The Blog

19/11/24 - The Friction Reduction Rolling Roof Modification

When I designed the observatory roll off roof I weighed up the decision to use plastic wheels or metal V groove wheels. In the end I went for the plastic wheels to save cost. I used a pair of 6m x 50mm angle iron tracks with one side laid flat and the plastic wheels guided by the vertical section of the angle iron. This worked well initially and the gate closing electric motor that was installed was able to operate the roof without any problems. Over time though the lack of a perfectly flat track and the lack of bearings in the wheels has led to an increase in friction to the level that the initial inertia required to start the roof moving was too much for the motor. 

So the solution was to do what I should have done in the first place and install metal V groove wheels with bearings. In order to fix them to the under side of the roof I hired two Acrow props to lift the roof each side in turn in order to get a screw driver to the fixing screws. After removing the motor and the angle iron fixing screws on the external section, then opening the roof and fixing some 4”x2” in the corners to spread the weight, I jacked up one side just enough to get to the wheel fixing screws. With the wheels removed I took out the angle iron fixings to the internal section. Now that all the fixing screws were removed, with my son’s helping hands on one half and myself on the other, we were able to rotate the angle iron so that it was orientated with the 90° facing up. Once in place we fixed it down using screws at a 45° angle through the holes that held it previously plus a few more newly drilled and countersunk on the opposite side. The new metal V groove wheels were easy to fit as the fixing holes were in the same place as the old wheel fixing holes. With the new wheels fitted  the roof was lowered down on the Acrow props to place the wheels on the track in its new configuration. Then it was a simple exercise to repeat the process on the other side.

With the application of some grease to the metal wheels and the track, the new configuration worked perfectly. The roof rolled with a much lower friction and initial stiction. It also rolled more quietly which was a pleasing surprise. The new wheels have raised the roof by a small amount so some further modification to the trims will be required but that can wait for another day. 

16/11/24 - The Autumn of my Discontent Tribulations

Now is the Autumn of my discontent! The last astro image I captured was from almost a full month ago, an attempt at Mirach’s Ghost, NGC 404 for the Sky Searchers Astronomy Forum Monthly Challenge. Clouds eventually ruined that night’s proceedings as happened the previous few sessions. Since then we have had nothing but constant cloud cover caused by a massive high air pressure over Western Europe, the size of Western Europe! The slowly rotating anticyclone has been pulling the moist air up from France and Spain which sits above us as blanket, unbroken, unforgiving, a cloud with just the odd short duration gap. I even turned off the All Sky Camera after submitting to the futility of capturing cloud all night long. 

I was going to go to the Autumn 2024 Deep Sky Camp in darkest East Sussex as a guest of the Orpington Astronomical Society, my third trip away with them. I was really looking forward to astro imaging under a Bortle 4 sky. My new Grab’n’Go rig was ready to grab and go, I had been using it in the back garden connected to the laptop as a trial run to make sure I had all the required software installed and all the leads, cables, gadgets and accessories that I would need to take with me. I even bought a new tent! A nice big one that I can stand up in. But the weather was forecast to be really unsuitable for astronomy, so after loading everything into the car, I cancelled at the last minute and put everything back in the garage. 

Also, our hypocritical neighbours have predictably added to the lack of astro imaging opportunity. They leave a light on at the back of their house which lights up the rear elevation like a Christmas tree in a long duration exposure. It’s not in direct view but it does cause a gradient in any image looking South East that degrades the data and I have to deal with in processing. I have mentioned it but to no avail. I tilted the All Sky Camera towards the Southern rooftops for a few nights during a promise of a couple of hours of clear sky in that direction after Sun set with the hope of capturing an image of the rapidly fading Comet C/2024 A3 (Tsuchinshan-ALTAS). The sky was clear in the area where the Comet was but the Comet was nowhere to be seen in the image due to the light pollution. Thanks Hypos! They have a Silver Birch tree in their back garden which totally blocks my view to the West from the Observatory. It’s not the end of the world, it was there when we bought the house and there’s not much to be seen in that direction below 45° elevation other than the London light dome. They used to crop it each year but since I built the observatory they have just let it grow. I asked why and was told with a sideways glance that it was to hide the new phone tower in the distance. This is bollocks of course, the tree is already twice as big as it needs to be for that purpose and my observatory is in a much better position to hide the view of the phone tower from their back door! Spite is an odd choice of response for church going folk!

