Blue Mountains - Katoomba Airfield 5th Oct

[mental4astro]

Hi all,

Rod is making available the Airfield to us for Saturday 5th of October.

I for one am in serious need of a good photon fix. And with the weather warming up, we shouldn't freeze so readily.

The Spring sky is galaxy time. Fornax, Sculptor, Grus and their buddies put up some real beauties and some real tough nuts to crack. The tough ones are also some of the closest, with several close by dwarf galaxies that have low surface brightness being a real challenge.

M31 and M33 are also placed at a better time of the night. Good seeing conditions sees these monsters display extraordinary detail. I've seen M33 as a lovely faint naked eye object at the Airfield. I'm hoping this October sees these conditions revisit us.

If you haven't been to the Airfield, access is via Medlow Bath, the next village past Katoomba heading west. The screen shots below will show the route from Katoomba. Note that the last 3km along Rutland St leading to the Airfield is unsealed. It was graded earlier this year and is still in good nick, though some ruts and some erosion gullies are forming. So take it easy on this stretch. It is an easy 2WD unsealed road.

The Airfield is at 1000m above sea level. This altitude is its greatest asset to overcome the glare of Sydney's sky glow. And as there is no farmland around, and rainwater readily drains off the poor soils up here, dew is not frequent.

The Airfield though is totally BYO. There is no power up there, so you need to bring what ever power requirements you need. Facilities are basic, there's loos, tank water, and the office building has a combustion heater and we are welcome to stay overnight there too, with the office available to sleep in too.

Please note that when entering the Airfield, take the left track of the fork - there is no access to the setup area if you head straight. Head past the "No Entry" sign and turn right up the hill to the set up area off the main runway. This airfield is only operational during the day for aircraft, so we won't have planes or helicopters land on us.

Being a dark site, and with our eyes dark adapted and many folks taking photos, please be very considerate of this and be careful of using white light. Red lighting is the norm at a dark site. A welcome courtesy is to warm folks that you will be turning on a white light BEFORE you do so. Don't have a red light? Easy, three of four layers of red cellophane over your torch will produce what we need. Red cellophane can be had from newsagents, florists and many $2 shops.

Any questions, please ask.

Mental.

[MortonH]

Hope to be there

[AstroJason]

Thanks Alex, at this stage I am unsure if I will be able to come along this month. Hoping some plans change so I can join you guys.

[AG Hybrid]

See you there. Might try and squeeze both my scopes in this month.

[killswitch]

Weather should be good.. ill be there

[Camelopardalis]

Great - should be there too. Hope the weather is a little kinder in the cloud and wind departments, don't care about the cold ;)

[Manav]

Out of town for the long weekend :(

[Wavytone]

Alex, I'm only a maybe - could be out of town with other commitments.

[mental4astro]

Madbadgalaxyman has started a thread on these dwarf galaxies that are satellite galaxies of the MW. A link to this resource can be found here (http://www.iceinspace.com.au/forum/showthread.php?p=1018914#post101891 4). I'll give some time to clocking these this coming new Moon. From my reading, some of these are really hard to make out.

[eclipse]

Depending on the weather as usual we will try and be there.

Les and Deb

[lacad01]

Sounds great, need to clear the cobwebs off the gear :)

[AG Hybrid]

Hmm International Fleet Review is 5th October as well. Not sure if I'll be coming now.

Anyone fancy Hargraves Lookout tomorrow night? Weather looks to be good. Moon wont rise till 1 AM. At least we would get a few good hours in.

[Wavytone]

The thought has crossed my mind, this afternoon looked superb. Watch the Mt Boyce AWS to see if the wind drops in the afternoon - if it's still a howling westerly at 3pm I'll say no.

