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CCD Views #316

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                             C C D   V I E W S   #316
                            --------------------------
                                November 6, 2003


              
 Table of Contents
 -----------------
 1. Introduction
 2. QS Tel Campaign
 3. Standards Observing Project
 4. Future of CCD Technology
 5. CCD Observing of NMO Targets
 6. Blazar Report & New Charts
 7. UV Per Outburst
 8. CCD Points

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1. Introduction

  Not much time has passed since CCD Views #315 and we already have
enough material for a new issue. Now is a good time to be a CCD
variable star observer.
  The CCD Committee is beginning a project to observe standard
fields. The goal is this project is to help identify systematic
errors in the observers' systems. Anyone is welcome to participate
in this program. All you need is a desire to learn how to do the
best photometry you can. See section 3 for more information.
  A new discussion group dedicated to the discussion of variable
star CCD and PEP photometry and observing projects has been setup.
To read the archives and/or join visit this URL:

 http://www.aavso.org/pipermail/aavso-photometry/

  We encourage the use of this discussion group to discuss topics
mentioned in issues of CCD Views.
  Also, an old friend has returned in CCD Points. :)

 Aaron Price (PAH)
 On behalf of Janet Mattei and Gary Walker, Chairperson of the CCD Committee

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2. QS TEL CAMPAIGN

  Dr. Christopher Mauche, Lawrence Livermore National Laboratory,
has requested our assistance in ongoing monitoring, particularly by
CCD observers, of the magnetic cataclysmic variable 1931-46 QS Tel,
continuing until at least the end of 2004. He recently visited
AAVSO HQ and reiterated the need for more data, especially CCD.

  Since the announcement in Alert Notice #302 on September 26 only
two observers have been regularly following QS Tel (Peter Nelson & Berto
Monard - thanks guys!). It is a difficult object for most being both faint
and in the southern hemisphere. However, this is an opportunity to
make the object your own and really contribute data in an area that
it is needed.

  ** If you can get down to -46 degrees and have a CCD, please
add QS Tel to your observing program!! **

  Observe QS Tel in V and R at least one time per night of
observing. Try to make your estimates as accurate as possible. This
will help monitor the basic activity of the star. Then once per
month or so, or if you notice a sudden change of brightness during
your regular observations, spend an evening getting time series data
on QS Tel. This will help monitor its 2 hr 20 min orbital period.

  Dr. Mauche informs us: "Regular observations are required to (1)  
establish the optical behavior of QS Tel, and (2) trigger an approved
target-of-opportunity Chandra Low Energy Transmission Grating
observation, which can take place only when the source is in a high
state. The Chandra data will be used to measure the EUV/soft X-ray
spectral energy distribution of the accretion-heated white dwarf
photosphere and refine the parameters of the absorption lines and edges
first detected with the EUVE satellite by Rosen et al. (1996, Monthly
Notices Royal Astronomical Society, 280, 1121).

  QS Tel is a very bright extreme ultraviolet and soft x-ray source
likely to be of ongoing interest to researchers, so long-term optical
coverage is very important. In fact it is the 2nd brightest AM Her
star in the sky in extreme x-rays. Because little is known about its
optical behavior, this request for optical monitoring represents an opportunity
for observers to add to the fundamental information on QS Tel.

  More background information on QS Tel and observing charts are
available in Alert Notice #302 and at this URL:
  [link removed - all charts can be plotted at http://www.aavso.org/vsp]

  QS Tel is currently fading. Recent light curve of QS Tel:
  [link removed]

  Recent Observations of QS Tel:
           QS TEL   OCT 16.7050  15.4  MLF   CR    
    QS TEL   OCT 16.7050  15.4  MLF   CR    
    QS TEL   OCT 26.7440  15.8  MLF   CR   
    QS TEL   NOV 04.4372  16.7  NLX   CCDV  SN=10, 500 SEC EXPOSURE Err: 0.1
    QS TEL   NOV 04.4590  17.0  NLX   CCDV  SN=10, 500 SEC EXPOSURE Err: 0.1
    QS TEL   NOV 04.4649  16.7  NLX   CCDV  SN=10, 500 SEC EXPOSURE Err: 0.1
    QS TEL   NOV 04.4708  16.5  NLX   CCDV  SN=10, 500 SEC EXPOSURE Err: 0.1

  Thanks to the following observers for submitting observations of
QS Tel since the publication of Alert Notice #302:

