ECHMASK reads the SDIST.DAT file produced by SDIST. The straightforward behaviour is achieved by specifying PERISCOPE false and giving zeroes for all widths and offsets. This causes a width derived from SDIST to be used; if the fit was Gaussian the width is twice your estimate to SDIST, and if the fit was Edges it uses the third largest width actually calculated (to exclude atypical values). Otherwise specify a new value for OBJWIDTH; overestimate rather than underestimate to prevent jumps in the extracted data due to the slope of the orders. ECHMASK also needs to know the order numbers. MSTART is the order number for the first order you selected with ICUR, and should be that listed by:
$ EXAM CONT.FITS.UCLES.ORDER_CENthough there is always the possibility of a
1 error.
If you get it wrong, you can adjust the order number using ICADD
to add or subtract the error from the mask structure. You
have to add or subtract ten counts to adjust by one order, e.g. if the MASK
contains a data value of 420, this refers to order 42 and adding ten to it to
make it 430 causes it to refer to order 43.
This is a typical run of ECHMASK.
$ ECHMASK
(COFile) Name of file containing order fit coeffs [SDIST] -
(PERIscope) Is the star / sky periscope fitted? [NO] -
(OBJWidth) Number of rows of object to extract per order [0] -
(OBJOffset) Offset from order centre of object centre [0] -
*** Will use an OBJWIDTH of 6 pixels
(S1Width) Number of rows of region 1 sky to extract [0] - 10
(S1Offset) Offset from object centre of region 1 sky centre [0] - 9
(S2Width) Number of rows of region 2 sky to extract [0] -
(MStart) Number of the first order fitted [82] -
(MDelta) Order number increment (-1 or +1) [-1] -
(MASk) Name of mask image showing order positions [MASK] -