Back
Audine CCD camera with Newton telescope 165/1145



17 April 2010

NGC 3718 in Ursa Major
Composition of 40 x 1 min exposures, offset, dark and flat corrected with IRIS v5.57, sigma clipping addition with personal software.






14 April 2010
NGC 3344 in Leo Minor
Composition of 63 x 1 min exposures, offset, dark and flat corrected with IRIS v5.57, sigma clipping addition with personal software.

Thanks to the Takahashi mount, the tracking was very good. Almost all pictures have perfectly round stars. The read-out noise was calculated from the difference between 2 dark frames = 6.30 ADU rms. The total noise in a single raw image (after substraction from an averaged dark frame to remove the hot spots) is 14.6 ADU rms, a value that includes both photon and read-out noises. Photon noise was calculated with the quadratic difference : 13.2 ADU rms. The photon noise is clearly dominating ! I think I am approaching the limits of my setup (in terms of mechanical stability) and my observation site (light pollution).



12 April 2010

NGC 3184 in Ursa Major
Composition of 80 x 1 min exposures, offset, dark and flat corrected with IRIS v5.57, sigma clipping addition with personal software.

This is the first time I experiment such long exposures. The stars are not perfectly circular, due to an unperfect mount equilibrium with respect to the delta axis.



10 April 2010

M63 in Canes Venatici
Composition of 35 x 30 sec exposures, offset, dark and flat corrected with IRIS v5.57, sigma clipping addition with personal software. The flat correction was not perfect and the sky background has been corrected.

The picture could have been exposed for a longer time (but the night was ending and day light coming back...)



 M13 in Herculus
Composition of 10 x 30 sec exposures, offset, dark and flat corrected with IRIS v5.57, sigma clipping addition with personal software.

This picture should be compared with another picture of M13 taken 6 months ago : the improvement in the material (new Takahashi mount) and in my technique are clear. In this new picture the stars are really sharpest and more circular.



08 April 2010

M106 in Ursa Major
Composition of 71 x 20 sec exposures, offset, dark and flat corrected with IRIS v5.57, sigma clipping addition with personal software.

A false color image can be seen here where the faintest parts of the galaxy start to show up.



06 March 2010

The first CCD pictures taken with the Takahashi mount. Both are obtained with 30 sec exposures.

The noise in the sky background of the images has two contributions: (1) CCD read-out noise, (2) shot noise due to sky background. Analysis of the dark and signal frames shows that both contributions have the same magnitude : read-out noise is about 6.4 ADU rms, and background shot noise 6.5 ADU rms. On the individual images I got both contributions for a total of 9.1 ADU rms. To decrease this strong impact of read-out noise next time I will reduce the number of co-added frames. Instead of 60x30 sec I could use 15x2min for instance.

The CCD temperature was about -30 celsius deg, and at such low temperature I also have a few columns that start to have a different response : they are visible on the left as weak vertical lines.
For both pictures, the flat field calibration was not very good, and I had to correct the background sky to make it uniform.


NGC 2903 galaxy in Leo
Composition of 60 x 30 sec exposures, offset, dark and flat corrected with IRIS v5.57
Sigma clipping addition, personal software based on CFITSIO


 M51, well-known galaxy in Canes Venatici
Composition of 60 x 30 sec exposures, same treatment as above
The weak extensions of the smallest galaxy are well visible