Pegasus Focuscube(s) Review
July-November 2018
Background.
My current setup comprises a Celestron C11 Nexstar GPS (c 2003, deforked) and an Opticstar Acsension 127mm Apo (Explore Scientific clone), side-by-side mounted on an EQ8 in my Pulsar 2.1m dome.
Until recently, focussing was done manually on the Apo and by a JMI Motofocus on the C11. But now, with the fact that I have 3 cameras (ASI 1600MM-Cool, ASI 290 Mono and ASI 224 Colour), an OAGand ZWO Mini EFW for use with the ASI1600 and ASI294,and a Quark and want to use all three on both scopes - with the C11 @ f/10 and f/6.3, finding/remembering all the focus points was getting to be a chore – not too much on the Apo – just a method of remembering how many extension tubes and checking the mm scale on the focusser, but for the C11 – with the JMI – it meant remembering whether I had it set for fast or slow and then counting the seconds between the focus points – written down on a sheet of paper! And of course remembering where I had left it after the previous observing session.
For me the benefits of a Motorised Focuser
· high precision control
· the telescope is not touched – no waiting for vibrations to settle
· focus remotely using PC
· use autofocus or focus aid features of your chosen imaging software – usually Sharpcap for me
· compensate for changes in temperature
There is really only one drawback in the upgrade, and that’s added hardware and wiring to the kit - another USB connection to your PC, and more wires running to the telescope and mount. I would think that those of you that have a personal observatory with a permanent setup are more likely to invest in an automated focus solution.
Astrophotography enthusiasts looking to automate their focusing procedure have a few options. You can either purchase an entirely new focuser kit that includes a motor (such as a MoonLite Focuser) or upgrade your telescope’s existing focuser with a stepper motor like the one available from Pegasus Astro – either the DMFC or Focuscube. Other brands are available
Here, I discuss the Focuscube – this seems to be a development of the DMFC in that everything is housed in a single box attacked to the scope, rather than separate stepper motor and control box.
What’s in the Box?
There are different variants of the Focuscube for refractors (‘universal bracket) or for SCT’s – specifically Celestron 6, 8, 9.25, 11, or Meade.
Pegasus keep a list of compatible scopes on their website.
What is in the box?
· 1 x FocusCube
· 1 x DC Cable to Cigarette Lighter (3A fused)
· 1 x USB2 Cable Type B
· 1 x Temperature Sensor
· 1 x Blue Anodized Bracket (Universal L shaped or SCT model) • Different sizes of bolts and spacers
· A single page install guide
Refractor SCT
Installing the Cube
Full instructions can be found on the Pegasus website. Below is my personal experience performing the installation of both types, in situ in my observatory. Note that there were a few issues – all down to me, not the Focuscube – see my notes below.
Basically:-
For refractors
i) Remove the existing focuser knob
ii) Remove a couple of the screws/bolts holding the focuser back plate
iii) Attach the Focuscube to the spindle using the supplied flexible connector and Allen key – can be a bit fiddly
iv) Attach the Focuscube to the focuser body either using the screws/bolts removed in ii) above – or use the supplied bolts – these are slightly longer to take account of the thickness of the Focuscube bracket.
v) Plug in the cables
For SCT
i) Remove the existing focuser knob
ii) Remove the three screws/bolts holding the focuser back plate
iii) Attach the Focuscube to the focuser back-plate using the original screws/bolts – only loosely at this stage
iv) Attach the pulley wheel to the focuser spindle using the Allen key – can be a bit fiddly
v) Loop the belt over the pulley and the wheel on the Focuscube.
vi) Adjust Focuscube position for tightness and fully tighten the bolts – there should only be a little – if any slack
vii) Plug in the cables
Notes:
The team at Pegasus Astro were amazingly quick to respond to the early questions I had about installing the Focuscube and some issues that I encountered that were entirely my fault – primarily because:-
i) Check that your scope is compatible with the Focuscube. Pegasus have a list of scopes that have been fitted with the Focuscube, and they are extremely responsive to any questions either via email or their live chat. I didn’t check that the focuser on my Apo was compatible with the Focuscube. In my case, the bolt(s) to attach the bracket to the focuser needed to be 10mm, but the Cube’s bracket would only allow 7mm bolts through it. It was necessary to make a slight modification to the bracket – i.e. bend the bracket!
ii) I have what may be described as a ‘vintage’ C11 – It’s a Nextsar GPS model that’s been deforked. It turned out that this model, and only this model, has a different spindle size from all the other models. The pulley supplied for a C11 by Pegasus is designed to fit a 21.8mm focuser spindle. The spindle on the Nexstar C11 is 22.8mm! A quick online chat to the guys at Pegasus, some simple measurements and some further research on the JMI website (http://www.jimsmobile.com/buy_motofocus.htm#Celestron - it had details of the spindle sizes! – noted here for future reference) confirmed the problem and Pegasus manufactured a new pulley and shipped it direct from Greece to the UK within 7 days
iii) When fitting,
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for the refractor, it’s OK to fit the Focuscube with the drawtube racked fully in or fully out – in my case there’s only about 45mm of travel and it doesn’t take too long using the Focuscube to rack fully in or out to set the zero point and the max point
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For the SCT I would recommend fitting it while the scope is at or near its usual – most often used – focus point. The reason being is that there is far more focus travel and the Focuscube speed is further reduced by the pulley ratio, so that it can take an age to rack all the way in and out. My final solution was to fit it, rack it in to the focus point of the ‘nearest focus’ setup I have, then rack in a it more (about 100000 steps using their software and se tthe zero point. Then I rack out to the furthest focus point used my be setups, added about another 100000 steps and set the max point – the zero and max can be rest later if new equipment doesn’t fall within the existing range.
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The Software
The Pegasus stand-alone software for the focus motor controller worked like a charm. I simply leave this application running during my imaging session to control the focus
You’ll find the necessary software to run the camera on your PC here: http://pegasusastro.com/support/
The stand-alone software that comes included with the Motor Controller works exceptionally well and is very straightforward.
The (Optional) Hand Controller
Since the installation back on August 2018, Pegasus announced an optional hand controller for the unit. Although the control software is easy to use it can be a bit tiresome when trying to achieve best focus – clicking mouse buttons doesn’t give the easiest of fine control. So I have upgraded to use the hand controller also. I use the software to go to my noted focus position (depending on the kit in use) and then use the hand controller in conjunction either with Sharpcap or just by eye to achieve best focus. It is good to know that both can be connected to the focuser at the same time and the software reflects the positional changes made by the hand controller
Final Thoughts
The Pegasus Astro Focuscube is an affordable and effective way to upgrade your existing telescope(s). This installation process was straightforward on my telescopes, but owners of other telescope types and sizes will need to research the Pegasus Astro website to make sure a motor focus kit is a good option.
The supplied software works well, but the Focuscube can also be used via Ascom drivers and so can be used from inside software such as Sharpcap