My Low-E-wrapped old Helios 120mm f/8.3 on a HEQ5

[Moonlit]

@Tufty Here's my rig all wrapped in Low-E like we talked about :)
It's the 6.5mm thick version of Low-E insulation with low-emission tape holding it together.
I've removed the EPs and turned the diagonal upside down to keep it warmer and safe.

At this point I had been observing for an hour and a half and it got chilly so I took my EPs and myself inside to warm up.

If anyone wonders what I wear to keep warm in -7 Celsius:
- Lightweight rubber boots with thick insulation designed for sitting still - not very suitable for walking in

- "snowmobile uniform" - a cheap overall with thick insulation, the kind worn by farmers and scooter drivers. Wool underwear, wool sweater and jogging pants underneath it.

- Ushanka hat that covers the ears and chin

- Photography gloves with slits for forefingers and thumbs. I think I'll upgrade to thick mittens when I go out again later

[Moonlit]

Addendum: The point of wrapping the scope, diagonal and EPs in low-emissivity material is to prevent it from cooling down below ambient temperature due to heat radiation to the open sky, which can cause it to drop below the dew point temperature and thus dew.

Tonight I set up the scope at around 3:30pm just after sunset (60 deg latitude) when the temp was -7C/19F and took it down around 9:45pm when the emp was -9.5C/15F.

Relative humidity measured on-site by my Netatmo weather station was 93%, giving a dew point of just 1 degree below ambient. The weather report suggested around 85% humidity a bit farther down the valley and 250 meters lower, so the Netatmo might measure it wrong.

Anyway, those numbers tell me that without the low-e wrap the telescope or EPs WOULD have had a high probability of dewing over because it loses so much heat to the sky through thermal radiation due to the high emissivity of the black paint. It has frequently done so in the past, which is why I went to the trouble of wrapping it.

To me it looks like low-e wrapping actually works.

[Tufty]

@MoonlitBrilliant. Really appeciate your write up.  This is exactly what I am interested in (apart from eyepieces generally at the moment - on which I still have far to go! ).  I am very well persuaded about the scope wrapping.  I also intend to be more scientific around ambient temp and and sky radiation etc.!  I don't know how accurate my apps are with the local data so will probably look into some kind of instrumentation as you suggest.  That does leave the EPs dewing up, so basically I guess it's a case of warming in the pockets!  Haven't solved that one. 

 

Clothes! lol it's been raining here like forever, but we had over a week at -5C before Xmas.  I bought a trapper hat a few weeks ago which covers ears and seems to work well (I wouldn't go out shopping in it though!). I found wearing a face mask keeps my breath away from the EPs a bit.  I also was given """Nordic""" socks - they are wool based but I don't think they are the real thing or 'nordic; apart from the patterns on them, but too thick to wear with my footwear!  So, my entire astronomy wardrobe needs revisiting! Photography gloves looks like a great idea, I'm not wearing any hand gear at the moment as I need fingers to feel for EPs etc .  I have decent enough coats to sit in the cold down to -30C but nothing for the legs! Still looking into that.. I was thinking thinsulate joggers or something.

 

Thanks again fio taking the trouble to write all that up

 

It's after Christmas and I'm still talking about socks lol