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Bob,
It will be intersting to see your report when you are able to observe
then comet. JJ was observing from a high altitude mountain site and it
exceptional that he has been able to observe this faint (mag 15 from my
own digital observations)comet. I am not suprised there are no other
visual reports of this comet, it is faint for visual observers, but an
relatively easy target for imagers. The feat of visually observing a
faint outer coma would seem to be difficult in a comet this faint.
However according to JJ he did indeed acheive this.
Best wishes
Denis


? ? ? ? ------ Original Message ------
? ? ? ? From: nightsky55=[email protected]
? ? ? ? To: [email protected]
? ? ? ? Sent: Sunday, December 29th 2024, 20:09
? ? ? ? Subject: Re: [comets-ml] Unusual brightening of comet C/2023 Q1


? Jakub and all,
? This discussion has inspired me to observe C/2023 Q1 in my 38-cm
reflector at the next opportunity. I also have a very
? dark sky especially in the north direction — when the aurora isn't
active! It would be nice if we had some additional visual observers so
there would be
? a pool of estimates to draw upon. J.J. Gonzalez Suarez's observation
is the only visual sighting of the comet I'm aware of.

? Bob

? On Sun, Dec 29, 2024 at 1:17?PM Jakub ?ern? via
<kaos=[email protected]> wrote:
? ? ? ? ? ? ? ? ? ? ? Hello all,
? ? ? ?If I have read the posts correctly, we have two observations:
? ? ? ?CCD magnitude of 14.1 mag with a 5' aperture.? ? ? ?Visual
magnitude of 11.6 mag with a 6' aperture.? ? ? ? ? How can we explain
such a large difference? The CCD method? ? ? ?measures flux in a chosen
aperture, and we know that a comet’s? ? ? ?surface brightness decreases
with distance from the central? ? ? ?condensation. However, even if the
surface brightness is? ? ? ?decreasing, the increase in the area of the
coma can still? ? ? ?significantly change the total measured magnitude.
? ? ? ?Regarding the well-known “CCD vs. visual” issue, it often arose
in the past from insufficient exposure times, which led observers to
measure only the central condensation in a smaller aperture, whereas
visual observers saw more of the coma. Even among visual observers
alone, an “aperture effect” has been described—smaller telescopes can
show a larger apparent coma and thus yield brighter magnitude estimates.
Hence, the 2–3 mag discrepancy was typically caused by different coma
sizes captured in visual vs. CCD observations. However, this problem has
largely faded in recent years as CCD observers have become more
experienced. With proper techniques, CCD observations now usually match
visual data closely, differing by only a few tenths of a magnitude due
to variations in spectral sensitivities (especially for unfiltered or
narrowband photometry vs. visual V or g' bands).
? ? ? ?It is unlikely that a difference of 2.5 mag could arise from
nearly the same apertures (5' vs. 6'), because an increase of just 1' in
aperture should not produce such a large magnitude gap under normal
circumstances.
? ? ? ?Although it is possible to measure an object as 2.5 mag brighter
by including a much larger coma with very low surface brightness (for
example, if the visual observation indicated a coma diameter of
15'–20'), this is not the situation described here. Therefore, the
reported visual observation may be in error—either in the estimated
magnitude or the coma diameter. The observer should re-examine their
observation to identify where the discrepancy arose.
? ? ? ?No one is flawless—myself included. It has been demonstrated many
times that observers can report objects or details they did not actually
see. There have even been cases where a comet was reported at the wrong
position. We must learn from such instances in order to provide
scientifically valuable data.
? ? ? ?Best regards,? ? ? ?Jakub ?ern?