S50 EQ mode Weird Color Aberration

JET

Since transitioning to EQ mode i have run across weird looking color gradients. I never had this issue targeting nebula, galaxies or star clusters before. Even imaging during a full moon never had this happen. This only started happening when switched to EQ.

The M101 was 9 hours on target with 7.5 hours of data at end of imaging facing north with only about 38% moon in the last couple hours of imaging..
The M13 was 3 hours facing south with about 40% moon in the last hours of the imaging.

As stated before, i have imaged with a full moon in Alt-Az and never has this before.

Some have suggested it due to no dithering in EQ mode?
Any suggestions on how to eliminate this?

If i continue to use EQ, should i use Alt_alp? Doe it allow for dithering ot be added?

Help please

See attached photos

Brille

The visible banding and color shifts in EQ-Mode have already been criticized by some people here, including me. The current information from ZWO is that these are peculiarities of the sensor that become particularly clear when stacking in EQ mode. In AltAz mode, the image field rotates so that the sensor also rotates, thus reducing the errors in the sum image.
These problems can normally be corrected with flat images. In future, the app will be expanded to include the option of taking flats in addition to the darks before the actual imaging starts.

JWRI97

Brille

This is good to know about the possibility of introducing flats. I have been wrestling to remove the banding in Pixinsight and whilst I can get it under control its a pain to deal with and even after careful processing its still there upon closer inspection.

Tim1343

This is very helpful to know, I thought I was doing something wrong with my EQ images as they have become very mottled in appearance.

JET

JWRI97
I have not been able to figure out how to make my galaxy look good trying to fix this issue. I was hope more data over differnt night would help ,but it did not. Maybe someone who is really good in PI could fix it but i don't have the skill or knowledge myself

wvreeven

Flats alone may not be sufficient. The usual way to avoid this kind of background issues is to apply dithering while imaging.

JET

wvreeven yeah dithering in EQ mode would help alot i think

ShaneRay

I have been having the exact same problem with my S30

jon

JET

But it does already. Doesn’t it ?

jon

Dear All,

I am experiencing very high noise in the background when shooting nebulas.

Here are two examples of Monkey Head, under city center bortle 9 sky (mag 17.30) and half moon high in the sky, shot simultaneously side by side with the S30 shot in eq mode 20sec with an Optolong L-Extreme filter on top, and with the S50 in alt/az 10sec with the IRCUT filter on.

The background is very grainy on the S30 and with these alternating greenish and blueish patches, which are impossible to eliminate in post processing.

See also a broadband, same night with S30.

And Bubble Nebula with the S50 in eq mode, same situation.

The sky was perfect with no high clouds all night long.

Not sure what is the cause, the filter, eqmode ?

Will this be solved by the future flats functionality, or is this the read noise, or the thermal noise made visible by the narrowband, by eliminating the light pollution glow ?

Support@Seestar

jon
From the images and your description, the grainy background and color blotching you noticed in the S30 narrowband shots are likely due to a combination of factors:

Narrowband filter greatly reduce the broadband light (including light pollution), which indeed makes sensor read noise and thermal noise more visible, especially in high-gain, short-exposure conditions typical of small-sensor systems like Seestar.
While EQ mode allows for longer exposures, it also means more dark current and fixed-pattern noise can accumulate — particularly under warmer ambient temperatures and in the presence of a strong moon. Unlike broadband shots where light pollution fills the background, narrowband shots reveal more of the underlying sensor characteristics.
Future flat frame calibration will help significantly in correcting uneven illumination and color gradients caused by filters, vignetting, and dust shadows. It won't reduce random noise, but it will help with the color patchiness and gradients you're observing.
That said, your S50 results under similar conditions look smoother in comparison, likely due to the IRCUT + broadband combo allowing the skyglow to mask some of the sensor noise.
We’re continuing to optimize our processing pipeline, and your feedback is very valuable in guiding those improvements.

jon

Support@Seestar

Thank you as usual for your prompt response and client centricity !

All the best,
Stevan

abhsieh

Support@Seestar
This seems to be the exact issue I'm having - something I haven't encountered with the Seestar before until this week where temperatures are rising in the evening and there's a full moon.

While we wait for a fix/update from ZWO...is there anything we can do to prevent this from happening?

Support@Seestar

abhsieh
Your problem seems to be caused by insufficient dithering of the color blocks. We will increase the dithering range in the next version. Let's take a look then.

marvindj

As a workaround, use 1.1 framing. Seems to double capture times but on my S50 , eliminated (to my eyes) the banding.