Getting the best performance from my AM5: Page 14

Getting the best performance from my AM5

Kevin_A

w7ay yes, the orange ones are silicone but very thin. I have shock absorbing sorbathane sheet material that is 2.5mm thick and a soft duro 40 that I may try out making donuts from. As far as the cold goes, I don’t work below -10c so my equipment won’t have to endure that either! Haha Some people say that a direct mount to the body is good if the body of the camera is affixed to a heavy scope, others swear by isolating the fan with springs to float it in the housing. It just seems a bit weird that the zwo design is just recently being scrutinized and questions on only the 2600 cameras! I would have thought it would have been an issue a long time ago unless their fan suppliers are shipping out duds due to profit over quality. Quality is getting worse, day by day and I know about light leaks in zwo and bad William Optics flatterners, scopes etc as I have returned a lot of good name brand products over the last 2 years…. Sigma too!

xmj0001

So I've started to jump into this issue. Seems quite intensive from what I've read in most of the forums. But if I understand correctly I should forgo Auto-Calibration in PHD2 in the ASIAIR app as it will get the wrong numbers. I should manually set the Calibration Step for about 1900ms Set Max DEC 150ms Set Max RA 150ms, Guide Scope should be set to .5 sec to 2 sec exposure. Guide Camera to Max Gain Aggressiveness starting at 5% on both working up till i get good RMS values.

Guide Scope: WO 50mm UniGuide 50mm
Guide Camera: ZWO ASI120MM Mini

Kevin_A

xmj0001 based on your guide scope and camera combo calibration steps should be around 1100ms. Let it calibrate on auto. The max durations and aggressiveness settings do not influence calibration, moreso affecting guiding once calibration is complete. Start aggressiveness at 30-40% and see how the lower numbers work first before bumping things up. Max Dec and Rabdurations should start at about 200ms on each but you will need to calculate your PE slope to get accurate numbers. These are just balpark numbers. Guide exposure length will be either 0.5 to 1s and this too will be based on how sharp your PE slope calculates out. Read some of the earlier posts regarding how to calculate guiding parameters based on your mount as others numbers are based on their own PE slopes…. Cheers.

xmj0001

Kevin_A Thank you

Galaxium

w7ay

I took my ZWO provided PE graph and digitized it via WebPlotDigitizer. I took that data and put it in a spreadsheet and calculated the local slope between each row of data. That didn't work out so well but I was able to visually identify the max slop area and choose the points to give me my maximum slope.

I chose these points to calculate my max slope:

(250.92, 6.588)
(251.03, 2.5158)

=> 4.0722 / ( 0.11 * (24 hr * 3600 sec / 360 degrees )
=> 4.0722 / (0.11 * 240)

I am unsure about the 240 as it relates to my AM5. Graph below of a November 2023 mount.

Max Slope (arc-sec / sec) = 0.154

Am I doing this correctly? My guiding results were not great with the ASIAIR+ defaults. I have been testing RA and DEC Aggression percentages. I have found this thread and everything is making more sense. It appears ZWO has made some improvements to the AM5 mounts over time? My graph below for inquiring minds.

I have not read how to properly calculate the "Calibration Step" size. Can someone clear this up for me? Kevin_A

ASIAIR+
William Optics 32mm f/3.75 Guidescope Focal Length 120mm
ASI120MC Mini (I just tossed my ASI 174MM in the garbage which I knew was a mistake but now I know it is confirmed as a mistake)
AM5
Redcat 71
I assume 0.5x sidereal since I haven't changed anything in my ASIAAIR+.

Many thanks to everyone in this thread with special appreciate to Chen. Thank you!

MrAstro

Hi,

Can anyone please take a look to my AM5 PE report and suggest Max Dec., Max Ra., and calibration step ..
Other settings I can tuning during the imaging session I suppose according to environmental factors, Like Exp. time (usually 1-1.5 Sec.) and aggression (usually 50-70 )
May be Chen can do with thanks 🙂 ..
I am using PHD2, ASI290MM Mini and Skywatcher 9x50 finder FL=175mm.
My imaging scale for the guider is 3.42"/pixel
All my imaging sessions are in Bortle 2-3 ( Travelling ).

CS all !

Kevin_A

MrAstro you should be using between 0.5-1.0s long guide exposures. Guide calibration step size will be around 900ms based on your guide scope and 290mm mini camera. Aggressions should always start at the lower range of around 30-40% on each axis. These are good ballpark settings. If you follow some of the previous post you can figure out what your max durations need to be when using either 0.5s or 1.0s guide exposures. You want to bump up the gain on your guide camera so multistar guiding selects at least 10-12 stars. I set mine now at 300 gain in asiair pro.
Your dec and ra max durations should be around 200ms on each using 1s guide exposures but that is just a ballpark but never go higher ever than 750ms on 1s exposures. You need to calculate your slope yourself like we all had to to get the exact correct number for 0.5 or 1s and the duration pulse length in ms. I would start off using 1s guide exposures and if it needs faster corrections use 0.5s. Cheers.

