Multi-telescope imaging rig

[Gina]

As promised in the monuts forum here is a description of my latest multi-scope imaging rig.  Photos to follow.

This is a permanent setup up in home-made observatorty (as most mambers here will know).  8ft square scope room with roll off roof and 7ft x 6ft warm room attached.  EQ8 mount on a solid concrete pier.

The rig comprises four scopes with MN190, Esprit 80ED Pro and two ST80s.  The MN190 is for smaller DSOs such as galaxies and smaller nebulae like M1 - the three refractors form a triple imaging rig with 400mm focal length and f5 focal ratio.  Three Atik 460EX mono CCD cameras provide image capture using Atik's Artemis Capture - three instancies on one laptop.  The MN190 also has an OAG with Lodestar X2 guide camera and currently using PHD v1.14 software.  This guiding system is used for both the MN190 imaging and the triple refractor rig.  Most of the time this works well.

To be continued - need a break ATM - still suffering from a bad cold

[iksose7]

Look forward to seeing the pics!

The only thing that puts me off having a multi rig like this (not that i could afford it!) is the balancing. How did you find balancing all that lot? Did you have to find the centre of gravity for each scope i take it and mount them according to that one at a time? The EQ8 has a fairly high payload though so maybe it wasnt as much of an issue.

I am still reluctant to start mounting my 200mm lens on my frac when i image in case it effects guiding at all! I have a feeling i am over thinking things though as i always see people with 80mms mounted on top for guiding.

Callum

[Gina]

Just popped out and taken a pic   Sunshine ATM   I'll post it shortly.

Balancing isn't a problem - just the usual procedure.  Unlock each cluctch in turn and balance.  I usually do the RA first.  This lot needs both counterbalance weights and almost all the way out.  For the Dec balancing I loosen the MN190 scope rings and slide it to get balance.  I adjust it to make it slightly camera end heavy that helps with Dec backlash.

As for your 200mm lens - if in doubt, try it - nothing to lose surely

[Gina]

Here a quick photo of the rig.  I'll try and get some other angles later.

[Gina]

One thing I consider essential for a multi-scope rig with guiding on one scope only, is to have a really solid mechanical connection between all the scopes.  I'm using the MN190 with OAG and Lodestar for guiding and mainly PHD v1.14.  I have an Esprit 80ED Pro mounted on top of the MN190 scope rings using an aluminium bar 50mm x 10mm of appropriate length.  The rings attach to a 15" ADM dovetail mounted on the EQ8.  Between the rings I have a 450mm x 250mm x 10mm aluminium plate screwed to the dovetail with M6 Allen head screws.  This takes a pair of ST80 scopes each with their own alignment plates of 200mm x 150mm x 4mm with M5 screw alignment adjusters.

The mountings for the ST80s are described in detail in my ST80 Mods for Imaging thread but I'll repeat the main points here.

[Gina]

Next we come to the mounting and alignment plates for the ST80s.  The requirements are that they must allow fine adjustment in both RA and Dec directions but very rigid once adjusted and locked down.  These plates also carry the stepper motors which drive the focussing.

The plates are pivoted at one end and adjusted at the other to give maximum leverage and fineness of adjustment.  The RA pivot is the head of the bolt that attaches the objective end of the scope running in a clearance hole in the main plate.  The Dec pivot is provided by washers on bolts at the corners.  The bolts are screwed into threaded holes in the main plate and left just slack for adjustment.  This allows the plate to pivot on the washers and clearance slots in the thinner plate allow sideways movement of the plate for RA adjustment.

At the other end of each smaller plate, an M5 screw in a threaded hole in the main plate is used to adjust the Dec alignment with th plate retained by a 3D printed plastic spring which holds the plate against the screw.

The RA adjustment is provided by an M5 threaded rod turned by a hand wheel.  A lever attached to the alignment plate carries a captive M5 nut running on the threaded rod.  Turning the hand wheel screws the nut up and down the rod and thence moving the lever and mounting plate which slides on the Dec adjust M5 screw.

