It is a common problem with H-alpha solar imaging with CMOS cameras that if a Barlow is introduced into the optical train Newton's rings frequently become evident in the image where they were not present if a Barlow has not been used. It has been found that a tilting mechanism can eliminate Newton's rings by using a correct tilt angle.
Click on an image to get a closer view
The equipment used
A Coronado Solarmax II, 60, BF15 H-alpha scope mounted on a Celestron AVX mount. A ZWO tilting mechanism was used to attach the SV305M Pro camera to a x2 Barlow lens which was then placed in the diagonal.
AstroDMx Capture for Linux was used to capture a 2500-frame SER file of the Sun.
Screenshot of AstroDMx Capture capturing the SER file data
The SER file was registered, stacked and wavelet processed in Registax 6 and post processed in the Gimp 2.10
Below are four process renderings of the active regions imaged AR2993, AR2994 and AR2995 revealing details of the surface structure.
Normal monochrome image
Colourised normal image
Monochrome half-negative image
Colourised half-negative image
It can be seen that considerable detail of the sunspot active regions and filaments has been captured. The various renderings of the image can be used to explore and examine the various details of the structures.
The SV305M Pro USB 3.0, CMOS camera performed well in combination with the tilting mechanism and the H-alpha scope to produce a detailed image without Newton's rings.
AstroDMx Capture can be downloaded HERE.
AstroDMx Capture is available for Windows, macOS, Linux including Raspberry Pi OS and ChromeOS.
