在cn看到的一段话

Posted 12 May 2015 - 05:52 AM                                                                         
The answer to your question is still up in the air.

The EC version has an SDE error of up to 4 arc seconds peak to peak and is too fast to be guided out.  This means that you will not have nice, tight, sharp stars at long focal lengths.  However there are a few who are very happy with the results of a guided EC mount and have posted pictures that seem to look just fine.  However math doesn't lie.

The NON-EC version does not have an encoder and thus no SDE error. So in theory you could train the PE down with PEC and then guide on top of that.  This would actually make it a better performer for longer focal length systems.

Having said all that, iOptron keeps saying/promising that they will have the SDE error addressed via a firmware patch.  In fact they have recently released some new firmware that is supposed to reduce it by 30% ish.   I think we are all waiting for some PE logs to see for ourselves.  If they managed to improve it enough, it may be worth a second chance.

Right this very second, I'd say the non-ec is the way to go.  If you are not in a hurry, wait a few months and ask again.

还有这个情况?

黄瓜兄不给翻一下？

my147258 发表于 2015-5-21 15:47
黄瓜兄不给翻一下？

大意是说ec版的一个小问题能够导致跟踪误差，但是可以通过固件优化进行优化

那个SDE是指的码盘分度误差。凡是采用码盘都会面临这个问题，就看谁家码盘做得精，以及软件纠错能力强。Renishaw码盘是公认的绝对高精度，SDE可以忽略不计。但光码盘和读数头就要2000多美刀。SDE频率很高，一般情况下不易察觉。导星时将曝光时间设为一秒左右才能发现。CN上报道的几个CEM60EC不同测试结果SDE大致为峰峰值2角秒，4角秒是极端情况，本体均方根PE仍然低于0.5角秒。艾顿近期发布了一款针对SDE的升级固件，据说能将SDE降低30%-50%，但目前还未看到用户的实测证实。如果真能做到将SDE降低那么多，CEM60EC可能就是真正意义上的精品。毕竟那些采用Renishaw高精度码盘的赤道仪也只能做到这样。我想艾顿是在扬长避短，从后期软件容错纠错上下了功夫。