newfits: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/newfits - from package: wcstools

You may install the required package with command apt-get install {package}

Error in other languages:
newfits: bevel nie gevind nie
newfits: comandă negăsită
newfits: comando não encontrado
newfits: commande introuvable
newfits: command not found
newfits: käsku ei ole
newfits: không tìm thấy lệnh
newfits: komanda nerasta
newfits: Kommando nicht gefunden.
newfits: kommandot finns inte
newfits: komut yok
newfits: nie znaleziono polecenia
newfits: níor aimsíodh an t-ordú
newfits: no se encontró la orden
newfits: no s'ha trobat l'ordre
newfits: opdracht niet gevonden
newfits: parancs nem található
newfits: perintah tidak ditemukan
newfits: príkaz nenájdený
newfits: příkaz nenalezen
newfits: команда не найдена
newfits: командата не е открита
newfits: 命令找不到
newfits: コマンドが見つかりません