Any feed-back on remote control for tilt-tuned filters ?

[christian viladrich]

Hello,

I am looking for any feed back on possible systems for operating remotely a tilt-tuned Ha filter. In other words, any way to implement a system / motor allowing rotation of tilt-tuned etalons (like Lunt, Solar Spectrum, Coronado).

Ideally, this would be to operate the system from the computer, but having a control box controling some kind of actuators and mechanism woul be interesting too.

Thanks for your feed back !

Christian

[MalVeauX]

Hi Christian,

I don't have one working at the moment, but essentially if you just match a plastic gear wheel to the tilt wheel you can do this with a basic DC step motor that has 1 step intervals or larger. I use Rigel systems nFocus step motors for these things, especially for focusers because it has a clutch system for when I want to manually operate it. Full ASCOM/PC control and also a hand controller if wanted. The clutch was my selling point because sometimes I want to manually adjust things. That's the easy part. The difficult part is mounting it securely and without blocking the tilt pathway of the etalon. You would need a sturdy bracket to hold the motor in place and keeping contact on the tilt wheel and of course a means to keep the bracket on the etalon/scope. I think a 3D printed solution would work if you design something.

Very best,

[pupak]

Remote control of the tilt is not a complicated matter, provided that you give up manual tilt with a wheel. Keeping the wheel is much more complicated.

[rsfoto]

Hello,

I am looking for any feed back on possible systems for operating remotely a tilt-tuned Ha filter. In other words, any way to implement a system / motor allowing rotation of tilt-tuned etalons (like Lunt, Solar Spectrum, Coronado).

Ideally, this would be to operate the system from the computer, but having a control box controling some kind of actuators and mechanism woul be interesting too.

Thanks for your feed back !

Christian

Hi Christian,

Take a look here if it is a Coronado. If you have a Lunt there would be a need to check how to get rid of the infamous golden tuning wheel.

The idea of Marty is simple but the results you will get are not very good. You will not be able to really get the finest tuning of the etalon.

viewtopic.php?p=316022#p316022

and if you have more questions you are welcome

regards Rainer

[christian viladrich]

Very interesting guys !

Rainer, your system is great. It makes me think we were heading to a Lunt etalon rather a Coronado (for reason of better quality). We need to take into account ease of operation.

Using the tuning wheel o fthe Lunt etalon seems more tricky if want want to avoid any backlash. Or we have to find a way to open the cell.

[pupak]

I tried a simple system based on the principle of bimetal with resistance heating. The tilt up to 10 degrees can be easily regulated with a PWM controller with a temperature sensor powered by 12V. Power consumption is approx. 10-15W. It is a simple and inexpensive solution.

[rsfoto]

Very interesting guys !

Rainer, your system is great. It makes me think we were heading to a Lunt etalon rather a Coronado (for reason of better quality). We need to take into account ease of operation.

Using the tuning wheel o fthe Lunt etalon seems more tricky if want want to avoid any backlash. Or we have to find a way to open the cell.

Hi Christian,

So you have a Lunt. What happens or can you take off the white part and it does not fall apart ? If yes then we are a step nearer for an easy solution.

[rsfoto]

I tried a simple system based on the principle of bimetal with resistance heating. The tilt up to 10 degrees can be easily regulated with a PWM controller with a temperature sensor powered by 12V. Power consumption is approx. 10-15W. It is a simple and inexpensive solution.

Interesting solution but how about repeatability as the bimetal also depends on ambient temperature ¿ or ?

With my stepper motors I always know where I am and adjusting is easy and very fine.

IMHO

[pupak]

The temperature of the bimetal is set so that at about 40°C the angle is 0. The regulator then maintains the set temperature in the required range (40-50°C). At a given temperature, the angle is always the same and I don't need to know it. If I'm in range, I can tell by eye just like with stepper motor control. It is a simple control loop with an accuracy of 0.1 °C, which is 100 positions at 10 ° C. If I build the controller with ESP32, I can control the tilt via BT or Wifi using the ASCOM driver as a rotator or focuser.
There are many solutions. The tilt can also be adjusted with a small piston with a spring using pressure. Just connect the two pistons with a tube and I can regulate without any electronics. I experimented with this a lot when I was building the pressure regulator for the LS80 and the piston will hold pressure for days. It is perfectly sealed.
A stepper motor with a helix is a simple solution from the point of view of control, but unnecessarily complex from the point of view of construction.
The important thing is that it works for you and you are happy with it. After all, it's all about the fun.

[christian viladrich]

Very interesting guys !

Rainer, your system is great. It makes me think we were heading to a Lunt etalon rather a Coronado (for reason of better quality). We need to take into account ease of operation.

Using the tuning wheel o fthe Lunt etalon seems more tricky if want want to avoid any backlash. Or we have to find a way to open the cell.

Hi Christian,

So you have a Lunt. What happens or can you take off the white part and it does not fall apart ? If yes then we are a step nearer for an easy solution.

Hi Rainer,
No decision has been made now regarding choice of the etalon (Coronado, Lunt, Solarscope). This is just that some are easier to control, while others have better quality.