Speaking of which the seabreeze reached that far this afternoon :)

[andyc]

Won't make it this month - but the up-side is I'm planning a 3 night trip to the Southern Highlands, so weather permitting I'll have some dark skies to get the scope into! Hope it's clear for all who go this month :thumbsup:

[AstroJason]

Yeah, I'm up for Hargraves tomorrow night Adrian if the weather is good

[Camelopardalis]

I've got other commitments during the day tomorrow which might make it a bit of a close call :(

[AG Hybrid]

Alright Jason. I'll meet you out there, mate. 7 Timer suggests its acceptable. It reckons it will cloud over at 50% at 1 AM. Moon will be rising by then anyway. Better then missing out a dark sky visit for the month.

[killswitch]

I can probably do tomorrow night weather permitting.

I forgot about the international fleet review as well, i really wanna see the F/A-18 flybys

[AG Hybrid]

Sweet! Yeah that fleet review might be a once in a life time thing. Should be a great day out and fire works in the evening.

[AG Hybrid]

Ill be leaving between 3:30 and 4:00 PM. Get there before sunset.

[AstroJason]

Cool same here mate

[Camelopardalis]

7Timer is now saying 1/8 cloud at 19:00 :(

I'm going to chuck a minimalist setup in the back of the car and I've got to head out. If I can escape early I'll see you guys up there!

[AG Hybrid]

Yeah think Ill just run my AR102 for some rich field work tonight. While the galaxy center is still high in the sky early on.

Sorry to hi-jack this part of the thread Alex.

[mental4astro]

:mad2:

:lol:

[Wavytone]

Waaaay too windy - it's blowing 35-45 knots at Hargraves.

Not only enough to blow your scope around, very unpleasant and I don't expect it will drop soon. Seeing will be crap too, so I'm staying put. Might be ok if you're doing wide field photos.

Have fun Dunk, I think you'll be back sooner than you planned !

[AstroJason]

Guys, little bit put off by this wind. If its this windy in Sydney and Hargraves is known for being windy on the best of days... how bad is it going to get at Hargraves tonight?

[AG Hybrid]

yeah I think this is a bad idea. Looks like we will probably have to let it go this month.

[AstroJason]

Yeah guys, I'm out. Not feeling the greatest anyway. If anyone does go, enjoy, but make sure you strap yourself to the mountain!

[Steffen]

I had planned to help out at the public viewing at UWS Werrington observatory tonight and later go to Linden, but my wife got me into a social "thing" that I can't seem to weasel myself out of.

Hearing the wind howl outside I don't think we would have had much fun at the scopes anyway…

The 5th October date is locked in, though :thumbsup:

Only poor weather or bush fires can ruin that for me.

Cheers
Steffen.

[MortonH]

Looks like there are a couple of bushfires in the Springwood area today. Best to stay home.

[rogerco]

Negative, no bush fires on the Blue mountains so far today, thank god seeing we are having wind gusting to 120 kl/h on occasions. Just left my mid mountains fire shed open day, it's been pretty quiet.

[Camelopardalis]

"Luckily" I got back late so have just been practicing my polar alignment in the garden, synscan assisted, especially useful since there's some big trees blocking my view to the south, and no Polaris :( Gotos within the FOV at 165x so far.

Btw, the breeze dissipated as I started setting up, only the occasional and more gentle gust now. Is this sort of wind typical for this time of year or freak? Back in the little island we typically would only get this sort of wind when it's cold (and it's cut right through!), relatively speaking, so about half the year :D

Roll on next Saturday!

[Wavytone]

Hi Dunk, august - September usually bring the "Windy Westerlies", these should ease up as the increasing warmth from the sun generates sea breezes with enough strength to block the westerly at ground level. On the coast during the afternoon these are the "black nor'easters" familiar to sailors on the harbour.

Around mid summer the wind strengths generally drop off and by January a high percentage of days/nights should have good weather with winds under 15 knots, the usual pattern is for this to persist right through autumn.

[Camelopardalis]

Interesting stuff, thanks!

