Out with the old, in with the new!

Well, this has been a long time coming I suppose. Those of you who read my blog regularly will understand the strife that I have had with my Sky-Watcher EQ5 Pro mount over the past 12 months. When I was looking around for equipment last year, the best advice that someone gave me when starting out, is “buy the best mount that you can afford”. I followed this ethic at the time by purchasing the EQ5 Pro. In hindsight, I wish I could have stretched my budget a little further and got the HEQ5 straight out the gate.

For the first couple of months it was working well. When using an intervalometer with my DSLR, I was limited to a maximum of 90-seconds, due to my polar alignment and the inherent accuracy of the mount itself. However the true limitations of the mount became clear when I first bought a guidescope back in October last year. You can read about that here.

To quickly summarise all my issues with one word…BACKLASH. It was causing all sorts of havoc with my image capturing. Dithers weren’t recovering fast enough before the next exposure started, even with a two-minute settle time. This overshoot, mainly in the declination axis, lead me to discard upto 50% of my images. Some might say that throwing out half of my images is quite acceptable with a beginner mount like the EQ5, however to me, it’s just wasted time. I wanted to make the most of the limited time that I can capture between the indecisive British weather, and with the EQ5 Pro, it was nigh on impossible. Therefore I’ve recently made two upgrades that should allow me to really capitalise on every single exposure taken.

Technically speaking, I’ve only made one purchase. I’ve been very fortunate in being able to help out a few people who are also starting out in astrophotography. I’ve recently been helping out a fellow member of the Wolverhampton Astronomical Society, who’s recently caught the astrophotography-bug. He’s got an absolutely amazing setup for such a beginner, and of course I’ve persuaded him to use Nighttime Imaging ‘N’ Astronomy to control his whole rig! Another one converted to the dark side!

Celestron AVX + StarSense Align/QHY Polemaster/Canon 90D + 300mm + 2x Extender + 1.4x Extender/60mm Guidescope + ZWO ASI 120MM-S

In exchange for me helping him make the most of his equipment, he’s VERY graciously gifted me the larger 60mm version of my SVBONY guidescope. You know who you are, so if you read this, I can’t thank you enough! The new scope increases my focal length to 240mm; an increase of 50mm. This should help detect and correct for any star movement that occurs.

The next upgrade is the most significant to date, allowing me improve my astrophotography no-end going forward. For a long time I’ve been eyeing up a Sky-Watcher EQ6-R, as that seems to be the most common mount that people use for astrophotography. However, since the beginning of the COVID lockdown I’ve noticed the price slowly creeping up due to demand, to the point where it was out of reach. The other option was the iOptron CEM40, but on speaking to other iOptron customers the quality control has seemingly relaxed during the pandemic, as they try to cover demand. Also, it would be a whole new ecosystem to get to grips with. When I enquired on stock level of the EQ6-R, just like every other piece of astronomy equipment, it was on back order by pretty much every retailer in the UK. So, I turned to the second hand market.

Recently, I’ve joined a couple of astro buy & sell groups on Facebook, and noticed an influx of mounts in the past couple of weeks; ranging from an EQ5 Pro like mine to an AZ-EQ6-GT. The latter certainly peaked my interest, in that it’s equivalent to the EQ6-R Pro, but with a few added extras including freedom-find encoders on both axis’s. This mount is very variable in its use, as it’s really two mounts in one – an alt/az mount for visual astronomers, where two telescopes can be mounted either end of the head, and a standard equatorial mount that’s identical internally to the EQ6-R.

In the end, I couldn’t resist it and last weekend drove all the way to Devon to go collect it, resulting in 8 hours total driving in a single day!

Sky-Watcher AZ-EQ6-GT mount with my 130PDS scope mounted. Sky-Watcher EQ5 Pro next to it for size reference.

This mount is a SIGNIFICANT upgrade over my EQ5; everything’s more substantial and robust. Just by looking at the tripod itself, you can see the thickness of the legs and the size of the mount head in comparison. As the whole system is lower to the ground it has a lower centre of gravity, increasing stability and the capability of withstanding high winds that I often get howling down my street. However, the greatest upgrade that has been made is the altitude adjustment for polar aligning. Gone are the two thumb screws that work in tandem. In its place, comes a single rotating bolt on a pivot point that slides up and down. This makes polar alignment simple and almost effortless!

