Ocular : help file unclear

An example is given here, and the answers, though working, are not very convincing.

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3901754/page/0/view/collapsed/sb/5/o/all/fpart/1

We really need a formal explanation on the maths behind the figures to enter in Ocular to simulate the DSLR properly.

Best regards

Fred

AFAIK, the plug-in's page in the Stellarium Wiki has been updated recently:
http://www.stellarium.org/wiki/index.php/Ocular_plugin

If you can't find useful information on that page, the only other options are to wait for Timothy Reaves to answer or to look at the plug-in's source code yourself.

The answer of Bogdan just tells me that I should better try to find a solution by myself than asking to the community !

I'm really sorry for the disturbance my message has caused to you.

"The answer of Bogdan just tells me that I should better try to find a
solution by myself than asking to the community !"

This is not a forum, it's support system in questions/answers format,
so the only community here is (some of) the Stellarium developers that
are subscribed to the tracker and any other users that can bother to
provide an answer. There's no unseen audience.

There is a more traditional Stellarium "forum" at SourceForge, but
it's awkward and not very active:
http://sourceforge.net/projects/stellarium/forums/forum/278769

Also, you are giving up too early. My answer is not definitive. Wait
for Timothy Reaves.

Wasn't there anything useful in the Stellarium Wiki page?

"I'm really sorry for the disturbance my message has caused to you."

If you are talking to me*, then be assured that your message has
caused no disturbance. The Q/A section is precisely for asking for
information, and, occasionally, feedback.

* "You" is a tricky word.

At least I found a bug by checking the source code as Bogdan advised me. It is in the CCD.cpp file :

float CCD::getActualFOVx(Ocular *ocular)
{
 float FOVx = (chip_width * 206.265) / ocular->getEffectiveFocalLength();
 return FOVx;
}

float CCD::getActualFOVy(Ocular *ocular)
{
 float FOVy = (chip_height * 206.265) / ocular->getEffectiveFocalLength();
 return FOVy;
}

Here, the factor 206.265 is not adequate. The formula used is for the sampling of the pixel :

sampling (in arc. sec) = 206.265 * pixel width (µm) / telescope focal length (mm)

The right exact formula for the field of view of the CCD shall be :

FOVx (arc. min) = 2 * atan(chip_width (mm) / (2* telescope focal length (mm)) * 180 / pi() * 60
FOVy (arc. min) = 2 * atan(chip_height (mm) / (2* telescope focal length (mm)) * 180 / pi() * 60

This formula can be simplified :

FOVx (arc. min) = 6875.5 * atan(chip_width (mm) / (2* telescope focal length (mm))
FOVy (arc. min) = 6875.5 * atan(chip_height (mm) / (2* telescope focal length (mm))

It can even be further simplified if chip size << telescope focal length, but to allow the use of DSLR lenses the above formula would be better.

FOVx (arc.min) = 3437.7 * chip_width (mm) / telescope focal length (mm)
FOVy (arc. min) = 3437.7 * chip_height (mm) / telescope focal length (mm)

Fred

Don't answer to the above message. I copy it to the bug section.