A star cluster is a group of stars that are gravitationally bound to each other and have a common origin. They formed in the same region of a gas cloud and are therefore approximately the same age. There are two main types of star clusters: open clusters and globular clusters.

On 5 May 2025 I imaged M5, also known as NGC 5904. This globular cluster can be found in the constellation Serpens at a distance of 24,500 lightyears from Earth. It was discovered by Gottfried Kirch in 1702.

A short recording in LRGB of 4 hours and 20 minutes:

Processing done in APP, Topaz and PSP.

On hindsight the luminance should have been taken at 30s exposure time. Due to the relative brightness of this object of magnitude 5.6 the core seems a bit overexposed.

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On 2 November 2018, with the assistance of Rob Musquetier and Caspar Tielemans, the first deep-sky object was imaged from InFINNity Deck. Using the SkyWatcher Esprit 150ED and a ZWO ASI1600MM Pro Cool camera pictures with 60 and 120 seconds were taken of M13 (see figure 4), better known as Hercules globular cluster. In the same frame galaxy NGC6207 is visible as are bright stars HIP 81848 and HIP 81673. The images were taken at around 9pm UTC with the cluster at approximately 15 degrees altitude, which is quite low for proper imaging, but setting up equipment and sequences and waiting for cloud cover to open made M13 drop lower than anticipated. Nevertheless I think we done rather well for a first attempt under challenging conditions.

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On 2 and 4 June 2019 I revisited M13, now to add some colour to it. I did not use my previous luminance as those were made with quite a different orientation of the camera. The images were taken using the SkyWatcher Esprit 150ED APO and ZWO ASI1600MM Pro Cool camera. The previous version was the first deep-sky object I imaged, this time it is the first time that I used masks on the filters in the ZWO EFW filter wheel. A total of 2 hours of data was collected:

Processing done in APP, post-processing redone in 2022 in Siril and PSP.

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On 23 August 2021 I revisited M13 while testing the newly acquired SkyWatcher Esprit 80ED. I made a quick recording in LRGB of 40 minutes:

Processing done in APP, post-processing redone in 2022 in Siril and PSP.

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The upper-left and lower-right corners of the image show elongated stars, caused by some optical defect in the telescope (astigmatism?). The scope was returned and replaced by a new one which does not show this effect.

On 8 August 2019 I imaged M15 in the constellation Pegasus, another globular cluster from the Messier list. The images were taken using the SkyWatcher Esprit 150ED APO and ZWO ASI1600MM Pro Cool camera. The brightest stars accompanying the cluster are HIP106157 (white), HIP106075 (orange, upper left) and HIP106243 (blue). A total of 1 hour of data was collected:

Processing done in APP, post-processing redone in 2022 in Siril and PSP.

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On 7 and 8 September 2021 I spent some time on Messier 29, also known as NGC 6913 (see figure 18), using the SkyWatcher Esprit 150ED APO and ZWO ASI1600MM Pro Cool camera. A total of 11 hours and 52 minutes of data was collected:

Processing done in APP, post-processing redone in 2022 in Siril, PSP and Topaz.

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On 16 February 2025 I collected data of two open clusters in the constellation of Gemini: M35, better known as the Shoe-Buckle Cluster, and NGC 2158. Imaging was done with the SkyWatcher Esprit 150ED, ZWO EFW with ZWO LRGB filters and ZWO ASI1600MM Pro Cool in LRGB, with three hours of luminance (180s subs) and 60 minutes per R, G and B (30s subs per channel), a total of exactly six hours of data. Everything unguided as always.

Processing done in APP, post-processing in PSP, Siril and Topaz.

The two clusters are not related. M35 is at a distance of 2970 lightyears from us, NGC2158 more than 11,000 lightyears. M35 seems to be a globular cluster, but it is now known to be an intermediate-age, metal-poor open cluster.

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The night of 13 February 2023 I had a visit from the namesake of our observatory, together with his sister and a friend. Using the C11 we spent more than an hour looking at various objects in the sky like Venus, Jupiter, Mars, C/2022 E3 (ZTF), M94, M44, M35, M31, M42 and this one, M37. Being an open cluster with may bright stars it is a very nice object at the eyepiece, so when the observing session ended at about nine o'clock, I set the SkyWatcher Esprit 150ED to work and took the following series of subs of M37:

Processing done in APP, post-processing in PSP.

