DDM60 tracking within <1px

[MarkS]

I am in the process of working up my ASA10N/DDM60 system. I just wanted to share how spectacular the tracking can be.

 

Because it is to be mobile, travelling to a number of dark sites, I have been trying to achieve the required tracking performance with the least set-up time.

 

First light with the ASA10N - the DDM60 has been under the stars several times - I set the tripod as close as I could and then used 3-position same DEC solve  for PA errors. One iteration yielded reported PA errors of 1.6' RA and 1.2' DE.

 

I used just the second 3-position config, and went straight to MLPT set to 5 exposures along the track.

 

The target was NGC 6744, and I could only get 12 X 5min subs over about 65min total time before a heavy mist rolled in.

 

The enclosed image is approx 1/4 of the full frame of all the subs integrated WITHOUT registering. According to Pixinsight analysis, the maximum dx or dy between any of the subs was 0.61px. By any standards this is excellent.

 

Mark

 

 

[destrehandave]

Thanks for the report.

 

May I ask what other mounts you have set up remotely in the field... Astro Physics, Paramount, Celestron, Meade?

 

Can you please discuss the experience of accurately polar aligning; what steps you take, and how long it actually takes to perform each operation?

 

Thanks in Advance!

 

Clear Skies

 

Destrehan Dave

 

[jjongmans]

Can you please discuss the experience of accurately polar aligning; what steps you take, and how long it actually takes to perform each operation?

 

1. Place tripod or pier with bubble level (2 min.)

2. Place DDM60 on tripod/pier (< 1 min.)

3. Place counterweightbar, counterweights, OTA (5 min.)

4. Connect DDM60 to PC and start Autoslew (< 1 min.)

5. Point built-in laser at Polaris (2 min.)

6. Balance setup with help of Balancing Tool in Autoslew (5 min.)

7. Tune PID parameters, use the autotune feature in Autoslew (3 min.)

8. Use Sequence to create a 3-star pointing model (automated) to fine tune the polar alignment. (5 min)

9. Polar alignment routine; Autoslew will move star from center position, recenter with bolts, if you do this a couple of times (step 8 and 9) PA will be spot on. (5 min)

--- time spent a half hour ---

10. Create all-sky pointing model with Sequence (automated) or declination model (MLTP), both automated. MLTP is best for mobile setups IMO.

11. Start imaging session, unguided

 

You'll get faster every time...

[destrehandave]

Thanks, Jeffrey

 

Would you know if there would be any possibility that one could substitute TheSkyX camera add-in for Maxim DL?

 

I know that Maxim DL uses Pinpoint and TheSkyX uses TPoint; perhaps thats the deal breaker.

 

Clear Skies

 

DD

[Jay]

Thanks, Jeffrey

 

Would you know if there would be any possibility that one could substitute TheSkyX camera add-in for Maxim DL?

 

I know that Maxim DL uses Pinpoint and TheSkyX uses TPoint; perhaps thats the deal breaker.

 

Clear Skies

 

DD

As far as I know, it´s not possible...

[destrehandave]

Thanks, Gentlemen

 

Because there isn't quite as much information available, being a new technology, may I also ask what is the difference between the encoders used on the DDM60 and the DDM85?

 

It seems I've found a document that states there is an extra step in setting up the mount with the DDM60, because "the encoder resolution isn't know; it just knows tolerances."  It was also interpreted by another post that the DDM60 had magnetic encoders which were less precise than the optical encoders on the DDM85.

 

Do the encoders on the DDM60 have less precision than the DDM85?

[Jay]

 

 

It seems I've found a document that states there is an extra step in setting up the mount with the DDM60...

Setting up the DDM60 and DDM85 is done in the same way. The older DDM60 model used to have different kind of encoders and required some extra steps but not for quite a long time... 

[GeorgeCarey]

As Jay says, the encoders in 60 and 85 now work in the same way. I believe that the resolution in the 85 is slightly better than in the 60, presumably because the diameter of the encoders are bigger.

There is a difference in polar alignment between the two mounts. The 85 has a traditional azimuth, altitude system, but the 60 has a unique centre point tip, tilt arrangement.

Edited February 3, 2014 by GeorgeCarey

[nakbrooks]

and the 85 Pro/XL has no alignment at all - it is bolted rigidly to the XL pier and you align the whole pier, a one-time procedure for fixed installations.

[MarkS]

Hi Dave,

 

I am in the Southern Hemisphere, so I don't have Polaris to work with.

 

I use a digital inclinometer with accuracy of +/- 0.2 degree or better to set the tripod level.

