saac

@psy1280 is it possible to select a generic ascom moun (assuming the AVX is ascom compliant). I'm only grasping at straws. Hopefully ZWO will respond to the bug report - keep chasing them because this is really spoiling the user experience of an otherwise excellent bit of astro kit. 

Jim 

Most likely they are just staying warm - sign of the times maybe!

Jim 

ps that looks a good selection - did you borrow anything?

It's too far North lol. Let me guess you south of the Watford Gap?   If it helps I know the feeling Glasgow is way to far South for my liking. As for midges they fly South for the winter   

Jim 

Latest bid for Dark Sky status, island of Rum is in the process of placing an application for Dark Sky Island status. These accreditations are obviously pitched at bringing visitors to the area but at the same time they do at least publicise the issues concerning light pollution.  I've spent some time on Rum, mainly hill walking, nice place and would be a really good astro observation site for the dedicated traveller.  If you feel so motivated there is a go fund page to support the application.

Fundraiser by Alex Mumford : Protecting the Dark Skies on the Isle of Rum (gofundme.com)

Jim 

I think (may be wrong) that the Voyager team converted data to produce the "sound" of interstellar space when they left the solar system.  Jupiter and Saturn probes have also produced some mesmerising audio interpretations.  This really is a fascinating interpretation and definitely widening access. I wasn't aware of Wanda Díaz-Merced; listening to the podcast now .  Such a wonderful concept, thanks for the heads up. 

Jim 

My name is James and I use GOTO.  

Jim 

On 25/02/2023 at 13:34, Louis D said:

  Almost no professional astronomers own their own equipment these days.

That's me then still paying off credit card  

Jim 

There may be some info on the ASiAir facebook forum, might be worth a look. ZWO seem to be making a right mess with these updates recently. 

Which version have you updated to, if I have interpreted it correctly this is the latest v2.1 - 10.74

https://www.facebook.com/groups/ASIAIR/permalink/2511344792362062?locale=en_GB

Jim 

2 minutes ago, andrew s said:

The isotropy of the speed of light is built into SR through the Einstein synchronisation procedure. It's not the only possible procedure and you can develop a nonstandard relativity based on them. However,  while the equations are more complex you get the same predictions as SR.

As the paper I linked to show the measured limits of any anisotropy are very tight.

In my view and that of the SI board it's a done deal and the isotropy is built into the SI standards.

Regards Andrew 

I suppose that is reflected (no pun indented) in the classic representation of Einstein's though experiment with his light clock - it uses a return path. So is he in effect saying in his postulate the return speed of light is fixed, hence built in.  I must admit before this thread I was never even aware of the notion that it was a legitimate question. Then again, the comment on birefringence  should have made the possibility less strange a question.  

Jim 

I found some homework for tonight.

[2012.12037] The One-Way Speed of Light and the Milne Universe (arxiv.org)

Jim 

3 hours ago, iantaylor2uk said:

I don't know what you think the physical basis is for why the speed of light would differ in direction.

If you look at Maxwell's equations, there is a single speed c, predicted for electromagnetic waves, and as far as I'm aware the c that appears in those equations does not depend on direction, and electromagnetism agrees well with experiment. 

In addition, there have been many published papers where general relativity has been applied to pairs of spinning black holes, particularly for black hole collisions, where as I understand it the simulations agree well with the measured data. 

I think if the speed of light were different on the two separate paths application of GR to spinning systems would have shown up as discrepancies with experiment. 

That was my initial thoughts Ian but I think what the issue is with that is that it represents a "derived" value, assumption are in effect baked in. The question arises from the possibility that space may not be isotropic in nature with respect to the passage of light.  So the challenge for the experimentalist is to find a way to verify the one way light path and it seems impossible. 

Jim 

1 hour ago, andrew s said:

You can have an eletrodynamics with an anisotropic speed of light but the equations are much more complex. 

The consensus is that you can measure the anisotropy but not the one way speed.

This Wiki article is a good starting point 

https://en.m.wikipedia.org/wiki/One-way_speed_of_light

Regards Andrew 

PS This paper https://arxiv.org/abs/1011.1318  reviews the isotropy of the speed of light see table 5. Current experiments show it is isotropic at the 1 in 10^-10 level.

Relativity effects of time dilation, length contraction etc are predicated on Einstein's postulates (Galilean invariance holding true and speed of light being fixed).  If the speed of light was dependant upon direction would that not show in our measurements of relativity effects?  Or is the magnitude of the speed less important than light being compelled to travel at its maximum speed whatever that would be in either direction?  

Jim 

4 hours ago, andrew s said:

To honour the original I would propose it has to be a man made mechanical device that operates (I.e. has moving parts) continuously without any energy input.