    HBD Bernard Heathcote, Australia
    HDJ David Higgins, Australia
    MLF Berto Monard, South Africa
    NLX Peter Nelson, Australia

  Extra special thanks to Peter and Berto for their continued  monitoring!!
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3. STANDARDS OBSERVING PROJECT

   By Gary Walker (WGR), CCD Committee Chairperson

 What is it?
 We are starting another observing project with this issue of CCD
Views.  This project is intended to encourage observers to check
their accuracy and repeatability of observations, using some
known Landolt Fields, that have been well observed by Arne Henden
(He has actually observed these more than Landolt did).  This
project will allow observers to check methodologies--ie SN,
Flatfielding, Dark Subtraction, Software Reductions, etc.

 Proceedure--ie What do I do?
 What you do is perform a time series (of 15-20 multiple
exposures) of a Standard Field, which is well known.  Thanks to
Bruce Gary and Arne Henden, we have selected 13 of these fields,
which means that one should be up at the meridian nearly every
night.  A table with the names and the magnitudes can be found at
[link removed] .

 Observe a field in V filtered, untransformed.  Reduce each
exposure separately.  Do not average your exposures.  Measure
Star A relative to Star B only. Each exposure should be according
to your normal proceedure - a good rule of thumb is to expose
long enough for the brightest star in the process to register
half of full well. Report your results to HQ using WebObs or your
standard proceedure, that way we can share the light "curves"
with all observers.  Use the star name and letter A (ie SA114A)  
listed in the web page above for your v instrumental magnitudes
(V filtered by untransformed).

 Thats about all there is too it.  A few administrative things.
These observations will count towards your totals.  Please share
your results.  I have already shared some of my results on SA114,
which I used to check out the proceedure before launching the
project.

 When you make a finding or have a question, post it to the new
photometry discussion group (see introduction for subscription
information).  Please share your findings, especially those that
have improved your photometry.

 Advanced Projects-BVRI
 If you customarily do BVRI photometry, and would like to check
your system, you can observe with your BVRI filters and transform
your data.  Again, report it to HQ using Webobs or your favorite
method. Designate the measurement at CCDB, CCDV, CCDR, or CCDI as
appropriate.

 Advanced Project-Fainter magnitudes
 If you would like to test some fainter magnitudes, then try
measuring the fainintest star in the table on the web.  Measure
relative to Star B.  This will give a couple of magnitudes
fainter information and may tax your proceedure. Report this
information as SA114D, or SA114E the same as in the table for
example. These measurements should be instrumental, v filtered,
and not transformed.

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4. THE FUTURE OF CCD TECHNOLOGY

  By Arne Henden, U.S. Naval Observatory, Flagstaff Station.

  CCD detectors are pretty darn near perfect.  They have very high QE
(quantum efficiency, basically how many photons they detect compared to
how many actually fall on the device), low readnoise, wide wavelength
response and low cost for millions of pixels.  So how can they be
improved?

  First, the QE has been slowly creaping upward.  The original
frontside illuminated Kodak chips, for example, had to image through
the electronic gate structure.  These gates are made of polysilicon,
reasonably transparent in the red but almost opaque in the blue.  The
net effect was that you only detected perhaps 40percent of the incident
photons.  The recent blue-transparent (TIN) gate material from Kodak
has increased the QE to 80percent or more, almost as good as thinning
the CCD and imaging from the backside, a very expensive technique.  In
addition, using microlenses over each pixel to focus the light on the
most sensitive part of the pixel improves the QE.  Kodak is just about
ready to release CCDs with the TIN gate technology on both of the
gates, so that no microlenses will be necessary. I think QE is rapidly
becoming a non-issue, with a broad peak QE of 80-90percent possible on
frontside illuminated devices.

  Next, the blue response is getting good on most CCDs.  However, the
red response is harder to control.  What happens is that the silicon
itself starts becoming transparent and the mean free path of photons
increases to such a point that most travel through the active region of
the pixel and are not detected.  By 1.1 micron, you have zero QE with
silicon-based CCDs.  Before that point, you can increase the QE by
making the active pixel region thicker, or by doping the silicon so
that the photon pathlength becomes shorter.  Both of these tricks
increase the QE, but usually at the expense of poorer resolution or
higher dark current.  I think you will see CCDs in the near future that
have 30percent QE near the 300nm cutoff of the atmosphere, and
20-30percent QE all the way out to 900nm.  Not perfect, but pretty darn
good.  The way technology has been improving, it might even be possible
to get close to 90percent QE over that entire range.  Remember, though,
that 100percent QE is the absolute limit.  Going from 80percent to
90percent is not a huge gain, so we are rapidly approaching the limit.

