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Captured (9) 300-sec unguided subframes of M1 on Sep 19 (3 R, 3 G, and 3 B) starting 07:04:11 UTC using SGP. Equipment: SkyWatcher Espirt 120ED refractor with field flattener, ZWO ASI294MM CMOS camera, ZWO filter wheel and 10Micron GM1000HPS mount. Calibrated those 9 subs using 300-sec dark and calibrated flat frames. Continued with post processing and M1 is looking like it normally does - no problem there. I did notice some faint nebulosity around HD37013 and observed a red streak right through the center of that star (see image). Inspected the 3 R subframes and only sub frame #1 and sub frame #2 showed a streak anomaly. Sub frame #3 looked normal. HD37013 is the brightest star in the field and shows some east to west elongation due to polar alignment error. What is the red streak ? HD37013_20x15.png |
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| If it only showed in 2 out of 3, maybe a bug or something on your lens? I suppose it could still be a smudge or hair on your optics somewhere if a dither maybe moved it enough. |
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I figured out what was causing the red streak problem. I acquired the Red frames first and the target was just over 30° altitude. There is a thin pole in that field of view that was causing the red diffraction spike. By the time the 3rd Red frame was acquired, the target had risen just enough to be outside the thin pole field of view. I had set my horizon limit to 30 degrees and it needs to be raised to 32° to avoid future problems. Thank Brian for your suggestions. |
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Rod Hughes: Good catch! |
