<p>For the last few months we have been constantly setting up an Artificial Horizon (Davis Instruments) using motor oil as the liquid.   We discovered that it is very hard to take a reading off of it unless we wait at least 15 minutes for the oil to become perfectly still.</p>
<p>We tried leaving it in place and covering it with a 5-gallon bucket.  This doesn't work very well as the glass covering it fogs up.   When we try to dry the glass, the oil begins moving and we are back to waiting 15 minutes.  We tried using it without the glass covers, but discovered that this only works when there isn't any wind.   We live on top of a mountain, there is always wind.</p>
<p>Googling &quot;Permanent Artificial Horizon&quot; and other various wordings has not helped.</p>
<p>We intend to use this spot at least twice daily.  We hope to learn to use the sextant as a navigational tool.  However, we are mainly combining the sextant, compass &amp; watch to mark the position of objects we see through the telescope so that we can record them in our Astronomy Diaries.  Our telescope doesn't do this for us.</p>
<p>Waiting 15 minutes or more for the oil to stop moving is proving to be a pain in the rear because it has to be done so often.   Has anyone figured out a way to permanently set up an artificial horizon that can be left in place?</p>

CC BY-SA 4.0
2020-10-31T04:10:43.190Z
What is the source of the motion? Vibration or wind, or is it thermal convection because the system is not yet thermally equilibrated? [The web site](https://www.davisinstruments.com/product/artificial-horizon/) says to use water and water is 1) transparent to visible light so won't be heated by sunlight as strongly as motor oils (especially the dark ones) and 2) has lower viscosity and better thermal conductivity than oil, so it might reach equilibrium by convection and conduction more quickly. What factors lead you to switch to oil in the first place?
uhoh
CC BY-SA 4.0
2020-10-31T12:02:22.717Z
We don't use water for 2 reasons, it freezes and the other reason is that it is not as reflective as motor oil.   We use new motor oil, it is a clear and slightly yellow color.   The source of the movement is us pouring in the oil into the container, or moving the full container, etc.   We keep the motor oil container in an unheated shed, so it should be about the same temperature as outdoors.   Regardless, for  a permanent Artificial Horizon, water is not an option because it's evaporation fogs the glass and also freezes in the winter.
Bookaholic
CC BY-SA 4.0
2020-10-31T12:57:32.487Z
Quite a challenge! But I wonder if you now were to just try the *recommended fluid for this product* once as a *diagnostic test* if it would also require 15 minutes to settle or not. It's just a thought, offered as a potentially useful debugging step. [This suggests](https://blog.adafruit.com/2015/03/31/striking-reflective-surfaces-made-from-used-motor-oil-reflect-the-ornate-architecture-of-bellelay-abbey-arttuesday/) some oil can be quite reflective but it's "art" not science.
uhoh
CC BY-SA 4.0
2020-10-31T12:59:35.917Z
[Reflectance spectra of crude oils and refined petroleum products on a variety of common substrates](https://www.spiedigitallibrary.org/conference-proceedings-of-spie/7687/1/Reflectance-spectra-of-crude-oils-and-refined-petroleum-products-on/10.1117/12.852200.full?SSO=1) is paywalled, but they do mention that the quick evaporation of volatiles in the beginning is noticeable. I wonder if you "aired out" some oil first, leaving it exposed to the air so volatile compounds can leave, then tried it, perhaps it would not need the additional 15 minutes any more.
uhoh
CC BY-SA 4.0
2020-10-31T13:06:19.100Z
Also, the index of refraction and therefore reflectivity of saturated sugar solutions is much  higher than for pure water, and that might lower the freezing point as well. At normal incidence the reflectivity in air [goes as](https://en.wikipedia.org/wiki/Fresnel_equations#Normal_incidence) ((1-n)/(1+n))^2 which illustrates that increasing the index can improve the reflectivity a lot!
uhoh
CC BY-SA 4.0
2020-11-02T14:27:40.853Z
@uhoh I will try the airing-out the oil suggestion by leaving an uncovered pan of oil out in the shed for about a week.    Sugar/sweet water will not work because bear/raccoons/critters are attracted to it.   They might check out the motor oil, but will not be tempted to return for it.  If the oil stops "evaporating" and leaving a film on the glass after airing out, this would solve the problem as we can then just cover it with a 5-gallon bucket.  Thank you for this tip.
Bookaholic
CC BY-SA 4.0
2020-11-02T22:19:23.707Z
Wow I'm getting the picture now that you have to take a lot more than optics into consideration :-) Okay have fun, good luck! btw another site on which this might be askable is **The Great Outdoors SE**. I had some luck there with an instrumentation question [How do simple compass needles remain level instead of see-sawing with magnetic dip? Are they flat even near the poles?](https://outdoors.stackexchange.com/q/21360/12619) and also [How did O’Brady charge his electronic gear while hiking across Antarctica?](https://outdoors.stackexchange.com/q/21362/12619)
uhoh
CC BY-SA 4.0
2020-11-20T22:32:42.463Z
@uhoh As it turns out, the oil's evaporation film is significantly lower after using oil that sat out for a week.   It is not 100%, but is see-through enough that we can use it, then clean it afterwards.   Cleaning causes the oil to move - but we have already used it and it will stop moving by the time we do so again.   Thank you very much for this tip.
Bookaholic
CC BY-SA 4.0
2020-11-21T01:22:13.683Z
Wow, that's good news, good to hear it and thank you for taking the time to stop by and leave an update. Would you consider posting a short answer here with that information? It's always better when Stack Exchange questions receive an answer, that way people searching are more likely to find it and benefit from the answer. Comments are less search-able and considered temporary; they might be deleted in the future. *Thanks!*
uhoh
<telescope><amateur-observing><horizon>
Is there a more permanent way to set up an Artificial Horizon?
Bookaholic
# Is there a more permanent way to set up an Artificial Horizon?

