Cancelling the Earth's rotation. 1hour 20mins timelapse.
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- Опубліковано 10 вер 2024
- An equatorial platform based on the Poncet principle, allows non-corrected cameras and telescopes to stare into deep space, with the earth's rotation automatically cancelled for longer exposure photographs.
Lovely bit of work Andy.
Where can I buy it?
Super simple and clever. I only have one concern (if used in photographic environment). Due to the construction, when the motor speed is constant, the speed of the platform is at maximum speed in the middle and a little bit slower, when is comes toward the end (or at the beginning). Probably there is a solution, but in the moment I don't see one - or am I wrong? If a wheel is attached directly to the arc which is in deed much more complex to design, the speed of the platform remains constant. Nevertheless: this is brilliant :-)
Cheers Axel
Yes you are right.. It's actually faster at the ends if you think about it (approximate it to Pythagoras). I have compensated for this in software by adjusting the stepper motor speed throughout its travel. (it's a 3D printer stepper motor controlled by a BBC micro:bit). In reality the difference is actually tiny and there's only a very small adjustment needed over its travel.
@@flexmaniaccan you share the coding or software you used?
What motor is used and how is the speed controlled?
It's just a regular NEMA17 and lead screw from a 3d printer.. the speed is regulated by a bbc microbit running micro Python.
Great Job! I'm working on a similar platform now. I've tried other less successful drives before, so I belive in the poncet segments and the lead screw. It doesn't need a lot of energy. We only need to consider the tangent fault. I also think this problem needs to be solved by the software. Have you taken any photo of the deep sky? And how long can you make exposed? (Sorry for my weak English...)
Hi... I'm managing approx 15 second exposures, but there are a few issues that I have to resolve. I think I am suffering some clock jitter due to the bbc micro:bit intepreting Python scripts, rather than compiled code. An arduino would probably be a better choice... I used bbc micro:bit because I already had one and it has LEDs and two buttons already installed!
Flame Nebula, captured using the EQ platform, can be seen here. This has about 20mins worth of total exposure time - multiple 10sec subs. No calibration frames used. photos.app.goo.gl/VjZF6WgHQwwG73uGA
@@flexmaniac I recommend the Arduino. I use it with a DC motor, and I took a random incredible 30 second exposure photo without motor speed change.... before the winter arrived, so now I'm very frustrated until spring. Anyway, Arduino makes very stabile the motor. The next step will be to use a stepper motor and change its speed during the run.
@@flexmaniac Not bad!
@@villasmiklos Yes I've got an Arduino Uno, I just haven't had time to do it yet... and it's kind of good enough that it works most of the time, so it's not urgent.
Can you make instruction? Your solution is great
Hi, the concept is explained here: www.reinervogel.net/index_e.html?/Plattform/Plattform_e.html
where can I buy one of these
I'm afraid this was a one-off home project :-)
This is bloody clever, where did the lead screw come from? And why is the curve opposite to the earth's surface curve? Neat
The lead screw is something normally used on a 3d printer, combined with a stepper motor you can very high resolution control. Each step is 1/6400 of a degree on an 8mm lead screw length, so 12.5um in linear motion.
As the earth rotates around the celestial pole, you rotate the camera/telescope in the opposite direction at 360/24 = 15deg/hr.
The platform is aimed at the north star (pointed exactly north) and the arc is prescribed around a cone with its axis around an elevation angle the same as the latitude of its position (52deg in my location)..
Certainly easier with a drawing (which isn't possible here!)
Is this compatible with 2 min exposure for astrophtograpy?
2 mins is probably too much, but it depends on your focal length. For wider FoV it might be ok. Ive been using 750mm FL and 20secs seems about the limit.. BUT this platform can be improved and longer exposures should be possible. This is due to using a micro:bit I think.
30secs at 750mm should be possible. 2mins at 750mm, i doubt it.
how do you reset it?
The motor stops when it gets to the end (or I stop it). Once disabled I just spin it back by hand, it only takes about 10 seconds.