Guiding Error

[Scooot]

Hi all,

I wonder if someone could explain something that’s been bothering me. I’m currently guiding and my right ascension is 0.71”, my Dec is 0.43” and the total error is 0.83”. Can anyone explain how the 0.83” is calculated from the RA & Dec figures? See the screenshot below. It’s not that important but I’m just curious.  

Edited October 8, 2021 by Scooot

[iantaylor2uk]

It’s the root mean square, so if you square the RA value and add it to the square of the DEC value, and then take the square root, that should be the final guide error.

[Scooot]

Great, many thanks Ian. 

[vlaiv]

Alternative explanation would be - addition of vectors.

Think school math problem with vectors - like adding of velocities.

You are moving left at 0.71 and moving up at 0.43 - what is your total speed?

[Scooot]

1 minute ago, vlaiv said:

Alternative explanation would be - addition of vectors.

Think school math problem with vectors - like adding of velocities.

You are moving left at 0.71 and moving up at 0.43 - what is your total speed?

Thank you Vlaiv, I’m sorry to say I don’t remember Vectors from maths but I’ll look it up. 

[Scooot]

7 minutes ago, vlaiv said:

Alternative explanation would be - addition of vectors.

Think school math problem with vectors - like adding of velocities.

You are moving left at 0.71 and moving up at 0.43 - what is your total speed?

Ah, thinking about that it’s Pythagoras, it’s all clear now. Thanks for the hint.