If you have a guider with a big enough field of view that you can get a guide star most of the time without having to offset your target or rotate your camera, or if you have a rotator, you can use ACP's "smart start" autoguiding feature. ACP will select the guide star and adapt the guiding exposure interval for variations in guide star brightness and filter transmissivity (for internal guiders), within limits! If you have a short enough focal length and a large enough internal/off-axis guide chip, or if you have a rotator, then ACP's adaptive guiding exposure interval calculation will almost always allow automated operation.
It is highly recommended that you read through Jim McMillan's excellent Autoguiding paper right now (Acrobat Reader required). Jim has a great deal of experience with high-precision unattended autoguiding using ACP, and is largely responsible for the advanced capabilities of ACP's smart-start autoguiding. After you read it, come back here and start with Smart Autoguiding Setup.
This info is also covered in Step 9 of Getting Started, but it's important so we're repeating it here!
It is essential that you have guiding within MaxIm DL working reliably with your setup before trying to use it with ACP's automation. There are many settings in MaxIm's advanced guider setup windows. Getting it right can be a bit daunting; just be aware that guiding is complex and getting the parameters right is just part of the fun.
If you are pulse-guiding through the telescope (as opposed to using guiding relays) be sure to select ASCOM Direct in MaxIm. Do not use "Telescope". If you do, then MaxIm's own (simplified) observatory control features can become active and confuse things with ACP. Do not connect MaxIm's Observatory Control to ACP's hub or the telescope, period!
You also must calibrate your guider once as described in the section Calibrating the Guider. With ACP, it is not necessary to recalibrate the guider unless you change your optics or guiding imager, even if you have a rotator! Of course, you'll need to recalibrate any time you change your guider optics or guiding imager.
For internal and off-axis guiders, you absolutely must have a planetarium with an accurately scaled field of view indicator.
If you have an SBIG or StarlightXpress adaptive optics unit, see Using Adaptive Optics.
To get the best operation from robotic imaging with your guider, you need to provide some settings to ACP's smart autoguiding.
Read through this and gather the data, then in the next section, follow the steps. Be patient! Your patience and care will pay off.
Maximum unguided exposure interval. This is not strictly a guiding parameter, but it's on the Guiding tab, so... this is the longest exposure that your system can take without guiding. It is used by ACP to make guide/noguide decisions on each image. OPTION: Normally, ACP will aggregate the exposure time on a single target through a given filter in making this decision. For example, if you take 10 exposures of 60 seconds each, ACP will use 10 x 60 = 600 seconds to make the guide/no-guide decision.
The starting guiding exposure interval. This is not a critical value with the smart autoguiding, however it is the first guider exposure interval that ACP will try. It's much better if this is on the long side, as the resulting clean star images will make ACP's exposure optimization calculations more accurate, resulting in faster guider adaptation and startup. If you have filters and an internal guide chip, choose a value that will work for guiding through your lowest transmissivity filter. Again, for more info read Jim McMillan's excellent article Autoguiding. It's contained within this help document!
The shortest guider exposure interval that you can use. Some mounts, like the LX200 Classic, cannot accept guiding corrections more than once every few seconds. Others can handle much higher correction rates. Generally, the faster a guider can correct the mount, the better. But there is one exception. Too fast an update rate can end up "chasing the seeing" resulting in poor guiding. It's up to you to choose the minimum guiding exposure interval that works best for your mount and your typical conditions. Keep in mind that MaxIm provides a separate "delay between corrections" setting that can allow you to slow the correction rate even when using short guiding exposures. Using this feature is important for mounts that cannot accept high update rates.
The longest guider exposure interval that you can use. Generally, the longer this can be the better, as it will allow you to use fainter guide stars and/or work through filters of lower transmissivity. The limit is based on the tracking noise and periodic error in your mount. It's up to you to decide how much guiding degradation you can accept at the long-interval end of the envelope.
The maximum error in guide chip pixels that you will accept at guider startup. ACP will monitor this error after starting tracking, for up to 10 guider cycles. If the guider never gets below this error, smart autoguiding will fail. If this is too large, the shutter will open with too much guiding error, and maybe even a lost guider. If you don't know what to use, start with 1 pixel.
The lowest signal-to-noise ratio at which your guider will reliably track with acceptable random errors. Remember that ACP will try to guide at this lowest SNR in order to maximize the guiding update rate. If you pick too low an SNR, guiding will be too noisy and cause blurring of stars. But if you pick too high an SNR, then you might not "get a guide star", especially if you're guiding through a low transmissivity filter. Another factor that strongly influences this is the pixel scale of your guider. If you have a guider whose pixel scale is much larger than the seeing, then you're asking it to guide to within a smaller fraction of a pixel, and thus you'll need a higher SNR to stay within your guiding tolerances. If you don't know what this number is, start with 3.0 and then work up from there in steps of 0.5. Make some runs and observe the guiding. If it fails to start guiding, your SNR is too high. If it guides too roughly or loses guide lock after multiple guider cycles, your SNR is too low.
