Getting the best performance from my AM5: Page 27

Getting the best performance from my AM5

johncdavis200

w7ay The AM5 was all my budget could afford ... sorry to botther you.

mountainair

Believe it or not, I have read all 505 replies to this thread -- and am blown away at the usefulness of the information here. An all-inclusive summary should be written and "pinned" to the top of the thread if possible.

At any rate, I have two questions for my ASIAir & AM5 mount which I have yet to use due to weather:

1) What would be better -- a more-sensitive 50/200mm f/4 (WO Uniguide 50) or a SkyWatcher EvoGuide 50ED APO with a field flattener, but at a higher f/4.8? I heard what Chen said about misshapen stars contributing to multi-star guiding error. The EvoGuide + Flattener is almost $400 with tax, otherwise I wouldn't bother you with this question :-).

2) The camera would likely be an ASI290MM (the USB3 planetary version), but I am unsure. I am enticed to try near-IR guiding with the ASI220MM Mini, but I hesitate at its USB 2 interface, the large pixels, and the fact that it's not appreciably cheaper despite the non-Sony sensor. I'm also concerned about it being able to reliably meet the 2 fps rule un-binned (though the specs claim 14fps, maybe I shouldn't worry). The QHY678 is out, since I plan this to be an uber-portable rig with ASIAir, and there is no mono ASI678MM (what a dream that would be). The ASI178MM might be a good compromise, and it's 14-bit. Any guidance between the three?

Thanks in advance, and happy holidays!

Kevin_A

mountainair the better star shape of the Skywatcher scope will be best as you can compensate for the slower glass f ratio by increasing the camera gain. I use both the 220 and 290mm mini cameras ( not the non mini version) and the 290 mini is not for sale anymore which is a shame. I think the sensors are fairly equal respectively but the smaller pixels on the 290 were slightly advantageous in my opinion. The 220 has been working fine for me and i like that the noise is very low past the HGC set point. I also looked at the Askar FMA180 Pro as an option too.

mountainair

I think I bought a lemon, and I wonder if I should send this back (unopened, I only removed the chart). In looking through all these PE charts posted here, I don't think I've seen one with messier harmonics. It looks like they ran this bench test during an EARTHQUAKE!

I'm not sure that I did this right:

This is a new AM5, with the 288 second period. So, I measured 27.82 screen units (blue line) across the 4 peaks and divided by 4 to get a more accurate distance for the period on the X axis: 6.955 (41.41 seconds per screen unit).

I then found what I think is the steepest slope (at least in this partial view) and measured it to have a horizontal component of .92.

.92*288/6.955 = 38.096 seconds

ZWO stated the mount has a MAX PE of 11.4, but I see 11.8 on the chart. So:

11.8 arc-sec/38.096 sec = .3098 arc-sec/sec

That's at the lower end of the quality continuum, and I wonder if .5s exposures and a .25x guide rate can tame those harmonics.

Kevin_A

mountainair most of the newer 288s period mount graphs look gnarly and jagged. The only way to verify is to test it out and keep the aggressions between 35-50% and if you are using 0.25X guide rate then keep the max durations at about 300-450ms. This will be a good starting point. The 290mm mini should allow 2 frames per second and keep the guide camera gain up near 175.

mountainair

Thanks Kevin.

For comparison, here's the chart from my friend's AM5 running the same 288s periods:

Noticeably smoother.

Kevin_A

mountainair that is an anomaly and a very good partial… but, but, but…. It is only a partial and for a true periodic error report you need to see 720 degrees of contact period and it is still only on Ra, no info on Dec gears as well. My suggestion would be to run it at my suggestions on a night of non turbulent atmosphere to get a judgement of how it looks. Look at my curve… looks worse.

Gagan

Hello everyone,

I have just got my first harmonic mount (AM5) delivered, and I am trying to workout the guide settings, and evaluate if I actually got lucky with this mount or if is going to give me a hard time.

I have tried to draw the slopes, but I am not sure if I am doing it correctly, moreover I don’t know what to do next after drawing the slopes, how do I calculate the data needed ?

Once I have the settings for my mount, hoping that it will guide well, will these setting be valid for all telescope and guidescopes I use or will I have to calculate the parameters for every single setup ?

Thanks

Gagan

w7ay

Gagan I have tried to draw the slopes, but I am not sure if I am doing it correctly

Chen

Gagan

w7ay

Thanks for the help Chen !
I am pretty lost, but from what I understand the steeper the slope the worse / harder to guide is the mount.

Am I understanding it correctly ?

