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Scope review

My largest scope up to buying this one was a 12″ manual Dob, with some lovely views and memories from it. I had been hankering after an upgrade for some years though with the intent of getting a scope that would satisfy my aperture fever.. I wanted the largest aperture I could handle by myself, without needing to have it stored assembled. I’ve not got the room to keep a really large scope fully assembled so I needed to make sure I could assemble and disassemble whatever scope I got in a fairly short space of time given Irish weather, and without too much bother and faff, otherwise I’d just get tired of having to build each observing time.

I did my research on the scopes available, and this particular model started to filter up to the top of my shortlists. 20″ aperture, truss construction with no single piece heavier than about 30kg, generally reasonable to good optics based on other owner experiences, and a goto system utilising the well known Synscan handset, and the support of a large brand and a known-good dealer network.
I also knew that I would probably have some engineering to do myself with the scope, but I’m happy with that as I’m a bit of an old-school hardware hacker and tinkerer at heart. Fettling something does not phase me at all.

This particular scope arrived, and I spent a good while with the first assembly, figuring out what needed to go where, and what snafus were presenting, The manual is abysmal really, but the scope is not difficult to figure out to someone any way mechanically minded. I did need to add more counterweight but that was to be expected with a Paracorr and 100-degree eyepieces in the focuser. The focuser could do with an upgrade to a compression ring fitting at minimum but it does suffice for the purpose. The focuser movement is smooth and clean which is really useful!
The truss construction with the ball and sockets construction method is well thought out, and means that collimation is fairly repeatable upon each assembly.
The shroud is a lovely addition, though it did take me a little bit of time to realise that the velcro seam runs under the “tube” with the hole in the shroud near one edge actually goes over the focuser and finderscope. There are improvements that could be made to the shroud but it’s pretty good when tightened at the top and bottom over the truss attachment bolts. When tightened properly it does not come into the light cone and also provides a lot of stray light protection if one is observing in a not-dark location. The shroud also prevents body heat and exhaled breath from reaching through the light cone and affecting the views and optics.
The goto system is reasonable, once aligned and synced on something in the neighbourhood the gotos are then fairly good. It’s a good idea to sync on a bright star near where the desired observing object lies, to get the best chance of getting that object in the eyepiece.
There is an altitude stop that prevents the tube from getting to within 11 degrees or so of horizontal. I moved that stop to allow my scope to get to the horizon. There’s no apparent issue with that once I had the correct counterweights for my setup.
I’m 5’10” tall, and I need a step or two once my target reaches above 37 degrees altitude, but I was expecting this for a scope of this size. I could not afford a scope with f/ratio of under 3 at this point. Two steps up a stepladder is all I need to get observing at the zenith, so it’s not too bad at all. I may invest in a good Catsperch chair at some point in the future. I’ll have to see how I go with a full night of being on a ladder.
If there’s a breeze blowing and the shroud is on the scope, then there will be a bit of movement seen at the eyepiece. In general though the views are steady, and there’s no loss of target when swapping eyepieces out which is a real boon for me after using the 12″ where I’d have to re-find the target again.

As for the optical quality, I’ve not seen any issue yet that I’m worried about. My seeing is generally in the 2-4 arcsec range on average nights, under an Atlantic jetstream. I’ve had a few evenings out under mediocre skies so far, but I’ve been able to get E and F in the Trapezium pretty much with ease for most of time. Stars are scintillating balls of mush, but a ball of mush that is seeing-caused. No astigmatism showing up so far, no real roughness apparent based on my testing at this stage. When the mirror is cooling down it does show an undercorrection but this appears to lessen as thermal equilibrium is reached. I haven’t had a long enough session yet with the scope to be able to determine the finer optical quality, but that will be done in time. So far, I’m happy enough with the performance – it’s certainly the case that I’m being atmosphere-limited, and that’s a nice place to be.

