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Dithering for Unguided Imaging Question


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I want to use this during wide field imaging on my Losmandy StarLapse mount between subs. 

 

Since your Tracking Mount has a Drive Motor for ONLY the RA Axis, any Dithering will ONLY occur in the RA Axis.

 

The BYE/BYN ASCOM Dither Feature simply directs ASCOM to perform a "Minor" Random Move at the point between Image Exposures (and then pauses a few seconds to allow the Mount to "Settle").

Even if BYE/BYN requests a Move that has BOTH RA and DEC components, your StarLapse Mount will ONLY move in the RA Axis where its drive motor has the capability (the DEC component will be Ignored).

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For any efforts to Dither, the User needs to have the PC connected to the Mount:

Usually this is via either ASCOM or the Guiding Software - PHD / PHD2 / MetaGuide.

 

This Thread is about the BYE/BYN ASCOM Dither feature, so ASCOM is Required.

 

This is 110% true.  Very good advice.

 

Dithering is a function of the mount, not the camera... so if the mount is not connected to the computer via ASCOM there is 0% chance of dithering because there is no way to communicate with the mount and tell it to move a few pixels in a random direction.

 

Regards,

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The Losmandy StarLapse unit comes with a small hand controller / RA dive unit.  I ordered the StarLapse with the G8 motor controller so I can do dithering.  It looks like there are no plug-ins for Losmandy mounts.  If necessary I can auto-guide but the P.E. no my mount is very low and I shoot under 200mm so auto-guiding isn't really necessary.  I just want to make RA only dithering corrections.  What are my options?

 

If necessary I can code a program to issue regular RA dithering corrections and time it so its sync's with BYE but auto-guiding may be simpler.  

 

Jim

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I am not quite sure what you mean by "no plug-ins for Losmandy mounts"? Do you mean that there is no ASCOM driver? If so, I believe that you are correct. Losmandy mounts typically use the Gemini GOTO system for computer control. The Gemini controls the mount and provides the hardware interface(s) for a computer connection. There is a Gemini ASCOM driver, so if you had a real G8 or G11 with Gemini GoTo system you could do unguided dithering from BYE through ASCOM and the Gemini.NET driver.

 

How do you, or can you, connect the StarLapse tracker to a PC or guide camera (ST-4)? That physical connection is necessary, regardless of what software is used. If you wrote a program to do RA dithering, how would the movement command get to the tracker with out the tracker and the PC being connected via a serial or USB connection?

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I can't find any ASCOM drivers or plug-ins for Losmandy mounts.  The StarLapse is 1/2 of a G8 mount - RA only.  I am driving the mount with the standard G8 motor controller box and not a Gemini.  The standard G8 and G11 motor controller boxes have an auto-guider port - ST-4 port.  I can do RA only guiding or dithering with my StarLapse.

 

It may be simpler just to do actual auto-guiding with my StarLapse but the extra weight is a concern.  I would need at least a 60mm guide scope and a sensitive auto-guider.

 

BTW - I do auto-guiding / dithering on my CGEM DX mount.

 

Jim 

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OK, I believe that you are correct.

 

1) that there is no ASCOM driver for Losmandy mounts without a Gemini.

2) if you have a guide camera with an ST-4 port then you can dither the StarLapse from some autoguiding app, like PHD2.

 

Actually, you could guide without the need for a 60mm guide scope. It may be more pricey than you are expecting, but check this out --> https://www.sbig.com/products/cameras/specialty/st-i/st-i-guiding-kit/.

 

You can purchase a lens that attaches to the front of an SBIG STi guide camera that eliminates the need for a full-blown guidescope. Note that the STi is purchased in addition to the guiding kit.

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Yes - I have been looking at the SBIG guide setup.  Its pricey but small and light weight.  I haven't seen many reviews on the setup but I will look again.

 

BTW - I currently use PHD2, Orion SSAG and 60 or 80mm guide scopes.  Thanks all.

 

Jim

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On 1/30/2018 at 8:22 AM, admin said:

I tweaked the values several times over the last few years.  What version on BYE are you using?

IT IS THE LATEST UPDATE.  i AM NOT USING A GUIDE CAMERA JUST RUNNING PHD.  NOT SURE WHY I EVEN TRIED IT BUT IT WORKS GREAT.

 

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You say that you are "running PHD", but what is it doing?

You also said "I loaded PHD and connected it and what do you know. works great". What did you connect it to? the mount? How is it "working great"? PHD cannot work at all without a guide camera.

If you don't have a guide camera then PHD cannot be guiding since it cannot calibrate the guiding without a camera. If PHD is just executing, but in an idle state, and you have selected ASCOM dithering in the BYE settings, then BYE should not be interacting with PHD when BYE is doing unguided dithering and PHD cannot be affecting dithering either.

I am confused. Please provide more detailed information about what you are doing and what you are seeing.

Thanks

 

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Probably, but if he selected PHD in the setting then there was no dithering.  I suspect this is what he did and -assumed- it was working since the large movement were gone... in fact there was no movement at all if this was truly the case.

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sorry running 3.1.16  I am not guiding and was attempting to use ASCOM dithering.  When I select ASCOM dithering the scope makes large swings.  When I set to PHD in the dithering section and start the PHD program it settles down and makes the correct adjustments. I can watch the movement on the grid display.  I know it makes no sense but it works.  I will try it again, with ASCOM selected,   when I get a good night and let you know what happens.

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I guarantee you it does not work... I programed it.  If you select PHD then you must be guiding for dithering to work... this is because PHD *is* doing the dithering, BYE simply tells PHD to dither and for PHD to dither it must be guiding first... these 2 go hand in hand.

Regards,

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danl1223,

You should get confirmation from the PHD2 developers/users whether it is possible to dither when no guide camera is connected, but a mount is connected via ASCOM.

I tried to duplicate what you are describing by connecting PHD only to an ASCOM mount and what I am seeing is that without PHD being connected to a camera, the guiding history graph stays empty. Also, the Looping and Guiding buttons are disabled. BYE does send dither commands to PHD2 and resumes imaging after the Settle Time has elapsed. This is what I would expect. PHD does not and cannot dither without a guide camera AND having its guiding functionality active.

There must be something that you are not telling us about what you are doing and what you are seeing.

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1 hour ago, astroman133 said:

You should get confirmation from the PHD2 developers/users whether it is possible to dither when no guide camera is connected, but a mount is connected via ASCOM.

This is interesting... it sounds plausible.... but only the PHD team can confirm this.

 

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