JamesF

Personally I'd prefer to avoid using wifi for transferring large files around, including downloaded frames from modern astronomy cameras.  I'd always use a wired connection if I could.

In my observatory the piers are sufficiently close to the warm room that I can run HDMI and USB cables to a KVM switch from the small form-factor PCs on the piers so I can run everything that way.  If I'd not been able to do that I'd have used the wired ethernet connections to control the pier computers from a Kstars front-end running in the warm room.

James

Insulated clothing already?!  I'm still wearing shorts and t-shirts most of the day (I have preferred something longer to keep my knees warm in the evening for the last couple of weeks, I admit).  And no, I am not a postie :D

James

I never realised there was so much going on there.  Nice one :)

James

3 hours ago, randomic said:

I made a diagram which might help visualise. These points are not interacting so in the right-hand case they would drift apart indefinitely. Obviously, the oceans are gravitationally bound to the Earth so they don't just leave

Thanks.  There's still something here that isn't clear to me yet though, and I'm not sure what it is.  I may just be being dense, over-complicating things or modelling the entire thing in my head in the wrong way.

If I think about a molecule of water at, say, "average" sea level in the middle of the sea with the Moon directly above it, so it's actually sitting on a line drawn between the centre of the Moon and the centre of the Earth, there's a force on the molecule towards the centre of the Earth due to the Earth's gravity.  There's also a much, much smaller force on the molecule towards the Moon due to the Moon's gravity.  The net force is therefore always towards the Earth.  So how can that molecule of water move towards the Moon?

It's also just occurred to me to wonder if there are "atmospheric tides" as well as sea tides

James

That looks very close.  Mine didn't ever fail in that way so I'm afraid I can't offer any help at this stage.

James

2 minutes ago, randomic said:

Hypothetically, couldn't everything happen on the gpu? Since as long as the frames end up in the right order it doesn't matter in what order they're processed (assuming you don't run out of vram).

My understanding is that some jobs work well on a GPU whilst others don't, depending on the nature of the code.  I suspect most raw colour to RGB conversions can be done with a kernel for combining pixels, so I think that might work well.  It's a bit of a moot question at the moment however, as I don't currently have a suitable GPU to work with.

James

That will keep me quite for a while   Thank you, Andrew.

James

Each frame from the 462MC as it comes off the camera is going to be just over 2MB I think.  If it's converted to RGB rather than stored as raw colour then that will triple, so 67 frames would be over 400MB plus the overheads of the file format (probably not much for 67 frames).  So you're probably in the right ballpark there.

Reducing the frame size or not converting the frame to RGB would probably improve performance, and you'd not need to save so much data.

I have been wondering if the demosaic process might be something suitable for pushing off onto a GPU.  Definitely something to look at for the future.

James

11 minutes ago, randomic said:

Yep, the bulge is caused by the non-uniform gravitational field across the Earth. We see the bulge in the oceans because the Earth is (relatively) rigid and water is not. Check my posts in this thread for more information.

So you'd say that only gravity is required to explain the effect, in which case given my stationary Earth and Moon example presumably we'd get similar tidal bulges, at least for a while?

James

Double stars are a favourite, I believe.  Perhaps specific types of star too, such as carbon stars.

James

I feel the need to return to this because my brain just wouldn't let it go and I spent part of another night lying in bed trying to properly understand what's going on.  (I hope I'm not the only person who does this sort of thing.  Not that there's much I can do about it if I am.)

First I tried to decide, if the Moon and Earth were stationary relative to each other, would there be a tidal bulge and if so, how would its height compare with the tides we have in the "real world"?  I couldn't make up my mind about that as presumably they'd just crash into each other after a while.

Ignoring the effect of the Moon for a moment, I came to believe that there may be no force on the water causing it to move away from the planet.  It's just attempting to continue in a straight line at a constant speed given the inertia it has gained from the Earth's rotation (though I'm not certain about this for liquids, and perhaps particularly for polar liquids).  So presumably the height of a body of water is given by some sort of equilibrium being reached between the water continuing to move in a straight line and the force on it due to the Earth's gravity?

If that is the case then presumably the effect of the Moon is to allow that equilibrium point to move away from the surface of the Earth because it reduces the total force on the water in the direction of the centre of the planet?

It also occurred to me to wonder: do the seas and oceans "slosh towards" the land on their western edges as the Earth rotates to the east?  For example given two land masses of equal height above the centre of the Earth with a large body of water between them, would the water level be higher when measured against the land to the west than the east?

James

@Thalestris24 is in Glasgow and doesn't have a car as far as I recall, so she may be able to help.

James

And oddly enough today a 127 Mak has turned up in the classifieds.

James

36 minutes ago, Paul M said:

The belt mod kit for my NEQ6 Pro arrived today, along with the bearing removal tool.

