Hallo,
falls sich noch jemand für eps Aur interessiert: es wird langsam interessant.
Die eclipse beginnt im Aug. 2009.
Liebe Grüße
Lothar
---------- Weitergeleitete Nachricht ----------
Subject: Epsilon Aurigae Campaign Newsletter #3
Date: Montag, 7. Januar 2008 19:53
From: Jeff Hopkins
To: Robert Stencel
2009 Epsilon Aurigae
Eclipse Campaign Newsletter #3
Winter 2007/2008
January 2008
Dear Colleagues,
One more year, actually around 18 months) before first contact. Time
is swiftly passing. Now is the time to get equipment checked out,
calibrated and techniques fine tuned. Now s also a good time to get
in sync with the star system. By that I mean see what numbers it
produces for your equipment. See how close your data is to other data
for the same time. See what adjustments are needed to get your data
to agree closer. Because the epsilon is around 5 degrees for the
comparison star lambda Aurigae, extinction is important. You can use
lambda to determine a rough extinction for each night. This is
another item that can be worked out now before first contact.
*************************************
News
The AAVSO has declared "Variable Star of the Year - Epsilon Aurigae."
A write up by Arne A,. Henden and John R. Percy on this is on pages
274 - 275 of the "RASC Observer's Handbook 2008."
In addition the United nations has declared "2009 The International
Year of Astronomy."
See
http://www.iau.org/iau0702.486.0.html
The AAVSO has plans for a "capstone" project for IYA 2009 involving
the monitoring of epsilon Aurigae. See
http://www.aavso.org/aavso/iya.shtml
For details see the AAVSO Poster Paper
http://www.aavso.org/images/iya-aas-poster.pdf
*************************************
Campaign Members
Dr. Serdar Evren of Maharashtra India writes he is using a Vilnius
photometer with UBVR Johnson filters on a 48 cm Cassegrain telescope.
Dr. Lothar Schanne of Germany continues to do spectroscopy work. He
is also looking for photometric help for two other stars, P Cyg and
WE 140. If you are interested, please contact him directly at "Dr.
Lothar Schanne" <
l.schanne@arcor.de>
07 December 2007
Dr.Mukund Kurtadika of Maharashtra India write that he is using an
SSP-3 to do BVRI photometry of epsilon Aurigae. He is having trouble
with star drift, but once that is solved the data should be very good.
31 December 2007
Hans-Göran Lindberg of Germany wrote: "I have a Starlight Express
HX-516 B/W Camera(PIXEL 7.4*7.4)ccd 4.9*3.6mm and I planing to add a
50 mm camera lens to it which will give me around 5 deg. view around
the star."
4 January 2008
Brian McCandless at the University of Delaware has offered to follow
epsilon Aurigae in the JH infrared bands using his SS-4 and 14"
Celestron.
*************************************
The Project
Epsilon Aurigae is an ideal star system for backyard observers in
light polluted suburban areas. It is bright (3rd magnitude) and easy
to find and observe. The next eclipse of this 27.1 year variable star
system will start in the summer (July/August) of 2009. The eclipse
will last nearly two years. A strange mid-eclipse brightening was
seen during the last eclipse. The star system is variable outside of
the eclipse which make things even more interesting. The nature of
these out-of-eclipse variations are still not understood. While the
basic period seem to be around 60 to 70 days the exact period seems
to vary.
It will be most important to get the best coverage during the contact
points (1st, and, 3rd and 4th) as well as the mid-eclipse. Because of
weather concerns and sky position during the summer months, as many
observers as possible will help complete the coverage. Because the
declination of the system is +44 degrees, the higher the observer's
latitude, the better the coverage during the summer months.
During the last eclipse, observes did not get excited until the
eclipse started so there is few photometric data before and during
first contact. Hopefully this time will produce better coverage.
*************************************
Single Channel Equipment
It is also ideal for single channel photometers. These include home
made PMT (Photomultiplier Tube) based UBV photon counting units, the
Optec SSP-5 (UBV analog), solid state instruments such as the SSP-3
for BVRI observing and the SSP-4 for infrared JH bands observing. For
solid state detector work the larger the telescope the better. While
an 8" telescope may suffice for the SSP-3, at least a 12" is
recommended for the SSP-4. For the PMT based UBV work, most anything
from 6" up to 18" can be used. The larger telescopes may saturate the
PMT, however.
