The quality in the Celestron appears to be a bit hit or miss from what I read online. I bought a used M2 100ED and so far it looks exceptional through the zoom and fixed power 15mm/36X & 7mm/77X. I have a 5.5mm/98X on order and to push the envelope a 4mm/135X.
But, I also bought a demo 100mm Trailseeker another Celestron offering in the same 45* angle & 540mm fl. It does fine up to 45X. After that it slowly loses detail whilst starting to blur. This was a two day, NEAF Vendors & Exhibitors astrological expo that included 120 vendors, demo warrantied for one year.
When I contacted the vendor that I purchased from for replacement all I received was, "so sorry, but we do not have another demo & can only offer refund". In spite of this allegedly being inspected by Celestron and allegedly coming w/one year warranty.
As it begs the inquiry, What exactly are you warrantying agin? I bought the 100mm model to resolve at highest magnification and 45X isn't nearly enough. I've since lodged a complaint w/Celestron.
We'll see what steps they take and I'll report back to the forum. Now, had I bought w/o demo discount, paid $350 for the Trailseeker, they would've exchanged allegedly. The vendor claimed to have be in business for around 14-15 yrs if memory serves.
B&H currently has that scope for 474.99 w/Free $30-45 Essential Accessory, 1-3 Day Delivery. I've no idea what the "essential" acc. consists of in this marketing spiel.
My reasoning in warranty is the oem zoom is 22-67X for a 45X differential of which at 22-45X, 23X is roughly half. The second hand M2 100ED had no problem w/skinny zoom rendering resolution through 67X w/o losing detail or blurring. At the very least the Trailseeker should have the ability to resolve through the 67X on the oem zoom w/o incident. Sixty-seven X out of an 100mm objective is not much of a hurdle to clear.
If I were to make another purchase I would do me best inspect the scope at a brick n mortar dealer/vendor. And bring an assortment of 1 1/4" eyepieces w/at least one close to 100X and a tripod. Though not a traditional refractor telescope, due to upright prism, you still should be able to resolve at least to one power/X for every MM of objective lens diameter.
I have no idea how many out of 100 would or would not and as a rule people are more likely to post about a product if they are unhappy. The moon at 77X is exceptionally sharp in a "budget/one up upgrade" Celestron Luminos 82* eyepiece when looking through the M2 100ED.
I bought the M2 online, sight unseen w/o so much as an inquiry unto the seller.
Pot luck and I was lucky on that buy.