03/09/24 - The All Sky Camera Installation

My ASI224 Camera was bought for Planetary imaging but I never did use it much. Then I read about the AllSkEye software on the Sky Searchers Astronomy Forum, so I downloaded it and installed it. And I have to say it is an excellent package. Once set up it will record images of the sky directly overhead, all night long. Then in the morning it automatically puts all the frames together into a time lapse video and it also stacks all the frames to produce a star trail image. It also joins the centre vertical row of pixels from each frame and stiches them all together to produce a Keogram image. But I haven't worked out how to do that yet!

I mounted the camera on a bracket on the side of the observatory, under a transparent dome to keep the rain off. 

I was quite pleased with the results of the All Sky Camera so I've added an All Sky Camera Page to my Astrophotography Section to show off the results. 

02/08/24 - The Astronomy Photographer of the Year Competition

The Royal Observatory Greenwich holds an annual Astronomy Photographer of the Year competition and the best of the entries are exhibited each year in the Maritime Museum. The images are stunning. I went to the exhibition in 2017 when it was held at the top of the hill at the Royal Observatory, when I was studying there. But then I didn't go again until last year on the invitation of my good friend Mick. So it seemed only fair that I should return the favour this year. Mick offered to pick me up from my house but I think it was an excuse to come and see my back garden Observatory.  Or it might have been his well known magnanimity. We arrived at the Maritime Museum and walked along the path to the entrance with a fine view of the Royal Observatory.

After a quick coffee in the Maritime Museum café, we made our way to the exhibition. The exhibits were excellent, as you would expect. Lots of aurora images at this time of Solar Maximum. Awe inspiring Deep Space images, Planetary images and Solar Images. Mick found the Solar captures interesting, I particularly liked a Night Scape image of an old building showing the Winter Hexagon surrounding Betelgeuse in Orion in the background.

Here's a link to the Exhibition Entries Shortlist if you fancy having a look.

Afterwards we had a very nice Burger and a pint on the pavement outside the Greenwich Tavern with William IV looking on, a Monarch I will always be grateful to for building my most favourite place in the world!

Well that's the second time I have attended the event with Mick, I hope we have many more.

28/07/24 - The Royal Astronomical Society Annual Picnic 

The Royal Astronomical Society holds an Annual Picnic for Fellows and friends in Greenwich Park each year and I have never been able to go due to work or other prior appointments getting in the way. But this year I did go. I drove to Greenwich Park and parked. As I walked along the Chestnut Tree lined path to the designated meeting point, the General Wolfe statue, I enjoyed memories of coming here many times before. I sat on a bench by the statue and took in the views of the Old Royal Observatory where I studied astrophysics, the dome of the 28" Refractor through which I have seen excellent views of Venus, Albireo and others, the gnarly old chestnut trees from which I have taken conkers and germinated them a few times and the view down the hill of the Maritime Museum, the Canary Wharf office blocks in the background, the towers of the old Greenwich power station and the white dome of the O2 arena. 

While I sat waiting, I wondered about my old friends. I wondered if Roger was still teaching, if the other Graham would be there, if Alex was still a famous rock band agent, if Eddy was going to be there so I could tell him about my new harmonica, if Jon was recovered from his ill health, if Judith was still married and if Michael was still a pervert.

It must have been coming up to 1pm because the Greenwich Time Ball was rising. As it dropped I noticed a bloke taking a picture of it and I said to him it must be 1pm! We started talking about the 28" Refractor, he said that he had operated it so I asked if he was a Fellow of the RAS, he was, he too was here for the picnic! In fact he was Q the organiser. We walked 100m East to the site of the picnic, under an old oak tree, from the position of the Greenwich Meridian Line to the position of the International Reference Meridian, separated by 5.3 arc seconds because one is perfectly perpendicular geometrically and the other allows GPS satellites to orbit the gravitational centre of the Earth's slightly non spherical centre of mass.

