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Using Ronin-S as a star tracker for astrophotography?
1654 13 2018-7-4
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Thomas Berglund
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Norway
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Ronin-S already has some pretty amazing features for timelapse and panorama photography. Has anybody ever thought of using a gimbal like Ronin-S as a star tracker for astrophotography? Would it even be possible?

Thomas
2018-7-4
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WernerD
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Unlikely. The absolute precision is not high enough. Just imagine how high the precision needs to be to keep one star on one sensor pixel for an extended amount of time.
You will be better off with multiple pictures and stacking.
And for deep field photography you need a polar mount.

So depending on what you want, it might help but just a little. Image stacking is the better solution. for such simple cases.

That would be my take at least.
2018-7-4
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Thomas Berglund
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WernerD Posted at 2018-7-4 10:17
Unlikely. The absolute precision is not high enough. Just imagine how high the precision needs to be to keep one start on one sensor pixel for an extended amount of time.
You will be better off with multiple pictures and stacking.
And for deep field photography you need a polar mount.

Werner, thanks for the reply! You are probably right. Just wishful thinking from me I guess, after looking at solutions like iOptron SkyTracker Pro
2018-7-11
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sky_makai
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I think it's very possible.  The question is whether the gimbal motors are capable of very-VERY slow and consistent movement.  
Active tracking isn't necessary at all if the gimbal's software program would be set to function moving the motors the same way a star tracker works.  A star tracker's motor moves in one direction at a very specific and continual speed.
2018-8-26
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Thomas Berglund
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sky_makai Posted at 2018-8-26 15:41
I think it's very possible.  The question is whether the gimbal motors are capable of very-VERY slow and consistent movement.  
Active tracking isn't necessary at all if the gimbal's software program would be set to function moving the motors the same way a star tracker works.  A star tracker's motor moves in one direction at a very specific and continual speed.

Thanks for the reply. Yes, it would be a pretty incredible and unique feature to add to an already awesome gimbal. I'm at least going to submit a feature request for this.

The Ronin-S is indeed able to make very subtle movements. Let's see what the DJI engineers think about this.
2018-9-30
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Thomas Berglund
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What is actually the best way to submit a feature request though? Is there a dedicated DJI page for feature requests?
2018-9-30
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sky_makai
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Thomas Berglund Posted at 2018-9-30 13:41
Thanks for the reply. Yes, it would be a pretty incredible and unique feature to add to an already awesome gimbal. I'm at least going to submit a feature request for this.

The Ronin-S is indeed able to make very subtle movements. Let's see what the DJI engineers think about this.

This is an interesting topic, whether the gimbal motors are capable of as much accuracy as a step motor.  Step motors are extremely accurate for slow increments, and are what's used in polar mount trackers.  

I'm not sure if/where there's a feedback channel for DJI.
1-2 19:17
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raphael_bellizzi
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sky_makai Posted at 1-2 19:17
This is an interesting topic, whether the gimbal motors are capable of as much accuracy as a step motor.  Step motors are extremely accurate for slow increments, and are what's used in polar mount trackers.  

I'm not sure if/where there's a feedback channel for DJI.

I never did Astrophotography, but what about create a track motion and the A and B points would be the exactly points for the movements of the stars and you set like hours to run this entire track and use the intervalometer to take the pictures instead of the Ronin S?
1-2 20:04
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Bill Broadhead
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X2 for this!!!!  If the motors are capable of very small continuous movement, this would be a killer application. It would still be necessary, of course, to find a way to align the unit with Polaris, so the tracking would be synchronized with the earths spin.

On a related note, has anyone used multilapse on the ronin S to do a series of stop motion long exposures of the Milky Way?  Waiting for a clear night to try this.   Thanks!
1-4 18:15
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WernerD
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Easy to find out.
For star tracking you need three things: Precise absolute position, smooth movements and long term exposure.
The most simple thing to test is the long term exposure. So position the Ronin to a static object and do a 30sec exposure with a 70mm lens. Is the picture sharp? I say it is not. There is always a slight vibration
1-5 00:17
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Niccolo16
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WernerD Posted at 2018-7-4 10:17
Unlikely. The absolute precision is not high enough. Just imagine how high the precision needs to be to keep one star on one sensor pixel for an extended amount of time.
You will be better off with multiple pictures and stacking.
And for deep field photography you need a polar mount.

Do you think its possible to use the ronin app to get it to track slowly? I havent personally tested it, but with the timelapse mode, I wouldnt be surprised if you could get it to work
1-6 18:43
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WernerD
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I think we need to clarify the use case.

For a wide angle lens like a 16mm or even a 35mm you don't need a telescoping mount. You take multiple images over a long period of time and stack them together on the computer. All the alignment is done during that post production.

The opposite of that is deep space photography. The lens is a 2000mm and with a 30 second exposure time the image is all black still and because of the large zoom even the slightest move would mean the stars are not sharp. So here you need to keep the star precisely at the same pixel for the whole time while the earth is turning. That is the sweet spot of telescoping mounts. For these extremes the Ronin will have too many vibrations in the motors. Not to mention you cannot mount such large lenses.

Somewhere between those two extremes is our use case. I have the feeling that even a 200mm lens and 30s exposure time will have so much shifting and tilting in the motors that even a static object will not be sharp. But that is to be tested, as said. If that has been proven, the next test is to follow the star. For a wide angle lens the precision can be good enough. For a longer lens probably not.

Don't get me wrong, I would love to do that. And in fact I am working on it. I am currently trying to debug the Bluetooth communication protocol between the Ronin app and the Ronin-S in order to send commands of my own. DJI is not very supportive here, to say the least, and the protocol would need to support certain functions I doubt it does, e.g. absolute positioning. The app does support relative movements only: Pan with a speed of x% to the left. We would need the speed value to be with units, e.g. 10°/sec. And best would be to say "pan to position +10° and tilt to +20° relative to zero".

1-6 23:40
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fans11076349
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WernerD Posted at 1-6 23:40
I think we need to clarify the use case.

For a wide angle lens like a 16mm or even a 35mm you don't need a telescoping mount. You take multiple images over a long period of time and stack them together on the computer. All the alignment is done during that post production.

Hello all,

this looks like a really cool idea if we can get it to work.  I did a stability test with a Panasonic GX8 and a 12-35 lens (24-70mm in 35mm full-frame equivalent) with 30 seconds exposures.  The camera has to be really well balanced to get it as stable as possible.  The results are somewhat variable, tough I cannot really put my finger on the exact reasons.  In about 1/3 of the exposures I could get a perfect result without any wobble.  

It would be interesting if some DJI engineer could provide input on the technical questions such as precision and smoothness of the motors, plus the API and its precision.  My wild guess is that some firmware tweaks might be necessary to achieve the level of precision required for star tracking.

Best regards,

Karol
1-9 12:04
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haell
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Sweden
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Hmm, interesting! Would love to have this as an option on the Ronin-S!
1-11 02:28
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