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KAF-8300 microlens diffraction

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#1 Phil Hosey

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Posted 17 November 2015 - 06:45 PM

is really starting to annoy me.  I don't mind spikes on my stars when I'm using a scope that has a spider, but with a refractor I want to see round stars.  Sadly there isn't much to be done except to either use a scope with a spider to cover it up or switch to a camera with a different sensor.  When I look at my own images, all I see are stars with stubby little spikes on them.  I envy those of you who can overlook minor annoyances like this.  



#2 Raginar

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Posted 17 November 2015 - 07:48 PM

Learned something new, I had no idea that's what caused it.  I agree, completely annoying.



#3 jdupton

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Posted 17 November 2015 - 07:57 PM

Phil,

 

   This is interesting. I had never noticed the effect before. I don't have a KAF-8300 camera but have looked closely at and processed images from one. I guess I just overlooked the short diffraction effects.

 

   Does anyone know why the KAF-8300 sensor shows diffraction from the micro-lenses compared to other cameras? I have a Sony ICX-694M based camera and just examined some of my images. I see no clear hint of such diffraction even though the Sony also uses micro-lenses.

 

   Do other sensors show this effect? I'll have to cruise AstroBin looking at other KAF-8300 images. Is it possible that the diffraction comes from some other source? (I'm thinking something like encroachment from a square / rectangular aperture somewhere in the camera body.(?))

 

 

John



#4 Phil Hosey

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Posted 17 November 2015 - 08:04 PM

John,

I've owned 3 different KAF-8300 cameras and they all exhibited this diffraction issue.  It's something a lot of folks just live with and I bet most owners aren't bothered by it.  I'm trying very hard not to let it get to me because everything else about the camera is good.  


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#5 ccs_hello

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Posted 17 November 2015 - 08:06 PM

Phil,

 

A picture could help.

 

individual microlen sits on top of each and every "individual" pixel for one purpose:

concentrate light to let incoming photons to fall only onto the active region of the pixel (to avoid wasted photons".

 

Microlens-based image sensor design is used almost in 100% of the modern sensors thus your observation might be from different sources.

 

Clear Skies!

 

ccs_hello



#6 WesC

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Posted 17 November 2015 - 08:14 PM

Nope its from the mircolenses... I've had it confirmed by QSI concerning my 683. I have them too... oh well. Its a great camera, I can live with it.


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#7 Phil Hosey

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Posted 17 November 2015 - 08:36 PM

Here is an example.

Attached Thumbnails

  • 8300 microlens diffraction.jpg

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#8 rflinn68

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Posted 17 November 2015 - 08:37 PM

Its worse when undersampled. Its really bad when I use my Star71, but I dont even notice them with my RC. Its not because the spikes from the spiders cover them up either. Anis would see 8 spikes with his Epsilon, depending on how the scope was oriented.

 

EDIT: Thats not too bad, about like what I see with my 107mm. You should see the stars with my Star71 and the 8300....all the little stars have spikes.  :crazy:


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#9 Madratter

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Posted 17 November 2015 - 08:43 PM

Personally, I like spikes so it just doesn't bother me.

#10 Phil Hosey

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Posted 17 November 2015 - 08:45 PM

Personally, I like spikes so it just doesn't bother me.

 

I'm OK with it at 1:1, but when downsampled they look like diamonds instead of being round.


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#11 Jon Rista

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Posted 17 November 2015 - 11:07 PM

Phil, have you tried drizzling your images? There is another thread on that topic, and one of the benefits of drizzling (even with 1x sampling) is better star profiles. Might help with the diamond stars.



#12 kraegar

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Posted 18 November 2015 - 09:24 AM

I was just noticing that my images with my new 8300 & star 71 have diffraction spikes on the stars, and was puzzled at why.  Thanks for posting this!

 

Unsure how I feel about them at this point, but in general I kind of like diffraction spikes personally, so I'll have to see how I feel about them as time goes on.  (It does help cover up the ugly star shapes from the Star 71 a little, too, though I plan on an aperture mask to help with that)



#13 Raginar

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Posted 18 November 2015 - 09:40 AM

Phil, have you tried drizzling your images? There is another thread on that topic, and one of the benefits of drizzling (even with 1x sampling) is better star profiles. Might help with the diamond stars.

 

Jon, it doesn't... unfortunately it just makes it more pronounced.  Most of my recent pictures are drizzled and it's really apparent.




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