New product - 1 arc-second tracking ability without using conventional auto-guider

[Dennis]

This looks like a very interesting add-on product; Telescope Drive Master (http://www.mda-telescoop.com/index.php?option=com_content&task=view&id=18&Itemid=40), offering 1 arc-second tracking ability without using conventional auto-guider or PEC software!!!

Some parts of the website are still under construction and the outfit appears to be based in Hungary although I understand they have some commercial arrangement with Meade in Europe?

The Telescope Drive Master Encoder/Black Box product appears to be available for the following mounts (http://www.mda-telescoop.com/index.php?option=com_content&task=view&id=42&Itemid=67)at the time of this post:

Synta EQ-6 non-goto or goto / Skywatcher EQ-6 Synscan / Orion Atlas EQ-G (both old and new versions)
Synta HEQ5 /Skywatcher HEQ5 / Orion Sirius EQ-G
Celestron CGE
Fornax 50 / 51 / 100 / 150
Astro-Physics 1200
Losmandy G11 (both old and new versions)
Meade LXD 75
Vixen GPDX

Visit the website (http://www.mda-telescoop.com/index.php?option=com_frontpage&Itemid=1)for more specific details on the Synta products listed above.

Cheers

Dennis

[acropolite]

Looks like an exciting new development Dennis, hopefully the pricing will be affordable.

[bojan]

I do not think it will be affordable.
This is the closed loop system with high resolution encoder directly on RA shaft, nothing new in principle, but never cheap (because of the price of such encoders).
Classic guiding (with additional telescope and camera) is still a good enough and cost effective solution for amateurs.

[Peter Ward]

I read the manufacturers website with some interest.

I remain very skeptical however.

A super accurate RA shaft rate simply does not make a perfectly guided image.

I have seen stars randomly drift in RA *and* Dec for various reasons, and while RA rate errors are one cause, there are many others, well like: refraction, convective cells, mirror flop, differential flexure, wind buffeting
and thermal expansion/contraction of the telescope and telescope mount components, plus sag in the camera mountings etc.

In short, if you think one of these new wunderkind devices will deliver perfectly round deep sky stars at 2500+ mm... with no guiding...I think you'd also be in for a big disappointment.

[Wavytone]

This isn't a helpful solution. The website also shows the author has a very naiive understanding of the causes of tracking errors.

- it assumes a stellar rate only, it makes no provision for lunar or solar rates; most good drive correctors from 30 years ago could do that;

- it doesn't have any ability to track in declination, ie it is not able to cope with a mount that is not perfectly aligned with the pole. The effects of refraction mean it is impossible to eliminate the need for declination tracking at all parts of the sky. This alone makes it useless as to solve this you will have to use another drive corrector for declination;

- it has no capability for fine adjustments even in RA. Which also makes it useless.

- it makes no corrections for geometric errors in the mount (angles that are not perfect right-angles);

- it makes no corrections for atmospheric refraction;

- it makes no corection for the flexure of the mount and telescope assembly - which may change during an exporure if these are cooling or warming;

- there is no adequate explanation as to how it compensates for periodic errors in the geartrain.

It might be adequate for driving an equatorial platform for a Dob being used visually, or perhaps a small mount with a piggyback camera with a short lens taking short exposures of a few minutes, but thats about all.

A closed-loop feedback system (autoguider) solves all of the above.

[allan gould]

Interesting but the caveats of Peter and Wavytone are well made. A good autoguider and software will probably be cheaper in the long run

[Dennis]

Did you see the following example on the website (http://www.mda-telescoop.com/index.php?option=com_content&task=view&id=18&Itemid=40)?

E.g. the attached photograph below (NGC1161) was captured by a 10 minutes' (!) long exposure using a 16" LX200R OTA (and SBIG ST-8) with 2.5m (!) reduced focal length on around 70 degrees horizon altitude without conventional autoguider and, as you can see, the shape of the stars are free of any kind of visible elongation or distortion.

Cheers

Dennis

[Wavytone]

That claim is simply not credible as anyone with some astrophotography experience (i mean manually guided film shots) should know.

[Dennis]

The claim was made by the author on the website and an image was provided as evidence to substantiate the claim. Maybe it was a fluke or maybe only someone with advanced skills or a certain set up can do this? However, I have no reason at this stage to question the authenticity of the claim or the image.

Cheers

Dennis

[Peter Ward]

Yes, of course.

Bisque also have a similar shot on their PME website, but either shot proves very little...other than on a good night you can jag round stars at long FL's. In reality it simply doesn't always work that way.

Autoguiders are a very inexpensive, effective and proven solution
for the reasons already mentioned.

[Peter Ward]

I think it's also worth mentioning here there is much more to a mount's suitability for astro-imaging than an super accurate RA rate.

High machining accuracy, mechanical stiffness and high natural frequency of vibration are...pardon the pun..paramount. Having a super accurate drive on a bowl of jelly is simply a recipe for astro-imaging misery.

[Dennis]

From the authors website:

"If the angular velocity of the RA shaft deviates from the prescribed (sidereal or King Rate) velocity value, it accelerates or delays telescope's driving clock. In this way, a high precision, feedback regulated, real-time rotational speed control has been created. Corrective action happens via autoguider input port of telescope's driver unit if its own."

I thought that the King Rate was the drive rate taking into account atmospheric refraction? However, the author does go on to write:

“if you are hunting just about 25-30 degrees above the horizon (and far from the local meridian) with a 1000-1200mm APO refractor, you will be able to apply around 1 minute exposure time only due to the exponentially increasing refraction rate at low altitudes”.

Maybe he's referring to those higher altitudes at which advanced imagers normally image at?:shrug:

Cheers

Dennis

[Dennis]

Which is probably why the author, in the documentation on the website writes?

"It is not rational (and no cost-effective at all) to purchase TDM for low priced and weak quality beginner mounts. At the same time, if you have a sturdy and rigid hi-quality or semi-pro mount, the price of TDM is just on a gadget-price level. (The weakest mount which can be rational to use with TDM is the Synta/SkyWatcher EQ6 or Orion Atlas EQ-G. This is why there is no TDM adopter offered for cheap mounts.)"

