PHD Guiding 2 and AP900


Chanan Greenberg
 

Hi,

I have been using an old (circa 90's) AP900 with an AP5" Starfire which is working great with PHD guiding with very decent results. Looking to improve.
I have two questions:
1. When I setup a new profile on PHD it asked if my mount has high precision encoders - I did not know what to do so left it unchecked. Does the AP900 have high precision encoders?
2. I have been using the default RA algorithm which is Hysteresis, but read somewhere that other algorithms may perform better such as Lowpass and Lowpass2 - any recommendations?

Thanks
Chanan


ccd astro
 

Hi,
I have an AP 900 from 2006 and it works great. It does not have encoders. 
My mount works best with the Hysteresis algorithm for RA and Resist Switch in declination. I use guide intervals around 3 seconds. On good nights, the rms error is < 0.5". 
It is worth experimenting with the algorithms, a good exercise for full moon nights. 
- Tom C

On Sun, Nov 27, 2022 at 11:47 AM Chanan Greenberg <chanan2009@...> wrote:
Hi,

I have been using an old (circa 90's) AP900 with an AP5" Starfire which is working great with PHD guiding with very decent results. Looking to improve.
I have two questions:
1. When I setup a new profile on PHD it asked if my mount has high precision encoders - I did not know what to do so left it unchecked. Does the AP900 have high precision encoders?
2. I have been using the default RA algorithm which is Hysteresis, but read somewhere that other algorithms may perform better such as Lowpass and Lowpass2 - any recommendations?

Thanks
Chanan


Dale Ghent
 

The 900GTO never had an encoder option. An encoder option came with its replacement, the 1100GTO.

Which algorithm you choose is based upon how your mount performs; not necessarily who made it. With your late-90's mount, maintenance is going to be a factor in how it performs today, even for a high-quality example. Has it been regreased and how fresh is its PEC? What are your guiding stats under your current PHD2 configuration?

On Nov 27, 2022, at 14:47, Chanan Greenberg <chanan2009@...> wrote:

Hi,

I have been using an old (circa 90's) AP900 with an AP5" Starfire which is working great with PHD guiding with very decent results. Looking to improve.
I have two questions:
1. When I setup a new profile on PHD it asked if my mount has high precision encoders - I did not know what to do so left it unchecked. Does the AP900 have high precision encoders?
2. I have been using the default RA algorithm which is Hysteresis, but read somewhere that other algorithms may perform better such as Lowpass and Lowpass2 - any recommendations?

Thanks
Chanan


Chris White
 

I'm not sure about the evolution of the 900, but I know that the late models had motor encoders.  Different than absolute encoders.  I'm not sure which type of encoder PHD is asking about, I imagine AE... .

I had a 2009 900GTO and I guided using hystersis.  With a fresh curve and APCC model it performed brilliantly.  I generally guided in the 0.3" RMS error and always had tight round stars.  I dont have it anymore, but I do remember tinkering with PHD trying everything out.  Hystersis set to 0 with exposures in the 2 to 5 second range seemed to give me the best performance.  To be honest, I should have tried it unguided but I never did. 


Chanan Greenberg
 

Hi Dale,

The mount seems to be performing well overall. I am not the first owner so I have no idea when it was last greased, I have had it for 3 years and have not done anything to it. I have not been using PEC at all, from my experience I find PHD seems to be having a harder time with PEC is turned on (at least using Hysteresis algorithm). 

Below you can see a sample guiding session.

Overall peak corrections are around 5", RMS total is at 1". My polar alignment error is 0.2' (12" off the refracted pole) so should be close enough for guiding to overcome that.




Chanan Greenberg
 

I had this mount under a different configuration with a C-9.25 and did 2-3 nights of drift alignment, that config could go for 15 minutes unguided with perfect round stars. This is why I know this mount is great and I am looking to tinker with PHD


ROBERT WYNNE
 

If it indeed had high precision encoders it would likely be worth more than the Starfire and mount together - and then some. I don't think high precision encoders were an option at that time and were only used on ultra high precision medical equipment such as CAT scanners and Black project satellites. But I defer to A-P for clarification. -Best, Robert

On 11/27/2022 11:47 AM Chanan Greenberg <chanan2009@...> wrote:


Hi,

I have been using an old (circa 90's) AP900 with an AP5" Starfire which is working great with PHD guiding with very decent results. Looking to improve.
I have two questions:
1. When I setup a new profile on PHD it asked if my mount has high precision encoders - I did not know what to do so left it unchecked. Does the AP900 have high precision encoders?
2. I have been using the default RA algorithm which is Hysteresis, but read somewhere that other algorithms may perform better such as Lowpass and Lowpass2 - any recommendations?

