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Hi,

I used to use IRAF for reduction but didn't use it for a long time. I have noticed that the findgain task is moved into obsutil package. Does this mean that there is another task, doing similar thing like findgain, which is not obsolete?

*help findgain* explains , that findgain requires 2 dome flat-fields and 2 biases. Is it posible to use twilight flats and under what condition?


Thanks
o.

The OBSUTIL package simply means "observing utilities", not 'obsolete" (that's for the OBSOLETE package itself). Nothing has changed about the task other than the location, unfortunately I can't answer the question about the suitability of twilight flats.

thanks for reply.

I tested a bit the FINDGAIN on real data and I am not sure how to understand the result. I took a sequence of dome flats with increasing exposure time. At each exposure time I shot 2 images one after another. The central value of a pair is pretty much the same because the light is stable. I run the FINDGAIN with pairs of dome-flats. This is the outcome:


#expTime aveLevel_Cent100 aveSigma_Cent100 gain RON
5 12138 108.9 1.03 10.86
8 18458.5 136.55 1.16 12.18
11 24523.5 162.95 1.12 11.83
15 33725 1 97.9 1.18 12.38
18 39789 218.15 1.22 12.8

The *aveLevel_Cent100* is the mean of the pair's central (average of 100x100 pixels) values. *aveSigma_Cent100* is just the corresponding stddev.

Is it possible that the gain and RON depend on screen intensity level? Actually I have an increasing trend here. ...

if you have info about the paper where Janesick describes the method would help also ... thanks