Construction of the geodesic parabolic dish developed by JA6XKQ and 1.42Ghz cantenna

For the introduction of the design, please read this article [1] written by JA6XKQ. For those who are interested in the details of the derivation and surface accuracy of the structure, you can refer to [2]. Another important thing is the supporting structures such as adding supporting rods behind the dish or additional inner meshes to prevent the heavy feed from deforming the structure. See [3] and [4]. Please refer to the excel sheet from JA6XKQ's website at [5] to obtain the specific dimensions.

This is a 1.4m f/D 0.345 dish. Three L shape aluminium bar as supporting structure is attached to a stainless steel bowl. The same material is used for the feed supports and the reflector is made from galvanized wire mesh. This picture is taken months ago and the mesh is now covered with rust, I plan to apply rust converter to the surface and spray paint at the end. An alternative is to use stainless steel mesh at the beginning, but the cost will be high.

Cantenna's diameter: 14.5cm, length: 18cm, probe's distance from the back (1/3 of the length): 6cm, probe's length: I started with 0.25*λ, and it is trimmed until a good SWR is obtained with a NanoVNA. These dimensions are based off from the design from Figure 3 at [6]. If you want to determine the diameter based on your desired edge taper, you can see page 3 at [7]. To compute the dimensions of the cantenna and a choke ring, refer to the excel sheet from SETI League at [8].

A N type female connector is used to attach the copper probe. No soldering needed as there's a hole where the probe can be slid in tightly. 

References:

[1]http://www.terra.dti.ne.jp/~takeyasu/Geodesic_Parabola_Antenna_2_1.pdf

[2]https://f4buc.pagesperso-orange.fr/parabole_geodesique2.htm

[3]http://www.terra.dti.ne.jp/~takeyasu/PhotoGallery.html#new_photo

[4]https://www.youtube.com/watch?v=od2SEhq8DR4&t=11s

[5]http://www.terra.dti.ne.jp/~takeyasu/

[6]https://www.semanticscholar.org/paper/A-compact-radio-telescope-for-the-21cm-line%3B-za-21-Saje-Vidmar/e5baaf7450e0aea72e7926e1bdd75d3175f23424

[7]http://www.w1ghz.org/antbook/chap6-3.pdf

[8]http://www.setileague.org/hardware/feedchok.htm

Hydrogen Line project with 1.4m parabolic dish, Nooelec H1 LNA and RTLSDR

The 21cm hydrogen line is a spectral line produced by atomic hydrogen. Due to the abundance of hydrogen atoms and the nature of radio waves to penetrate dust clouds in our galaxy, we can study the milky way by observing the doppler-shifted spectral line. Spectra attached below are the result of multiple gaussian curves and the corresponding radial velocity of the individual peaks are then used to construct the structure and rotation curve of the milky way.

Self built 1.4m parabolic dish (geodesic dish developed by JA6XKQ http://www.terra.dti.ne.jp/~takeyasu/...) mounted on an equatorial mount used for astrophotography.

Spectra along the plane of our galaxy from galactic longitude 0 to 360 degrees at latitude 0 degrees. Radial velocities are corrected to the local standard of rest (LSR). Individual spectrum is multiplied by a constant obtained from the calibration using the S7 region's peak brightness temperature value from the LAB survey, at https://www.astro.uni-bonn.de/hisurvey/euhou/LABprofile/

Spectrum with multiple gaussian curve fitted.

Hydrogen line map from declination -60 to 60 degrees. Hydrogen column density is calculated by integrating the area under the spectrum from radial velocity -150km/s to 150km/s and times 1.82x10^18, given at https://www.cv.nrao.edu/~sransom/web/Ch7.html

Milky way structure. Data seemed to only match with the Perseus and Carina-Sagittarius arms. Most of the points are in between the Perseus and Norma arm, this is probably due to unresolved peaks in the spectrum from smaller radio telescope. Parameters for the spirals arm plot can be found on page 7 at https://iopscience.iop.org/article/10.1086/501516/pdf

Lastly the rotation curve fitted with a logarithmic curve. The rotation speed is obtained by choosing the most red-shifted and blue-shifted radial velocities in the spectra obtained from Quadrant I and IV respectively. The rotation speed are lower compared to the published data from Clemens (1985) attached, because the most red and blue-shifted peaks are often weak and difficult to detect with good SNR and hence the chosen peaks will be not be the maximum and minimum radial velocities. But the general trend can be seen clearly in the graph, a flat curve as you go further away from the center of milky way, suggesting that something is giving them extra speed and most of the mass might not be concentrated in the center. 

Rotation speed against radius figure from Clemens (1985), Ap. J. 295, 422.

Shout out to Society of Amateur Radio Astronomers (SARA) for funding this project!

Jupiter

Right dot is Europa.

Equipment: Skywatcher 150/750, ASI120MC, 2x Barlow, EQ3 Pro
Software: AutoStakkert, Registax, PS

Fraunhofer lines

Calibrated using F line (hydrogen beta) and E1 line (iron) on Rspec. Spectrum and graph are then put together on PS, approximately matching the dips in the graph with the dark lines on the spectrum. Taken with 1350l/mm DVD grating and D5300.

High pressure sodium lamp spectra

 

Spectra of high pressure sodium lamp as it warms up, showing the collision broadening and self reversal effect due to the absorption by the cooler sodium in the outer layers. Shot using DIY spectroscope, 1350l/mm DVD grating and DSLR. Cropped to the same size in PIPP and calibrated on Rspec.

