[HN Gopher] A Guide to Smartphone Astrophotography [pdf]
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A Guide to Smartphone Astrophotography [pdf]
Author : happy-go-lucky
Score : 132 points
Date : 2022-06-23 11:11 UTC (1 days ago)
(HTM) web link (spacemath.gsfc.nasa.gov)
(TXT) w3m dump (spacemath.gsfc.nasa.gov)
| Melatonic wrote:
| I thought about making a very lightweight star tracker for my
| phone - if you took that with you and a way to mount it (like a
| small tripod) and then had the phone shoot a raw timelapse of
| whatever maximum exposure is possible (say 30 seconds) then you
| could do a track + stack and come out with great results. You
| would need to stand in place for probably about 30 minutes
| minimum or more to get enough photos
| mgraczyk wrote:
| Plug for my team at Google. One of the cool things in the Pixel
| camera is an "astrophotography mode", which takes far more
| pictures than normal with longer exposures.
|
| https://ai.googleblog.com/2019/11/astrophotography-with-nigh...
|
| You can try it out on any recent Pixel device by holding the
| phone very still (probably need to mount it) when it's dark. You
| can get incredible images with no additional effort, just
| pointing it up at the sky.
| yreg wrote:
| I find it funny (but cool!) that this is a full on 190 page book
| on the topic.
| rob74 wrote:
| Smartphones (at least those with single cameras) have the
| advantage that you can just hold them up to a telescope's
| eyepiece and take a picture, which is a bit harder with "real"
| cameras.
| dylan604 wrote:
| they make mounts now where this is exactly what you do which
| is nice when the device can do longer exposure than you can
| hold still. they are adjustable so you can use it for a
| plethora of different devices.
|
| They're great for use at star parties. You can keep switching
| out eyepieces (a common thing) to get the view you want for
| whatever is being viewed. Then each person can get a pic on
| their device. It makes them much more engaged especially
| since the CMOS sensors can start to pick out colors that the
| human eye can't see.
| dekhn wrote:
| Even better than a smartphone, mounting a DSLR at the prime
| focus on a telescope makes it really fun at star parties.
|
| I went to a star party for some kids with my scope. There
| were a bunch of other guys there with scopes- all of them
| reflectors with hard-to-see-through eyepieces looking at
| faint blobs in the sky. The kids seemed bored. So I set up
| my refractor, installed my dslr (turning on Live View) and
| pointed it at Jupiter. You clearly see the planet and
| several moons around it. The kids thought that was great
| and one mom looked at me and asked... "Did you just show us
| the moons of Jupiter". I could see at least one kid look at
| it, look up at the sky, look at the telescope, and sort of
| put it all together.
|
| The DSLR has better image quality, the image is falling
| directly on the sensor, the noise is very low, and there's
| a digital zoom option that works well.
| dylan604 wrote:
| Except a DSLR can't make an image that they take on their
| own device and walk away with it to immediately post to
| socials. that's the thing that draws them in.
|
| A DSLR image needs to be processed to bring out the true
| qualities of the image. Also, a DSLR's tiny little pixels
| while a literal shit ton of them means that objects like
| planets resolve very small in the image. That's why most
| plantery images are still popular to use webcam level
| cameras.
| dekhn wrote:
| That's the point of digital zoom (which is built into
| live view).
|
| Nothing stops you from taking a photo of the dslr screen
| with a phone camera, either.
| dylan604 wrote:
| Except live view is just that, live just like your eye on
| the scope. To really get the benefits of a DSLR, you want
| long exposures like 20sec or longer to really pull in
| those photons. Then you probably want some auto-guiding
| to get longer to avoid trails, blah blah.
|
| So other than planets, live view will just show the same
| thing you can see through the eyepiece (black and white).
| If you're zooming in on the digital zoom, maybe you need
| a larger selection of eyepieces? a nice 9deg or similar?
|
| I have a scope that was bought specifically for DSO
| imaging, so when I point it at the moon, the full disc is
| maybe 25%-30% of my frame in prime photography with my
| DSLR. Which is still cool as most scopes are so zoomed
| into the surface you have to scan around to see the full
| disc, which is also cool in its own right. with a 30deg
| eye piece, the full disc is simply stunning. that same
| eyepiece looking at jupiter/saturn has them very very
| small but still easily identifiable. switching to a 15deg
| gets to the point i need ND so the moon doesn't blind
| you, but brings the planets into a much less
| disappointing view.
