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: Star CN with DSLR Camera
    From: Don Seltzer
    Date: 2016 Jan 29, 09:39 -0500
    NIH offers a free image processing program that may be useful.

    "NIH Image is a public domain image processing and analysis program for the Macintosh. It was developed at the Research Services Branch (RSB) of the National Institute of Mental Health (NIMH), part of the National Institutes of Health (NIH). It has been superseded by ImageJ, a Java program inspired by NIH Image that runs on the Macintosh, Linux and Windows.

    Image can acquire, display, edit, enhance, analyze and animate images. It reads and writes TIFF, PICT, PICS and MacPaint files, providing compatibility with many other applications, including programs for scanning, processing, editing, publishing and analyzing images. It supports many standard image processing functions, including contrast enhancement, density profiling, smoothing, sharpening, edge detection, median filtering, and spatial convolution with user defined kernels.

    Image can be used to measure area, mean, centroid, perimeter, etc. of user defined regions of interest. It also performs automated particle analysis and provides tools for measuring path lengths and angles. Spatial calibration is supported to provide real world area and length measurements. Density calibration can be done against radiation or optical density standards using user specified units. Results can be printed, exported to text files, or copied to the Clipboard."

    Don Seltzer


    On Fri, Jan 29, 2016 at 3:29 AM, Sean C <NoReply_SeanC@fer3.com> wrote:

    Bill and Greg,

    Out of curiosity, I tried using Adobe Photoshop to measure the pixels. It has movable horizontal and vertical guides that I placed on the upper, lower, right and left limbs. I then split the differences between those guides and put two new guides at the center of the square they formed (one vertical, one horizontal giving me a set of crosshairs at the center). Next, I used the convenient ruler tool to measure the pixels from the crosshairs to the horizon. The result after all that: 2,402.5 pixels (apparently PS can acheive sub-pixel accuracy!). Using Greg's corrections, I get an Ho of 22°18.0'; an intercept of 0.9' away. In other words: roughly the same result. ;)

    Cheers,

    Sean C.


       
    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