Other Avoid these like the plague if you have ZWO extenders


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I purchased some TPO extenders from OPT for use with my camera backspace for both the Celestron and the Williams Optics.

I knew the price was too good to be true. I have now basically lost the use of 2 ZWO M42-M42 21mm extenders after the TPO ones cannot be removed. And they were not tightened down that much.

Tried to separate them, including putting them in the freezer since the metal thickness was different, thinking that the thinner would contract faster... nope they stayed bound.
Channel locks you say?


Nope, didn't work. In fact, the first one I tried (StellarVue brand) was as bad... tried loosening them the same way... but the channel locks ended up bending the thin walled StellarVue so much force was applied.

Even placing in a vice and then using channel locks did not work... so I decided to see if I could slowly bend the sides of the StellarVue and get it loose... nope, this is what it looked like when it finally came out


It ended up scoring the female threads on my ZWO M42-M42 extender, and after this I'll be darned if I'm threading ANYTHING to the two that are still together nor to the 30mm one I have in my case.

TIme to buy 4 more ZWO 21mm extensions. Five will give me the 105mm backspace recommended for the NexStar 8se.
Well that sucks. When I have two pieces of Aluminum stuck together I use two pieces of inner tube rubber. Cup one piece in each hand and grab each stuck piece. Haven't lost a war with AP gizmos yet! I think the reason they stick is they are so thin that they change shape, and if they are different masses they warm or cool at different rates.

I have to admit sourcing spacers is 10x tougher than spending a couple grand!
Well that sucks. When I have two pieces of Aluminum stuck together I use two pieces of inner tube rubber.
Tried that using an old bicycle inner tube. It won't break loose for any amount of money. I even went direct metal to metal, not worrying if I marred it or not as nobody would see it in the dark! An old trick I learned a long time ago was to stick them in the freezer for a short amount of time, the thinner metal should contract faster, loosening it up... no joy.
It's like they bonded to each other. I've got one sitting with some good old fashioned Kroil on the one that is still stuck together. If that doesn't break it loose I'm not sure what else to try. Got 5 21mm M42-M42's in my basket at Agena right now, along with 2 more of the M42-M48 threaded adapters that fit between the flattener and the T2-M48 16.5mm extender (seems like one of the more likely pieces to "misplace" since it's so small).
Needless to say, the review I left over at OPT was not very good. One star and photos.
I think the next attempt, since the Kroil hasn't done any good, is to take my Dremel with a cutting wheel and SLOWLY cut through the thin walled one and try not to score the threads in the ZWO one. Pisses me off that $21 worth of extenders trashed $40... and I honestly don't expect OPT to stand behind them at all. If they do, I'll REALLY be surprised. I have requested an RMA for the two unused and undamaged ones that will NOT be used on any equipment I have.
Well, OPT's answer was "You can use straps to loosen them we have discovered".
Yeah...... like I'm really going to carry around a strap setup and a socket wrench to attach it to simply to remove their crappy extenders.

They did give me an RMA for those that I have not used (and they have been packaged at light speed and sent on their way for a refund)... but as I fully expected, not a peep about the ones that screwed up.
I was able, using the strap method (an oil filter strap to be exact) to get their "great" cheap-ass extender loose from the ZWO one... so instead of losing 2 quality ZWO extenders, I only lost one.
I'd be surprised as hell if OPT did anything about the screwed up one... and needless to say, it's the last time most likely I'll be ordering anything from OPT telescope.

Of all the vendors I've dealt with so far... the best one has been Agena Astroproducts.
I currently am applying a small amount of bees wax to the threads when I place these together. It serves a dual purpose... it helps seal and also lubricate the threaded area.