[christian viladrich]

I tried a simple system based on the principle of bimetal with resistance heating. The tilt up to 10 degrees can be easily regulated with a PWM controller with a temperature sensor powered by 12V. Power consumption is approx. 10-15W. It is a simple and inexpensive solution.

Interesting. Could you expand a bit on that ? Maybe with a quick drawing.

[christian viladrich]

I tried a simple system based on the principle of bimetal with resistance heating. The tilt up to 10 degrees can be easily regulated with a PWM controller with a temperature sensor powered by 12V. Power consumption is approx. 10-15W. It is a simple and inexpensive solution.

Interesting solution but how about repeatability as the bimetal also depends on ambient temperature ¿ or ?

With my stepper motors I always know where I am and adjusting is easy and very fine.

IMHO

Yes, this is an important point because we want to control the tilt of the filter in order to tune the filter to specific offsets with respect to Ha.

[pupak]

I don't have as many years of experience as you. I'm basically a beginner, but even my short experience shows that tilting filters are sensitive to the ambient temperature and especially to the optics in front of them, so I think that some fixed value is quite an illusion.
Based on this principle, I can store the temperature for the given condition and I will be about the same.
The picture is just an idea. On the side, a bimetallic strip bent into an arc is fixed against the planchet. It is wrapped with resistance wire and has a thermistor on it. By changing the temperature, the geometry of the tape changes and thus the angle of inclination. Temperature regulation is a trivial Arduino matter.
Hopefully you will get the point from my "English".

[christian viladrich]

I don't have as many years of experience as you. I'm basically a beginner, but even my short experience shows that tilting filters are sensitive to the ambient temperature and especially to the optics in front of them, so I think that some fixed value is quite an illusion.
Based on this principle, I can store the temperature for the given condition and I will be about the same.
The picture is just an idea. On the side, a bimetallic strip bent into an arc is fixed against the planchet. It is wrapped with resistance wire and has a thermistor on it. By changing the temperature, the geometry of the tape changes and thus the angle of inclination. Temperature regulation is a trivial Arduino matter.
Hopefully you will get the point from my "English".

Thanks for the explanation. I now understand what you meant.

Don't wory, my English is worse than worse ;-)

[pupak]

I once did a bimetal micro focus on the SC11 and it worked great. The setting was cca 10 microns/°C, so it was a very fine focus indeed. But the range was only 0.5 mm, which was more than enough for automatic focusing. It was so small that no one understood how it actually worked, because almost nothing could be seen from outside. I controlled it ESP32 with Wifi via ASCOM driver.

[rsfoto]

Hi Christian,

If the golden wheel of the Lunt etalon can not be removed then there is another solution with my stepper motor.

Adjust the Lunt etalon into 0° angle position and we add two adjustable rings which means you just screw the Lunt etalon into rings like depicted on my message about the three different ideas I presented. The rings can be 3D printed with no problem in PETG material which withstands to up to about 70°C. I have printed succesfully threads with a pitch of 0.75mm and the Coronado rings as depicted have a pitch of 1.0mm.



From my 3 ideas the one using the 28BYJ-48 stepper motor is the best.

Bimetal support, designed by Pupak, can also be printed trouble free, unless it reaches more then 80°C temperature where PETG starts to melt.

[rsfoto]

I don't have as many years of experience as you. I'm basically a beginner, but even my short experience shows that tilting filters are sensitive to the ambient temperature and especially to the optics in front of them, so I think that some fixed value is quite an illusion.
Based on this principle, I can store the temperature for the given condition and I will be about the same.
The picture is just an idea. On the side, a bimetallic strip bent into an arc is fixed against the planchet. It is wrapped with resistance wire and has a thermistor on it. By changing the temperature, the geometry of the tape changes and thus the angle of inclination. Temperature regulation is a trivial Arduino matter.
Hopefully you will get the point from my "English".

Hi Pupak,

I don't have as many years of experience as you. I'm basically a beginner, but even my short experience shows that tilting filters are sensitive to the ambient temperature and especially to the optics in front of them, so I think that some fixed value is quite an illusion.

At the moment the telescope with etalons has reached equilibrium eg. has warmed up, about 30 minutes for me, the position does not change anymore and I have lived quite happy with the illusion for the last 15 years and 11 years with my etalon adjuster ...

[christian viladrich]

Hi Christian,

If the golden wheel of the Lunt etalon can not be removed then there is another solution with my stepper motor.

Adjust the Lunt etalon into 0° angle position and we add two adjustable rings which means you just screw the Lunt etalon into rings like depicted on my message about the three different ideas I presented. The rings can be 3D printed with no problem in PETG material which withstands to up to about 70°C. I have printed succesfully threads with a pitch of 0.75mm and the Coronado rings as depicted have a pitch of 1.0mm.



From my 3 ideas the one using the 28BYJ-48 stepper motor is the best.

Brilliant ! I should have thought about it ...

[rsfoto]

Hi Christian,

If the golden wheel of the Lunt etalon can not be removed then there is another solution with my stepper motor.

