The Blog
14/07/24 - The Duct Tape and Nichrome Wire DIY 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.
Dec Axis Tension Ring
Dec Axis Tension Ring Grub Screw Access Hole
RA Axis Tension Ring. Grub Screw Access Hole to the Right
Control Panel Covering Tension Ring Grub Screws Access Hole
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.
18/05/24 - The Arduino Rain Sensor Re-Commissioning
After much messing about I have finally got the Observatory rain sensor up and running again. When it was decommissioned for the star party the Arduino was moved from the Observatory rain sensor to the portable rain sensor and it did a fine job at the star party. So in order to get the permanent arrangement working again I had to take the Arduino out of the portable rain sensor and put it back in the Observatory rain sensor. Trouble is I put it in round the wrong way and blew its brains out by putting 9V on one of the data pins!
After I worked out what was happening I put a different Arduino in round the right way, tested it and commissioned it back into service. It now connects to NINA as the Safety Monitor and reports not safe with the application of a wet finger on the rain sensor plate. The housing has a heater under the sensor plate that switches on when the dew point rises to within 4°C of the ambient temperature to prevent condensation forming on the sensor plate and giving a false alarm, a common problem when humidity is high and a metal surface is facing the cold vacuum of space!
There are two Arduinos in the Observatory, the one that controls the rain sensor and another one that has a temperature sensor connected to it that I can use to see the current temperature and humidity from indoors using remote desktop. I’ve been playing with the coding so that it will control a bank of relays to allow me to switch the 12 volt DC supply to the telescope, camera and the Pegasus DC and data distribution Power Box.
Then finally I need to put into action what was originally the plan A Arduino project which was to control an extract fan when the temperature rose in the summer. At the moment there’s a solar controlled extract fan that comes on when the Sun shines and a mains powered one that I manually plug in.
Eventually I would like to automate the roof so that in the event of rain, the rain detector will change the state of the Safety Monitor which will trigger the NINA sequencer to park the telescope into a horizontal position, switch off the camera cooler, close the roof and send a notification to my phone to wake me up if I’ve nodded off on the settee.
15/05/24 - The Observatory Reassembly Process
After getting home from the Star Party my astronomy equipment stayed in the garage for a few days! But then I went for it and began the reassembly process. After hoovering up all the bits of cable strippings and spider webs in the Observatory, the next job was to put the mount on the pier and the telescope on the mount. I put the heated dew shield on the telescope and connected up all the 12V and USB cables. Having a permanent setup spoils you, remembering where everything goes is a bit of a head scratcher! It was the same at the Star Party.
I’ve decided to spend the Summer going for Messier images and adding some more to the Messier AP Challenge I started and never finished. A lot of the targets on the list are quite small so I took the Focal Reducer off the back of the telescope and returned the OTA to its native F10 2350mm focal length.
Once everything was connected and checked I shut it all down and waited for Civil twilight and for the promised forecast of clear skies.
Once the Sun had set I slewed round with an over exposed capture loop running to help find the Moon then reduced the exposure and pulled the image into focus. The Lunar X Clair-obscur had peaked five hours earlier and it was still just visible. So I saved a loop of exposures running for 30 seconds.
Next step was to calibrate the guiding. The PHD2 Guiding Assistant optimum position is 180 azimuth and 0 declination but very few stars there appear in my OAG so I slewed about looking for suitable stars and then clicked Calibrate. It finished the calibration with warnings of inaccuracy, so I ran the Guiding Assistant and as soon as it started the right ascension line rapidly shot off the top of the graph! It was at that moment I realised the Polar Alignment should have been done before the calibration! So I fired up the NINA Three Point Polar Align Tool and discovered the Azimuth was good but the Altitude was still at the packing up for transport Latitude setting! I got the Polar Alignment to within a total error of less than 10 arc minutes and recalibrated the guiding.
The first Messier target was M98 and ready to go in a NINA sequence I put together earlier in the day, but by now there was cloud cover and the high humidity was making everything quite wet. So I shut down and closed the Observatory roof. There’s always another night for the Messier AP Challenge.
11/05/24 - The Once in a Life Time Aurora Display Event
On the day I got home after the Star Party the sub atomic particles that had been travelling through space for the last few days following a coronal mass ejection from the sunspot group AR3664, finally hit the Earth's atmosphere. At the same time it was a New Moon, the sky was clear and xxx. These events together caused a once in a lifetime Aurora Borealis event that was visible all the way down to the equator! But I was a bit knackered after the camping trip and although I knew it was coming, nobody knew how good it would be. I thought to myself, yeah heard all that before and went to bed early and missed it! Gutted!
