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The ZWO AM5 landed!


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Posted (edited)

Proper First Light for the camera, scope, AM5 and Me!

As the weather's been so decent recently I felt compelled to get out and image, despite the late finish :smile:. I chose M13 as it would provide a decent contrast against the light summer sky, and was conveniently situated. This is the first time I've imaged since the Spring of 2020, so essentially all the gear was new to me. I have to say it took a good long while to get imaging, largely due to unfamiliarity, but got there in the end. At least it's the first time I've started off in shorts and T-shirt (not a pretty sight :smile:)!

I did have trouble using the PA routine, sometimes the circle would move with adjustment, and at other times seemed quite oblivious to my inputs. And of course, the ASIAir won't let you go any further until you get the smiley face, so no option but to continue :huh2:. It could all be down to operator error, so I shall need to investigate further. I have to say that the iPolar is a cinch in comparison, but then I was using a different mount and not the imaging camera. We'll see.

This was the set-up.

  • ZWO AM5
  • ASKAR FRA400 f/5.6, at native FL.
  • ASI533MC camera
  • Astronomik L2 UV/IR filter
  • William Optics 50mm/200mm Uniguide
  • ASI120MM guide camera
  • ASIAIR Plus

I took 60x60s lights, gain 100 at -10°C (at 80+% power, it was a warm evening!), 30x previously recorded darks, 60x flats (0.2s), and 60x Flat/darks (0.2s). Guiding was multi-star at 0.5s. For this exercise, dither was off.

I haven't processed the image yet, but really that is secondary to how the mount performed, and will post later, though once done I shall be able to assess the star shapes and sizes. Here are a couple of guide plots from the evening.

Screenshot_2022-07-09-23-28-26-563.thumb.jpeg.59b940f75b47caae6f53381ca4abcdff.jpeg

Screenshot_2022-07-10-00-08-38-265.thumb.jpeg.14e6e3aaa8a23a7045f1a3ebd4ec99cc.jpeg

Here's a single full-frame sub. Centering was bang on.

Light_M13_60.0s_Bin1_gain100_20220710-000225_-10.0C_0035.thumb.jpg.0a99fcf407093af7baf47bb4c234aace.jpg

I'm certainly not complaining about these results :biggrin:. I hope this has been useful.

Ian

Postscript. Interrogating the guide log using PHD log viewer, I get an rms of 0.38" RA and 0.5" DEC for the whole shoot. PA error is given as 29.6', so that needs to be improved.

Edited by The Admiral
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Thanks for posting this 👍🏻a lot of people will be very interested 🙂

Can you try guide exposures a bit longer next time, just to see the effect it has, I know the conventional wisdom on these is 0.5 second but would really like to see if 1 or 1.5 seconds smooths the corrections out

Cheers 

 

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Posted (edited)
3 hours ago, knobby said:

Thanks for posting this

Not a problem, I'm interested myself.

3 hours ago, knobby said:

Can you try guide exposures a bit longer next time, just to see the effect it has, I know the conventional wisdom on these is 0.5 second but would really like to see if 1 or 1.5 seconds smooths the corrections out

That is my intention when we get back to more sociable imaging hours ;).

I think there are a few things worth remembering. This endeavour had reasonably good seeing I believe, but it's when the seeing gets rough that problems could arise I think. In fact there is a new thread on the Facebook ZWO mount site which refers to the issues of the more transient behaviour of the harmonic drive, rather than the overall PE. [Note. I'm not a member of Facebook, nor intend to be, but I have been able to read their pages using my Android tablet. The text isn't obscured by the flag telling me to sign in, as there is with Microsoft.] There is mention of this document relating to the Rainbow mount, https://www.firstlightoptics.com/user/products/large/Supplementary Manual V16.pdf, where on page 16 the author notes that some units may display transient tracking error rates which change by up to 0.7 arc.sec/sec. This is a characteristic of harmonic drives apparently, and so would be common to all such mounts (without encoders?). As you can see from the PE trace for my mount, the curve has some definitely sharp kinks, and I guess this is where the guiding could fail, and where a 0.5s exposure comes from. That said, there are owners of the Rainbow astro on this site and appear to be pleased with their mounts.

Interestingly, I have seen reference to a 9" SCT (with reducer) being carried by an AM5, and apparently with guiding of 2 seconds. Can't quite see how that works, but there you are.

