Horizontal lines/banding on my astrophotography images

[AstroNebulee]

Hi

I have recently altered my az gti mount to operate in eq mode.  I'm using a sw 72 ed ds pro with field flattener and my canon 600d.  I have been having so much trouble with horizontal banding in my astrophotography images.  They are 180secs long so not a huge long exposure and at 800 iso.  I use an all wired connection from my laptop to the az gti mountwith an lynx astro cable to the mount,  using synscan for windows , sharpcap for PA and PHD2 for guiding with my zwo asi120mc-s and 30mm zwo guidescope.  I take the images onto my sd card and using a intervalometer.  I haven't got to grips with apt yet so wanted to keep it simple.  I don't dither either, I know I know I should.  But I cant seem to get rid of the horizontal banding very easily atall, it could be the sensor temp getting to high as these were taken last week during the summer but wasn't scorchio nights. I leave a 10 sec gap between each sub frame taken, so hopefully enough time for the sensor to cool a bit.  The horizontal bands aren't in the dark, flat or bias frames only when the light frames are stacked together in DSS.  I'll attach a stacked frame of M31 and a single light frame and dark, bias and flat master frame, so anyone can have a look and see what I mean. I took 10 lights, 5 dark, 20 odd bias and flat for M31.  All the calibration frames were taken just after shooting the light frames and all outside so the temp shouldn't change much between the subs.  It was only a quick go but even when I was imaging the NA nebula I had the same issue at 180 secs exposure.  I have tried the horizontal banding reduction in photoshop with my astro tools set but even after numerous applications of it still no joy. I have read a lot on banding issues with canon dslrs and some people don't have issues.

M31 17-7-21 all stack.TIF MasterDark_ISO800_180s.tif MasterFlat_ISO800.tif MasterOffset_ISO800.tif M31 single light frame.tif

[Snoani]

Hi

I regret that I am not an expert but I have imaged with a DSLR previously.

On stretching your single frame I can see the banding is there (see below) and so the banding on your stacked image appears to be an accumulation of banding on all of your light frames.  As you say it is not on your calibration frames though, so the camera looks ok.  I would therefore think that it is something to do with your mount/guiding, exactly what I couldn't say though.

I would personally recommend that you dither as I hope that this would remove the banding when stacking.  

Jem

 

 

 

[CloudMagnet]

It is just the camera noise I would say. If you stretch the dark frame you will see the same pattern there as below. Not dithering is one of the reasons why this will show as you are constantly adding that noise pattern onto the same pixels of your final image. Dithering will shift that pattern around so when your stacking lines them up again, the pattern will cancel out.

Camera temperature will also play a big part. The warm temperatures of the summer, combined with a reasonably long exposure you are working at wouldn't surprise me if the sensor was reaching 30 Celsius, darks will only do so much, the noise will still be there.

[AstroNebulee]

Thank you for your guidance, So it all boils down to starting to dither really then, am I right in that I can dither in phd2? 

[CloudMagnet]

1 minute ago, AstroNebulee said:

Thank you for your guidance, So it all boils down to starting to dither really then, am I right in that I can dither in phd2? 

Yeah, it will help a lot. Setting up dithering would normally done using another imaging program such as Astrophotography Tool or Sequence Generator Pro. They will work with PHD2 to synchronise the dithering between exposures.

It wont solve the problem entirely, that would only happen with a cooled dedicated astronomy camera, but you should see a big improvement in noise levels.

[AstroNebulee]

I shall have to try and get my head around apt or nina then to get the dithering sorted with my dslr. No way I can afford a dedicated cooled osc yet anyway, thank you again, thd learning curve just got steeper haha 

[CloudMagnet]

Its a good way to do it, one step at a time. When I used a DSLR to image with, I started with just tracking first, then added in guiding and controlling the camera using APT later. Really helped ease moving to a dedicated camera at a later date. Better I think than learning everything at once.

[AstroNebulee]

Yes I agree it's a lot to get my head around at the moment, nina or apt is the way forward for me then, that or an asi air pro but can't do that az my zwo asi120mc-s isnt supported, thank you again for your help 

[Clarkey]

I have exactly the same problem of horizontal banding on my 600D - seems to be a bit of an issue with the camera. I dither, but even doing this does not get rid of one particularly bad strip across the middle of the frame. I have tried various bits of software to remove it, but with limited success. I have had to resort to manually removing the banding during processing. Your noise pattern looks a bit more random - so hopefully dithering will do the job. However, about 1/3 of the way down the frame there is a more pronounced strip which may cause problems.

It should be noted that the nighttime temperature at the moment will only give you more noise. In the winter when you are going to do the bulk of your imaging the cooler weather (and sensor) should help. On that note - leave the LED panel open to allow the heat to escape more easily. Also, you could use shorter subs and extend the waiting time between to allow the sensor to cool slightly.

To be honest, the noise from my 600D annoyed me so much, I abandoned it as a deep sky camera.

[wimvb]

fixed with CanonBandingReduction in PixInsight. It would need a little more tweaking to completely clean up the banding. Dithering would help, but probably won't remove all of the banding. In my experience, longer exposures will drown this pattern, as will increasing the total number of subs.