Cheers

Dennis

[Zuts]

Maybe, my autoguiding setup runs to nearly 1000 AUD. It still has differential flexure and adds over 2kg plus cables to the imaging rig.

Orion autoguider AUD 469
102 mm achro AUD 250
side by side losmandy mounting AUD 300

Also I have to set it up, it requires a laptop connection etc. If this item was around AUD 1000 I may be tempted to sell my autoguiding gear.

I have a self guided camera but need the autoguiding for Ha shots; and believe me its a joy to use the self guiding on the SBIG without the hassle of connecting all the autoguiding stuff; and this to me seems an equally simple solution for non SBIG cameras or narrowband shots; depending on price and suitability.

Cheers
Paul

[Dennis]

From what the author has written, I would expect the system to be more capable that this, given the limitations he has addressed below:

"Unlike different conventional autoguider systems, Telescope Drive Master does not need and does not have any feedback from the sky during tracking. This means you need to minimize the mechanical and adjustment problems of your telescope OTA, mount and pier such as mirror flip, tube & mount flexure, dirty and improperly installed RA bearings, swinging cables of CCD & power supplies on OTA, instable and moving pier as the most common problem sources and, finally but chiefly, inaccurate polar alignment.

If you want to achieve less than 1" (arc-second) tracking error during your 5 (maybe 10) minute exposure on "photometric altitudes" of the sky (zenith distance is less than 40-45°) without position-corrections, you need to keep the axis of the RA shaft on the (refracted) pole (see explanation below) with the best accuracy you can achieve."

Cheers

Dennis

[Peter Ward]

The flaw in this system is it simply isn't looking at deviations at the imaging sensor level.

Perhaps they use a direct coupled encoder, or they couple the system via intermediate gears, either way there are still eccentricity, indexing and periodic errors.

The only way these can be accounted for is to accurately measure deviations against the sky, not the RA shaft.

[Dennis]

Again, as the author openly acknowledges:

:There is no optical feedback from the certain part of the sky observed so your telescope needs to have a sturdy and rigid mount which is not cheap. (This system is insensitive regarding flexure of mechanical parts and weak quality RA bearings.)"

Cheers

Dennis

[Dennis]

Gee Peter, lighten up and give the guy a break!

All alone, sitting quietly at my desk, here is Uncle Dennis’ train of thought:

I found a new astronomy gadget – I think, “Gee, this looks like an interesting product, I’ll post a link on Ice In Space to see if anyone is using one and to see what others may think of the approach”. What happens next?

I read some replies that say it cannot do certain things yet when I look at the website, there is evidence that is appears to work as described.
I also read some replies that appear to “find fault” with the system and, maybe its how I interpreted the post, appear to “rubbish” the system. But upon further reading of the website, the author himself acknowledges those limitations.

Maybe it’s just me, but it seems the product appears to have been too strongly denounced, in quite forceful terms, prior to having seen any tests or results?

Cheers

Dennis

[Zuts]

Other people including Qui of QHY are looking at similar solutions so they must think these 'absolute' methods have some credence. In any case I wouldnt want to buy the first unit but if after reading some independant reviews it was found to perform as advertised then i would probably buy one, and at the risk of naming names I bet Houghy would!.

[Peter Ward]

Hey, I have no axe to grind here.

Any product that effectively improves the tracking of a mount is a good thing. :)

What I do find annoying is: on the referred website, the implication is this device removes the need for guiding only by RA shaft rate correction.

I've found just he opposite to be true.

The better you can guide on the sky, the more flux you can lay over fewer pixels, and the better the result.

[Peter Ward]

Hey, I have no axe to grind here.

Any product that effectively improves the tracking of a mount is a good thing. :)

What I do find annoying is: on the referred website, the implication is this device removes the need for guiding.

I've found just he opposite to be true.

The better you can guide, the more flux you can lay over fewer pixels, and the better the result.

[Dennis]

For those interested in seeing the results when this system was fitted to a Vixen GPDX mount, and if you can access the Cloudy Nights Forum (http://www.cloudynights.com/), here is a link to one user’s experience (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2856182/page/0/view/collapsed/sb/5/o/all/fpart/1#Post2859133).

The results look very promising although the user indicated a price of around 1,000 Euros, so you won’t get much change out of $2000 Au. :(

Cheers

Dennis

[bojan]

That was exactly my point.
Too expensive... guiding does the same job ( PLUS it allows for not-so-accurate alignment) for much less money.

[Bassnut]

Somethings wrong here, the site shows the encoder fitted directly to RA as an output encoder. To resolve 1 arcsecs, it then needs to have at least 1.2million ticks per rev. Ive seen Heidehain encoders a lot over the years on CNC machines, they are top shelf, and, very expensive. I scaned Heidenhains site for prices and anything like the model they used, to no avail unfortunately (the picture res of the encoder frustratingly doesnt allow reading of the model number), but at a guess an encoder alone of that res would be many times more than 1k euro. So, Im thinking they have gear reduction on a lower res encoder, which then raises questions of machining accuracy/variability between examples and PE within its own gearing.

[AlexN]

I must admit, the most interesting thing on the site to me was a 20min unguided exposure using a 160mm F/8 refractor on an EQ6... A 160mm F/8 refractor would have one hell of a moment arm, be fairly heavy, especially in the front end, I know I've managed 5 minute unguided shots through my 102 F/7 refractor, after nearly a full night tweaking the polar alignment.. 5 minutes at 700mm is pretty good in my books.. 20 minutes would just be out of the question without guiding, or perhaps, this new device..

Thanks for bringing it to our attention Dennis... Its great for the people with paramounts to say its rubbish, but for those of us not made of money, this might be an option... I will however be waiting for some real world results...

Post the link on Cloudy nights and let the americans try it first! :D

Cheers.
Alex.

[leon]

Interesting stuff, but I might just stay with the set up I already use, it's not perfect but it dose the job pretty well.

Leon

[AlexN]

Ooooh... here we go...

Checked on Cloudy Nights.. Someone already has one... Heres a link to his results with his GPD/GPDX mount... Looks like it worked as described...

