bright points, it is an astrophysical laboratory demonstrating how massive stars sculpt matter on a galactic scale. The cluster is exceptionally young – its age is estimated at only 1.5 million years, making it one of the youngest, actively studied regions in the Milky Way.

O-Type Stars: A Short and Turbulent Lifespan Key to understanding Melotte 15 are its brightest and most massive components, including several O-type giants and numerous B-type stars.

O-Type Stars: They are extremely hot (surface temperatures can exceed $40 000 \text{ K}$ ), possess immense masses (up to 50 solar masses), and live very short lives (only a few million years).
UV Emission: Due to their high temperature, they emit enormous amounts of ultraviolet (UV) radiation, which is the primary ionizing agent for the surrounding hydrogen gas, causing the characteristic red glow of IC 1805.
Stellar Wind: These stars also eject powerful stellar winds that have, like a giant broom, swept the gas out of the nebula’s center, creating the visible cavity around Melotte 15.

Located in the constellation Cassiopeia, approximately 6,000 light-years from Earth. It is an extremely young star cluster with an average age of 1.5 million years. Located very close to the center of the Heart Nebula, precisely it is about 50 light-years ahead of the nebula. Melotte 15, contains a few bright stars nearly 50 times mass of our Sun, and many more dim stars that are only a fraction of our Sun’s mass. Melotte 15 is one of the association core clusters Cas OB6. This cluster is more nebular in nature.

Melotte 15 – Open Cluster in the center of the Heart Nebula

Maturity and the End of the Cycle

The presence of such massive and hot stars means the cluster is currently experiencing its most intense period. However, its dominance won’t last long. O-type stars consume their nuclear fuel thousands of times faster than the Sun. Within the next few million years, they will exhaust their hydrogen and explode as supernovae, leading to the dispersal of the remaining nebula and the eventual break-up of the cluster itself.

Technical Challenge: Brightness Balance

Astrophotography of Melotte 15 presents a challenge because the brightness of these central, massive stars is thousands of times greater than the subtle nebular structures. This demands precise HDR (High Dynamic Range) processing and careful reduction of the star halos to avoid “blowing out” their cores while simultaneously preserving detail in the background.

Own translation based on source: https://pl.wikipedia.org/wiki/Melotte_15

Technical information

Date: 12.2020
Composition: APP,
Processing: APP + RT + GIMP + add-ons (Linux),
Total exposure time minus defective light frames: 4h 36min.
Lights: 238
Calibration frames: Flats, Bias, Darks

The Horsehead Nebula Complex: Barnard 33, IC 434, and the Flame Nebula (NGC 2024) – An Astrophysical Analysis

PekDar — Fri, 17 Sep 2021 16:55:42 +0000

The Laboratory of Gravity and Radiation

The Horsehead Nebula Complex, located within the constellation of Orion, is one of the most important and instructive regions in our Galaxy. Situated at a distance of approximately 1500 light-years from Earth, it serves as the closest active star-forming zone to us, providing a textbook laboratory for interstellar physics.

This image focuses on the dynamic interaction of three fundamental types of cosmic matter that coexist within a single frame:

Emission Nebulae (IC 434, NGC 2024), which emit light due to hydrogen ionization.
Dark Nebulae (Barnard 33), which absorb light, forming dense, cold cocoons.
Reflection Nebulae (NGC 2023), which merely reflect and scatter light from a nearby star.

The primary engine and sculptor of this region is ultraviolet (UV) radiation, emitted by massive, short-lived stars such as Alnitak ( $\zeta$ Orionis) and Sigma Orionis. Their energy creates powerful stellar winds and generates shockwaves that, over millions of years, erode and compress the parent clouds of gas and dust. Consequently, this image is a visual record of the ongoing cycle of cosmic destruction and creation.

Three Nebula Types in One Frame

The Orion Complex serves as a laboratory showcase, demonstrating how the powerful ultraviolet (UV) radiation from nearby massive stars—such as Sigma Orionis and Alnitak—affects the structure and luminosity of the interstellar medium. In this single frame, we witness textbook examples of three fundamental mechanisms of light-matter interaction.

The Emission Background: IC 434 (Hydrogen Ionization)

The bright, red background dominating the frame is IC 434—a gigantic cloud of hydrogen. This is a classic emission nebula (H II region), which does not reflect light but rather emits its own light through the process of electron recombination.

Mechanism: High-energy UV light, originating from the distant but incredibly powerful star Sigma Orionis, strips electrons from hydrogen atoms. When these electrons “recombine” (drop back to lower energy levels), they emit a photon.
Color/Signature: This process is responsible for the characteristic deep red glow seen in images, dominated by the H-alpha line ( $656.28 \text{ nm}$ ).
Crucial Role: IC 434 acts as the “projection screen” for the Horsehead Nebula (Barnard 33). Without this emission background, the dark silhouette of B33 would be invisible.

Barnard 33 (Dust Erosion)

The distinctive black silhouette shaped like a chess piece is Barnard 33. This is a dark nebula—one of the most famous molecular clouds in the Milky Way.

Mechanism: Barnard 33 is not a lack of matter, but an extremely dense, cold molecular cloud of dust and gas that is too thick to let light from IC 434 pass through. The cloud actively absorbs light from behind it, creating the high-contrast silhouette.
Shape and Erosion: The specific “horsehead” shape is the result of photoevaporation. The intense UV radiation from IC 434 (which ionizes hydrogen) simultaneously destroys and evaporates the outer layer of B33.
Future: Barnard 33 is a remnant: its density allows for star formation within its core, but it is being gradually “eaten away” by the radiation of its stellar neighbors.

