Radio Astronomy Station of Humain (B)

Interferometers - Credit Pascal Hilkens

The date of september 9th was already marked for a long time. The radio astronomy station of Humain in Belgium will open its doors to the public for the first time. Together with my collegue Walter we left early in the morning to visit this once in a life time opportunity.  The weather was perfect with a clear sky to walk along the two north-south and east-west axes of the old interferometer. 

This radio astronomy station was founded in 1953 by the Royal Observatory of Belgium to house the very first Belgian radio telescopes dedicated to observing the Sun. In the 1960s, a solar interferometer of 44 radio telescopes was constructed and operated up until 2001. Today, the station continues to host radio and optical experiments to observe the sky, the Sun, the Earth’s space environment and its atmosphere.

Credit Pascal Hilkens

After a quick snack we walked into a demo with the Solar Explorer or Sol'ex. This was a nice surprise as we didn't expect that the Royal Observatorium would own an amateur Sol'Ex instrument. This gave us the chance to ask in depth questions to Sabrina Bechet from the Royal Observatory. She gave some tips on the position of the instrument with the mount.

From Left to Right: Pascal, Sabrina Bechet (Royal Observatory) and Walter

First Image with Sol'Ex

Today I made the first picture of the Sun in H-alpha with my new Sol'Ex.

Hardware Setting: TS/APO60 f/6 with ASI290MM

Software Setting : 130fps, 7,55ms, Gain  0, Mono 16

Capture area : 1936 x 114 binning 1x1

Temperature Camera : 48°C

Filter: Hoya ND16

Software: SharpCap4, Inti, CS4, Samsung SSD

My picture of Comet C/2022 E3 (ZTF) published in Heelal

My picture of Comet C/2022 E3 (ZTF) of January 21, 2023 is published in astro magazine Heelal (Jaargang 68, number 9, September 2023, page 20). It's my third picture of a comet that made it for publication. Previous comets were Neowise C/2020 F3 and C/2017 K2 (Panstarrs). 

See also my blog : Reprocessing Comet C/2022 E3 (ZTF) with antitail

See also my blog : Comet Comet C/2022 E3 (ZTF) with three tails

See also my blog : Comet C/2022 E3 (ZTF)

Saturn @opposition August 27, 2023

There were a few moments with no clouds which I used to iamge Saturn. Saturn was in opposition and thus ideal circumstances; Unfortunately both seeing and transparancy was fair. and even poor.

Polarallignment was done using SharpCap4 with ASI290MM on guiding scope 50x240. Imaging with TAL200K @f/22 with ADC, Barlow x2 and ASI224MC camera with UV/IR blocker. 

Software: SharpCap4, AstroSurface U4 and CS4

Lights:  34.8ms and 28.36 fps, total of 3000 frames

White Balans : B85, R55

Saturn August 22, 2023

 

Another image from Saturn on August 22, 2023. Stacking was done using Astrosurface U4, keeping 12,5% of the 3000 frames. Further editing was done with Astrosurface and CS4.
The white balanced is changed to get out more colours. 

Details below and above the rings are clearly visible. 

Exposure time was 22,6 ms or 44 fps with a total of 3000 frames.

Effective focal length and best sampling factor

My Helios collegue, Walter, asked me about the effective focal length of my set up when imaging Saturn (august 22, 2023).

So here it is:

I uploaded my picture of  Saturn in WinJupos. Using the measurement - adjustment tab it's possible to obtain the diameter of the planetary disk in pixels (Di). The apparent diameter of the planet in arc seconds  (Dp) is provided by ephemerides tab. 

Sampling S = Dp/Di = 19/128.8 = 0.1475 arc seconds per pixel

The image sampling is equal to :

S = 206 P / F  (P = pixelsize of the camera and F = effective focal length in mm)

So F = 206 P / S = 206 3.75 / 0.1475 = 5237 or F/D = 5237/200 = 26.18 

Conclusion :

My set up with barlow x2, ADC and ASI224MC (3.75 micron) on TAL200K f/8.5 has an effective focal length of f/26.18. This means that my magnification is 26.18/8.5 = 3.05

Based on this f/26.18 and a Dawes resolution power (RP=1.02 wavelenght/diameter telescope) of 0.5838 it possible to measure the sampling factor k (k = RP / S).

k = RP / S = 0.5838 / 0.1475 = 3.95. 

Conclusion :

The Nyquist-Shannon theorem requires a k>2 but in practice a sampling factor of  3 to 3.5 is recommended according to Christian Viladrich - Solar Astronomy page 300 - Planetary Astronomy page 80). Increasing the sampling factor k beyond this would not bring a significant gain. Wirh my set up of 3.95 I will investigate how to reduce this to a value of 3 to 3.5. 

For information: the formule on page 81 of Planetary Astronomy should read F =206 Tp Di/Dp and not using factor 260.

Saturn reworked picture adjusting white balans

My previous reworked pictures of Saturn had some issues with colour setting. Again I reworked my pictures using AstroSurface U4 for stacking and sharpening and CS4 for adjusting white balans (RGB adjustment).

The result is more bright and the image has more colours.