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Thread: Arp 199 under rather good seeing conditions -- what a difference

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    Join Date
    Dec 2006

    Arp 199 under rather good seeing conditions -- what a difference

    Tuesday night-Wednesday morning (April 10, 2012 UT) the Clear Sky Chart said it would be clear with lousy seeing. I decided to give it a try anyway. I wanted to catch M95 and its super nova even if the seeing was lousy. My last post of Arp 199 showed what lousy seeing does. When it did finally clear (it was cloudy for a while) Arp 199 was right high enough to image but M95 too far west and low. I did a focus run and found the seeing rather good contrary to predictions. As I expected it to cloud up any moment (fog has rolled in nearly every clear night this year) I decided to give Arp 199 another go. Fog did roll in during one blue frame making it useless but rolled back out again. I then replaced that frame after the luminance images were taken. Moon rose during the second blue frame but it was usable.

    I'm processing it a year out of order to illustrate the difference between good and bad seeing. Also I moved the field over to better frame NGC 5557 which was cut off in the previous version. Its outer halo is larger than I expected. I cut some of that off even after moving a couple minutes east.

    Original post:

    Due to the reframing a couple objects on the previous annotated image moved out of the field and a galaxy cluster moved into it. The position of the BCG is listed as the cluster's center but with a slightly different red shift. The cluster's redshift was determined photographically while the BCG was apparently done spectroscopically which is more accurate. I put a "P" after the photographically determined distance.

    There's an asteroid in the image, (26383) 1999 MA2, that gives away the order of my frames as at magnitude 17.1 the color frames were strong enough to color the background sky. The lost blue frame shows up as a gap between the end of the green frames and first blue frame. The added blue frame, mostly after moonrise, follows the luminance trail.

    Sloan image:

    Arp's image:

    14" LX200R @ f/10, L=5x10 RGB=2x10x3, STL-11000XM, Paramount ME

    Attached Images Attached Images

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