It was good to see Roger reclined on his picnic blanket with a couple of students from his current Astrophysics class and a good spread of picnic food. We chatted about this and that, people past and people present, RAS events and astronomical events. It was good to see him again. And I had a good chat with Alan, one of Roger's  current students, he studies particle physics and was interested in my astrophotography.

Greenwich Park is one of my favourite places in the world, it's full of people of all ages, colours, creeds and languages, all strolling about  relaxed and congenial, enjoying the sunshine, the views, the history and the peace. When my four hour allocated parking slot was coming to an end I shook hands with old friends and new and was glad to have been able to join in this year.

14/07/24 - The Duct Tape and Nichrome Wire Heated Dew Band

With the Kentish relative humidity regularly in the over 90% range and the objective lens easily reaching the dew point when pointing at the cold dark vacuum of space, the new Stellamira needed a heated dew band. So I decided to knock up a duct tape and nichrome wire one to suit. My Pegasus Power Box Advance has two dew controller outputs, one of  which I use to connect my SCT heated dew shield to. The PPBA struggles to control both the dew shield heater and my heated Cassigrain lens ring at the same time, so I made an IC555 controlled dew heater controller for one of them. But the reported load was about 1A for both, so I decided to design my new heated dew band around that figure.  

I measured the resistance of 1m of the nichrone wire at 8.25Ω and calculated the amps per m current flow. Then calculated the length of wire required to allow 1A to flow. My spreadsheet returned a value of 1500mm. So I cut off a 1500mm length, put 12V across it and measured the current at 1.06A. Close enough! 

Then I measured the circumference of my Stellamira dew shield and worked out the number of zigzags of the 1500mm length of nichrome wire required for the correct length of dew band. Using small pins I put in two rows either side of a length of duct tape to create a former for the wire. I folded the ends of the duct tape over the other side of the wire zigzag and removed the pins. 

The intention was to solder a short single core flexible cable to each end of the heater element but the solder didn’t take so I crimped the connections. Then I soldered the connections to a 10m length of twin flex and used heat shrink tubing to insulate and protect the joints. I soldered an RCA plug on the other end of the flex. 

I wanted to insulate the outer surface of the element and I only had a length of fairly stiff expanded foam which wasn’t ideal but it was the right width. So a length of this got duct tapped to the back of the heater element. A softer, more flexible insulating material would be better so I might change it later if I come up with a better idea. A couple of lengths of Velcro, duct tapped to the outer side of the band finished it off.   

I look forward to trying out my new heated dew band. May the cloud gods smile upon me. 

12/07/24 - The Electronic Auto Focuser Engineering Challenge

A new astrophotography telescope needs a new Electronic Auto Focuser to work well with a NINA capturing sequence, especially if the intention is to operate the rig whilst sat on my arse, remotely from the comfort of the front room! So I went with the ZWO model. The new ZWO EAF is a 5V stepper motor unit which takes both its power supply and its communication connection from the USB hub on the back of the ZWO ASI294MC Pro camera. So it would be a simple case of bolting it onto the telescope focuser assembly, plug it in and away we go. Or so I thought!

The good folks at First Light Optics confirmed compatibility with my StellaMira 110mm Refractor and forwarded links to installation procedures for a whole rake of different telescopes. Unfortunately, the StellaMira 110mm wasn’t on the list! This telescope is a re-badged, tried and tested Orion EON 110mm f/6.0 ED Apochromatic Refractor, newly available from Stellamira with an upgraded hybrid-drive rack-and-pinion focuser with integral 8-ball-bearing system, helical gear drive, and dual-speed motion. Excellent smooth focus movement but the redesign doesn’t allow space for the EAF bracket! 

So in order to line up the EAF bracket centrally on the back of the focuser assembly, the bracket had to be modified. I will hold my hand up and admit to being more than just a bit reticent to take my shiny new telescope apart to modify it but again, the ever helpful FLO Team came to the rescue. I explained my dilemma and they sent an instruction set from a customer that had recently had the same issue. 

