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In reply to: Suck or blow
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.
In reply to: Suck or blow
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?
In reply to: NEQ6 and TheSkyX
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.
In reply to: 2022 – how was it for you?
Observing statistics for 2022.
Gary Poyner (Birmingham)
A record year – the most observing nights from my location in Kingstanding, Birmingham since I began to record weather data in 1978. Admittedley most of the observing opportunities were with broken cloud, or mere breaks in cloud, but a record is a record.
The year seems evenly split for clear skies before and after the Solstice. Clear skies from dusk to dawn were rare with just 14 during the year, but slightly better than 2021 which recorded 11. Most of these were in the shorter Summer months.
2022 (2021 in parentheses)
Clear nights (less than 50% cloud) 41 (19)
Partially clear nights (50% or more cloud) 103 (100)
Totally cloudy nights 221.
Total observable nights 144 (119) with 74 (82) of these nights having Moonlight interference. I made observations
on 139 nights.Total hours at the telescope 303.67h (227.7h)
Best month August with 17 nights, 9 clear and 8 partially clear (April – 16)
Worst month November with 8 partially clear nights and 0 clear (December -3)Birmingham Met office gave incorrect information on cloud cover for 77 nights during 2022 (73). They remain consistantly dire.
Total visual VS observations for 2022 is 12,005 (8,201), an increase of 3,804 on 2022. CCD single measures using remote telescopes COAST, SLOOH and the AAVSO SRO-50 and MPO-61 are 2,996 (3,527), a decrease of 531 on 2021 – mainly due to a long Monsoon in the SW of the USA and prolongued down-time with COAST.
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In reply to: Christmas Meeting
The plaque in the picture gives a date c1865, but, having not seen the actual telescope it looks the finished article to me. I would therefore guess a little later – c1867. William Wray’s patent on Improvements in Achromatic Object Glasses was filed in 1866. See 920 of English Patents of Inventions, Specifications: 1866, 903-966. The witness to the September piece is J Turnbull, which I suspect is his brother-in-law, Joseph, who was also an optician.
Wray, however, was at Clifton Villas up to at least the spring of 1874, but he had changed his address to Laurel House sometime in 1875, so the telescope must date before then.The Science Museum Group website, incidentally, states the company name changed from W Wray to Wray Ltd after the merger with Aitcheson in 1908 and that the name became Wray Optical Works Ltd in 1950. However, the London Gazette shows the business name was Wray Optical Works Ltd as early as 1944.
In 1860, two years before he was elected FRAS, Wray visited Spain where he assisted James Buckingham in his observations of the 1860 solar eclipse on July 18. Also in the large group was the Astronomer Royal. Wray was also a member of the Microscopical Society.
Wray died at Laurel House on 31 December 1885 and was buried at Camden on January 4 the following year.In reply to: Composite images
Composites should always be marked as such so that it is clear that parts of the image have been processed separately and then recombined. People can then make a judgement about how “real” the image is. I wouldn’t say that a composite is a “fake” since, if done properly, it shows what would have been seen if the limitations of the telescope and camera had not been present. A good example is stacking a moving object, such as a comet, separately from the fixed stars. I agree though that this is open to abuse from people who are less than honest about how the image has been generated.
In reply to: Bob Evans
I remember meeting Bob in 2009 – he was visiting family in Cheltenham and had asked if he could borrow a telescope. Our local club (Cotswold AS) invited him to one of our observing evenings but as it was very wet he gave us a talk about supernova patrolling instead. A really nice guy.
Attached photo from the evening is a little poor, sadly (Bob is at the right).
CallumAttachments:
Topic: Piazzi’s transit telescope.
On a trip to Sicily I got to look through the actual transit telescope at Palermo National Observatory that Piazzi used to discover dwarf planet Ceres on 1st Jan 1801. An experience I wont forget!
In reply to: Bob Evans
This is sad news indeed. Bill Bryson devotes a delightful chapter to Bob Evans in his best-selling book ‘A Short History of Nearly Everything’. I bet he’s up there somewhere sharing stories with Leslie Peltier and George Alcock, the three great visual supernova hunters.
