It looks like your Orion may be out of spec. TT published specs on Orion's temperature stability is +/- 10 ppm, At 10 MHz, that is 30 Hz. Your Orion had an excursion of 989.0 - 953.7 or 35.3 Hz. One would hope that the +/- 10 ppm is 'worst case' but your measurements are even worse. 73, Mark