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Would an autoguider be a big benefit?


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Hi All,

I'm a newbie and am going to be picking up my first scope and mount this weekend. It's an EQ3 Pro and Startravel 102. When funds allow, I'll be adding an ASI178MC and mini pc running NINA for astrophotography. We're mainly interested in DSO. Would the addition of an autoguider scope & camera be a benefit or should the tracking of the EQ3 be good enough?



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Absolutely yes, in fact autoguiding is more common than not autoguiding. Not guiding will limit your usable exposure time to quite short ones, which will depend on how good your particular unit of EQ3 is but generally probably best to avoid exposures over 30s if you want to have most of the frames be usable. Since you are already gearing towards having proper PC control of the whole rig, you have done most of the job already.

The only things you do need to buy are a guide cam, guide scope and some cable to connect the mount to the PC. And get used to some software of course, but its not super difficult.

This is probably the most common camera for guiding: https://www.firstlightoptics.com/zwo-cameras/zwo-asi-120mm-mini-usb-20-mono-camera.html . I have one and honestly there isn't much to say. It does its job just fine.

For the guide scope you have lots to choose from and its up to you how much you want to spend on it. Spending extra is mostly a convenience thing, not something that gets you better performance (for the most part). A generic 50mm finderscope converted to a guidescope with an adapter will do the job just fine. I personally found the finderscope style rotating lens cell focuser annoying to use so i bought an actual guide scope, but this is not something that has to be done. 50mm finders are cheap and i would assume you can find a used one for sale every now and then.

For the cable, it depends. I think the newest model of EQ3 PRO might have a USB port on the handcontroller and/or main control box, but im not sure. My EQM35 has one and the mounts are quite similar in design. If thats the case, any USB2 printer style cable will bridge the PC to the mount just fine. Plugging the USB cable to the hand controller will let you use both the handcontroller and your PC to control the mount. This could be beneficial, but if youre going to only use a PC to control, then not that big of a bonus.

The other solution is to get a USB to serial cable that plugs in to the hand controller port of the control box, note that this means you cannot use the hand controller anymore at the same time. https://www.firstlightoptics.com/sky-watcher-mount-accessories/lynx-astro-ftdi-eqdir-usb-adapter-for-sky-watcher-eq5-pro-heq5-syntrek-pro-az-eq5-gt-az-eq6-gt-and-eq8-mounts.html

The second suggestion is probably the more common one, and many people find the USB to serial cable to be more reliable than the on-mount USB, but personally i prefer the first choice.

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These days if you are going to do imaging with a mount guiding goes hand in hand with that process.  The norm is to use a second scope, which can be a 9 x 50 finder or a dedicated guidescope, and a mono camera typically adding £220  example here, but this adds weight to the rig and the EQ3 pro is rated at 5Kg payload for imaging, and the ST102 comes in around the 3kg mark, so your choice of camera at around 130g means this combo would be well within the capacity of the mount.

If you intend to run the scope via software on a PC of some description then I would seriously consider ditching the handset and connecting the mount direct to the computer via a LYNX EQDIR cable - around £35.  You then use EQMOD or GSServer as the interface for ASCOM compliant applications such as NINA and an / or Astronomy planetarium applications to select the targets.  Having a direct connection makes things simple and saves having to have one more possible communication issue.  Having to place the handset into PCDIRECT mode, which makes the handset redundant, the handset effectively becomes the EQDIR cable !


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2 hours ago, dazzystar said:

Thanks guys for the replies.

It looks like I'll be going down the NINA route so will look for a mini-pc that can sit outside with the rig. I'll keep an eye out for a used camera and find / guide scope.

You seldom see finder guiders offered for sale in the SGL classifieds... so you could be waiting a long time !

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