[Camelopardalis]

Oh and I got bitten last night, right on my wrist :( I was wearing trousers and a long sleeved fleece top. Pesky critters :mad2:

[mr bruess]

Weather should be good.. i might be there if my car gets fixed.
Petrol will be expensive.

[mental4astro]

You're gonna LOVE summer up there - mozzies are around, & so too are dozens of tiny bats that flutter, chirp & carry on around us whilst they feed on the mozzies we attract, :D. Then you age 10 years & crap yourself when one of these nocturnal areobats streaks past between the focuser & your nose, & you see a shadow shoot past & feel the the wind from their wings blow on your face! :eek: Flaming excellent stuff!

If petrol money is a problem, bring a mate along & share the cost of fuel. I do that when I give Peter a lift.

[Camelopardalis]

So not only are our predators crawling around on the ground with their 8 or no legs, and we can't see them when nature calls :D , but they're buzzing and flapping all round our heads getting in the way of the views? Sounds like paradise ;)

Given my garden "experience" this weekend, I'm guessing we must be getting to aerogard season. One other thing the garden reminded me...the light pollution is awful, we're really spoiled up in the mountains! Well worth the drive IMO

[MortonH]

I love bats buzzing around. Used to get them in the UK as well.

As long as they don't fly inside my OTA!

[Camelopardalis]

Yeah we used to have a few bats swooping between the trees in the UK too, a few though not the mass I see flying overhead after sunset here :eyepop: so long as they don't take me scope :D

Looks like I'm going to have to invest in those mozzie unfriendly layers early than I anticipated... I discovered another mini-vampire bite on the back of my foot at ankle level this morning, must have got that from last nights outing :mad2:

[MortonH]

I got some strong insect repellant as part of my vaccinations, etc. before going to India for work a couple of years ago. Haven't been bitten when I've been using it. Will check the brand later.

[MortonH]

or you could get one of these
http://www.iceinspace.com.au/forum/showthread.php?t=112690

[AG Hybrid]

Due to work commitments I think my schedule has cleared up and I probably wont be going to the Fleet review. I should be able to make it to Katoomba.

[Camelopardalis]

LOL only covers the face though ;)

[mental4astro]

Well, looks like I'll be bringing my little GSTAR camera along for the ride too. In another current thread, I offered to bring it along so folks can see how a video stream looks like, and the offer has been jumped on. So if you'd like to try it in your scope, let me know, or have a look while Dunk and Steffen have a go with it.

[absolut]

Providing we don't get any bush fires and the weather is good I'll be coming along Sat night!

I'd love to check out the camera too Alex, dying to see how it looks! :D

I think I'll be bringing some sleeping gear this time, been close to nodding off on the way home... not a good look really!

Crossing my fingers for some awesome seeing! :)

Rob

[Camelopardalis]

Score :thumbsup: what's the focal length Alex?

[mental4astro]

The focal length is that of your telescope. My focal reducer is 0.5X, so half that of your scope. The lenses I can bring are 16mm, 50mm and 125mm. I can also bring that piggyback bracket for your C8 as the camera is very light and the lenses are not heavy either. I really don't want to bring my 114mm scope with its 500mm focal length as the whole exercise will then ruin my own intensions for the night. Man, I haven't done a DSO sketch is such a long time...

[mental4astro]

Special request

I'm finally getting around to making a series of sketching how-to videos. One of these I would like to make as a time lapse of myself at the eyepiece doing a sketch. Does anyone have a suitable camera that I could borrow? I'm guessing that it could need some type of IR illumination too. I've got a very sturdy tripod it can be mounted on. I mentioned time lapse as a sketch can take, depending on the DSO, from 1/2hr to three hours.

Anyone coming to the Airfield able to help?

Mental.

[Camelopardalis]

Ah ok, so it comes with its own lenses and just needs a tracking host...that's easy enough, I'll have 2 (maybe 3) scopes on board both on goto mounts.