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2856182/page/0/view/collapsed/sb/5/o/all/fpart/1

[AlexN]

Oh, forgot to mention... He paid 1000 Euros for it, however the creator has now signed a deal with Meade...

3 things could come of that...
-Bigger company, manufacture in bulk, cheaper product for all end users.
-Bigger company, manufacture in bulk, sell unit only for Meade mounts/intergrate into meade mounts...
-Bigger company, Manufacture in bulk on the cheap, sell to everyone at inflated prices and because they are the only company selling it, we cant do anything about it..

[bojan]

It will never be cheap.
Encoders with that sort of resolution are on the market for a long time.. and price never dropped.
The only thing that can drop is quality.
Stick to auto-guiders guys, that what they were designed for.

[Dennis]

I’ve just dug up some receipts and invoices for my side-by-side auto guiding set up for a quick cost comparison.

Orion Deep Space Star Shooter:….. $569
WO 66mm F6.1 Petzval:…..$349
WO Diagonal for short tube OTA:…..$100
WO Guide Rings:…..$100
Scopestuff side-by-side plate:…..$100
WO Saddle/Plate combo:…..$200

The above comes to around $1400 and was purchased over a period where the Aussie/US $ exchange rate fluctuated, so the figures can only be a rough guide. The Orion camera is the original Peltier cooled model as I wanted it for noise-free, long guide star exposures and for this, it works really well. I’m sure that someone could cobble together a less expensive kit, but the above is just what I’ve ended up with over the years.

So, technical/performance issues and flexibility/versatility issues aside, this makes roughly $600 difference between my rough costs above and the guesstimate of $2000 for the TDM kit.

However, if I were building a new system from scratch, I would probably double the budget and would likely lean heavily towards an SBIG dual chip camera, as I have enjoyed much more reliable results with my SBIG ST7E dual chip ccd camera compared to my side-by-side set up; the overall set up, complexity and operation is simpler too, a single camera on a single scope looking at one section of the sky.

Just some thoughts; not trying to convince anyone to take my position which is simply where I am through historical factors, opportunities and trial and error, which will no doubt change as I get wiser and hopefully, wealthier!:lol:

Cheers

Dennis

[Peter Ward]

Arrgh..... so are there really people out there that will pay
"1000EUR + shipping + VAT" .....so at about $A2200? for a device that
*will not* correct for:

polar alignment error
intrinsic sidereal/king rate error
mirror flop
mount flexure
OTA felxure
atmospheric refraction
atmospheric convection
camera sag
mount /OTA thermal expansion
mount/OTA thermal contraction
mount non-orthogonality
intrinsic gear indexing errors
etc. etc.

But...by crikey...the constancy of RA shaft rate is brilliant!

Humm.... I seem to recall a dual chip, self guiding CCD camera was introduced to the market nearly 20 years ago, that solved all of these problems....nah...I must have been deluded :)

[AlexN]

Peter - Agreed... At 2200 AUD I'd be looking for an ST7XME / ST8XME, not an RA drive corrector...

[Dennis]

Within the stated limitations of TDM as documented on their website, it would appear that the system is targeting the amateur astronomy community who may want to manage one or more of the following scenarios:

It does not need to find bright guide star for tracking (the observation process can be automated on much easier way).
High density filters (e.g. H-alpha) do not have any influence to the performance of tracking.
TDM is a standalone application so it does not need any PC support or other external device for using it.
TDM is firstly recommended for the observers who intend to take a lot number of shots per night about different parts of the night sky quickly and easily. (E.g. supernova patrols, comet and/or asteroid hunters, observers of cataclysmic variable stars, etc.)
TDM can be an extremely advantageous application for robotic telescope owners who needed to find bright enough guide stars within the field of view manually so far.
For "tourist amateurs" who do not want to drag an extra tube and CCD just for autoguiding purposes up to the peak of the mount escaping from light-polluted regions.
If you want to use a narrow band filter (e.g. H-alpha) but you have a dual chip CCD or just an AO-7/AO-8 adaptive optics as guiding equipment, your guiding chip will be in almost total darkness... But TDM will help.
If you have just a tiny guiding chip at the bottom of a small aperture tube, you probably will not always be able to find an appropriate guide star... TDM will help you again.
TDM together with AO-7/AO-8 adaptive optics is the best equipment that you can have!!! TDM will eliminate the periodic error of your mount (independently of the magnitude of its amplitude) and AO-X will eliminate the rest of the deviations like scintillation and/or refraction. This is the ideal, ultimate set of serious astrophotographers!
Who is not satisfied with his/her mid-ranged telescope mount's tracking ability but does not want to spend another couple of thousands of euros/dollars for a top rated one (which has much more PE then TDM...), those will appreciate this cheaper solution.


Cheers

Dennis

[bojan]

If someone is really annoyed by the presence of PE, in my opinion the much more cost-effective way to minimize it is illustrated here:
http://groups.yahoo.com/group/EQ6/photos/album/1421078408/pic/list
To polish the worm, there is no real need for lathe, it can be done with simpler, ad-hoc arrangement.
Also, the replacement of original gearbox (or total elimination of gears between motors and worm gear by using timing belts) does help a lot, some reports are talking about 5"pp and even better (for EQ6).

However, as Peter said, all this *will not* correct for items on his list.
So, all this effort does not make much sense .. when at the end, some sort of guiding is still needed for longer focal lengths imaging.

This discussion reminds me of a similar thread, about direct drive stepper motors on both shafts.. like ideal solution for ideal mount. Yes, we can and we should aim for the better.. but we have to take into account the cost of this, sometimes irrational urge... IMHO of course.

[multiweb]

I read this thread and the cloudy night forum with great interest. It's quite a revolutionary approach to guiding. I have to join the skeptics though :whistle:
We look at the sky and we guide accordingly in reference to what we're imaging right? Putting aside what Peter already pointed out that we have orthogonality problems, wind, flop, flexure, etc... you name it: still if we had resolved all of the above it would still be like being bolted solid to a boat deck and taking pictures of the sky right? I mean, you can't compensate only one RA rate when there are so many other variables at work? :shrug: Sounds just like common sense to me to use the stars as a reference?