Thanks
Chanan


Brian McFarland
 

That early mount probably has incremental encoders intended for digital setting circles - not the sort of absolute encoders that were supplied on later mounts and not the type of encoders you would use for autoguiding.  My guess is standard 10K incremental encoders. So when PHD asks if you have high precision encoders, the answer is no.

I'm basing all this on my own experience with a circa-90s AP 1200.

Hope that helps!

Brian


Dale Ghent
 

Things being worse with PEC on is kind of expected on an aged mount - it means that the curve that the controller is programmed with is no longer effective which can make things worse. It can lose its effectivness for a variety of singular or combination of reasons - the gears have worn and the programmed curve no longer applies to the current reality, the worm gear and wheel have had their teeth remeshed, there grease has hardened and accumulated bits of gunk that get in the way. To correct this, you need to update the curve using a tool such as PEMPro.

If the mount is 2nd hand and hasn't been regreased since you've owned it, and the last regreasing date is unknown, it's probably best to just go ahead and do it. You can get regreasing instructions and a grease kit from A-P. Ordering the kit is something you'll need to do over the phone as it's not listed on the online store. It's cheap. It takes a weekend to do if you're thorough about cleaning out the old grease. It's a good "aw nuts I have 2 more weeks of bad weather" project. When done and put back together, do a new calibration run in PHD2 and a new PEC when the time and inclination are available. Leave PEM off until you make a new curve.

You should see better than 1" performance on a balanced mount load, modulo wind, seeing, and polar alignment factors. It's hard to tell from the resized screenshot, but it does look like there is some rhythm to the RA corrections, so a regreasing and new PEC may be in order.

On Nov 27, 2022, at 18:12, Chanan Greenberg <chanan2009@...> wrote:

Hi Dale,

The mount seems to be performing well overall. I am not the first owner so I have no idea when it was last greased, I have had it for 3 years and have not done anything to it. I have not been using PEC at all, from my experience I find PHD seems to be having a harder time with PEC is turned on (at least using Hysteresis algorithm).

Below you can see a sample guiding session.

Overall peak corrections are around 5", RMS total is at 1". My polar alignment error is 0.2' (12" off the refracted pole) so should be close enough for guiding to overcome that.



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Paul Nelson
 

I can't speak specifically to how PHD2 works with A-P mounts as I have not been able to use it with mine yet. I have an AP900HDA (1995) that needs an adapter to connect an RJ12 connector to the hand controller, and my first attempt was an utter failure. With assistance from A-P personnel, I believe that I have the issues resolved, but haven't been able to try it out yet. Mine does have encoders, but as mentioned in another response, they are for using with Digital Setting Circles to assist in locating targets  (in my case using PushTo since my mount has no GoTo capabilities) and I would agree that the answer is no on encoders.

I would suggest trying the PPEC (Predictive PEC) algorithm in PHD2. It would help to know the worm cycle, but it can figure it out, if need be. When you first start guiding with this algorithm, it acts like Hysteresis, but over the first couple worm cycles it "learns" any regularly occurring error and predictively adjusts for it. It allows you to specify both a predictive response and a reactive response to detected errors. This has worked the best with my iOptron mounts, and will be my go-to algorithm when I try it with my AP900HDA. With my other mounts I have typically used a Predictive setting of 60 and a Reactive setting of 50 so it doesn't slam it back too quickly and overshoot, but you might need different settings for your mount. This should smooth out any periodic error in your worm somewhat. With my iOptron mounts (CEM40 and CEM60) I typically get 0.5" to 0.7" total RMS error, when things are adjusted right, and sometimes as low as 0.4" with good Seeing, and would expect that with a quality mount like your AP900 you should be able to meet or exceed those numbers. I would also recommend turning on Multi-star Guiding if you haven't done so already. I have found with my mounts that a mesh that is too tight ("stiction") can be as bad as one that has too much backlash as it resists the change, so adjusting the mesh might be wise, as well as re-greasing it, which I need to do with mine.

Paul


Dale Ghent
 

PHD2's PPEC is objectively unnecessary with an A-P GTO mount that has a current PEC programmed into it. Your HDA model must use PHD2's PPEC feature to attain similar effect as an in-mount PEC due to its inability to store a curve in its controller. With GTOs, a PEC programmed into it is active whether you're using PHD2 or not.

