Welcome to Astrosite Groningen. On these pages you mainly find information, and a presentation of results, on a number of astronomical subjects that we find most interesting. Our main interests are comets and variable stars; therefore, emphasis will be on the various aspects of observing these objects (charts, observations, photographs). But we also plan to cover other topics, albeit only as an aside, such as eclipses, and atmospheric phenomena like aurora and noctilucent clouds, mainly by presenting a selection of our photographic results. We hope you enjoy this site. We always welcome comments, and suggestions for improvement. And feel free to contribute: observations, images, whatever you want to share... Reinder J. Bouma Edwin van Dijk

Minor planet 9706 on August 17, 2002 in NEAT images.

Recent updates (over the last month)
Oct. 17, New APASS file for October/November. Observations and images of C/2023 A3.
Oct. 12, Observations of C/2023 A3 and C/2024 S1. New chart for C/2023 A3.
Oct.  6, Observations of C/2023 A3, C/2024 S1 and 13P.
Sep. 25, Observations of C/2023 A3 and 13P.
Sep. 21, Observations of C/2023 A3.


SQM-L sky brightness measurements at our observing sites. Click here.


Visually observable comets
Comet
Mv
Trend
Charts
covered by APASS file
C/2020 V2 (ZTF)
14-15
fading
no
yes
C/2022 E2 (ATLAS)
12-13
near maximum
no
yes
C/2022 N2 (PANSTARRS)
14-15
near maximum
no
yes
C/2023 A3 (Tsuchinshan-ATLAS)
3-4
fading
yes
no
C/2023 C2 (ATLAS)
13-14
near maximum
no
yes
C/2024 B1 (Lemmon)
14
near maximum
no
yes
C/2024 G3 (ATLAS)
14?
brightening
no
yes
C/2024 S1 (ATLAS)
??
small elongation, brightening?
no
no
12P/Pons-Brooks
13
fading
no
yes
13P/Olbers
10
small elongation, fading
no
yes
29P/Schwassmann-Wachmann 1
-
regular outbursts
no
yes
37P/Forbes
14
near maximum
no
yes
333P/LINEAR
14
brightening
no
yes

NEW! October 17, a new file with comparison stars from APASS in the magnitude 10-15 range is available for the October/November
        moonless period.


Bright comet C/2023 A3 (Tsuchinshan-ATLAS) in the evening sky

This comet, after being briefly visible in de morning sky for southern observers as a 2nd magnitude comet with a long dust tail, has now become an evening object 
best placed for northern hemisphere observers, with visibility improving every day now that the elongation is increasing again.

The comet briefly peaked at magnitude -4 on October 9 due to forward scattering, but at an elongation of a mere 4 degrees from the Sun was virtually 
invisible for earthbound observers.
However, the situation improved rapidly over the following days although the situation was still far from ideal with the comet in twilight very low over 
the western horizon, and a bright near full Moon to boot.
But over the coming days the situation will improve further. After October 20 the comet can be observed in a dark sky near the end of evening twilight 
without lunar interference. Although the comet now is moving away from both the Earth and the Sun and gradually fading it is expected that it will still 
show a long dust tail, which under the best conditions may still be some 20 to 30 degrees long. By the time the Moon is starting to interfere again 
during the second week of November the show will be virtually over.
Nevertheless observers with proper equipment will be able to follow this comet until the end of the year. By that time it probably will have faded to 
magnitude 10 or so and gradually disappear in evening twilight.


On October 14 the Earth was predicted to pass the orbital plane of the comet, and the geometry was perfect for observation of an anti-tail.
Fortunately that day brought clear skies for us, albeit with considerable lunar interference.
The image at upper right was taken close to my observing site near Westerwijtwerd by Iris Veronique Mulder with a Canon EOS R10. 
It is a 8s exposure at ISO400 with a 40mm f/5 lens taken at 18:07UT and is a good representation of the naked eye view.

A larger version of this image can be viewed by clicking here.
The close-up image at lower right was taken at the Aekingerzand near Wateren by Rik ter Horst at 18:05UT.
It is a 3s exposure at ISO1600 using a Sony A7III camera equiped with a Canon 100mm f/2 lens, and is a good representation of the view in (larger) 
binoculars. Note the very faint anti-tail pointing at lower right opposite the main dust tail.
A larger version of this image can be viewed by clicking here.


[RJB17102024]





Comet C/2021 A1 (Leonard) at perihelion

This comet, discovered a year ago as the first one of 2021 is passing perihelion today.
Over the last couple of weeks it has developed into a very fine object in the evening sky, in particular for observers in the southern hemisphere.
It is very active, producing modest brightness outburst every 4 days or so since the middle of december, and showing a spectacular tail in wide
field images, unusual for a comet that never became brighter than about magnitude 3-4 in a dark sky. A good example is the image above which was
taken less than 24 hours from perihelion by Michael Mattiazzo from SWAN Hill, NSW. Currently the comet is about magnitude 5 visually.
It is expected to fade gradually over the coming weeks moving away from both the Earth and the Sun.  [03-01-2022]


Bright comet C/2020 F3 (NEOWISE)!

This comet, discovered on March 27 by the NEOWISE satellite as a magnitude 17 object, brightened to 7th magnitude for southern hemisphere observers
before disappearing in evening twilight en route to perihelion on July 3 at slightly under 0.30 AU from the Sun. In the meantime it had become evident that this
was an 'old' object, and there was good hope that northern hemisphere observers would see a naked eye comet near about magnitude 3 deep in morning twilight shortly
after perihelion. So it was a pleasant surprise that C/2020 F3 actually emerged as a first magnitude object sporting a bright dust tail that rapidly grew longer
and longer over the last week as the comet could be seen higher above the horizon in a darker sky.
The (binned) image to the right was obtained on the early morning of July 12 by Martin Mobberley from Cockfield, Suffolk, UK and is a fair representation
of what visual observers were able to see around the same time.

A full version of this image including observing details can be viewed by clicking here.
Over the coming weeks comet NEOWISE, now placed in the evening sky, will fade fairly rapidly after its closest approach to the Earth - the minimum
distance was 0.692 AU around 23.0 July - moving south and becoming better placed for more southerly observers.







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