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Need help analyzing my HyperStar stars

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#1 Ken_nneth

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Posted 12 January 2019 - 02:39 AM

I need some help analyzing my Hyperstar image. I sent some images to support at ZWO asking if they had any idea what was going on with my stars. The answer I got was that it was probably a HyperStar collimation and focusing problem. I think it might be a combination of coma and collimation. When I poste a topic about using StarTools to fix these awful stars I got several replays indicating that it might be something else. I would like to get more feedback on these images, so I know a little more about what I need to do when the weather again lets me use my equipment. These images are a strait “LRGB Combination”. So if you have any ideas please take some time and help me with this.

 

Top to bottom: center, top left, top right, lower left, whole image, lower right 

Attached Thumbnails

  • Center.jpg
  • Lower keft.jpg
  • Lower right.jpg
  • Upper left.jpg
  • Whole Image.jpg
  • Upper right.jpg


#2 sharkmelley

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Posted 12 January 2019 - 03:10 AM

In the first place, the centre crop clearly shows that your focus was way off.

Even with the focus off, we would expect the aberrations in the corners to be symmetrical.  But the star shapes in your corner crops have different shapes.  That clearly indicates a collimation and/or sensor tilt issue.

 

However, the first thing to check is the spacing of the sensor from the corrector - are you using the right adaptor?  If your spacing is incorrect you won't be able to achieve sharp stars right across the image field.

 

Then you need to deal with the collimation and/or sensor tilt.  This can be quite time consuming.  A sensor tilt issue can be diagnosed by rotating the camera 180 degrees.  Note that adaptors can create tilt - a tilt problem does not necessarily mean the sensor is tilted within the camera body.

 

Once you have fixed the collimation and/or sensor tilt you may still find you need to make a fine adjustment to the spacing.

 

At a focal ratio of f/2 everything must be extremely accurately adjusted.

 

Good luck!

 

By the way, the "Cats and Casses" group on Cloudy Nights is the ideal place to discuss Hyperstar issues:  https://www.cloudyni...69-cats-casses/

 

Mark


Edited by sharkmelley, 12 January 2019 - 03:21 AM.

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#3 happylimpet

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Posted 12 January 2019 - 04:40 AM

Collimation is clearly an issue (and hopefully the only one) so I'd deal with that first. Even on axis the stars are asymmetric.


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#4 OleCuss

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Posted 12 January 2019 - 09:23 AM

I agree.  Focus was clearly off a bit.

 

Collimation and/or tilt as well.




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