It’s a commonly-known fact that the planet Venus is visible to the naked eye during daylight, if you know exactly where to look. Fewer people know that Sirius, although 13x fainter than Venus, is visible as well! Sirius is the brightest star in the sky besides the Sun, and while it’s a challenge to see it with the naked eye with the Sun up, it’s by no means impossible.
I was recently able to hold Sirius in view for 47 minutes after the Sun rose, while looking through cirrus clouds! Scroll down to read a transcript of my observation, or read on for tips to help you spot Sirius in the daytime for yourself.
Tips for daylight observing
When it comes to seeing objects during the daytime, it’s absolutely essential that you know exactly where to look. Knowing where to look makes all of the difference, as an object will usually appear totally invisible until you first “see” it, at which point it might turn out to be quite easy indeed. (Have you ever stood at a starparty and watched a group of people pointing out the planets as it just begins to get dark? “Oh, there’s Jupiter!” “Where?” “Right there!” “I don’t see it…” “Right above that tree!” “Oh!”)
When it comes to seeing Sirius in the daylight, it’s easiest when you start before dawn, so you can keep your eyes on it from the time it’s still easily visible. Keep it lined up with a tree or other foreground object, so that as the sky brightens, you know exactly where to look should you lose it. If you’re trying to see an object before sunset, instead of sunrise, it helps a lot to use binoculars to line up the object with a tree or landmark before trying in earnest to see it with the naked eye.
Circumstances of my observation
I made the following observation from my Arkansas observing site on the morning of October 22nd. It was the first (and so far, only) time I’ve tried to see Sirius during the daytime.
Local sunrise was at ~07:26am according to the NOAO computational definition, which is what I use to keep my observations standard. (It is, however, interesting to note that due to observing from a mountain at an altitude of 2180ft above sea level, the apparent sunrise would have been noticeably earlier: SkyTools estimates 07:21am.)
The transparency during the previous night had been excellent, but unfortunately, cirrus clouds began to form that morning, and covered Sirius from my point of view. Thankfully, I was still able to hold it for a fairly long time, even through the clouds.
I had time.gov open on my phone (and later my mom’s phone, after mine died) to use as an accurate source of time, since I was unsure how far off my recorder’s timestamps might be. As it turns out, my voice recorder is slow by 33 seconds. The times below are corrected for the discrepancy.
7:10:44 am – Ok, I just picked up Sirius, it’s easily visible. I’m going to go back upstairs actually and watch the sunset for a–err sunrise for a few more minutes because it’s… incredible. If I stand under these low hanging branches on the tree with the spiky leaves on the left, then it’s right above that tall tree, so that’ll help me find it when I come back out. [crunching gravel noises] Here I go.
7:18:51 am – Alright, I got Sirius, it’s still easy to see with direct vision. There are some light, patchy, thin clouds and contrails… um, one of which is actually about to drift over Sirius. [quietly] Is how it is. Let’s see if it’s still visible when the contrail goes over it. It’s not the thickest, not the thinnest. [long pause] Yeah, Sirius is still holdable with direct vision even behind the contrail, so that’s good. It’s holdable enough that I’m gonna leave my spot, see if I can get a better view of the fog in the valley and the sunset.
7:21:30 am – [quickly] Sirius is still easily visible, so I’m dashing in to get more cold gear, so I’m prepared to stay there for a while.
7:23:35 am – Ok, had a moment of “oh no! it went away while I was gone!” but no, it’s still holdable with direct vision. It, uh, went behind a tree from the perspective of my spot I use to find it. So it looks like I’m gonna be gradually scooting out into the yard here as Sirius sets. [slight pause] Uh, there’s a couple- I mean there’s, there’s a little bit of light clouds in that area of sky, kind of just a thin, gauzy veil over Sirius- but hey, do the best with what I’ve got.
7:26:17 am – There are little, insignificant notches [Loud phone notification: Scott texting] –in my vision of Sirius. Um, it’s still, it’s still would say it’s 100% visible with direct vision. It’s just that the entire time pretty much that I’ve been tracking it since it got hard, every now and then it seems to flicker, but I never actually lose it. Just a note.
7:29:50 am – Sirius is getting faint, and it’s starting to get to the point where I need to know where to look- y’know, I lose it when I move my eye off- but, when I can have my eye on it, it’s 100% of the time with direct vision.
7:30:29 am – Oh, the sun’s starting to touch the top of the tree! As of the time of me saying the seconds number, time.gov reads: seven, thirty, thirtyeight.
7:31:48 am – Yeuup, it’s um, still Sirius! [chuckles]
7:32:43 am – Some light clouds passing over Sirius, as there has been. It’s interesting to note [pause] that watching it, the seeing appears bad. It’s not as though it’s getting to faint to see, it’s.. flickering like a star in bad seeing. Oh yeah, still, uh… [pause] probably 90% of the time with direct vision. If I stare too long, I get the Purkinje effect, and it goes away.
7:34:26 am – ‘Less light’ cirrus clouds passing over it, but so far it’s remained visible through the little cirrus wisps. [pause] I say cirrus.. just wispy clouds, moving pretty fast, north to south.
7:34:55 am – It does disappear behind the thicker sections. Of the clouds.
7:37:59 am – I can actually see the sun now if I turn around, so note to self: Don’t turn around.
