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Cold and Effects On Your Refractor...

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#1 NorthCoast

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Posted 05 December 2007 - 09:58 AM

Hold cold and what effects have you experienced with your refractor(s)? I started this thread becuase I found the off-topic comments in another thread interesting.

I have observered down to 0°F (maybe more) with no adverse effects to the images or optics. Some of my best memories of Saturn were from a bitter cold, still night one Holiday season a few years back.

:)

#2 AnthonyP

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Posted 05 December 2007 - 10:53 AM

I find that the chilliest and coldest of nights are the ones that usually present themselves with the best seeing conditions.

You will need to keep in mind that the refractor will need to cool down otherwise the images will look like they are boiling.

There really shouldn't be an issue with you using the scope in sub zero weather.

#3 Tom T

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Posted 05 December 2007 - 10:57 AM

Up here in mid-michigan, I'm accustomed to cold temps (although mine aren't as bad as PJ's and some other Northern folks). I'll observe in -25F as long as I'm out of the wind. If it's windy - forget it. Then my limit is more like +15 - +20.

As per problems - It depends on the scope. I've used a ton of refractors over the years and some have had more issues than others. TV in particular sticks out as having *no* issues in temps as cold as -25F (they really seem to have have a superb cell design). Given my location, that something that's pretty important to me.

The biggest problems I've seen: cell design that causes pinch (although this can happen over any temp delta), and sticky or frozen mechanical parts. Length of cooldown time can be a bear too. Especially if the temps keep dropping through the night. This is one (additional) reason some prefer doublets to triplets.

#4 Muffin Research

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Posted 05 December 2007 - 11:06 AM

Holy Cow!

-25F that's what -31° celsius?
Ouch!! :bow:

Hmm luckily it doesn't get that cold here.
your windy limit is usually the coldest it get's here.
and about the most I will take, without being completly insulated and have all kinds of thermic devices in my jacket.

#5 Jason B

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Posted 05 December 2007 - 12:14 PM

I don't live too far from Tom so I experience similar temperatures, though we seem to have more cloudy nights being closer to Lake MI :(

I have noticed that the focusers on my Vixen refractors got really tight in the cold until I relubed them with grease that can stand the lower temperaures. I have never had any issues with pinched optics or cool down.

Jason

#6 cvedeler

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Posted 05 December 2007 - 12:22 PM

The coldest I ever ventures out was 0F when I lived in Spokane WA, but the wind was blowing so it felt like -250F. Never again! That was brutal to the extreme! I draw the line right around freezing (32F, 0C) and that is with no wind. Add wind and cold and anything less than 50F is too cold for me. I've become a wimp in my old age. But, I must admit that sometimes when it is super cold it is like the air stops and everything gets crystal clear!

My scopes have always handled the cold much better than I have.

#7 Bob Abraham

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Posted 05 December 2007 - 01:18 PM

Here are some data points from my own experience:

TV102 - No temperature-related effects down to at least -15C (about 5 degrees Fahrenheit; never had it out any colder).

TMB 105/650 - No temperature-related effects down to -10C (about 14 deg F), at which point the lens spacers began to enter into the optical path and become visible as small shadows at the edges of out-of-focus images of stars. No significant effect on the in-focus images though. At -15C (5 deg F) very mild astigmatism (presumably from pinching of an optic in the cell) began to become visible.

TV101 - No apparent effects down to at least -5C (23 deg F; haven't had it out any colder).

TEC140 - No apparent affects down to at least -15C (5 deg F; haven't had it out any colder).

Tak FS78 - No temperature-related effects down to -10C (about 14 deg F; never had it out any colder).

#8 Wehkoja

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Posted 05 December 2007 - 01:42 PM

Last year when i shot Moon Eclipse, it was about -15 degree Celsius! Only bad thing was that my toes got quite cold, but it wasn´t so bad!!! only if you do wear proper clothing!