Camera wise, I'll be bringing my point-and-shoot - it can manage up to 15 second exposures but there's no remote shutter on it. Not sure if that's any use?

[mental4astro]

Hey Dunk, no the camera doesn't come with its own lenses. It just comes with a 1.25" adapter. The lenses I'm bringing, one I bought a CCTV lens, the others are SLR camera lenses that I've bought an adapter to couple to the camera. This is the camera I'm bringing:

http://myastroshop.com.au/products/details.asp?id=MAS-071C

Time lapse is taking not a single long exposure, but a film that slowly records a long spans of time, & when played back the action is greatly accelerated. Like those docos showing a flower grow in a matter of seconds, not days.

[Wavytone]

Hi Alex,

I'll bring my LX5 and tripod, it shoots beautiful video in low light and can run exposures to 4 minutes (overkill). Timelapse is a no, unless the frames are triggered manually (IMHO not hard if the duration isn't excessive).

Regarding illumination, I can't do UV or IR. But what I know does work well is a low soft light from a single LED torch with a tissue over it to act as a diffuser (which I also happen to have).

[BenM]

Won't be able to make bitterly disappointed!

[Camelopardalis]

Got it :thumbsup: sorry.

[malau]

What time is the event start normally? Im planing to head up with my friends

[mental4astro]

G'day David,

There is no actual start time. For that matter, there's no finish time.

The Airfield will be open all day for aircraft, and we can arrive whenever we like. If you do arrive early for astro activities, make your arrival known to Rod, the Airfield manager. He will be able to guide you to where to stay on site until the Airfield is clear of its daily aircraft activity. There are aircraft kept at the Airfield, so Rod can get upset if you arrive and don't make your intensions known. You can say you're there for the astronomy session, or you can take your life in your own hands and say you're there to meet Alex :P.

I'm hoping to get there before sunset. I'm aiming for between 5pm and 5:30. This will give me plenty of time to set up, have a bite to eat and enjoy the cloak of darkness come over the Airfield.

Rod makes the Airfield available to us without asking for a fee. He is only too happy to be able to share this enormous site with ourselves and our hobby. To say thank you, we give him a slab of his favourite brew, for which the hat gets passed around to share out the cost of the brew.

Look forward to meeting up with you and your friends.

[GeoffW1]

Hi,

We have illness here, so I'd best not plan on attending.

It's bad luck, I had intended to come along and look at planetary nebula, this time of the year is propitious.

All the best for the night, see some of you at Wiley Park High.

Cheers

[vic4loc]

Sorry have to miss out this month, heading to Coona over the long weekend.

Victor.

[Camelopardalis]

OK, I confess, I bought a new filter... that shouldn't have provoked the clouds to the extent of the current forecast, which isn't looking pretty :mad2:

[Oleg]

Forecast is not that bad actually, according to weatherzone in Katoomba:

6pm Mostly cloudy 16°C WNW 19km/h
9pm Mostly clear 13°C WNW 17km/h
Sunday, October 6
12am Mostly clear 12°C WNW 18km/h
3am Sunny 8°C W 9km/h
6am Mostly cloudy 12°C WNW 17km/h

Have you noticed it will by Sunny at 3am? :D

[MortonH]

Unfortunately "mostly" clear simply means less than 50% cloud cover. Currently the prediction is 45% cloud cover at 9pm and 34% at midnight.

[AG Hybrid]

45-35% cloud cover... I could live with that. 7Timers not looking bad.

[Camelopardalis]

I've noticed a trend - the prediction for the cloud band is slipping forward, so it'll be interesting to see what they're predicting in the morning.

What happened to the run of clear nights we had? I though my cloud dodging days were over :D

[eclipse]

We can't make it today, enjoy yourselves.

Les and Deb

[AG Hybrid]

7 Timer is saying it will get better later into the night, But really bad early evening. Obviously to test our patience.

[Camelopardalis]

Looks like my chances of seeing the Veil with the big scope evaporated into clouds :(

What's the plan? Go or no-go?