MrAstro

Kevin_A
Hi,

Long time huh!!..🙂
I already calculate it, Its = 0.141"/sec.
So, Could you tell me please what to do with this number? Rather than I search all this long thread 🙂
I am using PHD2. WO scope FL=200, ASI290MM mini.
Thanks

AstroBen60

Hello Folks

As I was waiting for my AM5 to arrive, I spent a lot of time reading all that extraordinary stuff and the links posted here.
I tought I was ready to measure the steepest slopes as soon as I would get it out of the box , and get ready for a perfect setting of phd2 ...

What a surprise I got when watching at my Test Report... !
It doesn't look like others posted here. It 's way more detailled and chaotic.
Looking at the amplitude, it looks like it's actually quite reduced commpared to others posted here. But the curve is'nt smooth at all.

So I wonder why this curve is like this, and how to deal with it.

Is it so detailled because of the relative small Total amplitude , and so the zooming effect on that part of the curve gives like a higher resolution of the measurement ? How to get back to a reasonnably smoother curve that I could work with ?
Is it so rough because that particular mount is just a piece of crap ?
Or finally, did Zwo change it's measurement method, with a higer resolution of measurement ?

Thanks a lot for your help .

Ben

AstroBen60

w7ay

So, I investigated a bit and realized there are two types of mounts here
Some have a 432s period, some 288. (433/1.5)
Mine, shown above, and the one of @xmj0001, show a shorter period than other ones.
But on zwo Website, the Am5 is stated for a 288 seconds period only ( and the am3 also by the way)
Did zwo change the design? Did they change of manufacturer?

By the way, I used webplotdigitizer as advised above, and this is fantastic and easy tool to measure that curve and get relevant data about it.

Thanks a lot if anyone has any information about this main period difference!

Ben

Kevin_A

AstroBen60 yes, they have changed their supplier! It should guide great but definitely looks like you will need fast guiding. Let us know how it works out for you. Mine runs between 0.5 to 0.7 rms everytime no matter if its 0.5-2.0s guide exposures at max durations between 150-350ms. And thats fine for my image scales.

w7ay

AstroBen60 Mine, shown above, and the one of @xmj0001, show a shorter period than other ones.

Yes, ZWO had changed it to a shorter period, ignoring the astrophotography rule of thumb that mounts with longer period are easier to guide (which is mathematically explained using slopes -- the slope of the fundamental of a periodic waveform is inversely proportional to the period). If you have problems guiding, part of your problem is from the shorter period.

Increase your guiding frame rate -- use a 0.5 second guide exposure with a camera that can do 2 FPS, and couple that with a good guide scope to compensate for the short exposure time. Attempt to reduce the guide rate to as low as you can get away with (0.25x sidereal rate will flatten out the guide sawtooth compared with 0.5x sidereal rate). Use a guide camera that gives you a wide FOV since you will need that to get as many stars as possible in multistar guiding, which you will need to reduce "seeing" problems with such short exposure times.

Make sure that the max pulse duration is comfortably shorter than the guide exposure time, otherwise the longer guide pulses will cause the guiding to skip frames.

FWIW, the RST-135 and the NYX-101 (both strain wave geared mounts) have gearings that give 430 second period (sidereal day divided by 200).

Chen

AstroBen60

Kevin_A

Thanks Kevin
Before reading your reply, I just sent an email to zwo, because they have a large FAQ about how to deal with the PE Test Report (it looks like they read that forum before writing it 😁), but state a 432 main period in their examples.
But the specs on the product page do state 288 sec for main period.
So they should confirm as you say they change supplier.

My image scale is 1,94"/pixel, so I thing it will be OK.

I'm still in the process of getting valuables results of my data with webplot and excel.
Actually, we have to take into account the slope in between points, but also the amplitude.
I mean a really steep slope giving 0,5arcsec move, then going the opposite way, even steeper for 0,4arcesc, is not realy a big deal... As long as your resolution is OK.

Ben

Kevin_A

AstroBen60 i am not sure why zwo are not being forthcoming with their spec changes. They seem to do whatever they please without documentation or discussion. My resolution for my biggest scope is 1.2 arcsec so guiding at 0.5 to 0.7 rms is fine for me but guiding has been a big question and challenging as my numbers do not change much going faster and shorter even with increased guide scope gain and better focus etc. I have a flat top graph and a good slope and fair numbers but nothing seems to have much effect and I remain rangebound between 0.4-0.8 no matter what settings. Unfortunately my skies are bad now so testing changes can be erroneous due to smoke in the atmosphere… so i wait. I think Chen said it all….

