Crescent Moon

Golden Sunset

The Moon is about two and a half days past New Moon and it was looking good in tonight’s golden Sydney sunset.

Whilst the four months of mostly cloud and rain has been forecast to continue into our southern winter, we have enjoyed some surprisingly pleasant sunshine over the past few days and I’ve managed three nights outside with telescope. I had to brush the spiders off!

However, the news is not good, unfortunately. For three nights I’ve been taking images of a galaxy called the Sombrero and also a bright supernova. Every single image has been wrecked by horizontal streaks right across the image.

They look a bit like inverted Starlink pollution.

I’ve spent countless hours trying to work out whether it’s the telescope optics, the camera hardware, the live stacking software or even the guiding software. Until I figure that out, I guess there will be no more images.

Here’s a clickable four minute exposure, showing the Sombrero Galaxy, with horizontal interference streaks:

M104 Sombrero Galaxy With horizontal interference lines

The black streaks always coincide with bright stars. If I over-expose the image, even more lines become apparent.

My images of the supernova in NGC 4647 are even worse….

What causes dark interference lines and how can I get rid of them? Help! Any ideas welcome!


EDIT. 6th May 2022. The Solution:

Telescope: Meade LX-90 Schmidt-cassegrain on Skywatcher EQ6-R mount.
Camera: ZWO ASI 071 MC
Software: ASCOM, EQMOD, SharpCap, PHD and Cartes du Ciel.

Cosmic Focus Observatory

34° South

Above us only sky….

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Images © Roger Powell

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ABOVE US ONLY SKY : amateur astronomy in australia


  1. That has to be very disappointing and puzzling. I wish I had some suggestions on what to do for a fix. You probably tried all the basics I would have like turning off, unplug-replug, adjust this and that setting.

    I attempted to ‘fix’ an E1 error on my wife’s sewing machine after it jammed. I succeeded in adding an E2 error to the list. I will stand back and watch as you work this out. 🙂

    Liked by 1 person

  2. 1) nice photo of the sunset and moon.

    2) the Sombrero galaxy image was the first image I remember downloading from the NASA site (a high-resolution version that at that time (2003) was a whopping 211MB. For the longest time, a print of it was on my wall at work.

    3) can’t help with the streaks other than to say this: when I used to print at home, occasionally I would be plagued by similar streaks on some prints. Investigation of the issue came down to one of two culprits: alignment of the printer heads and conflicts between the printer and printer driver of the application I was using to print. I realize neither applies to your issue . . . except (maybe) that you’re stacking images and it could be an artifact of the stacking. I don’t suppose you can look at individual photos to see if the lines are present prior to stacking? Also, maybe try a different stacking program (Photoshop can stack images) to eliminate that possibility. Perhaps stacking fewer images might also help confirm or eliminate the stacking software.

    3a) the fact it coincides with bright stars seems to point to sensor or camera issue although that sounds like a stretch. But then, I don’t know a whole lot about how your equipment works. Have you tried enlarging the photo to see if the lines are completely dark or if there are details within the lines? The presence of details might indicate a stacking issue.

    4) now I’m really going out on a limb and talking out of my posterior… could it be spectral lines due to the color temperature differential between source and sensor:

    5) something (almost) similar I came across:

    6) this is probably not useful, but:

    Nota bene: I’m not trying to insult you by implying you wouldn’t have thought of these things yourself. Just motivated by your call for help even if I’m just posing simplistic and completely useless scenarios.

    Liked by 1 person

    1. For some reason WordPress stuck your comment in the “Approval Pending” page. Probably because of the three links. 😵

      1) Thanks.

      2) Yes. the Sombrero is a mesmerisingly beautiful galaxy. I’m going to try it again soon, I hope.

      3) I was able to deduce that the interference bands did not appear in each original frame. So I knew it was not the camera at fault but somewhere in the pre-process procedures.

      5) The link refers to images taken with a DSLR a totally different procedure. Interesting though. . .

      6) I sometimes get these short diffraction lines through stars when using my refracting telescope, so that’s interesting. I don’t get them in the schmidt-cassegrain telescope I’m currently using.

      NB I’m not easily offended (unless someone says something which is actually offensive. . . . ) so I appreciate your research and comments. Very much.

      FYI the camera is a low noise CMOS astro camera.

      No buttons or knobs to twiddle. All controls and adjustments conducted from the software in the laptop. Pre-processing has the following main steps:
      1. laptop receives sub-frame from camera and software saves it as a light frame.
      2. software merges light frame with dark frames (taken at start of session) and saves.
      3. software merges light frame with flat frames (taken at start of session) and saves.
      4. software aligns stars in sub-frame with those already in the stack.
      5. Software adds sub-frame to the stack.
      6. Updated stack appears on monitor.
      7. Waits for next sub-frame to download from camera. Go to 1.

      The Solution

      I went to the software forum and the admin/author has now provided me with the solution. The problem was that three sessions ago a software feature called “Horizontal banding suppression” was activated. Don’t ask me how, I don’t normally play with controls I have not read up on. Must have been Dolly that did it.

      Fortunately for the last target I had saved each light frame and was able to use the software (with banding suppression set to zero) to successfully process that image, which shows a recent bright supernova. It will be my next post.

      After that, it will be back to the Sombrero.

      Liked by 1 person

  3. Great photo of the Sunset and Moon. Glad you found the solution to the horizontal lines. My first thought was, wow you are incredibly unlikely if the skylink satellites keep passing over your targets at just the wrong time.

    Liked by 1 person

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