Science Questions

Can you make any astronomical sightings during the day?

Tue, 24th Sep 2013

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Chloe asked:


I would like to know if you can make any astronomical sightings during the day.





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Sunspots are much better to visualize during the day than during the night!!!  Of course, look up on the internet about how to make an appropriate apparatus to visualize the sun. 

Solar eclipses are also seen during the day, and allowed early astronomers to see the sun's corona.

A simple sundial may also be interesting, and allow one to determine the time of day, as well as different seasons and the angle of the sun.

The moon can be seen during the day at times (new moon), and one might be able to view it with a telescope, although the detail would be less than would be seen at night.  Likewise, some of the planets may be able to be seen during the day, or at dawn or dusk.

One of the problems with looking for stars during the day is the sun illuminates the atmosphere which then drowns out the stars.  It also happens in the cities at night with all the lights in the city.  In space, a telescope is not influenced by the atmosphere, and can be used in the sunlight. CliffordK, Sat, 13th Jul 2013

Not in general. However there are a few exeptions. Right before sunset you can just start to see the brightest stars. You can obviously see the sun (which is the closest star) during the day and the moon can be ssen during the day during certain phases. Pmb, Sat, 13th Jul 2013

I wonder if a filter can remove the "atmospheric" blue from the field of vision to allow us to see the (bright) stars during the day? Lmnre, Sat, 13th Jul 2013

If conditions are right, the moon is sometimes visible in the daytime sky and on one occasion I saw daytime Venus, it was a total accident, happened to be looking at a jet trail. Never been able to spot it again. Mostly we do sun spots using a telescope and projection screen. We were able to see Venus transit the Sun with this method. Next Mercury transit is 2016 May 9

I should mention, never look at the Sun through a telescope or binoculars, that would be just like using a magnifying glass to start a fire only it is your eye retina, you can go blind. Knew a fellow that stared at a partial solar eclipse without protection, had the image of a crescent for the rest of his life.

I've always wanted to see the ISS cross the sun (or moon) but haven't made a serious effort yet.

In regards to the atmospheric blue Lmnre, since moving to Kansas a couple of old time well diggers have stated that they were able to see stars during the daytime when at the bottom of the well, I wouldn't know how to verify this, but I don't think they were "pulling my leg".

distimpson, Sat, 13th Jul 2013

Here's a picture of Venus crossing in front of the Sun, telescope image projected on screen, large dark spot is Venus, the other dark marks are sunspots, a pretty active day on the Sun!

distimpson, Sat, 13th Jul 2013

Isn't it true that in certain circumstances Venus can be seen in the sky without a telescope? Recall that this is what Elenor's father said to her in the movie Contact. Pmb, Sat, 13th Jul 2013

Yesterday afternoon I showed visitors craters on the crescent moon through a telescope, even though the Sun was still shining.
Heat haze in the daytime is worse than night, and contrast is lower in daylight.

The recent meteorite in Russia briefly outshone the Sun.
Comets are often best seen just after sunset or just before dawn.

The other event that is visible in the daytime sky is a supernova in our own galaxy. Visible supernovae are very rare, estimated at something like 1 every 400 years - but they can outshine the moon for a few weeks, and be bright enough to cast a shadow at night. evan_au, Sat, 13th Jul 2013

The light from that patch of sky would still be the same intensity, *but* every other part of their field of vision would be so dark that their pupils would dilate, letting in more of the light from that patch, and *maybe* allowing the eyes to differentiate the stars from the background (I mean foreground, as it were). The vitreous humor (that is, the liquid in the eyeball) does filter out the ultraviolet, so *maybe* dilated pupils allow the vitreous humor to act more effectively in filtering out the blue of the sky. Hmm .... I must say that I'm *not* convincing myself with my theory.

Edit: Uh oh. Snopes says they must have been pulling your leg. Lmnre, Sun, 14th Jul 2013

"Edit: Uh oh. Snopes says they must have been pulling your leg."

or a simple misinterpretation, for example, light scattering by debris  This post also states "It is possible to see stars in the daytime with a good telescope, as long as it has been prefocused and can be accurately pointed at a target."