I'm certainly no expert on guiding, so I'm open to any correction here. Naively, I can imagine that should the guiding not keep up with a transient, it will catch up further down the line when rates of change are more reasonable, just so long as the mount hasn't moved too far on, and the overall tracking error remains acceptable. Since I was imaging for at least 8 PE cycles, it does seem that under my imaging conditions, given that all subs looked fine, these transients caused no issue with 0.5s guiding, and with the mount lightly loaded.

Of course, I don't know where those 8 cycles sit in the whole 24 hour PE period, and how similar they are over all cycles.

A lot of unknowns to be sure, but that doesn't indicate that the mount is not up to the job!

Ian

Edited by The Admiral
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Posted (edited)

This is the end product: https://stargazerslounge.com/topic/397076-m13/. It was processed in APP and the FWHM was consistently between 2.3 and 2.5. Presumably they are pixels, so this is equivalent to about 1.94*2.4=4.7 arcsec, where 1.94 is the resolution in arc.sec/px. I can't help thinking this is a fairly naive calculation though ;).

Ian

Edited by The Admiral
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8 hours ago, The Admiral said:

This is the end product: https://stargazerslounge.com/topic/397076-m13/. It was processed in APP and the FWHM was consistently between 2.3 and 2.5. Presumably they are pixels, so this is equivalent to about 1.94*2.4=4.7 arcsec, where 1.94 is the resolution in arc.sec/px. I can't help thinking this is a fairly naive calculation though ;).

Ian

To my eye the star shapes look pretty good. I’d be pleased with that, but then I’m not very critical. I know som people are never happy however round their stars look.  Is this FWHM typical of what you normally see with this scope and camera? 

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33 minutes ago, Ouroboros said:

Is this FWHM typical of what you normally see with this scope and camera? 

Thanks for your comment.

This is first light for scope, camera and mount! So I can't really say. I think that the seeing was particularly good that night too.

Ian

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Yesterday I spotted this on the tripod.

P1030771.jpg.bfe9a6607d52475f0507a1e57423cb0c.jpg

I had assumed that the locking knob on the tripod was just a simple screw arrangement, but I was impressed to see this design. Obviously they'd given some thought to making a non-marring design.

Ian

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Posted (edited)

I've just read a review by Simon Lewis in New Zealand, and one of the beta testers. He's obviously very positive about the mount, but worth a read.

https://www.amateurastrophotography.com/zwo-am5-harmonic-mount-review?fbclid=IwAR281QD1y7gidltcH9Z8SracANGwljnhQOTNhXyKtdAAuBuLXZbjn_ZDpV4

To be honest, I'm feeling very positive about it too and it is such a pleasure to use when coupled with an ASIAir.

Ian

Edited by The Admiral
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  • 5 weeks later...
Posted (edited)

I thought I'd update my thread on the latest adventure with this mount. Given the late nights called for when imaging at this time of year, I can't summon the energy very often :lol:.

Last Saturday (6th Aug) I imaged IC 5070, the Pelican Nebula, in straight colour. I've been having trouble doing the PA on both my imaging runs (which I'll describe elsewhere), but I managed to get 9.1' PA Error, overall RA guide errors of 0.39"rms, Dec error of  0.4"rms, and combined 0.56"rms, according to PHD2 log viewer, with a 0.5s guide exposure.

I've posted the result here.

Yesterday I got the kit set up and intend to image IC5070 with an L-Extreme wilter (ha-ha, that typo spells out more like I feel in this heat) filter, my first entry into NB. I shall have to see how that turns out.

Ian

Edited by The Admiral
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Your pelican image looks great Ian! Your guiding is also really good, both RA and Dec have the same RMS values too. I bet your back is thanking you for not hoisting out heavy equipment each night. 

Are you letting it run through to the early morning whilst you sleep, or are you staying awake and bringing it back in when you've had enough? 

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Thanks Richard. Dead right, my back is thanking me, and to be honest, I just wouldn't have bothered getting the heavy gear out, even if I was able to. Using this gear with the ASIAir just makes life so much easier too. Tempting though it may be, I shall probably bring the gear back in in the early hours. I'm not that brave yet :). I've already got a Pelican Nebula taken through a L-Extreme from last night, and tonight I'm having a go at the Elephant's Trunk Nebula with the Extreme too. Where I do my processing is too hot to be comfortable so that'll have to wait a bit. All of these could do with more imaging time, but currently I'm just relishing the opportunity. I can always add more subs later.

