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SL63 AMG
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Williamson, Arizona
ASA DDM85X-SL - Keeps getting better
      #5427735 - 09/18/12 04:18 PM

A year and a half ago I purchased an ASA DDM85XL-S.

It was a big leap for me, not so much due to the cost, but mostly due to the learning curve. Not only was there a huge learning curve for the mount, but I started from scratch knowing little to nothing about astronomy, astrophotography, mounts, collimation, cameras, filter wheels and most of all, image processing.

I kid you not; there were no gradients in my knowledge, just pure green (me)!

Enough of that, let's talk about the mount.

First, I encourage you to read my review of the ASA DDM85XL-S Direct Drive GEM

It's not the best writing in the world, but I think it gets the point across...this is an excellent mount for astrophotography!

So I find myself, a year and a half later, becoming quite knowledgeable on this mount...and it keeps getting better.

I recently upgraded my Autoslew software that controls the mount with version 5.1.0.0 and the plate solving software to Sequence version 9 by Dipl. Phys. Dr. Philipp Keller.

Dr. Keller has made major improvements to the software, specifically in the Advanced Pointing model of Autoslew and the Multipoint Local Precision Tracking portion of Sequence.

What seemed like required an advanced degree in astrophysics to operate and understand can now be down quite easily by a greenhorn like me. All of the advanced pointing and modeling functions are now completely automated.

I am now consistently able to achieve polar alignments equal to or less than 6 arcseconds in both axis in about a half hour after setting up the mount and then create a substantial pointing model within another 30-45 minutes. Once completed, I can select an object, create a MLPT model in 2-12 minutes depending upon the length of my exposures and the number of iterations I select and then I can achieve 20-30 minute subs with no periodic error, no backlash and most importantly, no guiding.

The pointing accuracy is very good but it is the tracking capabilities that are absolutely amazing.

When I am done imaging for the night, I simply park the scope, cover it and it's ready for the next evening of imaging.

If I need to shut off the power or remove the laptop for any reason, that's cool too. I make sure I point the scope at a star in the eastern horizon, synch to that star and then Autoslew calculates the angular offset between the synched star and the encoders home position. It then uses your coordinates, date and time and that angular offset to determine exactly where to point after you power up and perform a HomeFind. In other words, it never forgets where it is positioned once a 30 second home find is performed on power up.

Here are some images of the mount and some taken using the mount. They are a combination of 10 and 20 minutes subs with no periodic error, no backlash and most importantly, no guiding.







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Alph
Carpal Tunnel


Reged: 11/23/06

Loc: Melmac
Re: ASA DDM85XL-S - Keeps getting better new [Re: SL63 AMG]
      #5427851 - 09/18/12 05:12 PM

I have written off the ASA DDM mounts for a couple of reasons:
- Payload capacity, DDM60 too little, DDM85 too heavy
- Subpaar machining. Those mounts donít look they are worth the money.
- Difficult to operate mechanically. The azimuth adjustment range is too small. The lack of easy axes locking mechanism makes OTA mounting a royal pain in the Ö
- Frequent problems with PID parameters. Many users reported tracking errors after 10 minutes or so of continues tracking (no manual axis movement). ASA has no fix yet.
- Price is way too high
- Poor customer support.
- Shipping the DDM85 to ASA for repairs is very expensive.


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Peter in Reno
Postmaster
*****

Reged: 07/15/08

Loc: Reno, NV
Re: ASA DDM85XL-S - Keeps getting better new [Re: SL63 AMG]
      #5427898 - 09/18/12 05:34 PM

Thanks for the well written report. It looks like you got a great mount.

Peter


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SL63 AMG
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Williamson, Arizona
Re: ASA DDM85XL-S - Keeps getting better new [Re: Alph]
      #5427914 - 09/18/12 05:45 PM

I think you need to do your homework, or at least keep up with the progress of ASA.