This is AR 3664 from the 8th May:
08/05/24 - The OAS Deep Sky Camp Star Party
I had a couple of days away as a guest of the Orpington Astronomical Society at their Deep Sky Camp in darkest East Sussex. And a great couple of days it was too! The weather behaved itself, I even got sunburned. And the night time sky was just as clear as the BBC said it was going to be. High humidity was the only problem. I arrived and set everything up, the new tent, still in the bag was supposed to be four man size but one sleeping bag laid diagonally worked out ok. After sorting out the electrical hook up I sorted out my new kettle and made a cup of tea. Then the tripod, CGX and SCT came out of the car boot and I started the assembly process. I've been set up in the Observatory for a while now and so had become out of practice with putting everything together. But the three small squares of OSB with a hole drilled in the centre worked to stop the tripod feet sinking into the ground. While getting the cables out and scratching my head my phone alarm went off to tell me that Solar noon was approaching. So I put a stick in the ground and lined the mount up with the shadow. If it was good enough for the ancient Greeks it's good enough for me!
Once everything was connected and switched on I fired up Stellarium, CPWI and NINA on my cardboard and duct tape protected laptop. After homing the mount I imported the Sun's coordinates and slewed towards it. The polar alignment must have been quite close because after ramping up the exposure to two seconds the edge of the saturated Sun was in the corner of the screen. A stepped reduction of exposure and a few taps on the slew controls soon had the Sun in the centre of the screen. I zoomed in and got the best focus I could then switched to my new Continuum filter, adjusted the exposure and saved a loop of 30 seconds of exposures.
As the setting Sun dipped below the horizon that evening I fired up the SCT again and waited for enough stars to appear to run the NINA Auto focus and three point polar align routines. The mount was quite a bit out. I probably forgot to use BST or something. The ancient Greeks didn't have to put up with this poppycock!
The humidity was already at 99%! I thought there was something wrong with my sensor. But you could feel it in the air and I had the feeling that this was going to be a short session. First target was the list of Globular Clusters in this Month's TSS Deep Sky Challenge. M3, M53, NGC 5053, NGC 4147 and NGC 5466. With just a single 60 second exposure on each one I quickly compiled an excellent challenge submission. None of the images are high resolution astrophotography competition winners but having the craic finding each one, plate solving to the centre of the screen, capturing and moving on to the next was a lot of fun. All of them were of sufficient quality to appreciate their beauty. Think I'll do a Caldwell Challenge or complete the TSS Messier Imaging Challenge next! Then I wanted to capture a before the event T Corona Borealis nova image in order to do a subsequent after the event image for comparison. So after a quick coordinates import from Stellarium, NINA slewed the telescope round to T CrB and a plate solve nudged it to the centre of my laptop screen. Again, I just captured a few 60 second exposures. I will be checking the news for the nova ready to capture the after the event image.
After that I moved onto the main target I had planned, Abell 1656, the Coma Galaxy Cluster in Coma Berenices. I calibrated the guiding, slewed to the target, checked the focus and fired up a pre-prepared NINA sequence. That soon settled into its thing so I went for a wander to see what others were doing. My homemade Arduino rain sensor connects to NINA through the Safety Monitor and it has a heater that prevents false positive detections that would be caused by condensation on the sensor plate. When rain is detected NINA sends a notification to my phone and parks the telescope. The humidity had been at 99% for so long that the anti condensation measures failed! The rain sensor started bleeping, my phone started ringing and the telescope started slewing! I realised what was happening when it was clear that the sensor plate was wet but there was no rain. I disconnected the rain sensor and fired up the sequence again with the if !IsSafe park telescope line deleted from the sequence but by now the guiding was deteriorating and struggling to stay below a total error of 1.0. The sequence aborts the exposure if the total error is above 1.5 for 5 PHD2 exposures in a row and most exposures were getting chucked! I don't know if the humidity was affecting my USB connections, my CGX motors or my polar alignment slipping off due to the soft ground but I shut the sequence down, disconnected everything, switched off and went to get my head down.
