which lens and filter to buy?

[merlinxlm]

Hello everyone, could some one point me to the right direction regarding, filters and lenses for my Celestron C6-S? At the present, I have a 9mm, 25mm and a barlow X2, plus a moon filter. I'm interested in DSO's, I saw the Orion nebula the other night and could clearly see the nebulosity and the main centre stars, but no colour, do I have to buy a nebular filter to see any colour? I was very exited to see my first DSO through my new scope. I was using my 25mm with the barlow, I found that it showed more detail than the 9/25mm lenses. What would be the best set up for observing DSO's? Am I expecting to much out of my scope to see DSO's? Sorry to ask such simple questions, but I'm new to using telescopes.

Thank you.

[russ]

Sadly you'll never see colour in M42, no filter will help. But you can enhance you view you already get. A narrowband or OIII filter will help bring out more of the detail in the M42 and other similiar Nebulae. I use an Orion Ultrablock 2" and find it greatly enhances the view.

My only reservation would be the aperture of your scope. These filters need good aperture to work best. 150mm maybe okay? I know the view in my 80mm apo is better without the filters but much enhanced in the 12.5" newt.

Russ

[Agent M27]

This is my first post and am on the edge of buying my first telescope!! My main focus would be seeing DSO's as well. I have already decided on an Orion XT10 Dobsonian. You mentioned aperture was a key factor, will 10" provide any color? Why is it that no color is visible from Orion? Is it due to our eyes not being able to collect the light from said DSO's? Thanks in advance! I love this hobby!

Cheers

Joe

[John]

This is my first post and am on the edge of buying my first telescope!! My main focus would be seeing DSO's as well. I have already decided on an Orion XT10 Dobsonian. You mentioned aperture was a key factor, will 10" provide any color? Why is it that no color is visible from Orion? Is it due to our eyes not being able to collect the light from said DSO's? Thanks in advance! I love this hobby!

Cheers

Joe

I can see hints of pale green in M42 (the Orion Nebula) through my 12" dobsonian but only hints of it.

I think you are right that it's the limitations of our eyes as receptors that limit the colours we can detect in deep sky objects.

The trouble is we get so used to seeing these fantastic colour images of these objects that we forget that they have been filtered, captured, stacked and processed in a way that our poor old eyes simply can't emulate.

I still feel a real thrill though seeing a faint object directly, even if it is often just a colourless misty patch !.

John

[jgs001]

The lack of colour is down to the components of the eyes that are used. The colour receptors in the eye are not very sensitive to dim light. When your eyes adapt to darker conditions, the colour receptors (cones I think) shutdown and far more sensitive (rods I think), but greyscale sensors become active. This means that when you are dark adapted and able to see the faint stuff, you won't see colour, unless the scope has a big enough aperture to gather enough light to keep some of the colour receptors active. As it's possible to see colour in the brighter stars, I guess that there are instances where there is enough light available to activate the cones, but not enough to stop the rods, so leaving your eyes sensitive. (I may have made some of that up, whilst I did Physics to degree level, my biology is not very good, although this crosses over between the two to some extent).

The colour comes through in imaging, because the camera's sensor is able to gather far more light and is sensitive across the entire colour spectrum (for colour cameras anyway), aided by using longer exposures. So whereas your eye is seeing only the light that's available at that instant, the camera gathers the light for some time period (30 seconds or more) and collects it all together into a single frame, and then as John says, stack lots and process them.

HTH

[Doc]

Colour can be seen through a scope but it's very limited. It's nor llike the photo's you see on this site.

Through my 16" dob M42 is has loads of colour, very green. Can see a touch of blue in the M45. A few planetaries are blue or green.

So it is possible but only with bigger apertures.

[FLO]

... When your eyes adapt to darker conditions, the colour receptors (cones I think) shutdown and far more sensitive (rods I think), but greyscale sensors become active. This means that when you are dark adapted and able to see the faint stuff, you won't see colour, unless the scope has a big enough aperture to gather enough light to keep some of the colour receptors active.

Someone explained to me once that, in effect, the eye/brain stops processing colour and switches to image intensifier mode.

I remember thinking 'hey, that's pretty cool!'

[jgs001]

Good explanation Steve, it is pretty cool. Until, that is, some so and so decides they need a cuppa and turns on the lights in the kitchen, which happens to be just as you're looking up from the scope to write something in your note book, and it hurts, a lot...

[FLO]

I bought some red goggles (Astro-Engineering, similar to welding goggles) so that I could retain my night vision when popping in for a cuppa or to use the bathroom. I felt a right twit when wearing them but they did work. Broke them a while back and haven't got around to replacing them.

[Jarndyce]

I've only had my C6-S for a short while, and had two views of M42, but both were clearly green.

In fact on the first viewing, I was absolutely knocked out by just how clear and how much colour in the Nebula was visible. I just wasn't expecting that. Second time was fainter, but there was a certain amount of high cloud around.

With a 20mm EP the trapezium was beautiful and crisp and different densities of green were visible in the surrounding nebula.

As my first DSO through my new scope, it was a spiritual experience.

As my 11 year old son said; "Wow....."

[ZOG]

It must be my old eyes <) I have never seen colour in M42 or any other nebulae for that matter, but who cares ? The fact that I can see these things, knowing how far away they are is amazing. Don't get me wrong, I love the work the imaging guys do, but for me it's the difference between seeing a pic of a lion in a book, and seeing one live in Africa.