Keeping the Lunt warm

[Starpowered]

Going to be 20-ish on the 11th in Ohio.

Checked in with Lunt folks about my LS50THaP and was advised to keep the blocking filter warm.

When its colder, I always wrap my hand around the Pressure tuner to keep the lube warmer and O-rings more pliable. 

First "event" with scope and hope the skies give me a break;-)

[Rob Sellent]

I imagine that '20' is referring to Fahrenheit and if so.....wow 😮 (just looked up what that is in celsius).....that is freezing ⛄

I'm in east Spain and the temps rarely dip below 50 Fahrenheit, even in the dead of a cold winter's night

Just thinking outloud, perhaps a little dew heater might do the trick

[johninderby]

Doesn’t get that cold in the UK very often. Around here we might get an inch of snow once or twice during the winter or sometimes none at all. 

[DaveS]

What is "Fahrenheit"? I seem to recall something of that name from my youth but have only used Celsius or Kelvin for the last 50 years or so.

[johninderby]

Bit like those old fashioned thread sizes Americans use instead of proper metric stuff. 😁

[Carbon Brush]

Please tell us more....

Are Lunt saying the scope BF may be damaged by extreme cold? Or is this just dew prevention?

I can understand keeping the grease warm and O rings pliable.

[vlaiv]

I've read this warning many times - it is often written on TS website along Ha solar gear - like this:

At some point I thought that Daystar quarks and their high return rate had something to do with this. Solar telescopes are shipped with good packaging - meaning a lot of styrofoam and such which is insulator. Quark eyepieces are shipped in regular small boxes and probably not well insulated. If shipment is in winter time or cargo is carried on an airplane - high altitude / low temperature, and I doubt that cargo bay is heated - this could lead to item being on lower temperature for some time.

So yes, that is a hazard that needs to be addressed. Don't know how it relates to blocking filter - it is often quoted for Fabry Perot filters - which use oil, so air spaced ones should be fine?

 

[Merlin66]

That's for Daystar "solid" etalons..... not for the air spaced etalons used in the Coronado and Lunt instruments.

A claim was made that extreme low temperatures could affect the central wavelength of the blocking filter and cause to go "off band" reducing the transmission and performance of the instrument.

Lunt now supply a heated rear plate which can be fitted to the BF diagonal to alleviate the problem.

Here in Australia I'm more concerned about the effects of elevated temperatures.

I looked at getting a Quark, but Daystar said I'd have to order a "special" which could come on-band at ambient temperatures above 40 deg C (The quark has no cooling capabilities and relies on heating only to come on-band). I declined the offer.

 

[Carbon Brush]

Slightly off topic. But prompted by Vlaiv.

I have seen instances of heatsinks debonding from integrated circuits (chips) following a transatlantic air freight journey.
This prompted me to look into the shipping conditions. They are quite worrying for expensive scope parts.

Imagine taking a room temperature item and boxing it for shipping in the UK winter.
UPS/DHL/TNT/Fedex collect it from you.
It spends the rest of the day in the back of a van - unheated. Taking the parcel to near freezing.
After a short time in the depot, it goes onto a trunk vehicle for delivery to the airport, again unheated.
At the airport it is in an unheated warehouse for a short time. It may even spend time on the tarmac in an aluminium cargo container.

By the time the parcel gets onto the flight, it is definitely around 0C.

Many cargo flights have an unheated and unpressurised hold. Presumably no money (weight) is spent on insulation.
We all know the outside air temperature at altitude is -35C or even -50C.
We know that flights follow great circle routing (give or take war zones, politics, etc).
This means a transatlantic flight (8 hours or more) spends several hours in really cold air. Transiting over Iceland, Greenland, Northern Canada.

Your delicate optical or electronic parts are going to be chilled to -40C or cooler.

Further, the pressure at altitude is only about 20% of surface pressure.
This means any sealed components containing air are at almost 0.8 bar above ambient pressure.
Pressure change is no problem for a Lunt pressure tuner. What about other things? Unintended air bubbles in assemblies?

I took a glance at the Lunt and Coronado web sites.
Telescope storage temperature and pressure limits are not specified - unless this is hidden somewhere.
This means you can buy a new scope, store it near absolute zero and take into space without problem!

As for me. On cold days (sub zero) the probability of solar viewing is quite low.
With the sun a 26deg above the horizon at noon mid winter, and a clear sky.........

David.

 

 

 

 

 

[Rusted]

How do these low temperatures affect the PST etalon?
Mine stays out in the dome, unprotected, with potential drops to -20C.

Though not very often in today's warming climate.
Minus single digits C are still commonplace.

26° above the horizon in midwinter? Mine scrapes past the Meridian at 11° ish!

[Peter Drew]

Be careful not to confuse etalons and blocking filters.   🙂

[Rusted]

23 hours ago, Peter Drew said:

Be careful not to confuse etalons and blocking filters.   🙂

Me confused? 

[Nigella Bryant]

It's the blocking filters that struggle at low temperatures. Hence lunt sells the blocking filter heater. I guess a mini dew heater wrapped around the bf would do the same and much cheaper. 

[Solar B]

I think that is about the daftest thing I’ve 

ever seen with regard to solar astronomy 😂

Brian