While night is the ideal time to observe any object, sometimes, whether by choice or circumstance, you can begin your observation session during the day while the Sun is still up!
There are two celestial events that only happen during the day, a Solar Eclipse, and a Transit of Mercury/Venus! During those events, only people on the day side of Earth can see them, and with eclipses especially, you have to be in the correct locations, otherwise you can’t even see a partial!
Occasionally, a bright meteor can be seen streaking across the sky during the day as well, yet those moments are very quick and easy to miss!
Let’s say your place offers public telescope viewing beginning around 7 pm. Thanks to daylight savings time, during the spring and summer months, the Sun doesn’t go down until AFTER 7 pm, or after 8 pm near summer solstice! But that doesn’t matter, the eager people still expect you to show them something, and they don’t want to wait until nightfall due to their own schedule constraints!
This article is more about common and a couple not so common things you can look for to observe during the day.
Here are your choices!
Well, that’s a given! The Sun dominates the daytime sky, and often leaves you no choice but to point your instruments at it. Just make sure your equipment has the proper filters to keep your eyes safe from any damage!
The sun can look rather bland and boring, as most white light filters make the Sun look like featureless orange disc. If there are sunspots visible, then there’s a reason to increase your magnification, but if there isn’t, then all you can do is keep the view as zoomed out as possible so people can see the edges of the disc. Since it’s not something that people usually see, they don’t know what they’re looking for, and may not even know if they’re seeing it correctly.
When the Sun gets low enough in the sky, it can start getting dimmer through a telescope. The more haze there is above the horizon, the more dim it looks, making it harder to see as you make your transition from a daytime object to a nighttime object.
Even during the day, the Moon is a good object to look at through a telescope, and you can easily see some good contrast on the features. A standard lunar filter can add more contrast and less glare if it’s still too difficult to see during the day.
Depending on the phase, you can catch the Moon in the morning, or afternoon. If your prime viewing hours during the spring and summer months star before sunset, your window to observe and show the Moon only lasts for 10 days out of the month during the waxing phases, with all the other days the Moon will either be too close to the Sun, or below the horizon, leaving you with no Moon to view while the Sun is still up.
Venus is the brightest planet in the sky, and it’s bright enough to spot while the Sun is still high in the sky, you just have to know where to look. It’s so bright that even your finder scope should pick it up the white dot in a blue sky.
However, due to its inferior orbit, it goes through cycles between being the “Morning Star” and “Evening Star.” Depending on which part of the cycle it’s in, you will have times when Venus is visible in the west before the sun sets, or it will be shining bright in the predawn hours, and be the last “star” you see before sunrise.
Yes, Jupiter can be observed in the daytime through a telescope! If the planet is far enough away from the Sun’s glare, it can be picked up. Because it’s not as bright as Venus, it won’t appear as bright through your finder scope, and it can be tricky as we’re looking for a white dot in a bright blue sky. But if your telescope is big enough, it should pick up the planet.
The only downside is, don’t expect much detail! Through a good telescope, the disc can be seen as a white circle, and even the cloud bands may be glimpsed during the day, but if people look at it and act unimpressed, you just have to tell them, “well, what did you expect? You’re looking at it during the day! It looks MUCH BETTER at night!”
A Bright Enough Star
Yes, if you get the telescope pointed exactly where the star is, it is possible! Even with the Sun higher up, stars brighter than magnitude +1 are all accessible with a small telescope as long as the star is 30 degrees or more away from the Sun. That means stars like Sirius, Canopus, Arcturus, and other zero magnitude stars can be spotted.
They will appear as small points of light, and depending on the clarity, the brightness of the star, and of course how large your telescope is, they may have decent contrast against a blue sky, or they’ll still be hard to spot. You may be able to see some color on the star, but don’t expect much. The fact you can spot such a star is an accomplishment, and a good demonstration on the telescope’s capabilities.
An Extremely Bright Comet
This one is a once in a life time event, but sometimes a comet can get extremely bright, and be visible during the day! Once more, it just can’t be too close to the Sun, but there have been exceptions! Comet Ikeya-Seki in 1965 was a magnitude -10 object within a couple degrees of the Sun, and reportedly was easily seen in clear daytime skies just by blocking the Sun with your hands!
We can only wish that this was a more common choice, but the reality is that comets like these are extremely rare, perhaps only a few per century at the most, and the last one that happened was in 2007. But you never know!
A Bright Supernova
While a daytime comet can be a once in a lifetime event, a supernova in our own galaxy that can be seen from Earth, the kind bright enough to be seen during the day, is definitely a once in a millennium event. The last notable one occurred in 1604, which we know as Kepler’s Supernova. We have yet to have one like Kepler’s in this millennium!
While yes, there was a naked eye level Supernova that occurred in 1987 (1987A), it was no brighter than magnitude 3, and actually occurred in the neighboring Large Magellanic Cloud, a dwarf galaxy outside of our own, only visible in the Southern Hemisphere.