Soluna Holdings (NASDAQ:SLNH) shares tanked 17.2% in Friday after-hours trading following its announcement to sell shares of its common stock in an underwritten public offering.The company, which develops sustainable data centers for cryptocurrency mining and other intensive computing, did not specify the size or terms of the offering, which increases its share supply and thus dilutes investors' ownership.The underwriter will be granted a 45-day option to buy up to 15% more of the number of shares of common stock sold in the offering at the public offering price, which was not disclosed.Proceeds from the offering will be used to enhance its data centers as well as general corporate purposes like working capital and capital expenditures.In August, Soluna received $12.5M funding from Spring Lane Capital.