[Dennis]

Yes – at least one person on CN!:)
It appears that the owner of the GPDX in question seems quite pleased with:
“The PE on my mount is typically +/- 15-20arcsec, the TDM can reduce this down to +/-1 arcsec without any significant setup effort”.


Hmm, does my radar require re-calibrating, or is it picking up the sparks from the grinding of an axe?:)

Cheers

Dennis

[Peter Ward]

PT Barnum, of Barnum and Baileys circus had a great saying:

"We've got a little something for everyone"

........ (like Fornax 50, 51, 100, 150, Synta EQ6, SkyWatcher EQ6, Orion Atlas G, Celestron CGE, Astro-Physics 1200, Losmandy G11 owners?? )

Now looking at the "happy" CN reviewer's linked data for this device


http://www.cloudynights.com/ubbthreads/attachments/2856182-Drift%20090109.jpg


we see, despite some impeccable RA tracking, there is close to half an arc minute of Dec drift in 1200 sec (!!)


Barnum had another great saying: "There's a sucker born every minute"
:lol:

[Dennis]

:lol: Peter, thanks for confirming that my radar does not require calibration.:)

Cheers

Dennis

[Wavytone]

Another very dubious claim. Very few telescope owners have the foggiest idea what order of magnitude their PE is, and even fewer have the ability to measure it accurately.

Many here need to be reminded that the US does not have any laws about misleading advertising and manufacturers can and will say anything.

As for the CN "review" that could have been posted by the designer of the device, for all we know.

[AndrewJ]

With my Mech Engineer hat on,
if the encoder used is of good enough accuracy, and the motor feedback loop quick enough, this claim is probably valid,
but getting a perfect RA Axle "tracking rate" doesnt help synchronise the "entire mount" to the sky, which is where all the argument comes in.
An absolute encoder on the RA shaft will certainly "proactively" remove the bulk of PE and backlash from the drivetrain, but some form of guiding ( albeit now much smoother ) will still be required to give round stars
And its round stars that count.

Andrew

[Dennis]

You are of course right, all these are possible. But, from looking at the TDM website and the results from the CN poster, as well as reading the technical information posted by Fred and Bojan on encoder technology and costs, I am still feeling charitable to the TDM dudes and personally, have chosen to give them the benefit of the doubt, or at least a fair go.

I think that Hungary is in Europe though.:whistle:

I wonder if I re-visited the old forums of good old fashioned film astrophotography, would I be able to see the baby being thrown out with the bath water when the first Cookbook CCD camera appeared on the scene! Now I am just being naughty!;)

Cheers

Dennis

[Omaroo]

uh? Absolutely not! Where did you get that gem from? LOL! THe USA is incredibly tough on false and misleading advertising - because manufacturers have an avenue to sue each other over it via the Lanham Act.

Living in the USA for a number of years, and being involved in developing new software and workflows for the publishing industry, I constantly came across people warning our new Australian company to be very careful about making claims that could even be slightly construed as being false.

Wests Law Encyclopedia:

[bojan]

Yeah right.. if they manage to get their hands on them :-)

[Omaroo]

Manufacturers always seem to have armies of lawyers at the ready Bojan... and I reckon that they'd be keeping pretty close checks on one another.

[bojan]

That is probably true for the big companies (like NEC I work for.. it is definitely one of them).
However, for the small guys, I doubt it. Lawyers are very expensive...

[Omaroo]

OK - we're coming down to semantics.

Sorry to divert the thread Dennis.

[Dennis]

No worries Chris – I suspected that the US must have some quite strong consumer protection laws, given the work of people like Ralph Nader, so it was quite reassuring to hear of your experiences.:thumbsup:

Cheers

Dennis

[Omaroo]

I suppose that a fraudelent advertising claim must be proven beyond doubt before action can even be considered. While a great deal of protection exists, it's up to the courts to find whether a case is justifed, and this is always the point of contention.

If the manufacturer of this device was to claim that it enabled a user to experience perfect siderial motion at the sensor under all circumstances then maybe that could be challenged. I don't think that they are trying that though.

[bojan]

It seems they do not. However, less careful (or un-experienced) reader may jump to a conclusions, as it already happened (IMHO).

But even if they do claim impossible things, what anybody can really do? Remember, this particular manufacturer is located in Hungary or who knows where.... way out of the hands of US laws

[Geoff45]

Yes
I believe that they have stopped putting tasting notes on their wines in case somebody complains that they couldn't pick up the "hint of peaches"

[Dennis]

It seems that Meade Europe are now the exclusive, world wide dealer and one would assume that they have gone through the machinations of a business case proposal and due diligence before purchasing distribution rights?

And yes, I do read that Meade USA are in dire financial straits and others have questioned their business model and competence, but maybe, just maybe, the TDM product could be a ridgy didge fair dinkum product and it might just deliver what it claims:

Quote:
“Telescope Drive Master (TDM in short form) has been developed for compensation of periodic and non-periodic tracking errors of mass produced equatorial telescope mounts which errors occurred on account of mechanical manufacturing and assembling inaccuracies”.

Cheers

Dennis

[Zuts]

Looking at Peter Wards list, nearly everything he mentions has nothing to do with the mount but to do with other things, i.e polar alignment, differential flexure, refraction and so on. So I reckon if you can add something to a 1600 AUD mount that gives you better PE than a Losmandy or even a far more expensive mount at a far lower price point then go for it. Having souped up the mount in this way there is nothing to stop you using a guide scope a well.

Cheers
Paul

[Bassnut]

You make a couple of very good points there Dennis. Meade must have done some serious research, and when you think about it, the one single thing that stops the higher end all-in-one Meades from becoming a default imaging platform is PE, its their achilies heal.

And before I get trashed for that, Ive done pretty well with my Meade tube, and If the TDM really does what it says, I would be happy with their mounts too. Again, if the TDM works, it would be the perfect match for Meade mounts.

[bojan]

You will have to use it anyway... So why bother?

