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Goto in a Dob...what's the fuss?!

emadmoussa

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emadmoussa

emadmoussa

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For a moment there I was thinking perhaps a Dob with Synscan capabilities will be nice. I'm not fussy about the Goto system, I do like manual searching and squinting my eyes trying to make sense of the star map. But tracking is a nice feature especially if you're looking at planets.

What's a con for one model is a pro for another and visa versa. A tracking mount will mean motors, and motors will mean a lot of things such as extra base weight, faffing around with wiring, power source and the most boring of all..aligning. On the other hand, manual is simple, you plonk it down and you're good to go. However, planets and the moon will - more than any other celestial objects - show how handy auto tracking could be. As you know I'm not a keen planetary observer, but I'm not a keen justify-er to fiends and family of why Jupiter went out of the field of view either :D

The other thing, while I heard good reports about Goto Flextubes being smooth enough in the manual mode (at least bit the early models), I still find it hard to believe that it wont' suffer from some degree of stiction. I never used a Goto Dobsonian before, but having used 3 other motorized mounts makes me draw this conclusion. I stand corrected - maybe it's a different story in recent models.

An equatorial platform is a middle ground, but it'll always make a tall dob taller (It's the difference between not using a step stool and using one)...and it will also need aligning. Will be nice if Skywatcher develops a tracking only rocker box and invested a bit more time trying to decrease the base weight and size majorly for big dobs...12" +. Or at least you'll have the option to pick...basic Autotracking model, or Synscan Goto. I think 2-3 years ago Autotracking was an option?

I'm just saying :)

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mitchelln

mitchelln

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Yes, SkyWatcher stopped selling the tracking only model around 2 years ago. It was right around the time I was looking at scopes and the last ones were disappearing from stock.

They were considerably cheaper than the GOTOs. Perhaps they didn't sell many or just wanted to consolidate their product line. The tracking variants mount was very different to the GOTOs.

They even were offering a GOTO upgrade kit at one time, but I heard it caused a lot of returns as you had to muck about changing the tube mounting. Reaching 600mm+ down a tube with a spanner is just asking for trouble. Even if you remove the mirror first you are still setting yourself up for fatal damage.

I guess your best bet is the 2nd hand market.

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emadmoussa

emadmoussa

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As a matter of fact, Modern Astronomy still stocks 12" Autotracker Dobsonian. This is at least what they say on the site. It's definitely the old model. I understand the recent models have been improved to allow smoother manual operation. How do you find your 300P Goto in the manual mode?

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swamp thing

swamp thing

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Now I know it's not for me to dare question your impeccable logic Emad, but why are you worried about stiction on a Goto model. You said yourself you wanted the tracking of Goto only, so you wouldn't be guiding manually anyway, just merely finding stuff manually for your own enjoyment. Here it makes little difference how "smoothly" it moves. ;)

Confused

near Croydon

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emadmoussa

emadmoussa

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That's right, Steve.. But generally I'm not worried about stiction per se, but rather how sticky it is. A bit of stiction should be fine as long as the mount doesn't creek or get stock in minute steering. I don't know to be honest, I never used a motorized Dob.

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AndyWB

AndyWB

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It seems a bit of an odd thing to do - to make a Dob GOTO. To be honest, I'd go with an EQ platform, but then my 10" on platform wouldn't be that tall still. And it'd still be low tech.

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emadmoussa

emadmoussa

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It seems a bit of an odd thing to do - to make a Dob GOTO. To be honest, I'd go with an EQ platform, but then my 10" on platform wouldn't be that tall still. And it'd still be low tech.

Few centimeters higher and I won't be able to reach the eyepiece at zenith without a step stool. And in the dark, climbing on stuff is the last thing I want to do...I know me...there will be a disaster :D

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mitchelln

mitchelln

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My 12" Goto is definitely not as smooth as the manual. You have to overcome the clutch friction. There is no way you could easily "nudge" it to keep it on target as you do with a manual. You also get quite a bit of recoil as the clutch tension resists the movement and shifts back. What Emad is calling "stiction" I guess.

