Viewing in Extreme Conditions-- Cold and High Altitude

[Hayduke27]

Hi everyone!  I am a new member and just getting started with astronomy and stargazing.  I have been reading a lot, learning a lot, and just loving the entire journey!  Forgive me if my questions have already been asked, but I have been searching the forums and haven't yet come across the answers I'm looking for.  I live in a small mountain town in Colorado.  Just a few miles out of town and I have very dark skies with minimal light pollution.  This is very exciting for obvious reasons, and my first telescope is due to arrive next week.  Anyway, as I have pondered viewing during the upcoming winter, a couple of questions came to mind:

1.) I live at nearly 8,000ft above sea level.  It seems to me that higher altitude would lead to better viewing as there is less air between me and the stars. am I correct in making this assumption?  Might the viewing up here be slightly more clear than it would at sea level?

2.) It gets cold here in the winter.  I'm talking it can drop below -30*F.  I know that I am supposed to allow my scope to cool to the outside air temperature for best viewing results.  Is there anything I should know about allowing my telescope to cool off to such cold temps?  Is there anything that could be damaged?  Anything I should be especially careful with?  I know I'll need to use a dew shield to prevent frost on the lens.  Will I need any other special equipment?

2a.) Will the extremely cold temperatures improve viewing clarity?  It seems like the cold, still air might make for good viewing conditions, but this is just a guess. Oh, by the way, the relative humidity is very low here, and the cold air is very dry.

 

Thanks for any and all information!!

[Stu]

Hi Hayduke,

Welcome to the forum. Sounds like you are going to have fun!

Absolutely, observing at altitude should give you better seeing as you are observing through less of the most dense lower atmosphere. Cold dry air sounds ideal in that you should also have better transparency and hopefully less dew/frost forming on the scope.

By the way, which scope have you ordered? Generally you will likely need a dew shield plus, in those cold conditions, dew strips on the major exposed optics but that depends whether it is a refractor, Newtonian or SCT/Mak. Let us know and we can advise more.

@jetstream observes in some pretty extreme conditions in Northern Canada so is better placed to answer your questions though. Hopefully he will pop along soon  

Have fun  

[Erla]

Had one scope outside all winter (temperature was bellow -25C at daytime for a while, relatively damp). The telescope did just fine. I had to tighten some screws on the mount though, metal parts contracted a bit, but that's about it. No drama.

[Hayduke27]

My scope is a Celestron NexStar 8.  When it comes to allowing the scope to cool down, I am guessing the optical tube is the most important part.  I have certainly had some digital screens on other equipment come close to freezing up on those cold nights, but all in all electronics seem to withstand the cold without ill effect.  I'll likely keep the power pack in a warm place as long as I can to try to keep my battery life from dropping out on me in the middle of a viewing session.

[jetstream]

Hello Hayduke27 I also observe in cold temps here in NW Ontario, down to -40. I prefer dobs because they seem less affected by the cold whereas my refractors lens cells cringe at these temps. One thing...as you bring a scope inside from these temps the whole thing will frost up- inside and out...not good. My wife made me an insulated bag to bring the scopes in with so they don't frost then melt.

Some cables can give grief as well.

Will you need oxygen at 8000ft?

[Uranium235]

Absolutely right, some types of cable really to stiffen up with the cold and can become brittle or break quite easily. Also, depending on the optics used - some refractors dont cope so well with extreme cold (pinched optics) - but you wont know until you actually try it. I've found that a newtonian design is more robust at lower temperatures since is it more forgiving of contraction. Also, as the evening wears on, its a good idea to tweak up the saddle bolts as the metal contracts (as it reduces the chance of flex when imaging).

Although you are probably also aware, do not touch the telescope (or other metal parts) with bare hands when its very cold! It would be much the same as trying to lick the inside of a freezer...lol.

[newbie alert]

It isn't cooling down..its bringing it to the ambient temp so you don't get air thermals in the ota causing weird spikes on stars..

If you are imaging with a DSLR then it's going to work far better in lower temps than high,and assume a cold dry air is pretty good on the transparancy ( seeing conditions) with a sct you will need dew shield and straps..not for the dew point but for corrector plate frosting up..look forward to the images

[wimvb]

I would be just as much concerned about the mount as the scope. I've read reports about pinching optics in top class refractors, while cheaper scopes were almost unaffected.

But at very low temperatures, the grease in the mount can harden like butter in a fridge. Something to consider if you plan to get into astrophotography.

