sidereal rate on an EQ1?

[GordonCopestake]

I'm trying to use an EQ1 mount for my DSLR taking wide angle long exposures. The 9V motor on the EQ1 has a potentiometer to control the speed of the motor (rather unhelpfully!). Does anyone know at what setting sidereal rate is? Is it the slowest speed? The fastest? Or somewhere inbetween?

[The Warthog]

I'd suggest you follow your star for a while, and use the potentiometer to adjust the speed up or down until it is right.

[geppetto]

That's interesting

Thought they were all crystal controlled nowa days.

Like WH said, tweak till it's right

[GordonCopestake]

problem with that is im not using a 'scope just a camera and i can't see the results until i download them to the laptop. hey ho, just gonna take a lot longer than i thought! the night is young!

[anthony]

Sorry Gordon, can't help (other than wishing you well with the weather)

BUT what is "crystal controlled"

Ant

[geppetto]

BUT what is "crystal controlled

Ant

The speed of the motor has to be accurate to give good tracking.

The best way to achive this is with an electronics board which drives the motor.

The rate at which this board turns the motor is determined by a crystal which has been

cut to work at the correct frequency .

Within reason the motor will turn at a very stable rate due to the stability of this crystal.

[GordonCopestake]

as opposed to non-crystal controlled where the charge in your battery allows the motor to turn at a certain speed which changes as the charge runs out. DOH!

[anthony]

a crystal which has been cut to work at the correct frequency .

With you right up to here! Then all misty.

Ant

[geppetto]

With you right up to here! Then all misty

I've been misty for years

If you get a piece of quartz crystal and stick a voltage across it

it oscillates or resonates at it's own natural frequency.

If you then sand off some of it's thickness, it will resonate at a

different frequency.

So, they work out the correct frequency for the motor driver

and then choose from a range of off the shelf crystals.

Very stable beasties they are. 8)

[anthony]

That has cleared the fog a bit - thanks

Ant