One thing that is really of interest with this scope, is that it appears to be exceptionally suitable for Electronically Assisted Astronomy, and for Lucky Imaging of DSOs. The f/ratio of under 4 and the aperture of a half-metre means that deep exposures can be obtained in a very short space of time.. I got to about mag 19 with about 4 min worth of 1.7 second subs with an ASI294MC-Pro, and seeing that result had my jaw hit the floor. The tracking is probably not good enough for multiple tens of seconds of sub lengths, but a low noise camera and a lot of disk space will work wonders..

The known issue of mirror flop causing collimation skew when changing altitude is fairly easily resolved, and I have also added a Kendricks secondary dew heater as I’ve had the secondary mirror dew up when not using the shroud. I may yet add a boundary layer set of fans and fans blowing at the rear of the primary to aid in thermal equilibrium

If you are in the market for a transportable half-metre telescope that one reasonably fit person can assemble and disassemble with relative ease, that provides lovely eyepiece images, and that does not cost the earth, then the Skywatcher Stargate 500p is a scope that should be high on your list.

New toy arrived..

It arrived..

It’s a Skywatcher Stargate 500p Dobsonian truss-type telescope. The primary mirror is a full half-metre wide, it has a 2 metre focal length. It’s an absolute light bucket. It comes with a computerised goto drive, and it takes me less than about 10 min to set it up and have it running.

It came in 4 large boxes, with a shipping weight of about 95 kg.

I updated my eyepiece collection to suit the f/3.94 focal ration, with a Paracorr, a few Ethos 100-degree eyepieces, and a widest-field Explore Scientific 25mm 100 degree eyepiece. I now understand exactly why people got for the green eyepieces when they can..

The views through this scope are, not surprisingly for a 20″ scope, absolutely spectacular. Theoretically from a dark sky this scope should get visually down to mag 16.2 or so. Trying my hand at some Electronically Assisted Astronomy with the ASI224MC I got a nice view of the core of M42, about 2 min of stacking of 1/8th second (!) exposures and managing to capture some of the proplyds (nascent star solar systems):

Using the larger 4/3rds OSC CMOS camera that I also got recently (an ASI294MC-Pro) I stacked 2 second subs for ~4 min to get this M1 Crab nebula with lots of detail and down to mag 18 stars:

After a while the conditions overhead deteriorated poorly to the point where I could not make out the shape of Leo and the Plough asterism was becoming invisible. I persisted with taking subs of M51 to get this pic: 

Overall – I’m *really* impressed with how this scope is performing for me. It’s a little bit of a bother to disassemble and reassemble and the heavy bits are rather awkward to try and get through a door – but they fit through a door. I’ve also found that I can strap the scope to a handcart and maneuver around the garden with ease, which bodes well for outreach with Astrosoc.

I have not yet had an opportunity to check a Moon or either of the large planets in the morning sky yet, really looking forwards to that..

PC update – new hardware in the main desktop

I got my hands on a Xeon E5-1680V2 processor last week. This is about the best CPU that I could get for my motherboard, and it’s an overclocking monster. Comfortable at 4.7Ghz at <80 degrees, currently at 4.6 and staying under 75 after extended benchmarks.

Adding to this the fact that I finally jumped 4 generation of graphics cards by updating to a Zotac 2080 Amp MAXX card, gaming and GPU computations are now impressive. All games at max details at 1980×1200 (none of that tiny HD resolution) now are pretty much stable at 60 FPS, and oh *so* pretty.

After having to update the PSU to a decent Corsair HX850i it now runs without clocking down or bluescreening in games, and makes me quite a happy camper. The PC name as “Behemoth” is still very much relevant. Pretty much the only update left for the PC is to go to 4x4Tb drives for the RAID array. No real cost benefit to going any newer or bigger or better with any of the components.

Not too bad for a system originally built some eight years ago, and still on the same motherboard, memory, and spinny disks. Updates to CPU/GPU/system SSD did happen over time.

Userbenchmark here:

Now off to go kill demons in Doom 2016, nazis in Wolfenstein II TNC, and to go raiding for tombs in the various new-series Tomb Raiders!

