Brutha

After browsing past this the other day, I was having a think and came up with the following (thought!) experiment (which if I remember correctly is based on some early experiments done to measure the speed of light).

Let's say we have a couple of disks connected via a rod, and they each have a small notch in the edge, separated by a small angle.

We point the apparatus at a star; at a certain rotation speed the star will appear (when the flight time of the photon between the two discs is matched by the time to rotate through the angle between the notches).

Would this be a valid measurement of the "one way speed of light"? Or is there some fundamental reason in the physics why this might also be illusory? (I am not a physicist!).

I'm not sure this is actually doable btw, if my maths is right an angle difference of 0.01 degrees would need the disks to be 20m apart and rotating at 500hz!

Thanks all, some good info there!

One thing I am wondering about is whether the fact I am quite a long way north is a problem. For me, the sun at noon will vary between about 10 degrees altitude and 55 degrees, with it getting above 40 only for about 5 months of the year - is that an issue for seeing do you think?

I saw the 3d printed Sol'ex DIY spectroheliograph on another post, and was quite tempted by the idea of changing direction and giving that a go, as it has the potential to do some really interesting imaging.... but then I found the kit stuff you need is 485 euros and it's all out of stock at the moment anyway (if they'll even ship to UK!).

Cheers

Brutha

Hi All,

I have Celestron 8SE which I'm very happy with for general night viewing. I don't plan any astrophotography with it (maybe another attempt at planetary once Jupiter or Saturn are higher in the sky again).

Given that there is not going to be any nighttime viewing for a good few months now, I've been toying with the idea of solar, using something like the Daystar Quark.

Of course, that won't work with the 8SE, so I will need a refractor. I can probably justify the cost to myself if the scope will have multiple uses. 

Are there any scopes that might meet all the following? I appreciate these might be contradictory but not sure!

• Good with the Daystar Quark eyepiece for solar
• Good for nighttime viewing, with a wider field of view than my 8SE - e.g. fit most/all of Andromeda galaxy in FOV.
• Good/reasonable for astrophotography if I get into it.
• Ideally fairly small

Any thoughts appreciated!

Cheers

Brutha

Hi All,

Over the past weeks I've completed the free Data-driven Astronomy course on Coursera, and enjoyed it a lot, so thought I'd post some info about it here for those who might be interested.

It's more of a programming / data analysis course than it is an astronomy course (and I knew this starting out), but there is still a fair bit of interesting content on pulsars, exoplanets, types of galaxies and so on.

It illustrates what seems to be the big problem in modern Astronomy; previously it was the case that the problem was getting the data. But now we almost have too much of the stuff, and the problem is finding clever ways to process it and get useful information about the universe.

So, it alternates between videos, graded quizzes, and tutorials / challenges on https://groklearning.com where you learn to code mainly in Python using various libraries like Astropy for astronomical calculations and Numpy for numerical / scientific stuff. And a bit of SQL thrown in along the way. 

You use data from various sources including Kepler for exo-planets and the Sloan Digital Sky Survey, and build up to using the scikit-learn machine learning library for predicting galaxy red-shifts and types by the end of the course.

Although they start from the absolute basics in Python at the beginning of the course, if you have never done programming in any language before, you might find the learning curve a bit too steep. But you'll never be typing in huge programs - most are only 10 lines or so in the end, with one or two a little longer.

At various points, you'll need to use google to figure out the approach to a problem or look for the appropriate function in a library etc. Funnily enough I found the first week the hardest, because you are doing basic algorithms in Python; in later weeks it is easier even though the problems are more complex, since the heavy lifting is done by the various libraries.

Cheers

Brutha

Hi Geoff, welcome from another Western Isles resident

I did something similar with Messier objects last year and intend to continue this year. Although I think we get a few less clear nights than most people, the dark skies do make up for it!

Cheers,

Brutha

Hi All,

I remember seeing some discussions on various forums about the various tracking options on telescopes, and there was some debate about which mode you should use for solar system objects.

I've been wanting to have a play with Jupyter notebooks and Astropy for a while and this seemed a nice opportunity! So, I set myself a little exercise to find out....

