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Unexpected full speed slew during dithering


Franky

Question

Hi guys,

I am using Backyard Nikon 2.0.2, Mountain instruments MI-250 mount (using Gemini Level 4 GOTO), connected to my computer via RS232 cable (thru USB adaptor). I use ASCOM Gemini telescope .NET driver. I also use DSUSB to trigger the bulb shutter.

When I use dithering, Backyard Nikon takes a few shots as expected - capture, download, dither, waiting, capture, and so forth. However, after 5th or 6th shot, the usual dithering move triggers sudden full speed slew and the mount rotates in RA until it reaches it's safety limits.

I tried another RS232-USB adapter with same result.

I have very similar issue with direction buttons in the "ASCOM Telescope" area. Sometimes, when I click one of the RA buttons, it moves just slightly and then stops. It just makes kind of "step" move. Other times, when I click one of the RA buttons, in the very same way as before, it starts fast slewing, and goes until it reaches the safety limits.

This issue makes the dithering function unusable for me.

What could be causing these problems, please?

Thank you,

Frank

 

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HI Guylain,

I was wrong when I've told you, that this issue happens in different positions of RA axis. I was testing this in garage and moved the telescope by hand - what I did not realize is that Gemini did not know I moved the RA axis, so she thought it is still looking at the polaris at counterweight-down position.

So the fast slew really happened because I was at the meridian at all times and gemini could not reach the new coordinates from where it was. See attached picture.

I tested it today by moving telescope to different part of the sky with hand controler and I was able to make 100 exposures without any problems.

Sorry for misleading information.

Frank

dithering.jpg

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Guylain asked if you were using PHD or direct mount dithering. Choosing ASCOM is for direct mount dithering.

This is also known as unguided dithering, since you are not using autoguiding. BYN supports dithering with PHD, PHD2 and MetaGuide autoguiding apps. Direct mount dithering can only be used when you are imaging without autoguiding.

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1 minute ago, astroman133 said:

Guylain asked if you were using PHD or direct mount dithering. Choosing ASCOM is for direct mount dithering.

This is also known as unguided dithering, since you are not using autoguiding. BYN supports dithering with PHD, PHD2 and MetaGuide autoguiding apps. Direct mount dithering can only be used when you are imaging without autoguiding.

I am imaging without autoguiding, that's why i'm using direct mount dithering :-)

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Ok, I'll have to do more tests.  Looks like a bug but I'm not sure yet.

The direct mount dithering works by issuing a goto to a close coordinate.  Your mount and PC time are all the same? Daylight savings time?  Is the moving about 15 degrees or does it always go all the way until it reaches limits.  I actually developed this feature for myself as I use a 10 Micron mount and I don't guide either... but my OTA is in Italy for repair this winter so I have not been doing any imaging for several months so this feature did not get much visibility from me lately.

Regards, 

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8 hours ago, Franky said:

HI Guylain,

I was wrong when I've told you, that this issue happens in different positions of RA axis. I was testing this in garage and moved the telescope by hand - what I did not realize is that Gemini did not know I moved the RA axis, so she thought it is still looking at the polaris at counterweight-down position.

So the fast slew really happened because I was at the meridian at all times and gemini could not reach the new coordinates from where it was. See attached picture.

I tested it today by moving telescope to different part of the sky with hand controler and I was able to make 100 exposures without any problems.

Sorry for misleading information.

Frank

dithering.jpg

Thank you for letting us know and no worries.

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