howto:astrometry
no way to compare when less than two revisions
Differences
This shows you the differences between two versions of the page.
Previous revisionNext revision | |||
— | howto:astrometry [2009/11/29 09:17] – wildi | ||
---|---|---|---|
Line 1: | Line 1: | ||
+ | ====== Image astrometry parameters ====== | ||
+ | |||
+ | RTS2 is able to support on-line astrometry, with corrections being fed back to the telescope as correction parameters, thus significantly improving the telescope pointing. Following is list of parameters which affect astrometry, and a guide how to set them up. | ||
+ | For rts2-camd-dummy and rts2-camd-fli specify all parameters in file /// | ||
+ | |||
+ | * **XPLATE** and **YPLATE** - size of pixel in arcseconds in X and Y direction. This is specified by //--plate < | ||
+ | |||
+ | * **FLIP** - that depends on readout direction and used optics. Can be also regarded as indication of negative **XPLATE** - e.g. arcseconds rose in different direction along X axis then is common. It is 1 for most cameras, the only exception so far is Andor, which have 0 flip for EM channel and 1 for non-EM channel. This is set in the driver and unless you put extra mirror in optics, should be correct. If needed, you can set flip with //--flip// parameter passed to camera daemon. Again, **FLIP** is visible in **rts2-mon**, | ||
+ | |||
+ | * **ROTANG**, which is an angle of north direction from vector Y axis. It is 0 when north is up on images, 90 when north is towards left (and **FLIP** is 1). **ROTANG** changes on german equatorial mount (GEM) by 180 degrees if you cross pole and go to the opposite side of the sky - eg. from hour angle 2 to hour angle 14. Default mount **ROTANG** is specified by //-r// parameter, and shows as **MNT_ROTA** in **rts2-mon**. You can also edit it there. **MNT_ROTA** changes on GEM by 180 degrees automatically. Please be aware, that **ROTANG** written to the FITS file can be sum of different variables, all having **RTS2_DT_ROTANG** flag set when the variable is created. RTS2 sums all variables with **RTS2_DT_ROTANG** flag set to form resulting **ROTANG**, which is then written to FITS headers. Check your mount source code for details - e.g. for OpenTPL mount with derotator, derotator angle is added by this code: | ||
+ | <code c++> | ||
+ | // nasmith derotator | ||
+ | if (opentplConn-> | ||
+ | { | ||
+ | createValue (derotatorOffset, | ||
+ | createValue (derotatorCurrpos, | ||
+ | createValue (derotatorPower, | ||
+ | } | ||
+ | </ | ||
+ | |||
howto/astrometry.txt · Last modified: 2009/11/29 00:00 (external edit)