Anyone have experience with Starlight Express Adaptive Optics?

I assume you looked into belt mods and such? Just mentioning In case you haven't

Yes I’ve used one to compensate for differential flexure on my dual rig. Works fine.

Kevin Dixon:
I have used the SX AO unit for years with my SCTs and get great results with it.  I control the AO through PHD2 guiding software which works quite well.

Clear skies,
Kevin

Kevin,

thanks for your reply.   Do you happen to know the optical backfocus of the device only using the included M42 adapters on both ends?

I want to put it on the end of Starizona SCTCORR-4.  I can take the tilt plate off my existing OAG/filterwheel/ares-m camera to gain an extra 5 mm (50 mm instead of 55 mm).

The SCRCORR-4  requires 90.3mm +/- 2mm which leaves 40.3mm +/- 2mm for the AO device.

from what I can tell from their drawings (which don’t include their device-only optical path distance but instead distances with their OAG) it’s going to be tight.

I used it on my Losmandy GH8 with a 700mm focal length refractor. it improved guiding immensely .

Kevin Dixon:
have used the SX AO unit for years with my SCTs and get great results with it.  I control the AO through PHD2 guiding software which works quite well

I have two of these, a main unit and a spare. I have used them on a TOA 130/Paramount ME, an AGO 10 inch iDK/Paramount ME, and currently on a Planewave CDK 14/Planewave L350. They work great but do take a bit of getting used to in terms of setup and operation. Once that is done they work very well.

I have used the original SBIG mirror type AO as well back in the day but SBIG is kind of yesterday's news and I have not used one of theirs in years. The SX unit will work with pretty much any camera and OAG if you have the right adapters, usually from Precise Parts.

I chose it because it works great with PhD. That is mostly because one of the original PhD programmers, Andy Glasso, had one and that was used to develop the support for it within PhD.

I would ignore all the nonsense about "high speed guiding" using teeny sub-second guide exposures to give you clearer images. It will do nothing for crap seeing. That will cause more problems than it solves. Treat it as an "optical guider" that takes some of the load off the mount. It is easier to move a one oz. glass plate precisely than a 50-150 pound mount. I typically use guide exposures between 5 and 7 seconds with my CDK (2563 mm) but that is with a high end direct drive mount that already has great tracking.  In fact, it will help with a poor mount but will not totally fix a bad mount because that would involve the aforementioned short guide times that are best avoided for many reasons.

The bottom line is that it makes guiding less "fussy" even with a good mount and with a less than ideal mount may help at least some, although that has it's limits. Current setup with Nightcrawler and Astrodon MMOAG and Moravian camera shown:

FYI, on a good night I typically see in the vicinity of .15 arcsec, on an average night maybe .25 arcsec and on a poor night about .35 or more.  Of course that is more seeing and/or wind than anything and is also at a good site with high end mount and optics.

I am actually a bit surprised more people don't use these but then most people probably use refractors that are well under 1000 mm where AO would not be of much benefit. I would put the break point where they are worthwhile at about that focal length.

Those who use the AO unit from Starlight Xpress, have you had trouble with your calibration frames?

After fiddling with one for a while I finally started to use it an anger last night and in the morning when I stacked my subs I noticed circular gradients throughout the field.  I took a look at the mast flats and this is what I'm seeing:

red:


Green:

Blue:


Lum:


And here's what a Red flat looked like before I installed the AO device:



And those circular gradients are showing up in my masters:

red master:



Got a nice fat circular gradient that aligns exactly with the flat.

I'm fearful that the light from the image was taken at a different "tip" angle than the light from the flat and what I'm seeing is the master is the residual.

Has anyone else had a similar problem with these devices?

@Bill McLaughlin Can you provide any feedback?

Thanks.

Yes, this was taken with the AO device powered immediately after all the subs for the target were taken (via the "Immediate Flats" instruction of the Target Scheduler plugin)

The AO unit is connected to the focuser tube of an Askar 107PHQ (petzval design) so it's quite far from the lens elements in the telescope and the OAG/FW/Cam is attached directly to the other side like shown in your picture. 

I'm assuming the FW is built in to your camera?

@Bill McLaughlin I know this is reviving an old thread, but I can't help but notice you don't have the ST4 cable connected to the SXV-AO. How are you sending bump commands to your mount? If there is a way through PHD2, I'd like to know how.

Try re-meshing your worms and loosening the retaining rings for each axis. I average 0.15 on my 6R after a quick loosen of these rings.

My mount tracks fine with the AO off, but doesn't seem to receive or react to bump commands over USB. Might be a calibration issue, but I don't know enough about what I'm looking for in PHD2 with the AO to know if it's calibrating correctly.

The AO calibration results should look much like those from the mount when looked at in the calibration review in PhD. You need to be sure you do not stop calibration too soon as well. It does the AO first and then says "complete" but it is not since it then goes on to do the mount calibration (IMHO, this is a bit deceptive and needs to say something like "AO calibration done, starting Mount calibration"). The results under "review calibration" should look something like this (of course your angles and numbers will be different)



You also want to be sure that you have "bump on dither" and "Enable AO corrections" checked. Your numbers may be different than below and I have disabled backlash since it is a direct drive mount that has none.

Thanks for the tip, but my current problem is the star drifts far enough that the mount should bump back, but seemingly nothing is happening. Thanks for the tuning tip, but I'm unfortunately not at that point yet.

That's worth a shot. Thanks