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It was a brightest object in the sky. Attached is the picture taken on 25th January around 6pm in Riga / Latvia, towards the south direction:

Apologies for a quality of the picture, the telescope was inside the flat and the picture was taken through the window.

unknown object

The object was visible for few hours while it was traveling from the south-east towards south-west. I observed this bright object previously on couple other days, it's the first time I pointed my tellescope in its direction.

View of the sky: https://i.sstatic.net/fRVl4.jpg

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It was a brightest object in the sky.

This already makes one think "Venus?"

At about 6 PM on 25-Jan-2019 from Riga Latvia the planet Venus was about 17 degrees above the horizon in the Southwest.

Venus is always strikingly bright when it's visible, it's apparent magnitude stays between about -3.8 and -4.8.

From in-the-sky.org's planetarium mode

Screen shot from in-the-sky.org's planetarium mode

This matches nicely to your photo out the window:

enter image description here

But what about the donut-shaped image?

Your image is way, way out of focus. The the outside of the annulus represents the diameter of the telescope's primary and the inside represents the diameter of the blockage by the secondary mirror holder. The blockage is about 45% of the radius or about 20% of the area, which seems reasonable for some telescopes. Here's a random example of a telescope with a similar blockage.

Here are some other celestial donuts to enjoy! In this case they are caused by a tiny spot of dust which is out of focus, and one is dark rather than bright, but they are other examples of how point-like objects that are out of focus show you your aperture.

celestial donut

above: from this answer, below: from this answer

celestial donut

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    $\begingroup$ I did notice that Venus was in the provided direction indeed. What threw me off is the black hole inside, which did not disappear regardless of the change of focus. Telescope blockage obstruction is the keyword that explains this peculiar shape of Venus! $\endgroup$
    – Datageek
    Commented Jan 31, 2020 at 11:25
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    $\begingroup$ @Datageek I'm sure it was quite exciting to see a celestial donut! There are some other interesting artifacts I've seen posted here, I'll leave another message for you in a few minutes... $\endgroup$
    – uhoh
    Commented Jan 31, 2020 at 11:29
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    $\begingroup$ @Datageek Here are two more donuts for you :-) What cluster of stars is this with a “dark donut” to one side? and also Did Hubble see a pair of UFOs? (Identify this artifact) $\endgroup$
    – uhoh
    Commented Jan 31, 2020 at 11:31
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    $\begingroup$ Exciting is an understatement, we thought the alien invasion is imminent! :) Thanks very much @uhoh, I will read more about it to try to understand this effect better and see if there is any way to avoid it. $\endgroup$
    – Datageek
    Commented Jan 31, 2020 at 11:38
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    $\begingroup$ @Datageek there are many questions in this site tagged photography but feel free to ask a new and specific "How can I focus?" question about your particular telescope and camera. There are several helpful people here who can answer astrophotography questions. $\endgroup$
    – uhoh
    Commented Jan 31, 2020 at 11:41

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