The first problem is the focus tension screw that is in the way of the bracket. I filed a section of the side of the aluminium bracket to allow it to nestle snugly next to the focus tension screw. There is an M4 screw hole very near to this knob and I aligned the central slot of the bracket with this hole and the smaller M3 hole that accesses the focuser's coarse knob fixing screw. That results in the bracket lying along the same axis as the adjuster axle. The central slot is too narrow to take an M4 screw so I used a round needle file on it until the M4 screw could fit through. With the modifications made, the whole assembly went together well.

The next step was to connect it to NINA. I plugged in the USB, selected the ZWO Focuser from the Equipment/Focuser tab selector drop down list and clicked on the settings icon. This fires up the ZWO Ascom setup window. A quick test of a click on both the in and out buttons confirmed everything was ready to go. The telescope focus tube is helpfully marked with a mm scale, so I wound the tube in to 5mm and clicked the Ascom set to zero button. Then I wound the focus tube out incrementally. The maximum is 95mm so I stopped at 90mm and this gave a reading of 28500 steps. 

An excellent engineering challenge! I look forward to the next clear night for the first test and see how it performs an autofocus routine. 

08/07/24 - The Mount Axes Striction Reduction Modification

My new Grab n Go Rig is brilliant. I can't wait to use it some more. When I first got the mount the RA and Dec axes were quite stiff, so upon the helpful advice of the supplier, First Light Optics, I tweaked the bearings to loosen both the RA axis and the Dec axis. First word of caution here, don't do this on a brand new mount without the permission of the supplier to avoid warranty issues. 

To adjust the Dec axis I unscrewed and removed both the counterweight bar and the end cap to reveal the Dec axis bearing tension ring. This ring needs to be slackened off till the Dec axis striction is gone. There are two grub screws holding the ring in place. Each has to be loosened in turn using a 2mm Allen key accessed through a hole in the side of the housing. Then with the Allen Key still in the second grub screw to hold the tension ring, I turned the OTA dovetail saddle anticlockwise to loosen it. The tension ring was then re-tightened just enough to remove any sideways movement on the saddle. Once I was happy it was tight enough without re-introducing striction, I re-tightened the two grub screws through the access hole.  

To adjust the RA axis I unscrewed the cap to reveal the RA axis tension ring. This ring has three grub screws but the access hole is hidden behind the mount control panel, so I took out the four screws holding the control panel in place to reveal it. After loosening the grub screws with the 2mm Allan key and again leaving the key in the third screw, I rotated the Dec axis to loosen the RA axis till the striction was gone. Then re-tightened it again to remove any sideways movement whilst turning the Dec axis. Once the grub screws were re-tightened, the control box replaced and the end cap replaced, I had the smooth operator that I had hoped for. 

I look forward to trying out my new low friction mount. May the cloud gods smile upon me. 

29/06/24 - The New Grab and Go Rig Excitement

After the disappointment of the last grab and go setup I had another go at finding something suitable. This time I asked the excellent people at First Light Optics for their opinion and narrowed the choice down to a StellaMira 110mm ED APO with an Adjustable Field Flattener and a Celestron AVX mount. Strangely, the first night after delivery was free of cloud and the jet stream was forecast to be way up above Scotland. The StellaMira came with a small dovetail bar that fits in the AVX but doesn't allow much movement of the OTA rings so with the Field Flattener and the camera on the end of the focuser it wasn't possible to balance the Declination axis. I expect I'll find a solution.

So after getting everything assembled and connected I fired up NINA and connected the mount and the ASI294MC Pro camera. I did a rough initial alignment placing the tripod where my CGX tripod used to go before I built the observatory and slewed to Vega to focus. Vega wasn't in the field of view but I used the stars that were there to get a rough focus. Then I plate solved those stars and Vega appeared dead centre of the PC screen. Using my Bahtinov Mask I spent the next half an hour focusing Vega, adjusting the back focus on the Field Flattener to focus a periphery star and then refocusing Vega, trying to get a good balance. I got it close but not perfect. I'll have to read up on a good Adjustable Field Flattener focusing method. The next step was to do a NINA three point Polar Alignment. This plug in is a work of genius! And the AVX adjustment is more positive than the sloppy, backlashy CGX altitude adjustment. I got it to within 3 arc minutes of total error, good enough.

