The COVID-19 curfew in the Netherlands made the winter of 2020-2021 especially long. Not only you were working at the home office for months, but all the shops (besides supermarkets, groceries, and pharmacies) were closed as well. During the evening you were not supposed to leave your own house unless you were letting a house pet out. Family and friends were all just familiar faces on the computer monitor. Luckily, we started our astrophotography hobby not long ago. But still, we could have used some excitement. Our idea has always been to connect our hobbies astronomy and travel, but we had no chance of doing this kind of astrophotography under curfew.
A new star appears
On the 18th of March 2021, a Japanese amateur astronomer Yuji Nakamura noticed a new star in the constellation Cassiopeia. In the following days, it brightened further, to be easily visible with small telescopes, and remained more or less constant in brightness afterward. Detailed analysis showed the newcomer was a classical nova, a type of cataclysmic variable star well-known to astronomers. It got a standard variable star name as well: V1405 Cas. Novae occur when a white dwarf star has accreted too much gas from its companion star, and this results in a runaway thermonuclear reaction on its surface. What made this event special is the lovely location in a beautiful part of the Milky Way. Nova Cassiopeia appears in a rich see of stars, next to the M52 open cluster, and the stunning Bubble Nebula. A perfect scene for astrophotography!
Astrophotography adventures under curfew
Except that Cassiopeia was low on the northwest horizon after sunset, blocked by the neighbor’s house. Our gear is reasonably portable, and we have battery enough to power everything for several hours. But we cannot leave the house by law. And then from the blue sky came the idea: let the cats out for a walk! Bo and Luna would never let us down, they were more than happy to join this lockdown adventure. We moved the telescope to the bank of the nearby channel, with a clear view of the northern skies. The town looked and sounded unusually abandoned for the early night hours, it was rather creepy. But we happily accomplished our mission.
Since the nova remained relatively constant bright for weeks, we had two other nights about a month later. But those were done from the back garden in the early hours before dawn as Cassiopeia was rising in the northeast. Two of these nights we used our narrow-band filter to emphasize the beautiful Bubble Nebula in the colors of ionized hydrogen and oxygen. One of the nights we used our broad-band filter, to have the stars with more natural colors. All of these were then combined into a single image shown above, with a bit more detail below. The nova is the bright orange-reddish star a bit left and below the center.
A naked-eye phenomenon
When novae erupt, they increase their brightness 10-100s thousands of times, sometimes becoming even visible to the naked eye. This is a rather rare sight, only a couple of examples are known in the past decades. Nova Cassiopeia brightened to naked-eye visibility in the first days of May, for a short period of time. Unfortunately, we could not follow this because the weather was bad in the Netherlands. However, we obtained an image using one of the Insight Observatory‘s remotely operated telescopes (the 16″ f/3.7 Dream astrograph in New Mexico, hosted at SkyPi Remote Observatory) and we liked the result very much. But since it is not truly our image, we will not share it here. If you want to support their educational activity, you may purchase observing time yourself.
A nova in Cassiopeia!!! Finally some excitement! Although it is an unfavorable position, blocked by the buildings to the northwest (the whole Wega complex). Must set up our base next to the channel, breaking the curfew regulations (story above). Our heroes of course protect us from unwanted neighbor cat proximity, chasing them away. Only once in this process, a cattail got entangled with the wires, causing a few arcsec oscillations in guiding. But you have to pay the price for safety when you are on an astrophotography adventure under curfew!
Clear skies predicted for the whole night. A few days ago I noticed that Cassiopeia was getting visible from our garden at dawn. So decided to move the telescope closer to the fence, to have an earlier view, and do the L-Pro shot of V1405 Cas (the Nova) in broadband, to have nicer stars in the Milky Way. Started the night on M101.
On the western sky there was a thin layer of clouds, so chose the first target (M81-82 with the L-eXtreme), high in the sky. That run finished before 2 am. Managed to get up at 2:15 spontaneously, and moved to Nova Cas. Scheduled and completed 30x300s run with the same gain 240 between ~2:30-5:15 am. Had a good sleep on the couch in the meantime. We woke up for a beautiful morning.
Using the Dream astrograph
We centered the image on NGC 7654 731 (member 731 of the M52 open cluster), which is very close to the nova. This gives a nice shot of everything, the nova, the M52 core, and the Bubble Nebula. The picture was taken on May 11th, 2021, at 1:54 am (end time in their local timezone). Darks and flats were available for download, too.
V1405 Cas, Bubble Nebula, M52 – 4.8 h, from Hoogeveen, Netherlands
30 March 2021 (20x180s), 16 April 2021 (30x300s) Optolong L-eXtreme
14 April 2021 (26x180s) Optolong L-Pro
Telescope: William Optics GT81, f/5.9, with Flattener 6AIII 0.8x
Camera: ZWO ASI533MC-P
Guidescope: WO Uniguide 50/200 with ASI120MMmini
Mount & control: iOptron CEM40, ASIair Pro
Filter: Optolong L-eXtreme, Optolong L-Pro
Software: Astro Pixel Processor, Photoshop