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Hi Night-Vision & All,
Assuming the LX90 has a similar database to the LX200, a good pair to use early in the evening at this time of year would be Achernar (Alpha Eridani) and Enif (Epsilon Pegasi -- a 2nd magnitude star about 1/2 way between the bright star Altair and the Great Square in Pegasus) which are both in the list of alignment stars for the LX200 -- I assume they are in the LX90 database of alignment stars too.
The other stars you mention are okay as well, but these two are in the early-mid evening each a bit either side of half-way between the horizon and zenith and more than 150 degrees apart. I think from memory the minimum recommended distance for alignment for the LX 'scopes is 45 degrees (two adult hand-spans and a bit) -- though in my opinion, the further apart the better (within reason) . Avoid aligning on stars close to zenith -- they make for poor alignments and ones close to the horizon as well because of atmospheric refraction.
Make sure you follow all the other instructions in the manual and that the tripod is on a very firm footing that is not "springy". Likewise make sure all the nuts and bolts etc holding the tripod together are firmly screwed-up (but don't over-tighten either) and the tripod spreader (with the bolt that screws into the base of the 'scope) is fitted properly.
Assuming all this and that you are taking care in centring your alignment stars reasonably accurately during the course of the align procedure (use medium to high power for this), my next suspect for the alignment issue is indeed mirror-flop.
Even if there is no actual flop during the align procedure, if a flop occurs while you are doing a goto to a subsequent object of interest, it will have pretty similar effect. After doing an align, do a few test slews to objects with an obvious centre -- at this time of year, NGC 104 (47 Tucanae) and M2 are good (there are plenty of others too) to see if it is all behaving as it should.
Hope you get it all together real soon.
Best,
Les D
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