Banding

[Bottletopburly]

I have noticed a banding on my images during last two sessions , now the only thing that changed was  my guide camera , now could it be I’m now dithering too many pixels , could it be led flat panel faulty causing issue  , stacked in Siril as normal using script no darks , I will restack lights on their own and see if I can work out if it’s flats or bias frames causing issues or if dithering causing, has anyone seen this before 

[+RonC]

I had this a while ago and I sorted it by adding another paper layer to my LED panel..?

Not sure if this will help as it wasn't as bad as your example!

Cheers

Ron

[+Derbyshire Dave]

1 hour ago, RonC said:

I had this a while ago and I sorted it by adding another paper layer to my LED panel..?

Not sure if this will help as it wasn't as bad as your example!

Cheers

Ron

Yeah, I had exactly that too whilst taking flats, and agree with Ron, another layer of paper sorted it.

 

Process of elimination though, so let us know how you get on Dave

[Bottletopburly]

Cheers @RonC @Derbyshire Dave   I think you maybe right I was thinking it may be to do with the refresh rate will have a play , camera still fixed to scope so I can redo flats and check will update.

[+Ibbo]

Just a thought if you can rotate the flats panel.

[Bottletopburly]

1 hour ago, Ibbo said:

Just a thought if you can rotate the flats panel.

Good idea 💡 Steve 👍

[Bottletopburly]

Seem to be getting somewhere problem is the flats , I tried with an iPad setting histogram one third from left no banding seen even using the stretching in APT , now I put two sheets of white baking paper in front of panel no difference add white A4 paper, the same , banding can be seen but if I use pink paper instead of A4 paper   Set histogram one third to left ( I measure  exposure using av mode on Nikon but manually set in Apt as  av mode can’t be set the same as a canon in APT ,  will run a stack in Siril and see how it compares to the iPad flats ( tried turning flats panel makes no difference).

[Bottletopburly]

Interesting article on taking flats for dslr https://www.myastroscience.com/proper-flats-with-dslr

[Bottletopburly]

So before i bin the EL panel i have now put two A4 sheets between perspex and EL panel and followed the advice in article https://www.myastroscience.com/proper-flats-with-dslr so a 20 sec exposure gives a mean value of 16383.0  so  a bit of experimenting with exposures i need half that and a 1.2 sec exposure gives a Mean value of 8055.5  can anyone tell me is the 1.2 sec looking any good for a Flat ,using AV mode does not work properly.

 https://www.dropbox.com/s/znfszypsbnuwart/Single__0003_ISO200_20s__NA.NEF?dl=0

https://www.dropbox.com/s/l9n7kybunsq1h1g/Single__0007_ISO200_1.2s__NA.NEF?dl=0

[Clive]

Are the flats for a OSC? If so, is the mean ADU the same for each channel?  The 1.2s image seems to be lacking in green?

[Bottletopburly]

Thanks @Clive  osc  Nikon D5300 it seems that article is not true and you can’t treat a dslr the same as a ccd I will have a tinker with the Av setting now I have put two white A4 sheets in front of panel  it may be the EL panel is duff due to the banding I was getting.

[Bottletopburly]

Tracing panel ordered off eBay £9.99 can’t be doing faffing about with the EL panel (which I think is duff due to banding which it wasn’t doing before)

[+Graham]

Just a thought on this.

If you have rotated the flats panel 90 degrees and it made no difference then the issue must be with the camera not the panel.

[Bottletopburly]

54 minutes ago, Graham said:

Just a thought on this.

If you have rotated the flats panel 90 degrees and it made no difference then the issue must be with the camera not the panel.

I did think that Graham but using an iPad is fine hence just ordering a tracer panel and cutting my losses with this particular EL panel 

[+Graham]

That would probably have more to do with the refresh rate on the I pad screen and the panel.

There must be a frequency issue between the panel and the camera.

If it was simply an issue with the panel the banding would have rotated with the panel. 

[+Graham]

Do you save direct to the pc from the camera.

Do you use an independent cable from the camera or do you use a usb hub.

[Bottletopburly]

2 hours ago, Graham said:

Do you save direct to the pc from the camera.

Do you use an independent cable from the camera or do you use a usb hub.

When I’m imagining I use a usb3 hub connection to shed pc all running usb3, a chap on Sgl  reckons the 1.2 sec exposure looks good and similar to his 5d flats and he takes his flats similar to the article ,info here https://stargazerslounge.com/topic/351043-flats-issues/?tab=comments#comment-3825441

[+Graham]

Might be worth a try to run the camera on a separate usb cable.

My old Canon used to pick up interference from the power supply when using a hub.

It might also pay to keep the independent usb cable away from the other leads on the rig.  

[Bottletopburly]

1 hour ago, Graham said:

Might be worth a try to run the camera on a separate usb cable.

My old Canon used to pick up interference from the power supply when using a hub.

It might also pay to keep the independent usb cable away from the other leads on the rig.  

I will try that need to take  exposure values with the 200pds as that’s setup on the mount  see what I get from the reflector compared to the refractor , 

[+Graham]

That will be interesting

[Bottletopburly]

Tracer panel turned up and initial test seems promising probably a little bright I ordered the non dimmable version , maybe I can add a dimmer switch at a later date but for now I can use a couple of sheets of white paper so next outing I will take two sets of flats one using Av mode and one using the Nina flats wizard the latter uses a different method using the adu value to find best setting , initial test showed a value of about 0.6 sec nothing to lose, will compare how they look after stretching and wiping in Startools.

[Bottletopburly]

Tracer panel work in progress mounted to a 6mm board and secured usb lead as seems a bit flimsy so will see how it goes as a flats panel 

 

Edited April 17, 2020 by Bottletopburly

[Bottletopburly]

@Graham a. bit more  detective work  on El panels and I read somewhere that to reduce banding on El panels it’s advisable to use longer exposure of 1/2 sec  for Flats so last night I did two flats one using the NINA software flats wizard  which calculates the optimal exposure time via linear extrapolation and that decided on a 0.4  sec exposure and a 0.5 sec exposure using apt setting so will be interesting to see if these work once we get a clear night to check , I used the stretch image function in apt and sure enough at 1/60 th banding can be seen once you start using longer exposures this disappears,  maybe quality of El panels doffer from panel to panel .

note I found the tracer panel to be uselesss as they are side lit from one edge giving uneven illumination .

 

Edited April 29, 2020 by Bottletopburly

[Bottletopburly]

Been messing with El panel , piece of white cloth in front of el panel then sandwich 20 mm frame between panel and Perspex  seems to blur the panel better ,and at 1/40 sec can’t see any banding present so clear night required to test .