Observation by Peter Anderson: Comparison Out of Focus Star images

Uploaded by

Peter Anderson


Peter Anderson


2019 Dec 31 - 14:00


2020 Mar 24 - 04:57



  • 150mm F8 achromatic refractor and ED

not relevant


Brisbane Australia

Target name

Sirius and Rigel out of focus images


Comparison Out of Focus Star images

About this image

The images were taken in February 2020 using a Celestron 150mm F8 refractor  with 3X Barlow - target Sirius, and in March 2020 using a Skywatcher ED model with the same specifications and setup - target Rigel. The first set was at the request of a prospective purchaser and the second while I was setting up for the Rigel series already posted.

I have no expertise in analysing zones from out of focus star images, but it was apparent that though there is little colour in the 'in focus' ED images, a reasonable amount is displayed in these out of focus images. The two sets of images should not be critically compared for brightness and colour because there were some adjustments to brightness and contrast.

Sky conditions were only average. I would appreciate comment on what these images might reveal. 

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Martin Lewis
Martin Lewis, 2020 Mar 24 - 10:26 UTC

Hi Peter,

These are difficult to interpret because of the colour dispersion. It would be useful if you repeated with a red filter and possibly separately with a blue filter. Also try without the Barlow as even premium ones can introduce considerable correction errors.


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