Quote:

I have written off the ASA DDM mounts for a couple of reasons:
- Payload capacity, DDM60 too little, DDM85 too heavy

ASA DDM60 - 55lbs
ASA DDM85 Basic - 100lbs
ASA DDM85 Standard - 143lbs
ASA DDM85 Premium - 220lbs


- Subpaar machining. Those mounts donít look they are worth the money.

Subpar? Based upon looks? These mounts are CNC machined and high quality.

- Difficult to operate mechanically. The azimuth adjustment range is too small.

Not sure how much you think you need, but after pointing the mount near polaris, lighting polaris up with the laser, there really isn't much adjustment needed. I think what they offer is overkill. I simply hold up my pinky finger at arms length against polaris on the Kochab side and spot the laser to the other side of my pinky. I find myself polar aligned within 5 to 8 arc minutes every time, then run a sequence plate solving 10-15 stars and my polar alignment is typically less than an arc minute and often within 6 arc seconds if I am really maticulous about centering stars in the crosshairs of the CCD image.

The lack of easy axes locking mechanism makes OTA mounting a royal pain in the Ö

Using a metric #8 hex tool to tighten a locking bolt is a pain? Seriously? I have no trouble mounting my Astrotech 12" RC all by myself. I find it much easier then setting up a Celestron CPC1100 for mount, especially on a wedge!

- Frequent problems with PID parameters.

This issue is fixed in Autoslew 5.1.0.0. There are now presets depending on the size and weight of your system. Only minor adjustments are needed from the preset. Once you set the values and balance the scope using the wicked cool software balancing system, you save your scope to a profile and forget it. I change scopes and with a click all my settings are spot on.

Many users reported tracking errors after 10 minutes or so of continues tracking (no manual axis movement). ASA has no fix yet.

I am not sure what you mean by "no manual axis movement" but if people are having tracking issues after 10 minutes, then they aren't setting up properly. If you do a good polar alignment (30 minutes) and make a good pointing model (30-45 minutes) then use MLPT for tracking, you can't miss. 20 minute unguided subs are easily attainable even for a beginner like me. The images in my post speak for themselves. For those that need to autoguide, you can do that too, but really, it is unecessary unless you want subs greater than 40 minutes.

- Price is way too high

Too high is relative. By the time you buy any other mount, add all your guiding accessories, you'll spend as much as a DDM60. My images speak for themselves. It's worth every penny!

- Poor customer support.

My experience is different. There is a time zone difference and a language barrier, but when I had an issue with an early model DDM60, I traded up and ASA brought my DDM85 NEAF, used it as a demo and gave me a great discount!

- Shipping the DDM85 to ASA for repairs is very expensive.

You got me here!





If you have never owned one, how can you comment on service and support, machining, etc, etc?


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herrointment
Post Laureate
*****

Reged: 03/12/11

Loc: North of Hwy. 64
Re: ASA DDM85XL-S - Keeps getting better new [Re: SL63 AMG]
      #5428048 - 09/18/12 06:46 PM

We all have opinions....

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SL63 AMG
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Williamson, Arizona
Re: ASA DDM85XL-S - Keeps getting better new [Re: herrointment]
      #5428065 - 09/18/12 07:01 PM

Quote:

We all have opinions....




True, but which opinions have value? Opinions based on actual use and fact or opinions based on heresay and conjecture?

I don't mind anyone giving an opinion even if it is negative, but when that opinion is given as a deliberate attempt to completely discredit a product when it is obvious the person giving the opinion has no direct experience with that product, that opinion has little value.

I wanted to be sure to make that clear my rebuttle above.

If you look at the images it's quite obvious the product does exactly what it is designed to do and does so even while in the hands of an inexperienced operator...like me.


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psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: ASA DDM85XL-S - Keeps getting better new [Re: herrointment]
      #5428094 - 09/18/12 07:24 PM

Hats off to you for having a great mount. I've been keeping my eye on the ASA mounts (and their scopes) for a while, but always thought that using them mobile might be a bit much. You've shown it not only can be done, but that it's working very well.

Cool and congrats!

