Hi everyone,
I have a technical question about an artefact I am seeing in a stacked image, and I would appreciate the opinion of more experienced imagers.
The attached image is a stack of about twenty-five 120-second exposures of the Headphones Nebula / Jones-Emberson 1, taken with the iTelescope T5 system. The data were acquired through the Clear filter and the image shown here is displayed with Siril’s Autostretch, so of course the effect is strongly enhanced.
The telescope is iTelescope T5:
https://support.itelescope.net/support/solutions/articles/231902-telescope-5
As far as I understand, this system uses a Takahashi Epsilon 250, 850 mm focal length, f/3.4, with an SBIG ST-10XME CCD. The camera is explicitly described as non anti-blooming.
What puzzles me is the diffuse nebulosity / halo-like glow visible around some of the brighter stars. I am fairly sure this is not classical blooming, since I do not see the typical vertical streaks or charge-spill trails in the individual frames. But I am also quite sure that this is not real nebulosity in the sky, because the survey view of the same field does not show such diffuse structures around those stars.
So my current suspicion is that this may be some combination of:
broad PSF wings around bright stars, strongly enhanced by the autostretch;
scattered light in the optical train;
internal reflections or filter/window reflections;
CCD-related effects, possibly related to the ST-10XME sensor or microlenses;
or simply a known behaviour of this particular telescope/camera/filter combination.
I am attaching both the stretched stack and a reference field view, to make clear that the diffuse structures are tied to the brighter stars rather than to real emission in the field.
Does anyone have experience with this kind of artefact on SBIG ST-10XME, Takahashi Epsilon, or specifically iTelescope T5 data?
Is this a known effect, and is there a recommended way to mitigate it during processing, apart from avoiding overly aggressive stretches or masking the bright stars?
Thanks in advance for any insight. I am still learning how to distinguish real faint structures from instrumental or processing artefacts, so any diagnostic hints would be very useful.
Best,
Claudio
📷 comp_r_clear_stacked.png
📷 Telescopius simulation.png