My profile pic might be of interest to some. Its me looking through the transit telescope at Palermo National Observatory that Piazzi used to discover dwarf planet Ceres on 1st Jan 1801Back in September, various news outlets reported that this year’s opposition of Jupiter was the closest since 1963 – including EarthSky [1], Scientific American [2], Sky & Telescope, CNN, etc. Last week, John Rogers asked my thoughts on this – specifically whether this was purely down to chance or due to periodic oscillations in Jupiter’s orbit. This piqued my interest to do some calculations, and I hope John won’t mind if I post my conclusions here for all to see.
In Figure 1 (attached below), I’ve plotted the Earth-Jupiter distance at every opposition between 1950 and 2300. The red points are oppositions that are closer than the 2022 opposition. By far the dominant effect is a 12-year oscillation, brought about by Jupiter’s orbit carrying it between perihelion (4.95 AU) and aphelion (5.46 AU). As you’ll see, the reports of the “closest opposition for 70 years”, whilst mathematically true, were somewhat over-hyped. There have been five other oppositions in those 70 years which were only fractionally less close.
John was curious about the impact of periodic oscillations in Jupiter’s orbit – for example, the 60-year cyclic perturbations induced by Saturn. In Figure 3, I’ve plotted Jupiter’s distance from the Sun at each perihelion between 1950 and 2300. The 60-year oscillation induced by Saturn is very apparent here, but it’s an absolutely tiny effect compared to difference between Jupiter’s perihelion and aphelion distances (0.5 AU).
So, in short, I think the closeness of the 2022 opposition is simply down to the close alignment between Jupiter’s opposition (26 Sept 2022) and perihelion (22 Jan 2023). Of course, the four-month separation is hardly a particularly close alignment. But since Jovian perihelions only come around once every 12 years, it’s quite possible to go for 70 years without getting a closer alignment than that.
The EarthSky article (link below) included this curious paragraph… “Jupiter isn’t always exactly closest to Earth on the day of its opposition. But in 2022, Jupiter’s opposition to the sun and closest approach to Earth fell on the same day. That’s because opposition took place so near in time to Jupiter’s perihelion – on January 21, 2023 – its closest point to the sun in its 12-year orbit. If it’s nearly closest to the sun, and we go between it and the sun … voilà, it’s a close opposition for us!”.
This claim was also repeated by other news outlets, and I think it’s broadly wrong.
To demonstrate this, in Figure 4 I have plotted the time interval between Jupiter reaching perigee and the moment of opposition. As you’ll see, the maximum offset is +/- 36 hours. So, Jupiter is always closest to the Earth on (or very nearly) the day of its opposition. Moreover, the offset in 2022 (shown by the red dot) – around 18 hours – is actually rather large.
To reinforce this point, in Figure 2, I’ve plotted the Earth-Jupiter distance at every *perigee* between 1950 and 2300 (equivalent to Figure 1, but for perigees rather than oppositions). If you think it looks very similar to Figure 1, you’re right. The two plots are basically identical.
So, what were EarthSky thinking? Well… if you don’t do the calculations, I think you might expect Jupiter’s perigee to be displaced some time before opposition when it is receding from the Sun, and displaced after opposition when Jupiter is moving closer to the Sun. In practice, though, the Earth’s orbital velocity is much higher than Jupiter’s, and this is rather significant in determining the displacement of perigee vs opposition. Even though, in terms of the absolute Jupiter-Earth distance, the non-circular shape of the Earth’s orbit is totally negligible, since the difference between the Earth being at perihelion vs aphelion is only 0.03 AU.
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[1] – https://earthsky.org/astronomy-essentials/jupiter-at-opposition-closest-brightest-best/
[2] – https://www.scientificamerican.com/article/see-jupiter-shine-during-its-closest-approach-to-earth-since-1963/Topic: BAA Annual General Meeting
I enjoyed attending yesterday’s meeting via YouTube and listening to David’s interesting talk on the History of the Telescope.
Thanks to all involved in running the Association for another year of good work.
AlanIn reply to: Partial solar eclipse of 2022 October 25
Dear Nick
I saw the solar disk on the youtu.be page. I download images every 2-4 minutes. I have a few things to ask you:
1) Does the image come in real time? What is the phase shift?
2) The disc image would be fully suitable for my study of the phenomenon. The only small problem is that the disc is too big, it is not entirely included in the picture.
