Welcome to the NavList Message Boards.

NavList:

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

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Big fat sunspot and a solar eclipse
    From: Greg Rudzinski
    Date: 2014 Oct 24, 11:02 -0700

    Francis,

    The 400mm telescope should get it done for both eclipse and Jupiter's moons. You should use at least 10 mega pixel digital camera. For image processing I use Adobe Photoshop Lightroom 5.3 and then measure pixels with Windows 7 paint brush tool. Warning-there is a learning curve for getting the most out of Lightroom 5.3 

    If a zoom lens is used then it has to be calibrated for each image. Not convenient. For filtering I use linear polarizers with one of the polarizer filters flipped in the holder so that the pair acts as an adjustable neutral density filter. I'm sure solar film will work on your 400mm telescope objective lens. Start at f22, ISO 100, 1/4000 sec, infinite focus.

    The classic astronomers must have measured realtime with something similar to a theodolite. I'm not sure when photo astronomy first started ...1850s? 

    Greg Rudzinski

     

    From: Francis Upchurch
    Date: 2014 Oct 24, 17:53 +0100

    Thanks Greg,

    It gets better. I already have a good digital SLR and 200mm lens (zoom though ,not prime, does that alter things?) Maybe this ok for lunar eclipses but will probably need telescope for Jupiter moons. My 4 inch refractor also works as a 400mm prime lens, so I guess that would do for both.

    What filters did you use for the 200m? Polariser +/- solar filter, not sure?

    What software to work out the number of pixels?

    How do you think the old guys (eg Cook et al) did it in the 1770s without photography and computers? Did they measure the thing real time with lens objective graticles or whatever they are called? Any information on those? I’ll probably try to do it the old way if I could find out how.

    Anyway, very good fun. Just need the clear weather at the right time.(not easy in wintery, wet and windy  UK. I suspect that is why we sent hundreds of ships south to find clear skies and warm weather.)

    Thanks a lot, I’ll get to work asap on this.

    Francis

     

     

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    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:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    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