First light SGP with MetaGuide dithering - Edge11 tadpoles


I have been working with a lot of new equipment at the same time I am learning SGP, but equipment and weather generally cooperated last night. Unfortunately I am having trouble with my focuser, so I was only able to focus at the start of the imaging - and I just left it at that setting for the 3 hours of this image.

This is a view of the IC410 tadpoles with Edge11 on cge-pro at f/10, with Atik 383L+ (8300) ccd and 3nm Ha. 12x15m exposures calibrated and stacked in my own code - then only levels applied in Photoshop - no other processing or cropping. Original scale was 0.4" per pixel - reduced here to 1.6". Original fwhm was in the low 2’s arc-sec.

This test confirmed that everything in SGP works fine with MetaGuide using the MG dithering provided by SGP. SGP does not control the amount of dithering - you have to do that by specifying it in arc-seconds in MG. Also, SGP does not monitor the guide error to tell when the guiding has settled after dithering. But if you just enter a delay between frames in SGP, the delay will happen just after the dither command - which is ideal. So the exposure ends, the image is downloaded, the dither happens - and then the delay. Just enable MG dithering in SGP and set an inter-frame delay (in this case 10 seconds) - and it all works.

I am guiding with OAG and the dither radius is 15" - so it recovers quickly from the dither move. There is no need to stop guiding or anything - dithering just happens and the star is quickly pulled back in.

I am hoping to do more automated sessions with focusing and meridian flip - but everything worked ok here for this fairly new user to SGP with a new OTA.


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Looks good Frank! We can definitely offer tighter integration with MG (especially in terms of waiting to settle)


Nice first light.

I always wanted to try MG, but I never managed to have all the pieces in place, but now I have everything needed.

Does MG compensates for DEC changes and meridian flips?




Yes - MG has been around for many years and it has always compensated for dec. changes. It has also handled meridian flips in a semi-automatic way where you tell it when the meridian flips and it automatically changes the guider calibration. Recently I added code so it does this automatically with an ascom connection - but it does not require an ascom connection for guiding or collimation.

My goal has been to allow automated imaging with both OAG and guidescope guiding - while handling meridian flips. I haven’t been able to test it much in SGP, but I believe everything is there to allow SGP to do an automatic meridian flip and for MG to continue guiding - but you need to insert scripts to run when you change objects to tell MG to stop guiding, then start guiding again.

The main focus of MG has always been tight guiding rather than ease of use, and it uses video to decrease latency and reduce the impact of seeing for collimation and guiding. As a result the user interface is very busy - but it is full of information and video provides a live view of the star that helps provide a realtime sense of the whole guiding/calibration process.


Excellent Frank!

The reason I never tried MG was the lack of video capabilities of my lodestar, but now I have a QHY5L2 that works flawlessly for guiding and it has video capabilities.




Yes - I have been promoting the qhy5l-ii for video guiding ever since it came out - and the image I posted was guided with that camera in OAG mode with about a mag 8.5 star at 10 fps. The combination of video with OAG works well because it is easier to find stars with interactive video - especially when using a rotator - and the centroiding in MG is able to study the star spot as distorted by seeing and guide on the central hot spot rather than the overall centroid.

Special instructions for using MG with the qhy5l-ii are on the main metaguide web page. I recommend using it in combination with ezplanetary.

From sgp’s perspective it is unaware of the guiding that is happening, and you can have MG visible in a separate window showing the star and the live guide plots. All sgp does is send a dither command between exposures - and when that happens you see the guidestar jump briefly, then return to the target in a short time.


This is so bloody exciting. I have been wanting to move away from PHD and use Metaguide for quite some time now … finally!

As soon as I have clear weather, I’m going to go ahead and test this out. I’ll be sure to post up my results as soon as this horrible weather passes

Thanks for all of your work, Frank and of course SGP team.


Thanks - I have been imaging a lot with SGP and MG lately and it all works pretty well. Lately my focus has been on imaging the comet - and for that I don’t use dithering but I do use shift-guiding, which allows long exposures while guiding on a star. I think MG is the only guide software that can do this, and it allows me to do high res, long exposure imaging of the central coma. I’ll be posting some of the recent results soon.

As with a lot of what MG does - SGP doesn’t know about it and doesn’t need to know. The two systems are fairly independent and that has advantages.

I haven’t been able to do much automation because I don’t like the way plate solves and syncs happen with a celestron mount, presumably due to J2000 vs. JNow being sent to the mount in a sync. So I haven’t done unattended meridian flips and things like that - but it should work.