  The area where CCDs will get worse is in pixel size.  The larger the
pixel, the larger the full well capacity and the greater the dynamic
range for an image taken with the CCD.  Manufacturers, though, are
going for small pixels since their primary market is consumer cameras
where camera size is important.  They want more pixels, not larger
detector size.

  There are some interesting projects underway.  The Orthogonal
Transfer CCD enables charge to be transferred in all directions. This
might be an interesting technique for fast guiding on-chip. The
electron multiplier CCD uses a string of amplification between the
serial register and the readout node of the CCD, providing noiseless
amplification of the signal.  This means you can get subelectron
readnoise on a CCD, thereby permitting single-photon detection and
removing readnoise entirely for low light level situations (such as
spectroscopy).

  Other detectors are being developed.  The GaAs technology is used by
the communications industry for fiber networks, and more companies are
developing arrays of GaAs detectors for 2-D detection to improve the
signal/noise on long hauls.  These detectors offer 1-2micron capability
and extend the amateur's usable wavelengths into the near-infrared.  
The CMOS industry continues to improve their detectors, and I expect
megapixel devices with low dark current and low readnoise to be
competitive with CCDs in a few years, possibly at extremely low cost.

  The future looks bright.  Ten years ago, few amateurs were using CCD
cameras and now they are a standard option for most telescope
purchases.  Computers and software are improving dramatically.  I
expect the vast majority of telescope users to have an imaging camera
before long; maybe we can convince a large fraction to start
contributing photometry!
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5. NOVEMBER NMO TARGETS FOR CCDs

  By Mike Simonsen (SXN)

  In March of 2003 an informal initiative to coordinate efforts of
observers to provide better coverage of stars in need of more
observations (NMOs) was created.

  The main idea was to share the observing between visual and CCD
observers. Visual observers would concentrate on targets brighter than
13.5V and CCD observers would concentrate on obtaining positive
observations fainter than 13.5V.

  In hopes of getting some of you to contribute to this initiative I
have identified some appropriate targets for CCD observers in
November.

Z Ari- (10.2-<15.0) Currently around the threshold of 13.5V and
fading, this one is ready to be handed off to CCD observers.

SV Aql- (10.2-<15.5) Probably on the rise from minimum, but the data
has significant scatter. The sequence probably doesn't help much. This
light curve needs help.

EU Aql- (11.4-15.1) At or near the 13.5 threshold and fading, this
star lies in a particularly busy Milky Way field. Not recommended for
beginners or the faint of heart. There is new photometry for this
field from Arne Henden in V and Ic, and the chart team is working on
new charts, but it will be a while before they are available. You can
get the data from Arne's ftp site.
[link removed]

VY Aur- (10.3-14.7) Fading towards minimum, this one is favorably
placed for months to come.

RX Del- (10.2-<15.5) This one has just reached the mid 13's and is
fading to minimum. The AAVSO charts have a good CCD(V) sequence from
R. Zissell.  Still well placed in the evening.

SU Cnc- (10.5-<15.4) Currently in the 14th mag range, most likely
headed for minimum. You should be able to follow this one for several
months and get observations from minimum to maximum by the time it is
lost to the sun again.

AU Cyg- (8.7-15.5) New charts with a Henden sequence are now available
for this star. Visual observers lost it around mid-October in the 15th
mag range. Faint observations are needed to fill out the bottom of the
curve. The trend in the last four cycles seems to indicate it is
experiencing progressively fainter minima.

SS Del- (11.3-<16.0) This Mira has a relatively short period (194d),
so more frequent observations are appropriate. The sequence and charts
for this star are very good. Currently in the 16th mag range, heading
for minimum.  Go deep!

UZ Gem- (8.8-<15.0) This one is truly in need of more observations.  
There is scant data for it when fainter than 11th magnitude. It is in
the 15th magnitude range now, so probably on the rise, but who knows?
Ugly charts with a totally inadequate sequence do not help the
situation. Be careful in identifying the variable.

SU Lyr- (11.2-<18.0) Few positive visual observations of this faint
LPV exist fainter than 15V. It is reported to be in the 17th magnitude
range currently. This is an obvious CCD target. There are good charts
with a CCD(V) sequence available.

