Minderwiz
Go to Lot of Fortune and make sure the second option is selected, that is giving a different calculation depending on whether it’s a diurnal (day) or nocturnal (night) chart.
May I ask what is the second option called?
I see Diurnal
The other check box is "Use whole-signs not degrees"
The option that is checked right now is diurnal.
Which program are you referring to. In the context of the thread, my initial guess was that you were referring to Starfisher. But on a re-read, I'm not sure that is so.
To speed things up, I'll respond in context and assume it's Starfisher, but if it is something else, such as Morinus, I'll respond when you tell me.
In Starfisher, you need to select Tools and then Settings. What you are after is the default bodies tab. That's where you can select planets and important points. You will see two entries for Part(sic) of Fortune.
One is simply called:
Part of Fortune and the other is called
Part of Fortune (diurnal)
The first changes the calculation depending on whether it is a day (diurnal) chart or a night (nocturnal) chart. The second only uses the day (diurnal) calculation, irrespective of whether it is a day or night chart.
The reason why there are two alternatives is that Ptolemy decided that it was simpler to just use the diurnal calculation, even though all his contempories, such as Vettius Valens used the calculation relevant to Sect (diurnal or nocturnal) and their practice, rather than Ptolemy's was passed on to Persian and Arab Astrologers.
In the later Medieval period there was a belief that the Parts were of Arabic origin (hence Arabic Parts) and this had two effects. Firstly they believed that the Arabs had perverted Astrology from its true form. As Ptolemy was their only real original source of Hellenistic Astrology, they started using his calculation. They also dropped most of the Parts because they were 'not original', as Ptolemy didn't use them.
Secondly, both Ptolemy's calculation (which was used by Lilly in Horary) and the name Arabic Parts were transmitted to Modern Astrology. So you will find many Modern Astrologers, using that calculation rather than the day/night version.
Only in the last twenty or so years have we discovered that the Lots were of Hellenistic origin and that Ptolemy was atypical of Hellenistic Astrologers. I use the day/night version (simply Part of Fortune in Starfisher) but if you don't want the calculation to change with the Sect of the chart, then use Part of Fortune (diurnal).
Virtually all software which calculates the Lot of Fortune offers both alternative ways of calculating it.