But then again if the skies are crystal clear and outside temp. is about -20 Celsius, i would go out without any hesitations!

#9 Mike Clemens

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Posted 05 December 2007 - 06:50 PM

I've never had any disturbing effects below 0F with any TEC, Tak, TMB, or AP lenses.

#10 Mike I. Jones

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Posted 05 December 2007 - 07:21 PM

This is my first winter here in Fort Worth with my TOA-130S, so it hasn't really gotten cold enough to affect the image quality.

But what I have already noticed is focus shift. I took some Holmes subs in the evening at about 61 degrees F, with very sharp focus. Then I got back up about 1 or 2 AM to get more shots, took several subs, thought I'd see how they were looking, and saw that they were WAY out of focus. The temperature had dropped to about 40 deg. F. I must have had to refocus at least 0.02", giving a first guess at focus of about 0.0005" to 0.001" per deg. F. The focus moves toward the lens with decreasing temperature.

It must be the lens - the tube is shrinking with dropping temperature but this would cause me to have to focus away from the lens, not toward it. Glass indices of refraction drop with temperature (termed dn/dt), which would lessen the refractive power for the same curves. But the focus shift depends on the change in optical power of each element. Also, S-FPL53 has a higher dn/dt than whatever the other glasses are, which could be a player.

Whatever the cause, I know that the TOA-130S focus moves with temperature. I bought a 1"x0.001" dial gauge and am going to try to rig up something to quantify focus shifts.

But the good thing is that the image quality remained superb at either temperature. It is reassuring to read that this is also the case for much higher temperature extremes.

Mike

#11 ryderc1

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Posted 05 December 2007 - 07:23 PM

Having owned many refractors, I've seen a few cold weather related issues.

I owned two TMB 100/800 CNC's whose lens spacers protruded into the lightpath. In very cold temps (about 15 deg F) the spacers created 3 indentations spaced 120 degrees apart in the out-of-focus outermost fresnel ring. I didn't see any impact on in-focus images although some would argue that it would have an effect.

A Sky 90 I owned had pinched optics in cold weather that produced a hexagonal star test pattern. In-focus images appeared to be fine, though.

I viewed through someone else's LOMO 80/600 lens that had pinched optics in cold weather which produced spikes on brighter stars and a pronounced a square-ish shape to the star test ring pattern.

Finally,I owned an early TOA 130 that put up terrible, mushy views in cold temps. It ended up going back to Japan. Apparently some other TOA's were found to have similar problems and Tak totally redesigned the TOA lens cell. When my scope was returned it delivered superbly sharp, contrasty, color-free views.

#12 Chris Schroeder

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Posted 05 December 2007 - 08:16 PM

I draw the line right around freezing (32F, 0C) and that is with no wind. Add wind and cold and anything less than 50F is too cold for me.

Jeepers, I would only be able observer about five months of the year then:lol:

#13 Tom T

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Posted 05 December 2007 - 08:50 PM

12° here tonight. Absolutely no temp issues with the NP101. Spent the last 2 hours looking through sucker holes. Checked in on Holmes - MAN that thing is cool.

#14 cvedeler

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Posted 05 December 2007 - 09:45 PM

I draw the line right around freezing (32F, 0C) and that is with no wind. Add wind and cold and anything less than 50F is too cold for me.

Jeepers, I would only be able observer about five months of the year then:lol:

You folks up in the far North country don't get decent long nights except in the winter so you better like cold if you are going to do this hobby!

I don't live in Southern Arizona because this is where the truck broke down. Of course we have the opposite problem in the summer. It was only a few months ago when I was in my yard with my scope with just shorts on at 10PM and it was too hot (still over 100F). I packed everything up because I kept sweating on stuff and was really quite uncomfortable.

I don't think I would trade it though. I'd rather do too hot than too cold. And we get 300 clear nights a year to boot! :jump: :grin: :jump: :grin: :D

#15 desertrefugee

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Posted 05 December 2007 - 09:58 PM

And we get 300 clear nights a year to boot!



