Resolved Newly appearing Image artifact

Hi, I have been using my AC4040 regularly now, and the last two nights an artifact has appeared in all light frame images that wasn't there before. I attach the unmodified camera output of M51 from June 18, no artifact, and M101 June 20, with the artifact. I also see the artifact in an equivalent June 19 image of a different object, and do not see it in any images before June 19. I also attach a dark frame from this past evening, and note that it does not show this artifact. To show how significant it is in a processed image, I also attach a jpg of M101 made from integrating several of the M101 raw fits files to help direct you to the artifact. Nothing has changed in my system to explain this.
Thanks for thoughts on it.

Mark

 

Hi Colin, I’ll try that and report. Thanks.

 

Here is a 90sec Bin1 Dark high read-out and 90sec Bin1 Light frame high read-out. I did these in the observatory, which has some light intrusion during the daytime, so I used the Ha filter to keep from oversaturating it. Given the stray light I couldn't do a proper flat panel image so it has some random light patterns in it.

 

Using the M101 fits image from the initial posting, an "image link" in the Sky X seems to indicate the artifact is optical in nature.
The spike seems to originate from the mag 8 star.
Thoughts?

_..--
Tim

 

I've certainly seen out of field stars run a line similar to that over an image. However, this has appeared on two different targets and the stars outside it on both didn't appear to me to be similarly situated enough to cause it to be at the same spot. Coincidence is a *****! I'll determine this definitively tonight by rotating the camera 45 degrees and keeping the target the same. I hope that you're both right about it, although if you are, that will mean that I'll have to be a bit more careful than in the past. With my prior CCDs, it didn't happen unless something fairly bright was pretty close. I guess in part a reflection (no pun intended) of the greater sensitivity of this chip. I also agree that it doesn't make much sense that nothing would show up in the dark frame or in the goofy dome light frame I took today.

Thanks for looking at it. I find recently that anytime I see something a bit different, I default to wondering if it is a CMOS issue. I like the camera and its sensitivity and download speed, so I need to move on from my prior CCD world view .

 

Could well be. At Doug’s suggestion at AIC I’m starting to dither a significant amount so my frame may have shifted that direction more than I thought. I’ll solve and link in TheSkyX a few different sub exposures and see if that star is right on the edge. I’m more convinced that you’re right which makes it even more of a coincidence that the night before on a completely different target I had the same issue in almost exactly the same spot. Things like that happen.

[Edit, I've now matched the images in TheSkyX and it does seem like that star is the one causing the problem. I think that the camera's enhanced sensitivity is going to require more attention to off-field stars. Recently I've been running unguided, so I haven't paid attention to this like I would have (I might have used that star as a guide star in fact). I'm going to rotate and frame the image differently for more data collection. Hopefully registering the old data with the new will allow rejection of the intrusion.]

 

Thanks Colin, I just installed and will test soon.
Hope all is well,
Mark