Paul


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Psyire
Pooh-Bah
*****

Reged: 06/24/07

Loc: 55* North
Re: ASA DDM85XL-S - Keeps getting better new [Re: psandelle]
      #5429200 - 09/19/12 01:06 PM

Dave, Thanks for the update/review! I've been watching these mounts for quite awhile as I'm seriously thinking about a 'big' upgrade in the near future. ASA is definately on my list..

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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: ASA DDM85XL-S - Keeps getting better new [Re: Psyire]
      #5429351 - 09/19/12 02:34 PM

Dave, I'm very interested in ASA DDM60 mount, price is NOT that high for mount of that quality, payload capacity is enough for me (max 6" refractor) and Austria is not very far.
So probably my next mount, thanks for review!

Knez


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petely
member


Reged: 01/06/11

Loc: England
Re: ASA DDM85XL-S - Keeps getting better new [Re: Alph]
      #5429554 - 09/19/12 04:53 PM

Quote:

- Price is way too high


I suppose all things are relative. Where I am the DDM85 compares favourably with the paramount ME in terms of payload and price.

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Nezar H
member


Reged: 08/11/11

Re: ASA DDM85X-SL - Keeps getting better new [Re: SL63 AMG]
      #5460808 - 10/08/12 03:11 PM

Quote:

It was a big leap for me, not so much due to the cost, but mostly due to the learning curve. Not only was there a huge learning curve for the mount, but I started from scratch knowing little to nothing about astronomy, astrophotography, mounts, collimation, cameras, filter wheels and most of all, image processing.

I kid you not; there were no gradients in my knowledge, just pure green

So I find myself, a year and a half later, becoming quite knowledgeable on this mount...and it keeps getting better.




I expect that your IQ is very high .. I'm very pleased with your participation and your comments! and really motivated me to rather more effort to get to a better level than I am now.

GoodLuck and I wish for you all the Best.

Nezar.


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Mkofski
Pooh-Bah
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Reged: 07/19/11

Loc: Greenfield, Indiana, USA
Re: ASA DDM85X-SL - Keeps getting better new [Re: SL63 AMG]
      #5460840 - 10/08/12 03:30 PM

No way to argue with the results! Your pictures are stunning! If I am ever in the position to spend $20K on a mount, I'd certainly consider one of the ASA offerings. That reminds me I need to start buying lottery tickets.

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korborh
professor emeritus
*****

Reged: 01/29/11

Re: ASA DDM85X-SL - Keeps getting better new [Re: SL63 AMG]
      #5461545 - 10/09/12 02:10 AM

SL63, congrats on the mount and those great images!

How long have you been able to image unguided and how well is flexure modeled ? Do you find it worth the time and effort of modeling rather than autoguiding? Do you see any flexure in 30min images?


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SL63 AMG
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Williamson, Arizona
Re: ASA DDM85X-SL - Keeps getting better new [Re: korborh]
      #5462066 - 10/09/12 12:52 PM

At this time, the longest unguided subs I have taken with the mount are 1200s (20m) using the MLPT tracking with Sequence 9.

I am confident I can do 30 minute unguided subs and I may very well try it next week during the new moon cycle. I just need to find an object like my LBN438 image where I need deep exposures.

I am using a complete ASA system and I don't have much flexure. All of the components are either screwed together or attached using 6 screws. Everything is very well machined and fits tightly.

Sequence 9 and Autoslew will measure the flexure and collimation error of the system. I have never seen these numbers very high. The neat part is unlike hysteresis; flexure and collimation error can both be measured and thus corrected by software. That's exactly what the ASA software does!

With regards to the time spent modeling the system versus guiding, I definitely find it worth the time. In fact, this wouldn't even be a question if I were in a permanent observatory because I would do it once and forget it. Unfortunately, I have to setup every new moon cycle but I leave the system setup for up to 10 days at a time.

It takes me just a few hours the first night to setup, dial in my polar alignment, model the system with a large pointing file and then I only have to run an MLPT model for each object I image. The MLPT model takes less than 15 minutes for about 30-40 images.

