AsPyLib: a library for image processing
Since 2010 I am developping scripts for CCD images processing in Python. A lot of functionalities are available (geometrical transforms, star detection and PSF fit, aperture photometry...). Python is a very pleasant langage, easy to step in, allowing real-time script editing.
For more detail have a look at these pages.
Quick asteroid ephemeris
To identify potential targets for lightcurve measurements, I use Python scripts that download orbit parameters from JPL horizons Telnet server, and compute quick ephemeris. More details here.
OHP 2011 Spectroscopy Workshop
More details here.
CCD astronomy with polluted sky
I live in the city of Leiden (Netherlands). This is one of the worst places in Europe for astronomy, with strong light pollution and very low altitude over sea level. This link gives an overview of my situation !
But I still manage to make some interesting observations with a CCD camera. My main interests are: imaging, photometry of asteroids and variable stars.
29 Jan 2011 - 09 Feb 2011: photometric measurement of (121) Hermione. This is a big asteroid with a small satellite, but I could not observe it (no eclipse). More details here.
21 Feb 2011 - 18 Apr 2011: photometric measurement of (202) Chryseis. This asteroid is quite bright, and appears on the CALL list. The period is very close to 12h so long periods of time are needed to measure it, so that its phase wrt Earth time slowly drifts over a full period. The official period (15.74h) is wrong. More details here.
08 Apr 2011 - 24 Apr 2011: light curve of (449) Hamburga. This asteroid is on the CALL list. Due to limited visibility to the west from my observing site, and the nights shortening, it was a bit adventurous to measure this slow-rotating target. Anyway the measurements were still useful and a period was estimated, see here.
02 May 2011 - 09 May 2011: light curve of (1069) Planckia. More details here.
Some other measurements:
29 Jan 2011: lightcurve of (66) Maja, see here.
06 Apr 2011: lightcurve of (138) Tolosa, see here.
20 May 2011: observation of TrES-3b transit in front of star GSC 03089-00929. More details here.
21 May 2011: observation of HAT-P-3b transit. More details here.
08 Apr 2011: lightcurve of GU Leonis, an eclipsing binary. More details here.
02 July 2011 - 04 July 2011: discovery of an eclipsing binary, type W Uma, in Cygni. The lightcurve has been processed by R.Behrend, see here. The magnitude range is 13.0 to 13.6, with a period 0.30072 days. It has been submitted to the AAVSO VSX database, see here.
09 July 2011: discovery of a small eclipsing variable (magnitude close to 14.5) in Cygni. More details here.
10 July 2011: discovery of a small pulsating variable, of type delta Scuti (magnitude close to 14.5) in Cygni. More details here.
9-20 Jan 2011: NGC891, first pictures with the VISAC.
28 Jan 2011: M1 (crab nebula).
23-30 Apr 2011: pictures from NGC3718, M51, M63 with the VISAC.
Comets and asteroids
July 2010: photometric measurement of (105) Artemis. The rotation curve is not finished. More details here.
June 2010: photometric measurement of (129) Antigone. This asteroid is well-known, and helped me to learn the technique. More details here.
June 2010: astrometric measurements of asteroids (850), (20024), (20085) over 3 successive nights. 22 positions sent to Minor Planet Center. I have received the observatory code C26 (Levendaal observatory, Leiden)!
The daily oscillation of the (alpha, delta) position due to parallax is clearly visible in the measurements. It can be extracted by least square fitting with a 2nd order polynomial, and taking the fit residuals. This allows to get an estimate of the distance to Earth.
May 2010: pictures of comets 81P, C/2008 FK75. I detected stars with magnitude V > 19.5.
May 2010: pictures of M51, NGC4565, NGC 5394.
May 2010: three pictures of M101 showing the effects of approximately equilibrated mount due to CCD cables pulling on the telescope tube.
March-April 2010 : first pictures taken with the Takahashi EM200 mount
The Orion nebula M42 taken with a Canon EOS 450D: see here
Comets and asteroids
October 2009: comet C/2008 P1 (Garradd).
Oct 2009 : most images are taken with a CCD camera, but I also made a few attempts with a Canon EOS 450D.
Sept-Oct 2009 : the old version of the telescope mount was still used.
Due to rather poor mechanical stability, a lot of short exposures were combined.
The tube was well baffled (no parasitic light) and a flat correction was used.
Aug-Sept 2009 : the first series of pictures taken with the Audine. The telescope tube was not properly baffled, which resulted in some significant extra noise (shot noise due to parasitic light). The pictures were also not flat corrected.
17 August 2009 : very first CCD images.
CCD camera Audine
Presentation: main characteristics of the CCD camera based on KAF0402-ME sensor
Audine with Ethernaude
Audine with LPT1 link
Canon EOS 450D digital camera
Gain and read-out noise analysis: both are varying with the sensitivity in ISO. The best sensitivity for astrophotography is the largest (1600 ISO). The improvement wrt 800 ISO is not so high due to saturation effects.
Old Newton telescope
Quality of telescope optics: Foucault tests, star test, and phase contrast have been performed on the primary mirror, surface accuracy is lambda/19.
Fringe correction in flat frames
All my flat frames are polluted with fringes. This link illustrates the approach I choosed to correct this unwanted effect.
Some approximations made by IRIS... (discussion 13 May 2010)
These links summarize a discussion in the AUDE group, about some strange behaviors of IRIS with two basic image processing functions:
- Sigma clipping (French)
- Median value. I also give a comparison of median calculations between IRIS and exact formulae (French)
Time synchronisation of a Windows XP computer
For time synchronisation through Internet I use the Meinberg freeware. Its performance should be better than with other freewares as Dimension 4, since it uses the full protocol NTP. However I had to fix a problem with Windows.