[HN Gopher] OpenAstroTracker: A cheap 3D-printed tracking mount ...
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OpenAstroTracker: A cheap 3D-printed tracking mount for DSLR
astrophotography
Author : reimertz
Score : 90 points
Date : 2021-05-10 12:18 UTC (1 days ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| dylan604 wrote:
| Dupe: https://news.ycombinator.com/item?id=26930958
| emptybits wrote:
| This is quite brilliant.
|
| Here's another approach to tracking, employed by Pentax and maybe
| others: Use 5-axis sensor movement to track stars (i.e. use the
| motors which move the sensor for in-body stabilization)
|
| Given GPS coords, software can do this to the limits of sensor
| movement afforded by the camera body. I don't have a Pentax but
| modern models can apparently track for at least 4 minutes.[1] (!)
|
| In theory, official or unofficial firmware for other models of
| camera might be able to do the same.
|
| [1]
| https://milkywayphotographers.com/article/2021/01/21/pentax-...
| wtallis wrote:
| I think this requires not just a GPS fix but also fairly
| accurate heading information from an electronic compass and
| tilt information from the camera's accelerometer, because
| shifting the sensor in the right direction requires knowing
| which part of the sky the camera is pointed at. (I haven't
| bought the astrotracer add-on for my Pentax because it's crazy
| expensive for what it is, but it should be at least a bit more
| than just a GPS receiver.)
| martyvis wrote:
| Surely in camera, it is just a matter of taking a shot, wait
| an interval, take another shot, then shift/rotate the two
| images until X number of bright spots line up and then form a
| new composite, rinse and repeat. If you have a motor in the
| camera for stabilising you can use that shift/rotate
| parameter to move the sensor for the next shot.
| avmich wrote:
| Tried to find some mechanical data on this and couldn't :( .
| What's the size of it, what's the working speed of motors?..
| [deleted]
| dukeofdoom wrote:
| How does this compare to something like move-shoot-move? I think
| that one costs only $200. Is it even worth it to DIY.
| dheera wrote:
| Almost everything is cheaper to buy than to DIY. This is a
| hacker forum and people like to DIY for other reasons than
| cost, including customization, the learning experience of
| building something yourself, being fully FOSS, not waiting for
| long lead times in some locations, and other reasons.
| dylan604 wrote:
| Shoot-move-shoot does what it sounds like. It moves the
| platform, allows time for the movement to settle, snaps the
| shot, then moves again. Astrotrackers like this are constantly
| moving at the same rate that the earth spins on its axis. This
| allows for the subject to remain in the same poistion in the
| frame during super long exposures. Depending on the accuracy of
| the polar alignment and the focal length of the lens, tracking
| allows for shots to go from <20 seconds to multiple minutes
| long for one exposure.
| andrewxdiamond wrote:
| What is the benefit of using robotics to move the camera over
| image stabilization software in post?
|
| Is it simply image quality? Or are there more trade offs?
| dylan604 wrote:
| The is a common question, but there are certain things that
| are just better done in camera than post. Then there are
| situations where a combination of in camera + post provides
| optimum results. Astrophotography is one that can and does
| use both. The longer you can expose, the more information
| obtained. For ultimate long shots, you need to compensate
| for the earth's rotation. You continue to snap away all
| night, and then take those images into post where you stack
| the images. The stacking software adds the data together
| resulting in a single image that is the equivalent of a
| single image with an exposure time equaling the sum of each
| shot.
|
| Why do this? If you do single long exposure, there is a
| very good chance your image will have an airplane fly
| through, a satellite streak by, or something more
| terrestrial like a fellow stargazer shining a laser through
| your frame, car headlights, etc. Taking a series of short
| exposures limits those issues, and if it happens, you throw
| out that shot and only loose 45-60 seconds instead of 15
| minutes.
|
| Stacking can also use shots you take when the lens is
| covered called dark frames. You take this for the same
| exposure time as the normal shots. This provides a noise
| pattern that builds up in any electronic sensor as the heat
| builds up from staying energized for so long (as well as
| natural summertime heat). That noise pattern can then be
| subtracted by the stacking software. The stacking software
| can also realign the images so you can use shots from
| multiple shoot days (er, nights).
| spfzero wrote:
| Taking short exposures and stacking also can help by
| removing the effects of periodic error in the mount gear-
| train (or belt-train).
| dukeofdoom wrote:
| You need a long exposure to let in enough light for stars
| to become clearly visible. If you expose for longer than ~
| 30 seconds, then the earth will rotate enough to start
| causing star trails. This will physically rotate the camera
| to counteract earths rotation.
| dukeofdoom wrote:
| I'm not sure if that is correct. It says on their website
| it's a start tracker. https://www.moveshootmove.com/
| sdfsfsrgg wrote:
| It can do both. They seem to use the product's name ("move-
| shoot-move") to refer to a mode which both tracks the stars
| and moves independently, creating a panning timelapse.
| dylan604 wrote:
| Interesting. I didn't realize there was a product/company
| with that name. Shoot-move-shoot is a common saying in
| motion controlled photography, and that was what I
| described.
|
| I love the age we're in where anybody with a little know
| how can cheaply/affordably build something that was only
| available to the very well funded before. Each one of these
| are attempting the same thing, but trying to avoid the pain
| points each dev has seen from other products.
| dheera wrote:
| Their marketing is a little dishonest though.
|
| https://i.imgur.com/QD32T7r.png
|
| They show all the other trackers with an Alt-Az wedge, but
| show their tracker without that piece, to make the other
| trackers look big.
|
| With the specific 2 other trackers pictured, you can detach
| that wedge and use them exactly like the MSM tracker without
| their Alt-Az mounts and they would be a lot smaller.
|
| Personally I own a SkyGuider Pro and use it with a pan-tilt
| head tripod and no wedge.
| dylan604 wrote:
| Haha, I noticed the same thing. I've started watching some
| of their tutorial videos, and have some other nit picking
| comments as well. However, these will probably get someone
| that's never done astrophotography up and running with the
| ability to get some great shots totally unachievable 15
| years ago in this price range.
| LeifCarrotson wrote:
| One benefit of shoot-move-shoot is that when
| combining/compositing the images together in post, you can
| remove and adjust for temporary artifacts like satellites or
| terrestrial lighting that would otherwise ruin a long
| exposure. You can also compensate for motion platform
| inaccuracies by shifting the location of each layer to keep
| the object you're trying to image at the same location in the
| frame. Minutes-long exposures mean you're just ORing all the
| photons together, and you get what you get.
| foobarbecue wrote:
| I use a Soloshot to film my surfing. I'm annoyed with the buggy
| closed source software and wondering if I could replace it with
| one of these...
| [deleted]
| MetaWhirledPeas wrote:
| This is nice! Is there something similar that's simpler and
| dumber, that just handles the rotation but doesn't try to locate
| objects?
| rripken wrote:
| Barn door trackers.
|
| https://en.wikipedia.org/wiki/Barn_door_tracker
|
| https://hackaday.com/2013/08/08/building-a-barn-door-tracker...
| teraflop wrote:
| Here's a very simple one-axis tracker using a 24-hour clock
| movement and a 3D-printed GoPro mount:
| https://hackaday.com/2018/06/03/3d-printed-clockwork-star-tr...
| rripken wrote:
| That really is a great hack if your camera is light enough.
| Genius.
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