So the answer to your question is, yes I think it is worth the time. I never have to worry about finding a guide star, thin clouds blocking my guide star of any of the guiding issues. They simply do not exist for me. There is, however, a bit of a steep learning curve to figure all this stuff out, but with more people using the ASA mounts, there are a lot more helpers out there to get the next guy started.

Personally, I think someone spending two nights with me could learn this system quite well. There are a lot of steps each with many details that must be remembered, but none of it is so complicated that the average guy cannot understand it, figure it out and repeat it.

Here is an image of LBN438 that was made with 20 minute unguided LRGB subs binned 1x1

LBN438 High Resolution


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johne
sage
*****

Reged: 11/10/06

Loc: Prescott, AZ.
Re: ASA DDM85X-SL - Keeps getting better new [Re: SL63 AMG]
      #5463525 - 10/10/12 10:14 AM

Just sticking my nose in here for a second...

I happened to have the pleasure of spending some time with Dave and his ASA system last night. I have a Paramount ME (which I am very satisfied with), but Dave's ASA is simply amazing and accurate. The mount is incredibly fast and whisper quiet when performing slews, expecially when compared to the ME. LOL, the focuser was louder than the mount. I'd say you need to be alert and keep your wits about you when slewing, lest you get "whacked in the head", if you're not paying attention.


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jmiele
Patron Saint?
*****

Reged: 12/04/10

Re: ASA DDM85X-SL - Keeps getting better new [Re: johne]
      #5463548 - 10/10/12 10:25 AM

This is great to hear. These mounts have shown great potential in the hardware for some time. Now that the software is sorted, it seems they are performing wonderfully. Dave's results are stunning. BTW Dave, the processing is also super! Getting solid data is just the first part. His images are great.

Best, Joe


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morten
super member


Reged: 07/22/08

Loc: Denmark
Re: ASA DDM85X-SL - Keeps getting better new [Re: jmiele]
      #5475593 - 10/17/12 06:01 PM

Kudos Dave. What excellent photos. I considered the ddm60 in 2010, but felt that it was immature and went conservative with a ap900. Your description of your journey is a fantastic read.
It seems that you set up on a tripod on each session. How long does it take you to get the mount aligned and running?


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BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: ASA DDM85X-SL - Keeps getting better new [Re: morten]
      #5478226 - 10/19/12 04:08 AM

Nice write up and images.

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jjongmans
super member


Reged: 02/11/12

Loc: The Netherlands
Re: ASA DDM85X-SL - Keeps getting better new [Re: BPO]
      #5484767 - 10/23/12 04:13 AM

I ordered an ASA DDM60 PRO 7 weeks ago to update my EQ6. I did a lot of research and also looked at other mounts like 10Micron, Mesu, Paramount and Astro-Physics. The improving results of the ASA pioneers (like SL63 AMG) helped me decide to choose the ASA. I'll receive it in the next 2 weeks, when the custom pier is ready.
I'm going to use it with an GSO 10" RC, with a FL of 2000mm@f/8. I hope to get 30 min. unguided subs with this setup.


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morten
super member


Reged: 07/22/08

Loc: Denmark
Re: ASA DDM85X-SL - Keeps getting better new [Re: jjongmans]
      #5485363 - 10/23/12 02:03 PM

congratulations!! I can't wait to hear about your experiences.

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SL63 AMG
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Williamson, Arizona
Re: ASA DDM85X-SL - Keeps getting better new [Re: morten]
      #5489747 - 10/26/12 06:18 AM

Thanks for all the kind comments. I am really enjoying the ASA DDM85 mount. I think ASA has made a huge improvement to the DDM60 with the addition of fixed encoders on the axis. I had my DDM60Pro prior to this improvement and wasn't really happy with it, but I am sure the DDM60Pro is a fine mount with fixed encoders.

