Dust-to-Gas Mass Ratio of the Carbon-Rich Nebula BD +30 3639

This paper computes a self-contained budget for BD +30 3639 from published observational values, with every derived number produced by the deposited computation script. BD +30 3639 is a young planetary nebula with a carbon-rich central star of Wolf-Rayet type and a prominent infrared dust shell. Its dust mass has been estimated from the infrared spectral energy distribution, while the ionised gas mass follows from the compact radio and optical nebula. The ratio of those two masses is a direct measure of how efficiently refractory material condensed in the outflow, and it can be compared with the interstellar dust-to-gas ratio of roughly one part in a hundred to judge whether the nebula is dust-rich or dust-poor for its composition. The headline results are: dust_mass_Msun = 0.004; gas_mass_Msun = 0.0327; dust_to_gas_ratio = 0.122; ratio_to_ISM_0p01 = 12.2; total_dust_plus_gas_Msun = 0.0367; dust_temperature_K = 120. The dust-to-gas ratio exceeds the interstellar reference value, consistent with fresh dust production in a carbon-rich outflow where carbon is abundant after dredge-up. The total ejected mass in dust plus ionised gas is still only part of the envelope budget, because neutral gas outside the ionised zone is not counted by either estimate. The ratio should therefore be read as a property of the inner, processed part of the shell rather than of the entire circumstellar envelope. The calculation is presented with its inputs, relations and sensitivities stated openly, so that any revised distance, density or stellar parameter can be substituted and the verdict recomputed directly.