Observing with Street Lights

Observing with Street Lights
Dark sky sites not always necessary to see the Milky Way (This image was taken ouside of a B&B in Julian, CA)

Thursday, January 15, 2015

Lick Observatory and photographing geostationary satellites

Yesterday I removed the ham satellite antenna from the mount and put the hydrogen alpha scope  back on.  I had high hopes of seeing the sun, but life events interfered.  It seems the gardeners wanted to use the parking lot for a staging area for raking and blowing and such.  So, after hours of delay, I decided to wait for night and make another attempt at catching some geostationary satellites.  While waiting I got an email from a long time OC Astronomer.  Bob sent a fantastic web list of photos of old and abandoned astronomical observatories.  Thank you Bob.  See the web page post below.  One of the abandoned sites is in the White Mountains in central California.  Pretty neat location.

 Hopefully the Lick Observatory can survive a little longer.  Too much light pollution.

http://weburbanist.com/2012/07/08/watch-out-10-eerie-abandoned-observatories/

Finally back to the hunt for geostationary satellites.  And finally success.  See the photo below.  I redid my calculations about where to point the camera and believe that my previous attempt wasn't aimed correctly.  I had the 5 degree below the celestial equator, but my azimuth calculation seemed to be off.  This time I estimated that I could use a star, Alnitak, the leftmost star in Orion's Belt, as a reference star.  It's declination is about - 2 degrees.  Also I estimated that at about
9:34 PM the star would be at the correct azimuth corresponding to the location of satellites at about 105 degrees west longitude.  I wanted to pick a longitude that was bound to have lots of satellites overhead, so 105-120 degrees seemed good.  We are at near 117 degrees west longitude.

So my plan was to wait for
9:34, set Alnitak into the top left of the photo view and leave my camera at the location throughout the observation period.  That way with a focal length of about 150 mm I should have a 6 by 9 degree image that should contain some satellites.
One misstep along the way almost sank the whole experiment.  As the
9:34 time approached, I found I couldn't see any of the stars in Orion.  They were visible to make eye but nothing on the camera.  I must of checked several times to be sure the lens cap was off, but yes it was off.  I finally in desperation took a six second exposure.  The photo told me right away what was wrong.  The lens was out of focus and the stars were giant blobs of dim light.  I used Live View and camera focus enlargement and dialed into a star and completed the focus just in time to set position on Alnitak.

I took several images of exposures of 30, 60, and 120 seconds, separated by 10-15 minutes.  Another OCA imaging old timer, Dave told me that he was successful with 30 second exposures in dark skies, so I used a range of exposures just to be sure.  I spaced the images out in time to try to find the optimum sun illumination angle.  Previously, I had guess that maximum reflection from the satellites would be about
midnight when the satellites reflected light was lined up directly with sun.

Finally after a half dozen exposures, I could see some point light sources in the camera image.  It wasn't until I downloaded the images and did some computer enhancement that the stationary sources appeared.  The point sources were spread over several pixels so they were not the result of hot pixel camera defects.

Success it seems has arrived.  We should celebrate.

Well, how about I celebrate and leave some homework for the interested observer.  Given the image, review Wikipedia longitude locations of satellites and see if you can identify the names of the dots in the image.  Can you find a position patter that agrees with the 6 suspected satellites?  Does the data fit better if another not visible satellite is added to the image?  Yes, the satellites really do move around a little bit, but mostly lie in a plane. My camera image was magnified and cropped so I think it's angular size is about 2 by 3 degrees.  This seems quite small to contain as many suspected satellites.  What else might be going on?


No comments:

Post a Comment