Thank you

Gagan

w7ay

Gagan from what I understand the steeper the slope the worse / harder to guide is the mount.

Correct.

This is why I'd warned people that what they are seeing is not the whole truth, just a segment that ZWO wants to show you. There are other hour angles where the slope could turn terrible; like with your mount for that particular part (few minutes) of the sky.

Chen

Gagan

w7ay

I have tried to follow some posts here to calculate the slope.

The result seems to be: 0.219729 arcsec/sec For the slope you suggested Chen.

Have I received a bad mount ?

I attach my math and graph, I used paint on windows as suggested by another user, not sure if is ideal, but I don’t know how to use a better method at the moment.

Thanks,

Gagan

Jan75

Can anybody explain why in one graph is 172.8 seconds from Peak to bottom, and the other one 216 seconds, while the displacement on the X axis has a 0.6 degrees intervals in both ?

Thanks

Gagan

Gagan
Disregard, I just understood it all.

I will try to calculate and post the results.

mountainair

Gagan, I believe you have a keeper.

I am by no means an expert, but having done this quite a few times on my own mount, I plugged in my own quickly-measured numbers for your chart (assuming you have a 288s mount, which seems to be the case) and came up with .22"/s. This can be guided out using Chen's advice above, especially since you have fairly smooth curves in your chart. The one slope is pretty steep compared to the others, so you may need a bit larger of a max pulse limit than the general guidance here, but I think you'll enjoy it. Happy Holidays.

Gagan

mountainair

mountainair
Hey 👋🏻
I do hope so, because I am selling a AZ-EQ6 and bought the AM5.
I was happy with the AZ-EQ6 Performance but not with the weight.
Having to drive 1 hour one way to a dark sky location and setup a big mount it’s starting to take a toll.

I hope I can get the same guiding performance with the AM5, with the biggest scope I currently have which is the Esprit 120 refractor.

MarcK

Hello everyone
Thank you for this great thread.

I have been working with the AM5 for a few months now and use the default settings 2000ms / 2000ms / 2000ms / 2sec for guiding. So I am usually between 0.4 and 0.8 Tot.
Until now I always thought I should just be happy with these values. But if I can improve my guiding, I would of course be happy to test.

To be honest, I don't really understand the math with the graphics.

If anyone can help me I would be very happy

Can we now say in general as starting point to play around 0.5x sidereal rate, 0.5sec guide exposure, 1900 ms Calibration Step, max RA/DEC numbers to around 150-350ms and aggression on both RA and DEC to 25-45%.

Thanks
Marc

Kevin_A

MarcK calibration step size is determined by your guide scope focal length and guide camera pixel size only and will change depending on those factors and not the mount. All the other settings are good as a base setting too, but I would first try 1.0s guide exposures before trying 0.5s as you will get better guide star signal. If 0.5 runs better so be it but you may require bumping up the guide camera gain a bit to improve star signal. Cheers!

MarcK

Kevin_A
Hello Kevin
Thanks for your reply.

I am using the ZWO Mini Guider Scope 120mm and ASI120MM camera. So 1900ms calibration step should be ok?

I will try first 1sec exposure time around gain 48.

Since I am still working with my Nikon full frame I do strong dithering 30px. But that should have nothing to do with improving the guiding settings.

Kevin_A

MarcK yes, 1900 or 2000 is perfect for that combo. I have the same combo and use gain 68… just a bit higher as I am in dark skies. I get even better guiding on my 160mm and 240mm guide scopes as they have bigger apertures. Your imaging camera has no effect either. I use 2600, 533, 183 cooled cameras plus Nikon Z6 and Z7 as well. I only dither 5-10 pixels and never any walking noise with my Nikons.

MarcK

Kevin_A
Yes of course I always play around with the gain. It always depends on where I am. Here in Switzerland in the mountains, we have some places with very dark skies. Sometimes I need gain 80.

I deliberately opt for a strong dithering of 30px. I only see advantages here. I have to cut the picture a little anyway, although the RedCat 51 and 71 deliver very well.

You have already gained a lot of experience in this thread what do you think about the diagram of my AM5. Mine was produced at the beginning of this year and if you compare it with last year's models, it doesn't look so smooth to me.

Kevin_A

MarcK your partial graph only represents a small portion of the complete period length at the highest PE area and not the full period. So it is bascally useless in reality to a point. However, based on that partial portion you would probably benefit from 0.5s guiding due to the many smaller fluctuations. Looking at the complete period I would bet that the whole period length is similar and rapid small corrections will do well to correct it. The roughness is typical of all 288s period mounts from zwo these days.
Looks ok to me, scary shape as usual but typical.

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