[mental4astro]

It won't be the first time an evening's started poorly, then changed into something spectacular. Could be ok a bit overcast - I can show those who wanted to try out my little GSTAR video camera before the sky clears & the serious business can start. Could be a late one.

I'll speak to the Oracal, and also check forecasts, & say by 3pm.

[Camelopardalis]

Sweeeeeet....I'll load up da 'mobile and await the flag dropping...

[Wavytone]

Alex,

Right now (10:15 am) it's clear to the east of me (northern beaches) but thin high cloud is moving in from the west, doesn't look good.
But the Katoomba webcam shows grey sky over the mountains - thin overcast.

Check the webcam before leaving.
Go/no-go will be 5 pm for me.

The BOM satellite photo (9:30 am this morning) shows bands of clouds with some sucker holes, extending far enough west to wipe out tonight and sunday night, so I really doubt its going to be much good.

[AG Hybrid]

Gonna bring me lots of food and drink. I think Ill be out till 2-3 AM for this one. I need a decent dark sky fix.

[killswitch]

Ill now be coming... fingers crossed for clear skies.

Also a reminder that its double demerit tonight.

[Wavytone]

Well I'm pulling the plug - I reckon it will be overcast - high cloud deck moving in.

The fireworks are a safer bet.

[MortonH]

Yep, fireworks for me too.

[mental4astro]

Just got off blower to Rod. At the moment things are fine with some high cloud & wind coming from west. Mate of his just landed his plane at Parkes where is is beaut. Here's the kicker - forecast says will deteriorate late arvo, but Rod's nose tells him it will be fine.

I'm packing car ready to go, & will call Rod at 4pm to determine my final choice. For now, at 1:40pm, I getting ready for the night. Last word at 4pm.

[Wavytone]

Ok... will try the webcam at the last gasp.

[Camelopardalis]

Fireworks shmireworks :D

7Timer is predicting 3/4 cloudy at 22:00. That's better than this morning and good enough for me. I'm loading up and awaiting the signal.

[Steffen]

I'm going to check back here at 4pm then. That leaves just enough time to pack the car and head off.

Cheers
Steffen.

[mental4astro]

Sorry folks, NO GOOD TONIGHT.

Another year gone to crap observing wise on the eastern seaboard.

Until next time,

Mental

[AG Hybrid]

Ahh well damn.

Although perhaps we should not throw this long weekend away so quickly.
On an interesting side note. Tomorrow night looks good according to 7 timer. Looks like nearly all night is clear. If the airport is closed. Anyone for Hargraves Lookout?

[AstroJason]

I was about to say the same thing Adrian. What about tomorrow night?

Alex, would we be able to get access to the airfield tomorrow night instead? If not, I'm up for Hargraves tomorrow night.

[Camelopardalis]

Gutted :(

I'm up for tomorrow night, car's already loaded :D

[Steffen]

Tomorrow sounds fine, if we are permitted.

Cheers
Steffen.

[AG Hybrid]

my car is already loaded too haha. Alright cool a few for tomorrow night. If we can't get the airfield we can meet at Hargraves then.

[Camelopardalis]

(From acropolite's reminder in general chat)...and with the clocks going forwards tonight, there's a chance I might get there before sunset :D :D

Btw, what's that all about, at this latitude?!? It's not like there's a huge variation in sunrise/set times, like back in Blighty :confused2:

[MortonH]

I'll try for tomorrow. Not sure yet, though.

[rogerco]

Just to let you know a total fire ban day has been called for tomorrow:

http://www.rfs.nsw.gov.au/dsp_content.cfm?CAT_ID=1109

the Blue Mountains is area "4" on that map.

Haven't looked at the weather forecast but that usually means, high temperatures linked with low humidity and wind. There are not any fires of concern in the Blue Mountains at present, the one that still shows at Springwood is a few trees burning within the burnt area. That of cause is not to say that if the wind gets up it might not break out.