The Flame Nebula (NGC 2024)

Dominates the right side of the frame. Similar to IC 434, it is an emission region, but its dynamics are more violent due to the proximity of its energy source.

Power Source: It is ionized by the nearby star Alnitak ( $\zeta$ Orionis), the easternmost star of Orion’s Belt, though Alnitak itself is not located in the nebula’s core.
Structure: The UV light from Alnitak is so intense that the nebula appears to be “burning” toward the star. The characteristic dark filaments are dense dust positioned in front of the brighter emission gas.
Star Formation: Behind these dark filaments in the Flame Nebula, astronomers have detected numerous protostars—the Flame is one of the most active and closest star-forming regions to us.

The Reflection Nebula (NGC 2023)

The small, blue glow at the base of the Horsehead is NGC 2023. It is one of the brightest examples of a reflection nebula.

Mechanism: Unlike IC 434 (which emits its own light), NGC 2023 merely reflects the light from a star located within its core (HD 37903).
Color/Physics: It glows blue because the process is the same one that gives the Earth’s sky its blue color—Rayleigh Scattering. Short wavelengths (blue) are scattered much more effectively by fine dust grains than long wavelengths (red).
Conclusion: This object completes the complex, demonstrating all three states of matter-radiation interaction: emission, absorption, and reflection.

ASAS 053739-0146.3 (USNOA2 0825-01610019) – Variable star

Spectral type: M9 (Red dwarf, coolest)

Surface temperature in the range: 2,400–3,700 K

IR – Infrared wave source

Mag: 15.35

Stars M class are most common. About 76% of the main sequence stars in the spectral band of the Sun (class G) are class M stars (red dwarfs), their brightness is so low, that it is impossible to see them with the naked eye, except under exceptional conditions.

The brightest known M class main sequence star is M0V Lacaille 8760, with magnitude 6.7 (the limiting magnitude for typical naked-eye visibility under good conditions is typically quoted as 6.5). So, it’s very unlikely that any brighter example of a class M star, will occurs anytime soon. But we can’t this completely ruled out.

As you can see in the example photo, with a telescope with a focal length of 420 [mm], brightness F2.8 and a sensitive RGB camera, by exposing a selected area of the sky long enough, you can register stars of the spectral type M (coolest red dwarfs) with very low brightness (15.35 mag) with a very clear presence in the entire frame.

It’s worth noting that red dwarfs burn out very slowly, which means they can be very, very old compared to other types of stars.

Technical information

Date: 12.2020
Composition: APP
Processing: APP, RawTherapee, GIMP + add-ons (Linux),
Lights: 170 x 60[s] (2h 50min.),
Calibration frames: Flats, Bias, Darks.

Own study based on sources:

– https://en.wikipedia.org/wiki/Stellar_classification

– https://en.wikipedia.org/wiki/Stellar_classification#Class_M

– https://astrobackyard.com/types-of-stars/#:~:text=%20The%207%20Main%20Spectral%20Types%20of%20Stars%3A,Arcturus%29%207%20M%20%28Red%29%20%28%20Betelgeuse%29%20More%20

– https://en.wikipedia.org/wiki/Flame_Nebula

– https://en.wikipedia.org/wiki/NGC_2023

– https://en.wikipedia.org/wiki/Horsehead_Nebula

Stars over Teide – Tenerife 2019 (night‑sky time‑lapse)

PekDar — Fri, 25 Dec 2020 21:52:56 +0000

Stars over Teide – Tenerife 2019

This short night-sky time-lapse over Teide was created during the PTMA expedition to Tenerife in 2019. Composed of 140 frames, the sequence demonstrates the smooth motion of stars relative to Earth’s rotation over the volcanic landscape of Las Cañadas.

Why Teide Offers an Advantage Teide is Spain’s highest peak (approx. 3715–3718 m a.s.l.) and the heart of Parque Nacional del Teide, a UNESCO World Heritage site since 2007 – one of the most valuable volcanic landscapes in the world.

Observational conditions are shaped by the “Mar de Nubes” – a trade-wind inversion layer. Cool, moist air and clouds below “cut off” coastal light pollution, while above (over 2000 m a.s.l.), the air remains dry and stable. This results in a darker background and superior image stability (seeing).

The sky quality is also legally protected since 1988 by the “Ley del Cielo” (regulating outdoor lighting, radio emissions, and flight paths), which tangibly supports the observatories’ work. Nearby, at Izaña (approx. 2390 m), operates the Teide Observatory – a key European center for solar research and photometry. While the Atacama in Chile holds the global record for atmospheric dryness, Teide remains the reference site for astronomy in Europe.

Shot Parameters (Time-lapse)

Frames: 140 (compiled into 3 sequences; two played faster to visualize dynamics).
Location: Vicinity of the Las Cañadas caldera (Tenerife), approx. 2200 m a.s.l.
Phenomenon: Visible apparent motion of the celestial sphere due to Earth’s rotation.

Visual Analysis The footage is dominated by the concentric arcs of star motion over a raw, volcanic foreground. Near the low horizon, a slight glow from the cloud layer (“sea of clouds”) is visible – acting as a natural “filter” suppressing light pollution from the tourist towns below.

Sources / Further Reading

UNESCO – Teide National Park (WH status since 2007)
IAC – Teide Observatory (location, altitude)
Starlight / “Sky of Teide” (inversion, “sea of clouds”, certification)
Teide – elevation & context