ollypenrice

Yes, there is some confusion here. An OSC camera with the usual UV/IR blocker is producing the best 'luminance' of which it is capable. I think Zakalwe is mistaken, here. If you put a Luminance filter in front of an OSC camera you will get what you would get without it, an OSC image with an interpolated luminance layer.

Various programmes will extract 'luminance' from an OSC image. For instance, in Ps you can go into LAB colour mode and one channel is the Lightness. This is worth processing differently as Martin says. It is like processing a luminance layer. You push for detail, contrast, sharpness (another word for contrast really?). In the other channels (colour) you are interested in saturation and noise reduction but not detail. One mono advantage is that you can collect this layer faster by letting all of the pixels collect all of the colours simultaneously.

I may be wrong on some of this because I am not a technical bod as an imager but I think in essence a luminance filter is just a UV/IR blocker, no?

Olly

So my MN190 is gathering twice as much light in the same time on the same object as my ED120 ?

They are roughly the same FL 1000mm compared to 900mm the only difference is 190xF5.3 compared to 120xF7.5

If the focal length is (more or less) the same you can just directly compare the areas of the objectives, Pi R squared. That is your light grasp and it is concentrated onto the same area because the f length is the same. OK, central obstruction, but in round terms you are indeed twice as fast.

Olly

Yes, yes! This the whole point which people miss. If you use larger pixels for longer focal length scopes (and these can be software created pixels, they don't have to be hardware) they they are just as fast as their shorter focal length cousins. There is nothing magic about focal length - it is the aperture which determines how many photons you get. A 14" scope WILL blow a 4" away if you image correctly with it, whatever the focal length.

NigelM

Yes, and people imaging with C14s will often bin even the luminance on large chip CCD cameras. There is your equivalent of the coarser, faster grain. But you also have to accept that you can't just go on using a bigger and bigger chip. For one thing you can't afford to and for another the scope won't cover it!!

No doubt about it though, a well fettled F2 Hyperstar C14 is going to take a bit of beating.

Olly

For high dynamic range images (M42!!) this is essential and works beautifully:

Compositing 2 Different Exposures via Layer Masks

Don't forget Martin B's tutorials of course.

Olly

... which is pretty spectacular!

Folks are incredibly hard to convince, sometimes, that f ratio is what determines exposure time. I had an enquiry from a guy with a C14 who could just not believe that his enormous telescope was going to be very slow.

Olly

Fantastic work Olly, never seen this before. Wonder what this would look like full mosiac in Ha.

Rather like this!

Olly

http://ollypenrice.smugmug.com/Photography/Widefield-images-including/ALL-V1cropNEWLAMBDA/1094349246_cE8rH-X2.jpg

Brilliant, Keith. I almost wish I still lived in Wirksworth so I could cadge a peep!

I'm interested in what you say about angling the EPs in a little since I was thinking about this recently. I have a good pair of small 10x25s for brding but can't get to use the two eyes at very close focus because the images won't combine properly in my brain. However, in another pair they will. So I wonder how binoculars are made and what the optical and neurological issues are.

Olly

No need to apologise Olly... thats just the one I thought I had seen before...

Do you often have probs with CN ?

Billy...

No, not really but I find it too big! I'm a country bumpkin and so I don't often go to CN. The net can be iffy here.

Olly

Thats the jist of the CN one as well Olly...

Billy...

Ah sorry Peter, but I couldn't open it. I thought it might have been about that.

Olly

There was a thread suggesting that there is no point in usng thm visually if you have a wide 2 inch EP.

Olly

Awesome shot Olly! How did you combine the HA? Just used it as luminance or did you mix it with red?

regards,

Pieter

Thanks to all. Pieter, Ha was added to red at 100 percent in blend mode lighten and then at 30 percent in blend mode normal and finally at 10 percent as luminance. Still experimenting...

Olly

I have replaced the image with a tweaked version to improve colour balance in the shadows and star colour.

Olly

Sorry mods, BooBoo. Please remove! French keyboards are a nightmare...

Olly

An award winner in the making here Olly, it has that potential, so take it all the way. It is going to be a belter.

Hope you and the good lady enjoyed the show in Toulon by the way.

Ron.

Thanks Ron and indeed we did. Rob made us feel like royalty...

Olly

Stunning Olly - please excuse my ignorance - how did you get 8 point diffraction spikes??

Skill and daring!!

No, it is the iris in the camera lens from stopping down to around f5. I quite like it but if it looks dodgy on the final image I will run around the big stars in the TEC140 and Registar them in over the diffraction effects.

Olly

This is the top part of my 'Great Orion Project.'

The bright red giant is Betelguese. This is 2 panels at 85mm in a Samyang camera lens and Atik 4000, 15x10mins RGB per panel and 12 hours of Ha. The nebula is huge and very faint. It will need double the RGB time to stand up at full size but with a 6 panel final shot I may compromise on that! This is only a quick experiment.

Olly

Very good review. A guest was here recently with a double stacked Lundt 60 and I was blown away by seeing prominences so easily on the disc itself, let alone on the limb.

Olly

Convincing review, and by heck you did a good job on that cluster! Gorgeous. No really, it is fabulous, Nadeem.

Olly

He's a very good fellow, that Peter Shah!

Olly

Hi,

From a dark site there are many fine nebulae you can see, too. When winter comes, Orion is wonderful - M42/43/ but forget the Horsehead. In the summer the Milky Way offers a host of targets. Do you have good star charts? Computers are not much use because they blind you!

Olly

I'm one of the converted as well. TeleVue EPs never disappoint. I have four and would love an Ethos as well. On the big f4 Dob we use here the TeleVues give a cleaner edge of field than anything else I can remember trying. Newcomers to the scope are often surprized that there is no coma corrector in place and the mirror is of quite humble origins. Lesser Plossls do show coma.

Also TV are a lovely firm to deal with and helped me over the phone with an accident damaged Genesis.

Olly.

Ten thousand and TEN??? I'm quite old already, you know...

Olly.

I've just worked through creating star layers and improving stars. The instructions are, in my view, perfect and I cannot thank you enough. (When I was an English teacher I spent a long time thinking about 'instructions' and they don't get any better than yours.) They all worked first time for me and, I can tell you, that doesn't often happen with me at the keyboard!

One trick I have tried and found occasionally useful is to use a very light (1 pixel radius) Median filter when the stars are selected. It reduces slightly a tendency in my images for stars to have all their colour concentrated in a ring around the edge.

Many, many thanks for this godsend of a tutorial.

Olly.