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Equipment Discussions >> Mounts

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Tonk
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Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6109707 - 09/30/13 05:46 PM

Quote:

The shaft position encoders have a resolution to better than 1 arc second (will have to check manual for actual value)




Just looked it up - they state encoder resolution is 0.13 arc seconds giving in practice a RMS of 0.5 arc seconds tracking accuracy

This following quote from Ian King Imaging about the 10Micron mount is a claim I haven't yet verified for myself ...

Quote:

Tests with 3600 second long unguided exposures have show tracking accuracy within +/- 0.5 arc seconds.




However I can confirm that I had a test star remaining on the cross hairs of an astrometric 12mm eyepeice for 20 minutes. I stopped here because I was testing for planned 10 minute exposures. Scope FL was 600mm.


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famax
member


Reged: 07/01/07

Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6109720 - 09/30/13 05:54 PM

No particular point in my comment Gir, just wanted to clarify (or have someone to...) this point.
To say, and by reading the asa's forum , the DD seems very nice , but far more complexe than old school worm+encoders...
This is my feeling, and that led me to choose the 10µ.
By the way , and for other consideration , would a ddm 60 fit with in the field astrophoto ?

I think i would be great to read a real Pro/cons about the ddm60.


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GIR
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Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: famax]
      #6110396 - 10/01/13 12:10 AM

famax, the complexity comes from not bothering to read the manual
Usually things feel complicated when you don't know how to do them, once you do they're quite simple.
What comes to ASA, it really isn't that complicated just a bit different, and in return you'll get an astonishing mount.
I've already given my view on the the field use issue on another thread.


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Hilmi
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Reged: 03/07/10

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Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6110465 - 10/01/13 01:13 AM

I also find it a bit of a put off that the ddm60 doesn't have a matching tripod being sold by the manufacturer.

This tells me it was designed with permanent installation in mind


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6110466 - 10/01/13 01:14 AM

Quote:


Just looked it up - they state encoder resolution is 0.13 arc seconds giving in practice a RMS of 0.5 arc seconds tracking accuracy






Not trying to downplay 10Micron but just to compare...
ASA Renishaw encoders provide a 0.01-0.02 arc sec resolution, and can track around 0.2 - 0.4 arc sec depending on your setup.
With my quite stable system tracking seems to stay around 0.1 - 0.2 arc sec.

And a question... doesn't +/- 0.5 arc sec tracking mean 1 arc sec in reality ?


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Tonk
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Reged: 08/19/04

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Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6110556 - 10/01/13 04:02 AM

Quote:

Not trying to downplay 10Micron but just to compare...




I thought this excercise was to give experiences and (verified) facts. Its not about downplaying.

Ah at least we are learning what the ASA can do in a little more detail

Quote:

The thing is how does this particular solution - (worm drive + absolute encoders) really compare to a direct drive solution?




So for the numbers collected/quoted its approaching an order of magnitude in favour of the ASA direct drive. So it sound like these two mounts are actually in different classes.


For me the price (~Ł6,000) and performance has hit the sweet spot. The GM1000HPS tracks unguided longer that I can use due to sky conditions and my prefered targets (comets) - it tracks with an accuracy better than the resolution of my imaging system - I shoot with a pixel width of 2 arc seconds)

For me buying a mount that tracks at 0.1" accuracy is a pointless waste of money and this might might be so for others. I shoot comets and long focal length work disfavours these targets.

Finally the mount really is mobile and extremely quick to set up anywhere. On my first test runs I did PA from scratch 6 times and was typically down to a mean of 15 arc second error in 15 minutes of model building and PA correction (thats 2 or 3 iterations on 12-15 stars).

The mount is increadibly easy to set up in a short time - very much like the Losmandy/Gemini systems. However the GM1000HPS is also approaching an order of mag better at unguided tracking than my Losmandy GM-8

I 'd like to say something about the vendor who sold me the mount - I came to him with the desire to buy a Paramount MX but once I explained to him what I shoot, and with what scope, where I shoot and a desire to "keep it simple" and set up quick (no guiding gear or extraneous equipment) I was pointed at the GM1000HPS. I'd never heard of the mount at this point - so on trust and 2 hours of playing with the mount - I went with his recommendation and I certainly don't regret it. Good man is Ian King! (and with the money saved I got an AstroTrac and other goodies )


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6110568 - 10/01/13 04:26 AM

If I understood correctly ASA DDM60 or DDM85 is able to do 30min unguided imaging with my FL (<= 1000mm) and GM1000HPS or GM2000HPS can't (I believe it says so in manual).
For me that could be deciding point. If I'm buying expensive mount (for observatory), unguided shooting is very nice.
GIR, how much error can I expect unguided 30min with 1000mm refractor? Is there someone that have similar setup?


