Astronomical Chronicle For August 2012 Is Up, Plans Pending For The Perseids Tonight At Darling HillSaturday, August 11th, 2012
Greetings fellow astrophiles!
1. Perseid Opening – As of 11:00 a.m., conditions look right for opening Darling Hill for the Perseid Meteor Shower. Please keep track of this website around 5:00 p.m. today for the final decision and possible decision about opening tomorrow night instead.
2. The latest edition of the SAS newsletter is available for download below:
This edition features a lengthy article by the SAS’s Rick Kellogg on an Electronic Polar Alignment Scope, available for download at 2012_August_R_Kellogg_Electronic_Polar_Alignment_Scope.pdf. Rick’s summary is below:
A traditional polar scope can be used to align an equatorial mount in a few minutes. However, the alignment achieved is typically not that accurate due to misalignment of the polar scope axis with the mount axis, or the polar scope reticle not being centered. I typically can only get to within 0.1 degree of the celestial pole with my Losmandy polar scope.
Extending the ideal of using a polar scope for aligning to an electronic scope – I use an SBIG STV with a 75 mm lens as an electronic finder. This combination provides a 3.7 by 2.7 degree field of view (FOV).
Setting the DEC to 90 degrees, Polaris and UMI lambda are in the field of view – regardless of the RA setting. By taking 2 pictures with different RA (differing by 4-6 hours or 60-90 degrees),
1) the pixel location of the mount’s RA axis can be determined, and
2) the pixel location of the Celestial pole can be determined (knowing the current epoch
coordinates of Polaris and UMI Lambda).
Then the offset from the mount’s RA axis to the Celestial pole is added to the location of Polaris (or UMI Lambda) to act as a target to move the scope via azimuth or altitude controls.
I have automated the process using the SBIG utility that comes with the STV (STV Remote), and a MATLAB script that I wrote to make the computations.
The typical polar alignment process can be easily completed in 15 minutes.