1. Connection Options: As you make selections for the various devices, you will usually see a prompt asking if the device is already connected and ready to communicate with PHD2. If you say 'yes', PHD2 will try to connect and then fill in some of the data fields with information read from the device. Saying 'no' simply means you'll have to enter the data by hand. If PHD2 tries to connect with the device and fails, you'll still be able to proceed by just entering the data manually. Device-connection in the wizard is basically a convenience feature that makes it easier to fill in the fields with accurate values. You won't see the prompt if PHD2 already knows the device can't return useful information - for example, if the mount choice is 'on-camera.'
2. Camera connection pane: unbinned pixel size. If you said 'yes' to the connection prompt, this information will usually be filled in automatically and the control will be disabled. If you said 'no' or if the device doesn't report its pixel-size, you'll need to enter the value by hand. You should be able to get the unbinned pixel size from the camera spec sheet or the manufacturer's web site. If the pixels aren't square, just specify the larger dimension or the average value if you prefer. This won't have any effect on your actual guidng results, but it will allow PHD2 to know the image-scale for your set-up. This is used for setting baseline guiding parameters, doing sanity-checks on calibrations, reporting guiding performance, and getting support on our forum..
3. Camera connection pane: binning level. If your guide camera supports binning (many do not), you can specify what level of binning you want to use for this equipment profile. If you want to use the same equipment set-up with different binning levels, it's best to create separate profiles for each binning value. If your guide camera has very small pixels and you have also specified a long focal length, you may see a 'warning' icon next to the Pixel Scale field. That is telling you that the specified image scale is probably too small and you should bin the camera if possible.
4. Camera connection pane: guide scope focal length. This seems to be a common place for mistakes, so it's worth being careful and getting it right. The correct value is not the aperture of the guide scope, it is the focal length. So, for example, if you're guiding with a 50mm finder scope, the focal length willl not be 50mm - it will probably be something closer to 150-175mm. A 60-80mm refractor guide scope will probably have a focal length in the range of 240-500mm, not 60-80mm. Similarly, if you're guidng with an OAG on your main imaging scope, the focal length will be that of the main scope. In some cases, you may be using a small threaded focal reducer on the guide camera, so that must also be taken into account. Like the pixel-size entry, the focal length doesn't demand a great deal of precision, but you should get as close as you can. Otherwise, the performance numbers may not reflect your actual results and the baseline guiding parameters may be sub-optimal.
5. Mount connection pane: mount guide speed. This is another area that seems to cause confusion. The guide speed is a parameter set in the mount or in themount driver, it's not something controlled by PHD2. PHD2 never sets the mount guide speed, it only reads it. It is usually expressed as a multiple of the sidereal rate and is typically in the range of 0.5x - 1x sidereal. Despite what you may read elsewhere, it's usually best to use guide speeds in this range rather than much lower speeds. Higher guide speeds can help to clear backlash more quickly and may help to overcome stiction problems. If you say 'yes' to the connection option prompt, PHD2 will attempt to read the current guide speed from the mount. If this fails for some reason, you'll need to enter the guide speed manually. PHD2 uses this value to automatically set the calibration step-size and to aid in checking calibration results; but the guide speed information is not important for the actual guiding. If you're using different guide speeds on the RA and Dec axes, enter the larger value. If you really can't determine what the guide speed settings are in the mount, leave the setting at the default value of 0.5X. This pane also has a checkbox regarding the presence of high-precision encoders in the mount. These devices are somewhat rare but are sometimes included on expensive, high-precision mounts, and you are likely to know if you have them. Most users will leave this box unchecked.

Why Nebulosity?

People looking at software for astrophotography have a wide range of options, these days. So, you might ask, why Nebulosity? Nebulosity takes a different approach than many packages. You’ve got a number out there that are trying to be the be-all and end-all package that controls everything from your camera to your dome to your toaster. As a result, they’re often very large (and therefore tougher to navigate), and very expensive. In general, this doesn’t make for something well-suited to someone just getting going in this hobby. In addition though, much of what you get in larger packages isn’t used by some of those doing the best work out there. You’ll find top imagers that use their astro package to control the camera, get the images, pre-process and stack them, and they’ll then shift entirely (or nearly so) over to something like Photoshop or PixInsight. With Nebulosity, you can do all that for a fraction of the cost and with a far simpler user interface. This simpler interface has led many advanced users to abandon other packages and use Nebulosity in the field and for at least their initial processing. Why? Try it and find out! The demo is free and lets you try out all the features.

More info

For a full run-down, have a look at the feature list in the full manual or simply download it and try it out (Download page). All features are enabled when you download it as a demo, but saved images will be degraded (diagonal lines superimposed) until you purchase a license. Thus, you can evaluate the software extensively prior to purchase. Keep in mind, all changes are described in the Release Notes and often Pre-release versions are available with new features.