Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Help me identify the problem and the solution

  • Please log in to reply
9 replies to this topic

#1 ebonnevi

ebonnevi

    Lift Off

  • -----
  • topic starter
  • Posts: 11
  • Joined: 11 Oct 2020

Posted 25 January 2021 - 10:11 AM

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?

LEO B2
 
Thank for your help. I have Pixinsight and photoshop but not sure where to start to correct this. 
 
 

 



#2 Raginar

Raginar

    Cosmos

  • *****
  • Posts: 9,698
  • Joined: 19 Oct 2010
  • Loc: Pensacola, FL

Posted 25 January 2021 - 10:37 AM

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.



#3 StarBurger

StarBurger

    Viking 1

  • -----
  • Posts: 710
  • Joined: 06 Mar 2018
  • Loc: North Country NY

Posted 25 January 2021 - 10:38 AM

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

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



#4 ebonnevi

ebonnevi

    Lift Off

  • -----
  • topic starter
  • Posts: 11
  • Joined: 11 Oct 2020

Posted 25 January 2021 - 11:02 AM

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



#5 Slice1969

Slice1969

    Vostok 1

  • *****
  • Posts: 128
  • Joined: 26 Aug 2019

Posted 25 January 2021 - 11:23 AM

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.


#6 bignerdguy

bignerdguy

    Viking 1

  • *****
  • Posts: 613
  • Joined: 31 Oct 2019
  • Loc: Lewisville, TX

Posted 25 January 2021 - 05:52 PM

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.



#7 ebonnevi

ebonnevi

    Lift Off

  • -----
  • topic starter
  • Posts: 11
  • Joined: 11 Oct 2020

Posted 25 January 2021 - 08:18 PM

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



#8 michael8554

michael8554

    Messenger

  • -----
  • Posts: 458
  • Joined: 19 Aug 2020
  • Loc: Wiltshire UK

Posted 26 January 2021 - 04:50 AM

Were the images taken recently = Full Moon ?

 

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



#9 ebonnevi

ebonnevi

    Lift Off

  • -----
  • topic starter
  • Posts: 11
  • Joined: 11 Oct 2020

Posted 26 January 2021 - 06:46 AM

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



#10 kwong wu

kwong wu

    Lift Off

  • -----
  • Posts: 1
  • Joined: 18 Dec 2020

Posted 27 January 2021 - 07:36 PM

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




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics