How to calculate the rotation degree of tick marks

[Jber505]

Hello Again,

Thanks to so much help that I received here, I've been able to move right along in learning how to perform my job digitally instead of with an old camera. 

In my last discussion, I learned out to make the tick marks using copies and rotation.  My question now is, how is the rotation calculated so A) I get the correct placement of the tick marks, especially the small ones as there are so many and B) how do I calculate the rotation degree so that I have the proper amount of space at the bottom of the guage/dial?

Here is an image to help show what I'm asking:

I know how to get the large tick marks and the small tick marks, if I were placing them evenly around the entire circle, I would know how to do that also - but since I'm placing them around only a portion of the circle (although still evenly) I'm lost.  I can only figure out the space by hit and miss calculations and that is taking much too long.  I would also need to know how much to rotate the entire thing by in order to get the open space at the bottom as shown.

thanks for your help!

[Grant H]

You need to use transform effects and you can get this in about 10 or so minutes.

first you need to set up the objects.

the thick lines I used effect>distort and transform>transform 20 copies angle 14

thi ones 100 copies angle 2,8

G

[Jber505]

Hello Grant,

Thank you so much.  Yes, I know how to figure out the number of copies that I need.  What I need is how you were able to calculate "angle 14" for the thick lines and "angle 2.8" for the thin ones.  Its the actual calculation of the rotation angle that I need to know.  I would assume it's something like 360/12 or something but I just don't know.

Thanks again.

[Grant H · Accepted solution]

well lets say you want a 90° gap

and need 100 marks. then: 360° - 90° (270) / 100 = 2.7 so copies 100 angle 2.7

and need 20 marks then it will be 270 / 20 = 13.5 angle

G

[Jber505]

Thank you so much! that is exactly what I needed!  I just couldn't figure out the equation, so thank you thank you.