David's Astronomy Pages Notes - CCD Session 26 (2002-09-20)

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Magnitude reach - GSC 1075:909 Area

Images of an area around GSC 1075:909 (less than 2 deg from Altair), where taken at  2 sec, 5 sec, 10 sec and 30 sec exposure.  Magnitude limit increased from +13.0 for 2 sec exposure to +15.0 for the 30 sec exposure.

2 sec exposure, mag limit +13.0

2002-09-20  22:06h UT CCD Image, 2 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#26003)

10 sec exposure, mag limit +14.5

2002-09-20  22:07h UT CCD Image, 10 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#26005)

30 sec exposure, mag limit +15.0

2002-09-20  22:08h UT CCD Image, 30 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#26006)

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Identification of Uranian Moons (Oberon, Titania & ? Umbriel)

Based on earlier analysis of CCD Images of Uranus taken on 2002-09-01 and 2002-09-13 it was suspected that new CCD Images of Uranus taken on 2002-09-20 showed the two uranian moon Oberon and Titania.  This was confirmed using the "UranianSats" Visual Ephemeris program by Dennis W. Tracey (http://www.winnipeg.rasc.ca/ftp/dtracy/ ).

Uranus, Oberon and Titania

The empheris program predicted that Umbriel would lie at sufficient distance from Uranus that it might just be visible at the edge of the light glare from Uranus (Mag +5.8)

Umbriel ?

2002-09-20  22:39: to 22:42h UT 5 CCD Images, 30 sec exposure (2x2 binning)

Uranus, Oberon, Titania & ? Umbriel

2002-09-20  22:39: to 22:42h UT CCD Image, 5 x 30 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#26018-22) Umbriel is possibly just visible at the top of Uranus's light glare

Catalog magnitudes of offset stars

2002-09-20  22:39: to 22:42h UT CCD Image, 5 x 30 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#26018-22)

See also : 
Uranian moon identification in images taken on 2002-09-01  
Uranian moon identification in images taken on 2002-09-13

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Double-Double in Lyra

Images of Double-Double in Lyra were examined (1x1 binning/0.5s exposure and 2x2 binning/5s exposure). As found previously (Notes from CCD Session 2, 2001-09-25) it was very difficult to split the two 4.5 magnitude 'stars' into their component double, due to their brightness and very close separation. 

Double-Double (Lyra)

2002-09-20  23:23h UT CCD Image, 2 x 5 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#26039-40)

Repeating the FWHM method the two 'stars' can be identified as non-single point source objects  as they have anomalously large FWHM values of 7-8.5 arc secs, compared to expected FWHM of 3.4-4.5 for a single point source object.  A FWHM diagram of  Image #26039 is shown below

It was noted that whilst individual Images #26039 and #26040 obtained astrometric solutions with 21 and 19 stars respectively using CCDSoft's Insert WCS/Auto Astrometry function, the averaged Image with higher signal to noise ratio achieved an astrometric solution with 23 stars.

An annotaed image showing the Double-Double stars together with offset stars (with their catalog magnitudes) is shown below

Double-Double  Catalog magnitudes of offset stars

2002-09-20  23:23h UT CCD Image, 2 x 5 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#26039-40)

The Double-Double was in fact the first astronomical object I ever imaged with my CCD Camera on almost one year ago (First Images)

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M92 Globular Cluster

Images of M92 were processed 

M92 Globular Cluster

4 x 30 sec, narrow histogram range  (core of cluster washed out)

4 x 30 sec, wide histogram range  (stars in core visible, but dimmer stars no longer visible)

2002-09-20  23:44 to 23:46h UT CCD Image, 4 x 30 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#26059-6)

4 x 30 sec, slightly enhanced by mid range brighten (shows both stars in core and dimmer stars)

2002-09-20  23:44 to 23:46h UT CCD Image, 4 x 30 sec exposure (2x2 binning) 11.4 x 7.6 arc min  (#26059-6)

2 x 2 min, enhanced by mid range brighten, slight unsharp masking

2002-09-20  23:47 to 23:51h UT CCD Image, 2 x 2 min exposure (1x1 binning, then x0.5 ) 11.4 x 7.6 arc min  (#26064-65)

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