[Zuts]

This is very hard to say. Still when people talk about the 'supposed' problems with the EQ6 it is mainly about the PE, certainly with the addition of a few aftermarket knobs, pillars and other bits and pieces it is a great mount IMHO. My EQ6 is certainly stable enough for decent astrophotography so what else makes a 6,000 AUD losmandy a better mount. And before everyone jumps in and flames me IMHO if you get round stars on a 30 minute exposure it's a good mount; and a PE of 1 arcsecond would go a long way to acheiving this.

An EQ6 with 1 arcsecond PE would be a very tasty mount indeed, and if it only added 1000 AUD to the price then i would be very tempted and the fitting of said device would probably be very straightforward and easy to accomplish.

Cheers
Paul

[Peter Ward]

Ok. I'll bite. Current G-11's running at around +/- 3-4 arc sec -uncorrected.

They are fully machined, made of brush finished anodized T6 & ground stainless, and have high precision shaft bearings and phosphor bronze worms plus a tripod built like the proverbial brick dunny. Then there is the Gemini system.....and T-Point like modeling in a box.

BTW a Benz also costs more than a Hyundai. Sucks doesn't it? :)

I digress.

This old chestnut has surfaced before...but I figure I'll say it again: with a common garden rock I can get round stars with a 2 minute exposure and 8mm fisheye.

But, at a FL of 2900mm, and one heck of nice mount, I've found some serious guiding is mandatory.

I suppose the point I am making is: even if there was such a thing as a "perfect" mount, unless you are imaging in a vacuum, the earth's atmosphere will happily make your deep sky stars look egg shaped.

IMHO if you want to get tighter stars, feeding back what the tracking and atmosphere is doing to the image is *way more* important than fussing over a super accurate RA rate.

[bojan]

Exactly my opinion also.
And $1600 remains to be used for something far more useful, however not necessarily fancy.. Toyota has exactly the same number of wheels (4), just like Ferrari...
A-->B.. same trip and result, but much cheaper vehicle.

[Zuts]

Yes, ferrari holden and so on. The point is new technology surfaces from time to time which may level the playing field. The current commodore with airbags, abs brakes, traction control and so on is a mighty fine car. For 30,000 AUD it is definately a much better and safer car than most mercs more than 10 years old which 10 years ago may have set you back over 100,000 AUD.

Maybe we are on a cusp, who knows, but I know this; aint good new tech at an affordable price a mighty fine thing :)

Cheers
Paul

[Zuts]

And to Peter, yes some serious guiding is mandatory. However if i can start to guide with a PE of only 1 arc second i think i am better off than with the usual 30 to 50 arcseconds of the average EQ6.

And to Dennis, i agree with you, if the price is right and IF it works as advertised it is probably a good thing.

:)

[AlexN]

Yeah I'd love to agree with Paul about the EQ6 only being less than the G-11 in terms of PE... but Man... I sure wish my EQ6 would grow up to be a G11..

Dont get me wrong, for the money the EQ6 is great, and with a couple of refractors on it it chugs along nicely for imaging.. However once loaded up with the C11 and trying to image at 2800mm F/L I really do wish I had something a bit more sturdy underneath it.. I've already spent nearly $700 just adding stability to the EQ6 (ADM D-plate saddle and D-Plates for my scopes) , with another $1500 odd to be spent (new counter weight shaft + counterweights im having made + Losmandy HD tripod) but stability only goes so far... the internals are its let down compared to the G11 which is truely a work of art, and definitely cheap for what its is... G11 + Gemini is a stunning combination

im not taking anything away from the EQ6, I love mine, but once you start getting some weight on it, or using an extreme focal lenght, its shortcomings become rather apparent. (as do my own!!)

Yes, Reducing its PE would make a difference, and would make it perhaps better, however its still not going to do the job that a self guiding CCD would do, in conjunction with Adaptive Optics...

As Peter said, even seriously over mounted scopes (say, a 140mm F/8 APO on a Paramount ME) still require/benefit from guiding, and adaptive optics help to minimize the the negative affects of the atmosphere..

Perfecting RA tracking is not going to help you if the seeing is poor, its not going to help you if you're not as well polar aligned as is possible, its not going to help you if your mount is slightly imbalanced.... What will help you in these situations. Guiding..

As the website for the TDM states, it will work concurrently with SBIG guiding systems, but it does not mention other autoguiding setups... so its hard to say if it will or it wont.. but this is for sure. If it only works with SBIG guiders and you have a self guided SBIG, you'd be better off buying an AO unit than getting 1arcsec PE I think..

Correct me if I'm wrong..

[DGK]

Hello,

Thought it was about time I joined iceinspace. I'm an Australian and have lived in Salt Lake City, UT USA for just over 11 years now. I'm the "dodgy guy" that posted my early experience with the TDM. Its all ridgy didge, to my mind the TDM is a little rip snorter!

Cheers

David

[h0ughy]

Welcome to IIS David, can you throw some more light onto this discussion other than the one that was linked to you initailly;)

[DGK]

Sure, but I've not been able to test the unit outside since my IM809 became available. Winter weather here is rubbish (and very cold....).

A winter project for me at the moment involves putting together a circuit to generate 2000tic/rev TTL quadrature from the encoder to send to my Argo Navis. Some critical components arrive tommorrow after a bit of a lead time, these are significantly higher quality than those I could pick up at Radio Shack! I've also managed to find an ERN120 on ebay for $99 (and a spare for $20!) to fit on the DEC and am visiting a friend this weekend to get adapter components turned up. All with a view of having the TDM encoder serve double duty and the Argo Navis gets to see 20,000tic/rev on both axis.

The developer asked me not to reveal the TDM encoder model to anyone so please don't ask ;) What I will say is inspection of the TDM interior board component layout was enough for me to confirm in my mind roughly how things are being executed to achieve 0.125arcsec resolution. There's a few tricks that are very clever.

