Today one of my players was working with the Intellego Guidelines and come with a question I'm unsure how to answer
When you use the Senses and not the Ranges?
Like, for the most simple things: Intellego Vim spells that "Discerns the Art of Vis" and the one that "Detect the presence of Vis" are Range or Sense?
This question was born because of the Hermetic Astrology mystery, where it says (TM:R Pg 51):
"Discern and measure a single astrological factor in the environment. Discern and measure the astrological time in the environment. (The caster is learning the conditions at the target location, not at his own locale, so usually extend range.)"
The example spell that use this guideline then use Range. But it can be with Sense? I always assume that "Discern" was Sense based [mostly because the Intellego Imaginem guideline]
So now I'm looking on what is the general rule here, so my players and I can work better on the lab.
In my experience, when in doubt, it does not matter. I have worked out a couple of examples in the past, just to find exactly the same level with either mechanic. Even so, let's see if there is more to it...
Firstly, your question is inaccurate. There is always a range. For most canon sense spells, the range is personal, meaning that the sense is granted to the caster. It could very well be touch or something else, to grant this sense to somebody else.
This means that the beneficiary has their sense (which is the target) enhanced to perceive some special property. I suppose a magical sense spell for the purpose you quote could let the beneficiary smell a certain astrological property in locales that they travel through.
Non-sense intellego spells gives the caster information about the target. In your example you could well extend the range to AC to get information about a remote locale well out of range for any of your senses.
Sense spells are most useful when you want to scan an area for some feature or property. Non-sense intellego spells would have to be recast for each target. OTOH sense spells do not immediately work across an AC, and they are no use if you cannot map the information into sensable features.