Field derotation in Alt/Az?

I’m considering getting a Planewave L350 mount. I was wondering if it’s possible to use it in Alt/Az mode and do field de-rotation? I’ve done a quick search and I don’t see anything mentioned in the SGPro feature set about field derotation - is even supported?

No, sorry, this is not supported at the moment.

Yes, not supported in SGP. Might be in NINA since that has many more features in general. Voyager likely does at great cost.

One thing that many people are not aware of with de-rotators is that if you have a system that produces diffraction spikes you will get some odd spikes due to the rotation that are hard to process out. IMHO you are better off with a wedge for the L-350. I made that choice when I recently installed one. here is an article on the issue:

Th 350 is a totally fabulous mount with really only a few negatives:

  1. Cost (with wedge and pier the real cost will be closer to $20 K than to $10K)
  2. Weight - takes two to install unless you are Magnus Ver Magnusson
  3. Not for night windy sites (in other words, New Mexico).

The advantages are huge:

  1. Tracking and pointing blow anything else I have used (AP and Paramounts) out of the water!
  2. Slew speed is amazing at 50 degrees per second! You are there before you have time to think about it.
  3. Dead quiet slews and tracking (stay clear because it will whack you if you are not paying attention)! :face_with_head_bandage:
  4. No damn flips - I never realized how much time you lose due to the time it takes and the occasional failures. My productivity is up by close to 25% for narrowband.
  5. Maintenance is close to zero compared to other mounts because there are no gears, no PEC, no belts to wear out, no lubrication needed. That is why a lot of organizations have chosen it’s larger brother the L-500. Here is an example that is used for satellite tracking (which does not need de-rotation so Alt-Az is fine)

So bottom line is buy one and put it on a wedge at a permanent site if you can!

My system:


The L-350 can be used in Alt-Azm mode just fine. The de-rotation is built into the Planewave rotator-focuser software and its use is transparent to SGPro, NINA, etc.

If not using the Planewave rotator-focuser (IFR90), then the Optec Gemini rotator-focuser is a good choice. Optec provides derotation software that runs between the imaging app and the ASCOM driver for the rotator and focuser. It also reads the altitude and azimuth from the mount to know how to do the necessary rotation.

Just to note - the Optec derotation software works with any rotator and focuser as long as they (and the mount) have ASCOM drivers.


Thanks for the great information! I would love to have an IFR90, but that’s another $5,000. Probably better to go with the wedge (a mere $2,000 ouch!) and not have to deal with the spikes as I have an RC14 that I would be mounting on it.


An imaging buddy has an L-350 in alt-az mode and an IFR90 but he is doing photometry with short duration exposures. His observatory has limited space and he wanted to use a CDK14, so alt-az was really a necessity. Also, the PWI3 software that runs the IFR90 is poorly documented and I found it challenging to work with.

For long exposures (DSOs) and plenty of observatory space, I would recommend using the L-350 in equatorial mode.