M37 is an open cluster in the constellation Auriga, not far from where I last photographed comet C/2022 E3 (ZTF). The cluster has been identified before 1654 by the Italian astronomer Giovanni Battista Hodierna, but was eventually catalogued by Charles Messier in September 1764, and as a result the cluster is now called M37.

The distance to Earth is about 4500 light years, which means that the diameter is about 20-25 light years. There are 500 identified stars in the cluster, 150 of which are brighter than magnitude 12.5. The bright orange star at the top left is HIP27661.

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Messier 39 is an open cluster also known as NGC 7092 and is located in the direction of Cygnus at a distance of about 1010 light years from us. M39 was discovered in 1749 by the French astronomer Guillaume Le Gentil and in 1764 by his French colleague Charles Messier added to the well-known list of Messier objects.

Captured with the SkyWatcher Esprit 150ED, ZWO EFW with ZWO LRGB filters and ZWO ASI1600MM Pro Cool, all unguided on the 10Micron GM3000HPS.

A total of just under five hours of data (4h52m) was collected:

Processing done in APP, post-processing in PSP.

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On 1 April 2024 I decided to give Messier 67 a try. The cluster is also known as King Cobra Cluster or the Golden Eye Cluster and can be found in the souther part of Cancer, some 2600-2900 lightyears from Earth.

Imaging was done with the SkyWatcher Esprit 150ED APO and ZWO ASI1600MM Pro Cool camera (see figure 10). I just needed a bit of data as course-material to explain APP, so decided to only collect 2.5 hours of data:

Processing done in APP, post-processing in Siril, PSP and Topaz.

After processing I noticed a RGBL-trail below the cluster. Using MPChecker I found out it was Asteroid (38) Leda, a rock 116km in diameter in an orbit between Mars and Jupiter. An animation of (38) Leda can be found in the Solar System (Asteroids) section.

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On 20 August 2023 data was collected from double cluster NGC 869 and NGC 884. The double cluster is located in the constellation of Perseus at a distance of 7460 light years from Earth and is about 14 million years old.

A total of 2 hours and 15 minutes was spent on this galaxy:

Captured using NINA with the SkyWatcher Esprit 80ED in combination with the ZWO EFW filter wheel, ZWO LRGB filters and ZWO ASI1600MM Pro Cool camera @ -10°C. Processing in APP 2.00, post-processed in Siril, PSP and Topaz.

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On 14 September 2023 I imaged Kemble's Cascade that leads to the open cluster NGC1502 at approximately 3500 light-years in the direction of the constellation of Camelopardalis. NGC1502, at the lower left corner of the image, was discovered by William Herschel on 3 November 1787. The Cascade was introduced by Father Lucian Kemble (1922–1999), a Franciscan friar and amateur astronomer who wrote a letter about it to Walter Scott Houston, an American popularizer of amateur astronomy. Kemble called it "a beautiful cascade of faint stars tumbling from the northwest down to the open cluster NGC 1502". Houston in turn wrote an article about the asterism in Sky & Telescope and coined the asterism Kemble's Cascade.

Imaging was done in LRGB, a total of six hours and forty minutes of data was collected for this galaxy:

Captured with the SkyWatcher Esprit 80ED in combination with the ZWO EFW filter wheel, ZWO LRGB filters and ZWO ASI1600MM Pro Cool camera @ -10°C. Processing in APP, post-processing in Siril, PSP and Topaz DeNoise AI.

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On 21 September 2022 NGC2360, better known as Caroline's Cluster, an open cluster at 3700 light-years in the direction of the constellation of Canis Major, was imaged. It was discovered by William Herschel's sister Caroline Herschel on 26 February 1783.

Imaging was done in LRGB, a total of seven hours and one minute of data was collected for this galaxy:

Captured with the Esprit 150ED in combination with the ZWO EFW filter wheel, ZWO LRGB filters and ZWO ASI1600MM Pro Cool camera @ -20°C. Processing in APP, post-processing in Siril, PSP and Topaz DeNoise AI.

