Reducing MONET data

20 Mar 2018 - Tim-Oliver Husser

tl;dr: for 3x3 images, please add an X offset of 2 pixels in order to get the images automatically processed by the reduction pipeline.

As you might have seen, we reactivated the pipeline and also started taking FLATs again, so that you can download fully reduced images.

For this to work, your images must have exactly the same dimensions as the calibration frames. This works fine in 1x1 and 2x2 binning. But in 3x3, unfortunately there is a little problem: The first 50 (unbinned!) pixels on the CCD are covered, so that they effectively serve as DARKs. Now we don’t want a binned pixel to cross this border. This means that for 3x3 binning, we take the calibration frames with an X offset of 2 pixels, resulting in 48/3=16 binned pixels in the covered area.

Long story short: for 3x3 binning, your CCD settings should look like this:

3x3 offset

Note: your reduced images will not undergo any dark/bias or flat correction, if the image dimensions do not match!

Shutter problems Monet/S

29 Sep 2017 - Tim-Oliver Husser

NOTE: this problem has been fixed by replacing the shutter!!!  (2018-MAR)

tl;dr: Please avoid targets in the Azimuth range 0-90° (North to East). Due to shutter problems you will not get good images!

It seems that we’re having some technical problems with the camera shutter at Monet/S: sometimes it opens only for a (too) short time and sometimes it doesn’t open at all. Apparently that’s connected to the position of the telescope, or more precisely, to that of the derotator.

For this test during the day with a closed roof we moved the telescope to different positions and took 5 pictures at each one. We expect some variations due to an inhomogeneous illumination of the roof, but for all mean count rates below 1000 we assuma that the shutter didn’t open. In the following plot the mean count rates are indicated by the radii of the circles and those smaller than 1000 are marked red:


As one can see that is a vertical strip in the azimuth range 0-90° (North to East), where the problem occurs. The numbers in the circles are the absolute derotator positions. Plotting the mean counts over those positions, we get the following plot:


So it seems that there is some range in the derotator rotation that causes the problem, probably too much strain on some cable. 

Therefore we recommend avoiding observations in that range for now. We will let you know as soon as the problem is fixed.

MONET/South science-image autoguiding in the works

14 Sep 2017 - Frederic Hessman

The open-loop (i.e. blind) guiding of the MONET telescopes is, well…., capable of being improved!  As the pointing model gets better, the blind pointing will get better, but a large steel telescope just isn’t designed to be so exact (small high-tech amateur telescopes can be so good that they essentially don’t need any additional help in guiding).   The best solution is to place an additional camera near the main science camera just for guiding, but we don’t have enough focal-plane space for this solution.  One of these days we’ll get the piggy-back telescopes working, but a non-aligned guider whose camera has to be rotated differently from the science camera is quite difficult to develop.

For projects where lots of science-images are being taken (e.g. photometry of an eclipsing variable, motion of an asteroid,…), we can use the short exposures to correct the guiding while the series is being taken.  Dr. Tim-Oliver Husser, our magical MONET-programmer, is testing such a system on MONET/South.  Here is an example of how well the telescope can track over an hour:

Science frame auto-guiding

As soon as the system is fully tested, we will add science-image autoguiding to all observations automatically.   Observations using just a few long-exposed images obviously won’t profit from this service, but most MONET projects will.

Taking flats with MONET

26 Feb 2017 - Tim-Oliver Husser

Monet/South is pretty much alive and working again with our new FLI camera. Starting now we’re accepting targets again!

And to get you ready, here is a small teaser featuring Eta Carinae:

Eta Carinae

MORISOT kick-off meeting in Potsdam

05 Dec 2016 - Frederic Hessman

Last week, the participants in the MORISOT (the MOnet Robotic Instrument for the Spectroscopy Of Transients) project met in Potsdam to discuss the final design of this exciting new instrument.

MORISOT will be a fibre-fed low-resolution (R=1000) spectrograph mounted on the MONET/South telescope that will operate independently of the imaging camera.  The science camera will act as an autoguider for the spectrograph, permitting us to obtain low-resolution spectra of quite faint objects.

The consortium brings together several new MONET partners:

The ability of obtain spectra robotically opens up both new scientific uses for the MONET/South telescope as well as new possibilities for the educational use.  The project icon shows an image of the impressionist artist Berthe Morisot painted by Edouard Manet with examples of low-resolution stellar spectra superimposed.