R PsA- (9.2-14.7) Scant observations indicate it is 13+ and fading.  
This is another star that may be exhibiting progressively fainter
minima recently. CCD observations would help define the bottom of this
curve. A poor sequence and declination of -29 degrees contribute to
the scant data. Southern observers are encouraged to help out on this
one.

S Tau- (10.2-15.3) Visual observers lost this one in the low 14's in
October. Positive faint observations are needed around minimum. With a
period just over one year, the maxima keep getting missed while in
conjunction with the sun, so there is not a lot of recent data on this
star. Follow it as long as possible.

Z Tau- (9.8-13.9::)  Z Tau has a close 14th mag companion that
probably has disguised the actual minima of this star for ages. It is
in a good field with lots of comparisons, and RU Tau is close by; a
two for one bargain! New charts and sequences for both of these will
be released in the coming month. Henden photometry is available on his
ftp site: [link removed]

If you are looking for other challenging faint targets you can
download the NMO Planning Tool from the website.

http://www.aavso.org/aavso-bulletin

Stars are sorted by their current status, so you can skim the list for stars fainter than 13.5v
relatively easily.

Good luck and clear skies.

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6. BLAZAR REPORT & NEW CHARTS - GET IN EARLY!

  In the last issue we called for observations of 9 blazars. We
received 203 total observations. Out of those, 55 were CCD. All of
the CCD observations were done with a filter. Way to go! Below is a
list of CCD observers ranked by how many observations they made of
the GTN blazars:

 Obs Rank   Who      What
     1      RSE     BL Lac, 3C 66A, Mark 41, Mark 501 & 2344+514
     2      MDA     BL Lac
     3      JM         3C 66A, Mark 501
     3      WDZ     BL Lac and 3C 66A
     5      OAR     3C 66A, Mark 501
     5      DIL     3C 66A
     5      SDY     BL Lac
     8      GBL     Mark 501, OI+158, 2344+514
     8      GMZ     BL Lac
    10      HDU        BL Lac
    10      RR         BL Lac
    10      MDW     BL Lac
    10      MMG     3C 66A

  This is a CCD publication, but visual monitoring is needed as
well. Thanks to visual observers MUY, KRB, PUJ, OJR, VJA, HUZ, GMZ,
SXN, STR, MGH, PYG, TDB, & SUI for their data.

  It's a good start but we need more so we can set an accurate
baseline for these stars (except BL Lac which seems to be well
covered for now). Please add these blazars to your program and
observe them once per week in CCDV and in R, Ic if you have the
appropriate filters.

  Also, CCD charts for 5 new blazars have been published. Please
observe these as well. Most of these are not well observed at all so
any new data will add to our knowledge of these objects' behavior!

    0106+22  S2 0109+22
    1746+09  OT 081
    1749+70  S4 1749+70
    1806+78  S5 1803+78
    2002-49  PKS2005-48

  We have *no* recent observations of those objects in our database.
This is a great opportunity to get in early!
 
  Nice & new charts for all these objects are available at:
            http://www.aavso.org/vsp
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7. UV PER OUTBURST

  UV Per (UGSU) appears to be in outburst for the first time
since late December of 2000. So far there are no reports of this
being a superoutburst. However, in 1989 and 1996 UV Per
experienced an outburst followed by a superoutburst and then a
post superoutburst brightening resulting in 3 different light
curve peaks. So careful monitoring over the next 10 days is
warranted.

 Please observe UV Per closely and report your observations to
the AAVSO as soon as possible. Get high quality and high resolution
data to look for superhumps that may signify a superoutburst.

 Charts of UV Per, revised in November of 2002 are available here:
http://www.aavso.org/vsp

 The f-chart has CCDV photometry from Arne Henden good for visual
and .1 mag CCDV use. For more accurate V & B photometry consult
Arne's DAT file:
  [link removed]

Light curves:

 Recent light curve:
http://www.aavso.org/lcg

 All 34,000+ observations (except fainter thans) dating back to 1933:
http://www.aavso.org/ql

 Close up of light curve of last outburst:
http://www.aavso.org/lcg

Last CCD observation:
        UV PER     OCT 08.1243 <17.2   GKA   CCDV
Latest UV Per visual observations:
            UV PER       NOV 05.7361  11.7   MUY
        UV PER     NOV 05.8201  11.8   NDQ   
        UV PER     NOV 05.8632  11.6   GGU

    GKA - GRAHAM, KEITH A (ILLINOIS)
    MUY - MUYLLAERT, EDDY (BELGIUM)
    NDQ - NAILLON, DOMINIQUE (FRANCE)
    GGU - GILEIN, GUUS (NETHERLANDS)
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8. RETURN OF CCD POINTS

  The last few CCD Views felt empty to me. While full of good and
useful information there was a hole in there. I think it was the lack
of CCD Points. So they're back, this time for good. I'll also give
you some insight into the super-secret-mega-formula that goes into
computing them.  Each observation is worth one point. But it can gain
points and fraction of points for a variety of things.

