Spiral search problem with Skywatcher mounts

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admin
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Re: Spiral search problem with Skywatcher mounts

Post by admin » Tue Feb 06, 2018 9:40 pm

Hmm, it would be tricky for the mount *not* to continue if the connection is lost during the spiral search (or for that matter while you have one of the direction keys pressed) - essentially the command that gets sent to the mount is 'move [selected] axis at rate [some multiple] x sidereal', so it does that until it gets sent a stop command. If the connection drops before the stop command then the mount will keep going. I can't see another way around this - there is no ASCOM command to move the axis but only up to a particular position and using GOTO wouldn't work as GOTO movements usually have all sorts of interesting final move in stages that aren't appropriate.

What I'm seeing here though is that perhaps it would be sensible to lock the spiral search out on higher movement speeds (limit to be determined - open to suggestions).

On the subject of the size of the spiral - the movements are fixed in terms of how long each movement runs for, so by selecting different slew rates you will get different spirals.

cheers,

Robin

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Rocket_Guy
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Re: Spiral search problem with Skywatcher mounts

Post by Rocket_Guy » Tue Feb 06, 2018 9:58 pm

With regard to the size of the spirals, I would think that adjusting the size of the spirals based on the camera's FOV would yield an optimum spiral size. Just a thought.

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Re: Spiral search problem with Skywatcher mounts

Post by SteveInNZ » Tue Feb 06, 2018 10:11 pm

I'm fairly new to using ASCOM for mount control so I couldn't say if it is more or less common when doing a spiral search through SharpCap than any other program/means.
Luckily I was doing the spiral at a slow rate. I just remembered seeing this thread so I thought I'd report it.
I see how there's not much you can do at your end if the link has been lost.

With this issue notwithstanding, I wonder if you can offer a more useful spiral search anyway. At the moment, the mount just goes round and round so you get lots of star trails on the screen. Since you have control of the camera, you could create a spiral search that stopped at each corner to take an image. Doing it manually, I would drop the exposure time and crank up the gain and take say a 10 second exposure to look for a fuzzy blob. Once the search is done, reset the camera to useful settings and image. Just a thought.

Steve.

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Re: Spiral search problem with Skywatcher mounts

Post by admin » Tue Feb 06, 2018 10:45 pm

In most cases (if you have a goto mount) plate solving is a better solution for finding your target than spiral search.

Spiral search comes good if you are looking for things in daytime (moon, venus, etc) or have a camera that can't do long enough exposures to plate solve (webcams). In both cases you are usually looking for something bright coming into view and moving quickly through it and hoping you press stop in time.

The trouble is with options like tuning the movement size to the field-of-view is that you then need the program to know the FOV, which means the user has to enter at the least the pixel size and the focal length. Although most people would know their focal length, I'm not convinced that many webcam users would know the pixel size :(

Unfortunately because I have more ideas for improvements to SharpCap than I have time, I have to weigh everything up in terms of questions like: how easy to do? how many people would use it? how much would it improve things? is there a simpler option? In this case I think the locking out of high speeds to limit the chance of equipment damage and suggesting the use of plate solving is the best balance at the moment.

cheers,

Robin

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Re: Spiral search problem with Skywatcher mounts

Post by Rocket_Guy » Wed Feb 07, 2018 2:33 am

You are probably right. Thank you for the responses

All the best, Bill

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