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M67 Transforms Evaluation

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msheald's picture
Joined: 2010-10-02

Hello! I imaged M67 on 18-April and 1-May with my 8 inch LX200 classic at f6.3 using BVI filters and an SBIG ST-402 camera.

    After using the photometry wizard in MPO Canopus with the same 15 stars from Mr. Henden's field, I obtained the following transforms: 18-April   B=0.529, V=-0.065, I=-0.006

    01-May  B=0.135 V=-0.051  I=-0.017

    The error plots for each night were very close to zero with small standard deviations.

    The transforms for V and I seem close. B seems quite different on the two nights. How much variation should I expect? Thank you and best regards.



Transform error
TCB168's picture
Joined: 2010-07-26

The first B transform seems much too big. I don't have the same camera but use a ST10XME. My B transform is always less than 0.1.

You need to check that the correct stars were selected for the original analysis. Also make a graph of the raw magnitudes from MPO graphing the B-b over the B-V using excel or something similar. The slope of this graph is the transform coefficient. check that the data looks real and isn't just a noisy graph.

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