Player One Poseidon-C prominent star halos - Forums

Topic starter

23 days ago

Hello all!

I've recently upgraded to an IMX571 camera from an old unmodded DSLR setup using a RedCat51 and have been quite happy with the first week of imaging. However, one issue that I haven't been able to mitigate is the presence of prominent star halos surrounding brighter, hotter stars. This is quite an issue when imaging the Pleiades. I originally believed that the halos were due to filter reflections (Optolong UV-IR cut) but the strong halos persist with the filter removed and with shorter exposures. Has anyone had any luck or have any suggestions to minimize blue star halos in broadband imaging? I've attached a few examples of stacked but unprocessed screengrabs of M45, a single exposure of the horsehead nebula depicting the same issue, and a comparison frame with and without the filter. I'm planning to deal with the halos in processing but was wondering if there's a hardware solution that could be attempted or if it's user error on my part.

I'm suspicious that it could be due to interactions within the protective window of the sensor though those should be reduced/eliminated by the anti-reflective coating? It could also be due to other optics or a combination of components. No halos were observed in previous imaging session with the Redcat51 and a DSLR. The halo issue seems to be present even in the Pleiades photo displayed on the Player One website describing the camera and in a few other astrobin images using the same camera and various scopes so it may just need to be dealt with using some masking and black point adjustments in processing.

Thanks for the help!

Stacked, unprocessed 90s exposures:Stacked, unprocessed 20s exposures:Single 120 s exposure Horsehead nebula:Comparison of single 90 s exposure with (right) and without (left) the UV-IR cut filter:

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bigCatAstro

Frequent contributor

23 days ago

I take it that you are separating the stars from the nebula before stretching, right?

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Ryan Winkler

Topic starter

23 days ago

Good question. Yes, I typically stretch the stars and nebulosity separately. The images posted are still linear (STF applied) and haven’t been processed. They’re either single exposures or a stacking product of 90 or 20 sec exposures.

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bigCatAstro

Frequent contributor

23 days ago

Ryan Winkler · Dec 18, 2025, 11:26 PM
Good question. Yes, I typically stretch the stars and nebulosity separately. The images posted are still linear (STF applied) and haven’t been processed. They’re either single exposures or a stacking product of 90 or 20 sec exposures.

My fault, I missed that detail! So, I think you’re seeing halos due to your current set-up, specifically with the Player One Poseidon-C. You were using an unmodded DSLR and those have more filtration happening. You’re certainly right, the halos do exist in the sample images on the site. Personally, the halos don’t bother me, but I totally get not wanting them.

Was the UV/IR filter used on the 20 second stack?

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Ryan Winkler

Topic starter

23 days ago

No worries. The filter was used in the 20 sec stack. I did a quick comparison of multiple exposures taken with no filter and the halo was not significantly affected but I did see a decent amount of star bloat.

Thanks for the input. I’ll play around with layering the different exposure stacks and star de-emphasis and see how the final image turns out.

Thanks for the input! It’s most likely an artifact I’ll live with when doing broadband imaging with hot stars in the frame.

alpheratz06

23 days ago

Hello

If I look in the upper left corner of the HH nebula, I can see the halo disk is not centred around the star image : to my opinion this is a sign that excludes IR bloating but suggests this is a parasitic reflection in the optical train.

It could be in the core optics themselves (bad luck) or in poorly AR coating in filters if any.

I got miserable such halos in a RC8 , which where highly dimmed when I purchase better quality IR filters.

Just for the sake of completeness, make sure it is not an effect of light dewing on the front lens or on thecamera windows if it is cooled.

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Ryan Winkler

Topic starter

20 days ago

Thanks for the reply. The halo offset dependency on the distance from the center of the frame definitely struck me as odd.

I live in a relatively dry climate (northern New Mexico at 8000 ft elevation) so I didn’t believe that dew would be an issue, but I did test by taking a series of exposures with the on-camera dew heater engaged at default settings. No change in the halo behavior unfortunately.

I don’t have any other scopes to test with at the moment but I can throw in a 100 mm canon lens for some images to see if I can isolate it to the redcat scope.

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Ryan Winkler

Topic starter

19 days ago

It seems like this issue may be due to the lack of AR coating on the sensor window (unless Player One used something completely transparent!). I’ve reached out to support for guidance to see how they’d like to move forward. Some testing and additional images with a variety of optical trains and filters can be found here:

Player One Poseidon-C prominent star halos - Beginning Deep Sky Imaging - Cloudy Nights

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Guillermo (Guy) Yanez

10 days ago

Hello Ryan. I may be jumping in a little late on the topic, but I just wanted to mention that I am very confident PlayerOne cameras do not come with a built-in UV/IR-cut filter, unlike ZWO and other brands. You will need a filter to eliminate halos unless you are already using a narrowband filter such as the L-Pro or L-Enhance.

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Ryan Winkler

Topic starter

10 days ago

Guillermo (Guy) Yanez · Dec 31, 2025, 09:27 PM
Hello Ryan. I may be jumping in a little late on the topic, but I just wanted to mention that I am very confident PlayerOne cameras do not come with a built-in UV/IR-cut filter, unlike ZWO and other brands. You will need a filter to eliminate halos unless you are already using a narrowband filter such as the L-Pro or L-Enhance.

Thanks for the reply! A series of test shots with and without a UV/IR-cut filter display the same issue around all bright stars (regardless of star color). The halo problem has been isolated to the sensor window where a new vendor was used to source the part and most likely no AR coating was applied. Player One has responded to the CloudyNights thread and will send out verified replacement sensor windows as soon as their vendor and internal testing are complete. Hoping for the new window soon!

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Guillermo (Guy) Yanez

10 days ago

Ryan Winkler · Jan 1, 2026, 02:50 AM
Guillermo (Guy) Yanez · Dec 31, 2025, 09:27 PM
Hello Ryan. I may be jumping in a little late on the topic, but I just wanted to mention that I am very confident PlayerOne cameras do not come with a built-in UV/IR-cut filter, unlike ZWO and other brands. You will need a filter to eliminate halos unless you are already using a narrowband filter such as the L-Pro or L-Enhance.
Thanks for the reply! A series of test shots with and without a UV/IR-cut filter display the same issue around all bright stars (regardless of star color). The halo problem has been isolated to the sensor window where a new vendor was used to source the part and most likely no AR coating was applied. Player One has responded to the CloudyNights thread and will send out verified replacement sensor windows as soon as their vendor and internal testing are complete. Hoping for the new window soon!

I am glad that PlayerOne is offering a solution by replacing the sensor window with appropriate AR coatings. Other than that, I would check if the dew heaters are doing their job in case you are in a cold area, and perhaps look for internal reflections in the imaging train. I also own a Redcat 51 and I do get some halos when paired with the ZWO 533MC Pro using narrowband filters. I suspect that getting a definitive solution is not around the corner, but you can certainly reduce those halos to an acceptable level. I think you are above the threshold.

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