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gfletcher

Guide Scope/Guide Camera FOV Question

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gfletcher

Hi guys

Can anyone help me work out the FOV  I am getting when I use my guide scope with guide camera?

The kit I have is:

BST 50mm mini guide scope (f3.2) 162mm F.L

With an Altair Astro GPCAMARO130C  guide camera

I am hoping the FOV is between 1deg and 2.5degs

Thanks

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gfletcher

The reason I am asking is that I am having problems when using the polar alignment feature on Shapcap Pro whereby I do not seem able to get to the plate solving stage.

The requirements for using this feature rely on the FOV being between 1deg and 2.5degs.

thanks

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Tweedledee
2 hours ago, gfletcher said:

Hi guys

Can anyone help me work out the FOV  I am getting when I use my guide scope with guide camera?

The kit I have is:

BST 50mm mini guide scope (f3.2) 162mm F.L

With an Altair Astro GPCAMARO130C  guide camera

I am hoping the FOV is between 1deg and 2.5degs

Thanks

With that combination your chip will show a FOV of 1.7 degrees x 1.3 degrees.

 

So should be within your required parameters.

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gfletcher

That’s great,thanks Pete.

At least I know that I am within the parameters.

as a matter of interest, what is the formula for working out the fov?

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Tweedledee

Heres how to work this out with any combination of scope and chip. Just follow the calculations below substituting any new numbers.

Take the focal length of the objective and divide it by a radian (57.3 degrees).

Guide scope BST 162mm FL.
162mm / 57.3 degrees gives an image scale of 2.82mm per degree.

Find your chip size.
Altair GPCAM0130C is 4.8mm x 3.6mm

Divide the chip dimensions by the image scale.
4.8mm / 2.82mm per degree = 1.7 degrees

3.6mm / 2.82mm per degree = 1.3 degrees.

Hope this helps.

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Tweedledee

It's even easier to work out the FOV with eyepieces using the above method because you only need one parameter on the eyepiece - the field stop diameter.

Get the field stop diameter by calculating it, measuring it or by looking at the manufacturers specs. Remember that with some types of expensive exotic eyepieces the field stop is internal, (between lenses) so it can't be measured directly, and you have to calculate or get it from the specs.

Just divide the field stop diameter by the image scale of the scope to get the FOV of the eyepiece.

There are various different ways to manipulate the formulae to work out the parameters you need.

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Bino-viewer

Atik Cameras do a phone app that does the same thing.

I think its free as well.

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