Diamond shaped stars

[Les Tilly]

I have just started to use pixinsight I used the Batcg reprocessing Script and i get Diamond shaped stars ant suggestions to making them round

Les

[oldwexi]

Hi Les!
What optics have you used?
It looks like spikes introduced by obstructions
infront of the optics or in the optical path.
Gerald

[Les Tilly]

I use a Tak 106 newQ and FLI 16803 I have perfectly round stars when i do it in other programs

Thanks for replying
Les

[Josh Lake]

Can you post an example frame from PI and from another program to compare? I wonder if it's simply a case of PI's Screen Transfer Function stretching the data more aggressively than other programs and so you're seeing a structure that's in all of them. Have you opened the circular-star frames in PI to verify?

[Geoff]

You could try changing the registration algorithm in BPP.  I find that "Auto" (the default) often gives me strange artifacts.

[Alejandro Tombolini]

Hi Les, maybe it is not related to PI. This picture was taken with the same telescope and a Canon 5D.
The following screenshot has four image of the same star of 5, 15, 60 and 300 second, directly from raw, without process (only debayered), and besides the bayered ones.
It can be seen that when exposure time increase, the diamond appears.
Saludos, Alejandro.

[Juan Conejero]

As always happens in these cases, we really need to work with a sample of the data where the problem can be reproduced.  Otherwise all we can do is speculate.

I seriously doubt this can be caused by any of the interpolation algorithms in StarAlignment. All of these algorithms are isotropic by nature. They can cause some ringing, which can be controlled with the clamping parameter and, in extremely difficult cases, by choosing an inferior algorithm such as bicubic spline or even bilinear. But ringing cannot deform star shapes this way. Definitely, I need to see a sample of the original data.

[ruediger]

Could it be related to spikes introduced by the micro lenses of the sensor?
At least the Kodak 8300 is known to produce similar looking star shapes.

But this doesn't explain why you get round stars in other programs.

Rüdiger

[vi100]

Could it be related to spikes introduced by the micro lenses of the sensor?
At least the Kodak 8300 is known to produce similar looking star shapes.

But this doesn't explain why you get round stars in other programs.

Rüdiger

+1

[Les Tilly]

Sorry for not getting back sooner. I went over a few more images and found it also in unrelated Pi images  Could this be a Under sampling Issue that Basically can only be seen by zooming in on the image?

Les

[lucchett]

Hi,
i am seeing this only now..
I have the same issue, same chip.
The defect is either induced or revealed by the image registration algorithm.
All lanczos show the issue. Low clamping can mitigate the problem.
Changing the method does eliminates the issue, but with a loss in resolution.

Stars are slightly diamond shaped, they show something like subtle spikes.

Andrea