Once the alignment has been adjusted, screws in the four corners of the mounting plates are screwed down to hold the settings and provide extra rigidity.  These go into threaded holes in the 10mm thick main mounting plate and do not require locking.

Hopefully all this will be clearer from the photos and diagrams following.

Photo of the two ST80 mounting plates attached to the main plate

This photo shaow one ST80 mounting together with the focussing arrangement.

This view shows the Dec adjusting screw.

Corner detail with fibre washer providing Dec pivot on M5 corner screws

Focus quadrant gear.

RA Aligment Lever

[Gina]

This is a diagram of the bracket that takes the RA threaded rod bearing and also provides the plastic spring that applies pressure to the plate for Dec adjustment.

[Gina]

Initial results with this rig as a triple imager.  Less than an hour of imaging time due to setting up time (focussing etc) and needing an early night due to a bad cold   9 Ha, 10 OIII and 7 SII all of 5m binned 2x2.  Stacked in DSS, stretched in Ps, aligned with RegiStar, then combined and further processed in PS.  Saved im PNG format.

[Stu]

Looks very good Gina, especially for just an hours data.

What is causing the red line through the brighter stars?

Stu

Sent from my iPhone using Tapatalk

[Gina]

Thanks Stu   Yes, considering it was clear all night it was disappointing to have to pack up early but better than getting pneumonia.  45m of Ha, 50m of OIII and just 35m of SII.  Just hoping that when the next clear night comes I shall be fit and healthy   I'm also hoping to go for 10m subs unbinned and capture a lot more data.  Unfortunately, I can't image the Pacman for the whole of the night due to viewing obstructions in the NW.

I think the red line is due to a reflection in the ST80 with the SII filter, producing little red spikes.

Edit...  Here's a "blow-up" of the SII stack.  Not quite spikes as I thought but a series of blobs in a line.

[Stu]

Yes, best to get yourself better first! Are you able to control the scopes from your house or do you need to be in the observatory?

Any remedy to the reflections?

Stu

Sent from my iPhone using Tapatalk

[Gina]

Yes, I can control most things from indoors but ATM I don't have the roof mororised nor switching on/off.  So I have to go outdoors to open the roof and switch things on.  If the forecast is free of rain for the whole night I can leave everything running until morning.  One day I hope to control the roof from indoors but it's not an easy job.  I quite often get everything set up in the daytime and then don't need to go out at night (weather permitting).

There are a couple of improvements I could make

1. Set up a webcam or CCTV camera to check that the rig is really pointing where I think
2. Add a bit to my Arduino focus sketch to remote focus over TeamViewer

As for reflections - take ST80 off rig and bring it indoors for inspection.  Apply black marker pen or matt black paint.

[Gina]

Managed to bring offending scope and camera indoors this morning during a sunny period between the showers.  I've found the problem - not the scope but the SII filter mounting being skew-whiff.  So multiple internal reflections from the surfaces.  Probably have shown more if it wasn't an Astrodon

[Gina]

Made a new (improved) filter holder and as near as I can tell the filter is orthogonal to the light path.  So Hopefully that will have fixed the problem.

[Gina]

Been giving some more thought to remote focussing.  ATM I have a working manual remote controlled focussing system controlling all four scopes with timing belts or gears from 28BYJ-48 12v stepper motors driven via ULN2003A stepper driver modules from 16 digital outputs on an Arduino Mega 2560. 

I have a wired remote control box containing switches to select which scope to focus and push buttons to control amount and direction of focus motor movement.  The remote control box connects to the Arduino over a stereo audio cable carrying DC voltages. The two signal lines connect to two analogue inputs on the Arduino.  Originally I had a voltage source in the remote box but changed this to just a resistive voltage divider with the source being pull up resistors from the Arduino 5v pin.  Differing resistors selected in the RC box produce different voltages at the input pins.  The sketch works out which resistor was selected and hence which switch and/or push button was used, and produces the appropriate action.

