Focuser Temperature Compensation Using N.I.N.A.
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- เผยแพร่เมื่อ 27 ก.ย. 2024
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DESCRIPTION:
Today, we are tackling an advanced topic that has the potential of improving your images. It is called focuser temperature compensation.
ASCOM Virtual Focuser GitHub repository:
github.com/jle...
French subtitles available! / Sous-titres en Français disponibles!
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Thanks for this - I have been reluctant to try the temperature compensation but after watching this I should at least analyse the data for my setup and give it a try. It is always a tough decision to spend a rare clear night trying something new or stick with old trusted settings even if they are not perfect !
I always thank you for useful advice AND providing such a good device.
I found the HFR AF trigger in NINA works well for OSC imaging. For monochrome, not so much simply because the HFR can shift quite dramatically with filter changes, particularly NB. The end result is an AF with every filter change, which isn't really a terrible result, but there is a trigger available for that instance without the complication of HFR changes. I limit my imaging to 10/filter so that I be reasonably certain of capturing a full 'suite' of filtered images per session; Temperature compensation may get around that but filter offsets combined with AF per filter changes to establish a "zero" reference each time seems to work very well. IMO - YMMV
See my filter offsets video, it will address your comment, i.e. it is perfectly possible to use temperature compensation with a monochrome camera (I do it all the time 😁) CS!
if your hfr is changing that dramatically after a filter change, your offsets might not be good :) I shoot mono and literally 0 of my filter changes change HFR because my offsets are working correctly. you are likely wasting a ton of imaging time.
Thanks Julian for this informative video
I have been using Astro Photography Tool’s Temperature (APT) Focus Compensation and have been able to keep my RedCat 71 with in the Bahtinov Grabbers’ critical focus range for over 4 hours this fall. APT’s temperature focus compensation runs in the background after being enabled but can be enable and disabled in APT’s scripts. It can also be configured to adjust focus during or between images. I have wanted to use NINA but did not want to give up temperature focus compensation. You have solved the problem.
Thanks
Awesome! Now, you can join our cult 😂 (see Dylan O’Donnell’s latest video)
Thank you Dark Sky Geek, a few nights ago I was out experimenting with NINA’s auto focus and the temperature was dropping quickly. I noticed that every auto focus run gave me a different result. So that is why I started looking at temperature compensation. Your video was very helpful to me. I have already bought an external temperature sensor for my robotic focuser (an Esatto 2” from Prima Luce Lab). A couple of questions if I may; considering that it is the tube that is contracting, why not place the temperature sensor on the tube? I plan to stick the sensor onto the tube with some adhesive backed foam, with some heat sink paste to provide good thermal contact to the tube. The foam will partly isolate the probe from the air temperature changes and should provide a less fluctuating result. Secondly, I have found that NINA’s auto focusing doesn’t work so well with nebulas. My work around plan was to write into the sequence a slew to a clear star group, do the AF, and then move back to the target nebula for imaging. Your approach of getting NINA to monitor the HFR of the images taken and compare the change in HFR to the last AF run would not be possible for me if I use a nearby star group for my autofocusing. So I don’t know where that leaves me - another problem to solve. Anyway thank you for the video, well done. Regards, John Bellingham
1. It’s not the tube that’s causing the focus to change, it’s likely the shape of the lens/mirror that’s changing. You don’t need to stick the temperature probe to the tube.
2. Focus with the L filter, and you won’t have any problem with nebulae. Use filter offsets as needed (I’ll do a video on filter offsets soon)
Best of luck!
@@darkskygeekG’day Dark Sky Geek, thanks for getting back to me so quickly. I have a 12” Meade SCT, so where would you suggest that I mount the temperature probe? Regarding the filter for improving NINA AF runs at nebulas; I have a ZWO dual band filter, will this help? (BTW I have a OSC camera.). Thanks again. Regards, John Bellingham
@John Bellingham You don't need to mount it anywhere special. I let mine hang in the air.
You need to AF with an L filter, and then configure NINA with the proper filter offsets.
