Tracking by hand.

[NIGHTBOY]

Now I know I posted this in another section but I felt it needed to be in here.

Has anyone ever made a cogs and handles type of devise for a dobsonian? Imagine 2 handles that you could slowly wind to move the scope on both axis. Would be pretty handy I'd say.

[cgarry]

I know a few people who have made their own equatorial platforms.  Far easier I think!

Cheers,

Chris

[Cornelius Varley]

I doubt you would be able to control the mount smoothly enough for imaging. 

 Equatorial platform http://www.budgetastronomer.ca/index.php?page=eq-platform

[NIGHTBOY]

Right ok. So would I be right in thinking that objects will only go through the viewfinder from bottom right to top left (with the scope dead still) so this mounts sort of on the wonk to counter act that??

[Freddie]

In one continuous AVI you could just let the image drift through the FOV, move the scope, drift through FOV etc etc. The stacking prog (AS!2, regi) will then take care of the stacking or you could put it through PIPP to crop and drop any frames with no image before stacking.

[NIGHTBOY]

You try that using a 3x Barlow Freddie! Not an easy task!

[nightfisher]

Dobs are not imaging scopes, best bet would be A-focal

[Stainlesssteve]

You could make a very large barn door tracker:)

http://davetrott.com/inventions/double-arm-barn-door-drive/

[NIGHTBOY]

I'd love a left/right and up/down handle, same sort as you'd find on a milling machine, would be awsome.

[kirkster501]

Why would you want to?  Dobs are wonderful visual devices - I love mine. But they are not designed for AP.  You could possibly get such a contraption to work in theory after much expense and frustration.  But then, "in theory" you could go from Northampton to Milton Keynes on a work commute walking on your hands - perfectly possible.  Theory and practicality are two different things!

[sidelight]

Seems to me this is a hobby built in part by people pushing at the bounds of what you can't do.  It would be a pig to achieve in the tolerances and robustness needed but the first thing I thought of was Gary Honis' binocular chair  http://ghonis2.ho8.com/garysbinochair1.html and a barn door tracker on top.

[NIGHTBOY]

It would be good for looking at planets on high mag, you can't really take the detail in because you constantly have to bump the scope round, if you could slowly wind handles to follow it then that sound like a good idea to me.

[Steve Ward]

That's what EQ mounts were made for , much easier to save your pennies for an HEQ5Pro and save a lot of time , frustration and heartache ... 

[NIGHTBOY]

Yes but the amount of threads I've seen on problems with aligning them etc seems like another big headache just around the corner. I'd just like to point my dob at whatever, sit, focus, smoothly and slowly wind and follow.

[NIGHTBOY]

Oh and save around £500 in the process.

[Moonshane]

might be OK for planets but not for long exposures as the problem would be field rotation. i.e. you can move in alt az all you like but this will not account for the rotation on the Earth's axis. even if you keep the object central there will be rotation around the centre in the various images you take unless you use an equatorial based mount (inc barn door trackers, eq platforms and of course standard eq mounts).

[Steve Ward]

If you want to image successfully , whether it be planets or DSO's you need an Equatorially aligned platform ... Period ... 

Unfortunately there are no cheap or easy routes to Astrophotography , it's a fact that we have all had to face up to , were there cheap and easy routes we would not be here now advising you on the matter but would be telling you how to get 10 minute exposures with a Dobsonian .... 

Sorry if that sounds a little harsh , but there's no point in sugar-coating the facts.

You would do worse than acquire Mr Richards "Making Every Photon Count" , widely regarded as the first port of call on the Astrophotography adventure , available from the sponsors I believe .

[NIGHTBOY]

If only we all had a spare £750 to throw at mounts eh?! Sadly I don't :/

[happy-kat]

How many minutes can be captured before rotation is visbible in an image, assuming low magnification and not using an avi. Perhaps it is a sliding scale as you move towards the zenith.

[RobH]

How many minutes can be captured before rotation is visbible in an image, assuming low magnification and not using an avi. Perhaps it is a sliding scale as you move towards the zenith.

As you guessed, it depends on where in the sky the target is, but a shade over 30 seconds is the maximum. Magnification makes no difference.

I started in AP using a 10 inch alt/az LX200 at F10 ( no-one told me that it was supposed to be near impossible with that setup!!) and generally used 20-25 second subs with no real issues.

As has been said though, you can get by shooting AVI's of planets/the moon with a dob, but long DSO exposures are impossible.....that's why you need a good EQ mount if you want to do those sort of targets succesfully, and is why some people pay the price of a mid sized family car to get one, although you can do fine with an HEQ5/6.....they just get really expensive when you get up to high payloads.

[ollypenrice]

As you guessed, it depends on where in the sky the target is, but a shade over 30 seconds is the maximum. Magnification makes no difference.

I started in AP using a 10 inch alt/az LX200 at F10 ( no-one told me that it was supposed to be near impossible with that setup!!) and generally used 20-25 second subs with no real issues.

As has been said though, you can get by shooting AVI's of planets/the moon with a dob, but long DSO exposures are impossible.....that's why you need a good EQ mount if you want to do those sort of targets succesfully, and is why some people pay the price of a mid sized family car to get one, although you can do fine with an HEQ5/6.....they just get really expensive when you get up to high payloads.

I agree with this with one exception; there are amateur astrophotographers whose mounts would buy a large family car!   (Not kidding, by the way. A Citroen C4 Picasso, for example, costs several thousand pounds less than an ASA DDM direct drive. And by all accounts it works a good bit better into the bargain.  )

Olly

[barkis]

If only we all had a spare £750 to throw at mounts eh?! Sadly I don't :/

Why not build yourself simple Barn Door tracking device, as already suggested.

Images of Milky Way star fields are very rewarding, and easily obtained with a DSLR camera equipped with suitable lens.

You could drive it by Stepper Motor, or if you make it accurately enough, you can operate it manually by simply turning the threaded drive screw at a rate determined by timepiece. It requires care, but quite doable.

There is plenty of literature around to help you. Do an Internet search on the subject.

It will give you an inkling as to the concentration hand guiding requires, even at fast f/ ratios.

Ron?