gothic5 wrote:I was able to get 28 45 Cancer as ascendant with LST 30 53 30 using a calculator and interpolating with table of houses.I tried also with formula Asc= arccot( (cos( RAMC+90) - tan(e) * tan( f ) ) * cos(e) / sin( RAMC+90) ) but left out the Lattitude.Is it possible to calculate by using Asc= arccot( (cos( RAMC+90) - tan(e) ) * cos(e) / sin( RAMC+90) )?

No

The original formula is:

Asc = arccot( ( cos( RAMC + 90 ) - tan(e) * tan( f ) ) * cos( e ) / sin( RAMC + 90 ) )


If the latitude ( = f ) is 0.0... and only then, then you can use the formula :

Asc = arccot( ( cos( RAMC + 90 ) ) * cos( e ) / sin( RAMC + 90 ) )

If you multiplied something with a value 0.0 . the result will be always 0!
So that part of the formula you can omit.

Greetings from the Netherlands,

gothic5 wrote:Just another question about above subject.I recently read David McCanns article about getting Regiomantus cusps from Placidus tables.He says to subtract 6 hours from Local Sidereal Time of chart.Ascendant at equator for this LST is MC of chart.I tried applying formula Asc= arccot( (cos( RAMC+90) - tan(e) * tan( f ) ) * cos(e) / sin( RAMC+90) ) Is this possible at equator with lattitude 0?

Yes. It is possible.

Thanks again for the reply.My interest in calculating points on the chart (asc mc house cusps for different systems) came from trying to understand how the concepts applied to the Great Circles.I spend a lot of time on my astronomy program which provides a good insight although the view seems to be one on the Earth toward the outer region.In reading astrological books or texts that explain chart calculation the diagrams show a view toward Earth from outside.Either way it is not always clear to me how projection of a particular circle(ecliptic,equator or other) onto another results in the point of a cusp.But I noodle around with different ideas-like putting planets at the cusp points and seeing how they change with different house systems while observing their astronomical points.Ascendant Calculation (and MC) usually are pretty clear (ecliptic & horizon) but I know some systems like Morinus can use another point for the first house cusp.Best wishes from cyberspace HS

Can anyone recommend a book on spherical trigonometry? I bought one (Schaum outline series) where it gives a lot of formulas for calculating triangles applied to circles but it dosen't really give specific values.Plugging in values to ABC abc makes the text clear to me.Also curious if anyone has read Glen Van Brummelen/Heavenly Mathematics: The Forgotten Art of Spherical Trigonometry which talks about celestial calculations of ancient Egypt and Greece.Request any info-Thank You Harold