.. Links to useful files 21/05/2018

.. include:: globals.rst

.. highlightlang:: rest

Useful files
************

This page documents some files that may come in useful while observing or
during reduction.

.. _defect_files:

CCD defects
===========

The |hiper| CCDs have a number of defects, dust and the like, and, as
of 13 May 2021, a hair in the upper-right quadrant of CCD 2 along with
a long-standing similar feature in the lower-left quadrant of
CCD 4. When acquiring targets these may not be visible so you are
**VERY STRONGLY ADVISED TO OVER-PLOT DEFECTS**. You can also create
your own using the pipeline command |setdefect| and you are encouraged
to do so if you see a defect not already marked in whatever file you
use.

Defects are classified as "moderate" (plotted in yellow) or "severe"
(red). What one counts as one or the other is a matter of taste. If you are
too picky, you could end up with so many defects that you are afraid to
observe.

I have decided to define defects according to the following
prescription: ``moderate``: 10 to 25% deviation from the norm;
``severe``: greater than 25% from the norm. I mark each pixel in these
categories, so a really bad feature might appear in multiple pixels
(there is a very nasty feature in the lower-left quadrant of |hiper|'s
CCD 4 for example). I plan to update the files with time, and retain
old ones for monitoring purposes.  I identified the bad pixels using a
flat field divided by a smoothed version of itself (smoothed with a 40
pixel FWHM 2D gaussian filter). I have also marked some lines caused I suspect
by charge traps. These are visible in biases at least; I am unsure
what effect they have when enough light is coming in.

For ULTRACAM I have also added hot pixels. Although these should at
least partially be removed if you apply a dark fram during reduction,
they can potentially add noise, e.g. if your target has 500 counts but
sits on top of a hot pixel contributing 10000, you get noise of
sqrt(10500), but still just a signal of 500 (and that's assuming
perfect dark frame correction). Clearly then the impact depends upon
the target so it's more difficult to assign severity levels. In the
file for ULTRACAM below I decided somewhat arbitrarily to define a
count rate of 40/sec and above as "severe", and 15 to 40 as
"moderate".  However, to help judge, hot pixels appear in the form of
integers representing the count rate.

When observing, you should move the target and essential comparison
stars away from any such defects, particularly those that appear in
red. The zoom/pan feature of |nrtplot| is useful for this.

Current files:

  #. 2021-08-02 (:download:`HiPERCAM defect file
     <hipercam_defects_2021_08_02.dft>`) Hair on CCD 2 gone
     after cleaning by Vik following removal of the CCD window
     to fix a leak.

  #. 2021-06-09 (:download:`ULTRACAM defect file
     <ultracam_defects_2021_06_09.dft>`) Hot pixels marked.

  #. 2019-12-08 (:download:`ULTRASPEC defect file
     <ultraspec_defects_2019_12_08.dft>`)

Old files:

  #. 2021-06-09 (:download:`HiPERCAM defect file
     <hipercam_defects_2021_06_09.dft>`) Some linear
     charge trap (?) features marked.

  #. 2021-05-13 (:download:`HiPERCAM defect file
     <hipercam_defects_2021_05_13.dft>`) New hair in
     upper-right of CCD 2.

  #. 2018-06-21 (:download:`ULTRACAM defect file
     <ultracam_defects_2018_06_21.dft>`) Added another bad column in CCD 2

  #. 2018-06-02 (:download:`ULTRACAM defect file
     <ultracam_defects_2018_06_02.dft>`)

  #. 2018-05-21 (:download:`HiPERCAM defect file
     <hipercam_defects_2018_05_21.dft>`)

Darks
=====

Dark frames made from |makedark|.

  #. 2021-05-27. Made from 26x60 sec dark frames.
     (:download:`ULTRACAM dark frame
     <ultracam_dark_r006_2021_05_27.hcm>`)

.. _fringing_files:

Fringe maps and peak/trough pairs
=================================

Two types of files are needed to implement defringing.  Fringe maps as
generated by |makefringe| (these are standard hcm files in format),
and sets of peak/trough pairs as generated by |setfringe| with
extension ".frng" (JSON text files). Here are some pre-prepared
examples to get you going, but if the z-band is important fo you, you
may want to get your own calibrations:

  #. 2018-05-19, HiPERCAM fringe map. Created from runs 0018 to 0025
     from the night of 2018-05-19 on the GTC, with one frame of 0019
     removed because of a satellite trail. 71x120 sec dithered images
     in all. Smoothed with FWHM=4. (:download:`hipercam z-band fringe
     map <hipercam_fmap_2018_05_19.hcm>`)

  #. 2018-04-15, HiPERCAM fringe map. Created from runs 0035 to 0043
     from the night of 2018-04-15 on the GTC, with one frame of 0038
     removed because of a satellite trail. 71x120 sec dithered images
     in all. Smoothed with FWHM=4. (:download:`hipercam z-band fringe
     map <hipercam_fmap_2018_04_15.hcm>`)

  #. 2018-04-15, associated peak/troughs. Not necessarily definitive but
     a start. (:download:`hipercam z-band peak/trough pairs
     <hipercam_fpair_2018_04_15.frng>`)