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iOptron CEM26 with or without Encoders - Opinions Please


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All, hopefully someone can shed some light on this as I have been around the houses on googling stuff and not really got a firm handle on the justification( if thats not too stong a way to describe this) to select the with encoders option and shell out nearly 2/3 the price again for -EC

The base model is just under £1k and the -EC model about £700 more expensive.

I understand the effect of encoders and the difference it makes to PEC and also unguided tracking accuracy - and its quite appealing however as always funding is a  consideration and so is the -EC going to make such a huge difference to the mount's guide performance (over traditional guide cam +PHD2) to dig deeper and spend the rather large amount of extras ?

The use case for me is that I want to do some remote widefield broadband imaging and get out of the observatory and into dark sites and if funds allow with one one the new ASI2600MC camera's with my trusty Samyang 135mm. So the image resolution will be 5.74 arcSec/Pixel with this setup

The other telescope I could use to image would be my AT72ED with 0.8 FF/FR so thats imaging at 2.25 AcrSec/pixel


I have a ASi120M and a miniguider scope that is very capabe and would be fine to guide the FL of 135mm or 344mm.


Would really appreciate views from anyone who is using the same mount or the previous model, CEM25 (-EC)


Its going to be roughly a 4-6 week wait for delivery, so if I want to get into some late summer imaging I would want to place an order in next few weeks.





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5 minutes ago, GazAstro said:

Are you planning on putting anything heavier on it later

At the moment - no, and probably never as I am looking at this purchase as a portable camping setup - may look at a  small triplet in the future in the 60-80mm range. I might be able to use it in my back garden with one of the new multi narrowband filters.

Thanks for the input, I am on the no EC side, unless somebody can make the case for EC



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  • 2 months later...

everything I read said the EC wasn't worth the additional spend. 


I have the non-EC 25P, if I PA perfectly and sort balance, I was getting 3 min subs unguided (but a few odd ones scattered in there), I only guide now out of habit


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You can get away a lot with short exposures, but in my observatory I always guide as my exposures are are usually 10 -20 minutes duration.


I went with encoders for accuracy and to avoid the need to Polar Align every time.


I always guide and unless I had something like the 10 Micron or ASA then I will continue to do so, but I always use an OAG on all my systems whether refractors or Reflectors.

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