iOptron Skyguider Pro Portable Rig

Everyone needs a lightweight rig; small enough to take away for a weekend to a dark sky site whilst not compromising on capability. This can also double as a quick home set-up if you’re not blessed with long periods of clear skies. You can have it primed to capture those 2 fleeting hours of starlight and still catch your favourite TV programme. This blog takes you through the steps I took to get to my perfect lightweight rig.

The Scope

My lightest, widest and cutest scope is my William Optics WhiteCat. This is the white version of the RedCat (also now available in grey as the SpaceCat). I got the white as it is the same white and gold livery as my 72mm Megrez.

The scope is 250mm focal length at f/4.9, so pretty fast and gives a nice wide view, perfect for large nebulae and wide clusters. It has a slightly usual focuser (more like a zoom camera lens) and is light at c. 1.5kg.

The front of the tube unscrews and once rotated becomes a dew shield. It screws back onto the body, revealing the focus grip. The cap has a built in Bahtinov mask for focusing. It packs away into a padded bag.

The Image Train

Onto the back of the WhiteCat’s M48 thread I mount:

1. ZWO Off Axis Guider M48-M42, with ZWO non-rotating helical focuser and ASI120MM mini guide camera. Thickness 16.5mm

2. Spacers: 11mm T2-T2 (comes with the main camera) + 5mm T2 spacer

3. Altair Astro T2-T2 filter drawer with removable filter tray (2” or 1.25”). Thickness 17mm

4. ASI294MC Pro cooled colour CMOS astronomy camera (whose sensor is 6.5mm into the body)

This gets me to 56mm back focus - near enough to the 55mm optimum spacing for my camera. I place the OAG first so the light path is not affected by the filter, and the spacer gives me the ability to slide the filer tray in and out - otherwise it would clash with the guide camera focuser.

I had previously run the main camera without the OAG but with a small 30mm ZWO Guidescope mounted onto the tube ring. This worked fine but does change the balance slightly. Having experimented with the OAG I liked the compact nature of the setup and have kept it this way. The OAG does not come with the red helical focuser, and is a MUST - it is the smoothest and simplest way to achieve focus on the your guide camera and takes the pain out of using off axis guiding. It is in my opinion, also easier than focusing the guide scope.

Aiming at the target

WO provide an accessory to fix a shoe onto the top plate of the tube ring. This fits the ZWO guidescope or newer Red Dot Finders. Unfortunately I had an older version WO Red Dot Finder with a different shoe, so I had to spend £10 on eBay for a shoe change in order to mount this.

As you are not looking for tiny objects with a 250mm focal length, pointing in the right direction only has to be fairly accurate. I prefer the ‘stand back and align’ approach of the RDF rather than finder scopes, and find it far more comfortable. I tend to only use the RDF for a few minutes, then once I’m in the right ball park, I switch it off to save battery. It is very light and stays in place during imaging.

The Tripod

For most of the year I have been using my heavy duty camera tripod made by Slik. The has an adjustable head and it is pretty rigid. However there was tiny bit of play in the head which I wanted to get rid of.

Over Christmas I bought the iOptron 1.5” tripod made specifically for the Skyguider Pro (and a few other smaller mounts in the range).

The tripod has a simply flat plate top with a threaded bolt that come up into the base of the iOptron Skyguider Pro. It has an accessory tray and is nice and solid.

The Mount - iOptron Skyguider Pro

Onto the tripod sits the mount; the iOptron Skyguider Pro. This is a simple tracking mount with a polar alignment scope built in and motors that control RA only (there is no DEC motor). It is chunky and well made but very portable. It has a built in lithium battery charged by usb. You can forsake the visual polar scope for the iPolar to help your alignment, but this requires a laptop and to me defeats to object of travelling light.

The mount can easily support the weight of a camera and lens, and also small scopes with the use of the counterweight bar and counterweight. As the name suggest, it has a port for attaching a guide camera (which makes it superior to the cheaper Skytracker). It has various speed controls, the most useful being 1x speed - or sidereal - to track the apparent movement of the night sky.

The standard wedge is pictured on its own. This is a black metal body with plastic threaded bolts. It has a bubble level for getting set up, an altitude scale, a Vixen-ish bracket to take the main Skyguider Pro body and adjustable screws for alt/az polar adjustment. A threaded hole on the base take the bolt from the tripod (or a standard photographic tripod).

In use it’s OK….but many people including myself have found it difficult to achieve good polar alignment as the actions are too jerky. It’s a solid 6/10 but no more.

Upgrade 1 - The Wedge

Recognising the limitations of the standard wedge, WO sell an upgrade kit for the Skyguider Pro which includes a wedge and counterweight extension bar, to allow you to balance a slightly heavier scope rig with the single 5kg counterweight.

Everyone raves about the wedge - and rightly so. As smooth as silk is the best description for this. It feels so much more solid and engineered compared to the standard wedge. The threaded bolts are all metal and the smooth action makes Polaris easy to align in the polar scope, saving you precious time out in the cold. At close to £200 it is an investment, but a good one.

Upgrade 2 - Dec Adapter

The second highly recommended upgrade is the WO Dec adapter/ puck which is the circular red all-metal connector that sits on top of the counterweight bar.