The next day was good, I lounged around relaxing, listening to astronomy and harmonica podcasts, chatting to the very nice OAS people and cooked some chilli egg fried rice for my dinner! As the Sun set we saw the two day old thin waxing crescent Moon on the western horizon. If I had been prepared I would have captured it but by now it was too low. The second night was wholly allotted to capturing more data on the galaxy cluster. First step was to re-do the polar alignment, the OSB plates definitely looked like they had sunk a little into the soft field grass under the weight of the CGX. The NINA polar align tool plugin reported 1.5° total error so I started a re-adjustment. The laptop screen was looking the other way from the position of the CGX AltAz adjustment knobs so I had to keep running round to the back of the mount to adjust then back to the laptop to check, all this took a while. After a few minutes the plugin told me I was taking a long time and I might want to start again! How rude! The BBC weather said we could expect a lower humidity tonight so after I set up the rig, changed the sequence to abort above 2.0 and changed the 9 volt supply to a 12 volt supply to the rain sensor heater to increase the temperature on the sensor plate if the dew point was close to the temperature. Then, once setup I fired up the sequence and went for a wander again. At midnight I set an alarm for 02:00 and went for a kip. At 02:00 the guiding was poor again and the exposures were aborting. So with a total of nearly five hours of exposures I went back to bed feeling quite pleased with myself.
An excellent Star Party and a big thank you from me to the OAS.
Right, I'm off to process some galaxy cluster subs.
04/05/24 - The Temporary Setup Experiment
The Observatory decommissioning went well today. I disconnected everything and laid the cables out in the garden at the pre observatory telescope position. I took the telescope off the mount and the mount off the pier then put them together again on the tripod. Once everything was reconnected I plugged the USB into the laptop and switched on the extension lead. Then while I was adjusting the cardboard box that protects the laptop from dew, the rain detector started bleeping! A fine mist of rain had started to fall and my DIY Arduino rain detector had proved its worth! So I moved the telescope to a horizontal position and pulled the tarpaulin over it and the boxes housing the power supplies and the laptop on its table.
The rain didn't last long. A couple of hours later I took the tarpaulin off and switched everything back on. It has been a while since I used the laptop to control the telescope and a lot of things needed updating. I had to set up all the equipment and build a new profile in NINA. The ASTAP plate solve database was out of date so I downloaded a new 5000 stars per degree database. My polar alignment was a guess and it turned out to be 8° out but I didn't bother correcting it. The object of the exercise today was to double check I have everything in place for the Orpington Astronomical Society Star Party.
After a couple of hours the humidity had risen to 99% and things were getting wet. So I turned the power off, disconnected everything, rolled up all the mains leads, 12V leads, USB leads, put everything in their temporary Star Party boxes, put the telescope in its travelling case, put the mount, still on the tripod in the garage and turned out the light. All that took almost an hour. Then I sat down pleased that I built an observatory so I can just shut the roof and lock the door when I'm done!
03/05/24 - The Inaugural Blog Post
Thought I would start a Blog! It seemed like a good idea to document my astronomy and astrophotography journey here as well as the images in the astrophotography sections.
We had a clear night last week and I captured some data on the Messier 81 Messier 82 galaxy pair. But I haven't managed to finish a process that I'm happy with yet. Mostly since then it's been cloudy so the roof has stayed on the Observatory.
I've been working on an Arduino sketch that will allow me to remotely switch the power supply to the telescope mount, the camera and the Pegasus Power Box from the comfort of my arm chair using a set of four relays. The breadboard prototype version works well and allows me to click on the computer screen to switch four LEDs on and off! Now I need to make the stripboard soldered version and install it in the Observatory. There's already two Arduinos in the Observatory, one that measures temperature and humidity, calculates the dew point and displays it on the computer screen, which I can then look at remotely. The other controls the rain sensor for the imaging sequence Safety Monitor.
No rush to get it installed though because I will be taking the telescope out of the Observatory to set it up on the tripod as a trial run for an upcoming star party camping trip. Then I'm going to a dark site in the middle of East Sussex to have a go at some Bortle 3 astrophotography as a guest of the Orpington Astronomical Society. I need to make sure I have everything needed to run the rig with just a laptop and a 240V supply.
It's probably good timing since the Observatory could do with a spring clean! Funny how you start off with all good intentions and neatly run cables in conduits and then as changes happen, as you do a tweak here and a modification there, all good intentions go out of the window!
Here's the setup in the Observatory just before it was de-commissioned.
