David's Astronomy Pages Notes - CCD Session 25 (2002-09-12 / 2002-09-13)

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Notes (S26)

Telescope Collimation

During recent sessions it was suspected that collimation of my LX200 telescope had deteriorated.  The scope was re-collimated and this sharpened up CCD Images significantly, as can be seen in the following  comparison of 2 images of the Mag +7.7 star SAO 125164 (near Altair) taken before and after re-collimation.

Further refinement of the scope's collimation will be tried later.

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Identification of Uranian Moons

It was suspected that CCD Images of Uranus taken on 2002-09-13 showed 2 Uranian moons.

Uranus + 2 suspected moons

2002-09-13  00:13 to 00:15h UT CCD Image, 4 x 30 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#25068-72)

The "UranianSats" Visual Ephemeris program by Dennis W. Tracey (http://www.winnipeg.rasc.ca/ftp/dtracy/ ) was used to identify that the two objects were indeed the uranian moons Oberon and Titania.   They lie at the distance and direction from Uranus that is predicted by the Ephemeris program.

The other main moons Miranda, Arial and Umbriel can not be seen as they lie too close to Uranus to be separated.  Light from Uranus (Mag +5.8) is spreadout to a diameter of 25 arc secs in this image (compared to its true apparent diameter of 3.4 arc secs).  

Uranus, Oberon & Titania

2002-09-13  00:13 to 00:15h UT CCD Image, 4 x 30 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#25068-72)

Oberon has a calibrated magnitude of +14.7 +/-  0.2, estimated using CCDSoft Software on 5 images #25068 to #25072. Titania is too close to Uranus to allow software to estimate its magnitude. A rough estimate suggest that its magnitude lies between +14 and +15.

Catalog magnitudes of offset stars/Calibrated Magnitude of Oberon

2002-09-13  00:13 to 00:15h UT CCD Image, 4 x 30 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#25068-72)

See also : Uranian moon identification in images taken on 2002-09-01

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Master Flats

Master Flat (2x2 binning, leads down) Av. 40 x 0.5 sec light frames (tee-shirt flats)

Master Flat, 1x1 binning, leads down (av 20 x 1.5 sec light frames)

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