Yuri Beletsky

This morning, I captured another image of Comet C/2023 A3 (Tsuchinshan-ATLAS) from the @LCOAstro site in the Atacama Desert, Chile 🇨🇱✨😱. The view was absolutely stunning !!! The comet is clearly visible visually. My gear: Nikon D810a camera with a 135mm lens. Exposure: 20 x 30 seconds. #Comet #Astronomy #Atacama #chile #TsuchinshanATLAS #cometa #CometC2023A3 #Tsuchinshan #C2023A3 #FollowTheComet

That’s why the Bortle scale should be used with caution when judging night-sky quality. In professional astronomy, modest light pollution near the horizon is usually tolerable because we rarely observe at such low elevations. A site may therefore receive a poorer Bortle rating, yet still be excellent for serious astronomical work. Context matters.

Seeing some takes on Bortle class sky rating that I think are good for some discussion. A Bortle class refers to the whole sky. Not part of the sky. The sky is not Bortle class 2 overhead and Bortle class 4 or 5 near the horizon. Each class has a description valid for the entire sky. For example, Bortle class 3: "Some indication of light pollution is evident along the horizon. Clouds may appear faintly illuminated in the brightest parts of the sky near the horizon, but are dark overhead. The Milky way still appears complex …" And it then goes on to other indicators and criteria. This is valid for the entire sky. Clouds - dark overhead, may be faintly illuminated near the horizon. The Milky Way still appears complex. If there is uncertainty, perhaps some indicators from a class above or below are present (and this may depend on the atmosphere - how much humidity and aerosols there are), it could be Bortle class 2-3 or 3-4. The better rating under good conditions, the worse rating under poor conditions. But not class 2 overhead and class 4 or 5 near the horizon. The Bortle dark sky scale has some elements that depend on factors other than light pollution. Airglow is in my experience visible *far more often* than the scale indicates, especially around solar maximum. Bright airglow can be mistaken for high clouds illuminated by light pollution. It can be bright enough to brighten the sky tremendously. My Bortle class 3 location goes to 21.5-21.6 mpsas during solar minimum, but even on very transparent, clear nights during solar maximum it can reach just 20.9-21.0. The other factor is visual limiting magnitude. I have observed meteors together with a number of observers and groups over the years and under the same sky the limiting magnitude can vary tremendously between observers, up to a full magnitude. It is not just myopia or astigmatism, some people have sharp eyesight but apparently less sensitive eyes. Or there may be different thresholds to positive detection: one person may be convinced they see a star if they can hold it constantly with direct or averted vision, an experienced observer may be confident even if they see the star only 10% of the time (or in the case of Stephen James O'Meara only a few % of the time). Photo: Bortle class 3 sky at Šebreljski vrh (Šebrelje Peak), Slovenia during an average summer night and the corresponding sky brightness map from Lightpollutionmap. The LP at 3 to 6 o'clock is from way SW in Italy. Thanks, Italy ...

@astrophoto1976 @JAtanackov @GeminiObs It has indeed increased over the past decade or so, however the observing conditions are still very good. In professional astronomy we rarely observe below 45 degrees elevation. Visually, from that location, you certainly see the distant city glow.

@YBeletsky @JAtanackov @GeminiObs Would you say the light pollution has increased around those observatories? Would you say that Bortle 1 visual conditions are still possible from there?

Oh wow. I guess the observatories in Chile don't have Bortle class 1 skies anymore? Those clouds are baking in light pollution.

Bortle scale is subjective. It integrates the whole visual experience, such as horizon glow, extended-object contrast, color perception. Therefore a site with zenith SQM of 21.8 (typical for an excellent sky) can still feel like Bortle 4 if there are bright city domes on the horizon.

@JAtanackov @YBeletsky @GeminiObs your thoughts on this?

@ericpare Congratulations !! 🎈🎉😃

We've been quiet about this, but we signed a book deal a while ago, and we've been working on this for over a year. This is an official announcement 💕 lightpaintingbooks.com Preorders: join my substack (from the link above)

@Haru_koala Great capture 👍😃

今年最後の天の川アーチをバイロンベイの滝の上から撮ってきました。黄道光がさそり座と天の川中心部を照らして幻想的でした。この形のアーチと黄道光のコラボは天の川シーズン終わりの今だけしか撮られない期間限定。ちなみに、アーチの外にひっそりとスワン彗星が写っています。

@christnperrier Yes, indeed 😃 Thanks a lot !

@YBeletsky Las Campanas Du Pont, OGLE and other telescopes (from Magellan tel I guess) 👏👏 So impressive to get the ZL with a smartphone ! I have seen it several times with the naked eye. As you say, we now have extraordinary capabilities!

The Zodiacal light above the Pacific Ocean. I obtained this image with my Samsung S25 Ultra smartphone from the Atacama Desert in Chile 🇨🇱 The amount of details captured by the phone is truly impressive, showing how far smartphone astrophotography has come. We are definitely living in the new era ! 🤩 @SamsungMobile @SamsungLatin

@texasranger_72 The new era of smartphone astrophotography

@YBeletsky Very nice. New era of what?

@skymango_x Thanks a lot 👍 I use standard phone app

@YBeletsky That's a lovely grab! 👏🏻👏🏻 I often use a Samsung S24 ultra - which produces incredible images. Did you use the standard phone app or something else?

@gameofchains Thank you 👍

@YBeletsky Impressive

I captured this image of the Milky Way's galactic core using my Samsung S25 Ultra smartphone in Chile's Atacama Desert 😃 That's right, it's smartphone astrophotography we are talking about here ! If you ask me why to use a smartphone? Well, challenge is everything and I am curious indeed & We are definitely living in the new era ! ✨

@VicKDurandPM I was taking images in RAW format. It’s a different thing from that Moon situation from years ago.

@StewarrMark Yes, I did 👍

@YBeletsky These looks super sharp for 30 seconds did you put the phone on a star tracker?

@hiheal Thanks a lot 😃

@YBeletsky Super impressive!

@Cathrinmachin Thanks so much 🙏😊

@YBeletsky Damn wow

@spce_enthusiast Yes, I stacked a sequence of RAW images (30 sec each) taken in Pro mode 👍

@YBeletsky Did you stack any images or did you just use the default astrophotography mode? Because if it's the latter, that's extremely impressive! Best I could do with astrophotography mode (on an S22) is this image, under rural skies (ofc nowhere near the sky quality of Atacama)

@AwareSolar I took a sequence of 30 sec exposures in RAW format using Pro mode 👍

@YBeletsky Great shot what setting was used . I'd like try tonight here on big

@BakryBaso Many thanks 🙏 Looks good, great capture 😃

@YBeletsky Great shot, Yuri! especially impressive considering it was taken with a phone! Here is an image I took under a bortle ~3.5 sky with S22 Ultra 😁

@tatramtn That’s quite impressive !

@YBeletsky I got these with an S24 Ultra in a relatively dark sky, maybe Bortle 3 or so. Pleiades rising over the trees. Two shots of the Milky Way, one with a tiny Andromeda Galaxy visible.

@Tameemi Thanks a lot 🙏😃 Yes, it’s Bortle 1 sky. But modern smartphones are also quite capable of capturing images in low light conditions.

@YBeletsky Absolutely stunning capture, Yuri! The level of detail here shows what’s possible only under extremely dark skies, probably close to Bortle 0! Incredible to see smartphone astrophotography reaching this level. Truly inspiring work! 📱

@luanaTakarai You should definitely try 😃👍