celestia-gnome: 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/celestia-gnome - from package: celestia-gnome

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

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