9 replies to this topic

[ebonnevi]

Hello everyone,

 

I have this image, stacked with Deep Sky Stacker. I did some basic strech but now I don't know how to remove the "banding" or square color that I have all aroung the picture. My calibration image look fine, well i think.  Is this a problem with the calibration?

 

Thank for your help. I have Pixinsight and photoshop but not sure where to start to correct this. 

 

 

 

[Raginar]

Did you shoot flats?  I think that would get rid of them.  How was the rest of your calibration data? Darks? Bias?

 

Does it show up in the original images? Is this a color camera?

 

We need more data.

[StarBurger]

Which scope, camera etc? Flats /darks used? # of frames?

There are the makings of a better image under all that.

[ebonnevi]

More details:

Flat: 50, looking good

DARK 25, looking good

BIAS: 50 looking good

Light: 240 seconds, gain 120

I used the same calibration for another picture for the same night and this square do not show up. (strange ya)

 

Color Camera: ZWO 294 MC

Original picture have not this problem

Scope is a Meade Series 6000 APO 115mm with field flatener

[Slice1969]

I'm definitely not an expert,  but if the pictures from the first night are fine, and you are just getting it the second night, then I would start looking to see what may have been different?

 

Was the temperature roughly the same?  If not, your darks would have some mismatch.

 

Did you change anything in the setup?  Cables, power sources, etc.

 

Did you change the length of the exposures?

Edited by Slice1969, 25 January 2021 - 11:24 AM.

[bignerdguy]

It could be your flats.  2 Questions:

 

1) Do you use an LED flat panel for taking the flats or do you do sky flats?

2) What was the exposure length of each individual flat file?

 

If the answer to #1 was a yes and the answer to #2 was an extremely short length that is your answer.  I ran into something like this on my system as I am using an LED light box i made. Since the LED's are very bright I was having to take extremely short shots but each individual shot had a totally different ADU value.  Turns out the reason for this is the fact that LED's flicker at really fast speeds but with a camera if you take a really short length exposure, you can actually catch the image at different points during the flicker, so some photos will be brighter and some dimmer than the others.  When you combine the flats this throws off the values and causes the banding/boxing/rings you see in your image.  the solution is to reduce the brightness of the LED panel (I did this by adding a dimmer circuit) and then taking a longer photo.  This causes the imager to stay on through at least one or more complete cycles of dimming/brightening and will give you a flatter response to the image and ADU values.  Doing this solved my issues i was having some time ago.  If you are doing something similar, try what I suggested and see if this makes a difference.

[ebonnevi]

No i didn't use a LED flat panel, I simply put a white shirt on my scope and check the histogram to set the exposure time..

The exposure time of each flat is the same 0.02s for this one

[michael8554]

Were the images taken recently = Full Moon ?

 

Then it's Light Pollution that won't be removed by Flats.

[ebonnevi]

Yes taken last weekend... can the moon do that?

[kwong wu]

Hi ,I am interested in buying Mead series 6000 APO 115mm. What is your comment ? focuser is good ? Thanks !