Timelapses

For the last two nights which were excellent, I played with Rachel's EOS 5D Mark III with the 24-105mm lens (I would have prefered a shorter & fix focal length) and a Polaris motorized tripod to add some movement to the camera during the night shots.

RAW image were preprocessed by Rachel with LightRoom. I then combined them with VirtualDub and added musics (from Jamendo web site) edited with Audacity.


On the night of july 28th I did one timelapse above the dome while observing several Be stars with the echelle spectrograph.

 

 

On the night of july 29th I took a timelapse of the milky way above the mountains from home with dramatic effect from the clouds. µAt the same time, I was doing long monitoring of the pulsating star BW Vul to get a second set of data to analyse... lot of work to do on this now.

Enjoy viewing those timelapses as much as I enjoyed making them! :-)

Be star QR Vul is in outburst

I have done several Be stars on the night of the 28th of july including QR Vul which has been seen in emission couple of times since 2008 but not recently. I was surprised to see that QR Vul was in emission in my spectrum:

Compare ith the spectrum taken back in may:

This is why Be stars are fun stars to observe with a spectrograph! :-)

BF Cygni

Excellent night tonight, with very good seeing (well, for the site; estimated around 3") and sky magnitude (with SQM) around 20.6.

I started with some known friends such as VV Cep and P Cygni and switched to a star of interest at the moment, the primary target scheduled for the coming OHP spectroscopy workshop: BF Cygni. This is a classical symbiotic binary star but the shape of some emission line (H beta for exemple) has the signature of strong jets emitted from the system.

Here is the observatory computer screen copy showing the guiding image, the spectrum (H alpha is very strong), the two CCD control (acquisition camera & guiding camera), the skymap area (around BF Cygni) and the telescope control:

Here is a view inside the dome, telescope pointed toward the target:

And the guiding camera long exposure (Atik Titan, 10sec) to see the field of view around BF Cygni:

BW Vul, a pulsating star

BW Vul is a variable star whose brightness changes every 4h50min. Spectroscopic study such as the one I did last night shows that the atmospheric absorption lines shift over the same period. This is due to the star pulsating radially, same as other beta Cephei - and BW Vul is the largest amplitude beta Cep stars ever observed.

The following graphs shows two spectra taken at different times, around sodium doublet:

 When you look over time, one can see that the two sodium lines are fixed (as well as several other ones). The small ones are absorption lines from our own atmosphere (vapor lines), and are of course stable (ie: no radial velocity) over the 6h observing time. The two sodium are the signature of interstellar sodium material which resides somewhere between us and the star, they are also not changing velocities relative to us.

The large absorption line around 5876 Angstroems is helium in BW Vul atmosphere which first shifts toward the red (ie: toward the right of the graph) as the stellar atmosphere compresses itself... up to a point when it bounces back - and does it twice with line doubling phenomenon, due to shocks inside this atmosphere:

 The following graph shows the evolution of the spectrum (dispersion = horizontal axis) over time (vertical axis, time going up when you go up), one can clearly see the star pulsating over the observing time:

You may notice a small absorption line between the two sodium lines; this is nickel which also moves (as the atmosphere moves) but as the temperature of the BW Vul atmosphere changes due to the compression (density) changing, there are moment when the line is not visible; nickel atoms are always there, but temperature is too high for the transition (ie: absorption) to take place.

BW Vul spectra acquisition (PRISM v10)

Night picture taken during spectra acquisition (see previous blog post)

Observatory by night

Clear night tonight. Full moon is illuminating the dome and the observatory so I took that opportunity to take some shots...