Banding..what is causing this?

[StargeezerTim]

Hi all,

I had a couple of images from two nights ago that have been ruined by banding. As soon as I apply even light stretches, I get the effect shown on the image. The conditions were clear but 'heavy', the seeing wasn't great. Good enough for consistent guiding though. The camera is a modded 1200D and I used a UHC clip filter. The scope was a 72 ED-R. 

I have noticed banding on this camera before but not to this extent or so soon after starting processing. I also noticed the histogram of the autosave in DSS was much thinner than usual and way to the left. The image is a stack of 30x6min subs, iso 800.

I would appreciate your thoughts about why this has happened. Also, I am finding it impossible to process. Noels horizontal banding reduction helps but not enough to get a reasonable image. If anyone has any suggestions for salvaging something from the image I am all ears...Cheers, 

 

Edit.. here is the image with another little stretch...

 

 

[wimvb]

First thought: what do the dark and bias master look like? Does this banding occur in the single subs?

To clean this up, if you have access to pixinsight, use canonbandingreduction. If you don't have access, pm me and I can do it for you.

Cheers,

[StargeezerTim]

5 hours ago, wimvb said:

First thought: what do the dark and bias master look like? Does this banding occur in the single subs?

To clean this up, if you have access to pixinsight, use canonbandingreduction. If you don't have access, pm me and I can do it for you.

Cheers,

Thanks Wim... The dark and bias files are OK. I'm trying again tonight so I'll wait and see if it happens again. I have a hunch that the seeing was so heavy last night it caused problems, but I'll wait and see what happens. Tim. 

[wimvb]

I would say "good luck", but it's already past. Holler if you need help with removal. 

Cheers,

[PeterCPC]

19 hours ago, wimvb said:

First thought: what do the dark and bias master look like? Does this banding occur in the single subs?

To clean this up, if you have access to pixinsight, use canonbandingreduction. If you don't have access, pm me and I can do it for you.

Cheers,

Wim - where is canon banding reduction in PI - I can't see it in my version (1.8)

Peter

[StargeezerTim]

9 hours ago, wimvb said:

I would say "good luck", but it's already past. Holler if you need help with removal. 

Cheers,

 

6 hours ago, PeterCPC said:

Wim - where is canon banding reduction in PI - I can't see it in my version (1.8)

Peter

I got a better image last night, i think the heavy seeing the night before really bought the worst out of the Canon.

I have just discovered that I have got a banding noise reduction function in the free software, the Nik Collection. Its in the Dfine 2 plugin. I've just been playing with it, it works pretty well but is better on mild banding. It looks like the really severe effect I had is most likely not recoverable, though with patience, I could probably rescue an OK image.

[wimvb]

It's under Scripts > Utilities. I put it in my favourites as well. Comes in handy all to often.

[wimvb]

3 minutes ago, StargeezerTim said:

 

I got a better image last night, i think the heavy seeing the night before really bought the worst out of the Canon.

I have just discovered that I have got a banding noise reduction function in the free software, the Nil Collection. Its in the Dfine 2 plugin. I've just been playing with it, it works pretty well but is better on mild banding. It looks like the really severe effect I had is most likely not recoverable, though with patience, I could probably rescue an OK image.

[DavM]

Try dithering, it certainly got rid of the banding problem on my Canon 40D!

I also only use flats and bias cal frames!

regards Dave

[sharkmelley]

It might be worth experimenting with a higher ISO e.g. 1600 maybe more.  Higher ISOs often reduce the amount of Canon banding.

Mark

[ollypenrice]

In CCD imaging I get this on shorter exposures, sometimes. I don't know if longer subs would help with your Canon but they certainly work for me.

If you get it so badly that you can see the different background values in Ps Curves you can probably fix it. Open Curves and put the cursor in the middle of the darkest part of a band and Ctrl click to put a marker on the Curve. (We'll call it Marker A). Move the cursor to the brightest part of a band and repeat. (Marker B ) Now pin the curve above these markers in several places to prevent it from being moved. Make Marker A active and type in the same output value as Marker B. That should do it, but it will only be possible for severe banding.

You might also save the data by careful use of the Dodge and Burn brushes. Give the brush the diameter of one of the bands and run it horizontally along the band to lighten or darken as needed. Not ideal but better than scrapping the data.

Olly

[StargeezerTim]

3 hours ago, ollypenrice said:

In CCD imaging I get this on shorter exposures, sometimes. I don't know if longer subs would help with your Canon but they certainly work for me.

If you get it so badly that you can see the different background values in Ps Curves you can probably fix it. Open Curves and put the cursor in the middle of the darkest part of a band and Ctrl click to put a marker on the Curve. (We'll call it Marker A). Move the cursor to the brightest part of a band and repeat. (Marker B ) Now pin the curve above these markers in several places to prevent it from being moved. Make Marker A active and type in the same output value as Marker B. That should do it, but it will only be possible for severe banding.

You might also save the data by careful use of the Dodge and Burn brushes. Give the brush the diameter of one of the bands and run it horizontally along the band to lighten or darken as needed. Not ideal but better than scrapping the data.

Olly

Cheers,

The Curves method works a treat with some repeated goes. managed to get a band free (almost!) image from it.  Tim. 

[ollypenrice]

Like all these fixes it works best as a layer, then you can be selective about where to apply it. Sometimes a partial fix is better (more natural) than a full fix but I'm glad it worked for you. On occasion an image has to be made to behave!   Oh yessss!

Olly