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Altitude Corrections?
Hi there,
I'm a new member inspired by the recent S&T article to give the E Aur project a shot. I have all the equipment and I should have a good observing window for E Aur in the early a.m. and I'm planning to give it a whirl tomorrow morning.
Q. I'm currently at 8,000 feet and I notice that stars on the horizon are quite a bit better than at home (900 ft) - do I need to do further adjustments or corrections to the intermediate analysis spreadsheet to account for the reduced air mass at this altitude? If yes, then how?
Inquiring minds would like to know!
Clear skies,
Denis Grey.
Hi Denis, I'm glad to hear the S&T article was inspiring. This is the exact effect Tom and I had hoped would happen. Questions like this are also something we hoped we would receive. If anyone is interested in the details, the correction method follows the equations described in Young's "Air Mass and Refraction." I don't have access to the paper from home so I'll have to get back to you on the specifics. From what I recall the fit doesn't include any effects of altitude (it's a six-parameter fit to the zenith angle). Here in Denver we've found the equations in the spreadsheet to be good enough in most instances although I've never gone from 5k ft to less than 1 k ft. Also Idon't normally observe below 20 degrees (sometimes this requires being up very late at night or getting up very early). Tom observes from a few hundred feet (if that much) above sea level and his data appears to be in good agreement with standard photometric methods soI think the error in the air mass at > 20 degrees above the horizon would be less than the internal error due to atmospheric seeing. Perhaps we could devise an experiment to test this and turn it into a publication! Have a good time observing and keep asking good questions! Brian
Hi there, I'm getting Aurigae and Aquila mixed up but the question is still an interesting one... Best, Denis.