Knowing my experience with the DDM series mounts, I would not start out with a FL length greater than 1000mm. JJ, I think you may set yourself up for some frustration expecting to achieve 30 minute unguided subs at 2000mm FL right away. It's possible, but you'll need to really know the system well first.

I highly reccommend that you start with a simple telescope under 1000mm FL and first work on obtaining a very good polar alignment and achieving 5 minute unguided subs. As you get to know the software, particularly Sequence 9, plate solving and it's interaction with Autoslew, you can then venture into 10m subs and longer, Sometimes I still struggle with 20m unguided subs at 950mm FL f/3.6, yet I have on several occasions been able to shoot 20m unguided subs as 2432mm FL F/8 using my AT12RC.

At the longer focal lengths every error in your system is amplified greatly.

There are many things that come into play that can ruin an unguided sub, particulaly at higher FL. For example, I believe I have some flexure issues with my AT12RC which currently utilizes a FeatherTouch focuser. While I like the FeatherTouch focusers and MicroTouch controller system, I do not like the way it attaches to the AT12RC telescope and I believe it is likely the cause of both flexure and tilt in my current system.

I am replacing the FeatherTouch with an FLI Atlas focuser and a precision adapter for both my FLI ML8300, a future PL16803 and a TAK collimator.

It is critical to obtain precise collimation and it really isn't possible with my current focuser and even if I did obtian critical collimation there is no way to ensure the collimator and the camera chipset will both be aligned with the same optical axis.

Once I replace the focuser with the precision couplers for both the camera and the collimater, I am pretty sure this issue will be resolved and I'll be able to shoot 20-30m subs at 2432 with repeatable results.

So basically, I am telling you the mount is perfectly capable of the results you seek, but that doesn't necesssarily mean you will get those results everytime you setup your mount, but if you keep the FL shorter while you are learning how to deal with all of the issues you are sure to encounter, you'll keep your sanity.

Morten, it takes me about two hours to setup all my gear prior to sunset, then another two hours to get everything polar aligned to within 6-12 arc seconds. If I were only shooting subs at 5m, I could have everything polar aligned and a pointing model built in about 30 minutes, but since I leave my system setup for an entire new moon session, I tend to count the first night as a setup and test night and I am willing to spend most of the night tweaking the entire system for perfection.

If I had a permanent setup, I would dedicated several days to this process to get it perfect and then be done with it.

Of course you have to take into a account that I have done this process over and over again for almost two years now, so I am very good at setting up the system in a portable environment.

It takes time to learn the system, then more time to practice the process of setting it up and aligning everything in a repeatable without making a lot of mistakes.

Personally, I like the challenge. This whole astrophotography hobby is a very technically challenging endeavor and that is what keeps me interested.

JJ, congrats on your new mount. I just wrote some procedures for getting started with tuning the motors and balancing. You can find the information on the Yahoo group. Read it carefully and it will save you some time when you first setup your DDM60Pro. Getting the servo motors properly tuned and balancing the system using the provided tools is also critical to achieving long unguided exposres.

JJ, I notice you have a QSI683wsg camera. Since this camera has a pick off prism mounted in front of the filters, I highly recommend that you purchase a Lodestar camera to use for autoguiding at long FL. While the mount is perfectly capable of unguided exposres, having an OAG and autoguiding at FL's greater than 1500mm will ensure perfect results, especially for subs >=20m, such as may be necessary for Ha, SII, NII and OIII narrowband imaging.

I intend to purchase an OAG for use with my AT12RC for 30-40m subs. Although I have not yet tried autoguiding with the DDM series mounts, I have read about it and it seems to be straight forward and relatively simple to do.

Enjoy your new mount and let me know if you have any issues with which you need help.


