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Author Topic: Tracking rate  (Read 5083 times)

Smokie

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Tracking rate
« on: November 24, 2015, 15:32:02 »

Hello Tom,

I have a question

I use version of V1.28k EQMOD
Configuration AstroEQ see Annex 1
Cartes du Ciel V3.10

As I measure the sidereal tracking it is not what I think it should be (+ - 15 degrees in one hour)but
+- half  the value
Changing values in the AstroEQ configuration does not alter the tracking of my mount
Can you do me a suggestion where to look for a solution?
Thanks
Gr,Henk
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TCWORLD

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Re: Tracking rate
« Reply #1 on: November 25, 2015, 21:11:10 »

Hi Henk,

Are you sure about all the gear ratios? If it is a factor of 2 out, either the ratios are out in what you've entered, or possibly the motor step angle. There is a remote possibly one of the motor driver mode pins is not correctly soldered (so the drivers end up in the wrong mode) - you can test this by seeing if the DEC motor moves at the correct speed.
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Tom Carpenter (AstroEQ)

Smokie

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Re: Tracking rate
« Reply #2 on: November 25, 2015, 22:01:42 »

Hello Tom,

thanks for the respons

ratio's are ok,Slewing  the mount with the arrows of control  of EQMOD is going well
the sidereal tracking , however , is too slow
the only way to change this that I could find is to use the customized tracking button
by placing RA on 25 and DEC on 0 I approach the Sideral tracking rate of my mount about
(+- 15 degrees per hour)

il test switching the DEC motor/RA motor tomorrow

Gr,Henk
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Smokie

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Re: Tracking rate
« Reply #3 on: November 26, 2015, 13:14:39 »

a next day of testing!  :)

I have also asked my question on EQMOD forum
Chris his reaction was to look in the same direction as you pointed:

“You shouldn't have to use the custom tracking button to move at sidereal. If gotos work fine but trackig doesn't then It sounds to me as though there is something wrong with the ASTROEQ configuration settings - specifically the sidereal speed or "iVal" parameter. This value is read by EQMOD on startup and is the value written back to ASTROEQ whenever the mount is commanded to move at sidereal rate. You may need to post for help on this on the ASTROEQ support forum.”


I have a wormwheel  homemade (photo)
it is an aluminum wheel / 120mm round with thread M12x1. 75 ,powered with a M12x1.75 thread
my calculation was: circumference 118x 3.14 divided by 1.75 pith =211
so I used 211 :1 in the AstroEQ configuration
motor shaft 15 T/ worm shaft 40T(2.666)
Result: sidereal  speed too low

This morning I have tested: 367: 1(3,14x117)
Result: sidereal speed right!!
I do not understand exactly what is wrong with my calculation :-\ but glad
It’working!!
There is a warning in the configuration
Tom ,can you explain to me what this means?

Gr,Henk
« Last Edit: November 26, 2015, 14:35:32 by Smokie »
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TCWORLD

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Re: Tracking rate
« Reply #4 on: November 26, 2015, 15:04:47 »

The warning is basically saying that the aVal is very high which results in an IVal which is small.

Because the IVal determines speed at sidereal, when EQMOD sends a different speed, IVal will be divided to make it - e.g. for 2x speed, EQMOD will request IVal/2 speed. For 4x it will be IVal/4.

If the IVal is small it means there are fewer values of speed that can be sent (as there are less numbers in the range 1 to IVal).

It shouldn't be an issue unless you start wanting to use the custom tracking feature in EQMOD to track very high speed objects. But to be honest I can't see that happening (trying to get the scope lined up on an object moving quickly and getting tracking going is probably impossible). For that reason the IVal is optimised to get the most accurate sidereal rate (by minimising integer rounding effects on the various calculations) as it is the most important speed.

You could try going down to 1/16th microstepping instead of 1/32th, which would increase the IVal, but the overall resolution of the mount would drop.
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Tom Carpenter (AstroEQ)

Smokie

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Re: Tracking rate
« Reply #5 on: November 26, 2015, 16:25:40 »

Hoi Tom,

i need some time to figure that out  ???, but like i said it's working oke so

im verry glad

Thanks again for the great help

Gr,Henk
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