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orion69]
      #6110575 - 10/01/13 04:37 AM

I "heard" that ASA has moved from the Renishaw optical to the Renishaw / RLS magnetic encoders. Since the RLS encoders are 1um resolution with 2000-fold interpolation, I can't see how they can manage 0.01 arc-seconds.

I do know that the Renishaw Resolute ETR used in the AP 1100/1600 are capable of about 0.01 arc-seconds (sub-divisional error). But these are optical, and magnetic encoders are less accurate.

But then again that's just what I "heard." Take with multiple chunks of salt.


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orion69]
      #6110599 - 10/01/13 05:30 AM

Knez

You might want to ask that question from the ASA forum, and get more detailed answer. All I can tell that ASA mounts do perform very accurately when tuned and balanced properly.
The closer you'll get to the maximum (weight) limits the more careful you'll have be with the tuning and balancing.

I'm using a two scopes (600 mm and 300 mm FL ) and should be able to take as long exposures I want. However, haven't taken more than 20min subs (NB) so far because prefer to have at least 10 subs for each channel. Even with that the overall exposure time is 10 hours. Besides I've been shooting rather bright targets so far.

I will test longer subs sometime during the winter with the 600 mm (e.g. 60 minutes) just to see what happens but it's not really an important issue for me. The thing I've enjoyed the most (besides complete silence and unbelievable accuracy) is the ability to do unguided imaging. Guiding is not complicated but once you've gotten used to taking unguided pictures, it would be very difficult to go back for using guider scopes.


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orlyandico
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Reged: 08/10/09

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Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6110601 - 10/01/13 05:42 AM

Actually unguided imaging is not the exclusive preserve of direct-drive or encoder-equipped mounts.

I can do 600mm unguided subs for 10 and even 20 minutes with my ancient gear-driven encoderless mount. This is assuming the target is high enough above the horizon that atmospheric refraction isn't a factor (I don't have APCC Pro).

Basically above 45 degrees altitude I can do 10 minutes all the time at 600mm focal length (2.68"/pixel) and 20 minutes most of the time (say 50% keeper rate).

When altitude drops below 30 degrees I start getting exposures trailed in RA even on the 10-minute subs.


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orlyandico]
      #6110608 - 10/01/13 05:53 AM

Quote:

Actually unguided imaging is not the exclusive preserve of direct-drive or encoder-equipped mounts.

I can do 600mm unguided subs for 10 and even 20 minutes with my ancient gear-driven encoderless mount. This is assuming the target is high enough above the horizon that atmospheric refraction isn't a factor (I don't have APCC Pro).

Basically above 45 degrees altitude I can do 10 minutes all the time at 600mm focal length (2.68"/pixel) and 20 minutes most of the time (say 50% keeper rate).

When altitude drops below 30 degrees I start getting exposures trailed in RA even on the 10-minute subs.




I need 30 min, and that must be routinely and very precise.
Throwing subs is not an option. If you have to throw subs that means mount is not capable for the task.


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famax
member


Reged: 07/01/07

Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orion69]
      #6110609 - 10/01/13 06:00 AM

Quote:

If I understood correctly ASA DDM60 or DDM85 is able to do 30min unguided imaging with my FL (<= 1000mm) and GM1000HPS or GM2000HPS can't (I believe it says so in manual).
For me that could be deciding point. If I'm buying expensive mount (for observatory), unguided shooting is very nice.
GIR, how much error can I expect unguided 30min with 1000mm refractor? Is there someone that have similar setup?




No, gm1000 and 2000hps can do very long unguided exp.
According to Per.