 

At my favourite sites I have measured True South by the Sun at local noon. This is used to set Azimuth with the aid of a sighting tool placed on the DDM60 base.

 

The inclinometer is again used to set the OTA altitude to the latitude.

 

Balance is optimised with the Balance Tool in Autoslew. So far, I have tuned the system once, and repeatedly used the settings without rechecking.

 

I use the 3 star routine in Sequence for Polar Alignment. Two iterations are sometimes necessary.

 

When PA is within 1-2 arcmin, I either do a 21 star configuration and then MLPT, or just go straight to MLPT in Sequence. Both options have always given perfectly satisfactory tracking for 5 - 15 min subs.

 

My total set-up time including assembling the whole system is usually less than 1 hour - I do need to assemble in daylight for the Azimuth alignment.

 

Mark

[destrehandave]

Thanks, everyone for your input.

 

My mind is reasonably settled on this mount...

 

Does anyone have any feedback concerning the Software Development Kit (SDK)?  I know that the software seems very functional, and once you understand the perspective of providing tools to help with all of the processes involved. 

 

But software is a living being.  Windows 7 has a 32 bit and a 64 bit; Windows 8 is now 8.1 and Tablets and mobile devices are trending upwards.

 

The way I see it, this mount reasaonably competes with the Paramount MX (which has no encoders, but very good software), and the AP900 or 1100 (with or without encoders).  The Paramount has a good following, very mature software, and a very good software support staff.  There is a guarantee that their software will be supported in future OS upgrades, and one day, maybe even an adroid/iPad app since it, too, requires a computer.  The APs have a very powerful hand controller, so they 'win' the battle of not having to have a computer. 

 

The DDM60 is optimized for Astro-imaging, and from what I've gathered, is the superior device.  My only concern is how quickly it can be somewhat utilized in non-AP environments, such as public star parties, where the 'go-to objects' functionality without a full laptop would place it aeons ahead of the competiion.  It would match AP, and best Software Bisque..

 

And as I mentioned before, what happens when Windows 8.2, 8.3... 9xx is released on incresingly powerul mobile devices?

 

Are there enough programmers and/or even an ASA user community to keep up, at least keep Autoslew, etc, viable on the 'latest' platform? 

 

Nothing's perfect... just providing feedback on how ASA can further their competitive positions.

 

Thanks again..

 

Destrehan Dave

[lukepower]

Hi Dave,

 

that's an interesting question. The way I see it is that these mounts have been primarily built for astrophotography, where you anyway need a laptop/computer to work. Autoslew is written in .Net, so it should be quite easy to keep up with newer versions of Windows, as Philipp Keller seems to work quite alot on that piece of code.

But I admit that sometimes an integrated solution would be cool, something like a Raspberry Pi integrated in the mount.

I am just unsure on how well the mounts are suited for public star parties, as the sensitivity to balance issues (and people leaning against/pushing/pulling) might be a concern...

[destrehandave]

I am a road warrior... I go to remote sites, set up, and take my images. But I always spend a few minutes doing visual first.

With my AP900, I use the polar finder, balance for visual use, goto 15 or 20 I objects visually, then re-balance using the camera, etc.  I'm now in Astro-imaging mode.

It would be nice to plug-in the comupter, quickly and accurately balance the tube for visual use, reasonably polar align with an illuminated reticle eyepiece, disconnect the computer, plug in Southern Stars http://southernstars.com , and slew to a few nice visual objects prior to my imaging sessions.  There is nothing like an eye-to-eyepiece view of a bight cluster, galaxy, or and nebula.  Even Jupiter, Saturn, and the moon are very pleasant visual objects.  I don't get out much, and it's a great feeling to catch a quick glimpse of these gems before getting down to serious, imaging business.

 

Once I'm done with my little visual excursion, I'd like to disconnect Southern Stars, re-plug the computer, hook up the camera, and refine everything to imaging standards.  Even more amazing would be to use the wireless Southern Stars adapter and do the whole thing on both devices wirelessly.

Thanks for listening! Call me a dreamer

DD

Edited February 8, 2014 by destrehandave

[MarkS]

Hi again Dave,

 

Once the DDM is polar aligned - and to do this accurately you do need the camera - changing to eyepiece only requires rebalancing. Then I would just use TheSkyX to send the scope to wherever I want. (However, I tend not to to visuals with my ASA10N because a fast scope like this is not ideal for observing bright objects. For observing I like to use a APO refractor.)

 

The caveat here is that balance for photography is very critical, so it can take a while to optimise even if you have good starting marks on the equipment.

 

Regarding software etc, I use Windows 7 64 bit, but I am told there is no problem with Windows 8. What the future brings is anyone's guess!

 

Mark