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cosmoskid
professor emeritus
Reged: 11/15/08
Posts: 685
Loc: Indiana USA
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If for example I'm viewing an object at RA 12H 30' Dec. 25 degrees 45' for 10 minutes, will I need to reset the RA back to 12h 30' before finding the next object?
One more question. How long of a time frame are the RA and Dec. calculations good for if I'm using the RA and Dec values in the sky atlas to find objects?
Thanks for the help.
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"Educate and inform the whole mass of the people... They are the only sure reliance for the preservation of our liberty." Thomas Jefferson.
"Who are they to judge the life I live? Before you start pointing fingers, make sure your hands are clean.”
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4585
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Yes, I believe the ETX setting circles are not _driven_...haven't paid much attention to them, ever. So you'll have to reset to your current RA before moving on.
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Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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jgraham
Postmaster
Reged: 12/02/04
Posts: 6763
Loc: Dayton, Ohio
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The R.A. and dec values given for a particular object are good for a lifetime unless you're doing high precision work, even this it's common practice to calibrate on a bright star near the target for precision pointing. And yes, when using setting circles it's a good idea to reset the R.A. circle to the correct value before moving on to the next target.
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-John
================================================
Homebuilt scopes from 4.25-16.5"
Meade LXD75-N6/SN6/SC8, DSX-90, ETX-60BB, ETX-125PE, DS-2130
Orion StarBlast, BinoViewers, Coronado PST
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cosmoskid
professor emeritus
Reged: 11/15/08
Posts: 685
Loc: Indiana USA
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Thanks. What I was trying to figure out is are the RA and Dec figures for an object good for any time of the night wether it be 11pm or 2am?
--------------------
"Educate and inform the whole mass of the people... They are the only sure reliance for the preservation of our liberty." Thomas Jefferson.
"Who are they to judge the life I live? Before you start pointing fingers, make sure your hands are clean.”
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brianb11213
Carpal Tunnel
Reged: 02/25/09
Posts: 2113
Loc: 55.215N 6.554W
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Quote:
What I was trying to figure out is are the RA and Dec figures for an object good for any time of the night wether it be 11pm or 2am?
Yes but you actually need to set the current sidereal time as well as the RA, on different indices, one moves the other doesn't. This action converts RA into hour angle (the time before/after meridian crossing). Of course you need to know the local sidereal time; civil time + tables via mental arithmetic, or a planetarium program, or a ST clock.
Edited by brianb11213 (06/27/09 04:07 AM)
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