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What are these artefacts in Telescopius?

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#1 rj144

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Posted 22 June 2021 - 10:44 AM

I've always been curious, just never asked.  If you go to Telescopius and use their FOV tools, you'll see quite a few weird artifacts (typo in title).  Here's one near Orion circled:

 

artorion.jpg

 

That's just one of them, but there are more.  Anyone know what these are?


Edited by rj144, 22 June 2021 - 10:49 AM.


#2 unimatrix0

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Posted 22 June 2021 - 10:56 AM

They use one of the deep sky survey images and these images are also stitched together as a giant mosaic , but also scalable etc.. it's photographic artifacts. 


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#3 rj144

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Posted 22 June 2021 - 11:27 AM

They use one of the deep sky survey images and these images are also stitched together as a giant mosaic , but also scalable etc.. it's photographic artifacts. 

Thanks.  That's what I guessed.  But, why don't they remove them?  That seems fairly simple.  

 

For newbs starting out, who have no idea what nebula are where, they kind of look like a type of nebula.


Edited by rj144, 22 June 2021 - 11:27 AM.


#4 TOMDEY

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Posted 22 June 2021 - 01:03 PM

Looks like a Narcissus Ghost from a bright star in the taking lens. These are very common and appear in the field symmetrically opposite in the parent image. The bright star may be outside of the cropped field that you're displaying there. The 48" Palomar Survey images (taken on 14x14 inch glass plates) are riddled these. It is caused by light reflecting off the 48" Schmidt Plate and back down to the film again. Extremely common with Schmidt Cameras and similars. Here is one from Vega on my 250mm F/1.65  Schmidt camera.    Tom

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  • 49 Vega Tom's Super-Schmidt 1st light.jpg

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#5 TOMDEY

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Posted 22 June 2021 - 01:07 PM

Thanks.  That's what I guessed.  But, why don't they remove them?  That seems fairly simple.  

 

For newbs starting out, who have no idea what nebula are where, they kind of look like a type of nebula.

It's just not worth the effort. These data bases comprise thousands of images. Prettying them up is not desired or recommended, because the images are used for research projects. Processing diminishes the base information content so can compromise the intent.    Tom


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#6 Ayaan Hashim

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Posted 11 July 2021 - 11:05 PM

Even Stellarium web has these artefacts in places.




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