Astronomy, Photography and Weather
November 30, 2022, 02:52:42 pm
Welcome, Guest. Please login or register.

Login with username, password and session length
News: IAA lecture programme continues alternate Wednesdays from September - an excellent programme of lectures- Queens University Belfast - Bell Lecture Theatre. Also keep an eye out for the Summer Events
 
  Home Help Search Gallery Staff List Login Register  
  Show Posts
Pages: [1] 2 3 ... 82
1  General Category / Photography / Re: Photos by Moonlight on: August 19, 2011, 09:37:27 am
Quote
I think long exposures like this will show noise, infact photos of some dark gray  clouds when taken to 50% even show noise
Hmmm ... setting "long exposure noise reduction" can make a significant difference ... but the fact remains that you've got to capture lots & lots of photons to reduce thermal noise. Noise reduction software can tidy things up but at the expense of fine detail in areas of flat tone, and some artifacts in high contrast areas of the image.
2  General Category / Photography / Re: Last roll of Kodachrome on: July 31, 2011, 09:13:13 am
I gave up on Kodachrome when they discontinued K25 ... never liked the colour balance of K64 (when projected), though yours posted seem to be OK - scanning "to blame"? As for K200, well the less said the better. But I still miss K25.
3  General Category / Weather & Atmospherics / Re: 2011 Noctilucent Cloud Season on: July 27, 2011, 03:38:51 am
Jul 26/7 - clear all night & pretty transparent, in fact it almost went dark!!!  NLC negative again. Season over?
4  General Category / Astronomy & Space / Re: In Preparation For Night Time Observing on: July 24, 2011, 05:26:33 pm
Quote
Although I doubt if the weight of one or two people walking on a structural concrete slab is going to transmit through to the concrete pier causing vibration
You'd be surprised ... don't forget a scope can be sensitive to disturbances of less than half an arc second.

Quote
a structural concrete slab would be a much better support for a shed and roll-off roof.
There are other issues here. Frost heave is more of an issue with a large area of slab. Best foundations for a shed are trench founds running under the walls. A wooden floor supported by the walls is good but a free standing wooden floor is better. IMO when the floor is kept reasonably dry covering it with an old carpet is a good way of creating a dust & vermin proof seal with the pillar - the carpet will also help protect your eyepieces from damage when dropped.
5  General Category / Astronomy & Space / Re: In Preparation For Night Time Observing on: July 24, 2011, 09:27:29 am
Quote
is there a concrete pad to stand on? It does wonders to keep your feet out of the damp grass, though it can be rough if you drop an eyepiece!!
Yeah, that's the issue. Also you don't want the footway to be transmitting vibrations to the pier. IMO a wooden decking with a hole in the middle to clear the pier is better than concrete though you do need to be careful to avoid having vermin use the "shelter" so provided.
6  General Category / Weather & Atmospherics / Re: 2011 Noctilucent Cloud Season on: July 24, 2011, 03:53:45 am
Clear sky from midnight on last night (Jul 22/23) and partially clear especially on the northern horizon tonight (Jul 23/24). No trace of NLC detected.
7  General Category / Photography / Re: Poppy Fields on: July 11, 2011, 01:16:18 am
Quote
3 coach loads of kids !!.... are you crazy
Depends how hungry the liions are Wink
8  General Category / Weather & Atmospherics / Re: 2011 Noctilucent Cloud Season on: July 10, 2011, 03:16:46 am
Unexpected mostly clear night with bright NLC in the NNE (stretching from NNW to just E of NE). Substantial low cloud on the horizon but I managed to grab this shot:


Jul 10, 0144 UT. Canon 40D, 17mm, 2.5 sec at f/5.6, ISO 400.

The "bright" cloud stretching across the top of the frame is tropospheric cirrus cloud, probably a smeared contrail.
9  General Category / Weather & Atmospherics / Re: 2011 Noctilucent Cloud Season on: July 03, 2011, 02:39:03 am
July 02/03: Very bad interference from "nasty low cloud" but from 0100 - 0130 UT there was obvious NLC, exceptionally bright swirls visible through & between patches of stratocumulus to an altitude of 20 degrees between North by West and North North East (solid cloud to the west of that).
10  General Category / Weather & Atmospherics / Re: 2011 Noctilucent Cloud Season on: June 29, 2011, 01:54:44 am
Jun 28/29: Much interference from tropospheric cloud (socked in completely from 0030 UT) but NLC seen, a bright band low on the northern horizon from 2300 to 2315, more extended but fainter swirls & bands in the NNW gradually fading from 2345 onwards.
11  General Category / Weather & Atmospherics / Re: 2011 Noctilucent Cloud Season on: June 28, 2011, 03:10:41 am
Jun 27/28: Sky clear!!! NLC negative.
12  General Category / Weather & Atmospherics / Re: 2011 Noctilucent Cloud Season on: June 14, 2011, 10:17:42 am
Quite a nice display last night, with the Sun so far north the NLC was noticeable even at local midnight. The best display seemed to be around 0115 - 0130 UT after which the brightening twilight robbed the NLC of its full splendour.

The main display here was just to the west of north, with no activity east of Capella. Time lapse images show the NLC moving at an apparently fairly slow rate from NE to SW. Three sample images:







Canon 40D, 17mm, ISO 400, various exposures (8 sec to 5 sec) at f/5.6 (evaluative auto exposure used)
13  General Category / Weather & Atmospherics / Re: 2011 Noctilucent Cloud Season on: May 31, 2011, 12:50:02 am
Poor conditions tonight with some high cloud & lumps of decaying shower cloud but NLC positive at 2330 (May 30th) - a smooth band / arc about 3 deg high in the north, less high to the west & east of north, the arc is about 2 deg in height. Very faint indication of rays from the northern horizon stretching up towards Cassiopeia but I think these are high cloud (cirrostratus) illuminated by twilight rather than auroral in nature.

Edit: Hmmm, reviewing images I'm no longer so sure ... maybe the arc is just shadowing by cirrostratus. Judge for yourself.

2011 May 30, 2334 UT.
14  General Category / Weather & Atmospherics / Re: Summer Forecast 2011 on: May 18, 2011, 09:55:57 am
I have very little faith in long term / seasonal forecasts.

Here's mine, for summer 2011 in Northern Ireland:

Some days it will rain for some of the time. Some days the sun will shine some of the time. Average temperatures in June, July and August will exceed those in December, January and February respectively. Lying snow is unlikely but not impossible.

 Grin
15  General Category / Photography / Re: AEO II Lightning Trigger on: May 18, 2011, 09:52:06 am
Umm - I don't know how the unit operates, but with cameras there is a delay between the shutter press and the shutter opening, this is partly due to the autofocus mechanism & partly to the mirror having to get out of the way. Try using manual focus (prefocus to infinity for lightning) and using the mirror lockup function, this should improve the response time by a large factor.
Pages: [1] 2 3 ... 82
Bookmark this site! | Upgrade This Forum
SMF For Free - Create your own Forum

Powered by SMF | SMF © 2016, Simple Machines
Privacy Policy