originally posted by: burntdogg
I have been observing these flashes for many years now, and in most cases they are caused by fast spinning space-junk, although there are likely also
flashes from operational satellites.
Space-junk has been building up at an almost exponential rate in recent years, and it does not take a huge piece to reflect enough sun light for the
object to be visible from the ground. Major contributions to SJ population have been from the Anti-Satellite weapon tests and from the collision of
IRIDIUM 33 and COSMOS 2251 a few years back now.
There is also a near constant stream of satellites being launched into orbit now, so spent rocket boosters etc can also be observed, although I don't
think they have the super-reflective surfaces which cause the brightest flashes (I could be wrong).
Tracking and identification is fairly straight forward...
However, you will need a camera + appropriate lens + tripod ($50 for a basic, but better to spend double and get a good solid pod if you think you
want to do more photography - eg. google "055PROB tripod" or "055XPROB tripod") and a few other accessories (memory card, remote release with "running
shutter" lock - $10 for both new - buy a Chinese release from ebay). It can be done on a fairly budget if you buy used gear. The lens is more
important than the camera, and a good one to choose is the Samyang/Rokinon 24mm F1.4 ($200 used aprox.), although QC on these is not great and the
stars may not be perfect in the corners of the frame when @ max. aperture, so if you want pretty pics of stars, you may be better of looking for
another 24/1.4. It would still work for this project though.
If on a tight budget, something as old (and cheap) as a Canon 20D (less that $50 used for a low use body I would think by now), will do the job, but I
wouldn't go older than that. A Canon 70D is a great choice if you want to spend a bit more ($350-400 I think) and you can use it to record HD footage,
although this feature works best in good light and is near useless for footage of stars. It is a great camera though, and very good value for money.
If money is not a huge issue, and you want a camera that will record UHD footage of the stars, and satellites too (although it might not work well for
this project as the footage is quite noisy and flashes would likely be lost/hard to spot, but you can still use still images which are much less
noisy), then a Sony A7S would be good bang for your buck, used @ around $500 or $600 I would guess currently.
You might be able to get away without the camera if you are close to your PC or laptop, but getting an image of the object will create a permanent
record, and give you a more positive confirmation of the identity. There can be multiple objects in the same part of sky, some or all below the
threshold of naked eye visibility, so you can only be truly sure of an identification if you catch at least one glint from the object, but preferably
some of the trail which it leaves as well, if any is visible to the camera.
Here is what you do:
1/ Set up camera indoors (RAW image quality, manual mode, daylight white balance, continuous shooting mode, set the time as accurate as you can get it
using your PC's clock - turn off ALL noise reduction), and focus using the stars (it's a bit of an art, and you should read up on it) once you get
outdoors. Take test exposures using max. aperture on the lens and using ISO 800 (20D) or ISO 1600 or 32000 on more recent bodies. Keep them short,
between 6-10 seconds ideally, but you might need less than that to keep the sky from washing out if you are somewhere light polluted, otherwise it
will be hard to see any trails left by objects. You may need to experiment a little to get it right.
2/ Observe, and wait... you might want to cover your camera, to keep it warm and dew free till you need it, but be careful not touch the focusing
3/ When you see a flash, uncover/turn on, and point the camera as close to the flash as you can, without any delay (practice beforehand). Set the
running lock to the on position and the camera will take exposures till you disengage the lock (this works for Canons, not sure about others). Give it
a minute or two, and hopefully you have imaged some flashes or a trail of the object.
4/ Once you get back in and you've off loaded the images to your hard drive, zoom into each image and check for trails, ideally with software which
will let you flick between the images without delays to load them - this makes it easier to spot small changes between images. You may need to
process/convert the images from RAW format to something like jpeg first.
5/ If you found a trail/glint in an image, start up Sellarium
, and load the Satellite plugin in the solar system
6/ Stellarium should load up a bunch of satellites, but make sure the data has been updated, if not, ask it to do so. Then check the appropriate part
of sky during the time of the exposures you took to see if any objects pass through. You'll find the correct timing of the exposure in the image
file's EXIF data.
7/ Assuming the last step did not reveal any candidates, go to celestrak TLE data
all the data you can from the "Special-Interest Satellites" section. You'll have to cut and paste the "debris" sets into separate .TXT files, and load
them one at a time, manually into Stellarium. Go easy, especially if have an older PC, and make sure you remove one lot of debris before loading up
another, unless you have a very fast PC, or Stellarium can slow down (and possibly crash).
That's basically it. Just make sure you always have up to date TLEs. I did used to have a
with actual examples (using different software though), but the images have
since been lost.
I no longer bother to identify satellites/junk (unless I have a good reason) as I am usually trying to image natural phenomena such as meteors, and
satellites/junk in an image is a PITA as there is so much of it, and even a small trail detracts from an image, but I do still catch plenty of junk
flashes and trails.
You can get a good idea of the type of things you will capture with a 24/1.4 lens with this UHD timelapse I've uploaded, although it was made using a
full frame camera, so a little wider FOV than when using a crop sensor DSLR like the 20D or 70D: vimeo.com
Please feel free to ask if you get stuck anywhere, and let us know how you (or anyone else who want to give it a try) get on.
edit on 16-9-2019 by FireballStorm because: (no reason given)