artefacts due to CCD sensitivity

[tilvi]

Heres I am posting a message from AAVSO list which describes in short the CCD sensitivity artefacts,

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lou krajci wrote:
> The last two nights I've been imaging V417 Lyr (19 08 39.1 +30 43 09) to
> determine some eclipse timings for this EB. A couple arcminutes to the
> west lies XZ Lyr (19 08 31.2 +30 43 21)...a Mira variable...that shows up
> very bright in my unfiltered CCD exposures. It also shows up bright in
> 2MASS images I pulled up in Aladin.
>
> Is it typical for a Mira variable to be so bright in the IR bands?


It is typical for unfiltered CCD - and it's one of the more common traps for
beginner CCD observers. I've received many "nova discovery" reports that
turned out to be (visually faint) Miras or carbon stars. Widefield images of
the night sky from mass-produced digital cameras can also show interesting
artefacts, due to their sensitivity to near-infrared.

Incidentally the IR amplitude of a typical Mira is generally much less than
its visual amplitude. And IR photometry is a subject full of discoveries to
be made. But I don't know of a procedure to convert a CCD camera into
something that only sees IR.

cheers,
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