JUPITER-SATURN CONJUNCTION 2020

The Conjunction day, 2020/12/21, was unfortunately cloudy. But during the next day, even if cloudy, the clouds opened enough to image the event. The planets were very low, just about 13º. But it was still a joy to see and image.

Jupiter-Saturn Conjunction on 2020/12/21

It will not happen again in many years to come. Next 2020/12/21, Jupiter and Saturn will be as close as 0.1 degrees apart.

Here is a calculation of the timing of the event. The minima will be at around 18:00 UTC.

Home-made White-light Filter with Baader Film

Made a simple but effective filter for my SkyWatcher 250/1200 using a Baader Milar film.

I sandwiched the film between two plywood sheets, and added a cardboard ring to fit the OTA.

Distance Sun-Mars, Perihelion and Aphelion

MARS VISUAL SIZE 2020-2040

Mars won’t be as big in the sky as this year (2020) until 2033 (22’’) and 2035 (almost 25’’).

Note that the time-windows for a ‘good size’ are relatively narrow.

Mars Orbit & Photos

Plotted the points in Mars orbit where I took pictures of it.

My Martian Adventure

Even back in June I had no idea I would soon end up with a telescope. The summer lockdown was an opportunity to go for it and spend a good amount of time learning and enjoying the sky DSOs and Planets. Mars has been one of the 'stars'. Love it !

Earth & Mars Orbit

Just for fun I got the orbit numerical information for 2020 of the Earth and Mars from the JPL (Jet propulsion Laboratory).

Then did some processing and graphed the result in 3D with a 7-day step. The blue line/dots correspond to the Earth. Red for Mars. Green for the vector from Earth to Mars.

It is quite visually obvious that the eccentricity of the Mars orbit is much bigger (a bit over x5 in fact) than that of the Earth’s orbit.

The Eyepiece Projection Method

Here is a short description about the eyepiece projection method, including some basic telescope optics relevant to Astrophotography.

All diagrams done with powerpoint, so they are basically conceptual. Hope you find it useful.

Mars South Polar Cap Shrinking.

Since the weather continues to be cloudy, I can only play around with the images I already got.

I tried to roughly measure how quickly Mars south polar cap is reducing.

It lost around 30% in one month, from around 1,000km to 700km in diameter.

Earth-Mars Approach on 2020/09/06

On September the 6th the Earth got closest to Mars than it will get in a long time, creating a golden opportunity for the community of astrophotographers.

The closest point happened at around 14:20 UTC on Sept. 6th, with a distance of 62 million km (0.415 Astronomical Units).

Mars, Jupiter, Saturn and Uranus relative sizes on September 28

On September 28th I photographed Mars, Jupiter, Saturn and Uranus.

The below image is a combination the photos of the four planets and shows their relative sizes in the sky.

All photos were taken with a SkyWatcher 1200/250 telescope, with an eyepiece of 10 mm focal length projecting on an ASI120MM camera. The RGB filters between the eyepiece and the camera.

2,000 photos were taken for each of the R/G/B channels. As a reference, the speed was 94 FPS (frames per second) for Mars, 61 FPS for Jupiter.

Software used: FireCapture, AutoStakkert, PixInsight, RegiStax and Photoshop.

Did not need to use WinJupos to de-rotate because each channel was just around 20 to 30 seconds, i.e., max 1.5 minutes per image.

Starnet++

Being able to separate the star field from the main (typically deep-sky) object can be very useful at times, be it to make easier to process the deep-sky object, or be it for pure curiosity about the result.

Starnet++ is an amazing tool, using a neural network, to achieve exactly this.

It is remarkably easy to use and free. Kudos for the team that created it !

https://sourceforge.net/projects/starnet/

The below image depicts the process to enhance a deep-sky object.

The experiments with the eyepiece projection method continue ...

My main telescope is a Newtonian Skywatcher with a diameter of 250 mm and a primary focal length of 1,200 mm (thus, F/4.8). This is a relatively fast optical system well suited for deep sky and rather wide fields of view. For planetary imaging, you will normally want much larger basic focal lengths to achieve a narrow field of view thus allowing you to ‘zoom into’ the smaller sky objects, like the planets.

As a reference, Jupiter, the largest planet in the sky (and in our solar system), is just around 40 arc-seconds. One arc-second is only a tiny 1/3600 of a degree. The Andromeda Galaxy, at about 3 degrees in its main axis, is about 270 times the size of Jupiter, and the Moon, with 0.5 degrees or 32 arc-minutes, about 45 times the size of Jupiter. By the way, it sounds kind of shocking, but yes, the Andromeda Galaxy (M31) is about 6 times bigger in the sky than the moon. Mars is about half the size of Jupiter (not the real size, but the apparent size in the sky)

In order to get a decent image-size of, say, Jupiter, you will need to work at relatively high F numbers, like F/20, F/25 or F/30 (F = Equivalent Focal Length / Diameter). For a given optical tube (where the diameter is already fixed), the only way to increase the equivalent focal length is to add optical elements that effectively ‘stretch’ the original focal length by ‘bending’ the light rays coming from the primary mirror (or primary lens-system in a refractor). The standard method to do this is to add a “Barlow” lens system. Typical Barlows are 2x, 2.5x, 3x, 4x and even 5x. Meaning, they do the equivalent of stretching the original focal length 2 times, or 2.5 times, … The Primary (mirror or lens) + Barlow setup is the most common method when using a camera.

Another way to get magnification is to use an eyepiece (basically, a small magnification lens). The magnification achieved by the system composed by a primary mirror (or lens) and the eyepiece is simply the focal length of the primary divided by the focal length of the eyepiece. This is the standard method when looking with your eye through a telescope. But is can also be used for camera imaging.

And, of course, you can combine both, Barlow + eyepiece. Maybe not the best arrangement, as you should always try to minimize the number of elements in your optical system, specially of lenses, which inevitably introduce imperfections (even if small) in the imaging process (reduce light by reflection or absorption, color aberrations, geometric distortions …).

In any case, I have been playing with combinations of the elements to see how they compare and ‘how far’ (magnification versus image quality) I can take each setup.

Ever wondered how Jupiter looks like in the Red, Green and Blue Channels ?

Jupiter, on 2020/09/04 around 20:49 UTC.

Jupiter R, G, B & R+G+B