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Horizontal lines after integration


(@astrogisjoh)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 6
Topic starter  

Hello,

I am a recent user of APP and I am very happy with this program!

There is only one problem a struggle with as you can see in the tittle : horizontal lines in my intergration result (stretched)

I use an ALTAIR Hypercam 294C Pro Tec camera with a Narrowband filter HUTECH IDAS NB1

I have tried different settings in APP on different pictures but with no change in the result.

I can see also horizontal lines in my MasterBias or MasterDarkFlat also but I don't know if this is normal and if this is related with my problem (beginner also)

The intergration of my Lights are done with Darks, Flats, Bias and as a test with Darkflats also but with the same problems.

This is a picture of my problem :

M13 2 St Stripes JPEG

Is there someone who can help me with this problem?

Kind regards,

Johan

 


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(@minusman)
Red Giant Customer
Joined: 5 years ago
Posts: 199
 

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.


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(@astrogisjoh)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 6
Topic starter  

@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.


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(@minusman)
Red Giant Customer
Joined: 5 years ago
Posts: 199
 

And the light frames?


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(@astrogee)
Red Giant Customer
Joined: 4 years ago
Posts: 128
 

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.


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(@minusman)
Red Giant Customer
Joined: 5 years ago
Posts: 199
 

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.


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(@astrogisjoh)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 6
Topic starter  

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.

 

 


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(@astrogee)
Red Giant Customer
Joined: 4 years ago
Posts: 128
 
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.


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(@minusman)
Red Giant Customer
Joined: 5 years ago
Posts: 199
 

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.


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(@astrogisjoh)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 6
Topic starter  

Yes, that will be the reason of that.

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


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(@minusman)
Red Giant Customer
Joined: 5 years ago
Posts: 199
 

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.

Bildschirmfoto von 2020 05 27 20 10 14

And this with higher gain and same exposure time.

Bildschirmfoto von 2020 05 27 20 10 33

The pictures were stretched strongly to make it clear.

The finished stacks then look like this.

Bildschirmfoto von 2020 05 27 20 10 23
Bildschirmfoto von 2020 05 27 20 10 46

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.

This post was modified 2 years ago by minusman

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(@astrogisjoh)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 6
Topic starter  

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


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

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.


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(@astrogisjoh)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 6
Topic starter  

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


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4736
 

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


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