[Charic]

21 hours ago, Hayduke27 said:

2.) It gets cold here in the winter.  I'm talking it can drop below -30*F.  I know that I am supposed to allow my scope to cool to the outside air temperature for best viewing results.

Thats mighty cold, makes Scotland feel all Summery  at 10°F, although it may have been much colder on my night?

This aspect of cooling is only essential if you store the scope in a warm environment, compared to the outside.
If you can safely store the scope in an outhouse, that's dry with good ventilation, then the scope should be ready to go, and be at the right  ambient temperature.

Its been shown through testing, especially on a Dobsonian, that image distortion and quality is seriously affected by a warm layer of air across the mirrors surface caused by the transference and loss of  heat from the mirror into its surrounding. For this reason, and the movement of any warm air passing up through the scope is the reason to cool the scope. It may never reach the required temperature during/for your session, but if you can reduce these warm air thermals, you will better the image. Also starting off your session with low powered, longer focal length eyepieces, then the distortion is not so noticeable, but becomes very apparent at the higher powers, if not yet at ambient.
I know plastics  can fail under temperature  extremes, not sure how metals and glass in telescopes / eyepieces will behave, not having reached the temperatures you describe.

 

[AKB]

34 minutes ago, Charic said:

not sure how metals and glass in telescopes / eyepieces will behave

...or eyeballs, for that matter.  Have a ghastly image in my mind of eyelashes freezing onto the eyepiece.

[Erla]

1 hour ago, AKB said:

...or eyeballs, for that matter.  Have a ghastly image in my mind of eyelashes freezing onto the eyepiece.

Thanks a lot, now I have that mental image too! Just what I needed before sleep ??. 

If I have nightmares, I'll blame you, sir. 

[gorann]

I see two more advantages of being that high up:

1) Even on cloudy days you have a good chance to be above the clouds

2) If you decide going into imaging using a non-cooled camera like a DSLR you will have very low noise from the electronics.

So, congratulations!

[Hayduke27]

On 9/1/2017 at 22:58, jetstream said:

Will you need oxygen at 8000ft?

I won't need oxygen  I've been living at this altitude for almost 40 years and am very used to it.

 

Thanks for all the replies and info everyone.  I may have to find a place to store my scope out in the cold for the winter season.  It sounds to me like it is very important for the tube to be the same temp as the outdoors, and I know it's not ideal to continually freeze and thaw the poor thing.  I'll have to be careful with the cables and plastic parts for sure, as at our low temps things most certainly do become extremely brittle.

 

15 hours ago, gorann said:

I see two more advantages of being that high up:

1) Even on cloudy days you have a good chance to be above the clouds

2) If you decide going into imaging using a non-cooled camera like a DSLR you will have very low noise from the electronics.

So, congratulations!

We have clear skies the majority of the time here, both due to the altitude and the distance from the oceans.  We're a high mountain desert, and I imagine I'll have ample opportunity to view the stars as long as I can keep myself from freezing to death.

 

My scope is supposed to be here this coming week.  I've been viewing the skies with my binoculars and a spotting scope, but with the bright moon it's been hard to see a lot until after moonset.  I am getting very excited and can't wait to get a peek through my new optics!

[Charic]

2 minutes ago, Hayduke27 said:

I am getting very excited and can't wait to get a peek through my new optics!

...I know the feeling 

[Louis D]

Dew shouldn't be an issue where you live.  However, I'm concerned that the lubrication that allows the mirror to move to focus your Nexstar 8 may congeal to the point you may find focusing very difficult.  You might ask Celestron what the lowest rated temperature is for that scope.  I also wonder about the gear grease for the tracking mount.

I would recommend long eye relief eyepieces so you can keep a distance between your moist eyeball and your cold, dry eyepiece eye lens.  You'll also need to rig up a method to divert your exhaled breath from going across the eye lens.  That eye lens fogging up can be your biggest enemy in the cold, and the only source of moisture where you live is you yourself.

If you can't store it outdoors, you'll probably need an SCT tube fan to pull out the hot air.

[wimvb]

Btw, usb and power cables with silicone insulation rather than plastic remain flexible at low temperature. More expensive to buy, but cheaper in the long run.

[Ben the Ignorant]

Hi, Hayduke27! Your conditions are excellent save for the deep cold. Once you master that problem your viewing will be wonderful. As Louis D said, extended eye relief is a must in the freezing cold, or water vapor from the breathe and skin will condense on the lenses; it happened in my average cold, you must take steps to avoid that in your extreme cold.