Some numbers here :

see :

http://www.astronamis.net/t2561-1-essai-10-microns-hps1000#32609
and
http://www.astrosurf.com/heidemann/Test%20GM1000HPS.pdf


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orlyandico]
      #6110610 - 10/01/13 06:00 AM

Quote:

Actually unguided imaging is not the exclusive preserve of direct-drive or encoder-equipped mounts.

I can do 600mm unguided subs for 10 and even 20 minutes with my ancient gear-driven encoderless mount. This is assuming the target is high enough above the horizon that atmospheric refraction isn't a factor (I don't have APCC Pro).

Basically above 45 degrees altitude I can do 10 minutes all the time at 600mm focal length (2.68"/pixel) and 20 minutes most of the time (say 50% keeper rate).

When altitude drops below 30 degrees I start getting exposures trailed in RA even on the 10-minute subs.




I'm sure you can after having perfect polar alligment and tuning everything well. But that's not the issue here. As far as I know ASA mounts are cabable of taking unguided images with far longer FLs than 600mm. It's just the way I'm using the mount.

I've tried taking unguided images with my Losmandy G11 and failed miserably. Maybe someone is able to do that but I wasn't. Now all I have to do... after Autoslew/Sequence polar allignment, and making completely automated pointing model and if being picky add "local" pointing model on top of that...is to "point and shoot". It doesn't matter if I'm taking 1 sub or shooting several hours. The only thing I have to think about is the Meridian flip if using the local pointing model. And as far as I know the next Sequence version will automate even that. It's so freaking easy ...and that's what I'm paying for.


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famax
member


Reged: 07/01/07

Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6110623 - 10/01/13 06:19 AM

What i find nice with the asa's is that there's a lot of thing to play with, and a lot of feeback from the system itself, giving good advice if you have flex in your system for exemple.
One could find it a bit complex , but i prefer this approach than the one of 10µ which is not very generous about the things hidden behind the model.

In fact, i would prefer a ddm for a static use , and a 10µm for in the field ops.


some more unguided tests :

http://stargazerslounge.com/topic/174111-best-mount-for-imaging-5k-6k-budget/...

Edited by famax (10/01/13 06:48 AM)


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jjongmans
super member


Reged: 02/11/12

Loc: The Netherlands
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: famax]
      #6110693 - 10/01/13 07:46 AM

I'm using a DDM60.
I also did some unguided tests: link
My website: link


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Tonk
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Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: jjongmans]
      #6110715 - 10/01/13 08:17 AM

Quote:

gm1000 and 2000hps can do very long unguided exp.





Yes - absolutely. I've seen Per's results. I've tested myself to 20 mins (once @ FL 600mm) and IK Imaging claim 1 hour unguided (but don't say at what FL).

Collecting reports - this GM1000HPS review ...

Quote:

http://www.astrosurf.com/heidemann/Test%20GM1000HPS.pdf




... (Using Google translate) reveals that the review authors had perfect round stars after 10 minutes unguided at FL 2800mm

Then this GM1000HPS review/test ...

Quote:

http://www.astronamis.net/t2561-1-essai-10-microns-hps1000#32609




... has the author getting round stars at 25 minutes unguided @ FL 1080mm but at 40 minutes the stars are clearly oval.

For the ASA ...

Quote:

http://stargazerslounge.com/topic/170735-mission-accomplished-20-minuted-unguided-with-asa-ddm60/




... we have 20 minutes unguided @ FL 1383mm





Quote:

In fact, i would prefer a ddm for a static use , and a 10µm for in the field ops.




I would agree with this approach - oh if I could afford 2 mounts !


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Starhawk
Space Ranger
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Reged: 09/16/08

Loc: Tucson, Arizona
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6110954 - 10/01/13 10:45 AM

Well, I have started off on a 10 Micron GM1000HPS test drive. So far I have just had it out one evening and started imaging with a C11 at 2800mm f/10 and experimenting with the Starizona f/7.5 reducer/flattener.

I haven't even pulled the images off the camera card yet- I promise to put centers and corners here when I do. Here are some first impressions- it's still in free form stream of consciousness in my mind. I'll have a much more organized impression of the mount when I get more time on it.

