Surely nudging a dob limits what you see?

[wolfytom]

Tell me if I'm wrong...

To see more detail on Jupiter surely I need a stationary image so that a smooth flow of light falls onto the retina and allows the brain to process detail into a more complex image.

If the planet is always moving then the brain is having to process far more information and we see less detail?

Will I always see more detail through a scope with autotracking than the same scope without?

(The biology described above could very well be garbage!)

[FraserClarke]

Your eye has a 'frame-rate' of about 25-30 Hz, and so only things happening faster than that are going to get blurred out. In fact, many people say they get a better image by gently 'tapping' the side of the scope to give it some movement -- though I think this is more applicable to very faint objects, because the faint parts of eyes are specialised to detect movements (i.e. AAAAAH! TIGER!!)

The drift of the image across the field of view is not very noticable. You'll be limited far more by things like natural seeing variations, wind buffeting the scope, etc.

[leenewtoastro]

if a car drives past slow you see it in all its detail still its just moving.

so the detail will be unaltered it will just pass across the fov slowly is all

when its gone out of fov you nudge to bring it back again. simples

try to think of it as jupiter is still and the earth is rotating

[Talitha]

"Will I always see more detail through a scope with autotracking than the same scope without?"

Not necessarily. Before getting my 16" Dob, i was really worried about needing to constantly nudge it, so i did a bit of experimentation with my f/10 8" LX-10. I'd study an object with tracking, and then without tracking. Whether the tracking was on or off, i never lost details on objects, except to the fluctuations in seeing.

But since i'd been using tracking scopes for over a decade, the constant manual adjustments interrupted my concentration a bit, but that was a 'me' problem... one which was quickly overcome when the Dob arrived in July.

[leenewtoastro]

a goto dob tali?

[Moonshane]

personally I think the answer to your question is yes, or is it no??

the problem with this sort of question is that it depends what you mean as always. for me the key reason for buying a larger dob is to get more detail on other things than planets.

larger aperture means more resolving power so a larger scope will generally outperform a smaller scope (or at least have the potential to see more detail) on most objects if the viewing conditions etc are the same. however, I have two dobs (see signature) and have found that the 6" outperforms the 12" on planets although I prefer the 12" for everything else. this is possibly due to the increased contrast of a smaller secondary and slower focal ratio.

I have found that at higher magnifications, it's perfectly possible to track objects but like you, feel I am losing some detail with the constant nudging and subsequent (albeit usually short in duration) settling of wobble. this is much less in the 12" which is one reason I prefer it generally.

as a result I am making a equatorial platform http://stargazerslounge.com/diy-astronomer/127311-equatorial-platform-dobsonian-telescopes.html - cutting starts tomorrow.

this in principle will provide me with a simple RA tracking system which should hold eg a planet in view for 10-20 minutes at high power. I anticipate this will allow me to see more detail but time will tell.

this board will work with both my scopes and I may even make two once I have proved the first one.

personally I'd prefer to avoid goto on the whole but I recently viewed a totally stationery Jupiter through a mate's tracking scope and was hooked.

[leenewtoastro]

MS are you going to do a picture diary?

i love pic build diarys

[Moonshane]

sure am. starting tomorrow with parts and cuts.

[Beulah]

Excellent Shane, looking forward to it.

[wolfytom]

I have found that at higher magnifications, it's perfectly possible to track objects but like you, feel I am losing some detail with the constant nudging and subsequent (albeit usually short in duration) settling of wobble....

... a simple RA tracking system which should hold eg a planet in view for 10-20 minutes at high power. I anticipate this will allow me to see more detail but time will tell...

...Personally I'd prefer to avoid goto on the whole but I recently viewed a totally stationery Jupiter through a mate's tracking scope and was hooked.

A Ha! (as Alan Partridge would say) My point exactly.

I don't possess a scope yet, this is all part of my purchasing deliberation! The problem is another complicating factor rears its ugly head every day!

[Talitha]

a goto dob tali?

That's one of the options i looked into before ordering the 16", but i'm one of those oddballs who actually enjoys starhopping. Tracking would be nice, but TBH the simplicity of nudging appeals to me... guess i'm just an old-fashioned geek.

[Mr Spock]

Having tracking allows you to take advantage of those fleeting moments of steady seeing.

Some 30 years ago I had a 8" on an equatorial 'nudge' mount. Although I did some good work with it, it eventually fell into disuse. Tracking is just so much more convenient and less fiddly.

[NGC 1502]

but TBH the simplicity of nudging appeals to me... guess i'm just an old-fashioned geek.

