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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.
Down here in Salisbury, things looked hopeful. There was thin haze being illuminated by a bright Moon. But about 25mins before launch a band of cloud rose in the west – I was looking at a bearing of about 240degs and 4 degs elevation – and after that there were only faint thinnings through which I glimpsed stars. I reviewed the images and didn’t see any star-like source move right to left during those few minutes. So, no ascent to (nearly) orbit imagery from me.
It may have been 1.2C on the hill, but it was fun – I could hear foxes and owls in the distance.
Not sure it is embarrassing. According to an interview on the BEEB, the risk assessment indicated a 27% chance of failure. And, as the saying goes, “sewage happens”.
It literally is rocket science. Its hard and we have become blase.
I will certainly have another go at the next launch.
Using the graph Nick kindly provided of apparent elevation versus range, plus the ground path and flight profile I got some approx values.
If I am viewing the map right, the lat and lon lines are at 2 deg spacing, I get a position for the launcher as 37N 15.5W at T+480s and 32.5N 16.5W at engine cutout.
From Salisbury it looks like 200-300s after launch gives an altitude just under 4 degrees – rubbish, but just doable*from a high location on a good night, if the engine burn is very bright (who knows?). Okay, its a chance in a million.
From Lands End it is better – but still not great – at ~9 degs elevation at ignition +200s. Should be brighter though.
For Tenerife – I know someone out there currently. I get:
T+480s ~5 degs elevation at 160km alt, 970km distant with 0 deg bearing.
T+570s ~16degs elevation at 160km alt, 465km distant with 1 deg bearing.For La Palma – for Paul
T+480 ~5 degs elevation at 160km alt, 950km distant with 13deg bearing.
T+570 ~18degs elevation at 160km alt, 442km distant with 17deg bearing.I think I got that right… but some of the measurements have an element of handwavium.
Thanks again to Nick for the visibility map. I shall hang on to a copy of that.
The article on the Beeb suggests there is a live stream….
https://www.youtube.com/watch?v=5Co18HcyqHk
I will make sure I am ready from 22:30 onward.
Has anyone any feel for how high it would be above the horizon?
Weather looks decidedly iffy here.
Sounds fun to me. Now, we just need a launch time…. 2 hours is a long time to just hang about. Suddenly a meteor camera looks very useful.
Oh, I think I missed something there….
You have to ask them to give you a copy of your data as FITS? Theres no SD card or something where all your session data is saved that is accessible to you? Does this mean you don’t have anything else other than a jpg/png they serve up to you live? I’m surprised at what you said but, clearly, they have found a market.
Just to be clear, as I have never used one, what is the bit depth on the png provided? I think that both 8 and 16 bit are legal png formats, though some software doesn’t like 16 bit pngs or TIFFs.
If the png is 8 bit (or even 3x 8bit) then they have rather constrained you to the Citizen Science route, as that makes it harder to do any on your own. But, I don’t know the png file format well enough to judge if its metadata content could be used to populate a FITS header.
The hint is in the name. The vast majority of deep sky images are exactly that, pretty pictures. Theres no scientific rationale for taking them and no need for the person doing so to worry about gamma stretching or sharpening – its about showing the structures and elegance in an object in a tasteful and appealing way. Look at how many people return to an object (such as M42 or M16) every few years because improved skills, location or instrument mean they will be able to pick out more detail or create an image more eye catching. The target itself has not changed. It is a quest to get the maximum performance from the kit you can afford: we all know that if we had a PlaneWave 24″ in Chile, an Andor camera and unlimited time on it we could take better pictures, but most of us cannot afford one, so we strive to do the best we can.
With planets its also about detecting features (dust storm, cloud feature, polar cap) but, they change which makes life much more interesting.
Its the change aspect that makes variable stars, the Sun, aurora, meteors and comets interesting too. Its why I spend most my nights chasing variable nebulae.
I have seen people post pics in the BAA Gallery that were clearly composites and they have not mentioned it. That I must admit to disliking.
Yeah, I read some of the AAVSO pages on this. Sounds like they are not in a hurry to provide FITS files – which is kind of weird given how its a trivial bit of coding. A doddle in C and trivial in Python.
Sounded like the way the Citizen Science is done is taking observations and sending them to someone else who does the data reduction… Sounds a bit dull to me. Data reduction is what cloudy nights are for.
Some mention of the code being open sources and then of release of an API, but nothing yet – and promises are cheap of course.
Thanks for the headsup. Your observation really does suggest we all need to keep a close eye on it in the months ahead.
Hi David,
I think that V shape and the right hand wing (on your image) feature have been faintly visible on some unfiltered images since the summer.
Such as here:
https://britastro.org/observations/observation.php?id=20221129_230438_ac6a218c4ac94ed0
and
https://britastro.org/observations/observation.php?id=20221129_230930_656c96e63f3df518Was it absent in your similarly exposed Rc filtered images from earlier in the year? The nebula is heavily reddened, so you might well see changes before those of us working unfiltered noticed them.
Do you still measure the nebulosity brightness at all? What does that curve say?
Would be nice for this or McNeil’s to reappear at last. Looked at Thomme’s last night and can’t see much change since I started looking at it and McNeil’s is absent with V1647 Orionis in the 19.5-20.5 mag range when skies are clear enough to detect it.
Happy Solstice!
Grant
From Wiltshire, at 0630 the Sun is about 8.3 degrees below the horizon. TheSkyX still shows 1st and 2nd mag stars visible at that time, but I don’t know how accurate that is.
I think this guarantees cloudy nights for a week…
You probably need to add dancers, a 120bpm backing track, some dry ice, lasers, a conspiracy theory and someone being humiliated to keep social media fans tuned in.
