This project is a collaboration between Francois Kugel and myself (Jerome Caron). The setup is located in Observatoire de Chante-Perdrix, Dauban (MPC A77).

We use an apochromatic refractor d=80mm/f=600mm with a CCD camera ST8300 Sbig. The sensor is a full-frame CCD with 3352x2532 pixels. With this setup the field covered is about 1.3deg*1.7deg. The limiting magnitude is around 15.8.

The refractor is mounted onto a HEQ5Pro Sky-Watcher goto mount driven by Prism software. Francois is setting up the telescope every evening with clear sky remotely from his house nearby, and the acquisitions are made automatically over the night. Then I log in from my place in Netherlands in the morning to make the processing. We use the software TeamViewer.

Every night, the 80mm refractor is imaging up to 750 fields in the Milky Way (3 images per field). We are covering more than 3000 fields. Then we compare the pictures just taken with pictures taken a few days ago and we search for possible discoveries.

We have detected more than 1500 variable stars and compiled our own catalog. We are also following the activity of about 15 dwarf novae and report regular outbursts to the AAVSO list cvnet-ourburst. We show some interesting facts and obtained results below.

Some slides describing the survey (in French): survey_presentation_OHP_26-29avril2013.pdf

31 Jan 2014: end of outburst in Sgr

A last observation on 31.38 Jan 2014 confirmed that the outburst event detected by us is now finished.
Here is a report that summarizes our observations.

A plot with the final photometry:

A fit of the spectrum with a power law gives variations in lambda^(-2.4343):

23 Sept 2013: outburst detected in Sgr

More details on this page (French).
English version here.

Our survey scripts have detected a suspect star at the position 18:40:29.13 -27:09:59.3 (J2000.0). We measure it at CR=13.4. The DSS2-R field shows only a faint star close to this position with V=16.8, 17.2 or 17.3 depending on the catalog.
Here's the DSS2-R field and one of the follow-up images (thanks to P.Dupouy):

The star is clearly blue. A spectrum has been taken by T.Bohlsen showing a blue continuum and slight Hbeta absorption.

July-August-Sept 2013: corrections for GCVS and Misao stars in VSX

We detected a few variables where the official position indicates a constant star nearby the real variable. Our findings have been confirmed by AAVSO (for all stars) and transmitted to INASAN in Russia (for GCVS stars):
Here's a second batch of corrections for GCVS variables, confirmed by AAVSO and sent to INASAN:

Nova Delphini 2013

We missed it! We observed the position of the nova on Aug 12.0904 UT and did not see any object brighter than mag = 15.2 CR.
We detected it a few days later, see our detection image here.

August-September 2013: fast variables Dauban V239-V250

These variables have been detected by our survey. We perform additional observations with a Meade LX200, to confirm the variability and type.
See the lightcurves for all variables on this page.

So far we succeeded to proove that 8 stars are eclipsing binaries. See for instance this plot for Dauban V242.

Thibault de France also observed Dauban V248 and found it is a RR Lyrae star!
Based on his data we find a period equal to 0.441454 days.

July 2013: observation of cepheids Dauban V16-V17-V18-V19

These 4 bright cepheids have been discovered by our survey. They have periods in the range 11-18 days.
We are making a finer photometry with a 200mm telescope. Here are preliminary results:

04 July 2013: detection of symbiotic nova OGLE-2011-BLG-1444 = VVV-NOV-003

This star was detected by our survey on 04 July 2013 due to its moderate variability.

It caught our attention as we could not find any known object at this position on DSS2-IR and 2MASS, which we thought was ruling out the possibility of a Mira. Looking at earlier dates, we found several images from our survey showing the star with a similar brightness over the period from 24 April 2012 to 12 July 2013. We don't have images that go far enough in the past to show the field without the star. So we were a bit confused...

This was actually a very unusual (and rare) type of nova. For more information, see the following links: telegram 5212, telegram 5215, OGLE page.

In 2013 we got the following photometry. Air mass is large for all measurements (~4.5). We use a yellow filter cutting <500nm which hopefully reduces atmospheric effects.

object 2013 Mar 21.1880 11.5
object 2013 Apr 10.1629 12.1
object 2013 May 11.0748 12.2
object 2013 Jun 01.0127 11.6
object 2013 Jun 04.0204 11.5
object 2013 Jun 15.0242 11.7
object 2013 Jun 25.9484 11.4
object 2013 Jul 04.9256 11.2
object 2013 Jul 12.9040 11.5

Our earlier images taken in 2012 suffer from calibration problems and unfortunately cannot be used for photometry. Nevertheless we have very clear images of the star at these dates:

2012 Apr 25.14592012 Jun 21.96902012 Jul 12.88982012 Jul 21.8773
2012 May 02.10572012 Jun 25.97692012 Jul 14.89982012 Jul 25.9078
2012 May 03.12382012 Jul 07.90632012 Jul 16.89812012 Aug 24.8296
2012 May 27.07502012 Jul 10.92002012 Jul 18.87772012 Aug 27.8257

June 2013: correction in GCVS/VSX

Here is another correction for a GCVS variable star. The correct position was also mentionned in the Skiff catalog for spectral types. The entry in AAVSO-VSX has been updated:

11 May 2013: improved astrometry

I spent a full week of programming to improve the astrometric reduction, with the bad weather helping. Accurate astrometry is essential for measuring magnitudes, because we need to know where to measure on the image, given the alpha and delta coordinates!