  + Observing stars mentioned in previous CCD Views, Special
    News Flashes or Alert Notices
  + Observing bulletin stars in need of more observing
    (points vary based on the need of data)
  + Observations reported with uncertainty ("Err:" field)
  + Transformed observations ("Transformed:" field)
  + Faint observations (points dependant on magnitude)
  + Observations done with a BVRcIc filter
  + Observations done within a few days of the full moon
  + Total number of objects observed
  + If your observer code is PAH you get a bonus of 10,000 points

  Eventually I'll start a column for running FY total and ranking.
Send any recommendations for point modification to aavso@aavso.org.

  REMINDER: CCD Points are *not* an official AAVSO report and carry
no weight at HQ. They are provided purely for fun and to start
barroom brawls at AAVSO meetings.

  Now without further adieu...

 Pts    Obs    Observer
 5386   896    JM  JAMES, ROBERT A. (LAS CRUCES,NM,USA)
 1042   1098   COO COOK, LEWIS M. (CONCORD,CA,USA)
 971    135    MMU MUNKACSY, MARK J. (PORTSMOUTH,RI,USA)
 733    116    GKA GRAHAM, KEITH A. (MANHATTEN,IL,USA)
 438    38     MDW MACDONALD II, WALTER J. (WINCHESTER,ONTARIO,CANADA)
 304    210    OAR OKSANEN, ARTO (FIN-40950 MUURAME,FINLAND)
 257    31     RSE ROBINSON, STEPHEN E. (ROCKVILLE,MD,USA)
 249    19     GFB GOFF, WILLIAM (SUTTER CREEK,CA,USA)
 180    45     MTK MICHALIK, TOM (LYNCHBURG,VA,USA)
 144   <10     WJC WOJCIK, JAN (POTSDAM,NY,USA)
 135    16     VST VALENTINI, STEFANO (CRESPADORO,ITALY)
 126    10     GMZ GRAZIANI, MAURO (FUSIGNANO 48010 (RA),ITALY)
 121   <10     ARJ ARNOLD, JAMES E. (HUNTSVILLE,AL,USA)
 111    11     ZRE ZISSELL, RONALD E. (SOUTH HADLEY,MA,USA)
 99    <10     NMI NICHOLAS, MICHAEL (GLENDALE,AZ,USA)
 87    <10     WDZ WELLS, DON (MISSOURI CITY,TX,USA)
 85    <10     GRL GRANSLO, BJORN H. (,NORWAY)
 85     12     NLX NELSON, PETER ROBERT (VICTORIA 3820,AUSTRALIA)
 50    <10     RR  ROYER, RONALD E. (SPRINGVILLE,CA,USA)
 50    <10     CJS CASE, JAMES A. (KANSAS CITY,MO,USA)
 49    <10     WGR WALKER, GARY (SHERBORN,MA,USA)
 39    <10     LIW LILLER, WILLIAM (RENACA - VINA DEL MAR,CHILE)
 28    <10     SQC SUSLAVAGE, CHARLES A. (CORONA,CA,USA)
 27    <10     DIL DILLON, WILLIAM G. (MISSOURI CITY,TX,USA)
 12    <10     WJD WEST, JERRY DOUG (MULVANE,KS,USA)

 These points reflect observations from October 1, 2003 (beginning
of the AAVSO fiscal year) until November 6, 2003. As before, we don't
include the observation totals of those with less then 10 observations
so as to avoid betraying the CCD Points formula!
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     An archive of "CCD Views" is available at http://www.aavso.org/ccd-views.

     An archive of "Eyepiece Views," a similar newsletter intended for visual observers, is available at http://www.aavso.org/eyepiece-views.

 Good observing!

 Aaron Price, AAVSO Technical Assistant (PAH)
 Gary Walker, Chairman of the AAVSO CCD Committee (WGR)


Copyright 2003, American Association of Variable Star Observers
 

Keywords:
AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484