| Date | Person | Description |
|---|---|---|
| Fournier, Georges | Fournier collaborated with Boulliau on astronomical observations in Paris | |
| 1618 – 1630 | Malapert, Charles | From 1618 – 1627 or 1618 – 1630, Sylvius assisted Malapert in conducting astronomical observations in Douai |
| 1633 | Perovius, Szymon | In 1618, Perovius conducted astronomical observations in Kalisz; the results were published by Malapert in his “ Austriaca sidera ” ( Douai, 1633) |