The $64,0000 question!

[Les R]

Hi Les,

That Nexstar 6SE scope has excellent reviews as a visual scope - powerful and easily portable.  It would also be good for planetary/lunar imaging with a webcam or similar.

However, for deep sky imaging you'll probably find there's not much room for a camera on the back when imaging objects high in the sky.  Also it will be difficult to balance the scope with the additional weight of the camera. Although it has a guiding port (I believe), the biggest problem is that the mount is Alt-Azimuth instead of Equatorial.  This means that you will suffer from an effect known as field rotation unless you mount it on a wedge angled towards the pols star (which is awkward).  

When I first began imaging, I used a Celestron mount very similar to this.  Planetary imaging was no problem but for deep sky objects it made image acquisition difficult and processing a nightmare.  I think I was lucky that it didn't put me off imaging for ever!

Mark

lol..... and there was me taking my time and making informed judgments on a purchase! Dunno what quite happened there... I did it over a week ago! Yes I understand what you are saying re equatorial mount and ive seen all the comments re using a wedge so wont even try that. Not quite sure what the limitations will be (apart from the obvious ones already mentioned) and as I alluded, as long as the littlun gets to see stuff without a mountain of hassle, it would probably not be a bad thing.

So apart from the moon and planets..... what can I visually expect to see clearly? I do understand why the need is there for long time exposures for photos, but I'm still unclear if those objects are taken blindly and pieced together on a PC in layers!

Anyway.... I'm quite excited at getting it now.... Just a shame its a way down in Chippenham! And with the littluns football until midday, Im struggling to think when I'll be able to get it. I dont want it posted!

[MarkS]

So apart from the moon and planets..... what can I visually expect to see clearly?

The 6SE is an SCT type of scope and has a high magnification which means it has a much narrower field of view than a refractor.
Visually, the moon and planets will look superb.
Unfortunately the narrow field of view (0.8 degrees) means that a star cluster such as the Pleiades will not fit in the eyepiece.  You will be able to see a piece of the very bright Orion Nebula but it will look grey.  The Dumbbell and Ring Nebulae will look well defined (but grey).
Globular clusters such as M13 will look magnificent through that scope.
Galaxies will look like faint grey fuzzy blobs unless you are viewing from a very dark place in which cases you might even be able to just make out arms.
If you are viewing from somewhere less dark I would definitely recommend a light pollution filter in the eyepiece.

I do understand why the need is there for long time exposures for photos, but I'm still unclear if those objects are taken blindly and pieced together on a PC in layers!

I'm not sure what you mean about taking objects "blindly".  We spend a long time carefully lining up the telescope on our target and making sure the focus is perfect.

If you take one long exposure (say 1 hour long) then you may see the following problems:
1) The CCD pixels start to saturate so parts of the image become patches of bright white.
2) The image will be full of aircraft trails, satellite trails, cosmic ray hits etc.
3) A gust of wind might upset the tracking and you waste a whole hour of data.
4) You might not be perfectly aligned to the pole star so the image frame will gradually rotate during the hour, giving tiny star trails.

It is best to take 12 exposures of 5 minutes and add them together:

If these images line up perfectly then they can be literally added together by the computer.  We call this process "stacking".  However in practice they are added using an algorithm that removes the aircraft trails etc.  These things are easily spotted by the algorithm because they appear in one single image but not in the others.  The other slight problem is that the 12 images may not align exactly so the computer has to align the images before adding them.

So there you have it - a quick guide to stacking!

Mark

[Les R]

The 6SE is an SCT type of scope and has a high magnification which means it has a much narrower field of view than a refractor.
Visually, the moon and planets will look superb.
Unfortunately the narrow field of view (0.8 degrees) means that a star cluster such as the Pleiades will not fit in the eyepiece.  You will be able to see a piece of the very bright Orion Nebula but it will look grey.  The Dumbbell and Ring Nebulae will look well defined (but grey).
Globular clusters such as M13 will look magnificent through that scope.
Galaxies will look like faint grey fuzzy blobs unless you are viewing from a very dark place in which cases you might even be able to just make out arms.
If you are viewing from somewhere less dark I would definitely recommend a light pollution filter in the eyepiece.

