Cathal

Site owner.

SDR fun

It’s been an interesting time recently, properly nerding out with the dabbling back into Software Defined Radio. Using a USB device, getting radio signals from around the world into the laptop, and doing interesting things from there. It’s pretty cool to be able, with the same device and hardware and antenna, to tune in the time signal on 60kHz, through getting shortwave radio stations from Botswana tuned in, to deciphering digital radio stations, to decoding the RTTY weather forecasts from the German weather service, to picking up faint FM radio stations from around the south of Ireland, to hearing Marine band transmissions, to seeing my car keyfob transmissions, to decoding and plotting airplane ADSB transmissions. All for under a hundred Euro for the hardware, and a few hours of learning.

It’s quite the rabbithole, is amateur radio stuff. Thinking about the HAM license and possible the VHF license as well, as those may come in useful for future outdoor adventures..

Scope problems..

My lovely new 20″ scope appears to need glasses. Seems as though Skywatcher didn’t make the mirror as well as they should have, and there is somewhere around one to two waves of spherical aberration present on the mirror. This is ruining the fine contrast on planets and making the scope a little frustrating to use. Currently working with the vendor to get a replacement mirror.

There is also another issue with the scope, where the primary mirror support structure has enough movement present under the change in altitude, to ensure that the scope cannot maintain collimation. My investigations so far suggest that the movement is present only in the interface between the glass and the central aluminium column that mounts the mirror to the rest of the telescope superstructure, so that’s another reason to require the replacement of the mirror as I cannot easily perform a repair on that interface, and given it’s under warranty I’m not going to touch that one.

The third problem I was having was with the quality of the GoTo computerised drive system. It turns out that one of the core components that supports the telescope “tube” had been bent out of place during a shipping accident, and was interfering with the correct operation of hte altitude portion of the drive. One removal and re-addition later, that component is now in the correct position and I’m now getting the desired target object somewhere in the eyepiece field of view after a slew.

My impressions of the scope are still good, though tempered by the (hopefully) temporary optical and mechanical issues present. There are some things I really like such as the ease of setup and takedown and the subsequent ease of storage that results from that. The drive accuracy once pointed on target means I can do lucky imaging of deepsky objects with some interesting results. The requirement for a small stepladder is not an issue for me on a lawn, but may be an issue on an apartment terrace. Now that I have the best of eyepieces and a Paracorr, I have some pretty low-power views when it is dark, but the high power views definitely have suffered with the aberrations present.

There does exists the capability for this scope to be a fantastic performer, just not yet.

Facebook stupidity continued..

Just checking my phone today, I saw that there were three Facebook applications running on my phone. A Facebook app manager, a Facebook app installer, and “Facebook services”.

I’ve never explicitly logged into Facebook on this phone, and I’ve had the app completely disabled (couldn’t uninstall due to Three having baked this piece of crap into the ROM) since taking delivery of the device two years ago.

The Facebook service app had transferred some 8gb of data since Feb 20th. At least now those apps are denied running.

Pretty piss-poor of Facebook not to take the hint on my device and install on the background. Must try and see what apps carried that malware payload onto the device.

It looks like a good time to root the device and completely remove Facebook, as well as add all Facebook domains and IPs to the null device. I’ll do that when the warranty runs out.

 

Update: – It’s the update to Android Pie that carried these pieces of crap onto the phone. Now the updates to those apps are uninstalled and the apps are disabled. Not good from Three Ireland tbh to have these baked into the ROM.

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.

http://www.cathalferris.com/pics1/500p/500p_on_the_lawn.png

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..

http://www.cathalferris.com/pics1/500p/M1_asi294.jpg

http://www.cathalferris.com/pics1/500p/ASI224_core_small.jpg

http://www.cathalferris.com/pics1/500p/M51__Stack_small.jpg

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: https://www.userbenchmark.com/UserRun/14237025

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.