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Raspberry Pi and Astronomy


Gina

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I got a 64gb card to ensure I had plenty of space for image files.  Simple to either take them directly from the SD card or just copy them over the network after the session.

 

The RPi3 has a big advantage over the RPi2 in that its wifi is on a separate chip and not over the USB bus but even so it is possible to overload the USB bus if you start connecting a lot of things to it.  Note that the Ethernet connection is also on the USB bus so if you are using that it  will slow things down even more.

With the separate wifi I suspect that the RPi3 will prove to be far more capable than the RPi2 for this type of thing.

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41 minutes ago, Gina said:

Yes, I'm quite prepared to use two RPis or more and to capture and store on micro SD for transfer later.  You can get quite a lot of 32MB image files on a 64GB micro SD, in addition to OS and software. :)  I now have 3 RPi 3s and one RPi 2.  I'm starting a collection :D

I've always thought that local storage on the RPi for transfer "at a later date" need not actually mean much of a delay.  I've thought the setup of e.g. FTP to transfer those locally stored image files (on the RPi) back to a client could be implemented as a background process.  e.g. every 30 secs run a script/application that checks the RPi image directory and then transfers those images back to the client.  The transfer could (if need be) be throttled so that only part of the Wi-fi/network bandwidth is used.  Thus the image collection/storage on the RPi is not delayed and the transfer back to the client is not "next day" and is not disrupting more real/near-real time processes.

(I could see it pretty easy to do programming a transfer app, but I am also told that Linux has good support for throttling things as well)

Ian

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In fact, thinking further from my previous post, using multiple RPis if you use a non-root RPi for Indi image capture and cable it to the root Indi server you could then use a completely separate Wifi link (network/channel/completely isolated) back to the client for image downloading (via a background FTP/SAMBA/whatever).  i.e. root RPi A is the root Indi server talking to RPi B (image capture) through a cabled network link and maybe RPi C doing Rapid guide.  RPi B the image capture would store images on the local SD and have it's Wi-fi enabled (as well as the cable to RPi A) and the Wi-Fi talking to different Access point/different SSID/different RF channel and the client would then download the captured images directly from RPiB local storage using FTP/SAMBA/whatever.

That way you are leaving the RPi A root server Wi-fi link clear for real/near-realtime command communications.

The Indi architecture is really very flexible.

an

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I'd like to recommend FileZilla for Secure FTP downloads from the Raspberry Pi, at least with Raspbian. As long as you have SSH enabled FileZilla can connect and you can grab your files using sftp and you don't need to configure anything. I couldn't get on with Ubuntu Mate, it was slower and things not so optimised as compared to Raspbian.

https://filezilla-project.org/

 

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I found it was terribly slow to transfer several GB of images over the RPi wireless connection so I just pulled the SD card out and popped it into my laptop and that was really fast.

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On 8/24/2016 at 15:00, Gina said:

Been checking network settings.  Both router and laptop are "n" but link is running at 72mbps.  Desktop is CAT5e wired to router and has a 1Gbps speed.

600mbps for wifi N is a theoretical maximum.    As with anything based on theory, the real world doesn't work exactly like that.

As you are getting 72mpbs that does put you easily above the older "g" standard.   Which had a max of 54mpbs.

 

Imo if speed, or consistency is important, always go for a wired connection.

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Unfortunately the wired connection on a RPi is only 10/100 and it shares the USB bus so is not ideal for large data transfers either.

 

I haven't tested it myself but I read online that the RPi3 built in wifi maxes out at about 19Mbps and achieves about 12Mbps at 10m range.

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Thanks both :)

I have a 64GB micro SD card so the imaging session can proceed at 3.2GB per hour as I've been running from the ZWO ASI1600MM-Cool and a 10 hour session would occupy half of it :)  The data can download in slower time via WiFi.  I doubt I shall be running that fast on most DSOs - just the brighter ones.

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2 hours ago, D4N said:

Unfortunately the wired connection on a RPi is only 10/100 and it shares the USB bus so is not ideal for large data transfers either.

 

I haven't tested it myself but I read online that the RPi3 built in wifi maxes out at about 19Mbps and achieves about 12Mbps at 10m range.

True, but there's nothing stopping you adding a USB network adapter.  If there's only 2 USB devices active,that means you should get something like 200 Mbps when copying files from a hard drive via the usb network adapter.

I've got a PI 3, which I use for a media center.  My film collection is currently running at around 1TB, I copied all of that onto a 3TB hard drive formatted in ExFat using my Mac - cheating yes.  But it does mean that I don't care if the PI network is slow - that's only needed for updates, and movie meta data downloads.   It'll be great in my caravan, when I get a TV for it.  (If the TV isn't able to play the movie files directly off the drive that is.)

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16 minutes ago, cjdawson said:

True, but there's nothing stopping you adding a USB network adapter.  If there's only 2 USB devices active,that means you should get something like 200 Mbps when copying files from a hard drive via the usb network adapter.

I've got a PI 3, which I use for a media center.  My film collection is currently running at around 1TB, I copied all of that onto a 3TB hard drive formatted in ExFat using my Mac - cheating yes.  But it does mean that I don't care if the PI network is slow - that's only needed for updates, and movie meta data downloads.   It'll be great in my caravan, when I get a TV for it.  (If the TV isn't able to play the movie files directly off the drive that is.)

Which software are you using for the media centre, out of interest?  I've been toying with the idea of using RPi3 as a MythTV front end, though as it would just be a front end (I have a back end in the cellar) network speed is an issue.

James

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Unfortunately the images are stored on the SD card so this also causes a bottleneck, the SD card slot on the RPi is quite limiting especially as it gets used for so much.  I've considered storing to a USB drive instead but this would be problematic as I will be using a camera on it that will already be pushing the USB limits and the ability of the RPi to provide power to devices.  I do have USB power connectors though so that can be fixed.

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1 hour ago, JamesF said:

Which software are you using for the media centre, out of interest?  I've been toying with the idea of using RPi3 as a MythTV front end, though as it would just be a front end (I have a back end in the cellar) network speed is an issue.

James

At the risk of hijacking the thread.  It's OSMC that I've got installed on my PI.    What I have is pretty much a default install, then I added added the hard drive.  The Hard drive is in a USB caddy.  If I got my act together I could power the whole thing from 12V.   But I'm not in a hurry to do that, as SGL is my first major outing and I'll have an electric hook up.  Can run it from mains :)

I've got a Hama media remote which I can use to select the film that I want to watch.

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