how to take LRGB images

[adamphillips]

ok im pretty sure to do this you need to take separate images with all the filters and then combine them in photoshop.

but nowhere on google does it ever say this specifically. it has been so frustrating. anybody with any advice?

also if anyone has experience. how much exposure time do you like to give with each filter? how many images stacked with each? just curious.

[ollypenrice]

There is no single answer to this question. It depends on the target, the F ratio, the camara, the quality you want to reach...

Nor is it necessarily true that you combine channels in Photoshop.  I combine colours in AstroArt and add luminance and narrowband in Photoshop.

You do create separate red, green, blue and luminace (and narrowband) images first.

There really is a lot to learn and I'm sorry I can't give you a one shot answer but it takes me a week to take people through the basics to a decent level. Have you read 'Making Every Photon Count' by Steve Richards?

It might be a big help.

Olly

[adamphillips]

thank you for the help, I know the variables all depend on the scope and camera.

my biggest thing was to find out if you had to take the color images separately.

if there was any way to filter regular images into three separate channels and them combine them.

I have been practicing with photoshop, this guy puts up his raw images for you to download if anybody wants to stack them and process them yourself. http://www.rawastrodata.com/

ive had some pretty good results practicing but I don't get how some of his finished photos have a bit of color specically his m51. I can get a bit of color from his horsehead nebula images, but when I practice on his m51 mines is pretty much black and white.

im new at photoshop im sure there is plenty I don't know.

[ollypenrice]

No, you can only do LRGB by using those four filters in turn over a monochrome chip. This is widely misunderstood but the point of a luminance filter is that it captures red, green and blue simultaneously but without distinguishing between them. A colour camera does not do this. It captures, on a pixel by pixel scale, red or green or blue and can distinguish between them, but a quarter of its pixels capture red, a quarter blue and a half of them green. You can discard the colour information and call this a synthetic luminance but it is still shot through filters which block 2/3 of the light, so it has one third the data of a luminance filter for the same exposure. There is no free lunch. No chip can capture and segregate the colours in one pass. It can capture them all or it can segregate them but it cannot do both.

I continue to insist, with the maths in my favour, that LRGB on a monochrome chip is the fastest imaging system that can be acheived. It may not be the least frustrating, though!

Olly

[adamphillips]

so is a caonon 5d mark ii capable of taking the images. I know you would need the filters.

im just not sure what a monochrome chip is.

[Pete Presland]

i have only ever done (L)RGB planetary imaging, but i was a big improvement in the detail of my images. a lot of effort 3-4 AVI's and then 3-4 images for every final image, but well worth it. i find it fascinating the different detail that is shown in each channel, i imagine that RGB DSO's are equally amazing!

[johnrt]

so is a caonon 5d mark ii capable of taking the images. I know you would need the filters.

im just not sure what a monochrome chip is.

A monochrome filter captures in mono - black and white. No colour, that's why you use LRGB filters to make a colour image using a mono chip. You do not use colour and Luminance filters with cameras which capture in colour.

[RikM]

A 5Dii is certainly capable of taking astro images, just not LRGB. It takes RGB all in one go.

[adamphillips]

hmm, so a canon DSLR cant do it at all or can a setting be changed to mono?

[ollypenrice]

Yes, a colour chip has, in front of each pixel, either a red or a green or a blue filter. Any colour filter like this blocks 2/3 of the light, red blocking green and blue etc. A mono chip has no colour fitlers on it. You yourself put them in front of all of the pixels at once using a global filter. Discarding colour information from a colour filtered chip does not restore the 2/3 of the light blocked by the physical filters on the chip. The blocked light never reached the chip in the first place.

Olly

[Pete Presland]

hmm, so a canon DSLR cant do it at all or can a setting be changed to mono?

it does not matter what you do with the settings the chip stays the same.

[adamphillips]

I appreciate the help, I really do, but ollys answers are so technical (which I like) its hard to understand sometimes. is the answer yes it can be done or no, not at all? it looks like a no.

[Pete Presland]

you can not do RGB imaging unless you are using a monchrome chipped camera, whether it is planetary or deep sky objects. selecting a monochrome setting on your camera does not make the chip monchrome.

[johnrt]

I appreciate the help, I really do, but ollys answers are so technical (which I like) its hard to understand sometimes. is the answer yes it can be done or no, not at all? it looks like a no.

No.

[RikM]

No. Not without extensive physical modification of the camera, which I don't think is worth the effort.

[Davey-T]

Have you actually tried taking any astro images with your camera ? just stick it on a tripod aim at the sky and experiment, best to learn to walk before you try to run.

Use DSS  not PS  to process your images.

Dave

[adamphillips]

im totally new. I don't even have a lens for the camera yet. though I do have a setup to attach it to the telescope and use that, but im sure ill be frustrated for a while just using it that way. I know astrophotography is a huge undertaking, but I finally decided its not worth it to not even try.

[carastro]

Astro imaging is a minefield.  But basically if you are using a DSLR or one shot colour CCD camera you can take instant colour images.

If you are using a Mono CCD camera you need to take RGB using separate filters.  All the images will come out Monochrome and you need to combine them to create a coloured image.  This is easier said than done and it took me several months of rubbish results before I cracked it.  It was the combination of the RGB that I found the most difficult bit.  I came accross this video written by Anna Morris and found it extremely useful.  However my colours were then misaligned, and after much more stumbling around I found some software called Registar which will "align" all your coloured filters.  Registar is not free, but it has revolutionised the process and I highly recommend it.  

This is Anna's tutorial on combining colours:

http://www.eprisephoto.com/create-lrgb

I hope this is the sort if information you are looking for without being too technical.

Additionally it is also a good idea to take Luminance (clear) images as this will give the detail, and add this to the RGBG = LRGB.  anna also explains how to do this.  

Carole 

[brantuk]

If you own a dslr then I'd advise you have a go with that first. You will have a lot to do both before and after actually shooting the pictures - like e.g. refining polar alignment and tracking accuracy, refining focus, aligning, stacking, and post processing the subs. It would be a good idea to put ccd and LRGB aside till you've achieved all that first and had some practise.

Then all you have to do is change the camera and add the filters when you're ready to go forward - at least the other elements will have been sorted first.

[carastro]

Since the OP asked about taking LRGB images, I presumed he either has, or is planning to get a Mono CCD camera.

Mind you, I'd agree with cutting your teeth on a DSLR (which is what i did), far too much to learn if you dive straight in to a Mono camera with filters in my opinion, unless you just do mono to start with.  

Carole