Click here if you are having trouble logging into the forums
Privacy Policy |
Please read our Terms
of Service | Signup and
Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User
Samir Kharusi
scholastic sledgehammer
Reged: 06/14/05
Posts: 988
Loc: Oman
|
|
We had some discussion as to whether the LPS-P2 should be better for blue reflection nebulae, however, for the pale blue of M45, both seem to be quite useless, click here. Nevertheless, the LPS-P2 could still be more effective on the more violet nebulae like the Running Man, if somebody wishes to undertake more field tests... For my full comparo click here.
--------------------
Bored? Peruse my website:
http://www.samirkharusi.net/
|
WarrenS
scholastic sledgehammer
Reged: 03/04/08
Posts: 897
Loc: Orange County New York
|
|
Samir, limiting magnitude 3.5 is pretty bad, horrible and useless in fact for astronomy and astrophotography. My CLS filter works very well on blue nebulosity in magnitude 5.6 skies, 70 miles north of NYC. I think the correct point is not that the CLS and LPS-P2 filters don't work but that we should get our butts OUT of big cities and someplace a little darker! Many people use these filters on all sorts of nebula with many excellent results, just peruse this and the CCD imaging forums. They can't perform miracles! You might be giving people a misimpression. 
--------------------
Warren
Astro-Tech 127EDT
Celestron Onyx 80ED
Astro-Tech Field Flattener
C8 (circa 1983 Orange Tube)
Atlas EQ-G, Orion SSAG
Canon 135mm F2.8
Canon 40D, Astronomik CLS clip filter
Leica, Minolta binos
|
Tonk
Post Laureate
Reged: 08/19/04
Posts: 4358
Loc: Leeds, UK, 54N
|
|
How do you get 3.5 skies! From the midle of a football pitch with the lights blazing ?
I live near a bad bad bright city - but mag 3 skies are reserved only for "Millenium Square" at the city center with its arrays of 100 foot high pole lights and white paving stones - the night clouds are a dazzling white above this spot and can bee seen 40 miles away!. Mostly its mag
4.5 and moving up to to 5.2 were I live
I would thought a CLS etc would be a useful help in the 4.5 to 5.5 mag zone. I'd personally give up below 4
--------------------
Televue 85, GM-8/Gemini, Canon 40D (unmodded), Canon 450D (modded w/Astronomiks clip-ins - UV/IR, OWB)
Coronado SM60/BF10, Baader Herschel Wedge
Leeds Sky Clock Ripon Sky Clock
|
Samir Kharusi
scholastic sledgehammer
Reged: 06/14/05
Posts: 988
Loc: Oman
|
|
Definitely did not mean to say that these filters are totally useless. In my experience they work very well at VisLimMag 4.5 or better, basically anywhere you can see a hint of the Milky Way. This led to my strong recommendation for the LPS-P2 for such outer suburbia/country skies when shooting almost anything. The discussion referred to was on choosing between the LPS-P2 and the CLS for M45, the LPS-P2 being basically more white-light-like and goes further into blue/violet, while the CLS leans more towards a duo-tone. My expectation was that the LPS-P2 "should" do better on reflection nebulae while the CLS should be better on emission nebulae. Looks like M45 is a lot tougher on filters than I expected. Anyway, at my VisLimMag 3.5 there isn't much to choose between them. At my home even the much narrower Astronomik UHC is not narrow enough, even on emission nebulae. It's true narrowband territory, in my experience for filters narrower than 10nm  I need several hours of filtered integration time to get even emission nebulae semi-decently:
--------------------
Bored? Peruse my website:
http://www.samirkharusi.net/
|
Samir Kharusi
scholastic sledgehammer
Reged: 06/14/05
Posts: 988
Loc: Oman
|
|
Quote:
How do you get 3.5 skies! From the midle of a football pitch with the lights blazing ?
Well, they have just installed a bunch of street lights yards from my house. I live in a desert environment; skies always blue (pale because of haze). So at least I hardly ever have to worry about clouds. When the sky has been washed by recent rain my skyfog gets as dim as VisLimMag 4.5 in the early morning. Now that winter is here I thought I'd have a go at this test on M45 since conditions looked better than my average and even the Unihedron Sky Quality meter indicated Mag 17.6/sq arc-sec (roughly VisLimMag 3.6). I really ought to concentrate on Lunar/Planetary...