:coldday:
I spent too many years in New England.

:whee:
Now I live in a place folks come to vacation - (and get 300 clear nights a year).

I just had my binocs out looking at Holmes in shirt sleeves.
:poke:

I haven't noticed any ill effects on my 120ST - but the coldest it's seen so far was ~40F.

#16 rusirius6278

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Posted 05 December 2007 - 10:32 PM

i`m in NE Oh...in my experiences, all my refractors, especially both Vixens, have always handled the very harsh, cold conditions here quite well...and keep up just fine with our fast, huge drops in temp...

in fact, altho successfully used in much colder, etc., temps. with no problems, i was using the Vixen ED103S at 29*-24* while doing this sketch,

Mars

in the 75 mins. i was out observing/sketching...

:) :cool:

Jim

#17 ScottAz

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Posted 05 December 2007 - 10:49 PM

:coldday:

0° here just now (SE Wisconsin) as I run back inside. Cool down time for an 80mm was less than twenty minutes. (Could have been less ... that's how long I left it out in the patch cleared of snow.) Took a look at Mars. Very cool! Grabbed the OTA and ran back inside. Hope to grab the mount soon. Using my Siberian Husky to warm up my hands! :snowedin:

#18 Deep Sky

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Posted 05 December 2007 - 10:55 PM

Just came in from admiring Orion nebula and the 7 sisters.. Up here in Ottawa, Canada.. it's a balmy -20C with the windchill (not to mention 5 foot snowdrifts). Already shoveled 8 times this month.. boy must be winter ;)
Used my new A80SS short tube, after an initial cooldown of about 3 minutes, it was smooth sailing.

-Darren

#19 NorthCoast

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Posted 05 December 2007 - 11:06 PM

Still cloudy in central Ohio... went to an NHL game tonight instead. :) I have only had the M110 out with temps down to high 20s F. I have never had any issues with my M90 or the previous Megrez 80s and WO 66 SD...

#20 mikey cee

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Posted 06 December 2007 - 01:14 AM

AH! you're all nuts!!.....There's Global Warming going on don't you guys stay in the know?? :smirk: :grin: :grin: :pMike

#21 oldeclipse

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Posted 06 December 2007 - 04:23 AM

Guess I am fortunate, it doesn´t ever get much below 40F here.

#22 Canadian

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Posted 10 December 2007 - 09:42 PM

I used to be out in -10 to -30C weather.
Ice in the moustache.
I don't feel the need to do that anymore.
But I know that as you get accustomed to the cold, it's not as big a deal.
Example - It's been -40C all week (many years ago).
Friday night it warms up to -25C, you can feel the difference, so you grab the scope and out you go.
Later on in the month, you have to go out to see an occultation, it's -10 and the 5 days previous it's been zero.
Now you feel colder than you did when you were out observing at -25C.
In Calgary, we tend to get a fair amount of extreme temperature changes, so you sort of get used to it.
And it is sooo nice when a chinook rolls in.
Like the skiers (more often boarders) just outside the city, somedays you see them wearing just baggy shorts and long sleeve shirts, even though it is 0C.
The unfortunate thing is that when it is cold, the sky is so clear.........

#23 SAL

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Posted 10 December 2007 - 10:17 PM

I will commonly observe in temps into the mid teens. I have never had a problem with my refractors but what I do run into is my eye moisture and breath cause the EPs to freeze up on me. :shrug:

#24 Mr. Bill

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Posted 11 December 2007 - 11:56 AM

Its been my experience with the 3 Skywatcher refractors and 1 lens set I've owned over the years that the optics will pinch as the cool down process takes place.

I think that properly designed lens cells is one of the things you get (and pay for) with more expensive refractors.

Another thing I do is keep all my optics I'm planning to use in the garage so that the differences between inside and outside is minimized.


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