Just moments ago (with the assistance of Cascable support) I was happy to sort out the biggest reason for not whole heartedly recommending the Cascable application. In using the shutter robot intervalometer settings I thought the interval setting meant delay when it meant the total shooting time. Now that I tested this out after changing this to the shot time plus delay I can see that this application works great!
I know that the popular choice for assisting photos is Backyard Nikon or Backyard Eos. My 1st reservation to this was that it would make a need for wiring a laptop or windows tab
let into the camera. I didn't want to add another big purchase if a basic intervalometer would work half way decent for setting up shots. I also really didn't require a windows laptop or tablet for anything else.
In my experience (as limited as it is) I now would highly recommend Cascable for it's element of portability, versatility and giving users an alternative to windows.
Here is the big limitation, if your camera doesn't have a WiFi hotspot you wouldn't be able to use it. There should be a listing of cameras that this would work for. In my case the Nikon D5500 does have a WiFi hotspot. You would enable WiFi on the camera, then you would pick up the WiFi connection on the iPad or iPhone settings. So far I have been pleased in how well the connection has held. It has only disconnected when the camera has been out of proximity with my iPad.
Once connected to the camera's network you enter the Cascable application and enable the camera.
Once the camera is connected likely this will pop into live view mode with the camera. At this point you can select and change many of the camera's settings.
From this point I like to just use the intervalometer instead of the camera recipes, but if needed you can use "recipes" for complex shooting settings with patterns of delays, f stops, bulb mode, etc... When using the intervalometer settings just choose how many shots you need to shoot, what the total shooting time is (interval) and what the stop criteria is (which for me is also the number of shots).
If this is not enabled you can just take a single shot with the given settings, once this is enabled it will perform the shots to the settings you've selected. In the last shot there will be a short review of one of your long exposure shots.
You can transfer images over from the camera to iPad or iPhone but that likely would be quite lengthy in time.
There are several things that I like about this application in terms of Astrophotography.
1st of all by having the live view on the iPad it helps you to know if you were in the right neighborhood of stars. I disable the histogram view in order to have more viewing screen.
Once the location is set up you can zoom in on a specific window you can place around a star which I use for setting up focus.
I also like how the last frame shot reviews on the screen briefly as then you can see whether your shot settings achieved what you were looking for.
I know I don't have the shooting experience to be lending any advice but for me a starter I find that the Cascable application helps considerably.
I'm sure I'll run into more quandaries as I have more shooting time but I would certainly +1 this application recommended by Geneva_min.