The viewing must be pretty good even from your little town, right? Have you estimated your limiting magnitude at your home, and at your outside observing spot? I am always curious of other observers' conditions.

[Hayduke27]

On 9/5/2017 at 05:33, Ben the Ignorant said:

Hi, Hayduke27! Your conditions are excellent save for the deep cold. Once you master that problem your viewing will be wonderful. As Louis D said, extended eye relief is a must in the freezing cold, or water vapor from the breathe and skin will condense on the lenses; it happened in my average cold, you must take steps to avoid that in your extreme cold.

The viewing must be pretty good even from your little town, right? Have you estimated your limiting magnitude at your home, and at your outside observing spot? I am always curious of other observers' conditions.

I am so new, I can't even answer your questions.  However, this is something I'd be curious about and would love to know how I can answer this!  Is there a relatively simple method for estimating my limiting magnitude?  Is it purely a matter of figuring out what the dimmest stars I can see are?  I can see a lot of stars and even the milky way from my yard.  From my dark site the milky way is so bright you can easily explore it with the naked eye.  With binoculars it's so amazing that I still neglect the telescope a bit.  It's just so easy to explore with the binos!!

 

Also, another question came to mind.  When it comes to allowing my scope to cool down to outside air temp, is this something that mainly concerns the tube, or should I make sure to let the entire thing cool down?  The reason I ask is I have the NexStar computerized arm, and I didn't know if that was going to be my weakest link with respect to the cold.  As long as the arm can operate, I think I'll be good to go.  However, if it freezes up, my scope doesn't really seem to have a manual adjustment option. That made me wonder if I shouldn't just keep the arm warm for as long as possible before I set things up.

[Ben the Ignorant]

Yes, you just look for the dimmest star. A perfect patch of sky for that is the Square of Pegasus, which is really three stars from Pegasus and one from Andromeda. Count how many stars you see there, and everyone can share and compare your view. I gave that mission to friends on vacation in southern Italy; one saw 11 stars, the other numbered 13. Maybe the difference was due to age - they are a father and a son - or maybe other reasons that are also interesting to explore for observers.

As for severe cold and scope electronics, I don't know but many others here can answer that.

[Hayduke27]

16 minutes ago, Ben the Ignorant said:

Yes, you just look for the dimmest star. A perfect patch of sky for that is the Square of Pegasus, which is really three stars from Pegasus and one from Andromeda. Count how many stars you see there, and everyone can share and compare your view. I gave that mission to friends on vacation in southern Italy; one saw 11 stars, the other numbered 13. Maybe the difference was due to age - they are a father and a son - or maybe other reasons that are also interesting to explore for observers.

As for severe cold and scope electronics, I don't know but many others here can answer that.

The square of Pegasus sounds like a great way to test my spots!  I'm guessing you mean that I count as many stars as I can see that lie within the box using only my naked eye?  Also, do I count the 4 corners of the square or not?  Thanks and I'm excited to try this!  I wish I had known last night, I was just staring at Pegasus about 8 hours ago.

[Louis D]

12 hours ago, Hayduke27 said:

Also, another question came to mind.  When it comes to allowing my scope to cool down to outside air temp, is this something that mainly concerns the tube, or should I make sure to let the entire thing cool down?  The reason I ask is I have the NexStar computerized arm, and I didn't know if that was going to be my weakest link with respect to the cold.  As long as the arm can operate, I think I'll be good to go.  However, if it freezes up, my scope doesn't really seem to have a manual adjustment option. That made me wonder if I shouldn't just keep the arm warm for as long as possible before I set things up.

You want the air, optics, and optical supports to reach equilibrium with the outside temperature so you don't get tube currents, distorted optics, or distorted collimation.

You may want to put heat wraps on the electronics and possibly eyepieces.

[dph1nm]

High altitude actually impairs night vision due to the lack of oxygen, but I guess if you live there you might acclimatise!

NigelM

[Hayduke27]

21 hours ago, dph1nm said:

High altitude actually impairs night vision due to the lack of oxygen, but I guess if you live there you might acclimatise!

NigelM

I have done a little reading about this, and from what I understand the human body is fully capable of extracting enough oxygen from the air to have no disadvantages with our viewing ability up to an altitude of about 9,000 ft.  Above this, our eyes lose the ability to make out some of the finer details due to lack of oxygen.  However, below 9,000 ft, the higher you get the better the viewing due to being above the most dense layers of the air.

