Using The SkyWatcher EQ5 Pro

Sky Watcher EQ5 Pro German Equatorial Mount

How to set up

When initially setting up for an imaging session, there are four things to immediately do; level, balance, focus, polar align. If you don’t do these things well then your images will suffer for it. You won’t be able to expose for longer frames, which lets face it, is probably one of the primary reasons you bought the kit in the first place, your stars will start trailing, they’ll be out of focus, and you’ll also put more stress on the equipment. So let’s take each of those things in turn.

Levelling

Why do we need it to be level? No, it’s not because everything will look at a funny angle when you image it. It’s space, there’s no up, down, left or right. We level it because if we don’t then it inhibits the mount’s ability to keep itself aligned with celestial north, which in turn will affect your ability to take longer exposures. So we level it as near as perfect as we can. For this the mount has a spirit bubble fitted into it. It’s not the greatest in the world, but it does the job. If you want to be really pedantic about it, and this is purely down to personal preference, you can get an actual spirit level and place it across the top surface of the tripod prior to fitting the mount head to it, and check acoss two or three directions if it’s perfectly level. Because I’m not a huge fan of taking the equipment apart constantly, I go with the bubble level method. For me its quick and it’s accurate enough.

Balancing

There are two axis in which you need to be balanced; RA (or right ascension) and DEC (declination.) These are the two axis that an equatorial mount moves around, and if you’re not as well balanced as possible then, again, you won’t be able to take longer exposures without introducing trailing into your images. What you’ll also do is put more strain on the gears and run the risk of them becoming unusable sooner.

DEC balance – this is the axis the OTA (optical tube assembly, or telescope itself) sits along. You balance this by finding the centrepoint with all the equipment added (camera, reducer etc.) This is why a longer dovetail is more useful as you can slide the entire assembly along it and achieve better balance when you have more kit such as focal reducers etc.

RA balance – there’s a school of thought that suggests having things a little “east heavy.” I have to agree with this personally. The idea is that being a little bit heavier on the one side, the east, helps to keep the gears meshed together. The following excerpt from a discussion on the Cloudynights forum goes into some further detail on it – “the purpose of an intentional imbalance is to keep the worm gear riding on the worm at all times. If you balance “east heavy” that means that the scope will just slightly want to fall to the east on the RA axis. This constant gravitational pull to the east keeps the worm gear riding on the drive side of the worm, since the mount is driving from east to west. When guiding, if a guide pulse is sent west, the worm speeds up and the contact remains good. If a guide pulse is sent east, that simply means that the tracking rate slows down, but since the worm is still driving from east to west, contact still remains good.  At no point does gear backlash come into play since the worm gear is always making contact with the same side of the worm as it drives the mount against gravity.”

This works for being west heavy as well, although unless you dial in being west heavy first, then you’ll find yourself having to adjust the position of your counterweights slightly. Being west heavy can be useful, especially for instances where most of your imaging session is going to be done after the meridian flip.

Focusing

I would at least hope that this is pretty self explanatory. You can’t take an image of anything if you’re not in focus. There’s a couple of ways to achieve this and I’m going to go through the ones that I use.

First off, go to a bright star. You can use the “Live View” function on your DSLR. This applies if you’re using it with either one of it’s own lenses or it’s sat at the focuser end of the the OTA. Switch to Live View and then, using the Zoom control (NOT by zooming in by twisting the lens itself if you’re just using the DSLR and an associated lens) to get to x10 zoom. Then, either by using the focus ring on the lens to get to around infinity focus, or by using the focuser on the telescope, twist and turn until you have pinpoint stars.

Something that is absoutely essential in aiding focusing is using something called a Bahtinov Mask. This will get you to perfect focus. They come in all sizes and there will be one that’s suiable to your own setup, and are the easiest way to achieve pinpoint focus. Place the mask over the objective end (that’s the end that actually points at the sky) and then look at the image. What you should see is a large “X” with a line going through it with the star at the centre of the “X.” Adjust your focus until all lines intersect perfectly and are in alignment with one another. You now have pinpoint focus.

You can also use the focus tools within such software as APT, NINA, SharpCap etc both with and without a Bahtinov Mask. I use a motorised focus system with the mask and as such can control the focus from the laptop via APT. Just make sure you take the mask off once you’ve achieved focus. We’ve all done this, so don’t feel too bad if you forget to do it. At worst you’ll only lose a couple of frames if you do forget.

bhatinov mask, ed72, skywatcher
Focusing with a Bhatinov mask in SharpCap

I also run my focus routine at the same time that I do my polar alignment, which I cover in the next section. Be aware that you’ll likely lose some light transmission with a mask on, so adjust your exposure times accordingly. The great thing about using a Bahtinov Mask is that it literally takes a few seconds to slip it on and it’s a good idea to check your focus hasn’t shifted throughout an imaging session, although some systems can allow you to keep focus automatically as it can be affected by temperature changes. APT for example has had its auto focus routine updated, although I have yet to use this myself. It looks very promising though.

Polar Alignment

If you’re platesolving and guiding, you may well ask yourself why bother with polar alignment. Why not just let the software get on with doing its thing? Truth be told, you still want your mount aligned with celestial north otherwise you’re going to run into problems when it comes to imaging. Even with solving and guiding, a poor alignment will result in field rotation and poor imaging results.

Because I already cover polar alignment in my Guiding Walkthrough I won’t go into any detail here. Just suffice to say that it’s hugely important for successful imaging, so please don’t skip out on it. Take your time and do it right.

Imaging

72ED sat on my EQ5 Pro

For its age the EQ5 Pro is still an excellent bit of kit. Granted it has a low (comparatively speaking) weight capacity, but I’ve also seen people load it with a 200 P-DS and obtain good results. I can’t recommend that as it’s well above its maximum rated capabilities, but I’ve seen it done, so the final decision there is obviously up to you.

With a pointing accuracy of up to one arc minute, and a resolution of 0.288 arc seconds, it’s going to get you on target, and keep you on target with a high degree of accuracy, especially when using shorter focal lengths. Subs of 10 minutes can be achieved at 420mm, with a high keep rate, although I personally tend to go with half of that and keep to 5 minute subs. I have an intermittent issue where my ASI178MC will throw out subs that have some sort of electronic interference pattern, which means that those ones get thrown out. So in order to keep as many as possible, I stay at 5 minutes.

With my setup I ditched the handset early on and opted for PC control of the mount via the SynScan app for Windows and APT. This works via ASCOM, and I have to admit is a dream to use. You can control all aspects of your imaging session via this, including slewing to target, meridian flip, focusing, imaging plans etc. You need an additional cable for this, an EQDIR one, which plugs directly into the handset port of the SynScan controller box. Just note that you need the SynScan Windows app open to be able to use it via APT. It also works with PHD2, although again you need SynScan already open for it to be able to connect.

The beauty of it is that you don’t need to do a star alignment and you can go straight into your session once you’ve sorted out your polar alignment.

Although SynScan comes with its own database of objects, I’ve found that it’s not that accurate when slewing to your target, and this is the main reason I prefer to use the platesolving technique within APT. Of course it may well be something that I’m doing wrong myself that causes this, but platesolving gets me where I need to go, and with the ASTAP integration in APT, I find that it solves images within seconds.

This is only a brief overview of the EQ5 Pro, but I find it to be a very capable and underrated mount and, if well looked after, will serve anyone well for many years.

All that remains is to thank you for taking the time to read, and for now, clear skies all.

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