Sunday, August 12, 2012

NGC-7331 Past and Present

Over the last two nights, I had a chance to image the galaxy NGC-7331 in Pegasus.  After preliminary processing of the data, I looked back over my imaging notebook and found that this was one my very early imaging targets.  I was interested to compare the two attempts.

The first was created from a series of approximately 20 unguided 1 minute color exposures taken back in October 2008 when I first started astrophotography.  Exposures were taken with an SPC-9000 webcam, which I had modified for long exposure, through a Celestron 9.25" SCT.  Image scale is 0.46 arcsec/px prior to de-Bayering.  Field of view is very small - this is an uncropped image!

The second was created from a series of approximately 20 guided 10 minute exposures through RBG filters.  Exposures were taken with a QSI-540ws CCD camera through a TMB-130SS refractor.  Image scale is 1.46 arcsec/px.

In looking back,  I am impressed what was possible with that little webcam.

In the same image frame as NGC-7331, I also captured the violently colliding group of galaxies called Stephan's Quintet.  The inset on the top left shows this group at the same image scale.  On the bottom left is an old image of the same group that I took in December of 2008, soon after replacing my wecam with a Canon DSLR.

Since the second night was the peak of the Perseid Meteor Shower, I looked through the frames to see if I had caught any meteors.  What I at first thought were tiny, short meteors, I soon decided were probably satellites:

This image is a superposition of three different 10 min exposures.  On the first night, at 2012.08.11 00h20 CDT,  there was a uniform solid trace, labelled above. A second dimmer trace occurred along a parallel path a few hours later at 2012.08.11 02h50 CDT.   I don't know if these are the same satellite.

Of more interest was the pair of traces in the frame from 2012.08.11 02h50 CDT  (one trace is below and to the left of NGC-7331 and the other to the left of Stephan's Quintet.)   Just 24h later, in the 2012.08.12 02h50 CDT frame, another identical pair of traces appeared (one is to the left of NGC-7331 the other is above and to the right.)  The similarities and timing seem too coincidental not to be the same satellite.  Since the traces are bright in the center and dim on the ends,  I assume this satellite is rotating uniformly.

Update 2012.08.16 - No success in identifying any satellites in this field of view within an hour of the observation in

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