I suppose the argument is why would you want to manually nudge a scope with tracking? If I have to fish around a bit for the target or re-center then I use the handset keys.

Perfect solution would be the ability to back off the clutches. Don't the Orion auto dobos have release handles on their clutches? Seems an obvious thing to me SkyWatcher have missed.

I have just got the full on cheat mode working as an option. Sky Safari on my phone with a bluetooth to serial dongle. The advantage is I can get comets on target quickly. Plus it just gives me some child like delight to have the scope seemingly slew itself by magic :)

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emadmoussa

emadmoussa

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My 12" Goto is definitely not as smooth as the manual. You have to overcome the clutch friction. There is no way you could easily "nudge" it to keep it on target as you do with a manual. You also get quite a bit of recoil as the clutch tension resists the movement and shifts back. What Emad is calling "stiction" I guess.

I suppose the argument is why would you want to manually nudge a scope with tracking? If I have to fish around a bit for the target or re-center then I use the handset keys.

Perfect solution would be the ability to back off the clutches. Don't the Orion auto dobos have release handles on their clutches? Seems an obvious thing to me SkyWatcher have missed.

I have just got the full on cheat mode working as an option. Sky Safari on my phone with a bluetooth to serial dongle. The advantage is I can get comets on target quickly. Plus it just gives me some child like delight to have the scope seemingly slew itself by magic :)

Errm. Actually, it seems that latest Skywatcher 350P models have the same clutches as the Orion USA. Is it safe to assume that they'll be smoother in manual mode. Reading about the Orion XX14g telescopes, they seem quite smooth in manual mode. If the latest Skywatcher 350P uses the same style then perhaps they're as good. I put together comparison picture to explain my point. Notice the different mechanism rocker box.

The Skywatcher 350P (latest model) photo is the courtesy of Gaidis, AKA, dude with tube. 

post-27451-0-55857600-1401968296_thumb.j

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Moonshane

Moonshane

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unless you do detailed sketches of solar system objects or very small planetary nebulae there really is no need for tracking on a dob. it takes a good while for a planet to cross the field of view even with a plossl field. e.g. at 200x it would take an object about a minute to cross the field of a plossl. it's not like you are having to constantly nudge the scope especially if you adopt the drift and nudge approach rather than constantly keeping it in the centre of the field.

I have an equatorial platform for my 6" f11 dob but that's not because of tracking it's because of the long tube having a rather long settle down time each time it's moved. this is not the case with a typical 8"+ dob.

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emadmoussa

emadmoussa

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How did you find things with the 300p? If things drifted by too quickly then get the goto, if not then I wouldn't bother

On planets I used Delos 6mm, and far as drifting was concerned...planets did drift by relatively fast. If you're pointing the telescope below 60-deg, the balance becomes critical and subsequently subtle manual tracking less smooth.

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mitchelln

mitchelln

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Errm. Actually, it seems that latest Skywatcher 350P models have the same clutches as the Orion USA. Is it safe to assume that they'll be smoother in manual mode. Reading about the Orion XX14g telescopes, they seem quite smooth in manual mode. If the latest Skywatcher 350P uses the same style then perhaps they're as good. I put together comparison picture to explain my point. Notice the different mechanism rocker box.

The Skywatcher 350P (latest model) photo is the courtesy of Gaidis, AKA, dude with tube. 

Well will you look at that :) Looks like a new design of motor box. So I doubt it will be a retro fit option unfortunately :( Good news for new owners. They had better make sure they ask though. Thanks for posting the info.

SkyWatchers site still shows old photos. That's a major enhancement you'd think they would promote. Instead the newest items on their News page are from 2011. Their website really is awful.

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emadmoussa

emadmoussa

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Checking around, I think

Well will you look at that :) Looks like a new design of motor box. So I doubt it will be a retro fit option unfortunately :( Good news for new owners though. Thanks for posting the info.

SkyWatchers site still shows old photos. That's a major enhancement you'd think they would promote. Instead the newest items on their News page are from 2011. Their website really is awful.

Checking around, I think it's only the 14" and 16" models are improved models. Can't be sure about the 300P though..

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