7:38:58 am – This cirrus just keeps forming and forming, and I keep losing Sirius behind it. I see it now, but.. it’s through a cirrus cloud, and it’s not great. Hope this doesn’t ruin my sighting. When I do see it, it seems like it’s still on the mostly-visible-with-direct-vision side.
7:39:38 am – Ironically, the clouds seem to make it almost holdable? I can hold it, the entire time it’s visible through clouds. When it’s NOT visible through clouds, when there’s a clear patch, it seems to come more in and out. So I wonder if that’s my internal noise reduction acting on it.
7:40:24 am – I just got a cloudless patch for a few seconds, and it stayed steadily visible. So.
7:41:48 am – I’m staring straight up at the blue sky to reset my eyes from that tree afterimage I’m developed strongly. Also, the clouds are over Sirius most of the time now, but it’s still easily visible direct vision 100% of the time when there’s a break in the clouds. I just got a several second break in which I could confirm that. Uh, the time, as of me saying the seconds mark, is seven, fortytwo, seventeen.
7:42:46 am – Sirius is still visible through some of the thin clouds, so I don’t mean to give the impression it’s only the gaps.
7:44:09 am – Just had an alarming moment of “AAA! thin crescent moon!” [chuckle] due to the shape of Siri… [trails off] …shape of a cloud. [suspicious] There was a- [trails off again] …oh, Marc’s up. There was a reflection of a sun that came panning across the trees, like someone was reflecting a scope or something behind me. [sigh] Still- I keep saying “easily visible”. By that, I mean that it’s easily.. well, it’s holdable with direct vision, however, I have to be careful to keep my eyes on target, which is difficult, if you’ve ever tried to stare at a single point. So it is kinda wearing out my eyes a little bit to do this. [confidently] But when I’m on target, easily visible.
7:46:05 am – It’s visible through some thin cirrus clouds, right now, but the visibility is greatly reduced. Problem is the cirrus clouds are forming in place- [passionately] it has been consistently clear ten degrees to the north… but these clouds just start forming. At that point. And then they pass over Sirius. Now there’s a huge cloudy extent over towards the weeest… [trails off] No, the east, the east. Where the sun just rose.
7:48:02 am – Okay, the end of the cloud-thing just came over! [quieter] I mean, there’s still a few little trailing cirrus [louder] but not the thick cirrus! I’m glad that stopped forming, oh my god I’m so glad that stopped forming. Uh, Sirius is definitely harder… I’m gonna wait for this cirrus cloud to go over [before] I make any more proclamations. I can see it through the bottom of the cirrus cloud. [long pause] It’s now kinda difficult with direct vision, I think I’m using slightly averted vision. With slightly averted vision, it’s pretty much holdable. [slight pause] The time as of me saying this- the second, is seven, fortynine, oh four.
7:57:57 am – So there’s currently a cirrus cloud over Sirius, again [sigh] high cloud [unintelligible] -last as long as I would have liked, but, when it’s visible, it’s not easy, but it’s not at the edge of visibility yet. The time, as of me saying the seconds mark, is seven, fiftyeight, eighteen.
7:59:03 am – Yeah, it’s hard… Think, um, 50% of the time with averted vision, 40% maybe… [sigh] I hope that it clears up so that I can really tell when it actually disappears, instead of it just getting so faint I can’t see it through cirrus. That recording of difficulty is made in a relative gap between the cirrus- I think there’s still some light cirrus there, but… The time as of me saying the seconds mark is seven, fiftynine, fortytwo.
8:02:22 am – Okay, I’ve still got it, but MAN! It’s getting hard. Um… I had lost it for a long time there. I got it now, but, like I said… okay, it’s gone again. Cirrus cloud. Starting to look more ghostly, and more like something in my vision. I am 90-95% sure that that was not something in my vision- it moved with the sky. But it has that ghostly quality, of a transparent-ish phosphene or entoptic field phenomenon. [pause] And there’s now going very long gaps between me seeing it. I haven’t seen it again, and probably would be able to if the cirrus clouds would get out of the way… [quietly] pleaaase, clouds… [louder] Ok. The time as of me saying the seconds mark is eight, oh three, fiftyseven. [pause] Well, here comes the sun.
8:04:33 am – I got it again there for a little while- still got it- but man, it’s slight. [pause] And there goes a cirrus cloud over it. It’s, um, it’s starting to get to the point where the pops have to be very long in order for me to be sure that I’m seeing something. So like there, cause I was moving back and forth, and it was staying in the same spot, it was coming in and out of view, though. So I think that was- think that was it, it’s just.. it’s at that ghostly threshold now. [loud phone ding] [quietly] I do wish that would get out of the way… [huff] ugh, battery low. [another loud phone ding] Battery low .. again? Oh, it’s doing panorama.
[Mom comes out to take a video of me around now]
8:13:55 am – Ok, so Sirius has been pretty much invisible behind the clouds except for a couple pops when Mom was videoing me earlier. Um, and then about a minute ago I got a couple of good pops… [Mom “woo-hoo”s in the background] [chuckle] …And the time as of me saying the seconds mark is eight, fourteen, eighteen. [Mom shouts “go Lauren!” in the background] Thank you!
8:20:49 am – [frustrated] Ok, I’m calling off the search, um, it just… I, I wa- there were too many clouds, and I wasn’t able to see it for long enough… and, so, um, I guess it went behind the tree, or it went somewhere where I don’t know where to look now, so. The time as of me saying the seconds mark is eight, twentyone, twelve.
A Cloudy Nights forum thread about seeing Sirius in broad daylight can be found here: