Starship Asterisk*

What you have in the plot is light intensity vs. position. Combining this with what Lior did using the double CONCAM meteor, allows you to plot the light output vs. altitude. The light output is connected with the mass loss from the meteor by ablation, so using this kind of plot one can see where th...

http://www.space.com/php/multimedia/zoo ... ghts_world

This one shows the Earth at night; may be useful to combine with the daytime view now used to show the NSL locations.

Noah Brosch

Essentially, we see a sphere, or at least things that are very distant from us in all directions. The limit is that of "the visible Universe", which is the location where the expansion velocity equals the speed of light. Light signals from things further away have not had time yet to reach...

Bob, Lior:
We (Ezra and myself with a couple of other guys) plan to go down to the WO site this coming Sunday and will be there at night (though most of our work needs to be done during daytime). If there are things to try, pls give us a buzz.
Noah

Tilvi, our cameras normally use a lens that yields a field of view of 6 by 8 degrees. The frames are regular PAL TV, thus some 520 pixels or so across a frame. This gives the scale, which is about one arcmin per pixel.
Noah Brosch

Joe: Greetings, fellow earthlings. My apolgies for what is about to be a long post, but I have been curious about a number of things for a while, and have not gotten any answers at any of the astronomy sites I have been to: I know that an object in geosynchronous orbit effectively "hovers"...

Tilvi: I suggest you look at our recent work astro-ph/0409186 that deals with meteor light curves. I like your idea of subtracting one frame from another at the same ST; you may even create a ST template by median-filtering a number of frames at the same ST and use this to subtract fromthe frame wit...

Tilvi, in both cases (KP & RH) it does not seem that the fog is very thick. This is because in the KP movie it is possible to see some nearby instruments in some frames and in both movies some frames have striations, probably clouds seen through the fog. You might want to try some artivicial fog...

I am still wondering, if the images such as the one posted by Dr Nemiroff can be used for flat fielding. Because for me it seems to be the effect of either the lens or atmosphere and the not the actual pixel sensitivity gradient. The circular portion shows the brightness due to moon (?). http://www...

Bob: I guess that the frame you showed was taken during a foggy night when light was reaching the CONCAM from a nearby, high-optical-depth layer. This would make an ideal flat field because in such a situation the illumination of the lens is uniform. The "limb darkening" is, I believe, due...

Indeed, the accepted mode for obtaining flat-field (FF) images is to take the twilight sky. Anotehr option, used mainly by amateur observers, is to image an illuminated white screen that is close tot he telescope thus is very out of focus. Tis will not work for CONCAMs. The most 'modern' way to FF i...

Bob: "I think Betelgeuse would make a good NSL project for a student. NSL data gives the most continuous and most uniform stream of observations for Betelgeuse ever. At the least NSL data can quanitfy what variability Betelgeuse is showing this year." I agree and, just because Betelgeuse i...

Bob, Betelgeuse is a difficult object for the CONCAMs because it is a LONG PERIOD semi-regular variable. There is no "period" proper; the variability, as in many supergiants, is of hundreds of days. See for example http://www.solstation.com/x-objects/betelgeuse.htm or http://www.aavso.org/...

Vic, here is a "good practice" advice. Whenever you plot a graph, make sure you put in the units of both axes. In case of CONCAM photometry, I suggest to always look at intensity ratios (magnitude differences) between your target and a nearby comparison star. To convince your readers that ...

Vic, I think your idea of doing some systematic work on beta Per is very good. You may want to check the following sites: http://www.as.ap.krakow.pl/o-c/data/getdata.php3?BETA%20per and, in particular http://www.as.wsp.krakow.pl/minicalc/PERBETA.HTM which gives the times of recent minima. A nice sma...

Tilvi, the variability of Algol is permanent and the repeatability of eclipses is like that of a Swiss watch. Algol is a good target for beginning observers of variable stars because it is so reliable. You can find some information in the special entry AAVSO has on it at http://www.aavso.org/vstar/v...

Bob, the visibility of a dust storm by MODIS does not mean that the visibility at the top of the mountain is affected in the same degree. The Dust particles are heavy and would settle to lower altitudes. However, if the lower atmosphere is very turbulent, the dust will be ~uniformly distributed and ...

Tilvi, Algol (beta Per) would be a much better target because it is not so bright, and the variability amplitude is much larger. Algol varies between 2.2 and 3.5, the eclipses are deep with a period of 68 hours and 49 minutes and the width of the primary eclipse is about 8 hours.

NoahBrosch

Tilvi, I suggest to use additional data sets from other CONCAMs that would fill in the time gaps in your measurements. This would allow you to check whether the ratios you plot are valid for all cameras. I also suggest to concentrate on a star that has a well known strong variability (Algol, for exa...

Bob, "We were aware of some of the information you posted but not all. The info and great link you gave will be quite valuable." Glad to help. "Slight, monotonic "stellar variability" near the horizon might always remain indistinguishable from atmospheric extinction." T...

Bob, extinction close to the horizon does not behave as astronomy textbooks tell you it should do. In general, one uses the "regular" extinction correction: m(lambda)=m0(lambda)+k(lambda)*AM, where m(lambda) is the object magnitude, m0(lambda) is its magnitude outside the atmosphere, k(lam...

Lior, the cosmic ray (CR) problem is well-known in CCD astronomy. IRAF has a task called CRREJECT that you may want to look to. It is also possible to look for CRs by comparing a frame with the one immediately preceeding and immediately following it; this would flag one-frame transients and in most ...

It is VERY difficult to do absolute photometry. Every little bit of atmospheric and instrumental influence works against this. We find that with a telescope and CCD we can do relative photometry with ~0.05 accuracy. For this, we compare the instrumental magnitude of the target with that of a few nei...

I have recently been awarded a grant by the Israel Science Foundation to build two CONCAM-like cameras with highly enhanced capabilities relative to the existing devices. In this message, and hopefully in the thread that will follow it, I hope to receive insights from the members of this list. The p...

We experience quite often high humidity in the second halfs of nights, which can reach 100% and dewing on suraces. The result is a limitation in the observing time for our telescopes and dewing of the CONCAM lens. This kind of dewing is well-known by amateur astronomers. They use a dew remover, whic...