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f/15 is too slow
I have had numerous cat scopes over the years. A better choice IMHO would be a 100mm f/7 ED refractor on an altaz mount. Much brighter image (at f/7) yet capable of enough magnification to show the moon and planets well, dead simple and easy to use.
Basically the focal ratios available in the small catadioptric scopes range from f/10 to f/15. I had a Meade 4" f/10 SCT for a long time as a grab&go, it was ideal for solar eclipses - I used it on a sturdy camera tripod with a pan head.
Having been out of it for almost 20 years I recently bought a 180mm BlackDiamond Mak (f/15), thinking it would be good for lunar and planetary. However IMHO its focal ratio is too slow and I think the optimum is definitely in the f/10-f/12 range, especially as modern eyepieces are vastly superior to what was around 20 years ago.
I've looked through a 5" ETX several times (they are f/15) and compared to my old 4" Meade I thought it was pathetic. I also found it was very hungry on power, irritatingly noisy, and without mains power it was basically unusable.
For such a small scope, shelling out for an equatorial mount is really stupid when you may as well hand guide it anyway, the focal length is not really all that long.
But if you are still set on a Mak, your budget you could probably stretch to a 150mm Back Diamond Mak, and put that on an altaz mount, forget about equatorial for the time being.
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