I've been using it for a while and find that I like the way it interleaves itself into the rest of the Mac system. I've had a Mac since 1986 (still have the original out in my garage) and have used several image editors and believe the learning curve on Aperture does not require climbing boots and a sherpa to learn. Good luck!
IPhoto-good fro limited adjustments, plays well with Aperture, not so well with Adobe when more complex editing is desired. It is where I start and use it for photo triage.
PhotoShop- take vows, join a monastery and lifetime study to find out the seven or eight things you will use for photo editing. Scott Kelby has made a career bringing it to us mortals.
LightRoom-great for photographers, but doesn't play well with others, mainly moving pictures from iPhoto to LightRoom.
Aperture-Very similar to LightRoom and works seamlessly with iPhoto. Right now my personal preference. Very easy to post pictures to Mail and Facebook.
What you are describing is compositing, I think. Try Adobe Photoshop and use layers and mask out the portions of the picture you don't want to use. Then flatten the layers and you will get a composite of the visible portions of the different photographs. However, you can make a career out of learning Photoshop, so go to Adobe Downloads and down load a demo copy and then go to Scott Kelby's website explaining"Seven Point Program for using photoshop for photographers. Then prepare for a lot of work. The demo copy is actually a working copy which will allow you to test it for a month. Adobe Lightroom is also very good but I haven't done any compositing in it, just adjustments.
Good Luck
Spectacular shot. The rock in the foreground looks really interesting as well as Shasta in the background.
I have a canon 18-200 and not all of the converters work on the mount of that lens. I would check them out because the one I have works with the standard canon lens but not the EFs.
Joy,
Here are a number of things I do when I shoot through my telescope, but should work for you.
First and foremost use a tripod for all shots that have less than 1/60 of a second exposure times with a 24mm or higher lens.
1. put your camera in manual mode (M).
2. use a remote shutter control, or a timed exposure drive control, such as 10 seconds or 3 seconds if you don't have a remote. That is under the drive control section of the set up menu on my camera.
3. Under the M choose the number of seconds you want the shutter to remain open, ie, 1/2, 1, 15, for the shutter speed, or bulb for longer periods and you will need a remote shutter control for this. (This what is used in astro-photography and if you have mirror lockup it will reduce camera vibration, but you need to click the shutter twice when in mirror lock-up mode.)
4. Set your lens to manual focusing and turn off the image stabilization if using a tripod.
5. set your ISO to between 100 up to 400 determined by the amount of light available in your scene. Higher than this may produce unacceptable noise. I still use a canon 40D and the next stop up starts getting somewhat noisy in the dark areas.
6. Set the aperture (f4 to f9 depending on how much fore and background you want) so that it will allow you to get the light meter into an exposure compensation area that will read on the Ev chart on the bottom of your window, then adjust aperture for a centered reading. (or as close s possible.)
7. Take your picture and see how it comes out, and then adjust the shutter speed and aperture to increase or decrease the exposure for your picture. I use ISO 100 to 200 to keep noise low and you can also turn on long exposure noise compensation to help with this if it becomes a problem, but will increase your time per picture.
Good luck
Adorama TV has an excellent tutorial on night photography and they explain it very well.