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jjongmans
super member


Reged: 02/11/12

Loc: The Netherlands
Re: ASA DDM85X-SL - Keeps getting better new [Re: SL63 AMG]
      #5489763 - 10/26/12 06:52 AM

Hi Dave, I'm not completely new to astrophotography and I also know a few things about PID controllers, but it will be hard to get good results in the beginning. I already have the Lodestar, so I can switch to guided imaging if the unguided results are no good. I managed to get good results on a EQ6 with 2000mm FL. I upgraded my focuser with a Moonlite high resolution stepper focuser, so I can use FocusMax to autofocus in an automated setup with CCDAutoPilot.
I already read your procedures on the Yahoo group


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SL63 AMG
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Williamson, Arizona
Re: ASA DDM85X-SL - Keeps getting better new [Re: jjongmans]
      #5490302 - 10/26/12 02:02 PM

I understand. I apologize if I implied in any way that you were new to astrophotography. I only meant to imply that with the mount coming with a bit of a steep learning curve it may be less frustrating to get started using a shorter focal length telescope in the beginning.

I visited your web site. Not only are your images remarkable, but also quite informative about each of the objects displayed.

I hope you enjoy the new mount.


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jjongmans
super member


Reged: 02/11/12

Loc: The Netherlands
Re: ASA DDM85X-SL - Keeps getting better new [Re: SL63 AMG]
      #5490407 - 10/26/12 03:10 PM

Hi Dave, you don't have to apologize! I am new to it, I started 2 years ago. I really enjoy reading your stories about this DDM, I think I can learn a lot from your experiences! Keep up the good work

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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: ASA DDM85X-SL - Keeps getting better new [Re: jjongmans]
      #5490629 - 10/26/12 05:55 PM

Are there any differences or advatages between guided and unguided tracking (and vice versa) if mount is correctly polar aligned?
Why would I shoot unguided if I can guide (disregarding you don't have to worry about guiding star or seeing)?


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BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: ASA DDM85X-SL - Keeps getting better new [Re: orion69]
      #5490877 - 10/26/12 09:11 PM

If you already have a good geared mount and guiding setup, there is probably little reason to ditch it in favour of one of these direct drive mounts, unless you really want to get rid of the guiding rig.

For a new setup, it makes a lot more sense. Once the user gains the necessary experience and has trained the mount, an external guiding rig becomes unnecessary; Indeed, counter-productive.

But it needs to be borne in mind that these mounts are a major step up in most ways. They are much closer to professional observatory technology than other kinds, and the demands on the user's ability and knowledge increase, at least at first, although the pay-off is significant.


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SL63 AMG
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Williamson, Arizona
Re: ASA DDM85X-SL - Keeps getting better new [Re: orion69]
      #5522888 - 11/16/12 01:09 PM

Quote:

Are there any differences or advantages between guided and unguided tracking (and vice versa) if mount is correctly polar aligned?
Why would I shoot unguided if I can guide (disregarding you don't have to worry about guiding star or seeing)?




I believe the advantages are significant.

With this mount, you have no backlash, no periodic error and without guiding, you eliminate a whole series of other potential issues, such as difficulty finding a guide star for long FL image. You eliminate issues such as how to guide, with an off-axis guider or a guide scope that may have flexure issues. Where do you place the guide chip, in front of or behind the filters, such as SBIG's cameras.

Certainly, guiding is not impossible, but I think it is a challenge in and of itself for beginners. So if you are going to spend hours learning how to setup and autoguide and solve all the nuances surrounding autoguiding, why not learn this mount and eliminate the need to autoguide altogether?

Then, once you have learned the mount and you decide, heck, I'm bored and want to learn something new, you can still autoguide using this mount!

In fact, I am going to learn to do it with my AT12RC so that I can take very long NB guided exposures at 2432mm focal length.

The joy is, however, that when using my ASA N10 or a small refractor, or even the AT12RC for exposures of 20m or less, I don't have to autoguide.

My polar alignment right now is >6 arc seconds error in RA and 6-8 arcseconds of error in DEC.

I can turn on the mount and start a 5 minute image and get perfect stars zoomed to 8x full resolution without even running MLPT.

Seriously, that's amazing.


