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Best and Worst subexposures of Altair after PEC training, 



Best and Worst subexposures of Altair after PEC training


After doing unguided imaging with my G11/G2 for the past year I decided to upgrade to the latest firmware and try it with PEC. I chose the star Altair because it is bright and near the celestial equator. I did the PEC training manually using my Canon 60D LiveView in movie crop mode to achieve maximum magnification. I did not actually record a movie clip because that causes the crosshairs to disappear.

I used the LiveView grid#2 pattern as my crosshairs. This pattern has 3 horizontal lines and 5 vertical ones, so there is a crosshair at the exact center. It is also good for exactly centering your alignment stars. I set the "Auto Power Off" to 4 minutes so the LiveView would not go dead in the middle of PEC training. In the movie crop mode Altair appeared to have a diameter of about 15 pixels and moved up and down about 10 pixels.

The PEC training was performed at only 800mm FL so it was difficult to accurately see when the star began to move from the center on the 3" LCD. Next time I will put in one or two extenders to up the FL to 2400 or 4800mm so I can accurately follow the moving star. Eventually I will get an autoguider to do the PEC training, but part of the idea is to avoid bringing out more equipment.

In the 240 second subexposures (ISO 400 at 56 degrees F) Altair's diameter swells to 90 pixels. The 2 best subexposures show only slight elongation of the faint stars, the 2 worst subexposures seem to indicate some kind of disturbance. It may have been caused by the intervalometer cord dragging or something loose, this has happened before. Over time I will be paying attention to the percentage of bad subs and working to bring them down.

Before I used PEC I needed to image near the celestial pole to reduce star trailing on 2-4 minute subexposures. Now I hope be able to image at any declination at 800mm.

I images shown are out-of-camera jpegs displayed in ArcSoft at full resolution. The scale is 1.088 arcsec/pixel.



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Best and Worst subexposures of Altair after PEC training,