|
| but at the end of the day if someone looks at whatever
| you show them and is engaged, then by all means continue.
| definitely not suggesting "you're doing it wrong" at all
| dekhn wrote:
| You use the ISO setting (which is Gain on a webcam, often
| not a changeable paramter) which is much better than your
| eye on the scope. For example, looking at M42 through the
| Live View, you can easily see all the colors and fainter
| parts that aren't visible through an eyepiece. It's
| clearly picking up light the eye doesn't process or
| report to the brain through an eyepiece.
|
| I'm not using an eyepiece. I have the DSLR at prime
| focus. The reason digital zoom works (to give more
| details) is because the LiveView screen doesn't have the
| screen resolution to show all the data.
|
| Trust me, I spend a lot of time doing this (I build
| automated telescopes, solarscopes, microscopes for fun).
| The DSLR sensors beat all the webcam sensors (I'm still
| trying to find an affordable sensor board with good
| specs, for example, the Sony StarVis, that I can
| integrate so I don't need to mount a damn DSLR any
| longer- they're too big and heavy and need too much
| power).
|
| I think there's two camps- one that really like eyepieces
| for the amazing results you can get with bright objects,
| and one that likes to look at digital images in real
| time, or later.
| dylan604 wrote:
| At that point, you might as well take an HDMI out
| connected to a larger screen to make it even more visible
| to those that wander by. I've seen a group do this with a
| camera designed for purpose that has software running
| stacking so that the longer the image is being viewed the
| better the image. They then project this for a larger
| visible image. Sounds weird as projector == bright light
| which is frowned up, but they always setup in a way that
| is not disturbing and since the image projected is pretty
| dark it's not as bad as one might think. They do
| everything they can to never blast white.
|
| As far as wowing people, it's pretty impressive. Once
| they go to the next celestial object, you can watch as
| the image stacking starts working as you see the fainter
| object continue to become more and more distinct.
| duskwuff wrote:
| > To really get the benefits of a DSLR, you want long
| exposures like 20sec or longer to really pull in those
| photons.
|
| A lot of modern smartphones support long (~30s)
| exposures, with compensation for motion during the
| exposure. Under the right conditions, they can take some
| very nice night sky photos -- and I suspect they'd do
| very well on the end of a telescope, too.
| dekhn wrote:
| in 30s, the stars have moved. Do the phones somehow
| derotate?
| duskwuff wrote:
| I believe so. The phone can compensate for its own
| physical motion during an exposure (e.g. when being held
| in shaky hands); proper motion should be no different. If
| anything, it's easier, because it's so smooth. :)
| orbital-decay wrote:
| Skimming the book, most of it isn't terribly specific to
| smartphones. It's more or less an introductory book on
| astrophotography in general.
| tamiral wrote:
| The amount of nerdiness in this is amazing I'm so excited to
| read it! Especially with the new crazy zoom functions on phones
| and aligning them easier with telescopes !
| nshm wrote:
| Interesting this field is changed significantly last 20 years.
|
| One thing is light pollution need to buy a big telescope if you
| can't transport it to the dark place. You have to drive 100+ from
| a big city.
|
| Second is advanced image processing with deep learning. There is
| no need for accurate sky tracker anymore, you just shot many
| images and software combines.
| [deleted]
| MonkeyClub wrote:
| > Second is advanced image processing with deep learning. There
| is no need for accurate sky tracker anymore, you just shot many
| images and software combines.
|
| This is extremely helpful for professional astronomers, but
| having started astrophotography back in the day with a 35mm
| Rollei that allowed for arbitrary exposure, the moon, and a
| very numb index finger, I feel that the one image you produce
| with care and accuracy trumps the collage on some emotional
| dimension for me.
|
| The collage is obviously the better image, but the amateur's
| photograph somehow captures both stars and stargazer.
| dekhn wrote:
| I don't have any problems in a suburban area of the Bay Area
| with a small refractor. I can see bright nebulas, etc. The only
| reason for the big scope in a dark area is if you're trying to
| look at deep sky objects.
|
| You still need a sky tracker to get enough exposures and
| generally, you want the item centered because that's where the
| optics are best.
| nshm wrote:
| We all know Bay Area is a great place to live geographically
| ;) Try to find black zone around Chicago for example.
| dekhn wrote:
| I live in the middle of the peninsula- I can see orange in
| every direction I look at night. I just think this only
| matters when looking at DSOs. And generally, cities are bad
| for astro because of all the heat turbulence.
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