Cheers

David

[Kal]

Just to clarify the technology that is being offered, is this in principle the same technology that Astro-Physics has developed for its 3600GTO mount? (which gets PE down to less than 1/2 arc second for long exposures)

http://www.astro-physics.com/products/mounts/3600gto/precision-encoder-complete.pdf

[Dennis]

Hi David

Welcome to Ice In Space!:welcome:

Ah, so you are the guy on CN who has actually tried one of these units! Thanks for dropping by; it is good to hear about your positive experiences.:thumbsup:

Not too sure why some of the natives here took a rather uncharitable view of this product; nor why they would want to be so rude to a complete stranger who had been kind enough to present such a good report, with accompanying graphs, etc., but clearly you’ve seen through the BS, have a good sense of humour and a thick skin too boot!:lol:

Hope the weather clears up so we can hear more about your tweaks to the system.:)

Cheers

Dennis

[DGK]

Hi Andrew,

The AP concept is the same but the encoder design is naive (and no doubt very expensive), as is the signal processing. The TDM encoder is an off the shelf item and relatively inexpensive.

Naive is not a word that I should have used used when referring to AP, an excellant high end kit company - "overdesigned" would have been more appropriate. Their rationale for using a 9" disk is to make sure that over a full revolution there is no timing drift. However, by using an appropriate industrial grade encoder and signal processing, the TDM is capable of achieving pretty much the same performance. The TDM encoder housing diameter is 2 1/4". The AP 9" disk is probably wrapped in very expensive CNC'd aircraft grade alumin(i)um making it even bigger and more expensive.

Cheers

David

[bojan]

Autoguiding is still way cheaper, and I strongly believe much more accurate (because of all the reasons mentioned earlier in this thread).

[Kal]

The technologies don't have to be exclusive of each other bojan. There are also some applications where on long focal length imaging you will not find a guide star that is bright enough and where autoguiding is not a viable option.

Long term I can see autoguiding will still be the cheaper, adequate for 99% of people, and more common solution used, but I can also see the demand for this technology from some specialist applications.

[bojan]

Kal, in principle I can agree with you about your estimate of potential users numbers, perhaps it will be a bit lower, and that will depend (among other reasons) on quality of the final product and of course, price.
The problem with future production may be the high price, as there will be no volume where those guys can find the room to keep the margin low.
Other alternative will be to compromise the quality to stay in the market (using cheap of-the shelf products, as David mentioned in his post earlier)
We shall see...

My problem here is that this is not the new technology and there still exist the need for auto-guiding in most cases, so I see something like this not really necessary. You can always find a suitable guiding star.. this is part of the challenge and fun in this game, right? And, easiest way is to go to the shop, spend couple of k$ and have that warm feeling inside..
Also, there are other ways to improve PE, for those skilled with mechanical tinkering (for EQ6 specifically, the replacement of gearbox with belt drive or even using better quality worm gear improves the PE drastically, for much less money).

Personally, I intend to stick to amateur philosophy in my astronomy projects: that means, I am avoiding commercial products wherever there exists a slightest chance of making something myself or using freeware from other amateurs. Even if it is slightly more expensive (I am prepared to pay for the fun I have here, you see :-)) In the same spirit, that also means that I will always offer my amateur advice and know-how (when I come up with something good enough) free of any charge, as it should be widely practiced in amateur community.

[renormalised]

That's the slow acting poison that SWMBO just slipped into your cuppa, that only she has the antidote for...and that she slipped into your cuppa for just spending that $1000 on a guidescope and camera:eyepop::P:D

[bojan]

You may be right here :D
But man, we are living in real world. And, this morning, when I had a careful peek into the status of my super (what was left of it) believe you me it was a horrible experience.. much worse that PE of my mount.
I still prefer the challenge, though ;)

[renormalised]

Maybe your super needs one of those TDM's to keep it on track:P:D

[bojan]

Now THAT would have been useful.
Unfortunately, TDM systems for superfunds are still on the drawing boards.. if they ever become reality :sadeyes:

BTW, some DIY here would also be much better solution that relying on others... maybe.

[renormalised]

Problem with DIY is not everyone is competent enough to tackle those sort of projects. Some are more competent at one thing than another...for example, they can build obs' but can't solder a PCB...and some are just plain lazy. Why make it yourself when you can buy it already made:)

[bojan]

I agree with you.... So they need help in developing DIY skills.
Also, what bothers me is most prospective "businessmen" tend to offer only partly accurate information, usually only the part that is in their interest. The good example of this behavior is the situation with Darren's firmware mod for standard EQ6 (freeware, which I am using and it works very well. However, commercial counterpart is even offering the replacement of processor used in hand-pad, only to have red LED on instead of green. And the only thing that needs to be done here is to replace/rewire couple of resistors.
Similar thing is happening with forgetting to mention the (free) Mel Bartels software and its capabilities when promoting commercial products with subset of Scope.exe functionality).
That blurs the picture to people who do not know that they are potentially good with DIY approach, and it promotes laziness, by all means. It can not possibly be an amateur philosophy, IMHO.

[DGK]

Andrew et al,

I am in the 1% tail you posit because of the following:

1/ I want portability and quick setup/pulldown time.

2/ I am a "serious" visual observer, not a "serious" imager. A matter of personal preference. Thank goodness many others are different otherwise I wouldn't get to see their wonderful images. :thumbsup:

3/ I like to push/go-to my Stellacam3 to objects and then have the image come up straight away on the monitor without fussing about. The portable mount combo gives me bang on pointing and polar alignment good enough for 1-2min exposures, with the TDM in the background I should be able to approach 10min, which I think is pretty cool. :D

4/ I like to set my truss dob up at the same time as the SC3 on either the M809 or ED80 (usually the big one tho...) and have both pointing at the same object. Fun at star parties but a bit of a work load, autoguiding is just out of the question unless there's help....

When I finally decided that the MTS-3SDI PE correction was not going to work well enough for me I contemplated upgrading my mount to a G11 or even a Mach1. Fortunately sanity kicked in :screwy: and I went looking at what I could do to implement autoguiding. After much thought I decided the xtra weight was going to kill my GPD (the M809 is about the limit visually and is okay with the SC3, probably not for a STL-11000CM :)...) and the extra setup, operating and pulldown time was going to kill me. Then I came upon the TDM around fall and haven't looked back since. Fits my needs perfectly :thumbsup:.

