Help! Please help identify source of circular gradient in NGC 6960, Veil Nebula?

[oymd]

Hi Everyone

Yesterday I imaged NGC 6960, and during processing I noticed a very obvious CIRCULAR gradient on my image?

I have attached a picture. I intentionally OVERDID the RGBK in Curves to highlight it more?

Is this from bad flats?

Is it from the filter?

Imaging setup yesterday:

 

WO Star71

294MC Pro

L-eNhance filter

65x300s

FULL MOON

 

These flats were taken 2 days ago, and did not produce any similar gradient on any of my Soul or Heart nebula images? Mount & OTA have not been moved or touched for the past 2 days, so did not take flats yesterday night?

The image on screen is after: DBE, background neutralisation, PCC, EZ DENOISE, HISTOGRAM STRETCH AND FINALLY STARNET.

 

 

 

I went back to the raw stacked calibrated Master Light unprocessed image, and just did a Background Neutralisation to remove the green cast, followed by a Histogram Stretch and RGBK curves. Did not do ANY postprocessing.

The circular halo/gradient is there, I think, but much less obvious?

Is it my processing?

Many thanks

Edited September 22, 2021 by oymd

[Catanonia]

Condensation on your sensor.

Happened to me this morning after a pretty dew wet night and took some flats and shat myself when I had a big black spot in the centre of a flat. 

I switched off cooling, switched it on again and it cleared itself up

[oymd]

1 hour ago, Catanonia said:

Condensation on your sensor.

Happened to me this morning after a pretty dew wet night and took some flats and shat myself when I had a big black spot in the centre of a flat. 

I switched off cooling, switched it on again and it cleared itself up

Oh...never thought of that...

How can I avoid it happening in the future? Should I use a dew heater band on the camera and attached filter drawer?

[barkingsteve]

You could get one of these for the 294. 

 

https://www.firstlightoptics.com/zwo-accessories/zwo-anti-dew-heater-strip-for-asi-cooled-cameras.html

[Catanonia]

16 hours ago, oymd said:

Oh...never thought of that...

How can I avoid it happening in the future? Should I use a dew heater band on the camera and attached filter drawer?

Not sure, my 2600 MC Pro has a anti dew function, don't know about your camera.

[GoldTop57]

Were you running the cooler when taking your flats? You could cool in stages so go to 0 degrees leave for 5 minutes and then down to -10 etc.

[oymd]

6 hours ago, GoldTop57 said:

Were you running the cooler when taking your flats? You could cool in stages so go to 0 degrees leave for 5 minutes and then down to -10 etc.

Yes, same temp as the lights. All were at -5C

[oymd]

On 22/09/2021 at 23:23, Catanonia said:

Condensation on your sensor.

Happened to me this morning after a pretty dew wet night and took some flats and shat myself when I had a big black spot in the centre of a flat. 

I switched off cooling, switched it on again and it cleared itself up

Thank you for your suggestion.

I wrapped the camera and filter drawer with one of my extra dew heater bands over the past 2 nights, and the circular gradient is gone. I was imaging IC 1848 over the past 2 nights. No circular gradient!

On Cloudy Nights, the responses I got were very much suggestive its the Moon reflecting on my WO Star 71's objective, but I was imaging the last 2 nights with the full moon out in the same conditions, and using the dew heater bands eliminated the gradient.

So it must be condensation then!

Thanks again..

 

masterFlat_BIN-1_FILTER-NoFilter_CFA.xisf

[Catanonia]

2 hours ago, oymd said:

Thank you for your suggestion.

I wrapped the camera and filter drawer with one of my extra dew heater bands over the past 2 nights, and the circular gradient is gone. I was imaging IC 1848 over the past 2 nights. No circular gradient!

On Cloudy Nights, the responses I got were very much suggestive its the Moon reflecting on my WO Star 71's objective, but I was imaging the last 2 nights with the full moon out in the same conditions, and using the dew heater bands eliminated the gradient.

So it must be condensation then!

Thanks again..

 

 

masterFlat_BIN-1_FILTER-NoFilter_CFA.xisf 133.87 MB · 0 downloads

Excellent and glad it worked out.