So far, the main observations I have are the mount is very complete in its standalone mode. The control box is about the size of the box for 7x35mm binoculars, so it is quite a bit larger than the CP 3 on a Mach 1. The plugs are all pointed up on the top. There isn't a hard mount bracket with the one I am using. Just one cable goes to the mount, and it goes between non-moving components. The mount powers on by pressing a power switch which looks like a mini rocker, but is actually a momentary switch. The mount boots and displays the startup status on the hand control as it goes through its checkout, which ends with an attempt to poll a GPS device.

The hand controller is also larger than the one on the Mach 1 GTO, and has true backlighting for the keys so it has very good legibility I. The dark.

The axes are very different from a Mach 1 GTO since they are free-turning when the clutches are released. So, balancing feels more like a CGEM in both axes. The dual vixen/Losmandy dovetail clamp was white secure though the first time I dropped the c11 into it in the dark, a leg went in the vixen slot and it wasn't obvious in the dusk, so pay attention before letting go.

The counterweights are very nice stainless steel cylinders with bronze clamping pins, but no bronze bushings like AP weights. The weight shaft is very close in size to the one on a Mach 1 GTO, but just large enough so 10Micron weights will go on a Mach 1 GTO, but Mach 1 weights will NOT go on the GM1000HPS. The shafts have radically different threads, so the mount can't be easily adapted that way, either.

The drive is something very new to me. It moves with power and authority with very little noise. 15 degrees/ second is really quick. I just did a 2 star align and then went on to a polar alignment. It was surprisingly easy, and from initial indications, extremely accurate. With more time I will try out making a true pointing model.

The drive constantly makes a soft sound like rubbing on something like a rubber surface from the high speed updates to the drive. In the eyepiece, the image is stationary. I took a series of 25 second exposures over 6 minutes at the focal lengths mentioned above. I'm thinking of stacking them without aligning to get some indication of the mount movement accuracy.

The wood 10Micron tripod is quite stout, and I was able to leave my hand on the C11 focus knob while focusing without jitter. I'll have to try that on the Mach1 GTO/ eagle pier combination to see what happens.

That's about all I have at the moment- I'll post back when I get my pix put together.

-Rich

Edited by Starhawk (10/02/13 10:06 AM)


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Per Frejvall
sage


Reged: 09/28/12

Loc: Saltsjöbaden, Sweden
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Starhawk]
      #6111330 - 10/01/13 02:15 PM

Starhawk!

You are welcome to use my pointing/tracking model maker to speed things up. Available on my site.

I have one question regarding ASA. Does it need homing and does it home 100 percent reliably? Being a remote buff this is a queston of great importance.

Both ASA and 10Micron produce formidable mounts, and it is interesting to note the notes from a few more 10Micron users, most of which seem to be on the positive side. For true remote use it really is a good choice.

Want to hear a disadvantage? Well, the momentary switch that turns the mount on and/or off is available in a 3.5mm plug. Naturally, a scripted mount power on/off function is thus easily accomplished. There is, however, no way of knowing if the mount is on or off... Best bet is to wait 30 seconds (longest boot time) and ping it. If it replies it is on and you can pulse the thing to turn it off.

Not a big thing, really

/per


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Per Frejvall]
      #6111363 - 10/01/13 02:38 PM

Quote:


I have one question regarding ASA. Does it need homing and does it home 100 percent reliably? Being a remote buff this is a queston of great importance.





I have a backyard observatory and I do homing just in case. Some ASA remote user don't do any homing because they know that the mount hasn't been moved.

Homing really isn't a big deal. Just create one parking position near the homing place, go there and the mount will start searching the homing position. Usually it'll take couple of seconds.
I don't think there is 100 % reliability in astrophotography but for me homing has never failed.
And if it would for some reason, all you have to do is to move the mount close to the homing position with Autoslew key pads and push a button. The mount will automatically start searching the homing position in a certain order ...and will always find it.

Of course if I'd have a truly remote observatory I'd install a camera to see what the mount is doing. Well, actually I do have a camera already because it's kind of neat to sit on the sofa and play with the mount remotely using a laptop


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6111409 - 10/01/13 03:07 PM

I'm actually doing that right now... taking couple of missing 10 min SII subs and then continue with another target. Here is how it looks like from the living room sofa


laptop view


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