ASIMount@ZWO

w7ay
Hi Chen,
The reason why the PE curve looks more un-smoothy compared to the older AM5 reports is that we change the smoothness when plotting the curves.
The strain wave gears with 432s period appear to be much same according to the original measurement data as the new ones with 288s period.
That is also one reason for introducing a new strain wave gear.

w7ay

ASIMount@ZWO The reason why the PE curve looks more un-smoothy compared to the older AM5 reports is that we change the smoothness when plotting the curves.

Please show the first derivative of the periodic curve (in arc-sec/second) for the two different gears so people can compare for themselves. That is the pertinent number for autoguiding. The peak-to-peak PE (zero-th derivative) that you show in that piece of paper is only important for unguided operation.

I don't have a dog in this hunt, because I own two RST-135 that use strain wave gears from Harmonic Drives LLC (today guiding about 0.35" total RMS, using the methods I have described). But your potential customers might be interested.

Chen

AstroBen60

w7ay
Am I saying dumb things when I say the peak derivative value has to be filtered before by the time during which it occurs? I mean having a general 0.3asec/" derivative and peaks like 0,8"/sec, but during less than 200ms, does not really matters?

AstroBen60

And by the way, a full access to the whole data that has been measured, via the QR code on the Test Report paper, would be great.
At least, customers who want it could work with that numbers and get what they are looking for, without much work from Zwo. And customers who don't care ... will just don't care again. The data is already gathered by zwo. It is just a matter of giving access to it.

I must say I am quite upset with that.
I would have known that zwo reduced their main period, I would perhaps have considered a Nyx101 or a rst135 instead, or wait for more customers feedback.
In astrophotography, we are in general rigorous guys, many with a scientifici background, fiddling around with arcseconds. This hobby is a high requirement one, and we don't buy things because they are red or blue, but because we investigate a lot before we buy.
As I said, my scale with a FRA400 will be 1.94"/p, with a fsq106 that could one day lie on it wiil be 1.4.. So I will maybe get decent results.
I hope once storms will be gone I would not be disappointed on first nights with it. Or that will definitively keep me away from red...

w7ay

AstroBen60 I mean having a general 0.3asec/" derivative and peaks like 0,8"/sec

Hi Ben,

You would have to set guide parameters (such as guide rate, max pulse duration, etc) based upon the worse of the two (actually worse possible, which is probably not shown in the piece of paper, since it emphasize the peak amplitude [mostly dependent on fundamental] and not the region of worst case slope [highly dependent on the higher harmonics] -- this is why I'd recommend doubling the number that you can see on the piece of paper, to be safe).

The 0.8 arcsec/sec does not bode well (read on further down this post, since you also mentioned a 0.21 arcsec/sec number). The reason is that if you were to use a 1 second guide exposure, a guide star (or stars) would have moved by 0.8 arc seconds within that exposure. You now have to measure the centroid of that small streak instead of the centroid of a fixed star.

Using a 0.5 second guide exposure would reduce that streak to a more acceptable 0.4 arc seconds. I would gently suggest that you try a shorter guide exposure, as long as your guide instrument is up to it. To use 0.5 second exposure, you will definitely need to use multiple-star centroiding (averaging the centroids of multiple stars reduces the variance of the "seeing" error by two for each doubling of stars, if they all have the same weight in centroid computation). You will need a sensor with a large FOV so that it maximizes your chance to see more stars. And you need a larger aperture since you need a larger light bucket.

As an aside, I had for a couple of years been using a Borg 55FL objective as my guide scope (200mm focal length or 250mm f.l. depending on whether the reducer is used; thus f/3.6 or f/4.5) and an ASI178MM as the guide camera that has a decent sized FOV compared to what others typically use as their guide camera. For the past month, I have been experimenting with using a 40mm aperture, 180mm focal length as a guide scope (with same ASI178MM) to see if I can use a camera with a smaller "light bucket," but with a larger FOV to try to find as many guide stars -- that FMA180 appears to work quite well -- ASIAIR could always find 12 stars even in star-starved regions near M81/M82 with a camera gain of 250 (analog gain of 25 dB, which appears excessive, but is fine). So, a smaller and lighter guide instrument that works just as well as my earlier setup. I had to drill some holes in the EAF to mount one on the FMA180(pro), but just a 30 minute exercise (helical focusers are impossible to get pinpoint guide stars without some kind of aid).

Just remember that guide exposures never produce pin-point stars. The star is moving (due to the slope of the PE curve) while exposure is occurring. The best you can do is to focus really well so at least you reduce other centroid measuring errors. This is that "sawtooth" that I keep referring to.

