ASKAP Timelapse, WA

[alexch (Alex)]

Originally Posted by philiphart

nice work as always alex. no doubt you had fun out there in the dark. i like the fisheye shot too .

having no light pollution domes in any of the shots is impressive and there's a great zodiacal band through the fisheye shot. what was your impression of the darkness of the skies visually.. any difference high in the sky to other victorian dark sky sites?

i do want to know how you got it all on the plane though!

cheers
Phil

Thanks Phil.
Indeed these were the darkest sky I have ever experienced. The first night there was no airglow and the sky background was subjectively a little darker than I have seen elsewhere. I wish I had my SQM with me but even 200 grams of extra luggage weight were potentially a problem.

On subsequent nights there was airglow and I wouldn't say there was a huge deal of difference to the Victorian dark sites. Seeing the Milky Way set parallel to the horizon and then disappear was very cool though.

We'll have to talk about the luggage over beer. Are you going to VicSouth this year?

[colinmlegg (Colin)]

Originally Posted by alexch

Thanks Phil.
Indeed these were the darkest sky I have ever experienced. The first night there was no airglow and the sky background was subjectively a little darker than I have seen elsewhere. ?

It's pretty rare to get a night completely free of airglow out there. I've only experienced a couple. One at karijini and the other wolf creek crater. Most of the time some yellow, red or green airglow is visible in the shots.

[Peter Ward]

A masterful effort. I enjoyed the sequences immensely.

[Phil Hart]

Originally Posted by alexch

Thanks Phil.
Indeed these were the darkest sky I have ever experienced. The first night there was no airglow and the sky background was subjectively a little darker than I have seen elsewhere. I wish I had my SQM with me but even 200 grams of extra luggage weight were potentially a problem.

On subsequent nights there was airglow and I wouldn't say there was a huge deal of difference to the Victorian dark sites. Seeing the Milky Way set parallel to the horizon and then disappear was very cool though.

We'll have to talk about the luggage over beer. Are you going to VicSouth this year?

hmmm.. i would like to go to vic south but can't make it now. will be using the saturday to practice eclipse imaging.. only weekend day i have at home in october! beer will have to wait for another time..

[Ric]

Awesome work Alex

Cheers

[iceman (Mike)]

You are a master, Alex.

This is now IOTW.

[bartman (Bart)]

Originally Posted by iceman

You are a master, Alex.

This is now IOTW.

This could even be VOTW / VOTY........
As much as I like the pic used for IOTW , it must have been hard to choose one Mike. I seriously love the cherry picker one and also the last one ( shows the distance between scopes and remoteness ).
Great call none the less!
Congrats Alex!!!!!
Bartman

[geoffsims (Geoff)]

Alex, Phil, Colin:

A quick note regarding airglow. You need to be careful when comparing the darkness of sites, even if using a handheld meter. Airglow fluctuations are quite complex. As seen in most time lapses, it is obvious to us airglow varies on short timescales (~minutes). There are also larger diurnal, and seasonal effects that come into play. Lastly, it fluctuates on decadal scales with the solar cycle. If you have access, there are many great papers in the literature about this.

See e.g. http://arxiv.org/abs/astro-ph/9706111

Average Mauna Kea sky brightness varies by 0.5 mag/arcsec^2 over a solar cycle!

Also see: http://arxiv.org/abs/0801.2270

My point is it is very difficult to visit a site once, and draw conclusions on its sky brightness (more specifically the amount of airglow present or not) relative to other sites. Light pollution aside, of course there are other factors that come into play (e.g. the latitude of the site will determine the range of angles that the zodiacal light will be be seen at, which will vary throughout the year...), but airglow is the dominant source of sky brightness in the optical bands, so is of most relevance here.

[colinmlegg (Colin)]

Geoff, thanks for those links. I agree and I guess that's my point as well. In my experience it's rare to see no airglow and it does seem to have a large influence on sky brightness. Even up on the altiplano in Chile where you'd expect the darkest skies, there's often quite strong and variable airglow...at least the 3 times I've visited.

[alexch (Alex)]

Indeed, in light-pollution free skies, airglow and zodiacal light pose a significant background sky noise problem for professional astronomers.


The fisheye sequence was from the first night and it was free from significant skyglow in the beginning. It was then when I thought "wow, this looks darker than anything I have seen before". It was probably due to low humidity and good transparency too.

