I travel internationally by air every two weeks or so with my job, and often take birding equipment along. So here's my advice:
- I never, ever, ever put anything valuable into hold luggage. Hold luggage is going missing more than ever at the moment (especially BA), and not all of it ever turns up. How much of your big birding trip do you want to do without your scope?
- Also, on many occasions I've watched bags literally being thrown in and out of the hold. I'd never put valuable optical equipment in there and trust it to baggage handlers, who have no respect for your property
- The recent UK legislation on number of carry-on items is being relaxed in many UK airports (check before you fly), so you can take two items on now, on some planes.
- I will usually put my bins, digitial camera and camcorder into my hand luggage, and carry my 'scope loose as the second piece of carry-on, where permitted. Otherwise it goes into the hand luggage. Tripod is packed in towels/fleece into the hold luggage - so far it's always survived in one piece, although my Dad's was broken in hold luggage two years back. No option, though, with current legislation.
Hope this helps! Luckily I don't have to try and worry about a DSLR, though...
BT
PS - If flying through UK airports, make sure your hand luggage meets the current strict requirements, or else it will be refused and end up in the hold...