Not Geocaching .... But Cool Anyway.
As many have figured out, I'm a very active amateur astronomer. (AstroDav ... gee, whodda ever thunk it? :lol: ) Around a year ago, I was able to image a VERY rare phenomenon. This image was featured on several different astro-sites over the following month or so after I snapped it. It's a dual Iridium flare.
For those who don't know what Iridium's are, they are a "constellation" of around 50 or so commo-satellites. They provide the workage of the expensive "Iridium satellite phones", which are still used, but have experienced several periods of less-than-profitable times ever since they were first brought into service years ago.
These satellites are unique in that they have large ultra-reflective solar-cell arrays which often catch the sun's light at times, producing a "flare" which can last about 1 minute. During these flares, the satellite commonly brightens from around magnitude 6 (just visible to the eye), up to a whopping magnitude -9. That makes them the brightest normal thing in the sky, by far, other than the Moon & Sun.
That latter value is so bright that it will easily cast shadows & will definitely ruin your night vision if you are looking right at it. The real neat thing about these flares is that they are 100% predictable & are listed on several sites for weeks out at a time. All you need is your exact time, down to about 10 seconds accuracy, & your exact location. The difference between so-so bright & super-bright can be only 10 miles or so down here on Earth, so many Iridium-chasers will actually take short trips to get right under the spot of maximum intensity .... sorta like chasing a solar eclipse.
These things AREN'T rare .... they happen several times per night all over the Earth. At any one location (your back-yard), a medium-brightness flare will occur about once a week. A super-bright one about twice per month.
Due to orbital specifics, they tend to happen in waves however. Your location might go 2 weeks without any nice ones, but then have 2 every evening & 2 every morning for 3 days at a time. They will be all brightness's & you can usually expect a REALLY good one at least once during that "outbreak".
But what IS rare is for 2 of them to happen side-by-side, at the same time. And what is REALLY rare is for both of those to be super-bright flares. That's why this image is pretty much a once-a-year thing for any one location, most likely even further apart than a year.
I'd have to dig into my notes to list the exacts, but the dimmest one here is about a mag. -3, while the bright one is around a -7. This exposure is about 1 minute long, so that gives you an idea of what speed they move & the time it takes to flare up & then dim back down.
Very little equipment is needed to do this. This was through a Canon D400 digital camera, with a 35mm lens. The only thing is, since the flares last about a minute, the stars will trail if you don't have the camera mounted on a tracking mount. 30-40 seconds is as long as you can expose a stationary camera without that happening. This was piggy-backed on my 12" telescope, which you can see part of at bottom. It was tracking at the time, allowing me to take a long exposure & still have pin-point stars.
But not having something to track wth doesn't mean at all the image can't be spectacular. Star trails are the most basic type of astrophotography possible, other than perhaps moon-shots. And they are also among the most favorite, even amongst those of us who might typically be stacking dozens of 20 minute CCD exposures of deep-sky objects, taken through huge computer-controlled scopes.
The reason being is that star-trails are simply simple & simply beautiful, the very most basic way of showing the heavens are actually always in motion, never staying the same. Because of this, trailed stars can actually INCREASE the beauty of an image like this. Not only will it draw attention to the non-trailled flare, but provides a startling contrast between the "natural" heavens, and the artificial stuff that we've put up there. All's you's needs is a camera & a tripod. 8)
Since these things only happen within about 90 minutes of sunrise & sunset, you can see the last bit of purple twilight at bottom of the image. Actually, it was dark to the unaided eye when I imaged this. But with the long exposure & my camera modified for extra sensitivity, the picture picked up some remaining twilight that the eye couldn't see. I think it just adds to the image myself, sorta framing it along with the front of my telescope.
I have exposed literally hundreds of celestial images, probably thousands, in scopes as large as 24" & with CCD's costing 10,000 $$$'s. But this very simple image, taken with nothing more than a $500 digital camera, is my very favorite of all.
Sometimes the simplest things are the most beautiful: