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Clear skies
Wolfgang
--
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO
http://mira.aavso.org/pipermail/aavso-p ... 02207.html
[Aavso-photometry] Low-pressure sodium lights and photometry
Wolfgang Renz w_renz at ...
Sun Feb 26 13:52:54 EST 2006
Hello Bob
Zitat:
I'm an astronomer at Ohio Wesleyan University, which is about 20
miles north of Columbus. OWU owns and operates Perkins
Observatory (
www.perkins-observatory.org), which houses a 32-inch
reflector. Because it's f/17, it's not very useful for CCD photometry as
the field of view is about 3x2 arcmin with our SBIG ST-8E. Thus, the
telescope is used mostly for visual observing by students and the
many visitors to our twice-weekly public programs. However, I do use
8-inch and 12-inch telescope on site for BVRI photometry.
The large reflector could be used for photometry too. You just would
have to select your targets appropriatly. With such a small FOV and
a good tracking/guiding mount you could e.g. concentrate variables
with close companions, variables in globular or smaller open clusters
etc.
Zitat:
To make a long story short, there is a strong possibility that a Wal-
Mart Supercenter and a Toyota dealership will be built within a mile
of the observatory to the south. The good news is that both would be
on land annexed by the city (pop. ~22,000) in which OWU is located
(the observatory is on the outskirts of town) and thus subject to lighting
code restrictions which would require them to use low-pressure sodium
lamps on 28-foot poles, as opposed to typical broad-spectrum parking
lot lights on 40-foot poles. (Wait until the Toyota dealer sees what his
cars look like under LPS light!) The bad news, of course, is that the
lovely yellow glow will still most likely annihilate the naked-eye views
from the observatory grounds and degrade telescopic views of objects
like galaxies and clusters.
If the major light pollution source are the LPS lights, any broad band
LPR filter that rejects the 588 nm Na emission line will help to supress
their light output. Getting rid of HPS light output, that converts the 588
nm Na emission line to a much broader emission around 588 nm
and other wavelengths is much more difficult (even the IDAS LPR isn't
ideal for this purpose).
See:
Micheal Koppelmann - High-Pressure Sodium Vapor Lamp Spectrum
http://www.lolife.com/astronomy/na.jpg
Christian Buil - Spectral calibration - Sky light pollution High Pressure
Sodium lamp types (Castanet Tolosan - France)
http://www.astrosurf.com/buil/us/spe2/hresol4.htm
http://www.astrosurf.com/buil/us/spe2/c ... burb_1.gif
http://www.astrosurf.com/buil/us/spe2/calib2/sky.gif
http://www.astrosurf.org/buil/filters/sodium.png (HPS!)
http://www.astrosurf.org/buil/filters/sodium_1.jpg (HPS!)
SCHIAPARELLI OBSERVATORY - Light Pollution
Light Pollution at Campo dei Fiori Observatory
http://www.astrogeo.va.it/astronom/spet ... _lumen.htm
http://www.astrogeo.va.it/astronom/spet ... nq_lum.jpg
SBIG - DSS-7 Deep Space Spectrograph
http://www.sbig.com/dss7/dss7.htm
http://www.sbig.com/dss7/image028a.gif
http://www.sbig.com/dss7/image030a.gif
...
Christian Buil - Astronomical filter curves (LPR)
http://www.astrosurf.org/buil/filters/c ... ON%20POWER
Don Goldman - Light Pollution Filters
http://www.astrodon.com/oldsite/LPSFilters.html
Hutech Astronomical Products - IDAS Light Pollution Suppression
Filters, Limitations and Common Misconceptions
http://www.sciencecenter.net/hutech/idas/lps2.htm
Ron Wodaski - Evaluation of Hutech IDAS light pollution
suppression filters
http://www.wodaski.com/wodaski/IDAS_review.htm
Zitat:
I have two questions for the list. Any insight would be greatly
appreciated!
1. It seems to me that LPS lights should have a minimal effect on BRI
photometry, but that V might be a different story. Am I correct in my
thinking? Has anybody succeeded in doing good V-filter photometry
in the presence of strong LPS skyglow? Any tips?
LPS lights has a single major emission line at 588 nm and therefore
should show up in the images of the photometric V AND Rc band filters
about equally (at ~ 50-70% of the max transmission of the filters).
For photometry the usage of LPR filters is of course not allowed. As
with any imaging under light polluted skies, you'll need to make longer
exposures to reach the same SNR for photometry. With using the linear
CCDs the effects of light pollution can be handeld much better (even
without a LPR filter) than with the non-linear film or visually. See e.g.:
Jay R. Ballauer - Does Light Pollution Affect CCDs
http://www.allaboutastro.com/Articlepag ... tCCDs.html
Robert Bateman - LPR Problem, The effects of an LPR on a large scope
http://www.robertb.darkhorizons.org/lpr.htm
Christian Buil - Urban astronomical observations (LPR filters evaluation,
spectroscopy, ...)
http://www.astrosurf.org/buil/city/result.htm
Tony Flanders - Aperture versus Light Pollution
http://mysite.verizon.net/vze55p46/id1.html
Zitat:
2. Does anybody know of references for estimating the level of skyglow
from a given number of LPS lights at given wattages from a given
distance? It would certainly help me make my case more effectively in
community meetings if I could give some quantitative estimates of how
bright the skyglow will be. Alternatively, does anybody know of any
photos showing skyglow from LPS lights at a single large parking lot
from a mile or a few miles away? There aren't any comparable facilities
in my area.
I don't know references for estimates as they depend probably on too
many factors. But there are a number of sites that have images with
obvious light pollution.
http://www.darksky.org/
http://www.astrosurf.com/re/light.html
http://dipastro.pd.astro.it/cinzano/en/index.html
http://dipastro.astro.unipd.it/cinzano/en/sbeam.html
http://dipastro.astro.unipd.it/cinzano/papers.html
http://cfa-www.harvard.edu/cfa/ps/nelpag.html
...
Sky and Telescope - Secrets of Deep-Sky Observing
By Alan M. MacRobert
http://skyandtelescope.com/howto/visual ... e_78_2.asp
http://skyandtelescope.com/resources/darksky/
Hutech Astronomical Products - IDAS Light Pollution Suppression Filters
http://www.sciencecenter.net/hutech/idas/lps.htm
http://www.sciencecenter.net/hutech/idas/lps1.htm
http://www.sciencecenter.net/hutech/idas/lps3.htm
http://www.sciencecenter.net/hutech/idas/tanaka.htm
Clear skies
Wolfgang
--
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO
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