QHY5 camera Special Instructions

Install drivers, connect to QHY5L-ii two different ways

The drivers may change and these instructions may go out of date, so beware adjustments may be needed.

The QHY5L-ii and QHY5iii-174 are very sensitive video cameras that are well-suited to guiding and collimation with MetaGuide. Although they have small pixels, they are sensitive and have low read noise, making them good for guiding with a small guidescope or off-axis guider.

Example view of off-axis guiding with QHY on 8" SCT. Note the small (1.5") and well defined guidestar image.

Install Drivers

Go to the QHY download page and download the latest drivers for the camera. I used to recommend using broadcast mode, but with recent versions of MG since the 5.2.15 Beta, the frame rate is shown correctly and you can use the native driver without broadcast mode.

Connect MetaGuide to the Camera

There are different ways to use the QHY camera in MG, but currently I recommend using the Native WDM driver.

Guide with the Camera's ST4 Port

The QHY cameras have an st4 port that allows autoguiding with accurate timing and without an extra cable from the computer to the mount. MetaGuide can control the guide port directly without relying on ASCOM - but you may want to have an ASCOM connection to the mount anyway, to read information such as declination and autoguide rates that are useful for autoguiding and otherwise would need to be set manually.

To use the st4 port, first make sure the st4 output port on the camera is connected to the st4 input port on the mount with a proper cable. Start MetaGuide and go to the Setup page and select the dropdown for Guiding Method - and choose QHY. If you also want to connect to the mount using ASCOM, to read information such as declination, then click on the ASCOM chooser and select your mount. As usual, some mounts may not connect direclty to MG and you may need to connect MG to "Generic Hub" - and then connect "Generic Hub" to your mount. Then close Setup and re-open it. If you connected via ascom, the correct declination should be displayed, along with the current autoguide rates.

To test the st4 port, use the handcontrol or some other method to get a live display of the RA/Dec. values of the mount. Then open the Setup dialog in MG and try pressing the N/S/E/W buttons and watch for small changes in RA/Dec. Each press will cause a 1 second pulse guide in the corresponding direction. This motion will be very small so don't expect anything big - but you should be able to see some response indicating a good st4 connection. Dec. motion may not be responsive due to backlash, so RA may be best to use. You may also be able to have a helper listen closely to the mount to hear the 1s pulse commands, and in that case declination may be more easily noticed because the dec. motors are normally off - and would only turn on due to a pulseguide command.

Unfortunately the support for st4 may change with future qhy drivers - so if it doesn't seem to work, please use ascom drivers for autoguiding.


Make sure you actually have a display from the camera visible in MG, because even if the camera is not connected, MG will connect and give no error, but the screen will be gray or black. Make sure the camera is connected and the image shown in MG is changing when the view changes.

If there is a problem with either the display or the st4 connection, try following the general troubleshooting advice on the MetaGuide Troubleshooting page.


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


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.


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.