Code in the sketch removes the effect of contact bounce on the mechanical switches.  I'll post the sketch and circuit details later.

This system works well enough from the warm room but now I would like to focus from indoors via TeamViewer (as an interim to providing full blown auto focussing with tekkydave's ASCOM focuser).  A graphical interface with selector switch and buttons that I can work by clicking on would be nice but until I sort that out I'll look at sending single bytes from the keyboard over the serial terminal function of the Arduino.

[Gina]

Here's a photo of the Arduino Mega box.  USB and remote control connections on the left and 4 6way ribbon cables exit on the right in slots in the box.  These go to the driver modules which are mounted close to the telescope focusers.  The lines are 4 data and 2 power (0v and +12v).  Having the drivers near the relevant focusers enables me to tell which is which easier using the LED indicators.  Power and Ground lines (red and blcak wires) enter at the front of the box and come from the power distribution and fuse box nearby.  I'll cover that later.

[Gina]

This is the (rather crude) remote control box.  Bigger than necessary but I had it available and this was before I had a 3D printer working.  Since I didn't have a rotary switch available I used two toggle switches and the focuser selector is binary.

viz.

off  off  = 00 = F0

off  on  = 01 = F1

on  off  = 10 = F2

on  on  = 11 = F3

The push buttons drive the appropriate focuser as follows :-

Fast Backwards

10 steps Back

1 Step Back

1 Step Forwards

Fast Forwards

[Gina]

Here is the Arduino sketch.

