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Separation of the Juice spacecraft from its launch vehicle was confirmed a few minutes ago. Its on the way!
Something to look forward to imaging – if it clears tonight.
Yes, I could make the code look for the TheSkyX COM process running and try to interrogate it for what the current pointing is, catching an error if need be. I have never bothered as I usually take many dozens of images of the same target and use a platesolving script that feeds the RA/Dec coordinates of the previous frame solved into an astrometry.NET instance. Upshot is that solving the first frame is slow, but the later frames solve in a second or two (depending on how many cores I use).
Worth thinking about – after I make the code rattle through the filters….
I just had a quick look at the ASTAP manual.
If I am reading it right, then ASTAP needs two FITS keywords* populated with the approximate field centre coordinates in RA/Dec and also guidance from the user (field diameter/search size) to run. So, its not doing blind solving, but the much simpler user assisted solving. Which probably explains the speed.
I’m not sure though how most of us would get the RA/Dec values into the header. Is there a command line tool or something available? I imagine you could supply a target name and the software then use Simbad or JPL Horizons online to supply the current position from your lat/long.
Does anyone know of such a tool? That would be extremely useful – and not too hard to write in Python.
Certainly, I control my telescope via TheSkyX, but I don’t like its imaging interface and so use my own CCD control software (or sometimes AstroArt) – which just takes images and does not talk to the mount. I imagine others may also be in the position of generating FITS from their camera without RA/Dec coordinates in.
*Or possibly 4, as I have seen two different definitions of keywords for RA/Dec.
Thats interesting. Glad to hear its still being developed.
Not sure a large circular aperture is always what you want for a comet, but its certainly a start.
Interesting.
As you say it brings out some nice detail in the dark bands and centre of the galaxy. Was surprised to see that in the top left part of the image some of the detail seemed to be blurred out. Would be interested to see what it did with something like the Rosette.
Ah, but is that Chlamyphoridae or Dasypodidae? These are important details.
You could also express it as the time an unladen swallow might take to fly it and then you would have to ask, european or african?
Thats inspired. Someone at the Jerusalem Post is very bored and having fun.
I’m looking forward to mass being expressed in terms of Tesla batteries or volume in terms of St Paul’s Cathedral.
The night of closest approach was largely cloudy here, besides which, I was stuck in Tesco’s car park for most the evening with a broken own car.
Did manage to get something on the 2nd though. https://britastro.org/observations/observation.php?id=20230303_232508_33211f79b6b09cc1
Ideal conditions but the 1C air temp combined with wind made my hands pretty cold by the end. I think the moonlight greatly improved on what I would have achieved with flash units.
In the spirit of full disclosure…. 🙂
Was -7.2C here last night (still -3.2C by 9:15) with a very heavy hoarfrost/fog in the early hours.
Looked in dome at 11:00 – by which time the air was registering as +5C – and found some condensation on the mirror.
Well , there goes my theory….
So, henceforth will also use a dew heater band near the secondary plus the fan. Can’t help matters having frost on the inside of the tube some nights. Don’t want to use too much power though.
The recommendations I was sent for people willing to service DSLRs, SLRs and lenses are:
This is an active list of good repairers – my friend has used a couple of them:
https://www.35mmc.com/17/07/2016/specialist-film-camera-repair-modification-companies/The two links below also get good reviews, but he has no personal experience of their work.
https://www.cameraworks-uk.com/camera-repairs-and-servicing
https://pppcameras.co.uk/aboutHowever, it must be remembered a 60mm lens may be out of their comfort zone of expertise.
He also warns that there are people out there who will do a poor job and charge you a lot, so you may prefer to watch a lot of youtube videos and then do it yourself.
Martin: Damn, had assumed the corrector lens in the Edge was up at the secondary. Sorry, bad advice on my part!
Martina: Have emailed friend. Will post here when he responds. The “forced ventilation” referred to keeping the small fan in my 300mm f/4 Newt going 24/7 – I am tempted to run it at 9V rather than 12 to spare the bearing a bit. Closing the tube or leaving open seemed to make little difference.
I did that in response to repeatedly finding condensation (water droplets and a fine dew plus a sheet of ice one night) on the mirror. Does the Edge have fans like the RASAs do?
Full dew conversation here….
https://britastro.org/forums/topic/suck-or-blow#post-615389There are camera specialist photographic companies that will attempt to dismantle lenses and clean mould off them. Given the number of elements in a DSLR lens, a telescope lens is a stroll in the park by comparison. I will ask camera enthusiast friend for a recommendation.
I noticed the inside of my 300mm F/4 starting to smell slightly of damp so went over to forced ventilation – have not had condensation on the mirror since.
One thought, I recall hearing of an SCT user inserting a tube containing packets of silica gel into the focuser (the tube had a wire mesh end so the air from the telescope got to the gel). You could also buy a couple of large packs silica gel from Amazon and put velcro tape on to them and place a fresh one on the inside of the lens cap at the end of every observing night. You then warm the spare up and store in an air tight jar so its ready for use on the next clear night.
So, is it the case that you manually select an unsaturated star on the first image, which is then automatically followed, or is it that you click on the same reference star in all images?
As I recall, you use a Paramount, so your periodic error is much smaller than with my NEQ6 – the former approach would not work well with the NEQ6 as a star can shift quite a lot at one point of the gear cycle (I lose about 15-20% of 30sec exposures – yeah, getting the OAG going sometime is on the “TO DO” list).
If you were interested I could dig out the code for automatically working out interframe offsets, so you don’t need to do a manual selection at all. The C version I lost years ago but, I still have the Fortran, VB6 and Python code knocking about. Translating to C would not be a long job. I was sort of surprised that there’s nothing obvious to use for image alignment in AstroPy.