[AstroNebulee]

3 hours ago, Clarkey said:

It should be noted that the nighttime temperature at the moment will only give you more noise. In the winter when you are going to do the bulk of your imaging the cooler weather (and sensor) should help. On that note - leave the LED panel open to allow the heat to escape more easily. Also, you could use shorter subs and extend the waiting time between to allow the sensor to cool slightly.

Yes thats what I thought with the temperatures at the moment, I'm not even bothering this week atall even with my clear skies. I was thinking of trying 2 min subs and see how I go, it may be a case of in the summer do shorter subs and longer interval and opposite in the winter until I can afford a osc. Thank you again for your input 👍

[AstroNebulee]

1 hour ago, wimvb said:

fixed with CanonBandingReduction in PixInsight. It would need a little more tweaking to completely clean up the banding. Dithering would help, but probably won't remove all of the banding. In my experience, longer exposures will drown this pattern, as will increasing the total number of subs.

Thank you, you've done an amazing job there. I am definitely going to dither once I've got my brain around it. So your suggesting I could do longer than 180sec subs as long as there is more of them? I mat try shorter subs and more of them firstly and experiment in the warmer nights (but not this week) and see what the maximum exposure time is before banding occurs. Thank you for helping me 👍

[wimvb]

2 hours ago, AstroNebulee said:

I mat try shorter subs and more of them firstly and experiment in the warmer nights (but not this week) and see what the maximum exposure time is before banding occurs.

My guess is that you will see the banding more in shorter exposures. Normally this banding is related to the read step of the sensor. If you expose longer, there is more signal to drown this pattern, and it should be less of an issue. Such was the case with my images from a pentax dslr before I moved on to a cooled cmos camera. Other things that you can experiment with is saving images on the cameras sd card vs downloading them directly to a computer, and using a battery in the camera vs a power adapter and the camera battery removed. I've read that data download, and heat from the battery have caused artefacts in peoples dslr images.

[AstroNebulee]

Thank you, I shall give these suggestions a go and see what works best. 

 

[Clarkey]

2 hours ago, wimvb said:

My guess is that you will see the banding more in shorter exposures. Normally this banding is related to the read step of the sensor.

The reason I suggested the shorter exposures was to help keep the sensor temperature down. Also, with my 600D the longer exposures seem to exaggerate the problem. However, the simple option is to try both (with dithering) and see which works best.

 

7 hours ago, wimvb said:

CanonBandingReduction in PixInsight

I have been considering PI for some time. This is another reason for the change. I think I'll need to get the credit card out (and permission from my financial advisor)🤣

[wimvb]

27 minutes ago, Clarkey said:

The reason I suggested the shorter exposures was to help keep the sensor temperature down

Removing the battery and using a mains adapter helped some to keep the camera temperature down. Long exposures drain and heat up batteries.

[powerlord]

One suggestion.. Rotate the camera half way through the subs. Even better rotate a few times. Depending on how you've mounted it on your azgti I grant you this could be tricky, but with a ball and socket on there not so hard.

[david_taurus83]

It's the current weather. Make sure the screen is flipped out and switched off as well while your shooting. Try to avoid using LiveView to focus as this really ramps up the sensor temperature.

With regards to sensor temps and having a 10s gap between subs, this won't make any difference. I made a peltier coolbox for my 600D a few years ago purely to make temperature controlled darks. I noticed that the sensor temperature was more dependent on ambient temperature than an exposure length. So a 300s sub didn't have much of a temperature increase over a 60s sub. Maybe a degree or 2. At cooler ambient temps (winter) the sensor used to level out at around 5 or 6 degrees above ambient. At warmer ambient temps (summer) it would get to 8 or 10+ degrees warmer.

I accidentally left the flip out screen closed and lit up one night and I seen temps of over 40°C!

[AstroNebulee]

2 hours ago, powerlord said:

One suggestion.. Rotate the camera half way through the subs. Even better rotate a few times. Depending on how you've mounted it on your azgti I grant you this could be tricky, but with a ball and socket on there not so hard.

I use my Canon 600D with my sw 72ed so I don't use a ball head on it, but rotating slightly seems like a one plan. Thank you 👍

Edited July 20, 2021 by AstroNebulee

[AstroNebulee]

1 hour ago, david_taurus83 said:

It's the current weather. Make sure the screen is flipped out and switched off as well while your shooting. Try to avoid using LiveView to focus as this really ramps up the sensor temperature.

Yep it is the weather also, I do image with the screen flipped out but on, so will give it a go of switching off after focus and frame set up is done 👍thank you 

Edited July 20, 2021 by AstroNebulee

[AstroNebulee]

3 hours ago, wimvb said:

Removing the battery and using a mains adapter helped some to keep the camera temperature down. Long exposures drain and heat up batteries.

It's another good tip to try out seems this dslr as quite a few are prone to this phenomenon, hopefully in the autumn when it's a little cooler I can get better images too with the help of all your good words, I've got a asiair pro coming soon, and this will help simplify my astro sessions too. Thank you