I took advantage of a clear evening to do a little more driveway astrophotography. The target was comet 144P Kushida. The comet is nearly at the Zenith in the evening, very conveniently placed with ample time to take more than a few frames.
The setup was fairly typical for me, the Canon 20Da and the TV-76 shooting for over 40 minutes (10 frames at 4 min each). The frames were calibrated and stacked in Images Plus and post proccessed with Photoshop and FITS Liberator. I followed Jerry Lodgriss’ instructions for preserving and enhancing the star colors with pleasing results. I suspect I will be using this technique more in the future and star colors are something that has always frustrated me.
Since I have a CCD camera co-boresighted with the TV-76mm refractor I was able to use the CCD to take frames simultaneously. This arrangement is convenient as I can use the CCD for finding and framing the target, the field of view is very similar between the two cameras. I spent time early in the evening to carefully align the CCD to match the view in the refractor. There is also a small 10cm SCT in the setup for use as a autoguider scope, but I have not been using this lately. I suspect I will try some longer exposures of C/2007 N3 Lulin in a few days and will need the guider.
The comet itself was fairly straightforward, a round coma with no real tail, a slight off centered shape to the coma. The cyanogen green comes through nicely, very apparent when processing the color planes separately. It is moving fairly slowly, for the DSLR photo I aligned on the stars and only had slight issues with the comet trailing. For the CCD image I aligned the images on the comet, showing some trailing in the stars.
The CCD frames do not show any sign of a tail or other structure either. This is not surprising as 144P Kushida is usually a fairly dim comet that is bright only due to material from an outburst a couple months ago. It is not a highly active comet with jets, tail and all of the other features that can make comet photography so interesting.
C/2006 P1 McNaught is currently passing close to the Sun. At a mere 18 million miles (0.197 AU) from the Sun the intense solar radiation is causing the comet to boil and vent violently. The resulting cloud of gas and dust is reflecting enough sunlight to brighten the comet dramatically. Estimates are placing the comet at mag. -5 or even mag. -6. This is much brighter than even Venus! Some observers are reporting easy unaided eye visibility, but in the sky over Tucson a lot of dust and aerosols in the air are causing a great deal of glare around the Sun. Thus binoculars or a telescope is required to see the comet.
The challenge is that Comet McNaught is just five degrees east of the Sun. Observing so close to the Sun presents distinct dangers, I do not want to fry my retina! So I carefully positioned my TV-76 on the alt-az mount so that the Sun was just behind the edge of my carport. Thus I could pan around and locate the comet with little fear of direct sunlight down the tube. A few frames with the Canon 20Da turned out OK but not great, those dust and aerosols in the sky and the resulting glare is reducing the signal to noise in the images. The photo to the right is a stack of three images in an attempt to improve the signal to noise, then greatly cropped in and levels adjusted in Photoshop.
The view was better in the eyepiece. A sharp point of the coma with a fan shaped tail. This really looks like a classic comet, I had not expected such a good tail in the bright sunlit sky. This is my first daytime comet, and since the opportunity may not come again anytime soon, this may be my only chance to see one, truly a once in a lifetime event!