More retro PC updates

So, the Optiplex 960 bios does not boot with a Xeon e5450 chip, and had I done my homework on that, I would have been able to find that out. However, I sourced an Asus P5KE motherboard with 8Gb of DDR2-1066 and a Q9550 chip in it for a decently low price, to further my retro PC ideas.

The Core2-Quad q9550 dropped straight into that Optiplex, making that a quad core 2.83 instead of the dual 3.0 it had been. Now I can install XP-32bit on that and get the mid-Naughties retrobox up and running properly.

The Xeon e5450 works perfectly in that new Asus board, overclocks like a demon, and I think that I’ll build that up to being an early Win7 retro box, though it won’t be retro for a few years.. When I get the upgrade card for my behemoth of a desktop, the GTX660 will go into this box to update from the QuadroFX380 currently there, and I may keep the Quadro card in the system as it’s not a low-profile card that could fit in the Optiplex. That system setup will do the 2010-era games very well indeed.

So here’s the current list of retro PCs and the years of games they are aimed at:

  • 1995 – Dos, P3-600, 256Mb, 80Gb, Dos7.1/Win3.11, Matrox G400MAx, Audician32+D2
  • 2000 – P3-1.13, 512Mb, 16Gb CF, Win98SE, GF4-Ti4200, SB-Audigy
  • 2005 – C2Q Q9550, 4Gb, 250Gb, WinXP-sp3, Quadro K600, SB X-Fi
  • 2010 – e5450, 8Gb, 250Gb, Win7, Quadro FX380, onboard Azalia 7.1 (for the moment)

The Behemoth of a desktop is currently:

  • e5-1620 V2, 32Gb, 500Gb/4x1Tb, Win7, GTX660, Asus Xonar.

With the expected upcoming windfall of cash soon, I’ll be updating the Behemoth to:

  • e6-1680 V2, 64Gb ECC, 500Gb/4x3Tb, Win7, RTX2080ti, SB Z.

(that will definitely keep what is a seven year old system faster than most current new builds. Might get a decent 144khz 4k monitor as well)

I still also have the PS2 and the PS3 – I must investigate the modding of both of those for fun and curiosity. My homebrewed Wii is also present and accounted for, as is my Amiga1200HD with the Blizzard 1230/IV accelerator.

Maybe it’s time to reposition one of the RPIs to be a retro arcade machine / console emulator. That could be an interesting project for the Springtime.

A lovely little telescope, resurrection and refit.

I answered an ad on one of the astronomy forums I regularly peruse, where someone was getting rid of a badly water-damaged telescope. I figured it would make a nice project for myself so why not reply and see how much it was going to cost me.

A mate of mine picked up the telescope from the owner, and warned me that it appeared to be in relatively bad condition, so I was a little apprehensive.

When I collected the scope and paraphernalia from my friend, I recognised the scope as a Celestron CPC800 – a Schmidt-Cassegrain design with 8″ aperture and focal ration of f/10, with the computer control and GPS-based time and location finding. With the scope came the tripod and spreader bar, the standard 8×50 finder, a prism diagonal with 1.25″ visual back, an older NexStar handset, and the power cable with a generic wallwart adaptor. The tripod showed evidence of corrosion under the black paint on all of the non-chromed parts and a little surface rust on the bolts that hold the scope down. The ports on the fork base were showing heavy corrosion on the contact wires and a lot of green crud at the base of the ports, which did not bode well for the mechanicals at that point.. The tube was showing a lot of corrosion, with lots of the black paint paint on the front dell having been completely flaked off, and the metal underneath turning to a white flaky powder that had dusted all over the corrector plate. The primary mirror itself looked in reasonable condition actually, with a very light coating of dust but pretty much bright and untarnished in any way. The secondary was also appearing to be pristine

I took the scope home, and immediately started to disassemble, at 11pm, in my kitchen..

Attempting to power on the scope with power from the 12v lead acid battery that I use to power the AVX mount with, led to seeing a bright LED on the base lighting up, but absolutely no response from the handset. Knowing that the two AUX ports are parallel with the HC port, I tried the handset in the two AUX ports to have a response from the third port. The handset was alive at least. Motor errors 17 and 16, somewhat expected, showing a lack of communication with the motors. But, the motors would move but not stop. That was a really good sign! Maybe the scope could be resurrected without too much expense.