Hi DarkSkyGeek, I started to follow your “Downloading and Installing the Driver” instructions but didn’t get very far because I have no experience with command prompts and such. I was able to save the .DLL file in a folder, and I could see the RegAsm.exe application on my system, and I was able to bring up an administrative command prompt. However from here on I have no idea what to do. If I could ask for a little (step by step) help from you I would greatly appreciate it. Or perhaps you may consider that without this basic knowledge in programming perhaps it is too dangerous for me to continue. Thank you for your help. Regards, John Bellingham
Hi DarkSkyGeek, my son had a chat to a friend, and he managed to install the driver, and received the “Types registered successfully”. However when I selected it in NINA I received an error message. “ASCOM Driver Error
Unable to connect to DarkSkyGeek's Virtual Focuser ASCOM Driver. Reason:
set - " is an invalid value. The valid range is:.”
I thought that you would like to know. Regards, John Bellingham
Fantastic, thanks a lot! Exactly what I was looking for (got a jumpy EAF external T probe, too)…
Do I understand it right that you collect the current temperature from the sensor every second and store this in a list with 120 elements, continuously deleting the oldest value when adding a new value. And the temperature your driver returns is the average of these last 120 raw values. TEMPERATURE_WINDOW_IN_SECONDS = 120 is the size of your moving average window, right? Although in the code comments you write “60 seconds”…?
😀👍
Yes, you are correct. The comment in the code was probably not updated when I switched from 1 minute to 2 minutes.
Merci pour cet exposé, clair, précis... et pas trop long. Sans prétendre utiliser la technique de compensation pour l'instant, une question de curiosité : j'imagine que l'info de température est récupérée par NINA et qu'il faut donc 1/ un focuser avec sonde et 2/ un driver capable de remonter cette info. Correct ?
Oui, c’est exact. Notez que la température fait partie de l’interface ASCOM IFocuserV3: ascom-standards.org/Help/Platform/html/T_ASCOM_DeviceInterface_IFocuserV3.htm
It looks like that in NINA the focusing temperature compensation only works with focusers that have a proprietary temperature probe (like the ZWO EAF). I am not using the EAF but another DIY ASCOM focuser (inspired from your very good OAG focuser project). Is there a possibility to plug a sort of independant 'ASCOM' temperature sensor that I could use for the compensation purpose? I am using NINA and happy with refocusing in function of HFR changes, though, so it is more a curiosity question... Or why not using both...
Many people have asked the NINA developers to consider using another source for the temperature readings, but they have resisted so far. So, your only option is to modify my ASCOM driver and firmware and electronics to report some temperature reading. Temperature sensors are very affordable. You will have to calibrate it. It’s certainly a fun project. Or you could modify the ASCOM driver only and have it get the temperature info from somewhere else, like a weather station. There are options. Maybe I’ll update my virtual focuser driver to make these things a bit easier for people to integrate with NINA. CS!
Thanks for your approach about this topic which is key for a great imaging session, I have question for you, how to revert driver is something goes bad? Also how much time I can save using this technique comparing with I focus every 30 minutes? The key is save time, and looks the driver and Nina are ready for this. Thanks
The goal of temperature compensation is to bring more subs near perfect focus, not to save time running autofocus.
I got a notice last night in NINA for a EAF firmware Update to version 3.1.9. I installed it and now the DarkSkyGeek's Virtual Focuser ASCOM Driver is not working. If I select your driver NINA is showing temperature of -273.00 C, sometimes NINA will show focuser movement, but the EAF is not moving, and the beeper will run continuously.
I have been using temperature compensated focus since you released the driver and have had nights where the focus was still in the Bahtinov critical range after 4 hours without doing an autofocus. During this time my focus steps have increased over 200 steps. My autofocus step size is 150 steps.
Wow, I don’t know what ZWO did to their firmware. -273C is like 🥶😁 Maybe see if you can downgrade the firmware?
I tried and the older version would not load.
ok. Maybe try contacting ZWO support? What if you don’t use my ASCOM driver, what temperature does the ZWO driver report? If it also reports -273C, then there is a problem with the firmware or the hardware. Hope this helps!