The guide sensor configuration (no rotator, rotated internal, rotated off-axis pickoff). You should know this already!
The guide sensor plate scale (arcsec / pixel), required for dithering calculations to be in units of main imager pixels. This is in the Imager preferences tab.
The guide sensor rotation angle (only if you have a rotator). If you are using a rotator, ACP needs to know the orientation of the guide sensor with respect to the main sensor. This will be done for you by the CalibrateGuider script (see below).
Whether your German Equatorial mount reverses the Y guiding signal on a flip. With guiding cables this is virtually never the case. However with software guiding (PulseGuide, DirectGuide, with MaxIm set to ASCOM Direct for guider connection) some German Equatorial mounts reverse the Y signal on a flip. At the time of writing, mounts that do this include the Bisque Paramount, Sidereal Technology drives, and the PlaneWave STI system. If you have problems with the guide star zipping off the chip vertically on 0 degree PA images when looking West, try enabling this option. Otherwise, leave it off. Leave it off for simple equatorial mounts.
Some mounts guide better overall with declination compensation turned off. If you are unsure of this, just leave it on (the default). On the other hand, if you know with confidence that you want the guider's declination gain compensation to be disabled, you can do this in the guider setup.
Once you've decided on the above, you can set up the smart autoguiding. If you have an AO, skip this section and go to Using an Adaptive Optics Guider. Otherwise, click this button
to display the ACP Guiding setup panel.
First tell ACP what the longest permissible unguided exposure interval is for your system. Thereafter, any astronomical image whose exposure time exceeds this value will be guided automatically. Set the Disable aggregation option (at the bottom) if you want the decision to be made only on individual exposure lengths.
Set the initial guiding exposure interval. Remember, set this on the long side. Try 5 seconds at first.
Set the maximum guiding exposure interval, seconds (default 10 sec.).
Set the minimum guiding exposure interval, seconds (default 0.5 sec.)
Set the maximum guiding error during guider startup, pixels on the guide chip (default 1.0 pix)
Set then minimum signal to noise ratio for guiding (default 3.0)
Select your guiding configuration from the drop-down list.
The guide sensor angle will be filled in by the CalibrateGuider script (see below)
Unless you have a good reason not to do so, make sure that "Use guiding declination compensation" is turned on.
Calibrating the Guider
If you have an AO, disable it temporarily and do this using conventional guiding. For the AO, conventional calibration is needed only to determine the guide sensor angle. The AO drive does not need calibraing (see Using Adaptive Optics).
If you manually calibrate MaxIm's guider and you have a German mount, you must calibrate it with the scope looking east of the meridian, and the Pier Flip option off. Also, you must set the declination of the point at which you calibrate. You must also manually determine the guide sensor angle (see Determining the Guide Sensor Angle Manually). For all of these reasons, I suggest you use the CalibrateGuider script as described below!
Before doing automated runs, you must calibrate MaxIm DL's guider. ACP comes with a standard script, CalibrateGuider.vbs that does this automatically. For external guide scopes, it finds a nearby bright star with no other stars in the area, sets the declination, sets the "Pier-Flip " state for German mounts depending on which side of the pier it is on, calibrates your rotator to the equatorial system, sets the rotator to 0 degrees PA, and performs the entire calibration procedure automatically. If you have an internal guider or off-axis pick off, you must first set the scope up so that a bright guide star is on the guide sensor (see How to Win the Fight with Internal and Off-Axis Guiders). Then the CalibrateGuider script will just calibrate, without moving the scope.
As usual, load CalibrateGuider.vbs into ACP's scripting console and click Run. That's all there is to it!
Starting with MaxIm 6 a multi-star guiding mode is available. ACP will detect this and modify its smart-start process to accommodate multi-star guiding. Basically, it is necessary to let MaxIm choose the guide star rather than ACP, and from there on the successive refinements and dithering all work the same way.
WHen you first enable multi-star guiding in MaxIm DL, it is necessary to either exit and restart MaxIm, or at least take an exposure using MaxIm's guider contrrols and then start it tracking for a few cycles, again with MaxIm's guider controls. If you don't do one or the other, ACP will not be able to tell that multi-star guiding is enabled. This is an issue only when you set up the guiding for the first time.
Guider Dark Frames - Guiding on Fainter Stars
You can often benefit by having MaxIm subtract a dark frame from the guider's images. The best way to do this is to select Simple Auto-Dark in MaxIm's camera settings for your guider. It's a bit hard to find, so check the MaxIm documentation. Guider calibration may need to be set to None if you are using an SBIG AO (see below).
Using an Adaptive Optics Guider
Explicit support for the SBIG, StarlightXpress, and Orion adaptive-optics guiders is provided by ACP. Automated AO operation involves sophisticated adaptive choice of exposure interval and monitoring of RMS wander after AO startup. If you have a camera rotator, be sure to also read Using Rotators and specifically How to Win the Fight with Internal and Off-Axis Guiders.
