photometry#
Methods for performing photometry / measuring fluxes.
- hsr4hci.photometry._gaussian_integral(amplitude, sigma, radius=0.5)[source]#
This function compute the following integral:
\[\int_{0}^{R} dr \int_{0}^{2\pi} d\phi \ r\ A e^{-\frac{r^2}{2\sigma^2}} = 2 \pi A \sigma^2 (1 - e^{-\frac{R^2}{2\sigma^2}})\]This function can be used to turn the results of the fit of a 2D Gaussian into units that are compatible with aperture photometry.
- hsr4hci.photometry._get_flux__as(frame, position, aperture_radius)[source]#
Auxiliary function to measure the flux using the “AS” mode. See
get_flux()for more details.
- hsr4hci.photometry._get_flux__ass(frame, position, aperture_radius, search_radius)[source]#
Auxiliary function to measure the flux using the “ASS” mode. See
get_flux()for more details.
- hsr4hci.photometry._get_flux__f(frame, position, mask_frame_radius=5.0)[source]#
Auxiliary function to measure the flux using the “F” mode. See
get_flux()for more details.
- hsr4hci.photometry._get_flux__fs(frame, position, search_radius, mask_frame_radius=5.0)[source]#
Auxiliary function to measure the flux using the “FS” mode. See
get_flux()for more details.
- hsr4hci.photometry._get_flux__p(frame, position)[source]#
Auxiliary function to measure the flux using the “P” mode. See
get_flux()for more details.
- hsr4hci.photometry.get_flux(frame, position, mode='AS', aperture_radius=None, search_radius=None, mask_frame_radius=5.0)[source]#
This function estimates the flux at or around a given position in a frame. There are five different modes for how to do this:
- “AS” (aperture sum):
Compute the integrated flux over a circular aperture with radius aperture_radius at the given
position. This is perhaps the most “intuitive” way to compute the flux.
- “ASS” (aperture sum + search):
Similar to “AS”, except the position of the circular aperture is varied in a circular region with radius
search_radiusto find the position with the highest flux.
- “P” (pixel):
Compute or interpolate the value of a single pixel at the given
position. (Internally, this simply uses an aperture with a diameter of 1 pixel.)
- “F” (fit):
Compute the flux by fitting a 2D Gaussian to the given position and returning its
amplitude.
- “FS” (fit + search):
Similar to “F”, except the position of the 2D Gaussian is also optimized within the given
search_radius.
- Parameters:
frame (ndarray) – A 2D numpy array of shape (width, height) containing the data on which to run the aperture photometry.
position (Tuple[float, float]) – A tuple (x, y) specifying the position at which to estimate the flux.
mode (str) – Either “AS”, “ASS”, “P”, “F”, or “FS” (see above for a detailed explanation).
aperture_radius (Optional[Quantity]) – Required for modes “AS” and “ASS”. Defines the radius of the circular aperture over the flux is summed up / integrated.
search_radius (Optional[Quantity]) – Required for modes “ASS” and “FS”. Defines the size of the region within which we vary the position to find the “optimal” (= highest) flux.
mask_frame_radius (float) –
For modes “F” and “FS” (i.e., the modes that are based on fitting a 2D Gaussian to the data), we use a mask to set pixels to zero that are further away from the
position(plussearch_radius) than the givenmask_frame_radius. This is useful to avoid that other signals or speckles “in the distance” affect the result of the fit. Modes “P”, “AS”, and “ASS” ignore this parameter.Caution
For measuring the stellar flux, this parameter should be set to a larger value than for planets; otherwise, the stellar flux will be under-estimated.
- Returns:
A tuple (final_position, flux), where the final_position is a 2-tuple of floats (i.e., the Cartesian position using the photutils coordinate convention).
- Return type:
- hsr4hci.photometry.get_fluxes_for_polar_positions(polar_positions, frame, mode='AS', aperture_radius=None, search_radius=None)[source]#
Auxiliary function for applying to
get_flux()to a list of positions that are given in (“astronomical”) polar coordinates.- Parameters:
polar_positions (List[Tuple[Quantity, Quantity]]) – A list of positions in polar coordinates, that is, every position is a tuple (separation, angle), where for the angle, 0 degrees is “up”, not “right”.
frame (ndarray) – The frame / image on which to perform the photometry.
mode (str) – The
modeparameter forget_flux(); see there for more details.aperture_radius (Optional[Quantity]) – The
aperture_radiusparameter forget_flux(); see there for more details.search_radius (Optional[Quantity]) – The
search_radiusparameter forget_flux(); see there for more details.
- Returns:
A list of the fluxes for each given polar position.
- Return type:
- hsr4hci.photometry.get_stellar_flux(psf_template, dit_stack, dit_psf_template, mode='FS', scaling_factor=1.0, aperture_radius=None, search_radius=Quantity(1, 'pixel'))[source]#
This function takes the unsaturated PSF template and computes the flux of the star, normalized relative to the integration time of the stack.
- Parameters:
psf_template (ndarray) – 2D numpy array with the unsaturated PSF template.
dit_stack (float) – Integration time of the frames in the stack (in seconds).
dit_psf_template (float) – Integration time of the unsaturated PSF template (in seconds).
scaling_factor (float) – A scaling factor to account for neutral density (ND) filters. Example: If the transmission is 2%, use a value of 0.02 for the
scaling_factor.mode (str) – See
get_aperture_flux()for more details. For the stellar flux, mode “FS” is recommended.aperture_radius (Optional[Quantity]) – See
get_aperture_flux()for details.search_radius (Optional[Quantity]) – See
get_aperture_flux()for details.
- Returns:
The stellar flux, normalized relative to the DIT of the stack.
- Return type: