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27 June 2013

Sunspot 1777: Webcam Prime Focus at f/8

Since I have moved to this new place after graduation I haven't been using my webcam for prime imaging. However, because of this attempt with my new telescope I realized a few problems (some was the same as previous) and it should be addressed as soon as possible. 

  1. [similar problem with my 3" Newtonian] The CMOS sensor is too small to capture the focal spot of the 4.5" reflector so the image appears highly magnified and thus prone to fast image drift causing motion artifacts to photographs. Immediate consequence of using this webcam shows the mount for this telescope system unsuitable - it shouldn't be an alt-azi mount.
  2. Unlike the previous solar filtering technique (the previous method was much unsafe and the glass filters are prone to overheating), the images were taken with a ND glass filter located on a mask that was fit to my telescope aperture. It has a diameter much smaller than my scope's primary mirror and hence limit the effective aperture size and hence angular resolution. 
  3. Ahh. the plague of dusts finally comes. It appears as streaks of disk shaped blurness in fixed location of the sensor. Luckily, it is easily detected (the large ones) and after taking all the photos, I cleaned it up with a few gentle puffs from my blower. White field test shows much reduced "drifters" so it should be cleaned for now.

So, out of 33 photographs, I selected the best in sharpness (least atmospheric disturbance) and processed it with Photoshop for detail enhancement [picture above]. The sunspot was obviously my target but with its angular size, it was quite difficult to pin down with an alt-azi mount. Anyway, I cannot tell if the speckles on the surface comes from noise or they are actual surface granulation of the sun but good thing was that penumbra of 1777 can be clearly seen. My last attempt of solar imaging was difficult to distinguish the shades from the umbra but then again, webcam prime imaging wasn't possible before without proper filtering technique.

So we have this magnified image but it failed resolve details of the penumbral filaments either due to the limited field of view coupled with flimsy mount or my telescope (actual) aperture cannot provide me enough angular resolution. I'll try with a larger sunspot next time. 

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