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During the night of January 9 to 10, the SkyWatcher Esprit 150ED was aimed at NGC2419, better known as Caldwell 25 (C25, bottom right of the photo), for an entire night of imaging. NGC2419 is nicknamed The Intergalactic Wanderer. The name is due to the incorrect assumption that, at a distance of approximately 300,000 light years, this globular cluster was not part of the Milky Way. Although it is located at a greater distance than the Magellanic Clouds, it is indeed 'caught' in the gravity of our Milky Way, but due to the enormous distance, a circle around the centre takes about 3 billion years.

Like many objects, it was discovered by William Herschel, in this case on the last day of 1788. Its absolute magnitude is -9.42 and it contains a mass 900,000 times that of the Sun. NGC2419/C25 is located in the constellation Lynx.

Imaging was done with the Esprit 150ED, ZWO EFW with ZWO LRGB filter set and ZWO ASI1600MM Pro Cool. A total of 10 hours and 20 minutes of data was recorded:

Processing in APP, post-processing in Siril, PSP and Topaz DeNoise AI.

The galaxy at the upper left is NGC2424, a barred spiral galaxy discovered on February 6, 1885, by French astronomer Édouard Jean-Marie Stephan. In addition, dozens of other galaxies are visible in the background, as can be seen in the ASTAP annotated version.

Click here for the full image and here for the annotated version.

After having imaged NGC2264 on 12 February 2021, some time was left for a second object. Being a moon-less night, it was perfect weather for a LRGB-object, which became NGC5466, also known as the Snow-Globe Cluster or Ghost Globular Cluster due to its lack of stars towards the centre of it. Four hours of data was collected in LRGB: 60s subs for luminance, 120s subs for the rest.

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This object, an open star cluster in the constellation Lyra, was imaged shortly before and after summer 2025. In May RGB was collected, while in August luminance was added. NGC6791 is located 13,300 light years away. It was discovered in 1853 by German astronomer Friedrich August Theodor Winnecke.

A total of 7 hours and 22 minutes was spent on this galaxy on 15 May and 20 August:

Captured with the SkyWatcher Esprit 150ED in combination with the ZWO EFW filter wheel, ZWO LRGB filters and ZWO ASI1600MM Pro Cool camera @ -15°C. Processing in APP, post-processing in PSP and Topaz.

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The last object imaged before the summer 2025 recess was NGC6811, an open cluster located 3,600 light years away in the Cygnus constellation. It was discovered by John Herschel on 29 August 1829. A total of 6 hours was spent on this galaxy on 13 and 19 May 2025:

Captured with the SkyWatcher Esprit 150ED in combination with the ZWO EFW filter wheel, ZWO LRGB filters and ZWO ASI1600MM Pro Cool camera @ -15°C. Processing in APP, post-processing in PSP and Topaz.

Click here for the full image.

One of the last objects imaged before the summer 2025 recess was NGC6819, an open cluster located 7,200 light years away in the Cygnus constellation. It was discovered by Caroline Herschel on 12 May 1784. A total of 5 hours was spent on this galaxy on 3 and 12 May:

Captured with the SkyWatcher Esprit 150ED in combination with the ZWO EFW filter wheel, ZWO LRGB filters and ZWO ASI1600MM Pro Cool camera @ -15°C. Processing in APP, post-processing in PSP and Topaz.

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In the night of 11 to 12 August 2024 clear skies allowed for a short target. Having about 5 hours of imaging time available I decided to give NGC 6910, also known as the Inchworm Cluster, a try. This galaxy lies at a distance of 3710 light-years in the direction of Cygnus and was first seen by WIlliam Herschel on 17 October 1786.

A total of 5 hours and 15 minutes was spent on this galaxy:

Captured using NINA with the Esprit 150ED in combination with the ZWO EFW filter wheel, ZWO LRGB filters and ZWO ASI1600MM Pro Cool camera @ -10°C. Processing in APP, post-processing in PSP and Topaz.

Click here for the full image.