Cheers

David

[DGK]

I just noticed that Meade Europe has the TDM up on their site now:

http://www.meade.de/news/news/archive/2009/february/article/pressemitteilung-2.html?tx_ttnews%5Bday%5D=03&tx_ttnews%5BbackPid%5D=393&cHash=4def1d0efb

No pricing, I'm not sure how this company is affilliated with Meade however. They may just be a dealer.

Cheers

David

[renormalised]

Meade Europe have been sold by the parent company in order to get Meade out of its troubles.

[Dennis]

Thanks David – I notice that they have added the Tak NJP to the list of mounts supported. And there is a Mk II on the original TDM website (http://www.mda-telescoop.com/index.php?option=com_content&task=view&id=52&Itemid=82).

Cheers

Dennis

[DGK]

Hi Dennis,

I'm struggling a bit to see what advantage there is in having TDM correcting with an autoguider. Maybe it makes a difference with high resolution imaging?

The first version I have is not supposed to work below a 1.25x guide rate but I have found it works fine down to 1.15x. Maybe v1.6 had this software fix included?

Poor weekend weather has prevented further tests and am still putting together the kit to generate position info off the TDM encoder.

Cheers

David

[gregbradley]

Hi David,

I see ASA is also making a mount with a similar approach.

There is also an advanced low friction coating that is quite cheap that is
claimed to reduce PE considerably on all mounts.

http://www.andysshotglass.com/astromo_mod_store.html

Perhaps a combination of both would setup the mount to be
able to have just a slow autoguiding like once a minute to correct
for flexure or slow polar alignment drift.

In my experience with a few mounts, exact polar alignment and
balance is one of the most important factors.

Self guiding is good but limited. Blue filters often stretch the
guide times out longer than ideal for the mount and the guide chip is tiny
and very low resolution which weakens the result. I get far better results
with an external guide scope.

I also find guide star selection can really make a big difference.
If I get higher than expected guide errors I pick another star. I often see
the right star giving 1/3rd the error of another star. Often the brighter stars
are a bit bloated and the centre of the star being computed by software may be
more prone to error than a tight small star. With self guiding your
choice of stars is very limited and none of them are what you would call
tight.This is why I like the ST402ME for the guide camera. It is similar to the
Starfish in FOV and is cooled and I can get quite good resolution for gudie stars
using a cheap AT66ED lightwieght scope that does not seem to flex (20mins seems fine
if not windy and polar alignment is OK) 30 mins is also fine. This is a Tak NJP mount and
its PE is around 2 arc seconds by itself.

If I read the site correctly it seems you can also use an AO device with this as well.

So wouldn't the best of both worlds be the gears coated with low friction coatings, the TDM,
the AO and then an autoguider set for 1 minute corrections to pick up flexures. Perhaps that would
be a super setup. SBIG are releasing their new standalone autoguider with an artificial star to correct
for flexure as well as normal corrections. That'd be a beauty.

Greg.

[Dennis]

Hi Greg

From the TDM website, some of the scenarios listed for utilising the capabilities of the TDM unit are just what you have described above in your thoughtful and interesting analysis, vis-à-vis:


TDM is firstly recommended for the observers who intend to take a lot number of shots per night about different parts of the night sky quickly and easily. (E.g. supernova patrols, comet and/or asteroid hunters, observers of cataclysmic variable stars, etc.)
For amateurs or professionals who have backyard or institutional observatory for permanent telescope installations (with permanent and good polar alignment).
TDM can be an extremely advantageous application for robotic telescope owners who needed to find bright enough guide stars within the field of view manually so far.
For "tourist amateurs" who do not want to drag an extra tube and CCD just for autoguiding purposes up to the peak of the mount escaping from light-polluted regions.
If you want to use a narrow band filter (e.g. H-alpha) but you have a dual chip CCD or just an AO-7/AO-8 adaptive optics as guiding equipment, your guiding chip will be in almost total darkness... But TDM will help.
If you have just a tiny guiding chip at the bottom of a small aperture tube, you probably will not always be able to find an appropriate guide star... TDM will help you again.
TDM together with AO-7/AO-8 adaptive optics is the best equipment that you can have!!! TDM will eliminate the periodic error of your mount (independently of the magnitude of its amplitude) and AO-X will eliminate the rest of the deviations like scintillation and/or refraction. This is the ideal, ultimate set of serious astrophotographers!
Who is not satisfied with his/her mid-ranged telescope mount's tracking ability but does not want to spend another couple of thousands of euros/dollars for a top rated one (which has much more PE then TDM...), those will appreciate this cheaper solution.

Cheers

Dennis

[DGK]

Thought I'd drop a line to let you know I managed to get the TDM encoder signals converted to TTL without messing up the TDM. It seems to work very well and gives me 20,000tic/rev for my Argo Navis as well as providing what the TDM needs. The encoder plugs into the converter and a new cable connects the converter to the TDM.

I put an ERN120 on the DEC axis to give me 20,000tic/rev on that axis and this plugs into the enclosure for the TDM encoder converter circuitry. A 9pin to RJ45 cable supplies the Argo Navis with the RA and DEC TTL quadrature signals. Both encoders are powered independently of the TDM and Argo Navis so I have the option of just using the Argo Navis when not imaging.

Now I need to wait for clear winter skies and then I can test out how good a quick 4 star polar alignment can be with these encoders and further test/use the TDM.

Cheers

David

[Dennis]

Nice work David, it looks like you’re really getting under the hood of the TDM to tailor it to your needs. If what you have done could be of use to others out there, with similar equipment and operational requirements, might it be worth while dropping the TDM designer an e-mail?

If your modification is easy to incorporate as a custom model, you might end up with the “TDM-David” variant!

Cheers

Dennis

[Bassnut]

Ive been wondering about this design for a while now, putting aside the overall usefullness arguement, it appears the output encoder is used primarily as a speed feedback device (digital tacho) to achieve very low PE, rather than for absolute positional accurracy, which would require a much higher resolution encoder, as used in expensive pro rigs (hence my apprehension earlier on the cost of the encoder).

