Andrew Thornett

Reducing blue halos around stars on my M27 image

I received a criticism that there were too excessive blue/purple halos around the stars in my M27 image.

It has taken me ages to come up with a solution but here it is.

Starting with my previously processed image:

(i) Load image into Photoshop CS6.

(ii) Duplicate layer.

(iii) Add mask to duplicate layer. Use brush (137 pixel, airbrush soft round 50% flow) to cover nebula in mask on duplicate layer.

(iv) De-select bottom layer (without mask) so not visible.

(v) Go to duplicate layer (not mask) and open levels and raise lower limit on blue level until blue halo disappears.

(vi) Re-select bottom layer so visible again.

Voila! Blues gone but nebula still original colour!


My best ever photographs of the sun 26/7/2020 – sunspot in hydrogen alpha, calcium H line, sodium line

The sun came out after my last photo and I have had a ball! At last – I feel like I am getting somewhere with my astrophotos of the solar surface.

It turns out that it is all about the flats – get them right and the picture is magic – get them wrong and it isn’t – so I kept taking new flats in FireCapture until picture on screen lost all those Newtonian rings!

…..From photos below, you can tell I did not get it quite right with the sodium filter today!


Sun 260720 Quark Hydrogen filter processed 260720@1138 74 of 194 frames cropped PI deconvolusion PS Astroflat Pro smart sharpen colourized:

Sun Quark Calcium filter 260720 processed 260720@1323 (100 of 1924 frames) cropped PI deconvolusion PS processed:

Quark Sodium filter Processed 260720@1209 cropped PI deconvolusion PS Astroflat Pro sharpen colourized:

Sunspot 26/7/2020 @ 09:30, Lichfield

After a long hiatus with no sunspots, there is one at last.

Battling against a lot of cloud, I managed to get a few seconds of precious video in (about the only) clear spot there was and processed it to get the image below.

The photo suggests that my Quark is not quite flat to the image plain – I am not sure if this is the focuser or the Quark etalon itself – I do have a tilt adapter but today was set to 0 degrees.

Can anyone tell me which from the photo?

  • ZWO ASI 174 MM camera
  • Best 183 frames of 960
  • Sky Watcher Equinox Pro 100mm OTA
  • HEQ5 Pro mount
  • Stacked in AS!3
  • Deconvolusion in PixInsight
  • Final processing in Photoshop CS6


Calcium H image of the solar surface from 25/6/2020, processed 23/7/2020

ZWO ASI 174MM camera

  • Sky Watcher Equinox Pro 100mm OTA
  • Daystar Quark Calcium H filter
  • 1.9GB video file
  • Best 89 frames stackded in AS3
  • Processed in Photoshop CS6
  • Lichfield


I then ran the above image through PixInisght’s deconvolusion routine to produce following. Which do you prefer? Let me know!