Do let us know how you get on.  I did this mod over the summer, but I'm really not sure I've got the worms set up perfectly yet.  Unfortunately since I did the mod I've not really had sufficient time for experimentation.

James

37 minutes ago, Gfamily said:

An alternative approach is to insulate the OTA, as that also reduces the air currents. 

Indeed.  That's on my list of things to do with my C9.25 as soon as a get a bit of free time.  If I'm feeing very enthusiastic I might even do the 127 Mak.

James

14 minutes ago, Grumpy Martian said:

Might aswell take it with ice with the temperatures viewing the moon and mars tonight.lol.

Is it really still that warm in your neck of the woods?  Here it's down below 6.5C now, and it's been down to 3C a couple of times in the last week.

James

1 minute ago, johninderby said:

Or if you prefer another type pf shot glass? 🤔. 😁😁😁

Great minds John, great minds...

James

I wouldn't mind if it came with a shot glass, for those days when it's just too cloudy to be worth setting up...

I don't know if the blue tube model uses the same materials, but since I took it apart and sorted a few little niggles (it was used when I bought it) I've been quite happy with the way it performs, to the point where it has been on holiday with us quite a few times now.  It's amazing how you can find space for a HEQ5 plus tripod, counterweights and power supply (and a couple of OTAs) in the car if you tuck them away when no-one is looking :)

James

7 minutes ago, pedromreis said:

But i'm looking at the schematics... with a bit of luck I should have all the parts need, arduino, motor drivers, motors, leds, capacitors, etc... maybe in the  weekend I give it a try on breadboard and see how it goes...

If you're happy with the electronic side (as you certainly appear to be) I think it's definitely worth spending a bit of time experimenting with it.  I started my own conversion quite a long time back and then life got in the way.  I promised myself I'd get back to it when I finished building my observatory and I did in fact reach the point of mounting the motors, plugging them into the controller and having it all working very neatly on the workbench using Kstars to control the mount.  Then Covid-19 happened and work got in the way of just about everything.  Fortunately (or unfortunately, depending on how things work out) work is about to get almost completely out of the way at the end of next month, so I shall be returning to the project very soon.

James

Tom (who designed the AstroEQ controller) used to sell them ready-made.  I don't know if he still does though.

James

33 minutes ago, DaveL59 said:

Oh I thought I'd go register mine, been a bit slack with doing that so far. So as per the card in the box I went off to the website and got this:

It seems celestron.com was due to expire exactly four weeks ago.  I wonder if it did expire because someone had forgotten to renew the domain, and today it reached the end of the "grace period" for renewals.  It appears to be working for me now, but "last update" time for the domain appears to be only a couple of hours back, so they may only just have sorted it.

James

I'll happily second the idea of refurb kit.  I use it in my observatory without any problems.  I also have a refurb HP Elitebook that I bought over six years ago that is still going strong and was still in daily use by my wife for work until the end of lockdown (I was pleased enough with it that I bought another for me for use outside my office a couple of years ago).

One thing you may need to be careful about with laptops is that they have a UK keyboard layout.  I've seen one or two that have the US layout.  Personally I don't get too fussed about that as I spent a good few years in the 90's switching between US and UK keyboards every day, to the point where my brain just handled the change without me thinking about it, but it might be a pain otherwise.

James

29 minutes ago, pedromreis said:

3 - Going all DIY route I can achieve everything, if I can get everything right, including setup a pcb board to control the motors, develop firmware, drivers, etc.... (not going to happen any time soon  )

Or go DIY with a solution someone has already designed, written the software for and so on.  I'm not familiar with Onstep other than being aware that it exists, but with AstroEQ I believe you can build everything based on the documentation that already exists (there are schematics, a BOM and so on all on the website) and then use the open source firmware developed by the person who designed the board.  At that point it looks just like a Skywatcher GOTO mount and you can use it with any software that works with one.

I took a shortcut with mine and bought a ready-made controller, but added my own motors and brackets to fit the mount, used the configuration utility to set up the controller and that was pretty much it.  Kstars etc. "just worked" on Linux.  I see no obvious reason why it wouldn't on a Mac.

James

There's also this: https://www.astroeq.co.uk/tutorials.php

I've used one to allow my EQ3-2 to be controlled from a Linux laptop using KStars/Ekos/INDI.  I don't see why it should be any different if you're using a Mac.

James

Internally I'd suggest it's best to work in some format like "seconds since the epoch" (where the epoch is 1st Jan 1970 for UNIX and UNIX-like systems).  Then you only worry about daylight savings when dates are entered or displayed.  Which is kind of how daylight savings works, in a way.  It's not like the Earth's position relative to the Sun has changed this weekend, for example.  It's just what we call the time when we want to communicate it with someone else that we've altered.  Using a value such as "seconds since the epoch" also makes it easier to compare times or find the difference between them.

James