Hello all from Italy.
I am studying (for UNI) a few stars in the M71 globular cluster, using Astro Image J.
The files received were a few lights (in H and K bands, near IR) and a few calibration files.
The calibrated fits files are not ideal, more data should be needed, but for the scope of the assignment it's ok.
Now, I have performed the relevant studies in AIJ, and I got my instrumental magnitudes (H and K) with their own zero points (from the observatory data).
I have been asked to create a H-K colour-magnitude diagram (with their errors), so I worked out errors in H and K bands respectively, although I am not sure about the calculation:
mag error = -2.5 Log(1 + 1/SNR)
The H-K magnitudes are calculated simply by H mag - K mag (right?).
So, if I have H-error and K-error, then the H-K error is = SQRT(H-error^2 + K-error^2) , correct?
Plus, for the colour-magnitude diagram: would you choose H vs (H-K) or K vs (H-K) ?
Many thanks in advance for your insights.
Best regards,
Mauro B.