The Shraddha should never be performed under any of those constellations that are considered as dreadful (such as Ashlesha, etc.,) and any of those that upon calculation, seem to be hostile. Indeed, in this matter, all these constellations should be avoided which are forbidden in astrology.
दारुणेषु च सर्वेषु प्रत्यरिं च विवर्जयेत्। ज्योतिषे यानि चोक्तानि तानि सर्वाणि वर्जयेत्।।१२७