That explains a mystery - I failed to locate it two nights ago with a mono CCD but captured it last night reverting to the colour camera, even though I was part obstructed by the North wall of my own observatory.  Will post an image later today - have only just surfaced after staying up to watch Jupiter!

Sent from my iPhone

> On 9 May 2020, at 09:36, Nick James <ndj@nickdjames.com> wrote:
>
> Morning everyone,
>
> Up until yesterday the central region (11 arcsec radius) of C/2019 Y4 has been brightening at around 0.05 mag per day but last night it had jumped by a whole magnitude compared to the night before (May 7.9 vs May 8.9). The attached plot is from my astrometry with a 0.28-m, f/10 SCT in Chelmsford.
>
> Terry Lovejoy, via the CometWatch FB group, reports a similar sudden increase between May 8.12 and May 9.12 using the iTelescope T11 system in New Mexico.
>
> With all the excitement over C/2020 F8 (SWAN) please remember to keep observing Y4 for as long as you can.
>
> Nick.
>
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> <2019y4b.png>