So, after a little research, I found I could replace the two circuit boards that are attached to the top plate of the fork base for a reasonable cost. The other PCBs around the scope appeared to be in good physical condition at least, dry and free from obvious corrosion. The testing of those would require the two boards in the base to be correct, as it appeared that the errors 17 and 16 were as a result of low power, mostly due to corrosion raising resistances and allowing current leakage between wires.

The replacement boards arrived, (many thanks to Stephen in Ktec Telescopes for a quick turnaround), and the installation of these was trivial enough. The smoke test was passed – nothing let out the magic smoke when power was applied! The handset powered up without issue, and the motors appeared to work perfectly on all axes at all speeds tested. I parked the scope outside on a paving stone in the lawn, and left it powered on for ~30 minutes to see if it could pick up a GPS fix. It did in fact pick up a GPS fix, one that was correct for both time and location, so I knew now that the electrics and electronics were now in fairly good condition.

I connected the serial port from one of my Dell SFF pcs to the handset, and powered on the scope. Using the HCUpdate and MCUpdate programs from the Celestron website, I was able to flash the current firmware on the handset. The motor controllers were at current levels anyway, not that surprising as the current version is unchanged since ~2011 or so.

Now on to the optics and tube. The corrosion on the tube front cell was such that the little steel screws holding on the corrector plate had bound tightly to the aluminium alloy body of the cell. Three screws were not bound and came away with a little bit of brute force and ignorance. One screw simply sheared off under the head, another two would not budge and have needed to be drilled off to allow the corrector plate to be removed for cleaning. The secondary is a Fastar-compatible and could be removed easily while I was trying all of this. It’s rather nerve-wracking to use spinning HSS steel bits that close to the corrector plate.. Eventually I managed to get the black plastic ring with the white writing off, and I could remove the corrector plate from the cell.

There was much brushing and cleaning of the cell as it was very flaky and dropping powder all of the time. I got all of the loose powder and pretty much all of the visible corrosion off, but I know I have another day of work to properly refurbish the cell. The screws and nuts holding the cell to the tube are bound solid in the aluminium cell – I managed to twist one of my screwdriver bits when trying to work it free so it was not a lack of torque at least.

The cleaning of the corrector plate was a fairly tedious process as there were significant marks in the anti-reflection coatings. Clean flowing water with a little dish soap and fingers, isopropanol and cottonwool, careful application of distilled water then to rinse. There are still some faint marks left but I expect that these are going to be pretty much invisible in general use.

The next step for me was to update the spare NexStar+ handset left over from my StarSense update that was performed on my AVX mount. Flashing it with the alt-az firmware via the Celestron CFM software meant that it was now suitable for the CPC mount. Testing the handset showed it to work exactly as was hoped, with the updated catalogues available for use, as well as the more familiar layout of the buttons and functions. Connection from the SkyFi box was also working perfectly.

Putting everything back together, cleaning all of the dust out of the base and re-lubricating the worm and wheels at the same time, I had a partial first light on a cloudy day. Using a Hubble Optics “artificial star” I could attempt a collimation across the length of Lily’s lawn. Using an 8mm eyepiece, and the working motor drives, I could get a pretty symmetrical set of in-focus diffraction rings. It really looks as though the optics are good enough to use!

First light was on a typically broken cloudy Irish evening. Two star align went okay, aligning the finderscope in the process. Given the weather conditions, double stars were the order of the day. Lots of pretty sights, Izar was cleanly split, the double-double Epsilon Lyrae was also cleanly split. Both were with very visible diffraction rings. Intra-focal and extra-focal were reasonable and will require a more comprehensive Roddier analysis in coming weeks.