On Nov 28, 2022, at 13:48, Paul Nelson via groups.io <creatorshandphoto@...> wrote:

I can't speak specifically to how PHD2 works with A-P mounts as I have not been able to use it with mine yet. I have an AP900HDA (1995) that needs an adapter to connect an RJ12 connector to the hand controller, and my first attempt was an utter failure. With assistance from A-P personnel, I believe that I have the issues resolved, but haven't been able to try it out yet. Mine does have encoders, but as mentioned in another response, they are for using with Digital Setting Circles to assist in locating targets (in my case using PushTo since my mount has no GoTo capabilities) and I would agree that the answer is no on encoders.

I would suggest trying the PPEC (Predictive PEC) algorithm in PHD2. It would help to know the worm cycle, but it can figure it out, if need be. When you first start guiding with this algorithm, it acts like Hysteresis, but over the first couple worm cycles it "learns" any regularly occurring error and predictively adjusts for it. It allows you to specify both a predictive response and a reactive response to detected errors. This has worked the best with my iOptron mounts, and will be my go-to algorithm when I try it with my AP900HDA. With my other mounts I have typically used a Predictive setting of 60 and a Reactive setting of 50 so it doesn't slam it back too quickly and overshoot, but you might need different settings for your mount. This should smooth out any periodic error in your worm somewhat. With my iOptron mounts (CEM40 and CEM60) I typically get 0.5" to 0.7" total RMS error, when things are adjusted right, and sometimes as low as 0.4" with good Seeing, and would expect that with a quality mount like your AP900 you should be able to meet or exceed those numbers. I would also recommend turning on Multi-star Guiding if you haven't done so already. I have found with my mounts that a mesh that is too tight ("stiction") can be as bad as one that has too much backlash as it resists the change, so adjusting the mesh might be wise, as well as re-greasing it, which I need to do with mine.

Paul


 

>>>PHD2's PPEC is objectively unnecessary with an A-P GTO mount that has a current PEC programmed into it.

I agree in general, but PPEC can still be used in conjunction with a mount that has PEC programmed into it to address residual periodic error

They are very complementary even if you have a low periodic error mount

On the flip side, PPEC algorithm should definitely not be used with an absolute encoder mount

On Mon, Nov 28, 2022 at 12:34 PM Dale Ghent <daleg@...> wrote:
PHD2's PPEC is objectively unnecessary with an A-P GTO mount that has a current PEC programmed into it. Your HDA model must use PHD2's PPEC feature to attain similar effect as an in-mount PEC due to its inability to store a curve in its controller. With GTOs, a PEC programmed into it is active whether you're using PHD2 or not.

> On Nov 28, 2022, at 13:48, Paul Nelson via groups.io <creatorshandphoto=yahoo.com@groups.io> wrote:
>
> I can't speak specifically to how PHD2 works with A-P mounts as I have not been able to use it with mine yet. I have an AP900HDA (1995) that needs an adapter to connect an RJ12 connector to the hand controller, and my first attempt was an utter failure. With assistance from A-P personnel, I believe that I have the issues resolved, but haven't been able to try it out yet. Mine does have encoders, but as mentioned in another response, they are for using with Digital Setting Circles to assist in locating targets  (in my case using PushTo since my mount has no GoTo capabilities) and I would agree that the answer is no on encoders.
>
> I would suggest trying the PPEC (Predictive PEC) algorithm in PHD2. It would help to know the worm cycle, but it can figure it out, if need be. When you first start guiding with this algorithm, it acts like Hysteresis, but over the first couple worm cycles it "learns" any regularly occurring error and predictively adjusts for it. It allows you to specify both a predictive response and a reactive response to detected errors. This has worked the best with my iOptron mounts, and will be my go-to algorithm when I try it with my AP900HDA. With my other mounts I have typically used a Predictive setting of 60 and a Reactive setting of 50 so it doesn't slam it back too quickly and overshoot, but you might need different settings for your mount. This should smooth out any periodic error in your worm somewhat. With my iOptron mounts (CEM40 and CEM60) I typically get 0.5" to 0.7" total RMS error, when things are adjusted right, and sometimes as low as 0.4" with good Seeing, and would expect that with a quality mount like your AP900 you should be able to meet or exceed those numbers. I would also recommend turning on Multi-star Guiding if you haven't done so already. I have found with my mounts that a mesh that is too tight ("stiction") can be as bad as one that has too much backlash as it resists the change, so adjusting the mesh might be wise, as well as re-greasing it, which I need to do with mine.
>
> Paul
>









Chris White
 

I used PPEC extensively with CEM mounts and it worked brilliantly. However with my GTO it performed notoceably worse than hysteresis. 

Just one data point in this convo...