I am not sure about the answer to Would the image circle size decrease if I was able to ditch the Barlow lens?

But if you look at the JavaScript of that page you will see

var sensorw = "Sensor Width"
var sensorh = "Sensor Height"
var maxres  = "Max Res"
var focleng = "Focal Length"

var thisF = sensorw * 3438/focleng;
var thisF2 = sensorh * 3438/focleng;
var thisF3 = sensorw * 3438/focleng * 60/maxres;
var thisF4 = focleng/Math.sqrt(sensorw * sensorw + sensorh * sensorh);


Values:


thisF  = Arc Min of Sky- Width: 
thisF2 = Arc Min of Sky- Height: 
thisF3 = Arc Seconds/Pixel: 
thisF4 = Magnification (X):


This is how that page calculates it

How to calculate the size of the image circle at infinity focus?
I have the following script

&lt;script type="text/javascript"&gt;
    $(document).ready(function(){
        if ($("input[id^='ABCD']").$("input[id$='Z']")) {           
            $("input[id^='ABCD']").$("input[id$='Z']").remove();
        }
    })
&lt;/script&gt;


And I want to remove the elements whose ID starts with "ABCD" and ends with "Z".
How can I do that?