For those who are interested in photon counting, I have received
several requests for high voltage power supply and pulse conditioner
printed wiring boards. I have prototype PWB for a regulated HVPS that
I am still testing. This is based on the Boyd design using a band gap
reference. If anyone else is interested in pursuing this, and if I
get enough interest, I will make more PWB for both the HVPS and pulse
conditioner. Several companies make very low cost (~$15) low voltage
power supplies that can be used to power these boards. Please contact
me directly if you have questions or are interested in photon
counting.
*************************************
CCD Equipment
There are some problems with finding observers using single channel
detectors. Most observers are now into the CCD world. While CCD
instruments are certainly great, some of their advantages are
actually disadvantages for the epsilon Aurigae project. The star
system is too bright. Even with an 8" telescope to stay in the linear
region of the CCD sub-second exposures are needed. this presents a
problem with atmospheric scintillation. Typically at least 10 seconds
of observing is needed to even out the scintillation variations. Most
CCD photometry is done such that both the comparison and program
stars are in the same image. The common comparison star is lambda
Aurigae and is located some 5 degrees away. This is well beyond the
field of view of even large detectors. This means doubling the work
and imaging the program star and then the comparison star. This
negates much of the advantage of CCD photometry. While there are good
comparison stars closer to epsilon Aurigae the are too faint to be
imaged along with epsilon. Typically they are around 6th magnitude.
The dynamic range of the CCDs is not sufficient to allow these stars
to be imaged at the same exposure epsilon is imaged at.
Can CCD instruments be used to observe epsilon Aurigae? Yes!
In The Society for Astronomical Sciences Newsletter Vol. 5 Number 3,
Bob Buchheim discusses using an aperture mask to cut down the area
yet retain resolution and scintillation reduction of a larger
telescope. While this helps with the brightness issue, it does not
solve the problem of getting the comparison and program star in the
same image. See
http://www.socastrosci.org/
At the Hopkins Phoenix Observatory we have been experimenting using a
50 mm camera lens with a DSI Pro CCD camera to do BVRI photometry of
epsilon Aurigae. Even using the 50 mm lens requires the lens to be
stopped down to F.4.0 to keep the R band data in the linear region of
the detector. We found that using the 50 mm lens at F/4.0 with 5.7
second exposures for the BV and I bands and 2.0 second exposures for
the R band worked well. Each image is a composite of 20 images
stacked. Even at only 2.0 seconds the R band data peak ADU counts
were over 36,000. Reduced data showed the data spread for 3 set of
images for each filter to have a standard deviation of close to 0.01
magnitude. More data will be taken, but so far this looks like an
excellent means to do CCD BVRI photometry of epsilon Aurigae.
A Mogg adapter was used to couple the DSI Pro camera to the 50 mm
lens. While a filter wheel was tried, focus could not be achieved. We
were required to use the original filter slide that came with the DSI
Pro. While not as nice or easy to use as a filter wheel we were able
to focus. Details of this project will be posted on our web site at a
later date. For information on the Mogg adapter see
http://www.webcaddy.com.au/astro/adapter.asp
Note: As an experiment an Orion equatorial mount ($50) was tried with
this and it worked fine. No telescope needed and it's powered by a 9
V battery. See:
http://www.telescope.com/control/produc ... t_id=09055
*************************************
HPO Fall 2007 UBV Observations
JD
2,450,000+ V B U
09/18/2007 4362.8275 3.059 3.638 3.714
09/19/2007 4363.8011 3.052 3.615 3.675
09/23/2007 4367.8011 3.044 3.622 3.679
09/24/2007 4368.8157 3.060 3.631 3.708
09/25/2007 4369.8059 3.052 3.624 3.694
09/26/2007 4370.8108 3.036 3.620 3.701
09/29/2007 4373.8018 3.060 3.623 3.689
10/11/2007 4385.7788 3.056 3.616 3.688
10/13/2007 4387.7816 3.045 3.615 3.684
10/14/2007 4388.7837 3.051 3.613 3.688
10/15/2007 4389.7816 3.048 3.613 3.672
10/19/2007 4393.7837 3.036 3.600 3.686
10/22/2007 4396.7802 3.034 3.595 3.670
10/23/2007 4397.7851 3.031 3.595 3.689