The time I saw Venus in the daytime with no telescope was amazing but just going inside to get a camera I lost the spot and have never seen it again. Accurate location seems to be the key, our wee museum is only open in the daytime and we are always looking for real time demos, I think we will pursue this one and invest in a "good telescope", sounds like fun. distimpson, Sun, 14th Jul 2013

The latest generation of amateur telescopes have a computer and sensors from a smartphone. This seems to add about $500-$1000 to the telescope price.
GPS can identify the current time, your position on Earth, and the computer can calculate which objects are currently above the horizon, and where they are in the sky. Other sensors determine the direction of North and elevation.
With one of these, you may be able to spot some very bright objects in daytime (eg Moon, Venus and Jupiter) - but I would check with the manufacturer whether it is capable of working in this way.

My telescope requires you to align it on some bright stars at night, but has a setting that lets you save this alignment until the next time you use it (provided you don't move the telescope in between). This means you really need a weatherproof enclosure that can open and close without moving the telescope. This enclosure is getting into some serious money - perhaps more than the telescope itself!

Note: Ensure no-one looks into the eyepiece as it moves across the sky, or they could suffer blindness if it passes the Sun. evan_au, Mon, 15th Jul 2013

I have seen three real interesting day time astronomical events in my life time, the total eclipse of 1999 that I waited for for 65 years and the two recent transits of Venus.
I have occasionally seen Venus but it is very hard to find without a computer controlled telescope. syhprum, Fri, 19th Jul 2013

The question did not say see things with the naked eye, although I have a possible exception to this in a moment. 

In areas with very clear skys with a good telescope it is possible to observe the brighter planets and stars during full daylight (provided of course you know exactly where to point it).  In fact some observers of the planet venus prefer to make their observations during daylight because when the sky is dark venus is too bright as a small image on a black background and it id not possible to observe low contrast detail on the brilliant white clouds.

There are some reports of it being possible to observe a bright star crossing the zenith (notably Vega) with the naked eye from the bottom of a tall chimney looking up the inside during full daylight this is because the removal of a great deal of scattered light allows the eyes to become much more sensitive Soul Surfer, Sat, 20th Jul 2013

I believe that radio telescopes can be used during the day.
I'm not sure about x-ray and gamma telescopes.

Of course, one doesn't get pretty pictures with them without various computational translations.

Space Telescopes generally operate in the daylight, but are less affected by the earth's atmosphere.
CliffordK, Sun, 21st Jul 2013

Scattering of light from particles in the atmosphere increases as the 4th power of frequency - which is why the sky is blue in the daytime.

The sky causes much less interference with the lower microwave frequencies used by traditional radiotelescopes, and so these can be used in daylight (although some newer radiotelescopes are starting to be used at far infra-red frequencies, which will be more affected than microwaves).

One surprise from using radar for atmospheric research after the 2nd world war was the discovery that there are meteor showers in the daytime. These were invisible against the glare of daylight. evan_au, Sun, 21st Jul 2013

Here's is a fairly unusual daytime event in just a couple days, a hybrid or annular-total eclipse:

this youtube video explains it pretty well :

might get a bit of it in the UK, not much in the US and only on the east coast. As always, be careful when viewing the sun, apparently your retina does not feel the pain associated with permanent eye damage. A projected image (as with Venus transit above) is our favorite method. distimpson, Fri, 1st Nov 2013

I was thinking (even though it usually gets me in trouble), if we had a supersonic plane, 1000mph/1675kph would be nice, that could sustain this speed for several hours, you could follow the path of the eclipse keeping the moon directly in front of the sun and make a movie of it changing from annular to total. Are there any jets in service that can fly this fast? The SR-71 and Concord could do it but I believe both are retired. Perhaps Sir Richard Branson has such a device. distimpson, Sat, 2nd Nov 2013

The sky is least bright directly overhead as you're looking through less atmosphere, so the idea of seeing stars during the day up a chimney or from the bottom of a well doesn't sound impossible. The Sky at Night Magazine recently gave instructions about how to see a star in daylight with a telescope, something that isn't normally easy to do, but when the moon is near it you can use that as a guide to the exact position of the star, at which point you can make it out.

By the way, if you are going to try projecting the sun through a telescope onto a piece of paper, don't do this with a reflector telescope as the heat may damage the optics. I don't know why this is the case, but refractors are the only kind of telescope recommended for this. With a reflector telescope, you're better off using a sheet of mylar across the front end, taped on securely so it can't fly off in the wind and fry your retina. Whatever you do, don't ever try using mylar at the eyepiece end - it will melt in an instant and offer no protection. David Cooper, Sat, 2nd Nov 2013

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