alt-az vs GEM

If one were looking into buying an 8" to 10" SCT for amature level astrophotograghy, what is better, an Alt-Az mount or GEM? Both have plenty of goto, auto tracking capabilities from the major mfr's. But does one have a clear qualitative advantage over the other?

As far as I understand it the Alt Az versions will suffer from field rotation during long exposure astrophotography. There are devices you can buy to counter this though.

Hope this helps.

Clear Skies,

Jack

You will need some kind of equatorial mount, or as Jack mentioned, a field derotator.

The simplest thing to use is either a GEM or a fork mount with a wedge, which converts it to an equatorial. Most astrophotographers use the GEM, because it is easier to balance, is more stable, and less prone to vibration.

I preferred the wedge & fork for an eq mount -- seems to me the GEM undoes much of the portability advantage of the SCT.

Leif
I tried an LX200 for imaging and it was fair for lower focal lengths, but even guided it was difficult to get good images above 800mm focal lengths due to high PE. If you go with an LX200 or Celestron equal the 8" OTA with a 3.3 focal reducer may be the better fit than the longer focal lengths of the 10" OTA's.

I now have a CI700 GEM and it is much better. Even with a GEM, I would recommend a higher quality one for serious imaging. A used CI700 (around $1400) or a Losmandy G11. But these are not very portable.

For visual though, I still prefer the LX200 fork mount in alt-az mode.

Hope this helps.
Steven Jindra