Good luck, I might come up for a drive and try a few night scape shots :)

[mental4astro]

I just got a call from Oleg. He doesn't have access to the net on his phone & missed the note for tonight, so he's at the Airfield now.

Guess what? IT'S CLEARED UP!!!!

Bloody hell! Rod's nose was right, & forecasts wrong. I should have gone with the Oracal...

If anyone would like to join Oleg, make tracks. Just say G'day to Rod.

Cleared up here at home too <sigh>.

Mental.

[MortonH]

Doh!

[absolut]

Bugger!

I'm 2hrs drive + the time it takes to pack my car + finish eating dinner... no chance of getting there leaving this late.
Guess I'll try again next month. :(

Rob

[AG Hybrid]

Cant join us for tomorrow Alex?

[malau]

Tomorrow still perhaps a "go"?

[Wavytone]

Mmm... last night from Sydney, the sky cleared for a while during the fireworks, around 8pm but soon after the high cirrus returned and the stars disappeared.

Tonight could be better.

[mental4astro]

Wavy, you should have gone back out at 10pm - crystal clear. Took my 8" dobbie out at midnight - fantastic seeing. So good I was able to see the LMC & the SMC from home naked eye! Something I hadn't been able to do in a very long time.

I doubt I'd be able to make it tonight to Hargraves. For those that do, I hope you get cracking good conditions.

[MortonH]

Don't think I can get away tonight :sadeyes:

[Camelopardalis]

Chaps, I'm heading out that way in about an hour to do some sightseeing (what do you call tourists over here, btw? We have all kinds of names back home ;) ), the scope is already loaded in the back of the car. I feel it's tempting fate leaving an SCT in the back of a car all day :D

If anyone is up for Hargrave's tonight then I'll see you there! I'll be aiming to get there to see the sun set and will check in here closer to the time so I know whether or not to set up :D

[csastro25]

Hi all

I'm Claude. I live at wentworth falls. I'm a keen astrophotographer and was wondering who do I chat or call about joining a local astronomy club up here. I am a member of the western Sydney amateur astronomers group. But it's to far to travel for the meetings. I do now and then get to linden to observe but I rather somewhere new and different. I heard about this place here in katoomba but didn't know who to speak to

If possible. Can someone contact me on 4757 1413 or 0429318726

Much appreciated and would like to meet some keen astronomers aswell

Thanks

Claude

[killswitch]

Dunk, keep us updated on the weather. BoM says its very windy around Katoomba.

That shack at the lookout worked quite well as a wind breaker though.

[mental4astro]

Hey Claude,

Set you a PM. Speak soon.

Alex.

[AG Hybrid]

I'm still looking to head out to Hargraves. Probably leave home at about 4 PM. Should get there about 5:30.Hopefully the weather holds. The shack and those trees make good wind breaks yeah.

[AG Hybrid]

7Timer says a bit average early on and clearing later into the night. Just like it said last night-which turned out to be great.

Fingers crossed.

[AstroJason]

Im about to start packing the car. Pretty sure it will be a good night. Will leave 4ish too

[Camelopardalis]

In Leura at the moment, there's a fair breeze but it's forecast to drop after sunset.

[killswitch]

Okay packing now and leaving soon then

[Camelopardalis]

Wow, what a night of many firsts :thumbsup: the wind couldn't blow out our enthusiasm :D

[AG Hybrid]

Turned out to be a fantastic night. By 9 PM all horizons were clear. A bit windy but we lasted till 1:30 AM. Saw a lot of new objects. Mostly galaxies for myself. Jason, Ed and Dunk saw Triton for the first time. A great buzz picking up that one.

[Camelopardalis]

Yeah look forward to more galaxies next time, thanks for all the pointers chaps :thanx:

Also good (for me) to have the C11 earning its living and feel much better about it outshining the 8 :)

[MortonH]

Did you get a look at the Veil with the new OIII filter?