I've assumed that for each tracking option, the telescope only tracks in RA, and for sidereal tracking it just keeps the telescope pointed at the same RA/DEC point. For solar and lunar, I've assumed they just increase RA tracking to move at just under a degree a day, and for lunar at around 13 degrees a day.

Next is to work out how much the planets are moving in RA per day for 2021 and 2022, something you can do easily with Astropy.

Then I work out how many hours it would take in each tracking mode for the object to move to the edge of the field of view - I've used my C8SE and an 8mm eyepiece as the model. Of course, this all assumes perfect alignment and tracking

The results are quite interesting (assuming I've done the calculations right, which is by no means guaranteed!): for Mars, it is mostly solar tracking that wins out over the two years - the green line shows "time in view" for solar, red is normal star tracking. Lunar as expected doesn't do anything:

Again for Venus, solar tracking is better (which makes sense, it being closer to the sun) :

However, once you get to Jupiter and further out, sidereal mode takes over:

Anyway, this only shows max possible with perfect alignment and tracking, so my guess is that things are closer in practice!

If anyone is interested, here's the Jupyter notebook:

Solar system tracking speeds.ipynb

Cheers

Brutha 

Thanks! Yes, for now the requirements are not serious, it will have my C8SE on top, being used visually. But part of the idea of the pier is that it would still be useful in case I upgrade to something bigger later.

So, 200mm it is!

Thanks! I said that was the last question, but now I realise I lied!

How deep do you think I need to set the bolts? I've seen one thread on here where they drilled 200mm deep holes, but I am wondering if that is necessary.

Thanks all! 

Last question then: in the pier installation instructions, it mentions to drill a hole with a 12mm masonry drill.

Since the threaded bar will be M12, that presumably means there will be very little space around the bar. The picture shows some space between the bar and the hole, filled with resin.

Should I leave any gap, i.e. go up to a 14mm drill bit or so?

Cheers

Brutha

18 hours ago, pete_l said:

There are loads of similar products. Widely available in hardware shops or online.

Yes, I thought there would be - but I just seem to finding mechanically fixed drop in anchors with interior threading, and threaded rods that can be chemically fixed.

There don't seem any chemically fixed drop in anchors though - just the ones in the original thread that I can find. But it's entirely possible that I am looking at them on the page and simply not understanding what I am looking at!

1 hour ago, StevieDvd said:

Not sure of your location, you may want to give us a clue as we have many international members. But in UK the chemical bolts sets are sold in B&Q and Wickes, and Screwfix & Toolstation will do the parts if not an actual prepared set.

 

Thanks - yes, Western Isles of Scotland, we're a bit short of B&Q megastores round here

But it should be possible to order what I need fairly easily - the trick is identifying just what I need!

18 hours ago, Kimboman said:

Hi I would recommend using threaded studs and chemical anchor in a tube that fits into a standard mastic gun(applicator) these are available from Tool station 

drill the relevant sized hole for the chosen stud size, ensure to remove all dust and debris from the hole just follow instructions.

I have used these actors up to 30mm die to hold down machine tools with no problems

Yes, I think on reflection this is probably the route to go!

Hi All,

Just preparing to get my concrete slab poured for my Altair astro pier. 

After a bit of reflection, have decided not the use the j-bolts that I ordered with the pier, since the shape of the slab is a little unusual, and I don't want to be juggling too many things when pouring the concrete. So, I'll pour the slab, get the surface nice and level, then we'll drill it later.

I quite like the idea of using the chemfix chembolts as suggested in a previous thread - since then I can just put M12 bolts down through the base of the pier, and not have much sticking up.

However due to my location, they want a truly ludicrous amount for delivery (i.e. 4 times the cost of the bolts!!!), so that's not an option, and they don't seem to be sold anywhere apart from the link in the above thread.

Has anyone used simple drop in anchors for this purpose? Something like these?

Cheers

Brutha

2 hours ago, Alan White said:

A few nights ago I used a scope on a 6ft or so high pier, it was mounting a large refractor for visual use.

Thanks Alan, in fact this should perhaps have been more obvious for me, having seen the rather impressive “Fraunhofer Refractor” in the Deutsches Museum in Munich (the one that was used to discover Neptune): https://www.atlasobscura.com/places/deutsches-museum-refractor-telescope-neptune

On 16/06/2021 at 11:34, jacko61 said:

I have the altair astro pier and have around 12" of concrete above floor level in my shed to get the eyepiece to where I'm comfortable. 

