With the addition of new Models, specutils has started to become a very useful tool. This time, I have added Doppler WCS, Weighted Combination WCS, and Serial Composite WCS. These WCS'es, along with the previously implemented Polynomial, Legendre, Chebyshev and Bspline models enable the user to make very complicated functions with simple building blocks.
Doppler WCS - This model applies doppler shift to the input. Instantiates the doppler shift model from the velocity (v). The doppler factor is computed using the following formula:
Weighted Combination WCS - This model combines multiple WCS using a weight and a zero point offset. Suppose there are n WCS'es. When called with an input, this WCS returns the following:
Serial Composite WCS - This model applies multiple WCS in-order to a particular input. Suppose there are 4 WCS'es, When called, this WCS returns the following:
The last two models, can be used to construct complicated WCS'es just by adding simple models. Even function pointers can be added to these WCS'es making them very flexible and useful.
Apart from these models, specutils now supports reading and writing multispec linear and log-linear formats as well. The IRAF classes were redesigned to use these building blocks, making the code more simpler and elegant. The next focus will be on implementing the slicing operations onto these models, and enabling transformations from one model to another.
Doppler WCS - This model applies doppler shift to the input. Instantiates the doppler shift model from the velocity (v). The doppler factor is computed using the following formula:
doppler factor = sqrt((1 + v/c)/(1 - v/c))
,where c is the speed of light
When the model is called on an input, input * doppler_factor is returned. The inverse of this model can also be obtained, which divides the input by the doppler factor. The Doppler shift model can also be instantiated from redshift(z) and the Doppler factor itself.Weighted Combination WCS - This model combines multiple WCS using a weight and a zero point offset. Suppose there are n WCS'es. When called with an input, this WCS returns the following:
Sum over i = 1 to n
[weight_i * (zero_point_offset_i + WCS_i(input))
WCS can be added using the add_wcs method, along with it's weight and zero point offset.Serial Composite WCS - This model applies multiple WCS in-order to a particular input. Suppose there are 4 WCS'es, When called, this WCS returns the following:
wcs_4(wcs_3(wcs_2(wcs_1(input))))
The WCS which is added first is applied first. WCS'es can be added using the add_wcs method.The last two models, can be used to construct complicated WCS'es just by adding simple models. Even function pointers can be added to these WCS'es making them very flexible and useful.
Apart from these models, specutils now supports reading and writing multispec linear and log-linear formats as well. The IRAF classes were redesigned to use these building blocks, making the code more simpler and elegant. The next focus will be on implementing the slicing operations onto these models, and enabling transformations from one model to another.
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