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General Discussion / European Symposium for the Protection of the Night Sky 2019
« Last post by admin on June 21, 2019, 12:46:36 pm »
You may be interested in the "European Symposium for the Protection of the Night Sky":

November 3rd through 5th, 2019, in Mulranny, County Mayo, Ireland. The symposium will immediately follow the Mayo Dark Sky Festival:
Electromagnetic Radiation Spectrum poster / Updated 20" version of poster
« Last post by admin on May 14, 2019, 02:22:46 pm »
I have made some changes to the EMR poster so that it will ship at a lower cost (now 20" wide instead of 24" wide).

The latest version is close to being sent to the printer.

Here is a compressed thumbnail image:

You can see the full poster here (1.2MB PDF).

Github link here (spectrum20 branch.

You comments are welcome.
SQM-LU / Controlling SQM-LU with an Arduino/compatible
« Last post by admin on March 24, 2019, 10:59:24 pm »
Here is an example of connecting the SQM-LU (or SQM-LU-DL) to an Arduino compatible single board computer.

The Arduino compatible computer I used was the Teensy 3.2 which is availabke for about $19.80USD.

A USB host interface is required that the SQM-LU can be plugged into. I used the USB Host Shield V2.0 mini for about $4.85USD available from here:

The USB Host shield 2.0 is documented here:

The software library is located here:

Here is the schematic (PDF):

Here is the wiring diagram:

This is the code that I used:
Code: [Select]
#include <cdcftdi.h>
#include <usbhub.h>

#include "pgmstrings.h"

// Satisfy the IDE, which needs to see the include statment in the ino too.
#ifdef dobogusinclude
#include <spi4teensy3.h>
#include <SPI.h>

class FTDIAsync : public FTDIAsyncOper
    uint8_t OnInit(FTDI *pftdi);

uint8_t FTDIAsync::OnInit(FTDI *pftdi)
    uint8_t rcode = 0;

    rcode = pftdi->SetBaudRate(115200);

    if (rcode)
        ErrorMessage<uint8_t>(PSTR("SetBaudRate"), rcode);
        return rcode;
    rcode = pftdi->SetFlowControl(FTDI_SIO_DISABLE_FLOW_CTRL);

    if (rcode)
        ErrorMessage<uint8_t>(PSTR("SetFlowControl"), rcode);

    return rcode;

USB              Usb;
//USBHub         Hub(&Usb);
FTDIAsync        FtdiAsync;
FTDI             Ftdi(&Usb, &FtdiAsync);

void setup() {
  Serial.begin( 115200 );
  #if !defined(__MIPSEL__)
    while (!Serial); // Wait for serial port to connect - used on Leonardo, Teensy and other boards with built-in USB CDC serial connection

  Serial.println("USB Host starting up...");

  if (Usb.Init() == -1)
      Serial.println("OSC did not start.");
void loop()

    if( Usb.getUsbTaskState() == USB_STATE_RUNNING ) {
        uint8_t  rcode;
        char strbuf[] = "rx\r";
        rcode = Ftdi.SndData(strlen(strbuf), (uint8_t*)strbuf);
        if (rcode){
                  ErrorMessage<uint8_t>(PSTR("SndData"), rcode);
        delay(1000); //Wait a while for SQM to respond.
        uint8_t  buf[64];
        for (uint8_t i=0; i<64; i++)
            buf[i] = 0;
        uint16_t rcvd = 64;
        rcode = Ftdi.RcvData(&rcvd, buf);
              if (rcode && rcode != hrNAK)
            ErrorMessage<uint8_t>(PSTR("Ret"), rcode);
              if (rcvd > 2)

This is the output on the Arduino serial monitor:
Code: [Select]
USB Host starting up...
r, 09.37m,0000015912Hz,0000000000c,0000000.000s, 020.6C,D
r, 09.37m,0000015909Hz,0000000000c,0000000.000s, 020.6C,D
r, 09.37m,0000015909Hz,0000000000c,0000000.000s, 020.6C,D
r, 09.37m,0000015909Hz,0000000000c,0000000.000s, 020.6C,D

Some interesting troubleshooting notes are here:

General Discussion / Calibrating camera to produce SQM results
« Last post by admin on March 08, 2019, 01:28:18 am »
Here is a paper by Zoltán KOLLÁTH, and Anita DÖMÉNY  which provided detailed steps to calibrate an all sky image from a camera to produce mag/arcsec^2, similar to SQM meters:

An example image produced by Andrew Cool from Yadlamalka Australia
General Discussion / Re: 2019 Lunar eclipse
« Last post by admin on January 25, 2019, 03:23:50 pm »
More detailed setup notes are in this PDF including sky brightness plots made with the new UDM GoTo control.
General Discussion / 2019 Lunar eclipse
« Last post by admin on January 22, 2019, 04:03:40 pm »
Here is a pretty neat SQM plot of the recent lunar eclipse recorded by Michael McKeag out in the desert east of Borrego Springs California:

Click for closeup.

This plot was manually annotated from a a UDM plot.
SQM-LU / SQMDroid for SQM-LU
« Last post by admin on August 04, 2018, 09:55:10 pm »
Thomas Hänel has written SQMDroid, an Android OS program that reads data from the SQM-LU meter. Thomas and his father Andreas presented SQMDroid and their findings at ALAN 2016 in Cluj, PDF here

The mobile Android device must be OTG (On The Go) compatible, and have an (well calibrated) orientation sensor to be used in the vector or NixNox mode.

The software is as-is, and it must be installed separately (not Google Play store), apk here.

SQMDroid has been used quite often with different Android smartphones, tablets (mainly Samsung) without problems.

A kind person has written an ASCOM driver which should work for the SQM-LU, SQM-LR, and SQM-LE. It is available from here:
Connected meters (SQM-LE/LU/LR/DL) / Re: GPS integration
« Last post by admin on May 08, 2018, 07:43:12 pm »
Unihedron sells a bracket for mounting the SQM connected metes to a car window for travelling readings:

As well, the Unihedron Device Manager software (UDM) now comes with a tool that converts the .dat (data-logging files) to .kml files used by GoogleEarth so that the following map image (with legend) can be created:

Connected meters (SQM-LE/LU/LR/DL) / Re: GPS integration
« Last post by admin on April 12, 2018, 05:38:43 pm »
I've been informed that there is a Bluetooth enabled GPS (Dual XGPS160) which also works well on a Mac with UDM.

Here is a link to that the Dual XGPS160:

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