Frequently Asked Questions



Will this work with my ccd autoguider camera?

MetaGuide relies on the benefits of video for accurate, low latency guiding. Many commonly used guide cameras do not have a DirectShow video driver and they simply will not work with MG. Examples are the SX Lodestar, and the Orion StarShoot. Most planetary video cameras will work. Color video cameras will also work, but there is a loss of sensitivity with the Bayer matrix. NTSC and PAL video cameras will also work, with a Video2USB converter - but they tend to have lower resolution since they are analog

USB, Firewire, and Ethernet video cameras should all work, as long as they have DirectShow drivers.

MetaGuide gives an FWHM of 1.1" but I know my seeing is much worse!

That's the idea. The goal of MetaGuide is to use Lucky Imaging methods to create an aligned and stacked view of the star that is smaller than the typical seeing over a 1-2 second timespan. This "Aligned" FWHM is labeled as AFWHM and it shows what MG can do given the current seeing - with video and novel centroiding. So it is expected to be smaller than "seeing."

Recent versions of MetaGuide include a calculation of seeing every 2 seconds - and that really should match the "seeing" conditions. But note that it assumes the telescope is well focused and has large enough aperture not to be limited by diffraction. In general it is hard to make a reliable "seeing" measurement - but the value provided by MG should at least give a ballpark value, and let you tell the trend from one night to another. If you use OAG, the guidestar "seeing" value will be heavily affected by the off-axis appearance of the star - so again it should not be taken literally.

Why won't my ASCOM driver connect?

Try connecting to the ASCOM Generic Hub first - and then to your mount. MetaGuide uses ASCOM 5 style early binding that was later discontinued.

How do I install on Windows 8.x?

Run the installation as administrator and use Windows 7.1 compatablity. If this doesn't work, try other compatibility options. It installs on most Windows 8.x systems, but some do have trouble.

Why doesn't my DMK camera work?

Unfortunately some DMK cameras do not work with MG currently. You can try and they might work, but currently the problem has not been identified.

Why doesn't my ASI camera work?

The ASI drivers changed in April, 2014 and you need to use the latest MG version, along with the latest ASI drivers. Both the camera and its st4 port should work with MG.

Autoguiding is perfect with modern software. Why use MetaGuide?

MetaGuide focuses on novel centroiding methods to reduce the impact of seeing, and low latency for prompt corrections to the mount. This allows your mount to act as if you are using adaptive optics with 1 second corrections - without the added complexity of AO.

Autoguiding performance is always limited by how well it is tuned, and in order to tune you need good feedback on changes to things like aggressiveness. MG is unique in providing accurate guide error plots that update every 0.5 seconds - so you have a "live" view and prompt feedback on changes.

MG is also unique in providing a "GuideView" that shows a live video view of the guidestar as it jiggles around the target pixel location.

Won't I be chasing the seeing?

I consider "chasing the seeing" to be mostly a myth that is caused by guiding systems that speak in terms of pixels rather than arc-seconds. If you switch from a small guidescope to OAG, the error in pixels will be huge and it will look like the guiding is very tricky. But MetaGuide displays guide error and fwhm in arc-seconds at all focal lengths, so there is no big change in moving to OAG. Instead, you get *improved* centroiding, and the only thing you chase is errors in the mount - which is a *good* thing.

My guide logs only show 0.1 pixel error. Isn't that good enough?

Guide logs are only an indication of what the autoguide system *thinks* it is doing. If the centroid isn't very accurate on a sub-pixel basis, the actual motion of the star on the image plane may be much larger than the recorded motion of the centroid. This is particularly true with a well focused guidestar in a short focal length guidescope. And, of course, flexure may make the problem even worse - with perfect guide logs that contrast with oblong, sausage looking stars in the image.

MetaGuide always tells you the fwhm, in arc-seconds, of your guidestar. If the fwhm with a short guidescope is 25", it will be very hard to autoguide at the scale of 2" fwhm in your images. Instead, I recommend very small and round and well sampled guidestars that are 2-3" fwhm.

My guidestars are ugly but can't centroiding algorithms find the true center so it doesn't matter?

Any error in the shape of the guidestar will translate to errors in the centroid, and centroid errors lead to errors in the image. I would try to keep the guidestars small and round for best centroiding. In order to make prompt corrections for the mount, the guide exposures need to be short and the guidestars will be somewhat distorted by seeing. MG uses novel centroiding to guide on the hot spot of each video guide image and reduce this effect.

How do you know it works?

The two ways to validate results from MG are in the match of the Airy pattern to theory, and the smallness of stars in long exposure images with mid-range equipment. The Airy pattern can be revealed even in mediocre seeing, and shows a good match to diffraction theory. This indicates the novel centroiding works for collimation.

MetaGuide has demonstrated sub 2" fwhm's in 10-15m exposures with mid-range mounts that have relatively high PE, and cost much less than high-end mounts with expensive bearings. I commonly see similar equipment produce stars in the 3.5-4.5" range - and I think the autoguiding software and technique are factors in explaining the difference.




Support

For support, please send feedback and questions to the AstroGeeks Yahoo group.

Contact (spam encoded address): freestar8n *at_t& yahoo _d_ot_t+ co*m

Guiding

Low latency guiding with video. Quick and accurate corrections for mid-range mounts.

Achieve tighter and rounder stars than with long guide exposures and standard centroid algorithms.

Let MG find and select faint guidestars as they come into view so you don't have to squint at the screen.

Collimation

Collimate using a star with the telescope aimed at the correct angle to the sky. Just center the coma dot on the star while the mount re-centers it. In better seeing you can use high power and collimate on the in-focus diffraction pattern.

Take an annotated and scaled image of your collimated star to show how well your star diffraction pattern matches theory.

Seeing measurement

Measure size of the star spot as it moves around over each 2-second interval, with live plots. Can be used as a dedicated seeing monitor with a telescope, or just to check seeing conditions

Drift alignment

Measure the dec. drift of the mount quickly so you can make rapid polar alignment adjustments to null out the drift.

Periodic error logging

Log periodic error in detailed formats for analysis in other tools. These measurements are taken every 0.5s with an accurate centroid, allowing high resolution studies of your mount behavior including gearbox and other noise. This may be the most important type of error for good guiding compared to the slower and more easily corrected terms.

GuideView mode

GuideView mode lets you watch the live guide corrections in video mode so you can see the small, fast motions of your mount that are the key to getting tight stars.