// Updated 2014-11-23 14:30// Gina's quadruple remote focussing system using manual control// with resistor values selected by toggle switches to select // which focus stepper motor to control and push buttons to choose// 1 - Fast Backwards// 2 - 10 Steps Back// 3 - One Step Back// 4 - One Step Forwards// 5 - Fast Forwards// No button pressed represents no action (case 0).//// Stepper motors used are 28BYJ-48 12v version with ULN2003 drivers// 4 phase, 8-beat motor, geared down by a factor of 64. // Step angle is 5.625/64 degrees.//// Arduino Sketch for triple imaging refractor rig plus MN190 Mak Newt focus control// This uses an Arduino Mega 2560.////////////////////////////////////////////////////declare variables for the motor pinsint motorPin1a = 22;	// Blue   - 28BYJ48 pin 1int motorPin2a = 24;	// Pink   - 28BYJ48 pin 2int motorPin3a = 26;	// Yellow - 28BYJ48 pin 3int motorPin4a = 28;	// Orange - 28BYJ48 pin 4                        // Red    - 28BYJ48 pin 5 (power)int motorPin1b = 30;	// Blue   - 28BYJ48 pin 1int motorPin2b = 32;	// Pink   - 28BYJ48 pin 2int motorPin3b = 34;	// Yellow - 28BYJ48 pin 3int motorPin4b = 36;	// Orange - 28BYJ48 pin 4//int motorPin1c = 38;	// Blue   - 28BYJ48 pin 1int motorPin2c = 40;	// Pink   - 28BYJ48 pin 2int motorPin3c = 42;	// Yellow - 28BYJ48 pin 3int motorPin4c = 44;	// Orange - 28BYJ48 pin 4//int motorPin1d = 46;	// Blue   - 28BYJ48 pin 1int motorPin2d = 48;	// Pink   - 28BYJ48 pin 2int motorPin3d = 50;	// Yellow - 28BYJ48 pin 3int motorPin4d = 52;	// Orange - 28BYJ48 pin 4////////////////////////////int motorSpeed = 1200;  //variable to set stepper speedint count = 0;          // count of steps madeint countsperrev = 512; // number of steps per full revolutionint lookup[8] = {B01000, B01100, B00100, B00110, B00010, B00011, B00001, B01001};//////////////////////////////////int wfPin = 1;  // Focuser select switchesint controlPin = 0;  //  Input control line pinint wf =0; // which focuserint focusCount[4] = {0, 0, 0, 0};  // Separate focus count for each scopeint val = 0;  //  value of control input voltage - functionint opCode = 0;  //  corresponding operation codeint wfval = 0;  //  value of control input voltage for which focuserint stepSize[4] = {5, 5, 1, 1};  // how many motor steps correspond to one focussing step - array for different focusersboolean busy = false;  // used to provide single action buttons - wait for "up" before continuingint timeOut = 0;  // Interval counter for turning all steppers off after a no activiuty period//////////////////////////////////////////////////////////////////////////////void setup() {  //declare the motor pins as outputs  pinMode(motorPin1a, OUTPUT);  pinMode(motorPin2a, OUTPUT);  pinMode(motorPin3a, OUTPUT);  pinMode(motorPin4a, OUTPUT);  pinMode(motorPin1b, OUTPUT);  pinMode(motorPin2b, OUTPUT);  pinMode(motorPin3b, OUTPUT);  pinMode(motorPin4b, OUTPUT);  pinMode(motorPin1c, OUTPUT);  pinMode(motorPin2c, OUTPUT);  pinMode(motorPin3c, OUTPUT);  pinMode(motorPin4c, OUTPUT);  pinMode(motorPin1d, OUTPUT);  pinMode(motorPin2d, OUTPUT);  pinMode(motorPin3d, OUTPUT);  pinMode(motorPin4d, OUTPUT);  Serial.begin(9600);}////////////////////////////////////////////////////////////////////////////////set pins to ULN2003 high in sequence from 1 to 4//delay "motorSpeed" between each pin setting (to determine speed)void serialDisplay(){  Serial.print ("Focuser ");  Serial.print (wf+1);  Serial.print (" - Focus Count ");  Serial.println (focusCount[wf]);}void moveBackward(){  for (int s = 0; s < stepSize[wf]; s++) {    for(int i = 0; i < 8; i++)    {      setOutput(i);      delayMicroseconds(motorSpeed);      timeOut = 0;    }  }  focusCount[wf]--;  serialDisplay();}///////////////////////////void moveForward(){  for (int s = 0; s < stepSize[wf]; s++) {    for(int i = 7; i >= 0; i--)    {      setOutput(i);      delayMicroseconds(motorSpeed);      timeOut = 0;    }  }  focusCount[wf]++;  serialDisplay();}////////////////////////void setOutput(int out){  switch(wf) {    case 0 :  {      digitalWrite(motorPin1a, bitRead(lookup[out], 0));      digitalWrite(motorPin2a, bitRead(lookup[out], 1));      digitalWrite(motorPin3a, bitRead(lookup[out], 2));      digitalWrite(motorPin4a, bitRead(lookup[out], 3));      break;   }    case 1 :  {      digitalWrite(motorPin1b, bitRead(lookup[out], 0));      digitalWrite(motorPin2b, bitRead(lookup[out], 1));      digitalWrite(motorPin3b, bitRead(lookup[out], 2));      digitalWrite(motorPin4b, bitRead(lookup[out], 3));      break;  }    case 2 :  {      digitalWrite(motorPin1c, bitRead(lookup[out], 0));      digitalWrite(motorPin2c, bitRead(lookup[out], 1));      digitalWrite(motorPin3c, bitRead(lookup[out], 2));      digitalWrite(motorPin4c, bitRead(lookup[out], 3));      break;  }    case 3 :  {      digitalWrite(motorPin1d, bitRead(lookup[out], 0));      digitalWrite(motorPin2d, bitRead(lookup[out], 1));      digitalWrite(motorPin3d, bitRead(lookup[out], 2));      digitalWrite(motorPin4d, bitRead(lookup[out], 3));      break;  }  }}///////////////////////void moveB10() {   if (busy == false) {  // do it once then wait for button release     for (int i = 9; i >= 0; i--) {    moveBackward(); }    busy = true; }}////////////////////////////void moveB1() {    if (busy == false) {    moveBackward();    busy = true; }}//////////////////////////void moveF1() {    if (busy == false) {    moveForward();    busy = true; }}///////////////////////void loop() {  wfval = analogRead(wfPin);  // Select which focuser to control// Break points 250, 500 and 750  if (wfval < 250) {  //  allow for small variations in control line voltage by separating into bands    wf = 3;  } else if (wfval < 500) {    wf = 2;  } else if (wfval < 750) {    wf = 1;  } else {    wf = 0;  }  val = analogRead(controlPin);// Break points 102, 307, 512, 717 and 922  if (val < 102) {  //  allow for small variations in control line voltage by separating into bands    opCode = 5;  } else if (val < 307) {    opCode = 4;  } else if (val < 512) {    opCode = 3;  } else if (val < 717) {    opCode = 2;  } else if (val < 922) {    opCode = 1;  } else {    opCode = 0;  //  no button pressed  }//  switch(opCode) {    case 0 : busy = false; delay(100); checkTimeout(); break;  // clear busy flag and wait for button state to settle (switch bounce)    case 1 : moveBackward(); break;    case 2 : moveB10(); break;    case 3 : moveB1(); break;    case 4 : moveF1(); break;    case 5 : moveForward(); break;  }}void checkTimeout(){  timeOut++;   if (timeOut > 100) {    allOff();  } }void allOff() {      digitalWrite(motorPin1a, 0);      digitalWrite(motorPin2a, 0);      digitalWrite(motorPin3a, 0);      digitalWrite(motorPin4a, 0);      digitalWrite(motorPin1b, 0);      digitalWrite(motorPin2b, 0);      digitalWrite(motorPin3b, 0);      digitalWrite(motorPin4b, 0);      digitalWrite(motorPin1c, 0);      digitalWrite(motorPin2c, 0);      digitalWrite(motorPin3c, 0);      digitalWrite(motorPin4c, 0);      digitalWrite(motorPin1d, 0);      digitalWrite(motorPin2d, 0);      digitalWrite(motorPin3d, 0);      digitalWrite(motorPin4d, 0);      timeOut = 0;      Serial.println ("All Off");}