3) If the disc remains stationary within the frame, it is not easy to establish the North-South direction. To do this, it would be necessary to bring (for example every 15-20 minutes) the disc close to the east side of the frame and NOT chase it until it reaches the west side. In this way, the alignment of the various images will make it easy to establish the North-South line on the painting itself. Can you make these breaks?This is the procedure I will follow with the camera (nikon) on my telescope:
– Entire disc in the frame;
– Periodically interrupt the tracking and take 3 or 4 images until the solar disc starts to leave the frame.
Here (L’Aquila near Rome the weather should be permissive)Thank you and good observation
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In reply to: Solar Observing – Mono to Colour
Hi Adam,
Welcome to the BAA Forum! That sounds like an excellent telescope and those are great images.
I am not sure I understand your question, but I’ll have a go at an answer.
With colourising I would be surprised if the algorithm in Astroart does anything other than assign predetermined colour values in RGB based on intensity to make it look nice, rather than anything to do with velocities. It is possible it has a template for the Sun, and varies the colour based on the location on the solar disc. The key point is the monochrome pixel values contain no data that can be converted into a velocity. I expect the temperature has nothing to do with it, other than cooler parts of the Sun such as sunspots emit less light.
All this said, if you are able to tune the H-alpha pass band in your telescope, then you might be able to sample different velocities relative to the H-alpha rest wavelength.
Best wishes,
AndyIn reply to: Antique Steinheil München Refractor
Hello Andrea, I forwarded your post about the Steinheil refractor to Bart Fried of The Antique Telescope Society. I suggest you contact him for further advice. His reply is :
Re: steinheil refractor.
Bart Fried
12/10/22 23:44
1
It does, but there’s no tripod? Also, the wood block is a home-made adapter to use it on an alt-azimuth mount. But it’s a wood tube and it was almost certainly in a cradle of some sort. If I were that fellow, I’d offer 1500 Euros and see what happens.Bart
Sic itur ad astra!
On Wed, Oct 12, 2022 at 4:13 PM denis buczynski
Bart
FYI this post came up on the BAA forum, it looks a nice example of it
type.https://britastro.org/forums/topic/antique-steinheil-muenchen-refractor
In reply to: Antique Steinheil München Refractor
Andra, hello, I am also Italian, I live in L’Aquila. That must be a mid-19th century telescope. Nothing exceptional: lactescence (spherical aberration), chromaticism, coma. If you want to show it off in your living room (after you’ve cleaned it up a bit, of course) it might do. However, if you plan to observe the sky with it, then I recommend using that money to spend a nice evening in a restaurant with a pretty girl. Maybe I’m wrong, but I remember my mother always telling me: dear son, old stuff dies in the house of fools.
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The latest Rubin Observatory newsletter advertises a colloquium for Monday 3rd October entitled: “Trailblazer: An Open Data Repository for Satellite-Streaked Images”
By Meredith Rawls and Dino Bektesevic.I am not sure whether it would be appropriate for me to post the Zoom link but the abstract reads:
An increasing population of commercial satellites is significantly impacting ground-based astronomical observations. To address this, we have built a new Trailblazer web portal, which aims to enable quantitative studies of streaks from satellites in images as the satellite population changes. Trailblazer is written in Python and Django, and allows users to upload and retrieve images affected by satellite streaks. Trailblazer stores uploaded FITS images in the cloud and saves key header information in a metadata database. Users can run queries to find satellite-streaked images by date and time, observer location, sky position, telescope, instrument, and band or filter. Images and metadata may be accessed through a RESTful API or a web query interface. To better disseminate the impact of satellite streaks on astronomy, each image also appears in a gallery for users to browse. Trailblazer is designed to be accessible to astronomers and other stakeholders to collaborate on mitigating the impact of satellite streaks, and is a cornerstone of SatHub at the new International Astronomical Union (IAU) Centre for the Protection of the Dark and Quiet Sky for Satellite Constellation Interference (CPS). Trailblazer launched in June 2022 thanks to funding from the LSSTC Kickstarter Grant Program, which enabled us to pay undergrads for software development. Check it out and upload your satellite photobombs: https://trailblazer.dirac.dev.