The standard black puck is held on by two plastic tipped threaded bolts. You loosen these to rotate the camera/ scope about the Dec axis (remember it only has an RA motor). Unfortunately, if you loosen too far the whole assembly can fall from the mount which would be catastrophic. As well as making the rotation smoother, the WO Dec puck cannot fall off even when loose due to a series of tiny threaded grub screws that keep the puck inside a groove.

The Dec puck is sold as one piece, alongside a second piece which the the red WO vixen plate. Again, this is an all-metal upgrade to the slightly simple vixen bracket that comes as standard. The Dec puck is an ESSENTIAL upgrade to avoid a serious design flaw in the standard puck, and not too expensive at c.£25. The vixen clamp is a further £50 or they come together at the same combined price. I bought both and noticed the difference immediately - no more risk of everything falling off, smoother rotation and better engineered components.

Upgrade 3 - Avalon X Guider

During 2020 I was happily using my Skyguider Pro with both the WO wedge upgrade and the Dec adapter/ vixen plate. These two changes had a marked improvement over the standard kit. I then saw an opportunity for a further improvement; a chance to purchase a secondhand Avalon Instruments X Guider.

The problem I was having was with fine adjustment for framing. Imaging large targets mean they often nearly fill the frame. Getting them centred was tricky. I would first loosen the RA gears, loosen the Dec adapter and manually point the scope at my target (or nearest bright star) using the red dot finder. From there I would tweak the RA using the forwards/ backwards buttons on the mount and manually adjust the Dec with tiny rotations until I had my target in frame. A final rotation of the camera could also be used.

I found this hard. Up a bit, down a bit, left a bit…it took me forever to get my framing correct. What I lacked was fine adjustment - a method that helped me enormously on planetary imaging (see Journey to Mars). I read up about the Avalon X Guider - designed for fine adjustment of a guide scope but with the capacity to carry my small scope and camera. It also claimed to be very light and rock-solid with no movement. They cost c.£300 new and I bought the secondhand version knowing that should it not be right, it would hold its value for re-selling.

The X Guider has a red body (that just happens to match the rest) with a plastic grey vixen bracket on top. Tiny bolts allow for the adjustment up/down and left/right and it is solid. The tricky part was mounting it to the Dec adapter as of course the holes didn’t align. I had to mount it forwards on the Dec puck (on the centreline) using two screws; one up through the Dec adapter and one down from the X Guider.

Now I can use the RA motor and Dec adapter to get close, and use the X Guider to get EXACTLY where I want to be, and it’s lovely. It was an expensive indulgence and definitely NOT essential, but has helped me save time and avoid frustration. I sold the WO vixen plate on eBay.

Modification to Bolts

With all these new pieces in place I made one further change. To my mind, the weakest part of the system now was the plastic headed bolt that secured the counterweight bar (and everything attached onto it) onto the RA gear on the Skyguider Pro. This is identified in green on the image.

There was no danger of it coming off, but I liked to have it tight, just in case. Once tight however, it didn’t like to be loosened again and the shallow grooves in the plastic head gave little grip. I had to resort once to pliers, which left their mark and was no way to carry on in the future.

I discovered that all the threaded bolts were the same on the counterweight and the wedge. The counterweight bolt needed to be long and slim to not foul the RA clutch plate. I removed the far-side (northern) stainless steel bolt from the altitude adjustment on the WO wedge and replaced it with a larger black plastic knob I had in my ‘box of bits’.

Using the WO stainless steel bolt I replaced this for the plastic one on the counterweight bar giving me far much reassurance when tightening and loosening this connection. The change to the alt control has no noticeable difference in the performance of the wedge.

The Brains

With the rig now complete, I needed a portable system for image capture - which is of course the ASIair (or the new metal bodied Pro version). This is the brains behind the camera, controlled by smartphone app. This device can also run a polar alignment sequence if you want your PA super-tight. It also has the skills to control a filter wheel or autofocuser (I use neither).

I run an ASIair Pro connected to the ASI294MC Pro using USB3 and to the ASI120MM mini using USB2. The mini also connects to the Skyguider guide port. The ASIair is powered by a Celestron Lithium 7.2Ah Powertank. The AISair daisy chains the power onto the ASI294MC pro to power the cooling fan via one of the four 12v power outputs.

From the USB output on the ASI294 I power a dew heater strip for the scope. That’s one power supply for everything. The Powertanks straps onto the tripod leg and the ASIair sits happily in the accessory tray of the tripod. I use the ASIair to focus on a bright star. Then having pointed the scope roughly at the target I use plate solving to locate my target, tweak my framing with the X Guider and run my capture sequence.

Tips in Use

The main tip I can pass on for using this type of rig is to not pick objects too near the zenith if you’re not prepared to spend a lot of time on your hands and knees. Framing a high target, even with all these upgrades, on a non-GoTo mount can be time-consuming and uncomfortable. I have learned that I am up and imaging far quicker if the object is 2/3rds up the sky as its just so much easier to find. Also test the height of your polar scope relative to your kneeling position, so you can find a comfortable height to set your tripod.

The Full Rig

Example Images with this rig