Peter,

A good recent example of this was C/2011 L4 (PanSTARRS). Have a look at
the images around the end of 2013 May close to the orbit plane crossing
here:

https://britastro.org/cometobs/2011l4/index.html

What we are seeing is dust far from the comet in the plane of the orbit
projected edge-on onto the sky. It can lead to a spectacular enhancement
of the visibility. The dust in the anti-tail can be a very long way away
from the nucleus and has spread out but stays pretty much in the orbital
plane.

We cross the orbital plane of C/2021 A1 (Leonard) around December 8th so
that might have a similar effect although it will be a very difficult
observation from the UK.

Nick.

On 11/11/2021 19:57, Peter Carson wrote:
> Here’s an image of 67P/Churyumov-Gerasimenko taken on the Nov 10^th from my
> remote observatory. I’ve highly contrast stretched and inverted it to show what
> appears to be a faint anti-tail. I’ve recently seen some similar images and
> thought the anti-tail might be an artefact, but it’s not.
>
> Can someone tell me what we are seeing?
>
> My image has a FOV of 48’ wide. A larger FOV and longer exposure is required to
> better see what is going on. Other details on the image.
>
> Peter
>
> Peter Carson
>
> Essex UK
>
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