The new algorithm was tested with 200 images taken in Sagittarius. This area of the sky is difficult due to visible structures in the Milky Way (giving variable star density, gradients in the sky background) and low elevation. Several images were also contaminated with clouds. Each image was divided in 48 zones, and the median astrometric residual was calculated for each zone. The residuals are below 0.5 pixel in 99.6% of the cases. Here is an histogram of the obtained values:

The new algorithm has additional steps as compared to the one in the online version of Aspylib. The purpose of these extra steps is to make sure that the list of stars used for the fit covers the image uniformly.

April-May 2013: corrections for GCVS stars

We detected new errors about the identity of GCVS variable stars. Our corrections have been accepted by INASAN (in charge of GCVS) in Russia.
The entries in AAVSO-VSX have been updated:

20 April 2013: Dauban catalog update

The Dauban (internal) catalog of variable stars has just been updated.

Over the last 3 months the total number of detected variable stars increased from about 1700 to more than 2700. We have more than 750 discoveries.

dateknown variablesdiscoveriestotal

18 February 2013: corrections in GCVS

During our observations, we have detected 3 GCVS stars with a mistake about the variable identity (V0348 Cep, V0513 Cep, WY CMi). In all cases, a second star located at 8 to 12 arcsec from the catalogued star, was the true variable. This information has been validated by AAVSO and transmitted to the Institute of Astronomy of the Russian Academy of Sciences (INASAN).

The entries in AAVSO-VSX have been corrected:

Images for V0348 Cep:
On the left, the field image from DSS2-R. The cross shows the old GCVS position, the arrow shows the Dauban detection. The Dauban images are on the right.

11 February 2013: first officialisation of discoveries

The first Dauban variables are published: 15 miras and 2 cepheids!

nameconstellationJ2000.0typemag rangeperiod (days)AAVSO-VSX
Dauban V1Vul19 40 28.88 +27 00 02.8M11.4 - 14.6: CR355 link
Dauban V2Vul20 38 07.90 +21 05 21.5M11.6 - <15.6 V228 link
Dauban V3Sge18 58 21.07 +20 47 57.5M13.0 - <17.6 V271 link
Dauban V4Vul19 48 55.65 +20 31 40.8M12.5 - <14.9 CR-- link
Dauban V5Sge19 05 38.87 +20 46 26.6SRA:11.6 - <12.9 CR241.9: link
Dauban V6Vul20 30 46.80 +26 00 38.3M:11.4 - <12.5 CR-- link
Dauban V7Sge19 33 33.27 +19 10 47.8M:11.8 - <13.7 CR-- link
Dauban V8Vul20 38 01.56 +27 54 41.2M:12.5 - <14.6 CR-- link
Dauban V9Vul19 23 22.03 +23 49 25.2M:11.1 - 14.6: CR419: link
Dauban V10Vul19 28 27.87 +23 11 44.4M:12.6 - 14.7: CR173: link
Dauban V11Vul19 34 03.37 +20 41 32.1M:12.8 - <14.6 CR379: link
Dauban V12Vul19 38 07.13 +23 23 54.1M:12.0 - <14.2 CR-- link
Dauban V13Sge20 05 00.58 +20 03 50.3M15.0 - <17.0 V397 link
Dauban V14Her18 52 44.84 +21 24 10.5M11.4 - <16.7 V331 link
Dauban V15Vul19 04 38.58 +21 17 04.2M12.1 - 16.8: CR394: link
Dauban V16Vul20 00 02.48 +29 11 12.8CEP:12.3 - 13.1 CR18.51 link
Dauban V17Cyg20 16 45.29 +37 07 44.7CWA11.1 - 12.1 CR11.87 link

20 January 2013: Dauban catalog update

As of 20 January 2013, we have detected the variability of 1762 stars.
- 1285 of them are known variables.
- 477 are potential discoveries, that do not appear in AAVSO-VSX.

More information here.

29 October 2012: Outburst of TW Vul

This suspected dwarf nova has been seen two times only in outburst, in 1904 and 1927.
We detected an outburst on 29th October 2012.

We measured the following magnitudes:

targetUT (geocentric)CR magnitudeinstrument/exposuresobservers
TW Vul2012 Oct 18.8179>15.7T80/600, 3*10secJ.Caron / F.Kugel
TW Vul2012 Oct 24.8184>15.7
TW Vul2012 Oct 29.841613.1
TW Vul2012 Oct 30.738213.2
TW Vul2012 Nov 02.817715.1
TW Vul2012 Nov 05.808915.9T400 f/3, 5*10secF.Kugel / C.Rinner
TW Vul2012 Nov 06.8030>15.5T80/600, 3*10secJ.Caron / F.Kugel

The AAVSO-VSX entry has been updated: see here.

Klaus Wenzel was very interested by this outburst. He wrote a short publication in a German journal to report our discovery and subsequent observations from other amateurs (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne, BAV in short). Thanks to him! See here.

01 September 2012: new setup

More information here.