Regards Andrew 

PS this seems close https://en.m.wikipedia.org/wiki/Beverly_Clock

Not been wound since 1864. However  it uses changes in air temperature and pressure as energy input so does not really count.

I wasn't aware of that one, amazing, must be very finely balanced and excellent bearings. I wonder if the night shift cleaner is winding it each night  

Jim 

8 hours ago, Moonshed said:

I wonder if anyone knows what has come the closest to being perpetual motion? (in the real world not theory).

Oh great question. I vaguely recall some sort of flywheel device that baffled investigators for some time but I might be getting that mixed up with gyroscopes proporting to be used to generate lift. Pretty sure now all such proposals are blocked by patent office at application stage - 2nd law thermodynamics violation. Not really sure what the definition is any way, for example does it qualify if it cannot drive an external load, ie it has to do work on the external environment.

Jim

3 minutes ago, andrew s said:

Fun isn't it 

Regards Andrew 

 

My maths teacher used to say that, and yes it is, but also frustrating in equal measure    It's like one of those perpetual motion proposals, everything looks plausible at first, but it doesn't stay that way for long. 

Jim 

33 minutes ago, Deadlake said:

A one way journey, no mirror, no clock synchronisation. 
 

The is called a light ring around a black hole, I leave the expert to it

 

Lol and that's is the rub, a modern take on "use a sky hook"   Nearest black hole is how far away?  Gravitational distortion will do what to any instrument package?  Trust an engineer to think about the practicalities. Hey, maybe we can make one in the lab.  

Not to mention what the distorted gravitational field may mean/influence any anisotropic properties of the local space? How would you know what affect has influenced what?

Cool video, these things really are fascinating -  thanks for link. 

Jim

2 hours ago, Deadlake said:

I’ve not read the whole post, however ways of measuring the velocity of light are 

1) Reflection, where a mirror is used to return the light.

2) Synchronised clocks reporting the velocity of light between two points?

And the aim is to measure the velocity of light one way?

Well one way (no pun) of measuring the one way velocity is to have light bend back on itself, just need a black hole to bend time/space and light will loop around and come back. The astrophysics are using this technique to find out new physics around the photon rings around back holes….

Isn't that the problem though, to contrive to measure a one way flight path - no reflected journey, no traveling back on itself.  Synchronised clocks - how do you tell the 2nd clock to start?  That is the problem.  Black holes , I can see a few problems there    It sure is a frustrating problem conceiving how this could be done for sure. 

Jim 

Hi Ash. If you haven't already done this I would recommend downloading a planetarium programme such as Stellarium or an app like Sky Safari (for tablet).  Once you get either running set your home location as the latitude and longitude of your remote site. Once you have done this the programme will show you the night sky hour by hour and you can see what objects are available for that night's session. Sky Safari will give you a suggested viewing list each night.  You might want to start by going for for some of the easier targets such as Andromeda, M45 and M42.  Once you get you han dit with these you could try chasing down some of the star clusters.  The BBC Sky at Night magazine publishes a monthly viewing guide, that may provide some inspiration as well. 

https://stellarium.org/

https://skysafariastronomy.com/

Jim 

I feel your pain, if it's not clouds it's light pollution,  

Jim 

Remember a pier would only really be needed if the intention is to do astrophotography. Visual would be fine with just a tripod. 

Jim

On 23/02/2023 at 19:31, bosun21 said:

Head north to Scotland!

Shhhhhhh  

Jim 

On 23/02/2023 at 07:57, Grump Martian said:

https://www.bbc.co.uk/news/uk-wales-64731286

A BBC link to a story about a dark sky site in Wales. Great, but not sure that the sky will be clear when I visit,lol.

The night skies in my area in South Hertfordshire are disgusting. Light pollution have rendered them very poor.

Indeed, what we need is not so much a Dark Sky Site/Sanctuary but a Clear Sky Sanctuary, now that would be good. 

Jim 

You can thank them via a pm even if the advert is closed

Jim 

13 minutes ago, Froeng said:

To compare this thread's subject to the actual "Holy Grail", ie the humble carpenter's cup, wouldn't we be talking about something like:

a) Galileo's original telescope that he used

b) Newton's original "newtonian" reflector

or c)   the Hooker telescope Edwin Hubble used at his time.

I admit non of the above people were Jesus, but then we are comparing ordinary telescope to holy cups...?

If I had either Galileo's or Netwon's original scope, they would be upload straight away to buy and sell.  Then I would buy a RASA 8

Jim 

@ollypenrice 's recent photographs taken with a RASA 8, I think, are truly stunning and show what a capable imaging system this is. So I think I am going to start apportioning off some of my retirement funds for a RASA 8 or 11 

Jim