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Tommohawk

16 Aurigae - strange goings on!

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I'm working on a NB version of the Flaming star and surrounding area, and whilst doing a sort of pre-process I noticed something very odd with 16 Aurigae in the SII stack. Initially I thought this must be just a stacking artefact, but closer inspection shows the artefact occurs on the individual subs too.

Couple of thoughts:

It could be some kind of diffraction effect caused by eg an insect on the objective lens. BUT it's only on 16 Aurigae (mag 4.5) and not on 14 Aur (mag 5) shown top left. You'd think that kind or artefact would show on all the brighter stars.

Initially I thought it was only on the SII images, but I can see its also becoming visible on the OIII I did previously, and is completely missing from the subsequent SII I did last night. So it was a transient effect, and I can see subtle changes in the 5 minute SII images.

So here's a stack of the 11 affected images showing also surrounding stars of similar brightness;  what's the verdict… cosmic event or creepy crawly?

694323284_SIImod_crop.thumb.png.ab54aa39ad67d6a0695e77a5ebb48feb.png

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That is bizarre, and something else that’s strange, after opening the image in a separate window to take a closer look, when I close that window and return to your original post, the star has disappeared from the image!

I guess that’s something wrong with my browser.
 

As to the artefact, I’m at a loss to explain it, as you say something on the optical train unless it was very close to the sensor would affect the other bright stars.

Maybe a drop of moisture on the sensor which has since evaporated? I have had that on cooled cameras particularly when imaging near the zenith.

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1 minute ago, tomato said:

That is bizarre, and something else that’s strange, after opening the image in a separate window to take a closer look, when I close that window and return to your original post, the star has disappeared from the image!

I guess that’s something wrong with my browser.
 

As to the artefact, I’m at a loss to explain it, as you say something on the optical train unless it was very close to the sensor would affect the other bright stars.

Maybe a drop of moisture on the sensor which has since evaporated? I have had that on cooled cameras particularly when imaging near the zenith.

Droplet on sensor sounds plausible - but you'd think this would still affect other stars. Also there seems to be some structure going on which I don't think could be created by a droplet on the sensor.

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Sorry, bit of a bump - but does anyone else have any thoughts on this? Its driving me bonkers!

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Hi Tom, to me it looks similar to this..  a spiral around 4th mag 52 Cygni on 9hrs of Ha on NGC6960..  I assumed it was an ASI1600 microlensing effect, it shows on all the subs..  Not seen anything like it on any since..  Have you seen it on any other images?

Dave

NGC6960_Ha_Int_Reg100.thumb.jpg.6e32198106ee797ee68b7acba0ad947f.jpg

 

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Hi Dave - thanks for that. Sorry I thought Id replied but must have forgotten to hit Submit!

Your image shows the horizontal filaments you'd expect in that area plus the odd spiral you refer to. Mine shows horizontal striae/filaments which  just shouldn't be there. 

I'd not heard of the ASI1600 microlensing issue, but looking around I can see other folk have mentioned it. However mostly the effect other folk refer to seems to be like this which is different yet again. I also get that defect - sort of like short squat diffraction spikes - but it doesn't bother me too much. Curiously, that example also refers to 16 Aurigae, as in my case!

The thing that is especially odd with my 16 Aurigae is that it only occurs on that one star and not on adjacent ones which are only 0.5 mag dimmer. It was also definitely transient. Initially I though it was a filter artefact on SII, but I can see it was also evident on the last few subs on the previous filter, OIII. By the following night it was no longer discernible.

I guess a tiny droplet on the sensor could do this, but I'd still expect some effect on neighbouring stars. I've never had this before BTW even with very bright stars. The striae do look quite "real" to me - but I guess if 16 Aurigae was going supernova or something we'd have heard about it by now!

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It doesn't look typical of the Microlensing effect.  Mark who did the analysis on the Cloudy Night thread is a member on here (sharkmelley), hopefully he might see this post and dive in with his opinion, he's very good at analysis. 

Carole 

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