Thanks (sorry for delay, hadn't been back to this site for a while!).

Interesting you have it so high though! Is it used mainly for astrophotography, or do you also do visual astronomy?

And to add a further question, as I have been doing lots of reading today! 

I am wondering whether paving slabs is a good idea around the scope, due to being slippy in cold weather etc. I am wondering if gravel might be a better bet - any thoughts?

Hi All,

So, rather than go down the home made pier route, in the end I decided to order an Altair pier, which has now arrived, and looks to be a cracking bit of kit!

It will go in the garden (just open air, no observatory etc), and for starters I will be using my Celestron 8SE on it, with the standard alt/az mount. I will need to create a custom adapter plate, but that's in hand and shouldn't be too tricky.

For now, the reason for the pier is mainly to avoid the faff of carrying the scope plus tripod in and out of the house when I want to use it, with a side benefit of a bit less vibration when using the scope. But in the future, I may well get a GEM mount of some form for astrophotography.

The area is currently just grass, so I think I will put some paving slabs down which will surround a central 60cm x 60cm x 60cm concrete block sunk in the ground containing the bolts.

But I'm going back and forth a bit about the height; if I set it according to the usual height it would be at on the tripod, the concrete block would need to be 5cm or so above the level of the surrounding paving. But most pictures I see of the same pier seem to have the base of the pier lower than the surrounding area if anything.

Is this just due to the additional height of GEM mounts? Any advice on where to start is welcome!

Cheers

Brutha

My understanding is that Maksutovs tend to have a longer focal length, so are better for planets and lunar viewing, but typically not so good for fainter deep sky objects.

If you scroll down a bit, they add right at the bottom that it is an animation showing the current position of the probe, not an actual live feed... a little bit cheeky I think!

Hi All, 

I'm looking for a simple solution that would let me extend my wifi up into the garden - this would be so I can connect a Raspberry Pi with Astroberry to my home network, rather than needing to run the Pi in hotspot mode.

Ideally, I was thinking of something simple - one of the wifi extender things that plug into a mains socket would be perfect I think. However, it would need to go through a wall and then up to maybe 50 feet max to the actual device.

Has anyone got any recommendations? Or am I being somewhat optimistic?

Thanks!

Brutha

On 31/01/2021 at 11:41, wulfrun said:

And even better, "vision of the future". Now they'd be very handy for any race-going punter! I see they also have the "exit of the student: 18mm", chinglish at its best 🙂

Hehe, of course, student = pupil, took me a while to work that out!

I know this is an old thread, but it is amusing that amongst such things as outdoor camping and formula 1 races that the Amazon description claims these are particularly suitable for is “blurred vision”.

https://www.amazon.com/Binoculars-30-260X160-Professional-Telescope-Stargazing/dp/B07SRZNNLF

On 18/01/2021 at 00:04, Astrofriend said:

How many of you who read this use the FreeCAD software ?

I do - I find it very powerful once you get used to it! And you are not vulnerable to a company removing functionality, as recently happened to Fusion360

On 21/01/2021 at 17:02, malc-c said:

It's about the same physical size, but that is where the similarity ends... Dual core 32bit ARM processor running at 133Mhz.... compared to the Nano's 20mHz 8bit AVR.... no comparison.  But does it directly support the Arduino C++ language, I don't think it does.

It does support C++ (although I guess not the Arduino special stuff). Interestingly, arduino are also building a board themselves using the new chip. Given it will have WiFi, I guess it will be a fair bit more expensive:

https://blog.arduino.cc/2021/01/20/welcome-raspberry-pi-to-the-world-of-microcontrollers/

15 hours ago, skyhog said:

Many years ago I always saw M42 with a greenish hue. It was quite unmistakable to be honest. I remember looking at it with my 8 inch SCT for the first time and that was the big wow moment. These days I don't see a hint of colour. That flashlight trick sounds interesting, I'll have a go at that!!! 

I was looking at Orion the other night through my 8SE, and it was quite clearly a greenish hue. I was reading this thread and wondering if I had imagined it, but glad to hear I wasn’t!