[AG Hybrid]

yeah we checked it out. We had a prime view of it. Very bright and large.

[Camelopardalis]

Had a nice view of it, but in the faint fuzzy frenzy I forgot to compare the OIII with the NPB :screwy:

There was noticeably more detail, but then the C11 catches almost twice the light of the 8.

It'd be a really interesting challenge to pick a small number of nebulae to compare one night, I think collectively we have quite a selection of scopes, filters and eyepieces...

[rocketboy]

Good evening all,

I went with Oleg to the airfield on Saturday. Saw quite a few objects.. I cannot shake the image of Jupiter and what I assume to be some of its moons from my mind.

From my camera set up for timelapse:

http://youtu.be/6axVpkHd70E

First sequence, sun sets. Second sequence, I adjust exposure and sun light fades as Venus appears. Third and fourth sequences, Milky Way travels overhead (fourth sequence includes tree tops for context).

Last two stills, just two of the best exposures pulled from the 500 stills making up this film.

For those who are interested:
500 images, 20 second exposure once every 30 seconds (via an Arduino). ISO 3200, custom white balance (for uniformity), 18-55 kit lens. All JPEGs (naughty boy) and no post processing save for level/contrast adjust on last two stills in the film.

Regards,

rocketboy

[ManUtdFans]

Hi Rocketboy, the milky way galaxy looked not obvious, was that because no post processing?

[rocketboy]

Hi, yes I think that post processing would make a large difference. And shooting raw if I had a memory card big enough for 3-4 hours.

As it is, JPEGs use lossy compression and so noise reduction didn't do much when I had a play last night. Also tried DSS to stack images on the mac with wineskin, but not very stable.

[killswitch]

Heres a photo from Sunday night at Hargraves

Jason took a timelapse that night....waiting to see it :)

[AstroJason]

That looks awesome Ed, really looks like you're "shooting" the stars with your death ray! Its coming, Kate keeps hogging the laptop to watch TV shows. I should get some time to process it tomorrow!

[mental4astro]

Ed, ya not a good shot. You missed the Horse by a couple of degrees above its back...

Lovely pic, mate. I've always found it intriguing how a laser beam just "stops".

[ManUtdFans]

I shot a photo like yours, the galaxy colour was a bit dull, not colourful.
Not sure how to make it outstanding (I got the RAW as well)?

[Wavytone]

Hi Alex, yes it is an interesting effect.

To an observer on the ground, the beam is visible within the "planetary boundary layer" which is the air from the ground up to a few hundred metres, maybe a thousand metres - which is full of microscopic aerosol particles. This layer typically extends to the cloud base which is usually 1500-2000 metres above sea level, and at this point there is usually an inversion layer. The air above the inversion is much cleaner, and the beam effectively disappears above that interface.

Hence its not uncommon to see a laser pointer apparently reaching the cloud base but not beyond that.

Over the upper Blue Mountains the cloud base is usually 1500-2000 metres above sealevel (having measured it on my paraglider), but can be higher in warm dry weather.

[Camelopardalis]

Excellent pic Ed, love the laser :thumbsup:

[mental4astro]

Wavy, that then explains why the beam reaches out further when aimed to the horizontal, and 'shortens' when pointed up vertical.

Thanks mate.

[Wavytone]

Yup... I've noticed the same too especially in the mountains when the cloud base is low. Took me a while to figure out why, considering that the runway length (for example) is much longer than the height to the cloud base. Similarly the distance from Hargraves across the valley to the west is over 10km.

Over Sydney itself the inversion layer is often only 100-200 metres above ground, on a humid night low clouds will form at this level.

[AstroJason]

Hey guys, I posted some of my shots from Hargraves and the time lapse sequence here (http://www.iceinspace.com.au/forum/showthread.php?t=113079). Enjoy!

[Camelopardalis]

Wow, nice!

[malau]

any meeting tomorrow night?