M61, with Supernova

Designation:	Messier 61, NGC 4303 – with Supernova SN 2020 jfo
Constellation:	Virgo
Magnitude:	+9.5
Apparent size:	6.9 arc-minutes.
Diameter:	80,000  light years.
Distance:	52,000,000 light years.
Date:	2020-05-24.
Exposure:	110 minutes (18 x 367 sec. Binning: 2x)
Field of View:	20.4 x 20.4 arc minutes (highly cropped from 1.6° x 1.0°original)

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This is the first supernova I’ve ever imaged, located in Messier 61, a barred spiral galaxy.

SN 2020jfo was discovered on 6th May 2020 and is a core collapse Type II supernova. In a few months it will probably be too dim to see.

OK, so where’s the supernova?

I should mention first that – whilst the galaxy M61 is 52 million light years distant – every bright star in the image is right back here, in our own Milky Way galaxy. At a guess most likely they are all less than about two or three thousand light years.

Where’s the supernova??

Hang on a bit. The only objects outside the Milky Way galaxy in this image are (a) M61, (b) the supernova and (c) another small galaxy, NGC 4301, a small galaxy about sixty four million light years away (fuzzy object upper right).

Just tell me where the supernova is!!!

Find the very bright central core of the galaxy. Below it you will see a row of four very bright stars. The third one from the left (directly below the galactic core) is Supernova SN 2020jfo – a star which destroyed itself about three weeks ago in a cataclysmic explosion. Astronomers will be on the lookout for supernova remnants and evidence of either a black hole or a neutron star.

Its magnitude appears very similar to the other three stars, which are comparable to the brightness of Pluto (around 14th magnitude). Yet it is perhaps 60,000 times further away!

EDIT: Just for the record, I’ve added the following image which marks the supernova.

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This image was conceived out of good fortune but was dogged with bad implementation.

The good fortune: The region of sky occupied by M61 would previously have been blocked by the sixteen metre high gum tree across the road.

My neighbour requested Council remove it. I had nothing to do with it – but its removal has improved my North Western outlook, especially down below on the Front Driveway Observatory (FDO), which is about one third of the way to the tree in the image below.

22nd May 2020 – FDO sky visibility improvement programme, well underway.

The feature image would not have been possible without the intervention of BJs Tree Service, who removed the stricken tree just two days earlier. It’s amazing how four men can turn a sixteen metre tree to mulch in the back of a truck in little over an hour!

The bad fortune: unknown to me until afterwards, a battery connection to the camera failed, meaning (a) its cooling system; (b) fan; and (c) its dew heater all failed. The result was very poor image quality.

This was compounded by the failure of my dark and flat files, due to a bungled first time attempt to use pixel binning – a process of combining adjacent pixels to improve the signal-to-noise ratio of an image at the expense of reduced resolution.

As a result, the image had to be drastically cropped and digitally enlarged – further reducing image quality – but it was exciting to image a distant supernova for the first time! 😵

The reminder I had recently placed at the top of my imaging work sheet was prophetic: 😧

IF YOU DEPART FROM A PROVEN ROUTINE, BE PREPARED FOR TROUBLE

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EDIT: I had it easy, using a ‘goto’ telescope and stacked imaging. See here for Telescope Paul’s inspiring account of his star-hopping attempts to find the supernova.

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Telescope Details
SkyWatcher Esprit 120 mm apochromatic 3-element refractor.
840 mm focal length @ f/7 with field flattener.
Baader L-Booster UHC-S light pollution filter 2458276.
SkyWatcher EQ6-R Pro mount.
Camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx)
ZWO ASI120 guide camera, using PHD2 software.

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