[vsnet-chat 3942] Re: Delta Sco observed by SOHO

[Hitoshi YAMAOKA <yamaoka@rc.kyushu-u.ac.jp>]

Dear all,

F. Farrell wrote:
> Unfortunately I can't provide numbers because their archive server
> is refusing to let me do FITS downloads which I could feed to image
> analysis. I was restricted to viewing the GIF equivalents and
> visually comparing the images of Delta Sco with nearby stars :(

LASCO C3 is a coronagraph, which has an external occultor.  So the
object at the more inner part of the image would be more vignetted.
Even with the FITS file, the precise (below 0.1 mag) photometry
would be difficult.  

The comparison with the images taken on the previous years is
plausible, as done by Fraser.

> I don't know the limiting magnitude of LASCO C3 or how its images
> compare to visual observation but it seems to be useful for filling
> in the annual data hole for variables near the ecliptic. 

The response is comparable with unfiltered CCD.

T. Scarmato wrote:
> I Have valued that the magnitude limit of LASCO C3 is 9 in the better
> images.

The FAQ of LASCO tells that the limiting magnitude would down to 10th
magnitude.

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan
yamaoka@rc.kyushu-u.ac.jp

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