EAA with the SCB-4000 camera was successful though the long focal length is a hamper. My 0.5x reducer is pretty crappy and gives teardrop aberrations halfway to the edge of view. I’ve got a 6.3 reducer in my hand that should help with the visual field, as I have a 18mm 82 degree eyepiece that should give a nice 1.15 degree FOV up from the 0.7 degree when at f/10, while still giving me an exit pupil of 0.75 with my 4.7mm. 275x is still not commonly usable in Ireland with the seeing we usually get here..

The plan is for this scope to be used by the UL Astronomy Society for member use and public outreach. I will be maintaining the scope and keeping possession of it when not actively used by the AstroSoc. It should mean more availability compared to the hoops needing jumping through to get the Physics Dept 10″ Meade LX10 out for use.

A little retro PC work and upgrades

Last summer, I used my big box of PC bits’n’bobs to build myself a few retro gaming PCs, each genre with hot hardware for its time. I wasn’t restricting myself to being time-specific with the hardware available during the time at all, I just wanted to build myself some machines that ran the software of a particular type very well.

The DOS/Win3.11 machine is a Dell desktop with a P3-600 and 64Mb of ram, a tiny ancient 2.1Gb harddisk, a Matrox G400MAx graphics card, and an Audician32 soundcard with a great wavetable board on it from (). There’s a lovely floppy emulator that uses a  USB drive with floppy disk images on it, selectable on the fly. This pc plays the old Dos games brilliantly, with great sound output and nice sharp visuals. This is for games like DukeNukem3d, Descent, Tombraider, and others from the 1990-1996 era. I haven’t done much work into the slowing down of the cpu for the likes of Wing Commander, that’s for future work. I should also do an SD-card HDD replacement, makes it a bit easier to transfer files over, and I can have multiple profiles of software as well

The Win98 machine is a self-build Tualatin 1.13 on TUSL-2 motherboard, 512Mb ram, 16gb sd card harddisk, Nvidia GeForce4 Ti4200 graphics, and a SoundBlaster Audigy sound card. This system absolutely rocks early Windows games from 1995 through e.g. 2000. The Ti4200 really does outclass the Voodoo cards at Glide gaming with the nGlide wrappers, and I can enable things like AA in most games without penalty to framerates.

The Windows XP gamer is a little Dell SFF GX620, P4 640 (3.2Ghz, 1C/2T), 2 gb ram, Nvidia Quadro 600 graphics and a Sounblaster X-fi Extreme soundcard, and a 160gb harddisk.

I also have on hand another Dell SFF box saved from scrapping, an Optiplex 960 with an E8400 core2duo and some 4gb ram, using the onboard graphics and sound.

For the XP machine, I’ve sourced a very cheap P4-D 3.4 that should just drop in, giving me a bump in speed and bringing the system to 2C/4T which should make a bit of a difference in things. Unfortunately, it has appeared that the motherboard in this little box has suffered from the bad capacitors that has plagued the hardware industry.. It fails to boot with a lot of coloured snow on the VGA output during the POST process. So, I have a handful of caps en route from eBay to fix this one.

I have also sourced a nice LGA771 Xeon X5450 to put into the LGA775 Dell motherboard. This will require a little sticker that swaps two pins, and a shaving of the physical cocket. Unfortunately the Dell bios makes a check for the Xeon dual-cpu capability and fails to post with this CPU. Looks like I will have to just build myself another box to utilise the cpu :) In the interim, I’m putting the 960 into play as the XP gaming machine.

Euro trip 2018

Here’s my little Euro road trip from early summer 2018:


  • 19 days
  • 7 countries (France, Germany, Switzerland, Liechtenstein, Austria, Italy, Slovenia)
  • 4300 km driven.
  • 17 border crossings or customs areas.
  • 5 days of kayaking.
  • 1 night slept in car.
  • 1 night slept in hotel.
  • 3 nights slept on a floor.
  • 5 nights spent under canvas.
  • €154 in tolls (approx), including Swiss and Austrian vignettes
  • About 6 fills of diesel or so.

The idea behind the trip was simple enough. That I would drive over to Slovenia with the 3 kayaks of myself, Dave, and John; with any camping gear as necessary for the stay, while I got to visit a few of my people en route.

