M42 2007-10-20/21

As the Saturday night was specially good for observation from ESAC, Leo, Michel and me met here to observe something after the moonset. Despite the good atmospheric conditions, the light pollution was important (more than other times?...), thus we pointed the telescope to one of the brightest deeps ky targets: the Great Nebula of Orion (M42).

The following two images show the results. Both images were captured using a C8 SCT with a Canon Rebel 400D attached to the primary focus. Using an ISO of 1600. The first one is the result of the combination of three exposures of 30 seconds with wide band RGB filters.

The second image is a combination of two exposures of 60 second with narrow filters Red:H-alpha and G: OIII and a 30 seconds exposure with a wide band Blue filter.

After we pointed the telescope to Mars but the images must be still processed. As soon they are, they will be posted here.

Fabra Observatory 2007-10-09

Last week, I was with a friend, Antonio Bernal, at the Fabra Observatory of Barcelona (map) using a 1900's 38 cm double refractor (visual and photographic) measuring double star separations with a restored micrometric fil counter (from 1900 too). The following pictures show the telescope in operation.

This telescope was widely used during 100 years for astrometry and several minor solar bodies were discovered from here. As a result they have spanish names (Hispania, Barcelona, etc.). The observatory has also a huge collection of photographic plates covering around 80 years. Think about what they can produce if they are digitalized one day... However, the most spectacular achievement was the discovery of the atmosphere ot Titan in 1908 by Comas Sola, the observatory founder, observing the satellite limb darkening. It was published in 1908 in Astronomische Nachrichten and confirmed by Kuiper in 1944.

Today, the telescope is in operation but due to the high light pollution caused by the city it can be used only for some astrometric and planetary observations. The following pictures of the dome and the city show clearly the effect of the light pollution.

After its restoration, Antonio is using the telescope to measure today the separation of double stars that were reported before 1950. So, he hopes to update the double star catalogues confirming the observations and derive orbital information of the double systems. Additionally there are also public visiting tours and in special events they organize some public observations.

Sputnik-1 - 50 years anniversary

Next Thursday, October 4th, 2007, is the 50 anniversary of the Sputnik-1 launch.


It is very surprising for me that ESAC has not any scheduled activity. Some people, me too, consider that it was the beginning of our business and it should be celebrated. The space part of course... (the astronomy part is probably the second oldest business of the human history... ). Therefore, to solve in some way this lack of celebration, I have made a simulation of the event and I post it here.

It is a Celestia simulation of the first Sputnik-1 orbits.Celestia simulation of the first Sputnik-1 orbits. The orbital elements are tabulated in the NORAD archives and they are valid for The orbital elements are tabulated in the NORAD archives and they are valid for October 1957. After the high atmosphere drag and other low orbit perturbations caused the decay of the orbit until the satellite catastrophic reentry in the atmosphere in January, 1958. It reproduces quite well the reported passages.


The spacecraft attitude is an inertial extrapolation of the attitude of the launcher after the deployment.

The rotation period (around 6 revolutions per minute) was roughly estimated with the observed rotation of the Faraday field of the dipoles of the antennas. Rotation arund the major revolution axis was reported by Bracewell and Garriott in 1958 in a paper in nature.

A good historical compilation of the events behind the Sputnik can be found here. In the following links, some historical movies about the event can be found.









An acceptable dramatic reconstruction is shown in the BBC documentary "Space Race". Some excerpts of the series can be found also in youtube.