Black Eye Galaxy

Using a black and white version this time to hide away the color gradients possibly caused by light leaking into primary mirrors, nevertheless I should pay more attention to the inverse vignetting since I started imaging, as the problem worsens every time when I pushed the image harder.

Equipment: Skywatcher 150/750, Nikon D5300, EQ3 Pro

Settings: 4hrs with 60s, 30s, 15s

Software: DSS, PS

Sirius B

Couldn't resolve it visually with 10mm plossl and 2x Barlow at around 8.30pm, perhaps only when it transits. Sirius B is clearly discernible in a 1 second frame as it gets higher.

The stacked image was heavily stretched in PS to reveal the faint background stars, to correct for the offset in position angle by rotating the image. Eventually, Sirius B is measured to be 64.5 degrees from north approximately, which is a 1.8 degree offset from 66.3 degrees obtained from Skysafari. The distance from Sirius A to Sirius B is 13" from the image, compared to 11.2", so about 3.5 pixels off.

Equipment: Skywatcher 150/750, ASI120MC, 2x Barlow, EQ3 Pro
Settings: 300x1s
Software: Registax, PS

Mars Opposition

South up. Didn't wait till it reaches the meridian at 1am due to the thick clouds.

Equipment: Skywatcher 150/750, ASI120MC, 2x Barlow, EQ3 Pro

Software: AutoStakkert, Registax, PS

Milky way at KKB

A standard portrait of a person shining a flashlight directly into the starry skies is prevalent on social media and by doing so creates unnecessary light pollution to the dark site, thus ruining long exposures image by astrophotographers and pairs of already dark adapted, unaided eyes.

This image was unfortunately taken under such occasion. It really isn't a big deal when I thought that a new picture can be shot in the next few hours of clear skies. But due to the rapidly changing weather in Malaysia, clouds rolled in less than 30 minutes, followed by hours of cloud gazing and waiting...

Equipment: Nikon D5300, 18-55mm kit lens, EQ3 Pro
Settings: 18mm, F3.5, ISO400, 180s + 60s exposure
Software: DeepSkyStacker, PS

Color Moon

The various range of colors displayed in the picture are intentionally amplified during post-processing to clearly show the mineral composition of our Moon. The blue color region, called the Mare Tranquillitatis, is rich in titanium and it is also the landing site of Apollo 11.

Equipment: Skywatcher 150/750, Nikon D5300, EQ3 Pro

Settings: 1/1250s, ISO640

Software: Registax, PS

Saturn

Equipment: Skywatcher 150/750, ASI120MC, 2x Barlow, EQ3 Pro
Software: AutoStakkert, Registax, PS

Comet C/2020 F8 (SWAN)

Comet C/2020 F8 (SWAN) was discovered on April 11, 2020 in images taken by NASA's Solar and Heliospheric Observatory. This was my first attempt at photographing a comet, it was quite a challenging task for me as the comet wasn't visible in the finder scope under the light polluted skies together with a low altitude position (about 20 degrees). Fortunately, I managed to get 17 minutes total integration time before the skies got too bright. The tail is barely visible in the image.

5 days later. This, I think, will be my last glimpse of the comet.

Equipment: Skywatcher 150/750, Nikon D5300, EQ3 Pro

Settings: 20s exposure, ISO400

Software: DSS, PS

Shooting ISS

 

Manually tracked and got it in 14 images out of 1808. Images in actual sequence are overlayed.

Equipment: Skywatcher 150/750, ASI120MC, 2x Barlow, EQ3 Pro
Settings: 1.5ms
Software: Firecapture, PS

The Sombrero galaxy

Due to its resemblance to a wide brimmed hat, we call it Sombrero Galaxy. It is a popular deep sky object to be photographed under light polluted skies because of its high surface brightness. Notice there is a faint blob on the lower right, PGC 962963 it has a visual magnitude of +16.65 at 1.4 billion light years away from us!

Equipment: Skywatcher 150/750, Nikon D5300, EQ3 Pro

Settings: 450x20s, ISO400

Software: DSS, PS

Great Orion Nebula

Acquired 90 minutes of data before 2019 ends. This target was also taken around the same time last year but with 40 minutes integration time only, giving me a hard time to bring out the fainter nebulosity. This time, with twice amount of data and good sky condition, I hope I didn't push the image too hard.

Equipment: Skywatcher 150/750, Nikon D5300, EQ3 Pro

Settings: 180x30s

Software: DSS, APP, PS

Partial Solar Eclipse 2019

Very cloudy on that day as usual. Was lucky to get a decent glimpse of this close to annular eclipsed sun. Shot with ASI120MC and 60280 guide scope.

M27 Dumbbell nebula

Equipment: Skywatcher 150/750, Nikon D5300, EQ3 Pro
Settings: 360x30s
Software: DSS, APP, PS

First deep sky M42

Only 40 minutes of data taken under Bortle 8 skies.

Equipment: Skywatcher 150/750, Nikon D5300, EQ3 Pro

Settings: 60x40s, 20 darks and bias frames

Software: DSS, Pixinsight

Perseids and Star trails

 

Can you spot which are the meteors?  I spotted a bright orange meteor streaking across the northern sky that day, it lasted about 2 seconds and left a trail which vanished very quickly in the sky. Taken with ASI120MC+All sky camera, processed in StarStax.