--------------------
Bored? Peruse my website:
http://www.samirkharusi.net/
|
Tonk
Post Laureate
Reged: 08/19/04
Posts: 4358
Loc: Leeds, UK, 54N
|
|
17.6 - I'd be crying  . I moved house 4 years ago to get from 18.6 to 19.6 (with horizon views of ~ 40 miles ) - then i bought a trailer so i could get to 20.8 at weekends. After that i have to travel 150 miles to get to the real dark stuff on the Scottish borders - or a bit further to get to the Galloway Forest Park (which is being assesed for international "dark sky park" status this weekend - woo hoo - will be 3rd one after two in USA)
--------------------
Televue 85, GM-8/Gemini, Canon 40D (unmodded), Canon 450D (modded w/Astronomiks clip-ins - UV/IR, OWB)
Coronado SM60/BF10, Baader Herschel Wedge
Leeds Sky Clock Ripon Sky Clock
|
Nils_Lars
Post Laureate
Reged: 01/04/08
Posts: 3459
Loc: Santa Cruz Mountains , CA
|
|
I tried my CLS on M45 and I didnt like what it did , I felt like it cut out a lot of the Nebulosity.
--------------------
Erik
Orion Atlas Self Hypertuned (EQMOD)
Orion ED 80
Williams Optics VII reducer
Celestron 8" SCT
Orion Starshoot Autoguider
PHD guide
Canon 400D Hap Griffin Mod w/Baader filter
Astronomik clip-in LP filter and 12nm Ha
Stilleto CVF and Bahtinov mask
Tamron 75-300mm&28-80mm lenses
NexImage webcam
http://www.flickr.com/photos/31986095@N05/
|
Psyire
scholastic sledgehammer
Reged: 06/24/07
Posts: 980
Loc: 55* North
|
|
I shot M45 through my IDAS LP2 filter recently and it worked out alright. (just needs more time) I do know that the CLS and Deep Sky filters are not good for any blue reflection nebula though such as this one. I don't agree that the LP2 should be grouped into the same catagory though as it's a broader filter.. It also helps that you don't have to deal with the Light Pollution as much in post processing when using it..
Info: 40mins of 8min subs, Canon 450D, 80mm scope F/5
--------------------
Celestron CPC 1100 XLT, Sky-Watcher Equinox 80ED
TV 31T5-Nagler, 8&13mm-Ethos
EarthWin Binoviewers w/ 24mm Panoptics
Elusive Photons.com
|
s58y
Postmaster
Reged: 12/12/04
Posts: 5509
Loc: Eastern NY
|
|
I've shot M45 3 times through an IDAS LPS filter, twice from about 85 miles north of NYC and once 100+ miles to the northwest. Under the moderate light pollution, the IDAS filter seems to work well for M45.
Here is the M45 shot from 100+ miles from NYC, with some moonlight and also artificial light pollution about equal to the natural skyglow (meaning the sky is about 2x brighter than it should be -- SQM-L = 21.24 to 21.40):
here
(I have no idea how this would look with no filter at all.)
--------------------
Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
|
Samir Kharusi
scholastic sledgehammer
Reged: 06/14/05
Posts: 988
Loc: Oman
|
|
That's a beautiful capture! I believe that to compare filters one needs to have, deliberately, insufficient integration time, so that noise levels and limitations to stretching are obvious and thus lead to a clear-cut preference. I did shoot 30+ mins integration with each filter, expecting that to get noisy stacks I may have to cut back to, say, circa only 10 mins each. Easy enough to do in post processing but I was quite surprised that the full 31mins integration still showed hardly any nebulae, for both filters. Mind you, 31mins at this site is equivalent to only a 46sec single exposure at a truly dark site, 4 Mags darker.
--------------------
Bored? Peruse my website:
http://www.samirkharusi.net/
|
|
15 registered and 14 anonymous users are browsing this forum.
Moderator: Charlie Hein, knuklhdastnmr
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 249
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: 