[vsnet-campaign-blazar 288] (fwd) further information on Mkn 421

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

(fwd) further information on Mkn 421

Date: Thu, 28 Nov 2002 12:16:03 +0100
From: Massimo Villata <villata@to.astro.it>

Subject: Mark 421
Date: Thu, 28 Nov 2002 10:05:16 +0000 (WET)
From: Mark Kidger <mrk@ll.iac.es>
To: villata@to.astro.it



Maximo:

Having carefully calibrated the Mark 421 field in the visible and near-IR
I can only endorse your comments. Mark 421 was a suggested target for the
original OJ-94 campaign and was dropped because it was just too difficult.
Even with larger detectors that has not changed: the presence of the 6th
and 7th magnitude stars nearby and the overwhelming nebulosity make this
an almost impossible object to observe properly. What is worse, in the
near-IR we were unable to calibrate a single field star because ever
single one of the selected stars appeared extended in the near-IR frames
and thus was probably a galaxy.

The only success that I have ever had with this object is with near-IR
photometry using a single-channel photometer, and even then the galaxy
makes life difficult. We lost out photometer a couple of years ago, but a
new one should be commissioned this Winter. Without it I would not even
consider trying to observe Mark 421 seriously.

Mark

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