It is currently Sun Dec 08, 2019 2:43 am




Post new topic Reply to topic  [ 6 posts ] 
 Timeismotion: accurately setting the end point of a pan 
Author Message

Joined: Fri Oct 15, 2010 2:00 am
Posts: 3
Post Timeismotion: accurately setting the end point of a pan
Has anyone worked out how to 'land' at a predictable mark?

In the video ( http://www.youtube.com/watch?v=QwDVMs5jEJY ), MIlapse mentions the a couple of bugs, one concerning the accuracy problem in determining the degrees traveled.. it's around the 5:00 minute mark.

If the distance traveled isn't going to be displayed accurately in the software, there has to be a workaround.. Otherwise you're never going to know where the pan will come to rest, which would make the software somewhat unusable. I've been trying to find a way to solve this - would MIlapse or any other good soul have any ideas how to do this?

I tried, using the method below:

1. Choose end point and physically move the head into position there.
2. Now, just using the Timeismotion software to set different combinations of acceleration and deceleration, I do a couple of runs from start to end, at a quick speed of, say, 200 degrees per minute. The start point is almost always less important than the end point - so no worries if it's a couple of degrees off from my ideal start point. As long as the end is accurate!
3. Having established that I can get to the end point I want to accurately, I change the settings in order to slow it all down - the accelerations and decelerations are increased, and degrees per minute decreased by a factor of 10 or more.

... but this method falls down at step 3. Even though I'm not introducing any weird fractions into the equations, (just tried it at a factor of 10) I always miss my end point. Very frustrating. Does anyone have a better approach?

Many thanks in advance.


Fri Oct 15, 2010 2:51 am
Profile
Post Re: Timeismotion: accurately setting the end point of a pan
I wouldn't go so far as to say it's useless... After all it's usually in the ballpark ;)

Here's why I think it'll never be dead on: when you accelerate and decelerate using TIM you're essentially 'forcing speed shifts' many many times. Each time you shift from one speed to another you introduce slight errors. That's to say the software can't know the distance traveled 'between' one speed and the next because it's blind (it has no feedback from the encoder wheel). It can only guess in the dark.

The TIM exploration was interesting and fun for me but at the end of the day you may start to understand why it's dead in the water. It's not a solution, it's simply an attempt.

All that being said... what you should look forward to is shutterdrone's upcoming tutorial where he's going to show how the MX2 can be attached directly to telescope heads and get feedback from the encoder. This is where it gets interesting because if the software can get feedback, it can make sure the head hits its mark. ;)


Fri Oct 15, 2010 4:56 am

Joined: Fri Oct 15, 2010 2:00 am
Posts: 3
Post Re: Timeismotion: accurately setting the end point of a pan
Hi Jay,

Thanks for the quick response. Love the look of the Dynamic Perception gear, but I've just spent 500 dollars sourcing bits and pieces from all over to get to this stage, so I want to get the best out of it that I can.

Currently, the amount that it's going out is quite severe - what the software tells me will be a 72 degree turn ends up at 90 or 110 degrees depending on the speed. Maybe I put in too many speed gradations - 99. I'll try reducing those to 50.


Fri Oct 15, 2010 9:36 am
Profile

Joined: Tue Oct 05, 2010 10:06 pm
Posts: 16
Post Re: Timeismotion: accurately setting the end point of a pan
I usually get it spot on using the same method. Just do a realtime move and then scale it proportionally. Just got to make sure that you scale your time up equally as much as you scale your speed down.


Sun Oct 17, 2010 5:53 pm
Profile

Joined: Fri Oct 15, 2010 2:00 am
Posts: 3
Post Re: Timeismotion: accurately setting the end point of a pan
Grif, glad to hear you've had success with this method. How many acceleration/ deceleration steps do you use?


Sun Oct 17, 2010 7:09 pm
Profile

Joined: Tue Oct 05, 2010 10:06 pm
Posts: 16
Post Re: Timeismotion: accurately setting the end point of a pan
havent been on in a while, to answer your question more is better as long as they're identical.


Tue Nov 09, 2010 10:49 pm
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © phpBB Group.
Designed by Vjacheslav Trushkin for Free Forums/DivisionCore. pozycjonowanie