L'avantage des gros tubes, c'est aussi un plus fort grossissement car une focale plus longue, j'ai tort?
Moi, j'ai fait le contraire mais pour d'autres raisons: les gros tubes sont lourds et pas faciles à ranger
et puis
j'aime avoir du champs aussi
J'ai aussi une réponse là:
https://diffractionlimited.com/how-to-c ... ng-camera/
Je recopie:
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The first thing to consider is resolution: how much of the sky does each pixel see?
Smaller pixels will give you higher resolution, but they’ll also see less sky and collect fewer photons. In that respect, having a larger pixel is much like having a faster focal ratio. But if you make the pixels too large you’ll have little square stars—and your resolution will be very poor.
It turns out that you need to match your camera’s pixel size to your telescope’s focal length. Use this simple formula:
Pixel Size (arc-seconds) = 206 * pixel size (microns) / focal length (mm)
At premium mountaintop observing sites, atmospheric seeing limits your resolution to around 1 arc-second (usually measured as Full Width Half Maximum, or FWHM). Only the best sites like Mauna Kea can provide sub-arc-second seeing. If you are not on a mountaintop, your typical seeing is likely 2 to 3 arc-seconds.
Let’s assume you want good resolution for the best nights, when your seeing disk is 2 arc-seconds FWHM. (SBIG cameras come with MaxIm LT software, which can measure this for you.) The Nyquist Sampling Theorem tells us that for maximum resolution you need 3 pixels across the FWHM. Therefore, at 2 arc-seconds you need a pixel size that gives you around 0.7 arc-second sampling. You will want to select a camera that gives you 0.5 to 0.9 arc-seconds with your telescope.
This table will save you the trouble of finding a calculator:
- Screen-Shot-2020-07-07-at-9.55.07-AM-488x800.png (265.34 Kio) Consulté 2930 fois
As an example, if you have a telescope with a 3000 mm focal length and seeing around 2 arc-seconds FWHM, then the table shows that you ideally want a pixel size in the 7 to 9 micron range.
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