Well that applies to lots of us, including myself Ed.

[DrNeb]

Your eye has a 'frame-rate' of about 25-30 Hz, and so only things happening faster than that are going to get blurred out. In fact, many people say they get a better image by gently 'tapping' the side of the scope to give it some movement -- though I think this is more applicable to very faint objects, because the faint parts of eyes are specialised to detect movements (i.e. AAAAAH! TIGER!!)

The drift of the image across the field of view is not very noticable. You'll be limited far more by things like natural seeing variations, wind buffeting the scope, etc.

our eyes do not have a frame rate of around 25-30hz.

common misconception. we can see a lot higher than 30fps.

60hz is the "sweet spot" per eye for non flickering observation. however the human eye can detect a difference way above that.

the new 3D tech (or old tech on nvidia graphics cards) for example MUST be at least 120hz - 60 per eye when using active shutter.

[acey]

Tracking definitely has its advantages but just look at all the thousands of happy dob users around the world, past and present (e.g. William Herschel).

[leenewtoastro]

Having tracking allows you to take advantage of those fleeting moments of steady seeing.

Some 30 years ago I had a 8" on an equatorial 'nudge' mount. Although I did some good work with it, it eventually fell into disuse. Tracking is just so much more convenient and less fiddly.

i thought goto's were no good for tracking? only good to get you there?

[John]

i thought goto's were no good for tracking? only good to get you there?

Once they have got you to the object, alt-azimuth GOTO's track it well enough for visual observing, but not accurately enough for deep sky imaging I believe.

I'm a "nudger" myself although I occasionally use a driven equatorial mount. I've invested in ultra-wide angle eyepieces which means it's much easier to keep objects in the FoV, even at high power. It sort of becomes second nature after a while

I prefer simple setups with no power, alignment and other complexities. I need to move my scopes around quite a lot so I've tended towards simple alt-azimuth mounts. If I had a permanently sited scope then no doubt it would be driven.

[lookhigh]

I must say ive always wanted a dob but the constant nudging put me of a bit because i have 2 kids that always want a look.

But then along come affordable GOTO dobs.

Didn't take long to make up my mind.

So the answer is, You probably will get too see objects for longer with tracking but the quality of the image should be the same.

[acey]

The 72-inch Leviathan - the largest telescope in the world during the 19th century - was an undriven alt-az (i.e. "dob") aligned due south, with enough side-to-side motion to allow objects to be viewed for a maximum of about 30 minutes as they went past the meridian. Too big to nudge, it was moved by ropes and pulleys with the assistance of a couple of workmen. Magnifications of over x1000 were used. It was with this scope that spiral structure in galaxies was first discovered, so the system obviously worked well enough for Lord Rosse and his assistants.

[LukeSkywatcher]

They must have had great seeing back then in Ireland to be able to use 1000X.

[acey]

No better than we get nowadays - but the 19th-century astronomers always went for very high power, because they were hoping to resolve stars in "nebulae". I think with the 72-inch they mostly viewed at magnifications of a few hundred.

[perrin6]

Just to be a pedant, a Dobsonian mount is not just any undriven alt-azimuth mount but a type first built by John Dobson. They are generally sturdy & made of low-cost materials such as wood with plastics such as teflon and formica-substitutes for the bearings.

[umadog]

Your eye tracks the planet to keep it in the fovea as it slowly moves through the FOV. You won't see fewer details, therefore. In other words, "just look at it"

[virtualpilot45]

The 72-inch Leviathan - the largest telescope in the world during the 19th century - was an undriven alt-az (i.e. "dob") aligned due south, with enough side-to-side motion to allow objects to be viewed for a maximum of about 30 minutes as they went past the meridian. Too big to nudge, it was moved by ropes and pulleys with the assistance of a couple of workmen. Magnifications of over x1000 were used. It was with this scope that spiral structure in galaxies was first discovered, so the system obviously worked well enough for Lord Rosse and his assistants.

Where can I get it? :-)

[DrNeb]

The 72-inch Leviathan - the largest telescope in the world during the 19th century - was an undriven alt-az (i.e. "dob") aligned due south, with enough side-to-side motion to allow objects to be viewed for a maximum of about 30 minutes as they went past the meridian. Too big to nudge, it was moved by ropes and pulleys with the assistance of a couple of workmen. Magnifications of over x1000 were used. It was with this scope that spiral structure in galaxies was first discovered, so the system obviously worked well enough for Lord Rosse and his assistants.

fantastic post! thank you, very interesting.