# Where does my (small) notebook go wrong?

Shukie
Hi all,

A few days ago I have done an experiment with a spectroscope to find the value of Rydberg's constant. In my notebook I have a dataset that I want to use a NonLinearModelFit on to find this constant. However, it will not work and I just can't figure out why it won't. I have gotten rid of everything else in the notebook to keep it as clear as possible:

View attachment Notebook1.nb

Could anyone please take a look?

## Answers and Replies

Gold Member
I think the problem is all in your starting points. Do you have a better starting point for "p" than one?
I see that {p,0} or {p,0.027} works:
Code:
fit3 = NonlinearModelFit[
dat1, \[Theta]nul + \[Alpha] + (ArcSin[p k - Sin[\[Alpha]]]), {{p,
0}, {\[Theta]nul, 3.15}, {\[Alpha], 0.}}, k, Weights -> wt]

Shukie
Thanks a bunch, that works indeed!