When does widefield become DS imaging?

[symesie04]

Just a quick question. There is currently a thread regarding imaging with the Hyperstar system and there are many coments suggesting it is ideal for widefield stuff. But as fast as it is and reducing as it does it still gives 560mm FL on the C11 in question. I have no idea what FOV it gives but would this FL not be Deep Sky rather than widefield. Guess what im asking what is widefield and what is Deep Sky?

[michael.h.f.wilkinson]

It is just a matter of definition. The hyperstar simply has a much wider field than the native focal length of an SCT. In that sense it is a wide field instrument. In professional instruments, anything with a degree or so is considered wide field.

[symesie04]

Hmmm i get you but is then that its just not its native FL that its widefield? If someone imaged with a frac at its native FL of say 500mm it would be considered Deep Sky would it not? Therefore if i was lucky enough to borrow one of those lovely 10m observatory jobs and reduced it to a FL of say a mere 6000mm would that be widefield? Would my images then really have to go into the widefield forum rather than deepsky 

[jambouk]

Before Michael replied, i was thinking anything more than a couple of degrees, say M31, would be my definition of widefield, but that is just based on feeling rather than knowledge.

Then there is dslr widefield, which could be 120 degrees i guess depending on your lenses.

But widefield imaging can still include and show detail of deep sky targets.

This will be an interesting thread to follow and see what others say.

James

[michael.h.f.wilkinson]

If I take an image of the Milky Way with my 18mm super wide angle on 35mm full frame it is certainly wide field, it is also certainly deep sky.

[jambouk]

Also depends on the chip you are using to image with.

A native 600mm f/l ed80 with the 0.85x focal reducer and an atik 314 give an image with a fov 1 degree x 0.8 degree. Swap that atik for a 11000 and the fov becomes 4.3 degrees x 2.8 degrees.

James

[Chris]

I think its a relative term:

i.e. I have a C8 (operating at f/7 1400mm focal length) to get upclose to those smaller objects for imaging. I wouldn't mind a 400-700mm scope for widefield imaging. however, if I owned for example a 6" f/5 Newtonian with a 750mm focal length I might want a 200mm lens for my widefield work and I'd use the Newt for my upclose shots.

its all relative, as mentioned all our amateur imaging is perhaps considered widefield compared to professional observatories images. 

Its all deep sky imaging unless your imaging relatively local objects like the planets and the Moon I think

[symesie04]

I get all that but in that case why do we have two different catergories for imaging? Surely its just a relative thing and therefore there should just be one section for imaging other then planetry. So as there isnt im guessing there must be some point either FL >< that makes it widefield or deep sky or a FOV that >< makes the difference?

[Alien 13]

My take on it is that any object within the milky way is widefield and external objects are deep sky.

Alan

[Chris]

So only galaxies and globs (by the skin of their teeth) are DSO's? and planetary nebs, SN rem's etc are widefield? is this right?

[michael.h.f.wilkinson]

Deep sky is anything outside the solar system. That is the accepted definition as far as I know.

[jambouk]

Yes, wiki supports that idea:

http://en.m.wikipedia.org/wiki/Deep-sky_object

James

[ollypenrice]

In terms of forum convention, and there is no hard and fast rule here, widefield implies camera lens imaging of constellations, the Milky Way or at least major parts of constellations. I think it's a fair distinction. Deep Sky tends to mean, conventionally, imaging through a telescope. It's nice, I think, for those imaging with short FL camera lenses to have a separate venue.

I sometimes produce widefield images via multi panel mosaics and using a focal length of around 500mm and a full frame camera. I post them in Deep Sky because they are telescopic images and can also be zoomed in on so that they are like any other short FL telescope image when at close quarters.

It's a bit like 'fast F ratio.' What does that mean? Well, it is never defined but most people feel that faster than F5 or so is 'fast.' Some migh say F4. But that is a reasonable agreement.

Olly

[Psychobilly]

I pretty much agree with Olly's interpretation...

Peter...

[KyleStoke]

my opinion and that is all it is, is widefield has a sense of perspective i.e a galaxy been deep sky but a galaxy in a star field been widefield, although that is not to say the widefield galaxy shot is not also deep sky.

hope that makes sense

[symesie04]

I definitely think  Ollys interpretation works best for me. Thanks gents.

[sharkmelley]

The original poster has put forward a false dicotomy.  The choice is not widefield vs deep sky.  Deep sky refers to the type of object and widefield refers to the field of view.

With a high focal length scope I could image Jupiter or the Ring Nebula.  The Ring Nebula is a deep sky object but Jupiter is not (because it is within the solar system) and neither of them would be widefield.  On the other hand with a Canon camera and a 50mm lens I could image either the Ring Nebula or Jupiter with its moons in the contect of a background constellation and they would both be widefield shots. 

Just my two pennyworth

Mark

[ollypenrice]

The original poster has put forward a false dicotomy.  The choice is not widefield vs deep sky.  Deep sky refers to the type of object and widefield refers to the field of view.

With a high focal length scope I could image Jupiter or the Ring Nebula.  The Ring Nebula is a deep sky object but Jupiter is not (because it is within the solar system) and neither of them would be widefield.  On the other hand with a Canon camera and a 50mm lens I could image either the Ring Nebula or Jupiter with its moons in the contect of a background constellation and they would both be widefield shots. 

Just my two pennyworth

Mark

In fairness to the OP this forum, like many others, has both a 'DS' and a 'Widefield' board so the false dichotemy starts there. I agree that it exists, though. Of course, these terms are not very sound if we look closely at them so we just need to interpret them on the basis of common usage and that, to most people, means on the basis of focal length.

Olly

[michaelmorris]

For me, it's a continuum.  One man's wide field is another man's narrow field - so any strict definition is pointless

[StuartJPP]

My take on a Deep Sky Object is an object outside our solar system that usually, but not always, requires long exposures to reveal. "Long" depends on the brightness of the object(s).

The focal length is irrelevant to DSO imaging, you just capture a different FOV.

Agree with above, wide is a relative term.

[RikM]

I've always thought of it in the same way Olly describes above. Like many, I use a range of focal lengths depending on the object. 1200mm FL Newt for small DSO, 750mm FL Newt for most things, 400mm FL Refractor for larger Nebs in narrowband, 135mm and 50mm camera lenses for 'widefield'.