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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.
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.
