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A Homemade Electric Focuser for my Edge11 HD

Details: Published: 27 February 2026

I have owned my Edge HD for about 4 years now and in the main, I have been very pleased with it. There are two problems with it:

It's very heavy.
It can be a pain to focus - especially when imaging.

I can do much about item 1. but I have been looking at options to help me improve the focussing of the telescope.

There are two problems with focusing, the first is that just touching the focus knob will set the telescope wobbling on my EQ-6 mount. Upgrading to a more rigid mount is a nice thought but financially not really viable at the moment. I really need to be able to focus it without touching the telescope. The second problem is trying to establish exactly where the telescope focus actually is in relation to the number of turns on the focuser. The focuser is essentially a brass linking tube that connects to a screw that moves the primary mirror up or down. There is no method of identifying where the mirror is and even which direction it needs to be moved or by how much to achieve focus. This is very frustrating when trying to focus the telescope when using long exposures on a camera.

Last year (2025), the BAA Journal had a short article on modifying a C11 to add a low cost turns counter (properly called a rotary encoder). This set the grey matter churning and after a few months, a similar rotary encoder was purchased (via eBay) from a retailer in China. I already had a very old (about 20 years old) electric focuser that I had used on my SkyWatcher 200 reflector which became redundant when I upgraded the focuser to a Crayford style dual speed unit. (A huge improvement).

SkyWatcher Electric Focuser

All I needed to do was to marry the two components with the Edge11 focusing screw coupling tube. Reasonable metalmaking workshop tools are required, specifically files, a set of drill bits (22mm and 26mm are the larger ones required), a pillar drill and a friend with a lathe or a contact at a local model engineering society. You will need a 3D printer or enlist one of the online companies to do the printing for you.

This is what I ended up with:

The top and bottom plates are 3mm aluminium sheet, the spacer between in 21mm deep, 3d printed.

The two gears are a (6mm) 30 tooth on the motor gearbox and a 60 tooth on the focusing coupling tube. A short length of brass rod (17mm diameter) fits perfectly within the focus screw coupler. This is turned town (using a lathe) to 14mm diameter to connect to the rotary encoder which is located on the top plate and above the coupler. A 252 6mm toothed belt links the two pulleys, the belt is not shown on the drawing. The only modification to the telescope is a M3.5 hole drilled through the coupling tube to lock the brass rod and the 60 tooth gear that drives the counter.

The 60 tooth gear had the shaft hole opened out to 22mm and this sits over the coupling tube.

This shows the bottom view with the the bottom cover set transparent. The gears are represented but no belt is visible

The engineering (CAD) drawing here shows the critical measurements:

The bottom plate uses the 3 existing screws that locate the orange disc surrounding the focuser.

The top view diagram has most of the repetitive dimensions omitted.

This photo shows the basic layout with the top plate omitted. At this point, I was checking the belt tension.

The distance between the motor and focus shaft centre is nominally 81mm for a 252 tooth belt, but my belt was a little on the tight side. If I did this again, I would find a way of making the belt tension adjustable. Possibly by using the motor mount plate that came with the original focuser kit.

This is what it looks like completed and fitted. Stainless steel 30mm countersunk screws with M3 Nyloc nuts hold it together. The 3 screws surrounding the counter are inserted from the underside as they are inaccessible when the base plate is screwed down.

The paintwork is about 8 coats of red spray enamel (from Halfords).

In Use

Fortuitously, especially during probably the wettest February on record, we had a clear afternoon and evening following final assembly.

I set up mid afternoon and with the moon at almost first quarter I calibrated the counter for 3 of my lenses and my ASI585MC Pro camera. It was an actual dream to use. Focusing was very smooth if a little slow, one revolution of the focusing knob takes about 25 seconds at high speed(!). However, now that I have noted the relative focus positions of my camera and lenses, getting very close to focus next time should be an absolute doddle. And all at a fractional cost of a commercial item.

Muon Daily Count and Trend Line

Details: Published: 23 February 2026

At the time of writing (20260223), I have been collecting Muon Count data for almost 3 years. My Cosmic Watch Muon detector is now officially a toddler!

The daily count is impacted by the solar wind, quite simply an increase in solar wind will cause a decrease in the daily count as the Cosmic particles are swept away. As we are now 16 months past Solar maximum, I decided to have a look and see whether this effect can be observed.

The following shows the daily count (in green) with a second order polynomial trend line in red.

The graph shows the trend line decreasing as solar maximum approaches (September 2024) should update daily and now increasing as we head towards Solar Minimum in 2029/2030.

However, there is a bit of a fudge. From approximately day number 700 to day number 850, the graph looks a little flat. I hold my hands up here. I disturbed my instrument to see if there would be an increase in Muon activity from the Sun. There wasn't, but there was a reduction in Muon count of about 12000 Muons per day. Quite significant. This area of the graph has been normalised to avoid a big step which would have distorted the trend line. Lesson learned, don't mess around with an experiment in progress!

On a shorter timescale, the Muon Counters saw a noticeable decrease in the muon count (3hour sample window) following the CME impact on 20260119. The reduction in count started the following day from the CME impact, clearly the increase in solar wind lagged the CME by a few hours.

2026-01-19 - Aurora

Details: Published: 22 January 2026

A CME impact at about 19:30 triggered an aurora which (for those with clear skies) was visibly across most of the UK and Northern Europe. Sunspot 4341 erupted on 20250118 at 18:09 UTC), releasing an X1.9-class solar flare.

I missed the peak (not paying attention to social media) but my NW facing meteor camera did capture a wide angle view from 22:00 to 23:00. The move is in mono (sadly), but the brightness of the aurora was outstanding, visible at times through cloud. This is a high speed time lapse movie.

My UKRAA magnetometer also detected its arrival, the storm and the tail off back to some sort of normality.

AT the outset of a storm I can often detect (as in this case) a pre-impact usually about 90 minutes before the main impact. this is visible in the dip in Bx and By lines at about 17:35UT. It appears to me that the main impact affecting this part of the Northern Hemisphere was at 19:15, a little earlier than the official NOAA impact time. An 'off the scale in both directions' disturbance is a serious storm and I understand that the storm was classified as G4 (Severe), one down from a maximum G5 (Extreme) storm.

Bx is the E-W deflection of the Earths magnetic field, By is the N-S deflection.

The storm abated slightly on the 20th but was still classified as G3.

At 19:00 on the 21st January, the storm appears to be over.

Finally, my muon detector captured the increase in Solar Wind associated with the CME (which caused a decrease in the muon count), delayed by about 24 hours as the Solar Wind travels far more slowly than the CME. The graph below shows the muon count from midnight 20250119 to 20250122 with a 4 hour sample window. The dip is very noticeable.

Looking forward to the next one..

Meteor Camera Highlights

Details: Published: 21 January 2026

This page lists some of the highlights, significant detections made by my Global Meteor Network Cameras. All in reverse chronological order.

Quadrantids Meteor Shower - 2026-01-03

Following on from the Geminids, I had another treat at the peak of the Quadrantids Meteor Shower. It was certainly not as impressive as the Geminids but not bad for a nights work while I was asleep. Incidentally, the Quadrantids refer to a constellation (Quadrans Muralis) that was demoted by the International Astronomical Union when it devised its official list of constellations at its inaugural meeting in 1922. The shower radiant is now in the constellation of Bootes.

UK00DA (SW Facing Camera)