Is it cheating or is it just a better/easier way to do it? The tools both hardware and software are there to be used and how you use them is up to you. Personally I think it was a clever way to solve what you thought was an issue with your image. People use multiple exposures all the time so if you've used it to create something that pleases you or someone else then why not?
The reality is that all images go through some form of post processing even the ones from the big boys at NASA. There's nothing wrong with a little cheating so long as you're honest about it when interrogated by the 'www' masses.
It's really only when someone tries to claim that they've taken a 'one shot Hubble quality image of M42 using a magnifying glass and a 1MP camera from a smartphone handheld' that people begin to lose trust and respect for them.
Having said all this I do think that it's always good to learn or at least try to learn how to do things with the least amount of manipulation possible first. I often find that the people who 'cheat' best usually already know how to do things without having to 'cheat', which probably explains why they are so good at it.
Nice image BTW.
