Weird default energy binning

[LukasNickel]

The default energy bins here:
https://github.com/cta-observatory/cta-lstchain/blob/main/lstchain/io/event_selection.py#L346

do not match what I would expect:

• Its not 5 (or any n) bins per decade. That would require 5*5+1 = 26 bins instead of 25
• 500 TeV seems excessive. Wouldn't 50 TeV be more than enough?

In [1]: np.geomspace(0.005, 500, 25)
Out[1]: 
array([5.00000000e-03, 8.07799049e-03, 1.30507861e-02, 2.10848252e-02,
       3.40646035e-02, 5.50347086e-02, 8.89139705e-02, 1.43649242e-01,
       2.32079442e-01, 3.74947105e-01, 6.05763829e-01, 9.78670891e-01,
       1.58113883e+00, 2.55448489e+00, 4.12702093e+00, 6.66760716e+00,
       1.07721735e+01, 1.74035029e+01, 2.81170663e+01, 4.54258788e+01,
       7.33899634e+01, 1.18568685e+02, 1.91559342e+02, 3.09482909e+02,
       5.00000000e+02])

Is there any deeper meaning behind these values or was there an error in #1036 ?

[LukasNickel]

Sorry, I got confused looking at the code.
The missing bin edge is added when creating the axes:

cta-lstchain/lstchain/io/event_selection.py

Line 450 in a805812

self.true_energy_n_bins + 1,

In that case only the question about the upper edge of 500 TeV remains.
Why is it fov_edges, but energy_bins?
That is correct, but unexpected

[moralejo]

In that case only the question about the upper edge of 500 TeV remains.

50 TeV would be too low, right? CTA requirements are defined up to 200+ TeV - a different issue is how often we will have observations which go beyond a few tens of TeV, but no need to limit that from the start.

[maxnoe]

50 TeV would be too low, right? CTA requirements are defined up to 200+ TeV - a different issue is how often we will have observations which go beyond a few tens of TeV, but no need to limit that from the start.

How do CTA requirements for the whole array affect the value of the energy migration matrix used for LST mono analysis?

We don't even simulate that high energies

[moralejo]

50 TeV would be too low, right? CTA requirements are defined up to 200+ TeV - a different issue is how often we will have observations which go beyond a few tens of TeV, but no need to limit that from the start.

How do CTA requirements for the whole array affect the value of the energy migration matrix used for LST mono analysis?

We don't even simulate that high energies

I may be missing something here... what is the advantage of setting a low value for the E-axis higher end?
We may not have data, or MC, until the very end of that range, but does it harm to have a safe limit?