<p>For an object at about RA 6h and close to the celestial equator, viewed from 37 degrees N, it becomes visible in the early morning on about July 20th, and it is is visible at some point during the night until about May 20th, when it sets shortly after the sun.  Between May 20th and July 20th it is not visible. (Determined Stellarium)</p>
<p>An example of such an object is Betelgeuse.</p>
<p>An object that is at 6h of right ascension will culminate at midnight (ie reach its highest point at midnight about on the winter solstice on Dec 21st. The sun has a right ascension of 6 hrs on the summer solstice on June 21st and a RA of 18 hours on the winter solstice.  So the best time to observe the object would be on the winter solstice.</p>

CC BY-SA 4.0
2020-08-30T14:58:03.183Z
2020-08-30T14:58:03.183Z
James K
<p>I am trying to answer the following question which I slightly understand but need a clearer explanation:</p>
<p>What are the times of year to observe an object at X hours of RA at visual wavelength?</p>
<p>I am trying to use the march equinox as a starting point for 0 RA and for a 12 hour RA object, it will begin to rise from the east as the sun sets west of course, around 6 months from the march equinox???</p>
<p>I appreciate an explanation and if you can link a map or a helpful visual as well. Thanks!</p>

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2020-08-30T14:00:07.853Z
It depends on the declension and your latitude:  For example Polaris is visible all year for Northern hemisphere observers (and never visible for southern)  Other stars are visible for different amounts of time:  Sirius is visible between mid August and Mid April where I am, (It is different at other latitudes).
James K
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2020-08-30T14:30:58.020Z
Say for example on 37 N latitude and an object at RA 6 hours.
echo12
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2020-08-30T14:42:59.020Z
and its declension?
James K
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2020-08-30T14:47:16.360Z
Observer somewhere in California 37N 119 W. And object 6 hrs RA
echo12
CC BY-SA 4.0
2020-08-30T14:51:41.910Z
Then the answer is anything from always visible (near the celestial north pole) to never visible (near the celstial south pole)  you have to pick a declension or there *is no answer*
James K
CC BY-SA 4.0
2020-08-30T16:50:32.440Z
I think James meant *declination*.
Mike G
<observational-astronomy><positional-astronomy><night-sky>
Right ascension, Equinox, Positions Help
echo12
# Right ascension, Equinox, Positions Help

(Asked by: username_0 on 2020-08-30)

I am trying to answer the following question which I slightly understand but need a clearer explanation:

What are the times of year to observe an object at X hours of RA at visual wavelength?

I am trying to use the march equinox as a starting point for 0 RA and for a 12 hour RA object, it will begin to rise from the east as the sun sets west of course, around 6 months from the march equinox???

I appreciate an explanation and if you can link a map or a helpful visual as well. Thanks!

**Tags:** observational-astronomy, positional-astronomy, night-sky

> **Comments:**
> **username_1**: It depends on the declension and your latitude:  For example Polaris is visible all year for Northern hemisphere observers (and never visible for southern)  Other stars are visible for different amounts of time:  Sirius is visible between mid August and Mid April where I am, (It is different at other latitudes).  
> **username_0**: Say for example on 37 N latitude and an object at RA 6 hours.  
> **username_1**: and its declension?  
> **username_0**: Observer somewhere in California 37N 119 W. And object 6 hrs RA  
> **username_1**: Then the answer is anything from always visible (near the celestial north pole) to never visible (near the celstial south pole)  you have to pick a declension or there *is no answer*  
> **username_2**: I think username_1 meant *declination*.  

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## 1 answers

### Answer by username_1 on 2020-08-30. Score: 0 | Accepted answer

For an object at about RA 6h and close to the celestial equator, viewed from 37 degrees N, it becomes visible in the early morning on about July 20th, and it is is visible at some point during the night until about May 20th, when it sets shortly after the sun. Between May 20th and July 20th it is not visible. (Determined Stellarium)

An example of such an object is Betelgeuse.

An object that is at 6h of right ascension will culminate at midnight (ie reach its highest point at midnight about on the winter solstice on Dec 21st. The sun has a right ascension of 6 hrs on the summer solstice on June 21st and a RA of 18 hours on the winter solstice. So the best time to observe the object would be on the winter solstice.


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