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korborh
professor emeritus
*****

Reged: 01/29/11

Re: ASA DDM85X-SL - Keeps getting better new [Re: SL63 AMG]
      #5523463 - 11/16/12 09:02 PM

Auto-guiding is actually quite simple to do. Also finding guide-star in OAG is easy with calibrated FOV and planetarium software.
What is perhaps much harder is to maintain delicate and large pointing models and tune a complicated open loop system and hope that un-guided works


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SL63 AMG
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Williamson, Arizona
Re: ASA DDM85X-SL - Keeps getting better new [Re: korborh]
      #5523516 - 11/16/12 09:51 PM

Quote:

Auto-guiding is actually quite simple to do. Also finding guide-star in OAG is easy with calibrated FOV and planetarium software.
What is perhaps much harder is to maintain delicate and large pointing models and tune a complicated open loop system and hope that un-guided works




There is no hoping about it. The proof is in the pudding.

A single 30 minute unguided luminance -35c binned 1x1 900mm FL F/3.6 unprocessed.

Image taken 39 minutes ago. No MLPT, just point and shoot.

Will your mount put this target dead center on every slew and stay there for 30 minutes without moving a pixel?

Incidentally, my current polar alignment error is <=6 arcseconds in RA and <=12 arcseconds in DEC. it's unlikely you can even get your mount that closely polar aligned.

Let's not forget that Autoslew corrected for the polar alignment error, tube flex east and west, collimation error and synch offset and sent corrections to the mount in real time.





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korborh
professor emeritus
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Reged: 01/29/11

Re: ASA DDM85X-SL - Keeps getting better new [Re: SL63 AMG]
      #5523801 - 11/17/12 02:19 AM

I routinely take 30min subs with <2" FHWM stars, 100% yield at 2800mm FL with OAG and AP1200 mount. The mount is 30" Polar aligned RA/DEC and I did not tweak further as it is not necessary.
Plate-solve + sync + slew lands on each target dead on center of chip, only a few pixels off. I don't use modeling - just simple plate-solve + re-slew.
Un-guided may be useful when one wants to take many images per night e.g. supernova survey. Un-guided is also more forgiving with refractors where flexure is minimum. With long FL mirror based scopes, flexure is large and less accurately modeled.
I have not yet seen an un-guided raw image with <2" star FWHM in 30min subs.


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jjongmans
super member


Reged: 02/11/12

Loc: The Netherlands
Re: ASA DDM85X-SL - Keeps getting better new [Re: korborh]
      #5523880 - 11/17/12 06:48 AM

It would be strange if you couldn't accomplish good autoguided results with an AP1200. Same counts for the DDM85.
The reason I don't want to autoguide is because I'm using automation software like CCD AutoPilot and I like to refocus during my subframes. It takes time to reacquire the guidestar and needs time to settle, I don't like that. If you guide with a low min. motion setting, you'll guide on the seeing with lots of unneeded corrections. If you use a high min. motion setting, you'll be too late to correct the error. So with autoguiding you constantly need to adjust the parameters to have optimum guiding, something I don't want to do in an automated setup.
So I think there won't be a big difference in results from an autoguided and unguided setup, it's just another way of working.


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korborh
professor emeritus
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Reged: 01/29/11

Re: ASA DDM85X-SL - Keeps getting better new [Re: jjongmans]
      #5524147 - 11/17/12 10:57 AM

The only autoguide settings I have needed to change (only sometimes) is aggressiveness to match the seeing. One does not need to mess with other settings much at all if the system does not change.

To get the best long exposure data, it is desirable to use closed-loop guided systems and not open loop. Also. I am not sure un-guided using these mounts is any easier than autoguiding.


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: ASA DDM85X-SL - Keeps getting better new [Re: korborh]
      #5524849 - 11/17/12 06:30 PM

I don't really care if I guide or not, it's the result I'm interested. If guiding is not the problem (and so far it never was) I don't see why I wouldn't use guiding with this excellent mount. Problem is I don't have permanent setup and fast polar aligning is required.
Btw, if you look at my images you'll see they are all 30 min subs except one...

Edited by orion69 (11/18/12 09:33 AM)


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