different RA/Decs returned by pyEphem -


i using pyephem calculate ra/decs of satellites , i'm confused different values computed , described on

http://rhodesmill.org/pyephem/radec.html

this bit of code

sat=ephem.readtle("satname ", \               "1 38356u 12030a   14148.90924578  .00000000  00000-0  10000-3 0  5678",\               "2 38356   0.0481  47.9760 0002933 358.9451 332.7970  1.00270012  3866") gatech = ephem.observer() gatech.lon, gatech.lat = '-155.47322222', '19.82561111' gatech.elevation = 4194 gatech.date = '2014/01/02 07:05:52' sat.compute(gatech) print 'a_ra=',sat.a_ra,'a_dec=',sat.a_dec,'g_ra=',sat.g_ra,'g_dec=',sat.g_dec,'ra=',sat.ra,'dec=',sat.dec

gives

a_ra= 0:52:40.75 a_dec= -3:15:23.7 g_ra= 1:14:10.55 g_dec= 0:06:09.8 ra= 0:53:23.57 dec= -3:10:50.5

if change observers location gatech.lon, gatech.lat = '-5.47322222', '19.82561111'

i get

a_ra= 1:15:36.95 a_dec= -2:32:29.9 g_ra= 1:14:10.55 g_dec= 0:06:09.8 ra= 1:16:19.75 dec= -2:28:04.6

i thought observers position came calculation of sat.ra , sat.dec suprised see a_ra , a_dec had changed.

what missing?

thanks ad

per last paragraph of “body.compute(observer)” section of quick reference:

http://rhodesmill.org/pyephem/quick.html#body-compute-observer

for earth satellite objects, astrometric coordinates [meaning a_ra , a_dec] topocentric instead of geocentric, since there little point in figuring out satellite appear on j2000 (or whatever epoch using) star chart observer sitting @ center of earth.

and in issue has been opened behavior, project open suggestions text can appear more prominently prevent future confusion users:

https://github.com/brandon-rhodes/pyephem/issues/55


Comments

Post a Comment

Popular posts from this blog

inversion of control - Autofac named registration constructor injection -

does autofac support specifying registration name in components' constructors? example: ninject's namedattribute . you need use autofac.extras.attributed package on top achieve this so let's have 1 interface , 2 classes: public interface ihello { string sayhello(); } public class englishhello : ihello { public string sayhello() { return "hello"; } } public class frenchhello : ihello { public string sayhello() { return "bonjour"; } } then have consumer class, in want select instance injected: public class helloconsumer { private readonly ihello helloservice; public helloconsumer([withkey("en")] ihello helloservice) { if (helloservice == null) { throw new argumentnullexception("helloservice"); } this.helloservice = helloservice; } public string sayhello() { return this.helloservice.sayhello()...
Read more

ios - Change Storyboard View using Seague -

i have following code checks connection server, , depending on want change views if no connection found. nsstring *connect = [nsstring stringwithcontentsofurl:[nsurl urlwithstring:@"http://myserver.com"] encoding:nsutf8stringencoding error:nil]; if (connect == null) { [self performseguewithidentifier:@"network_failure" sender:self]; } else { // other code here } my problem not change views. have added storyboard segue between 2 views identifier of network_failure . not have navigation controller or that, problem? thanks help! no not problem. first of all, in objectivec exists nil object oriented null . must use that. so: if(connect == nil) or better: if(!connect) so due fact nil not same of null , probably code does't enter in if scope . you have been able discover breakpoint. anyway: be sure set trigger segue (line) 2 view controller , , name network_failure (that not best name. should instead view1toview2 ) as, m...
Read more

verilog - Systemverilog dynamic casting issues -

i've code snippet following in testbench function void write_to_port( my_data_type_base data ); my_data_type_extended data_ext; if(!$cast(data_ext, data)); `uvm_error(get_type_name(), "failed cast"); `uvm_info(get_name(), $psprintf("data_ext :\n%s", data_ext.sprint()), uvm_medium) // write data_ext out port.... endfunction when run it, i'm getting uvm_error "failed cast." i'm not quire sure why $cast not returning 1. can see, i'm printing out extended class data item after casting uvm_info. can see it's being cast properly. if don't use $cast if condition, don't runtime error. isn't coding practice use if dynamic cast check if $cast returning 1 ? what might reason behind cast not returning 1 in above case? i think semicolon on line 'if' not belong? i think consumes if statement, , uvm_error executes regardless of how if evaluates: if(!$cast(data_ext, data)); <- no semico...
Read more