PHEMU 2015Europe eclipse Amalthea

COLLOQUIUM Astrometry of the solar system after the Gaia project - PARIS Bernard Christophe, Olivier Dechambre

Ephemeris

• 2E5, Europe eclipse Amalthea,2015-04-08, 20h16mn33s UTC (Start).• Duration: 2,7 minutes (30 images)• Amalthea magnitude: 14.5• Distance between satellites: 37 arc/second• Jupiter elevation : 58 °• Ideal conditions !

COLLOQUIUM Astrometry of the solar system after the Gaia project - PARIS Bernard Christophe, Olivier Dechambre

Sky field map

COLLOQUIUM Astrometry of the solar system after the Gaia project - PARIS Bernard Christophe, Olivier Dechambre

Saint-Sulpice Observatory - IAU947

• Newton Telescope• Diameter: 60 cm• Focal length: 336 cm• ….

COLLOQUIUM Astrometry of the solar system after the Gaia project - PARIS Bernard Christophe, Olivier Dechambre

« Methane strategy »

• Jupiter absorption on Methane CH4

COLLOQUIUM Astrometry of the solar system after the Gaia project - PARIS Bernard Christophe, Olivier Dechambre

Methane Filter

• 890nm Bandpass Interference Filter: 10nm FWHM

• Edmund Optics « Techspec » series.

COLLOQUIUM Astrometry of the solar system after the Gaia project - PARIS Bernard Christophe, Olivier Dechambre

EMCCD Raptor Camera

• EMCCD Camera Raptor Photonics• Gain : 50 %.• Recorded on Dell PC laptop(FITS files).• GPS datation (Michel Chevreton Software).

COLLOQUIUM Astrometry of the solar system after the Gaia project - PARIS Bernard Christophe, Olivier Dechambre

First result: Amalthea detected

COLLOQUIUM Astrometry of the solar system after the Gaia project - PARIS Bernard Christophe, Olivier Dechambre

Photometric analysis 1

• The unit images reveal of very faint signal, Amalthea is barely visible.

• The measurements of Amalthea is difficult with:– common software (Prism, Iris, Tangra,…)– different photometry mode (Aperture or PSF fitting)– 360 pictures on pretreated (Dark) and recentered on

Callisto

• The results are not usable ( SNR too low).

COLLOQUIUM Astrometry of the solar system after the Gaia project - PARIS Bernard Christophe, Olivier Dechambre

Processing and Photometry 2

• 360 pictures ( 5 sec)• Dark processing• Realigned using Callisto (Maxim DL)• Sliding average on N pictures• Amalthea photometry (N)• Minimum of eclipse (N)• Timing

Photometry fonction of N

N= 5 ..\..\..\..\..\PHEMU2015\sortie05.xls

N=15..\..\..\..\..\PHEMU2015\sortie15.xls

N=21..\..\..\..\..\PHEMU2015\sortie21.xls

N=25..\..\..\..\..\PHEMU2015\sortie25.xls

N=35..\..\..\..\..\PHEMU2015\sortie35.xls

Amalthea photometry (N)

Amalthea curve light

Rank is first image on an N packet

Minimum de l’eclipse fonction de N

152.5

153

153.5

154

154.5

155

155.5

0 10 20 30 40 50

Série1

Linéaire (Série1)

Timing• The middle of the PHEMU is n°153 image ( N°154 but

Raptor camera started the first image at zero number)

• The datation of the n°153 image is 20150408 201756.8 ( Raptor camera header file displays image beguinning )

• 154.14 => 20h17mn56.8s + 2.5s + 0.14*5s = 20h17mn60s

• The middle of the PHEMU is 2015 04 08 20h18mn00s + or - 3s

Conclusions :• Methane filter reduces the Jupiter diffusion but also

Amalthea's light…• Methane filter: the Galilean moons are still very

bright and can be in close proximity of Amalthea.• Occultation disk ??• The functions of photometric analysis software must

evolve. Example: Sliding average on N pictures.• For the moment, a quite difficult observation for

amateurs !