Hi there, this is a Polaroid Packfilm back for, well, packfilms, which were designed to contain peel-apart instant films within a filmpack.
Unfortunately, both Polaroid and Fujifilm have stopped producing packfilms, which made them EXTREMELY EXPENSIVE.
FYI, the average price for Fujifilm FP-100C (ISO 100 Color film) each pack is about 60~100 USD for now in 2020.
Since that's just an ISO 100 film I don't think that you'd be shooting with that...
Fujifilm made some FP-3000B(ceased production too long ago) which is ISO 3000 B&W film, might be matching your needs, which is costing about 60-100USD too in 2020.
All those films are expired but still can provide very optimal results, if you fully understands them. But honestly I don't think that these films suit astro-photography anymore. However, if you want to, there're still some other options like using the integral film backs instead of the peel apart film backs.
FYI, there were many costumed integral film backs made from those Fujifilm Instax cameras, which are using very cheap ISO 800 Instax integral films. And if you wish to take one step further, there are some real polaroid integral film backs (really rare though) which can still be used with today's Polaroid Color 600 or 70 films. The 600 type is about ISO 640, while the 70 type is about ISO 160.