[Gina]

Nice sunny day here but very cold - heavy frost this morning which has only cleared where the sun has warmed it up.

Struggling against the flu and dosed up with Lemsip Max I tried going out to the obsy and setting up the scopes but without much success   I'll have another go later.  The alignment needs re-doing after taking the ST80 off and that scope needs coarse focussing before using the remote fine focussing.

The hand wheel came off the RA adjuster threaded rod and the focus knob has come loose.  Easy enough to fix but...  I'll have another go later - I really want to get things set up for 10 hours of cllear sky forecast for tonight.

Maybe there's something to be said for driving the alignment with stepper motors after all

[Gina]

Printed out a new, improved hand wheel and have fitted it.  Still having a problem with the focuser though but I think it may focus using the fine remote control.

Whether I shall be up to doing an imaging run tonight is in the lap of the gods   One clear night in a fortnight or so and I might not be able to manage it   AGAIN!!!!

[Gina]

Had a phone call from a friend I haven't talked to for a few years this afternoon and it really cheered me up

Anyway, that's by-the-by, got the scopes aligned and focussed as well as I can on a terrestrial object so I think I've done all I can ready for imaging.  So I may be able to image this evening - just have to see how I feel

[SnakeyJ]

Looking really nice Gina and great result with one hours data. Hopefully the new filter holder cures the reflection. Lots of promise as a photon hoover. Nice to see the 3d printing, electronics and programming coming together like this. Big salute :-)

[Gina]

Some of the gear is working and some isn't   Having problems with USB cables again and there's a bit of a problem with power plugs on the cameras.  I was about to say that guiding was working well but on going back to the PHD display I see the guiding has got the dreaded RA "walk off" symdrome

[Gina]

I think the guiding problem is due to EQMOD ASCOM disconnecting from the mount.

[Gina]

This is weird.  I didn't touch it during this graph period.