>>“Of course, now I have to decide to go to Yellowstone or not.”
Yes, go to Yellowstone! That park in the winter is a once in a lifetime experience for most people. No matter if you get 100 great shots or none at all experiencing Yellowstone in the winter is woth the trip.
>>“The other approach is to go to Yellowstone as planned and enjoy the view, take photos with this and my other lenses, and not worry so much about taking perfect photos.”
Sharpness – In my opinion uber-sharpness is way over rated. The ability to zoom into ridiculously high magnifications and the constant pressure exerted by our “peers” over the internet have caused us to become obsessed with sharpness to the point that loose site of what makes a great photograph.
Reading the internet, we are lead to believe that sharpness (or sometimes low noise) is the most important aspect of image quality. I respectfully disagree!
A great photograph is about combining your subject, the light and your composition to create a compelling image. If the image is not compelling or interesting or if it has no message to convey to the viewer, then it won’t matter how sharp it is – it only becomes a very sharp snapshot. On the other hand if you have an image that is a tad soft but it draws in and holds the attention of the viewer – that has the potential to be a great photograph.
Now, I strive to get the most out of my gear and I hope to get the sharpest image that I can, but I don’t worry all that much when an image is a little soft at 100% zoom. I have come to know, through experience, how sharp an image needs to be for my intended output.
Unless you print really big and then examine the print with your nose against the glass a lot of the detail and “perfect sharpness” we look for at 100% will not show in the print.
I don’t make my images for other photographers, who are the only people who closely examine photos looking for perfect sharpness and grain. I do not want the viewer’s putting their nose against the glass to examine minute details. My photographs are intended to be viewed as a whole – I want the viewer to absorb the entire composition. When we stand back and view the entire image, no matter how big it is printed, those tiny flaws that we obsess about at 100% on our computer screen just blend in and disappear.
Remember that on your computer screen at 100% zoom you are looking at a huge version of your image. My laptop screen is about 100ppi so when I view D300 image at 100% it is like looking very close at a 43 inch wide image printed at a very low resolution.
Also, I noticed that your first image, the bolt, is an unprocessed NEF shot using the Standard Picture Control. The sharpness setting is 3 in the Standard Picture Control. This is a fairly low value, it is a great start for post processing, but it is not a good judge of the sharpness that you can achieve with some basic post processing. (And No - I don’t recommend increasing the in-camera sharpness setting, sharpness is better controlled in post processing)
Try this; Take the best shot that you got of that bolt. Then post process the image, resize for printing and sharpen. Now make an 8” x 10” or even a 12” x 18.” Once you have the print/s view them in good bright light at a distance that your eye can take the entire photograph and judge your sharpness from those prints.
Having said all of that – My advice...
Continue to work toward making images as sharp as you can - but try not to get caught up in the pursuit of (sharpness) perfection. Concentrate on capturing compelling well composed images. Your ability to consistently get very sharp shots will improve with time and experience.
When you judge sharpness – consider what you can do in post processing to increase sharpness – decide how you will eventually output (a print, on screen) the image and who the intended viewer is. Remember that you and other photographers are the only people who will be scrutinizing every little detail of the photo.
Don’t let the internet driven hype over sharpness (or making perfect images) detract from your enjoyment of the craft.
On any given day of shooting wildlife my goal is to get 1 “keeper” – anything more is a bonus. On a trip like you are planning to Yellowstone I would be more than happy to get 10 -15 above average shots and hopefully 2 or 3 truly great shots.
So, go to Yellowstone – have fun – get some shots – have more fun!
PS I agree with Neil about the 5 series tripod for the 600mm lens. The bigger tripod is not a magic bullet and it will not instantly solve all of your problems but it will help you to get more consistent results.