Sky-Watcher AZ-EQ6-GT Altitude Adjustment

When finished and properly aligned, the pin then slides down inside the large bolt, reducing the risk of any cable snags when the telescope is slewing around the night sky.

As you can see from the photograph above of my new setup, the weather was crystal clear that night I bought it home, and I honestly couldn’t wait to test it out! So I got it all setup with my Intel NUC PC and sorted my cable management with some expandable cable sleeving, as suggested by Glenn on astrobloke.co.uk. At least my cables won’t snag on anything now when it’s slewing around.

Straight away without changing any settings, the new mount was detected in EQMOD and some new features were unlocked in the process; the illuminated polar scope is incredibly useful and permanent periodic error correction (PPEC) will help improve tracking.

As I mentioned before, polar alignment is a breeze with the single adjustment bolt and I was aligned with an accuracy of 1.2 Arc-Minutes error within 2 minutes or so. Once I had connected to the PC on my iPad, I initially opened Stellarium and used it to find a star that was close to the southern meridian and around 30º above the horizon. Around this location, +/- 5º or so, is the best place for PHD2 to calibrate on due to the seemingly fastest angular rotation of the night sky.

The initial slew though went completely wrong, and the scope ended up pointing at the floor. My heart was in my mouth at this point! “Oh no, I’ve bought a dud!” I quickly stopped the slew and re-parked the mount within EQMOD and it turned out there was a massive offset in the declination axis.

Instinctively, I manually released the clutches and re-aligned the mount to the home position using the setting circles on the mount. Then within EQMOD, I found the ‘Re-Sync Encoders’ button, which reset the encoders to the home position. Releasing the clutches again and manually moving the mount instantly changed the mount coordinates within EQMOD, which was exciting to see it working in person. I re-parked the mount again and correctly parked in the right position this time around. Few, crisis averted!

The second attempt to slew to the chosen star was successful and plate solving within NINA worked flawlessly as always. After that I was soon into PHD2 guiding and running an initial calibration. Straight away I could tell there was a difference between the two mounts. The mount instantly changed direction when going from North to South, and it ended the 12 step process very nearly bang on 0px movement from the initial starting point. Just to confirm my suspicions I ran the guiding assistant with the backlash test.

I was utterly shocked by the result!

PHD2 Backlash Graph

That’s 1000x better than the EQ5, as it would continue to travel north when it should be going south! This new mount is ALMOST perfect with 0ms backlash; I could try and reduce that even further by adjusting the worm mesh, but I’m perfectly happy with this result and I don’t want to risk making it worse.

My guiding results spoke for themselves, with it being on average below 0.6″ Arc-Seconds. It looks quite spiky in the image below, but notice the Y-axis range – +/-2″!

PHD2 Guiding Result

To just test everything, I decided to choose a relatively bright target that fills the majority of the frame. Messier 13 – The Great Hercules Cluster – is always a stunning target, regardless of scope or lens. I will always have a fondness for this target, as it was first light through my Sky-Watcher 130PDS.

56 Minutes – Messier 13 – The Great Hercules Cluster

Unfortunately though, I was battling a 92% moon in the southern direction that night which completely washed out the entire night sky. This forced me reduce both my exposure and my ISO settings to 120-second exposures at ISO400. These settings allowed me to capture reasonable detail in the outer edge of the cluster, while not blowing out any stars in the core.

120-Second Exposure – Messier 13

I was only able to capture 1-hour before the clouds rolled in. I had to dispose of the last two exposures due to those clouds and not the mounts’ tracking inaccuracies for a change!

For an initial test, I’m really impressed with this new mount, and I’m confident that I can really push it to 10-minute exposures without it breaking a sweat. Everything is solidly built, and works superbly.

However, are the destined clouds compounded if I bought second hand astronomy gear? So you get the clouds from the initial purchase, and then clouds again from the second purchase…well it seems to be holding true for the next week at least!

So from now on, you won’t read about me complaining about a temperamental mount and how many subs I had to throw out. I was also able to increase my dither amount to 5-pixels and reduce the minimum dither settle time to 15 seconds, instead of 120-seconds. That should help reduce any noise in my final images, plus it’s a huge amount of time saved between exposures in any case; just over 1 minute. That allows me to get in an extra 2 exposures an hour!

I’m really looking forward to using this mount from now on. I just need to get rid of these pesky clouds that also came back from Devon with it. So if it’s cloudy where you are, I do apologise for the horrible weather in the coming days. Hopefully you will have better look than myself!

Till next time, wherever you are, clear skies!

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