I used a mirror in my shed, but i wouldnt say that was "easy".
Also, orthogonality testing is really a 2 stage process, but stage one is a lot harder without the right tools.
Ie stage one is to ensure the DEC axle is orthogonal to the RA axle ( normally a factory process )
Stage 2 is to ensure the OTA is orthogonal to the DEC axle
There are lots of methods posted on the net, but Up where you are, i reckon the easiest way to do a stage 2 check is to put the scope on a wedge and "mechanically" aim the wedge at Polaris, not the pole.
Then, you simply declutch the RA axis and spin the OTA ( preferably with a camera for ease of use ) and watch what happens.
ie if you start with the DEC axle horizontal, you adjust the azimuth of the wedge to roughly centre polaris,
then set the DEC axle vertical and use the alt adjustment to centre polaris.
Now you reset the axis to horizontal and note where Polaris is on the screen
Now manually rotate in RA by 180deg and again note where Polaris is
If Polaris effectively describes a circle as you rotate, then the OTA is parallel to the RA axle.
If not, you need to adjust accordingly.
There are 2 very small threaded holes in the back of each of the OTA saddles.
You need to get some screws that fit into those holes ( i dont have the sizes handy ).
These temporary screws effectively act like jacking bolts on the OTA locking bolts, to allow you to provide a fine adjustment of the OTA relative to the saddle.
As such, you release the tension of the three OTA locking bolts on one side of the OTA, and use the jacking bolts to tweak the position until the spin test results in Polaris doing donuts in the FOV of the camera ( or eyepiece )
Andrew Johansen Melbourne Australia