Area 52

I see we're discussing two different situations. Let me explain how an AO helped me. I used a Meade 12" LX200, F:6.3 reducer and a self guiding SBIG-9E with exposures of at least 6 minutes each. Focal length of the system was ~1750mm. The full moon completely filled my image, so relatively small field of view. All of my data is supported by actual equipment measurements, not on mfg ads. At this magnification the atmosphere becomes an issue no matter the mount or optic quality. The optics or mount quality has nothing to do with seeing or transparency. They are two different subjects. That is why the professional observatories us TRUE AO optics. They have the best drives and optics money can buy. All low magnification does is bring the point spread down due to the effects of not seeing the sky for what it is. Meade and Starlight Express both use the vernacular AO loosely. True AO optics uses lasers to measure atmospheric distortion; thereby, changing the shape of the mirrors to correct for the effects on a microsecond level. Neither Meade nor Star Light express does this. They are more or less medium speed drive correctors.... and this isn't a bad thing. Meade makes inexpensive mounts with relatively so-so optics that is cost effective. Periodic error can be +/- 10 arcseconds. An AO was critical to getting my error down to an acceptable level at my F ratio. $1500 for an AO sure beat spending $20,000 for a Mathis mount plus optics. Very short exposures can "beat the ceiling". In other words, the effects of atmospheric distortion are minimized. By using very short exposures stacked together using inexpensive equipment, I have seen planetary pictures that are absolutely incredible. Results, high magnification with low atmosphere effects. But the effects of long exposures bring to light the demons of the sky. My error was finally reduced to ~ +/- 1 arecsecond. Not bad. This included atmospheric conditions .... on good nights. Consider also the altitude of the object being imaged. Looking over head, you looking through one atmosphere. But go down 30-40 degrees and see what happens. Overhead, I could capture 21st mag asteroids. At 30 degrees down, I did good to catch 17 mag rocks. How many atmospheres and how much mud was I looking through? I guess what I'm saying, If you're using low magnification, you have fairly good equipment shooting long exposures, an AO is not necessary. But if the image shows effects either from the mount or atmosphere (it will not help bad optics) then it can be of benefit. But be forewarned, expect to spend many hours extinguishing the dragon's breath.

It's all about the atmosphere, period. I've seen perfectly good scopes sold because the owner judged the optics visually ... or by imaging on bad nights. No consideration was given to the atmosphere. I used a CCD guided telescope assisted by a SBIG AO from 2001 to 2008 discovering asteroids. Sub-arcsecond tracking.. or for a matter of fact... arcsecond tracking for any period of time is a true rarity at best... even with an AO. The most steady seeing I had was during foggy weather. The Minor Planet Center (MPC) recommends ~ 2 arcseconds per pixel. This recommendation recognizes the rarity of arcsecond tracking/seeing and the effects on an image. I recommend reading the IAU/MPC site on effects of atmospheric conditions on imaging. Using UCAC4 or Nomad catalogs to reduce the raw data allows for astrometry accuracies of ~ .2 to .3 arcseconds through advanced algorithms, only. My scope was set at 2.7 arcseconds per pixel. Using UCAC 3, I reduced my residuals on average to~ .3 arcseconds. Again, my scope with AO VERY rarely tracked to arcsecond accuracy for any period of time. AO's are not for the week of heart. My AO/scope combination was a pain in the rear to setup. It took weeks to get the numbers working, but, without a doubt, I would never have achieved the tracking I did without it. According to the manufactures, your bell curve can be reduced by approx. 25-30%. It is my thought that adjusting a mirror is faster with less vibration than trying to reverse a motor with backlash adjustment. A tip: Chasing turbulence/seeing at high rates is counterproductive. I recommend corrections in the .5 to 3 - 4 second range. You don't want to chase the seeing but giving it time to allow for a small averaging effect. Again, the IAU-MPC has a lot of information on this subject.