Observing Advice

Until further notice we suggest that users on FTN double their planned exposure times for all colour (BVR) observations to help increase their image quality.

The old CCD camera which was on FTN had good response across all optical wavebands. However, the new CCD camera that has been installed on FTN has a poor blue response (i.e. it is not very sensitive in the blue end of the spectrum), and the B band images are particularly affected by this.

For FTN users this means that, for example, a 15s exposure of a globular cluster would have very few counts and look very noisy in the B band, as shown below for the image of NGC 2419 in B, V and R.

B	V	R

For an approximate solution, doubling the exposure time will double the counts on the CCD, thereby decreasing the noise in the images.