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)
Feb.  5, New APASS file for February/March. Observations of C/2017 K2, C/2019 L3, C/2019 T4, C/2019 U5, C/2022 A2, C/2022 E3 and 81P.
Jan. 31, Observations of C/2017 K2, C/2020 V2, C/2022 A2, C/2022 E3, C/2022 U2 and 29P. New charts for C/2017 K2, C/2022 A2 and C/2022 E3.
Jan. 22, Observations of C/2017 K2, C/2020 V2, C/2022 A2, C/2022 E3 and C/2022 U2.
Jan. 18, Observations of C/2017 K2, C/2020 V2, C/2022 A2, C/2022 E3 and C/2022 U2. Charts for C/2022 A2.
Jan.  6, New APASS file for January/February. New charts for C/2017 K2 and C/2022 E3. Observations of C/2019 U5, C/2020 V2, C/2022 A2, C/2022 E3, C/2022 U2 and 29P.


SQM-L sky brightness measurements at our observing sites. Click here.
Visually observable comets
CometMvTrendChartscovered by APASS file
C/2017 K2 (PANSTARRS)8-9near maximumyesno
C/2019 L3 (ATLAS)11-12fadingnoyes
C/2019 T4 (ATLAS)13-14near maximumnoyes
C/2019 U5 (PANSTARRS)12-13brighteningnoyes
C/2020 K1 (PANSTARRS)12-13brighteningnoyes
C/2020 S4 (PANSTARRS)14-15?brighteningnoyes
C/2020 V2 (ZTF)9-10near maximumnoyes
C/2021 T4 (Lemmon)14-15brighteningnoyes
C/2021 X1 (Maury-Attard)14-15near maximumnoyes
C/2021 Y1 (ATLAS)14near maximumnoyes
C/2022 A2 (PANSTARRS)9-10fadingyesyes
C/2022 E3 (ZTF)5-6fadingyesno
P/2022 P1 (NEOWISE)12?fadingnoyes
C/2022 U2 (ATLAS)10-11fadingnoyes
29P/Schwassmann-Wachmann 1-regular outburstsnoyes
77P/Longmore14-15brighteningnoyes
81P/Wild 212-13fadingnoyes
96P/Machholz 110-11fadingnoyes
118P/Shoemaker-Levy 414fadingnoyes
237P/LINEAR14brighteningnoyes
NEW! January 6, a new file with comparison stars from APASS in the magnitude 10-15 range is available for the January?February moonless period.

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.




Click here for older news items.



update 05-02-2023