However you are absolutely right - it is impossible to compare apples to apples here. For example on those two memorable nights in the observatory on La Palma there was a significant airglow and the sky looked a little milky. In New Zealand it was so strong (following a big geomagnetic storm) that I think I saw the airglow patterns naked eye. I'll try to make a habit of taking circular fisheye images throughout the night at dark sky locations in the future and build up a database. (Do I need another camera?)

Cheers,
Alex

[pvelez (Pete)]

Have carpet burn on my chin

The best images I've seen in many a year

Thanks for that.

Pete

[FlashDrive (Poppy)]

Alex .... As usual ...nothing but the ' Best' ... Keep them coming ..!!
Love watching your Timelapse's.

Flash ..!!

[alexch (Alex)]

Col, Pete - thanks!
Mike, thanks for the IOTW!
Alex

[colinmlegg (Colin)]

Originally Posted by alexch

I'll try to make a habit of taking circular fisheye images throughout the night at dark sky locations in the future and build up a database. (Do I need another camera?)

I think you do Alex . So how many tripods did you take to WA? For plane flights I pack my DP S0 beam + 2 tripods (minus heads) and all clothes in a flexible 7 foot ski bag. Electronics (Laptop,MX2,bramper,etc.), cameras and lenses go in a carry on back pack or hand held bag. Anything else not breakable like tripod heads go in a 2nd suitcase. Worked nicely on the Chile trip, although I do feel like a slave to the technology at times.

[Phil Hart]

Originally Posted by geoffsims

Alex, Phil, Colin:

A quick note regarding airglow. You need to be careful when comparing the darkness of sites, even if using a handheld meter. Airglow fluctuations are quite complex. As seen in most time lapses, it is obvious to us airglow varies on short timescales (~minutes). There are also larger diurnal, and seasonal effects that come into play. Lastly, it fluctuates on decadal scales with the solar cycle. If you have access, there are many great papers in the literature about this.

We're on exactly the same page Geoff!

http://philhart.com/content/airglow-...dark-sky-sites

Just cause you have a small light pollution dome on one horizon doesn't mean the zenith sky brightness is objectively worse than the darkest of dark sky sites. Airglow is a very significant limiting factor. Alex's visual observations about what he could see matching the fisheye images is interesting though!

Phil

[jjjnettie (Jeanette)]

Brilliant work Alex.

[alexch (Alex)]

Originally Posted by colinmlegg

I think you do Alex . So how many tripods did you take to WA? For plane flights I pack my DP S0 beam + 2 tripods (minus heads) and all clothes in a flexible 7 foot ski bag. Electronics (Laptop,MX2,bramper,etc.), cameras and lenses go in a carry on back pack or hand held bag. Anything else not breakable like tripod heads go in a 2nd suitcase. Worked nicely on the Chile trip, although I do feel like a slave to the technology at times.

4 tripods + 5 heads, chargers, DP cart in a luggage bag. Then DP beam in a flexible Aldi ski bag and another suitcase for more gear and some personal items...
It was challenging but doable.

[ourkind (Carlos)]

Originally Posted by jjjnettie

brilliant work alex.

+100

[strongmanmike (Michael)]

Now, I guess that's quite a reasonable backdrop for night scape work....buuut hey my dead tree isn't too far behind .........

Great stuff Alex, some of you guys get to some awesome locations, I must say

If I may make one slightly negative comment and far be it for me to critique a master ... but many of the sequences were rather randomly jerky on my moniter, I have a good fast internet connection here at work too, is it me or the sequences...?

Mike

[alexch (Alex)]

Originally Posted by strongmanmike

Now, I guess that's quite a reasonable backdrop for night scape work....buuut hey my dead tree isn't too far behind .........

Great stuff Alex, some of you guys get to some awesome locations, I must say

If I may make one slightly negative comment and far be it for me to critique a master ... but many of the sequences were rather randomly jerky on my moniter, I have a good fast internet connection here at work too, is it me or the sequences...?

Mike

Thanks! Indeed that tree shows a lot of potential

I don't think it is you, Mike. But it is likely to be your computer, graphics card or Adobe Flash that make the timelapse stutter.

Try in a different web browser.

Cheers,
Alex