Now, your 0.21 arcsec/sec is much more encouraging, and lines up with what others are seeing with their 430 second periods.

With that kind of slope, you should be able to use short max pulses of around 150 ms even with a guide rate of 0.25x sidereal rate, and a 0.5 second exposure (2 FPS). After discovering that sawtooth graph, it occurred to me that reducing the guide rate will also reduce the sawtooth amplitude (and thus centroid estimation error), so I have been using 0.25x sidereal guiding since. It has been a rather major factor in guiding for me. Whether you can also use a slower guide rate will depend on the worse case slope of the PE curve, and it looks like your mount should be able to handle it (although I think Kevin has reported that ASIAIR cannot choose 0.25x sidereal guide rate with ZWO's own mount; so you may be out of luck there if you use ASIAIR -- try INDIGO Sky instead of ASIAIR if you want to stick with a small microprocessor as your controller).

Good luck.

Chen

AstroBen60

here is my analysis of my test report:

As far as I didn't make any mistake, the max first derivative is 0,21 arcsec/sec, what seems quite good anyway.
But the truth is in the pudding, so let's wait for clear ang long nights to come back.

Ben

AstroBen60

w7ay

Hi Chen

Thanks a lot for your reply

The 0.8arcsec/sec I was talking about was just an example. The max value I have on that tiny part of the whole measurement is 0,21,what lies within the average slope most people have with these mounts (0.17 to 0.35 from what I read ), maybe a little bit on the good side. The only difference I see is that we often see large Max PE amplitude on previous mounts with 432 period, and this one is quite reduced, like the one posted above, also a 288 period one. But as you say, we don't really care as long as we are guiding... And looking at the graph, we can see that for let's say at least 85% of the time, it's under 0.1. Some frames might be devoted to dustbin, but that's not catastrophic neither.

I asked zwo the complete dataset. As it has been measured, it must be stored somewhere. Will they acces to my request...? As you say, a conservative approach would be to double the max value we get from our measurement.

Anyway, IMHO, these mounts are really devoted to travel, easy setup, and short focal lengths. So the resolution of these short FL setups, associated with typical pixel sizes of 3.7u, will be forgiving.
But it's a nonsense to me when I see C11s on it 😳.
As long as you can't take your scope in a bag pack, or cabin luggage, what is the point to have a compact mount to put a huge tube on it? When buying these mounts, we pay for compactness, easy setup, not for accuracy. I have a feeling that, with typical sensor chips, anything above 600/700 mm is not adequate with these harmonic mounts, they are not made for that.

I actually guide with an OagL and a 178mm also. As my focal length is quite short (400mm), I don't really have difficulties to get several guide stars, so I should be able to test your recommendations. ( as soon as the clouds will get away, and the real night will be back..).

And Finally, I don't use ASIAIR. I always put minipc's on my mounts ( mele Q3), because I can't live without NINA. So this shouldn't be an issue to test 0,25x guiding rates.

Thanks a lot for all the extraordinary stuff you posted here, I learned a lot.

Ben

w7ay

AstroBen60 As it has been measured, it must be stored somewhere. Will they acces to my request...?

I agree, Ben. That is what allows the "reference microphones" to be built relatively cheaply nowadays, for example -- their serial number lets you access a per-microphone database for use with compatible software, making the microphone be the equivalent of much more expensive ones.

But it's a nonsense to me when I see C11s on it

Agree 100%. The strain wave geared mounts can swing very heavy payloads like a rag doll. But I am not sure if they can guide heavy payloads with long focal lengths well enough. The heaviest payload I have on mine is an FSQ-85. I will be testing the RST-135 with a Mewlon 180C when it is scheduled to arrive this Autumn -- if it struggles, I would need to go to a RST-300, since the Pryxis NYX-101 (who also never built a mount before) has problems of its own. But forget travelling with an RST-300.

I always put minipc's on my mounts ( mele Q3), because I can't live without NINA.

Hah, I have been writing my own software to use INDIGO on macOS. The latest fun exercise is to construct a new All-Sky Camera. My earlier camera had use a discarded first gen ASIAIR on WiFi, with a color ASI178 and a CCTV lens. The new camera uses a Raspberry Pi 4 running INDIGO Sky, Ethernet PoE for a single wire connection, an uncooled ASI294MC, and a Samyang E-mount 8mm fisheye lens. I am especially happy with ditching the ASIAIR, which is severely limited in what it can do.

Chen

Kevin_A

w7ay just a quick question for you Chen… is there a reason you guide with a 178 vs the standard 174 guide cam? Just bigger sensor or usb3 or ? I am thinking of getting a Askar 180pro and maybe a new guide cam with bigger sensor.

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