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John Coffin's picture
Last seen: 5 months 1 week ago
Joined: 24/10/2017 - 13:58
Further investigation, mixed method v calibration lamp only

The best fit for Z And was when the only frame taken after the meridian flip was used, and it was calibrated using the mixed Balmer and lamp method. The Balmer lines were found from Pi And (also taken after the flip).

The lamp was the one taken for Z And, after the flip. No heliocentric or corrections for radial velocity were made.

The errors were 

H alpha                 -0.4

H beta                   +0.65

H gamma             +1.2

H delta                  +1.0

 H epsilon             -1.0

When the same frame was calibrated using its lamp lines only and not the Balmer lines from Pi And

Errors are:

H alpha                 -0.4

H beta                   -1.45

H gamma             -1.8

H delta                  -2.5

H epsilon             -3.5

So for me it seems the mixed method gave the best results 

Robin Leadbeater's picture
Last seen: 16 min 23 sec ago
Joined: 05/03/2014 - 00:50
lamp now ok at H alpha

Hi John,

OK so comparing with the errors you had at the start of the thread it looks like you now have a good calibration across the range, including at H alpha where ISIS only uses  lamp lines.  We still do not understand why the lamp gives increasing errors towards the blue end but I think we should probably accept this as a win for now !