Re: interesting article on planned all-sky survey

[droege@snapmail.us]

Michael, and all,

I did see this paper.  I also looked for how they planned to reduce the
data and what they were doing special about wide angle observations. I
always look for a mag vs sigma plot.  If the paper does not have one then
I figure they are trying to "sell" the project.

The paper contained some comfort for my data.  There are a lot of nights
where for one reason or another the stars are somewhat trailed.  Michael's
pipeline seems not to mind this, and measurements on trailed nights are
similar to measurements on good tracking nights.  I am sure when the other
problems are removed that trailed data may not be the best, but even here
we shall see.

I continue to believe that I am doing the right thing by taking images in
near arbitrary directions.  This highlights the real accurracy of the
data.  Holding fields constant improves precision over accuracy but may
even mislead users more than carrying photon statistics with the data. 
;^)

I also note that my tass set up observes all stars at the same altitudes
and also within two degrees of the vertical in RA.  It is my hope that
this minimizes the problems with respect to positon in the sky which I
believe to be severe for this kind of data.

I also think that arbitrary pointings provide for a better chance to
process the data to improve the accuracy.

I should note that all these "opinions" await confirming data. They come
from spending a lot of time looking at data and trying to make sense of
it. Eventually I hope to work out data measurements that can come to
conclusios.  It is a tough business.

We shall see.  I continue to persue my version of GP's method and it shows
some promise.

Tom Droege

>
>   A recent issue of Publications of the Astronomical Society
> of the Pacific (vol 116, number 824, October 2004) contains an
> article of interest to TASSians.
>
>         "PASS: An All Sky Survey for the Detection of Transiting
>          Extrasolar Planets and for Permanent Variable Star Tracking"
>
>             by Deeg et al.
>
>   You can find this paper via ADS (I've cut the long URL below
> in half for clarity)
>
>       http://adsabs.harvard.edu/cgi-bin/nph-bib_query?
>           bibcode=2004PASP..116..985D&db_key=AST&high=416a79eb0011836
>
> or on astro-ph:
>
>       http://xxx.lanl.gov/abs/astro-ph/0408589
>
>   There is also a paper contributed to a conference in July 2004
> describing the first prototype camera in their system:
>
>       http://xxx.lanl.gov/abs/astro-ph/0409557
>
> I am somewhat disappointed not to be shown results from this prototype,
> since the authors write that they did collect data on a number of nights.
> They explain that the existing data were collected from a temporary
> set-up, while their planned survey requires an instrument which is
> both mounted so that it points in a fixed direction, and operated so
> that it observes the same stars at the same altitudes every night;
> therefore (I infer) the current camera's data is unworthy of being
> analyzed.
>
>   The planned system will use a novel system in which the cameras
> take short trailed images of stars always at the same altitudes in
> the sky (hence 4 minutes earlier each night) and use a sort of
> "trailed-aperture photometry" to measure the light from each star.
>
>                                              Michael Richmond
>
>
>
>
>
>