OK, that makes sense. I always had the impression that without reasonable magnification, things would just be a mere spot in the viewfinder. I didn't think stuff would fill the viewfinder. So there is no colour anywhere (planets aside) visible and everything is down to filters and Photoshop in those marvelous colour images.

I'm not sure what you mean about taking objects "blindly".  We spend a long time carefully lining up the telescope on our target and making sure the focus is perfect.

If you take one long exposure (say 1 hour long) then you may see the following problems:
1) The CCD pixels start to saturate so parts of the image become patches of bright white.
2) The image will be full of aircraft trails, satellite trails, cosmic ray hits etc.
3) A gust of wind might upset the tracking and you waste a whole hour of data.
4) You might not be perfectly aligned to the pole star so the image frame will gradually rotate during the hour, giving tiny star trails.

It is best to take 12 exposures of 5 minutes and add them together:

If these images line up perfectly then they can be literally added together by the computer.  We call this process "stacking".  However in practice they are added using an algorithm that removes the aircraft trails etc.  These things are easily spotted by the algorithm because they appear in one single image but not in the others.  The other slight problem is that the 12 images may not align exactly so the computer has to align the images before adding them.

So there you have it - a quick guide to stacking!

Mark

Thanks Mark...... so in a briefer description, its purpose is mostly error correction which multiple images can detect, remove and enhance. And what I meant by "blindly" was thinking that images being made of things that were too feint to see properly and only visible with really long exposure on equipment more sensitive than our eyes.

Anyway.... I had a long drive down to Chippenham and back this afternoon to pick it up. See the motor drive working and visually, the optics looked fine. (I thought the lens was marked when I arrived, but it turned out it was just in need of a wipe.) It only came with a 25mm eyepeice the diaganal star and dew guard and t adapter.

The guide scope had been removed /lost. (I have a feeling the guy it secondhand and was just knocking it out! I may be wrong - just had that impression) Anyway - so I would need a guidescope for it I guess and an external power source, since imagine the internal batteries would last long.

[MarkS]

So there is no colour anywhere (planets aside) visible and everything is down to filters and Photoshop in those marvelous colour images.

Not exactly.  The colour really exists but unfortunately the human eye is not sensitive enough to see colour in dim objects.  The camera does not have this problem and images the real colour that is actually there.

There's an easy experiment you can do to prove this - go out into the garden in the dark and you won't see the grass is green or that the flowers have different colours.  Now take a long exposure (probably a few minutes) of the garden - you'll notice that the camera picks up the colour you can't see.

That's just like is for faint nebula and galaxies.  It's an amazing experience to see a grey fuzzy blob in the eyepiece and then take a long exposure of the same thing with a colour camera.  All the colours suddenly spring into life.  It is one of the joys of astro-imaging.

By the way, enjoy your new scope!!

Mark

[Les R]

So there is no colour anywhere (planets aside) visible and everything is down to filters and Photoshop in those marvelous colour images.

Not exactly.  The colour really exists but unfortunately the human eye is not sensitive enough to see colour in dim objects.  The camera does not have this problem and images the real colour that is actually there.

There's an easy experiment you can do to prove this - go out into the garden in the dark and you won't see the grass is green or that the flowers have different colours.  Now take a long exposure (probably a few minutes) of the garden - you'll notice that the camera picks up the colour you can't see.

That's just like is for faint nebula and galaxies.  It's an amazing experience to see a grey fuzzy blob in the eyepiece and then take a long exposure of the same thing with a colour camera.  All the colours suddenly spring into life.  It is one of the joys of astro-imaging.

By the way, enjoy your new scope!!

Mark

I know I didn't say as well as you've explained.... but that was what I meant! ie naked eye cant see the colours but long exposure pulls in more light. (Though I did think filters player a part!)

I need to make up a list of things I need to buy... or more to the point, details of the things so I can search online to buy secondhand.