Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Latitude by photo
    From: Frank Reed
    Date: 2020 Aug 7, 13:16 -0700

    Robin, you wrote:
    "Altair stands out to left of centre and its identity is confirmed by Sagitta and Delphinus above.
    Having just gotten power back after nearly 3 days since Tropical Storm Isaias

    Yikes! This storm mostly missed us here in eastern New England. Winds here topped around 25mph steady, and we had a little torrent in the late afternoon, but it only lasted twenty minutes. Power was out for a while at the center of the island but not here at the south end. Just 40 miles west of here in the Noank-Mystic area, conditions were considerably worse with some significant wind damage. I understand some people are still without power further west and into New Jersey and New York.

    Regarding the image, I was surprised that Sagitta was so clearly visible, given the lighting conditions. The limiting magnitude is somewhere around 4.5, which isn't bad, considering. The altitudes of Altair and Vega are clearly key. And it's also nice that we can determine the location of the true horizon. In fact, given that this is a modern building, we can assume it's aligned with the compass points. Extending the floorlines to their crossing point takes us to true altitude 0° and, as it turns out, true azimuth 270°. In addition to latitude and Sidereal Time, I believe it's also possible to pin this image down to the nearest day. If we assume the image was created within the past ten years, which is almost certain, then we need the Moon or a planet to get the date. On the extreme left of the image, right where the ecliptic would be crossing, there's something bright. I think I have it figured out, but I am curious to see what others come up with.

    A little trivia: there are two historical "lunars" stars in this photo. There's Altair, of course. And on the left, there's Beta Capricornii, which was one of Maskelyne's lunar stars in the earliest editions of the Nautical Almanac. 

    Frank Reed

    PS: If you want to skip the astronomy to determine the latitude in this image, hit Google with "colorful hotel". How many clicks to latitude and longitude?!

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site