![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
Okay. This had better be the last time I go over this particular subtopic. I want to move on!
Now, prime difficulty once you have a scope large enough to resolve the seperated components is the matter of contrast. What you want to do is damp out the overbright starlight (A rhyme! I should be a songwriter) but leave the little ember glow of that darling planet still bright as it can be just an infinitesimal distance to one side. And without building a miror the size of the moon, please. I am not going to be able to process an entire unit's worth of information on optics or electromagnetism in a few days (that is for next semester) so... I leave it to be taken as given for the moment that the telescope size needed at visual wavelengths is about five to ten metres. We already have telescopes this size but not in space. In infrared we would need a scope 20m + in size [what? 100 - 300m is larger than 20] (wavelength is longer therefore we need a larger detector to achieve comparable detector, gain required is lower too but as I do not understand EM well enough to talk about gain I will leave it aside as much as I can).
One thing we can do is use a mask to, um, back up actually. Even though most telescopes do not have sufficient resolution to show stars as anything but a point of light we still have to deal with what is called the Airy disc, the star actually appears as a small fuzzy circle of light. It is surrounded by concentric rings of light of diminishing intensity, fringes produced by diffraction. What we don't want is for the planet to be obscured by the Airy disc, nor to find itself in the midst of a fringe. With the use of an annular pupil mask the first dark ring can be broadened and deepened. Looking at 10 micrometres (that's in the infrared) we would need then a telescope diamater 'only' 20 metres across. If we want to go further we would need to use an interferometer.
Okay, enough. Not as finished as I hoped to be. Tired now, need sleep - up early omorrow and work hard. Good night/day all.
Now, prime difficulty once you have a scope large enough to resolve the seperated components is the matter of contrast. What you want to do is damp out the overbright starlight (A rhyme! I should be a songwriter) but leave the little ember glow of that darling planet still bright as it can be just an infinitesimal distance to one side. And without building a miror the size of the moon, please. I am not going to be able to process an entire unit's worth of information on optics or electromagnetism in a few days (that is for next semester) so... I leave it to be taken as given for the moment that the telescope size needed at visual wavelengths is about five to ten metres. We already have telescopes this size but not in space. In infrared we would need a scope 20m + in size [what? 100 - 300m is larger than 20] (wavelength is longer therefore we need a larger detector to achieve comparable detector, gain required is lower too but as I do not understand EM well enough to talk about gain I will leave it aside as much as I can).
One thing we can do is use a mask to, um, back up actually. Even though most telescopes do not have sufficient resolution to show stars as anything but a point of light we still have to deal with what is called the Airy disc, the star actually appears as a small fuzzy circle of light. It is surrounded by concentric rings of light of diminishing intensity, fringes produced by diffraction. What we don't want is for the planet to be obscured by the Airy disc, nor to find itself in the midst of a fringe. With the use of an annular pupil mask the first dark ring can be broadened and deepened. Looking at 10 micrometres (that's in the infrared) we would need then a telescope diamater 'only' 20 metres across. If we want to go further we would need to use an interferometer.
Okay, enough. Not as finished as I hoped to be. Tired now, need sleep - up early omorrow and work hard. Good night/day all.
