Horizontal lines after integration

Hi Johan, what exposure time do your subframes have and are the subframes recorded with low gain values. Do not use bias frames with CMOS cameras. Only use darks, flats and dark flats. Adam Block recently uploaded some very informative videos on Youtube.

@minusman Hi, thanks for your answer!

Exposure time for my Flats was 0.080sec (80ms) and 4000 gain.

Exposure time for my DarkFlats was also 0.080sec (80ms) and 4000 gain but now cover placed.

Exposure time for my Bias was 0.001sec (1ms) and 4000 gain and covered.

Exposure time for my Darks was 120sec and 4000 gain same as Lights but cover placed.

I have processed without Bias frames and used then DarkFlats instead but with the same bad result and I noticed that the MasterDarkFlat had also horizontal lines.

I will look for the videos, thanks.

And the light frames?

Thats a lot of gain. You're only getting about 8-9 stops of dynamic range and amplifying all the noise. The sweet spot for the camera is about 1000. At 1000, you get about 12 stops of dynamic range and good read noise reduction.

Do they also watch in the lightframes? And did you dither? I have a problem with stripes too. I've got it well under control by adjusting gain and exposure time until the stripes are only minimally visible in the lights and the rest is dithering. If there are still some strips left in the stack I remove them with the Canon Bandig Script in Pixinsight.

The light frames have an exposure time of 120sec with 4000 gain and no dither

After a close check and zoomed in on a light frame the lines are also visible a little bit but only in the middle of the frame near the globular cluster stars.

The first 10 light frames have no lines but from then on it starts to appear.

I have now to say that I see the lines also a bit in my masterdark but the most in my masterdarkflat or masterbias.

I have tried to capture with lower gain in the past (900 gain and 85sec exposure were the numbers given with the sensoranalyse tool in SharpCap) and total time was about of 2hours but during stacking with

DeepSkyStacker there were only 15 stars visible and the result was a black screen. It was done with my Orion 190mm f/5.3 Mak-Newt Astrograph Telescope on the M66 galaxy.

Posted by: @astrogisjoh

I have tried to capture with lower gain in the past (900 gain and 85sec exposure were the numbers given with the sensoranalyse tool in SharpCap) and total time was about of 2hours but during stacking with

 

85s is pretty short. I have a ZWO 294, 3-5 mins will give you a good SNR for your image and something for DSS to work with.

I does sound like you're getting the lines from dark noise. I guess your camera is cooled so not sure why this noise is showing up over time. The ZWO has annoying rays of dark noise from the side of the sensor. I found so far if I used darks, the colour was killed but Vincent is looking into it. I'm going to keep a closer eye on this to see if I'm getting increasing noise over time too.

It is quite possible that at the beginning of the night the stripes are not visible because the sky background is not yet perfectly dark. Later they will become visible because the background becomes darker. Then only the dithering and possibly increasing the gain again helps.

Yes, that will be the reason of that.

Are you sure that increasing the gain helps too because my gain is already quite high?

Here are some example pictures, taken with my ZWO ASI 294 under similar conditions (sky area, moon phase, light pollution). These with Unity Gain and 60s exposure time.

And this with higher gain and same exposure time.

The pictures were stretched strongly to make it clear.

The finished stacks then look like this.

The left image I have to help with the banding script in PixInsight (in Photoshop there is also a banding action). In the right image the gain increase
...make the sky background come out. This in turn masks the stripes.
In your case with the globular clusters it is probably not possible to increase the gain without burning out everything.
Only aggressive dithering will help.

@minusman Thanks for bother showing this, it will be very useful to me the next captures!

Check if you're using FAT32 as filesystem for your working directory. If that's the case, that might also be your problem. You need to use (when it's a USB drive) exFat. I assume if it's on your normal system, that is using a modern filesystem.

And indeed, you need to optimize on a proper gain.

@vincent-mod Thanks for the support and I use a SSD drive with NTFS as filesystem for my working directory.

Ok, so then it's likely the gain as mentioned. 🙂 Good, that can be easily improved upon.