I’ve taken a quick look at https://trailblazer.dirac.dev/about/ and it looks as if it should become a valuable resource.
In reply to: Last night’s planetary observations
I too am passionate about planetary observation. I first saw Jupiter with its 4 satellites through a self-made telescope (the one in the attached photograph. I was totally penniless, not even money for the cinema). It was a cardboard tube with two lenses. As objective an old biconvex spectacle lens (+ 2 diopters) d30 mm, the eyepiece made with a small lens from a wire counter produced about 25X. The finder had been given to me a few days earlier. Red and blue colours were abundant, but I saw the planet as Galileo had seen it in 1610: orange luminosia star in the centre and four small stars almost aligned. I enjoyed telling everything to some classmates at school and to the Italian and literature teacher. We were studying the meaning of Don Ferrante in the novel I Promessi Sposi by A. Manzoni. It was a cold, clear winter evening. I had no gloves and at a certain point I could no longer feel my fingers. A wonderful memory that still excites me after so many years.
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In reply to: Mars dust storm alert
Here is an update. I had an email this evening from Makoto Adachi just after 18.00UT, the local time in Japan being just after 2.00 a.m. He had just come indoors from the telescope to report upon the expansion of the storm. It has definitely expanded to the south, and Aurorae Sinus is now hidden by dust.
Richard McKim
Good morning, everyone,
I would like to share with you some observations of the planets I made last night.
My observing commenced shortly after 22:30hrs and ended at 00:06hrs BST. The morning of the Autumn Equinox.
I own a Celestron C9.25 and decided that it was about time I brought it out hibernation. This is a fine telescope, as Damion Peach will testify in his review of it on his website.
I have this mounted onto a Losmandy G11 with Gemini 2. And I am currently using a Stellar Lyra 1.25-inch Star Diagonal, the optics are collimated and very clean.All observations were made at the C9.25 native F10 at 2,350mm focal length and I used a 13mm Baader Hyperion eyepiece giving a magnification of x180.
Seeing at times was ANT-II occasionally ANT-I my skies were hazy.
Jupiter.
It has been too long since I last had a look at this giant. Tonight, I was delighted to see the planet again. Through my C9.25. Jupiter was pleasing to see. The seeing was steady. But the planet was visible through a hazy sky. I think this helped to settle the seeing. On the planet. Jupiter’s two main belts were clearly visible. I thought the NEB looked brownish to my eye. Maybe someone on here can confirm this? I was able to see other features including Festoons and barges. IO was Orange in colour whilst the other three were white dots. One of the moons Ganymede was very close to the planet, and I thought it might have just come out of transit. But wasn’t certain of that.I spent a long time studying the planet and trying to familiarise myself with all the belts and zones. I must read up on observations of Jupiter before next time.
My next targets were Uranus and Neptune. I am happy to say both planets were clearly visible. Uranus appeared as a tiny orb at x180. But I wasn’t able to see anything else. Neptune again, appeared as a small disk. I wasn’t able to see any colour in Uranus or Neptune.
It made a pleasant change to use the Mk1 EB again. And the SCT.
In reply to: map of light pollution trends
Yes, Daryl, I live in Abruzzo in L’Aquila, a small mountain town at the foot of the Gran Sasso d’Italia at an altitude of 700 m. Tivoli is not far away. The 2009 earthquake destroyed L’Aquila, the (very slow) reconstruction is turning the town into a beam of lights shot everywhere and at random. Especially since LEDs consume less electricity. Even in the countryside, you need at least binoculars to spot the Pleiades clusters and Perseus, M42 and M31 can barely be discerned through a telescope, while the Lyre ring nebula has disappeared completely. Only the Sun, Moon and the shining planets remain.
In this hateful and hellish environment, I almost had to give up the telescope. For the past three years, I have been devoting myself to the study of twilight phenomena. At sunset, when the sky is clear, I take a photograph of the anti-solar sky. Then, from these photographs I determine the level of transparency of the local atmosphere.
At first I thought it was a sad fallback. Now, I have an archive indicative of air pollution and the level of ozone in the local stratosphere.
The photograph shows the beautiful view from my home, which shows the respect we have for the natural environment.Ciao
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British Astronomical Association
Supporting amateur astronomers since 1890
