Claude Catala and
Reduction of Classical data
|Classical Observing with ESPaDOnS||ESPaDOnS in Queued Service Observing Mode|
|Characteristics and Performances||Other relevant documents|
ESPaDOnS is a bench-mounted high-resolution echelle spectrograph and
which was designed to obtain a complete optical spectrum (from 370 to 1,050 nm)
in a single exposure
with a resolving power of about 68,000 (in spectropolarimetric and 'object+sky' spectroscopic mode)
and up to 81,000 (in 'object only' spectroscopic mode).
In 2011 and 2012, CFHT undertook a small project to reduce all the ESPaDOnS data that had been taken over the first 3 years of ESPaDOnS, under Classical mode. Until then, only raw (unprocessed) data were available at CADC, and were then of limited use.
Processed data are now available to any registered user from the CADC query pages for CFHT data and CFHT data, advanced search.
The query can be made by instrument or target name, for example.
Important information regarding the processed data available, their format, and the reduction can be found in the Processed classical ESPaDOnS data page.
YOU WILL GET TWICE A MUCH FLUX IN THE RED compared to EEV1, and even a bit more flux in the blue too! To help PIs deal with the change, CFHT has prepared a Olapa-ready Exposure Time Calculator: New ETC for ESPaDOnS and Olapa
This new ETC is based on the one for EEV1, which was created by JF Donati. The interface and presentation are very similar.
This was accomplished by fabricating a triplet with a new design, new materials, and a new mechanical mount not using any glue at all, and by also installing a new ADC (Atmospheric Dispersion Corrector) whose prisms also are not held with glue either. Results of on-sky tests performed with these 2 new optical devices show a total crosstalk below 1%.
|Date||Nov 2009||Dec 2009||Jan 2010||Mar 2010||Aug 2010||Jul 2011||Jun 2012||May 2013||Sep 2014|
Some of the crosstalk left, along with its variation, is due to the Atmospheric Dispersion Corrector. This complex optical device probably still exhibits stress birefringence, and since its configuration changes as function of time (as a function of the telescope's position), this small stress birefringence introduces a small level of variable crosstalk.
Crosstalk is the contamination of one Stokes parameter (one type of polarization) by another Stokes parameter. For example, a linear polarization of 10% "leaks" and a small signal of 0.5% is recorded in circular polarization, alghouth there should not be any. In ESPaDOnS, crosstalk is caused by stress birefringence in a triplet lens and in the ADC, and is usually temperature dependendent.
The triplet lens used between June 18 2005 and February 2006 showed birefringence, with about 7% of Stokes V (circular polarization) ending up in Stokes Q and Stokes U. The cross-talk produces spurious continuum polarization, which does not affect most programs because ESPaDOnS is best used to measure polarization in lines and not in the continuum (measurement of continuum polarization with ESPaDOnS is very difficult as the instrument was not designed to do that).
The next triplet, installed in June 2006, had cross-talk around 2-3% (linear to circular, and vice-versa).
An improved triplet (with new optical design and new materials) installed in Oct 2008 initially showed low cross-talk, which unfortunately increased into 2009 (up to about 4% in June 2009). It is thought that curing glue was the cause. During the summer of 2009, it was also discovered that the ADC (Atmospheric Dispersion Corrector) also introduces a large amount of cross-talk.
Please see the ESPaDOnS known technical issues page for more details related to the first investigations of the crosstalk.
Classical Observers (Semesters up to and including 2007B) can consult the ESPaDOnS in Classical Mode webpage.
The drop of efficiency was roughly 1.0mag for the period Jan-June 2005 total (with respect to the inital and best throughput values measured on the sky). Between June 2005 and February 2006, the spare spare fiber bundle has exhibiting a 0.4mag loss of flux (again with respect to the best throughput measured on the sky).
Please see the ESPaDOnS known technical issues page for more details.
Please note the following:
|BEFORE July 2005
(with the script real_time_esprit)
|invert the sign of V and Q
the sign for U is OK
|AFTER July 2005
(with the script libre_esprit
or with Upena)
|invert the sign of U
the signs for V and Q are OK
Contemplating continuum polarization? Please consult the FAQ before you make any proposal. ESPaDOnS was not designed to do continuum polarization very well. See details on the Continuum Polarization page.
The engineering that took place in September 2004 was very successful. A brief summary includes a few figures and graphs. In November and December 2004, commissioning took place, with average weather conditions.
For official information and numbers, please see
official ESPaDOnS webpage.