Also, as you mentioned, I live here and have lived here for over 30 years, so I am about as well acclimatized as is possible.  I don't notice the air being any thinner, even when I am out hiking and being active.

[Hayduke27]

On 9/25/2017 at 08:41, Ben the Ignorant said:

Yes, you just look for the dimmest star. A perfect patch of sky for that is the Square of Pegasus, which is really three stars from Pegasus and one from Andromeda. Count how many stars you see there, and everyone can share and compare your view. I gave that mission to friends on vacation in southern Italy; one saw 11 stars, the other numbered 13. Maybe the difference was due to age - they are a father and a son - or maybe other reasons that are also interesting to explore for observers.

As for severe cold and scope electronics, I don't know but many others here can answer that.

@Ben the Ignorant I finally got out for a nice dark night last night, and was able to sit back and give this a good hard try.  NOT including the four corners of the square, I could count 14 stars for sure, and I swear I could almost make out 2 more but not well enough to count them.  I could also see Andromeda plainly with the naked eye.  

I just looked on my Sky Safari app, and it looks like one of the dimmest stars that I could make out for sure and counted in the square is magnitude 6.0. 

This was an incredibly interesting exercise.  It really takes some patience to get your eyes adjusted and then to look so hard into the square trying to tease out the stars that flash into your averted vision but disappear when you try to look straight back at them.  Very interesting and good practice to be sure!  Thanks for the tip!

[Luna-tic]

On ‎9‎/‎1‎/‎2017 at 20:26, Hayduke27 said:

My scope is a Celestron NexStar 8.  When it comes to allowing the scope to cool down, I am guessing the optical tube is the most important part.  I have certainly had some digital screens on other equipment come close to freezing up on those cold nights, but all in all electronics seem to withstand the cold without ill effect.  I'll likely keep the power pack in a warm place as long as I can to try to keep my battery life from dropping out on me in the middle of a viewing session.

Nice telescope. Temperature equilibrium for the tube is important for viewing, but as stated, the colder outside temperature can affect the mechanical operation of the drive, if it gets cold enough to affect the lubrication used in the mechanism. Also be aware of the plastic coatings of the coiled cord of the handset, they could potentially crack when flexed at extreme low temperatures. I would make investing in a dew heater and heat strips a priority, as well as a dew shield for the front of the OTA. Look at something like a Thousand Oaks heater control; it can independently control four heat strips. You'd need a strip for the tube at the corrector plate, one for the eyepiece at minimum (they come in different lengths with Velcro for attachment), and then you could have a couple for the drive axes if you end up needing them. The dew shield not only helps keeping dew off the corrector, it blocks some ambient light and helps with reflections off the corrector.

On ‎9‎/‎1‎/‎2017 at 17:24, Hayduke27 said:

1.) I live at nearly 8,000ft above sea level.  It seems to me that higher altitude would lead to better viewing as there is less air between me and the stars. am I correct in making this assumption?  Might the viewing up here be slightly more clear than it would at sea level?

2.) It gets cold here in the winter.  I'm talking it can drop below -30*F.  I know that I am supposed to allow my scope to cool to the outside air temperature for best viewing results.  Is there anything I should know about allowing my telescope to cool off to such cold temps?  Is there anything that could be damaged?  Anything I should be especially careful with?  I know I'll need to use a dew shield to prevent frost on the lens.  Will I need any other special equipment?

2a.) Will the extremely cold temperatures improve viewing clarity?  It seems like the cold, still air might make for good viewing conditions, but this is just a guess. Oh, by the way, the relative humidity is very low here, and the cold air is very dry.

 

If you're sitting in -30* looking at stars, you're crazier than I am, LOL.

Your body may be acclimated to 8000 feet, but even so, your night vision will suffer some. Central vision essentially disappears, regardless of altitude (night blind spot). Peripheral vision deteriorates rapidly as the angle off center increases. Pilots are recommended to use supplemental oxygen above 5000 feet for night flying . It's much worse if you are a smoker.

The upside is, you're looking through less atmosphere, so most likely, whatever the decrease in your night visual acuity is most likely offset by the improved "seeing". More than the cold, the altitude is what will improve the viewing. Cold air is more dense than warmer air, but in your area the humidity will be less, so less water vapor to cloud the view. I only wish I had your atmosphere here in the Southeast US, as well as your darker skies.

 

Happy viewing, and WEAR A COAT!!