Adjust the Lunt etalon into 0° angle position and we add two adjustable rings which means you just screw the Lunt etalon into rings like depicted on my message about the three different ideas I presented. The rings can be 3D printed with no problem in PETG material which withstands to up to about 70°C. I have printed succesfully threads with a pitch of 0.75mm and the Coronado rings as depicted have a pitch of 1.0mm.



From my 3 ideas the one using the 28BYJ-48 stepper motor is the best.

Brilliant ! I should have thought about it ...

Hi Christian,

If you do not like 3D printed rings in this case you could try to get the rings from Coronado which I think fit into the Lunt, but they are costly. Long time ago I ordered two sets for my 60mm Coronado which I then transformed into the adjuster by flattening the part of the golden wheel. With 3D printing it is possible to design a 1 piece ring for holding the motor and the corresponding ring with the adjuster thread. Just need to know the thread of the Lunt or whatever etalon you buy.

I have made 3D printed parts with PETG and they are very strong and in this case we have no big stress on this part. The rings at the opposite side of the golden wheel have a tempered steel plate as spring but if we design the rings we can put a normal hinge using a 3mm stainless steel rod and in the front where the motor actuates we put 2 compression springs in order to get the pressure needed for play free adjustment.

The best solution is with the 28BYJ-48 stepper motor.

Rainer

[rsfoto]

Very interesting guys !

Rainer, your system is great. It makes me think we were heading to a Lunt etalon rather a Coronado (for reason of better quality). We need to take into account ease of operation.

Using the tuning wheel o fthe Lunt etalon seems more tricky if want want to avoid any backlash. Or we have to find a way to open the cell.

Hi Christian,

So you have a Lunt. What happens or can you take off the white part and it does not fall apart ? If yes then we are a step nearer for an easy solution.

Hi Rainer,
No decision has been made now regarding choice of the etalon (Coronado, Lunt, Solarscope). This is just that some are easier to control, while others have better quality.

Hi Christian,

Thanks. Somehow I did overlook this message.

My experience tells me that you will not be able to use day by day the same values. I need to tweak a bit every time depending of the hour of the day and the temperature but I can say that the basis values are very similar day byd day.

So if you have H-alpha adjusted on band then you can with great certainty use a certain value of steps to get your desired Off-band adjustments taking the ON-band value as a starting point.

[DavidG]

For the stepper motor control you might want to consider the MyFocuser system by Robert Brown. It was developed for controlling a focuser remotely for astrophotography but the operation would work perfectly for this application as well. It is very easy to build has many option like temperature compensation, can be controlled manually with push button or by Bluetooth, or Wifi and be based on an arduino Nano or a ESP Wifi module. There is also a MyFocuser program to control it so many parameters can be easily changed and setting saved. I also believe and App. It can also be controlled by INDI driver so other programs like K-stars can control it a many cameras at the same time It supports many different stepper motor control boards as well, many of which can do microstepping and stepper motor like the 28BYJ-48 stepper motor. I have build a couple for club members and again it is not difficult to assemble.

https://sourceforge.net/projects/arduin ... erpro2diy/

- Dave

[minhlead]

Hello,

I am looking for any feed back on possible systems for operating remotely a tilt-tuned Ha filter. In other words, any way to implement a system / motor allowing rotation of tilt-tuned etalons (like Lunt, Solar Spectrum, Coronado).

Ideally, this would be to operate the system from the computer, but having a control box controling some kind of actuators and mechanism woul be interesting too.

Thanks for your feed back !

Christian

This might not be on topic but my rig of solar imaging is working remotely. It's a double stacked PST etalon and Quark chromosphere and I only tuned the PST and Quark once. When I got the highest possible cobtrast and field uniformity, I just leave them the way they are and turn on the power on my quark when I need it. Worked out pretty well so far!

[rsfoto]

I just leave them the way they are and turn on the power on my quark when I need it. Worked out pretty well so far!

Hi,

That is more or less good when you always image at same temperature of the telescopes and same ambient conditions.

In my case this is similar to your experience when I open the roof and wait for 30 to 45 minutes so that everything warms up and then I see that even focus is 95% on track.

But my experience is, month in month out, one needs to readjust them tiny bit to find the settings we want...

[minhlead]

I just leave them the way they are and turn on the power on my quark when I need it. Worked out pretty well so far!

Hi,

That is more or less good when you always image at same temperature of the telescopes and same ambient conditions.

In my case this is similar to your experience when I open the roof and wait for 30 to 45 minutes so that everything warms up and then I see that even focus is 95% on track.

But my experience is, month in month out, one needs to readjust them tiny bit to find the settings we want...

For my location, the etalon need adjusting twice. Once for winter and once for summer and that's it. For me the observatory is about 1 driving hour away so that's no big deal. But I got your point, for very distance , unattended remote observatory that could be a problem. In that case, I feel the pressure tuning with knob turning mechanism of a Lunt could be easier to DIY a motorized tuner, may be you can fit a motorized tuner into a PST etalon with some 3d printed puley and timing belt. Other tuning mechanism is quite hard IMO.

[christian viladrich]

Thanks for your inputs guys. Very interesting !