(Asked by: username_0 on 2020-10-30)

For the last few months we have been constantly setting up an Artificial Horizon (Davis Instruments) using motor oil as the liquid. We discovered that it is very hard to take a reading off of it unless we wait at least 15 minutes for the oil to become perfectly still.

We tried leaving it in place and covering it with a 5-gallon bucket. This doesn't work very well as the glass covering it fogs up. When we try to dry the glass, the oil begins moving and we are back to waiting 15 minutes. We tried using it without the glass covers, but discovered that this only works when there isn't any wind. We live on top of a mountain, there is always wind.

Googling "Permanent Artificial Horizon" and other various wordings has not helped.

We intend to use this spot at least twice daily. We hope to learn to use the sextant as a navigational tool. However, we are mainly combining the sextant, compass & watch to mark the position of objects we see through the telescope so that we can record them in our Astronomy Diaries. Our telescope doesn't do this for us.

Waiting 15 minutes or more for the oil to stop moving is proving to be a pain in the rear because it has to be done so often. Has anyone figured out a way to permanently set up an artificial horizon that can be left in place?

**Tags:** telescope, amateur-observing, horizon

> **Comments:**
> **username_1**: What is the source of the motion? Vibration or wind, or is it thermal convection because the system is not yet thermally equilibrated? [The web site](https://www.davisinstruments.com/product/artificial-horizon/) says to use water and water is 1) transparent to visible light so won't be heated by sunlight as strongly as motor oils (especially the dark ones) and 2) has lower viscosity and better thermal conductivity than oil, so it might reach equilibrium by convection and conduction more quickly. What factors lead you to switch to oil in the first place?  
> **username_0**: We don't use water for 2 reasons, it freezes and the other reason is that it is not as reflective as motor oil.   We use new motor oil, it is a clear and slightly yellow color.   The source of the movement is us pouring in the oil into the container, or moving the full container, etc.   We keep the motor oil container in an unheated shed, so it should be about the same temperature as outdoors.   Regardless, for  a permanent Artificial Horizon, water is not an option because it's evaporation fogs the glass and also freezes in the winter.  
> **username_1**: Quite a challenge! But I wonder if you now were to just try the *recommended fluid for this product* once as a *diagnostic test* if it would also require 15 minutes to settle or not. It's just a thought, offered as a potentially useful debugging step. [This suggests](https://blog.adafruit.com/2015/03/31/striking-reflective-surfaces-made-from-used-motor-oil-reflect-the-ornate-architecture-of-bellelay-abbey-arttuesday/) some oil can be quite reflective but it's "art" not science.  
> **username_1**: [Reflectance spectra of crude oils and refined petroleum products on a variety of common substrates](https://www.spiedigitallibrary.org/conference-proceedings-of-spie/7687/1/Reflectance-spectra-of-crude-oils-and-refined-petroleum-products-on/10.1117/12.852200.full?SSO=1) is paywalled, but they do mention that the quick evaporation of volatiles in the beginning is noticeable. I wonder if you "aired out" some oil first, leaving it exposed to the air so volatile compounds can leave, then tried it, perhaps it would not need the additional 15 minutes any more.  
> **username_1**: Also, the index of refraction and therefore reflectivity of saturated sugar solutions is much  higher than for pure water, and that might lower the freezing point as well. At normal incidence the reflectivity in air [goes as](https://en.wikipedia.org/wiki/Fresnel_equations#Normal_incidence) ((1-n)/(1+n))^2 which illustrates that increasing the index can improve the reflectivity a lot!  
> **username_0**: @username_1 I will try the airing-out the oil suggestion by leaving an uncovered pan of oil out in the shed for about a week.    Sugar/sweet water will not work because bear/raccoons/critters are attracted to it.   They might check out the motor oil, but will not be tempted to return for it.  If the oil stops "evaporating" and leaving a film on the glass after airing out, this would solve the problem as we can then just cover it with a 5-gallon bucket.  Thank you for this tip.  
> **username_1**: Wow I'm getting the picture now that you have to take a lot more than optics into consideration :-) Okay have fun, good luck! btw another site on which this might be askable is **The Great Outdoors SE**. I had some luck there with an instrumentation question [How do simple compass needles remain level instead of see-sawing with magnetic dip? Are they flat even near the poles?](https://outdoors.stackexchange.com/q/21360/12619) and also [How did O’Brady charge his electronic gear while hiking across Antarctica?](https://outdoors.stackexchange.com/q/21362/12619)  
> **username_0**: @username_1 As it turns out, the oil's evaporation film is significantly lower after using oil that sat out for a week.   It is not 100%, but is see-through enough that we can use it, then clean it afterwards.   Cleaning causes the oil to move - but we have already used it and it will stop moving by the time we do so again.   Thank you very much for this tip.  
> **username_1**: Wow, that's good news, good to hear it and thank you for taking the time to stop by and leave an update. Would you consider posting a short answer here with that information? It's always better when Stack Exchange questions receive an answer, that way people searching are more likely to find it and benefit from the answer. Comments are less search-able and considered temporary; they might be deleted in the future. *Thanks!*  

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## 0 answers