For SBIG units, automated AO exposure calculation in ACP may require that MaxIm's guider image calibration be set to none. If you run into trouble, do not set it for simple auto-dark or full calibration. It's OK to image-calibrate StarlightXpress AO units.
In order for this to work reliably it is vital that you first get the AO to operate reliably manually in MaxIm. Once you have done that, you should adjust ACP's guiding preferences from those described above as follows. Click this button
to display the ACP Guiding setup panel.
First, turn on the checkbox Guider is an Adaptive Optics unit.
Now tell ACP what the longest permissible unguided exposure interval is for your system. Thereafter, any astronomical image whose exposure time exceeds this value will be guided automatically. Set the Disable aggregation option (at the bottom) if you want the decision to be made only on individual exposure lengths.
Set the initial guiding exposure interval to 5 sec.
Set the guider cycle time to 1 sec.
Set the maximum guiding exposure interval to 5 sec. An AO running at a rate below one fifth Hz is not going to be effective.
Set the minimum guiding exposure interval to 0.05 sec. Yes, 0.05 (5 hundredths). This is essential if you want your AO to operate at 10 Hz or more.
Set the minimum signal to noise ratio to 2.5 for the SBIG AO and 6.0 for the StarlightXpress.
Set the maximum guiding error during startup to 2 pixels.
Now create an observing plan using your Luminance or Clear filter that puts a bright star on the guide sensor and run it. The AO should start up successfully and run at a reasonably high rate (5 Hz or more).
How ACP's Smart-Start Autoguiding Works
ACP's smart-start autoguiding can greatly improve the reliability of guiding in an automation scenario. With an internal guider chip sitting behind filters, and for variations in guide star brightness, guiding exposure intervals need to change, and ACP adjusts them automatically.
What makes ACP's auto-guiding "smart"?
ACP selects the guide star instead of MaxIm. It uses PinPoint to scan the full-frame guider image, then picks the brightest star that (a) does not have a companion within 20 pixels, and (b) is not within 10 pixels of the edge of the guide chip.
Guide star brightness is measured via the total background flux of the star instead of just using the brightest pixel. This eliminates false selections from cosmic ray hits, etc.
It then accurately measures the signal to noise ratio (SNR) of the selected guide star. PinPoint's local background mean and standard deviation of noise is used to calculate background flux within the same aperture area that is used to measure star flux. The ratio of these two flux values is an accurate measurement of the SNR. Even if a star is embedded in nebulosity, or if the guider has a large bias/pedestal, this measurement will give an accurate SNR. This is vastly superior to "peak pixel" schemes used in other software.
Based on your setting for minimum SNR for guiding, ACP adjusts the guiding interval to be as short as possible and still achieve your minimum SNR. This allows the guider to update the mount as often as possible while maintaining a clean guide star lock. Thus your guiding will be as smooth as possible for your guider's sensitivity and the effect of any filter you may have in front of the guide chip. Note: you can specify lower and upper limits on the guider exposure interval. Some mounts can't handle too fast an update rate. If the update rate is too slow, tracking errors can build up between guider updates and nullify the benefit of guiding.
After starting the guider in tracking mode, ACP watches the guiding errors and only lets the main imager start exposing after both X and Y residuals are below a user-specified tolerance (default 1 pixel).
If the residuals don't both fall within the tolerance after 10 guider update intervals, it will re-try the entire guider startup process, starting with step 1 above. It repeats this again two more times, recalculating SNR and exposure each time.
If you specify the same target coordinates in sequential targets, and if you either have an external guide scope or no filters, ACP will leave the guider running across the sequence of co-located targets. Otherwise it re-starts the guider for each target regardless, as the filter may have changed.
Within a #REPEAT set (same filter, same exposure interval), if the total exposure time exceeds the max-unguided interval, the guider will be used. However, if it fails to start, and the individual exposure time is shorter than max-unguided, the images will still be acquired.
ACP observing plans can enable "dithering" during guiding (unguided dithering is also supported, by the way). The #DITHER directive can specify the maximum amount of dithering, in fractional pixels, that will be applied to each image. #DITHER without a value will result in +/- 5 main imager pixels max. The images are offset plus or minus a uniform random amount in X and Y of from 0 to the maximum. The X and Y offsets are independent random values.
ACP's German mount flip tracking will automatically flip the guider as needed, eliminating the need for recalibration after a meridian flip.
If you have an internal or off-axis guider and rotator, it will go through a series of steps after a GEM flip to make sure that the same guide star is being used successfully. Without a rotator, you will probably not be lucky enough to have a guide star on your internal/off-axis guider (due to the small field).
With this logic, assuming your guider has sufficient field of view and sensitivity, guiding will be virtually 100% reliable. When it fails the image will be acquired anyway, allowing ACP to work through passing clouds, and not upset the timing of your run.
If you manually calibrate MaxIm's guider and you have a German mount, you must calibrate it with the scope looking east of the meridian, and the Pier Flip option off. Also, you must set the declination of the point at which you calibrate. You must also manually determine the guide sensor angle (see