My First Light Image was a quick slew from Vega to Messier 13, an old friend! It was interesting to see my new field of view. I set up a quick unguided sequence to capture 20 minutes of 30 second exposures, then slew to one of Brett's Carbon stars for July, VY UMa to plate solve and capture another 20 minutes of 30 second exposures. 

While the new rig was doing its thing I went and sat in the garden to have a look about. After about 10 minutes in the dark I could see Kochab and Pherkab and possibly one of the mag 4 stars in Ursa Minor. Not bad for a close to Solstice sky. Vega and Arcturus were steady in the sky, there was not a twinkle to be seen, so the jet stream forecast was right. I got the binoculars out and had a look for M13. An uninspiring grey smudge didn't come close to the beauty of a good resolution image. Conversely, VY UMa, easy to find just north east of Dubhe, it appeared like an orange jewel and was a bit of wow that the image won't convey.

With the short capture test complete I put the binoculars away, slewed the telescope to T CrB and grabbed 20 x 30 second frames for the TCrB Thread. It's still there, it hasn't exploded yet! For a test of a deep sky object I slewed to Barnard 347 and set up a sequence for 100 x 30 second exposures. The butterfly wings just fitting nicely in my field of view. The Moon was now on the horizon although behind my house, the focus was drifting, the temperature was still 21°C so the aged 294 did well to keep at -10°C and the humidity was at 77%. I haven't processed it yet and it won't be a masterpiece but it will be interesting to see what I get. So I need to get an EAF and a guide scope or OAG. I need to do some research into adjustable Field Flatteners and I need to find out what to do about the dovetail bar and the excessive friction in both the AVX RA and the Dec axes. But other than that I'm well chuffed! It's great to be in the Fracktor Club. 

07/06/24 - The TSS Messier AP Imaging Contest

The Sky Searchers Astronomy Forum has a Messier AP Imaging Contest which I started having a go at in 2019, capturing with my Canon 600D. I compiled the first list of 40, earning a Forum Profile Badge. Then the challenge kind of slipped down the list of imaging priorities and I didn’t manage to achieve the next Badge, the M80 level. So this summer I resurrected the Challenge and carried on where I left off. 

So I have added three more, elliptical galaxy M85 in Coma Berenices, the Orphiucus globular cluster M12 and the open cluster M39 in Cygnus. This brings my total up to 65. The next 15, to take me to the next level will have to wait for the autumn skies to come round. The Virgo and the rest of the Coma Berenices galaxies I had planned are too far to the west now and hiding behind the swiftly growing silver birch tree in the neighbour’s back garden.

Here’s my TSS Image gallery:

TheSkySearchers - Graeme1858 Messier List 

25/05/24 - The Grab and Go Disappointment Fiasco

After the complications involved in using the observatory SCT at the Star Party, or more specifically putting it back together again afterwards, I decided to get a "grab and go" rig. Something more transportable, something smaller that would fit more easily in the back of the car, that could be used at star parties, taken on holiday and generally be more versatile.  The mount would still need to be a motorised goto but the telescope could be quite a bit smaller giving me a wider field of view. I found a Skywatcher 120mm achromatic doublet refractor on an HEQ5 Pro mount for £200 less than everyone else was selling it. After waiting a couple of days for a delivery date confirmation I phoned them, only to be told that they had none in stock! So I went to the next supplier on the list that had one on the shelf and put my order in. A couple of days later I had become a member of the refractor owners club! 

The excitement didn't last long. I set up my new telescope in the back garden where the CGX used to go before I built the observatory. But this rig was different, I could lift it! Then I waited for the night to come. The Skywatcher HEQ5 mount is supposed to be a tried and tested workhorse but this one was a sickly dog that made unhealthy noises when it slewed and failed to track when it reached its target, showing star trails where stars should be. Worse still, when it did manage to stay on target the Skywatcher 120mm achro captured images of stars that were surrounded by blurry halos. Either it was not possible to focus the thing or the achromatic chromatic aberration on this refractor was a whole lot worse than I was expecting it to be. 

So I packed it up and sent it back.