Atike 383 LRGB Image Quantities

[Jkulin]

Hi All,

I'm just switching over from my Nikon D800 to using my Atik 383 with LRGB filters

Is there a general rule as to how many luminance images to take versus RGB filter images, for example with M31 would you shoot twice as many luminance images as opposed to RGB, I'm trying to get a feel for what scripts to establish on first light hopefully on Saturday, with the light pollution in my area I can just about pull 10 min subs with my Nikon but that was using a LP filter, which I am hoping to get away with not using now.

Thanks in advance for your help.

[geordie85]

If your imaging area suffers from light pollution, you'll still need to use a LPF unless your just imaging in narrowband. 

As fur subs, at the moment I'll usually image for an hour in each rgb channel then the rest of the night in luminance, then the same again the next night. Atleast this way I have some data to play with if the weather doesn't play ball for a while again.

If I know the weather will be fine most of the week, I'll spend an entire night on each channel. You'll want more luminance than rgb as that's where your main details come from. 

[Jkulin]

Thanks Geordie. much appreciate the advice, we have been lucky to get one night a month at the moment let alone 5 in a week :-(

OK, I appreciate that I will need a LPF in some skies, especially to my East, so I just need to work out the best location to fit it, as I don't think it will fit directly onto my FW before the T adapter and wondering whether it will cause vignetting, I'll fathom that out.

So really working on your suggestions I should work on the ratio of 3 to 1 as a general guide and if I can get it better than that then all good?

[geordie85]

What scope are you using? What size LPF do you have? I ask because most 2" filters will screw onto the end of a flattener/ coma corrector. 

Lack of Clear nights is why I shoot 1 hour red, 1 hour blue then 1 hour green at the moment. 

I try to get atleast double luminance to colour.

[Jkulin]

Hi Geordie, it's in my sig, 8" F8 RC and a SW 80ED Pro, I'm using Astronomik 2" CCD CLS and a 2" IDAS P2 Light Pollution Suppression Filter, the IDAS lets a bit more light through but both have been effective.

Although I have FR for both scopes I don't use the Astro Physics one on my RC as I haven't needed to yet as the RC is really good at producing flat fields, on the 80ED I use the FR all the time.

If it goes clear this weekend then will try and grab some tests and see which works better.

Thanks for your advice

[johnrt]

Imaging in semi urban skies as I do I believe the key to a good quality final image is in how much Luminance you gather. A plethora of sins can be hidden under a quality Lum. So I aim for 20 of each RGB filter, normally at 5 mins a sub, binned x2. Then I gather as much Lum as I humanly can, normally in 10 minute subs at full resolution. I aim for anything upwards of 60 subs (10 hours).

If you are cursed with some light pollution as I am a decent LP filter stacked in front of your LRGB works wonders, I have an IDAS LP2 that sits in front of all my colour filters.

My secret mantra when constructing LRGB is; Behind all of my pleasant LRGB images lurks an ugly RGB image! It's all about the Luminance for me!

 

[Jkulin]

Thanks John, blimey that is some capture times, so in general you are working on 15 hours minimum in total, so about a 5:1 ratio?

What's your process, do you do all the RGB in one night and then over a succession of nights the L and process the L separately to create masters in PI.

THE CCD process is quite different from DSLR so need to go back to the processing in Warren Keller's book.

[johnrt]

3 minutes ago, Jkulin said:

Thanks John, blimey that is some capture times, so in general you are working on 15 hours minimum in total, so about a 5:1 ratio?

What's your process, do you do all the RGB in one night and then over a succession of nights the L and process the L separately to create masters in PI.

THE CCD process is quite different from DSLR so need to go back to the processing in Warren Keller's book.

I try to get the RGB in one night if possible, but if not then it's over multiple nights. I then re-visit as many times as needed to get the Luminance. I tend to shoot the Lum first then finish off with RGB.

This one chalked up the most exposure time, about 22 hours (over a couple of years!)

 

[Jkulin]

Beautiful images John, just looking at your website and Flickr, I would give my eye teeth to be 1% as good as you, simply stunning

[geordie85]

I'm on my phone so can't see people's sig's. I'd screw your LPF onto the end of your fr/ ff to be most effective and it won't be load bearing.

I completely agree with John, that every lrgb image hides an ugly, blurred rgb image. Well that's atleast true for all of my images. Remember that your not looking for detail in rgb, just colour. I'll usually blur my rgb data before adding luminance to help with all the nastiness and noise.