PixInsight Forum (historical)

PixInsight => General => Off-topic => Topic started by: dhalliday on 2010 February 21 06:12:22

Title: RGB vs LRGB revisited (Jim Misti data sets)
Post by: dhalliday on 2010 February 21 06:12:22

Cloudy weather forces me to use other data to play with.
I found an excellent site,with juicy data here;
http://www.mistisoftware.com/Astronomy/index_fits.htm

And in playing with it I believe I have satisfied myself that RGB (45 minutes)
http://www.flickr.com/photos/daveh56/4373360547/

 is as good as RGBL...(45/45 minutes)
http://www.flickr.com/photos/daveh56/4375899314/

Just for the record....
All I need now is a 32 inch telescope.... >:D

Dave

Title: Re: RGB vs LRGB revisited (Jim Misti data sets)
Post by: Carlos Milovic on 2010 February 21 08:20:37

Hi Dave

There is a slight improvement on sharpness with LRGB.
The whole idea behind LRGB was to safe exposure time, since the human eye is not capable of good chromaticy changes discrimination, one could use 2x2 or 3x3 bins with RGB data, and then take very long clear or luminance lights for the brightness information. Anyway, latelly many high resolution imagers take 1x1 RGBs... and L. So, that's where I can't find the point... At the end, is just a little more SNR.

Title: Re: RGB vs LRGB revisited (Jim Misti data sets)
Post by: Niall Saunders on 2010 February 21 08:32:59

I agree Carlos,

In my experience lately, a good set of RGB images simply does not benefit from the extra Lu data - If needed, time would be better spent acquiring an Ha channel, or just simply acquiring more, or longer, RGB subs.

Cheers,

Title: Re: RGB vs LRGB revisited (Jim Misti data sets)
Post by: Jack Harvey on 2010 February 21 08:39:03

Niall  Could not have said it better myself, as I have long been a RGB 1x1 advocate.  But in fairness I would point out a lot of very good imagers still collect Lum and do very nice LRGB.

Title: Re: RGB vs LRGB revisited (Jim Misti data sets)
Post by: Niall Saunders on 2010 February 21 08:45:38

I still tend to collect an Lu dataset - if time and weather permits. But Lu data is now lowest in my priority list. Bu data is top, just because it is so noisy, then Rd/Gn, then Ha if the object will benefit.

I think 2x2 binning has very little real purpose nowadays - 1x1 and a little bit more time on target will always give the best results. But, if yiu want to run 1x1Lu, and 2x2 RGB, then at least you will still be able to get a reasonable image.

There has been a good discussion on this whole subject over on the CCD Newastro Yahoo group - with excellent input (as usual) by Ron Wodaski. I'll need to re-read the thread and try and summarise what the various conclusions were.

Cheers,

Title: Re: RGB vs LRGB revisited (Jim Misti data sets)
Post by: dhalliday on 2010 February 21 08:49:34

Is it not possible to get BETTER SNR in RGB data,because longer exposures are possible..??
In other words,is this the weakness in Lum...?

CCD New Astro...????
Is this one of the better Yahoo groups for discussion...?
Are there others..?
Dave

Title: Re: RGB vs LRGB revisited (Jim Misti data sets)
Post by: Jack Harvey on 2010 February 21 08:50:19

Please do share those insights as Ron has been doing this a long time.