Great if thats the case and it appears to work, smart idea, but then it doesnt improve pointing accurracy, not that matters perhaps, dont know. I also wonder, since it doesnt rely on absolute position for calculating tracking accurracy, whether it might suffer long term drift?.

[AlexN]

Fred, I think it would still suffer long term drift... take for example if your polar alignment was less than optimal.... It also wouldn't correct for any dec drift (which there shouldn't be any if everything is aligned perfectly) however I know no matter how much time i spend polar aligning, my guider is still making dec adjustments...

[DGK]

Hi Dennis,

Actually, I only needed to look at the input side of the TDM to see what it was doing. Given the encoder type I pretty much expected the approach taken, it was no surprise. I have no detailed understanding of how things are done further down the pipe, and don't really need to anyway. The change I've implemented does not modify the TDM in any way, it just sits between the encoder and the TDM. Much to my surprise it all worked the first time :) I've let the developer know what I've done, he was not really sure that I was going to be successful during my early enquiries so he suggested getting the straight through encoder configuration just in case. Anyway, one fun challenge out of the way, now I need to check it out under the stars.

Oner other cool thing is that with the encoders powered outside of the AN I can push that ota around really quickly and there's absolutely no errors. Not bad for 20,000tic positioning resolution.

Cheers

David

[DGK]

I tested the TDM last night with the Argo Navis taking the position information from the encoder and it works well. The drift test using an Intes Micro M809 and webcam at f/24 is posted on the CN forum Dennis linked - similar to that seen earlier with the lower resolution scope, close to +/-1arcsec correction. With the AN being provided with 20ktic/rev the TPAS model is coming back at 35arcsec RMS which is very nice - +/-1arcmin pointing over the whole sky.

[Dennis]

Hi David

That's great news. It appears that the TDM system is ideally suited to your particular requirements and you also seem to have tailored the system to even better meet your needs – a double bonus.

I really do enjoy reading about these new products, brought to market my talented amateurs, especially when they work as intended and the end user is able to derive the benefits they were looking for.

You have posted some impressive looking data (updated) compared to the native GPDX before you fitted the TDM system.

Cheers

Dennis

[AlexN]

I posted in the thread on CN.. Definitely looks like a great improvement...

[DGK]

Last word from me on this, just posted pdf's of three 600sec drift test on CN. My mount RA tracking has been taken from 35arcsec peak to peak down to +/-1.25arcesec 90 percent interval. Hope some found it interesting, if maybe not useful to most.

Cheers

David

[Dennis]

Thanks for the wrap up David, the CN graphs certainly reveal the effectiveness of the TDM.

I’ll be keeping an eye on this product for my GPDX, although I am in two minds as I really don’t want to loose the Vixen Polar Alignment ‘Scope - I have come to rely on its ease of use, speedy set up and accuracy.

Cheers

Dennis

[Attila]

Hi Everybody on this forum-topic,

It is very nice, even more, delightful for me to read these skeptical and sometimes hostile opinions regarding TDM.

I am one of the two developers of TDM from Hungary and I can only say that if you do not like milk, please, do not drink milk. But, in spite of it, milk is a very good drink for others...

At the same time, I need to refuse Wavytone's claim: "The website also shows the author has a very naiive understanding of the causes of tracking errors."
Hey guys, there is intelligent life outside of Sydney as well...:welcome:

TDM is a working standalone application in practice but not just on "drawing board". MEADE Europe will sale it worldwide soon.

And let me have just one more sentence, please: TDM is NOT a competitor of autoguider technology but an alternative solution for a similar problem.

It is a bit more expensive compared to the cheapest autoguider system but much more cheaper than e.g. a Paramount ME. My EQ6 has less than +/-0.5" tracking error (with TDMv2) for a bit more than one tenths of the total investment of a Paramount which has +/-2 or 3" PE (or higher).

Each of the photographs of my website is true, there were exposed as I declared. Please do not insinuate me that I provide autoguided shots on my website.


Thank you,

Attila Madai
MDA-TelesCoop Llc.
Hungary

[Dennis]

Hello, Attila

:welcome:Welcome to Ice In Space.

It’s always nice to have the developers of new gear drop by, to provide their unique insight, knowledge and experience of their products.:)

When a new product comes along that offers a new or different method of managing RA errors, I guess it will challenge the established views? So, in many ways, the fact that the pot was stirred in such a heated manner is actually good news, as a less capable product might have passed by unnoticed.;)

So, I would take the skeptical comments as a sign that you are hitting the right target for the scenarios you have designed the TDM System for, and described so well on your website.:thumbsup:

Cheers

Dennis

[Attila]

Dear Dennis,

Thanks for your realistic words and for your welcome message above.
In spite of my limited time, I am willing to reply to your questions (if you have) sooner or later.

David has one of the TDM boxes but there are more than two dozens of TDM from the very first series in the world. EVERYBODY was satidfied with it and now we have the second version with higher accuracy and autoguiding capability. (And we have not finished the development yet...)

At least 90% of the questions arrived to this forum from skeptical or supporting people is explained on my website in details. Please read this at first.

TDM is not a "cure-all" product and I DID NOT CLAIME ANY FALSE OR DELUSIVE INFO ABOUT OUR TELESCOPE DRIVE MASTER!!!

We can definitely guarantee that your RA shaft will run on exactly sidereal or average King-rate (depending on jumper-settings) within +-1" (or better) accuracy in 95% of your exposure time within the explained limitations.
(By the way, just answering to one of the previous questions here, this TDM version provides AVERAGE King-rate but not position sensitive real King-rate. This is also explained in my website.)

But, if you have a "baggy" or "flaccid" mount and/or OTA, TDM will obviously not be able to change it to a professional instrument...

Astronomical measurement and photography needs very high quality hardware products and very precise human activity. TDM can help you to improve your existing mid-level mount's "mechanical quality" without changing it without spending ten thousands of bucks. (Nowadays it can be important point of view I think...)

But you need to do the rest of the job like polar alignment, fixing you flipping mirror, etc. :shrug:

Attila