BD700 First Officer describes a visual departure from Runway 15 at ASE with a right turn out that does not remain visual until above the terrain. The departure was a ferry flight and occurred after being on duty for over 16 hours.

Narrative

Fatigue/Bad decisions: We left South America for Aspen with a Customs/fuel stop in Texas; on arrival at Aspen our block time was 13:00 hours and our duty time was 16:00 hours. Aspen's weather was a concern as TAF showed possibilities of low ceilings and visibility and snow. We were due back in Texas for maintenance the same day. On arrival ATIS W was 170/25G36 10 miles 80 broken 6/-4 29.74. ATIS W remained for our departure; winds were stable from the south; not shifting as usual for Aspen which made a northwest departure not possible. I proceeded to agree to the signed waiver to be able to depart to the southeast as reported ceiling was 8;000 broken and we could see the tops of the mountains around Aspen. I decided to take off Runway 15 and climb visually straight ahead and turn to LINDZ as per clearance. This was second or third wrong decision as I should have made a climbing left turn to LINDZ due to lower terrain to the east. At about 300 FT above the mountains we entered a solid cloud layer; around 12;000 and came out on top at around 14;500. Being the MSA in the quadrant 15;700 and seeing yellow in the EGPWS about 4 miles ahead I became concerned those few seconds as to terrain clearance and unable to maintain VFR until established on the IFR departure track. In hindsight I should have delayed departure until wind shifted or better still delayed maintenance for a day or two.