Hi Nick,
Thanks for making the code available. Always interesting to hear how other people do things.
As you mention Ubuntu, I assume fcombine does not run under Windows.
For us heathens still using Windows, do you know if that archive can be used in a Windows WSL2 instance? Under W10 WSL2 there is a simple Linux command line environment*, but I believe W11 WSL2 instances have a full graphical interface. Have you used fcombine under that?
Finally, what language is the code in? The mention of libcfitsio kinda suggests C. Just curious as to how you work out interframe offsets and rotations – my own code for that works but isn’t elegant or especially fast.
*I run my astrometry.NET installation under it using Ubuntu installed on a Windows laptop via WSL2 – though Windows gave me a choice of which Linux.
I think I prefer a short duration dewing as that gives less time for the water droplets to absorb gases from the atmosphere and become acidic. Though, with the reduction in heavy industry over the last 50 years and diminished use of coal powered fire stations, perhaps I am being over cautious. But, realuminising mirrors ain’t cheap.
I was also disappointed that parking the telescope horizontally didn’t encourage the droplets to run off better – most of them seem to stay attached to the mirror. I assume its a surface tension effect.
Yes, I take your point regarding air temperature, but think the combination of glass being a poor thermal conductor and a fan means the surface of the mirror (not the bulk) can follow the air temperature quite closely. Thats very handwavium, but I don’t have time to make a mathematical simulation. Anyone?
I can remember many still nights with dew, but not that many windy ones – though it may be a selection effect as, before the dome, I didn’t observe on windy nights for fear of tube vibration.
I also considered a dehumidifier, but need to check the energy consumption first – a dome isn’t exactly a sealed system. A small computer fan is very low power, hence my enthusiasm.
I think the main change I need to apply now is a very fine mesh net over the secondary end of the tube to try to catch the bigger debris and discourage spiders.
Just checked. Third morning in a row without any condensation, ice or droplets on the mirror and none present when I used the telescope on the 27th. Will keep checking every morning.
A cunning plan indeed. 200 clear nights a year and dark skies, whats not to like? … Apart from the hosting charges/costs. 🙂
Grant
Thanks for all the input. I’ve been pondering this a bit.
From what has been said, its clear that cold air and a warm mirror will degrade the images, but is not a dew hazard – cooling your mirror for an hour or so at the start of the night and possibly using a gentle dew heater later, seems to sort that issue.
The question then, is what to do when the air is warm and the mirror cold?
A frequently seen example would be when someone who has been outside on a cold day wearing glasses goes into a warm house. The glasses quickly dew up. At that point many people wipe the water from the glass surface but, if you wait, the dew clears unaided as the temperature of the surface of the glass approaches that of the air and evaporation, caused by air movement, takes it away. This suggests that, for my telescope, the question is how to minimise the condensation and speed up the evaporation?
Warming the surface of the mirror by attaching heaters isn’t possible as they block the light and I am not aware of cheap tube mountable infra-red LEDs that could do the job.
Warming the back of the mirror can be done and will have an effect, but glass is a poor thermal conductor and a strap dew heater (or two) on the outside of the tube wall near the mirror may be the best we can do.
Air movement will encourage the evaporation of the dew, so a fan is also needed. If the fan is off, the air above the mirror will stagnate and the condensation will persist for hours. If the fan is on the mirror will reach equilibrium faster and, while the dew will form faster, it will also evaporate faster. So, the question becomes: what is better for the mirror short lived dew ups or long lived dew ups?
To my mind, water droplets sitting on the mirror for hours is very bad news so, when the telescope is not in active use, I will try running my dew heater on a higher setting than I normally use, plus I will run my mirror cell fan.
I hope this makes some sort of sense – please let me know if I am being exceptionally dumb as I may have missed something. I will report back here in a week or two. I wil inspect the tube every morning for a week or two.
One aside: I have used a Pulsar, a SkyShed POD and a roll off wooden roof and never opened up the roll off roof and discovered the telescope significantly dewed up. I am not entirely clear why that would be. Bigger air volume – insulated walls/ceiling/floor?
Okay, what I wrote earlier appears to have vanished… version2.
A while ago, I sought help here regarding my NEQ6/TheSkyX setup forgetting where the sky was and regularly losing connection.
Highlights of the problem included when I asked it to point at NGC1999 and it ended up pointing 30 degrees below the horizon: deep joy.
So, I was using a TPlink connection to the telescope and that proved very unreliable. I had the earths and cabling checked professionally – and that was all good – but it would regularly lose connection during a night and even took to disconnecting when our microwave cooker was turned on.
After much investigation, I discovered that one of the 4 switched mode power supplies I used was dying (they have some nasty failure modes)- it still tested as 12V and there was little AC “ripple” on the voltage, but the fault mode meant it was chucking huge amounts of noise down the mains.
So, I dumped that PSU and things improved, but were still not perfect. I got a BT Wifi extender to connect and dumped TPlink. That massively improved things. Now, its unusual to get a single disconnection event during the evening and the pointing issue went away.
However, I discovered that 4 switched mode power supplies were still causing problems. The OTA is isolated from the mount by felt pads and I found that with one of the PSUs my CCD and the tube seemed to be experiencing a floating voltage (a DC offset).
Finally, fed up with the PSUs I decided to ditch them entirely and got a cheapo 20A 13.8V linear power supply that feeds my mount, CCD, fan, dewheater(s) and minipc – having checked with manufacturers to make sure they were all okay with 13.8V, instead of 12V. That seems to have solved all the problems. No connection loses, no lose of pointing and no floating voltages. Wish I had tried it a year earlier.
The PSU is quite heavy, but it now lives in its own little enclosure together with all the wires and the collimator.
Thanks to all who helped.
