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Henden Fields for Extinction and Zero Point Calculations?

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Henden Fields for Extinction and Zero Point Calculations?

Hello! I was wondering if it would be appropriate to use Henden fields for nightly extinction and zero point values? Since I reside at latitude -24 degrees, a number of the fields pass directly overhead. I would use Landolt standards for transforms.

    Thank you for your guidance. Best regards.


HQA's picture
Henden fields

Hi Mike,

I presume you mean the fields that were calibrated at NOFS, and available through Seqplot (or perhaps the Henden/Sumner sequences)?  Stick with those that have a minimum of three nights of observation if you use them.  There are some potential systematics with using such fields for all-sky calibration, especially since -24dec fields at NOFS transit the meridian at airmass 2.5 or so.  If you are determining extinction so that you can correct the differential extinction across a field of view, then the NOFS data should be fine.  If you are using the fields to calibrate other fields, then you may get ~0.03mag offsets from the truth.

There are some useful Landolt fields that get close to overhead for you, such as PG 1323.  There is a Landolt paper with well-calibrated stars over a wide declination range that tends to get overlooked:  1983AJ.....88..853L which I recommend.


Thank you! I downloaded the

Thank you! I downloaded the paper you recommended.

    Thank you for your guidance regarding the Henden NOFS fields. I appreciate it. Best regards.



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