Calibrating raw photometric measurements So I have a photometry data sourced from Solar Mass Ejection Imager's (SMEI) server as an ‘add-on data’ for my point source of interest (a variable star) with a 104 minute cadence. However, it’s not really in the UBV photometry system, in V-band specifically, but rather scales with their SMEI photometry system while processed through a centroid fitting.
Is there a possible way to initially calibrate the photometry data like mapping the point source's nearby bright stars perhaps? And if so, how should I start of?
Attached photo is the 'raw' light curve of the star from the gathered SMEI data.

Please bear with me for I'm just a novice especially with regards to photometry. Guide(s) and response(s) are always welcome and I look forward to.
Clear skies.
If I understand the question correctly, you have raw data from a CCD sensor in arbitray units (which correlate with brightness) and your challenge is to callibrate this intensity for a certain frequency range.
Not knowing much about the SMEI sensor and where on the sky it has been looking at, I struggle to give you a full recipe. If you have for an object whose intensity (time series) from other observational instrument in the desired frequency band, you could use that non-SMEI data to correlate (if not even fit e.g. linearly) with the raw data time series for the same object as recorded by the SMEI sensor. This gives a calibration function which delivers intensity from raw data in arbitraty units.
References which sound possibly helpful

P. Hick, A. Buffington, B. V. Jackson: The SMEI real-time data pipeline: from raw CCD frames to photometrically accurate full-sky maps (2005)
A. Buffington et al.: Photometric Calibration for the Solar Mass Ejection Imager (SMEI)
Martin Clayton and Anthony Holloway: Simple Spectroscopy Reductions