Tadpoles in Orion

a51T2EFP

This is a 3 minute 9 image 20 seconds stack of The Orion Nebula. I see all sorts of 'tadpoles and dark spots that wash out after some more imaging time. Has anyone else seen this in their shorter exposures? This is with my S50.

Moontanner

a51T2EFP
Great post! Tadpoles attack!

I don't have a Seestar, so can't say I've seen this exact problem. I have however tried stacking thousands of very short exposures before to see the results firsthand. The result was lots of strange lines and spots that I assumed were read noise.
Maybe it was the early stages of troop mobilisation for the looming tadpole invasion force.

Brille

That's very unusual. I've never seen anything like this before. Did you only notice the dark "tadpoles" on this stacked M42 image, or did you notice it on other images as well? Have you looked at the shape of the dark spots (which are all oriented in the same direction) on the individual lights? Are they visible there as moving dots, or as elongated spots on a single light?

a51T2EFP

Brille This is a first to me. I have not seen this before. But, I have never imaged this for less than 15 minutes. I wanted to image to keep the trapezium from being washed out. But, got this instead. The dark 'tadpoles' are sharp and there are no anomalies on the aperture or sensor. I have never seen this in any other images, which tell me they are a part of the foreground. Maybe someone can duplicate my results to confirm the existence of these interesting details. It's been snowy and cloudy here so I haven't been able to try again. Now, I did this image all in the S50. I just tried through Siril, and all the tadpoles disappeared. However, they are in the subs.

Brille

To get to the bottom of the cause, I would actually take a look at the individual subs. Are the “tadpoles” visible on all lights, or do they disappear at some point? What shape are they? Are they dark spots that move, or are they elongated streaks that are static from the outset? To determine whether there is dust in the optics/on the Seestar sensor, you could check whether the stripes always remain in the same position relative to the background. The Seestar moves the position slightly every 5 lights to drizzle the images when stacking. If the spots remain in the same place, then you have definitely captured something that was actually visible in the sky.

a51T2EFP

Looking and studying the results, The spots are not all the same. Some longer, some shorter. I would really like to see if someone can duplicate this, and process the stack in the S50.

Brille

To investigate this further: Was the Seestar tilted during the shooting? Are the tracks pointing exactly downwards, suggesting moisture droplets on the sensor? To answer this, we would need to know whether it was mounted on an EQ or AltAz mount, as well as the location and time of recording. Some of the tracks are visible below the nebula and are blacker than the deep sky background. This again suggests some kind of effect in the Seestar's optics. Do you have a way to make the lights available via Google Drive or Dropbox? I'd like to take a closer look at them.

a51T2EFP

Brille After going through the lights. I didn't see the dark spots. They seem to have entered through the stacking in the S50. The night was nice, EQ mode. Never had a problem tracking. The Fits stack shows what may be noise where the dark spots are. And the processing didn't remove them. I am beginning to think it was noise from not enough images to stack. Here is the JPG version with all the spots. This is the stack of nine images. Looks like noise.

a51T2EFP

Brille Put the wrong image up.

Brille

Yes, it seems to be noise.

a51T2EFP

Thanks for your input. They did look kind of interesting though.