The journey down to the ferry was uneventful. I had attempted to travel lighter than usual, while still having enough to camp and paddle in relative comfort, as well as living out of bags for the duration of the trip. I managed to get a clear view out of the back window, which turned out to be most useful for autoroute and autobahn driving! On the ferry over, we had a basic cabin – turned out to be the last one available when I booked. I got a little shock when I heard the Captain giving us an arrival time in Roscoff, as I had thought I had booked to Cherbourg. After a quick sanity check and double-check, I realised that yes I had indeed booked to Roscoff, but had booked the return via Cherbourg. The slow sprint across France was warm, pretty, and relatively uneventful as French road trips go, getting to the last unserviced Aire before Mulhouse by midnight, for a slightly uncomfortable sleep in the car for that night – and a promise to use a hotel to sleep in on the way back instead of the car – especially as there were no cheaper cabins left available on the boat on the way back so reserved seats were the order of the return ferry trip.

I dropped Lily off at her brother’s in Zurich, as well as getting to meet him for the first time in over a decade. Meeting the kittehs there as well was good! After a night there, I transferred to the nearby town where my Aunt and family live at their home near Zurich. It was good to spend some time there, as it was my first time seeing them at home in Switzerland. I got a bit of a shock at the prices of things out there, but it was an incentive to see about Swiss employment! After a visit to the Rheinfalls with the aunt and family I got back on the road to Slovenia. En route across Germany I got a quick cup of tea with Flo’s wife Vita and clarified some arrangements for my future visit there again later in the trip. So I continued my trip down to Bovec.

In Bovec, I spent two nights with Dan and gang in the little AirB’n’B studio apartment above the bar beside the little Mercator, getting the Koritnica paddled on the next day. I then transplanted to Kamp Toni for the imminent arrival of the two lads from home, who were flying to Venice and driving up the Soča river valley.

We spent 4 days of paddling the gems of the Soča river getting Serpenica 1 and 2 done a few times as well as a great run on the Koritnica, but the levels were dropping all of the time and it was a pity that the Bunker run was too low to do properly. We also got a a lovely little sightseeing trip to the Soča source and up to the top of the Vršič pass.

After the lads left to fly from Milan, I had another two nights of chilling with the Dan group again. I then drove to Flo’s place for two nights of visiting, after Flo’s recent return from his transalp cycling 400km from Austria to the Adriatic. There was an interesting and amusing trip to Ikea and a building of a shoe cabinet (kudos to the Ikea engineers for improving their furniture assembly to be almost tool-less) for the stairwell. The local church fete was pretty cool as well!

Then came a very long day of driving, from near Munich at 06.30, via an hour for food in Zurich at 09.30, and making it to our Ibis hotel in Le Mans for 19.00 before the thunderstorms hit. There were temperatures of 35.5C seen en route, and we were thankful for the aircon in the Q7. It’s not often that one can drive a full tank of fuel of that size from top to bottom with relatively normal driving..

The next day was a visit to Mont St Michel, a personal favourite of mine. Always good to see the Abbeye, though past the start of July there are definitely more and more people visiting, and it does feel a little cramped when rubbing shoulders all of the time on the narrow streets.

The ferry was late leaving, for whatever reason Irish Ferries didn’t start loading cars until after the sailing time, and we were 80 minutes late casting off, but yet arrived on time in Rosslare the next morning. Tip for those that are using reserved seats, bring a Thermarest and a light sleeping bag and you may be able to use the floor space if there are not too many people in the reserved seating area. At least the aircon works to keep that area feeling fresh..

A lovely trip, much needed relaxation, huge distances driven in comfort, some fun memories, some fond memories, and a desire to do it all again next year!

“Of” is not a verb.

Note to internet people that speak English – the word “of” is not a verb. Phrases such as “should of”, “could of”, and “must of” are all simply incorrect..

Those errors are understandable from kids or those with English as a second or third language, but it’s inexcusable from mainstream websites or media outlets.

Please proofread your writings more thoroughly.