Chronos said:It takes a certain number of photons to 'trip' a ccd pixel. Increasing aperature increases the number of photon available per second. Increasing exposure time also increases the number of photons available for capture. An object too faint to 'trip' a pixel with a one second second exposure will not register no matter how many one second exposures you stack.
vociferous said:I
A prominent issue with the aperture and exposure time is not collecting too little photons but too many. If a pixel "well" fills up, it will "overflow" and form lines. That makes it more difficult to use the image because the pixel is generating more flux than you can measure with the CCD.
Creator said:True, but don't the new sensors have anti-blooming protecton to prevent bleed over from overexposure...(or does that reduce the sensitivity substantially) ...and can't it be twarted by proper software ?
Creator
Drakkith said:I believe anti-blooming can cause the photo sites to no longer be linear above a certain value.
Creator said:Yes, I believe you are right, Drakkith; the anti-blooming grids block part of the pixel area and the QE goes down. Apparently the better solution is to "stack" frames of shorter duration using non-anti-blooming ccd. From what I've read, that seems to be most common technique to prevent blooming and still get deeper imaging.
BTW, interesting software you linked to get precise faint magnitudes from images. I always wonder what the price is for these software packages, not usually stated.
Creator
Drakkith said:My own software is AIP4WIN, which is around 100 dollars for the book and software. (The book includes the software) MaximDL is around 300 I think, but includes the ability to control your camera, which AIP4WIN doesn't.
Chronos said:The best CCD cameras are supercooled for this reason. Most of these are simply unaffordable to all but the most dedicated [ie, unmarried] amateurs.
vociferous said:Most of the commercial CCDs have solid-state cooling. The professional ones usually use some kind of liquified gas to keep them cool (obviously at a significant expense and hazard that makes them unsuitable for most amateur applications). If you get the CCD cool enough, you really only have to worry about electrical noise and background radiation from outside the CCD.
The limiting magnitude of CCD imaging refers to the faintest object that can be detected and recorded by a CCD camera. It is determined by the sensitivity and noise levels of the camera and the amount of light available for the object being observed.
The limiting magnitude is typically calculated by taking a series of images of a known reference object with varying exposure times and measuring the signal-to-noise ratio (SNR) for each image. The limiting magnitude is then determined by the exposure time at which the SNR drops below a certain threshold.
The limiting magnitude is affected by several factors, including the sensitivity and read noise of the CCD camera, the atmospheric conditions (such as sky brightness and transparency), and the amount of light pollution in the area.
Yes, there are ways to improve the limiting magnitude of CCD imaging. This can be done by using a more sensitive camera, reducing the read noise through cooling or other techniques, using longer exposure times, and minimizing light pollution and atmospheric interference.
The limiting magnitude of CCD imaging is an important metric in many fields of scientific research, including astronomy and astrophysics. It helps determine the faintest objects that can be observed and studied, and can also provide information about the properties of these objects, such as their size and distance.