10/24/2007 4398.7983 3.038 3.592 3.687
10/26/2007 4400.7795 3.028 3.588 3.689
11/01/2007 4406.6872 3.043 3.597 3.650
11/01/2007 4406.7865 3.037 3.611 3.722
11/13/2007 4418.8024 3.074 3.645 3.802
11/14/2007 4419.8115 3.066 3.656 3.803
11/18/2007 4423.7816 3.085 3.668 3.814
11/19/2007 4424.7136 3.084 3.664 3.799
11/19/2007 4424.7948 3.075 3.669 3.830
11/20/2007 4425.7830 3.083 3.676 3.835
11/05/2007 4410.7837 3.030 3.586 3.696
11/23/2007 4428.7788 3.099 3.686 3.834
12/02/2007 4437.7219 3.096 3.685 3.835
12/03/2007 4438.7330 3.082 3.686 3.822
12/04/2007 4439.7240 3.096 3.679 3.829
12/08/2007 4443.7219 3.085 3.665 3.805
12/12/2007 4447.7441 3.073 3.655 3.805
12/13/2007 4448.7240 3.075 3.650 3.787
12/15/2007 4450.7399 3.068 3.641 3.776
12/17/2007 4452.7205 3.067 3.634 3.764
12/18/2007 4453.7240 3.057 3.631 3.780
12/21/2007 4456.7913 3.049 3.614 3.769
12/22/2007 4457.7205 3.051 3.613 3.750
12/23/2007 4458.7254 3.041 3.601 3.742
12/23/2007 4458.7427 3.046 3.605 3.754
12/25/2007 4460.6892 3.040 3.605 3.720
12/26/2007 4461.7101 3.048 3.606 3.748
12/29/2007 4464.6906 3.044 3.614 3.735
12/30/2007 4465.7212 3.039 3.608 3.754
12/31/2007 4466.7177 3.040 3.603 3.739
*************************************
Report from Bob Stencel:
[
http://www.du.edu/~rstencel/epsaur.htm ]
The science goals for observing epsilon Aur are several and include:
[1] photometry: help determine whether the ~0.1 mag quasi-periodic,
out of eclipse light variation is due to the F supergiant star, or
related to excitation of disk material (UV and infrared spectra);
and, have that variation determined well enough to constrain whether
the mid-eclipse brightening seen previously is merely F supergiant
variation or could be a central clearing in an inclined disk;
[2] spectroscopy: a "disk trailing wake" appears to influence the
light curve and spectra only after mid-eclipse (Canavaggia 1980,
Ferluga and Mangiacapra, 1991), but pre-eclipse observations are
needed to determine whether material is symmetrically distributed
about the disk along the orbit;
[3] directly test the Huang disk model interferometrically, to
witness whether the single F supergiant stellar disk (2.1 milli-arc
seconds measured diameter) does bifurcate into a pseudo-binary during
eclipse due to the dark disk superpositioning;
[4] confirm the polarimetry results obtained during the previous 1984
eclipse (Kemp et al. 1986).
Interferometric measures were conducted twice so far during
autumn/winter 2007 using the Palomar Testbed Interferometer, first on
Oct.19 then on Dec.27, 2007. Reduction of data from the October
measurement, obtained during local V maximum light, confirmed
published values close to 0.002 arc seconds diameter for the F star.
The late December data have not yet been fully processed, but they
too were obtained during a local maximum in V band, although the U-B
color was slightly redder than during the October maximum light.
More observations are scheduled for the coming weeks to examine
pulsation-related diameter changes.
The AAVSO and IAU have become interested in the epsilon Aurigae
eclipse campaign. We have been informed that AAVSO is preparing to
highlight epsilon Aurigae as one of its Variable star of the season
entries at web site: [
http://www.aavso.org/vstar/vsots/]and encourage
eclipse campaign participants to visit the site for further
information. The IAU recently won United Nations approval to conduct
an International Year of Astronomy, IYA, in 2009. The US committee
wants to adopt epsilon Aurigae for its Citizen Science activity,
among others in 2009 and beyond: [
www.astronomy2009.us]. Watch for
news about these developments in future campaign newsletters.
*************************************
Anyone wishing to contribute to the Newsletter, is most welcome.
Please send contributions to me at phxjeff(==>)hposoft.com.
In addition to sending this directly to those who have expressed an
interest in epsilon Aurigae, I will post this on the campaign's web
site.
Anyone not desiring to receive these Newsletters, please e-mail me
and I will remove your name from the list.
http://www.hposoft.com/Campaign09.html
Jeff
--
Jeff Hopkins
HPO SOFT
Counting Photons
http://www.hposoft.com/Astro/astro.html
Hopkins Phoenix Observatory
7812 West Clayton Drive
Phoenix, Arizona 85033-2439 U.S.A.
(623)849-5889
(623) 247-1190 (Fax)
www.hposoft.com
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