I just installed ZWO_ASCOM_Setup_V6.5.19.exe and things are acting differently. I am now seeing the -273C for ZWO Focuser (1) driver and the Virtual Focuser ASCOM driver. In the past the temperature was different in the ZWO Focuser (1) driver. I am trying to remove the Virtual Focuser ASCOM driver. I will get back to you when I have more information.
OK. If ZWO’s driver reports a bad temp, then there is nothing my driver can do to fix that. Also, removing/unregistering my driver won’t change anything. I think your hardware or the firmware you just installed is faulty, and I recommend you reach out to ZWO support.
Merci! Excellente vidéo et comme toujours très claire.
Star HFR is bad approach for refocusing, since it depends on wind, seeing, etc. Those factors change a lot during night. For example, you have 3 then 4. Focus on, waisted time. This 4 could be 3.3 in the next frame without refocusing
Sure. However, NINA uses a “window” of multiple samples, and a threshold - both are user configurable - to determine when to run an autofocus routine. So, in practice, it has not been an issue, at least not for me. But yeah, temperature compensation can improve things a bit.
@@darkskygeek It is big issue if fl 2500mm f10 and O3 or Ha filter used for some regions; for example, Abell 39. Basically, small and dim planetary nebulae will be not covered by your method. Although, it may work for CDK>17” and f ratio
@@anata5127 I don’t understand what you are saying. First, I always run autofocus using a luminance filter, and then, I apply some filter offset once I switch filters. Hopefully, the field of view has a few stars in it, enough to measure the star HFR and have a statistically meaningful result. Why would that not work? Or maybe I missed something in your message. Thanks!
@@darkskygeek Autofocus with O3 doesn’t work in conditions, I listed (yes there are stars, but you see them after 60 sec exposure). Yes, you are right. Run focus in L and apply offset. This is a way I do. Moreover, I apply temperature compensations. 1 degree shifts 30 steps (120um).
Did you image with long fl when target is 0.5-2’ and you need details? Eccentricity should be
@@anata5127 Don’t autofocus with an OIII filter! Autofocus with a luminance filter. A focal length of 2500mm and an APS-C sensor (for example) will show plenty of stars to get a good measurement of the star HFR and the autofocus will succeed. Then, you switch to your OIII filter and you apply the offset for that filter, which you measured when you installed that filter in your filter wheel. I still don’t understand what the problem is.
Very clear and informative. Good job!
Good video of an important topic for everyone with f/4 and faster! I implemented a quadratic temperature compensation (with elevation residuals) in Kstars/Ekos, and I was fretting having to do this again with N.I.N.A upon changing mounts. Glad to see at least a linear Temp Compensation is available already in N.I.N.A. I've been using my own home grown Ekos Temperature Compensation for 2 years, and I couldn't ever go back to the old ways (delta C triggered AF run, HFR AF trigger, or time based AF trigger). I always run an AF to start on a target, then let temperature compensation take over. I have run several hours and always been inside the CFZ @ f/2.2 (RASA 11). It's just awesome. Now repetitive AF runs (after the first on a target) seem very wasteful of imaging time.
When you say relative, I'm assuming that if for any reason you manually adjust focus, the "setpoint" (base) of the integrator will reset to the latest location? Both completed AF runs, and manual setpoints should be honored (whichever was done most recently) as the starting point for the relative position. Also, is there a threshold for allowed changes (so that nuisance/small changes are built up before being applied)? Thanks.
Thanks for the kind words, and glad to meet other like-minded people 😄
The “Relative” option (actually, the option name is “Absolute”, so “Relative” = “Absolute” set to off) of the “Move Focuser by Temp.” instruction means the following:
New focus position = Current focus position + Slope * (Current Temperature - Temperature at last focuser movement)
Reference: nighttime-imaging.eu/docs/master/site/sequencer/advanced/instructions/
This is important because, as I explained in the video, the model is likely not accurate enough to be used with the “Absolute” option turned on. There are too many variables at play. My testing showed that doing an initial autofocus run, and then using the command in relative mode, is a better option.
There is no threshold that can be parameterized for that instruction.
Hope this helps. Thanks for watching!