Ian

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Excellent stuff! Yeah the confidence to leave it run unsupervised will come in time 😊 The elephants trunk is a nice target, will be looking forward to seeing your final image when you get around to processing it. I think you're doing the right thing by trying out a couple of different targets, there's nothing worse than putting all your eggs into one basket and it doesn't really work out (eg wrong framing). As you say, you can always add subs later on! 

I know the feeling about not getting to process, this is my fourth sequential night of imaging and I haven't processed any of the images. I've only blinked through them in pixinsight each morning to check they're all good and that I don't need to tweak anything for the following night. Never mind, clouds and rain are due Saturday for me so it'll be business as usual, giving my time to process my images. 

Good luck for tonight, hope it goes well. 

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  • 2 weeks later...

Although it's cooled down now, I've had no time to progress further before now. So for anyone who's still interested in this thread, I've just processed IC1396. My firsts attempt at dual band imaging with the L-Extreme filter, and I've clearly got much to learn, besides which it needs a lot more integration. However the results are not the purpose of this thread so much, and the image is posted elsewhere (https://stargazerslounge.com/topic/398677-ic1396-elephants-trunk-in-hoo-false-colour-my-first-dual-band-image/).

For this imaging sequence I achieved an overall guiding level of 0.31" rms RA, 0.32" rms Dec, to give an overall rms figure of 0.44", which I'm pleased with. PA was 5.2'. The guide log is attached.

PHD2_GuideLog_2022-08-11_215834.txt

Ian

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Abnormally good seeing for this area last night, gave me a chance to check on the guiding issues I’d had last week. In short, no issues at all, the rms was pretty much the same as yours Ian at 0.41 for a 150minute session on IC59. Iike you I’d have loved to have left it running and gone to bed but I’m not that brave yet! 
Also did a check on what happens if guiding is turned off, surprisingly I still had round stars at 2 minutes and no issues with resuming guiding. I’m imaging at 432mm though and I guess much longer and I’d see effects.

Edited by Martthebass
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12 minutes ago, Martthebass said:

Abnormally good seeing for this area last night, gave me a chance to check on the guiding issues I’d had last week. In short, no issues at all, the rms was pretty much the same as yours Ian at 0.41 for a 150minute session on IC59. Iike you I’d have loved to have left it running and gone to bed but I’m not that brave yet! 
Also did a check on what happens if guiding is turned off, surprisingly I still had round stars at 2 minutes and no issues with resuming guiding. I’m imaging at 432mm though and I guess much longer and I’d see effects.

Sounds all good 🙂. Presumably, resumption of guiding was automatic? It would be very helpful if somehow we could know where in the PE cycle the mount is, as I would imagine that the response to failure of guiding would be very much influenced by the presence of "irregularities" in the shape of the PE curve. One day I might centre the image on a bright star and then let the mount track without guiding, with frequent subs. It should be possible to recreate the PE curve by checking the deviation from the centre position.

Ian

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1 hour ago, The Admiral said:

Sounds all good 🙂. Presumably, resumption of guiding was automatic? It would be very helpful if somehow we could know where in the PE cycle the mount is, as I would imagine that the response to failure of guiding would be very much influenced by the presence of "irregularities" in the shape of the PE curve. One day I might centre the image on a bright star and then let the mount track without guiding, with frequent subs. It should be possible to recreate the PE curve by checking the deviation from the centre position.

Ian

No I just turned off guiding and ran a few subs through on 120s and then turned guiding back on. Fortunately the stars were still pretty centred but it did choose a new main star. 

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9 hours ago, The Admiral said:

Does that mean that you are single star guiding, not multi-star?

Ian

No I’m multistar but I’ve never figured why the crosshairs sit on one and show it’s size/brightness.

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4 hours ago, Martthebass said:

No I’m multistar but I’ve never figured why the crosshairs sit on one and show it’s size/brightness.

Me neither! As guiding is based on PHD2, then time to turn to the PHD2 manual. I think this para explains it.

"Some guiding configurations can benefit from guiding on multiple stars rather than just one. This results in using a weighted average centroid
position of multiple stars rather than just the centroid of a single star. Multi-star guiding is enabled using a check-box on the Guiding Tab of the
Advanced Settings dialog. When this option is enabled, the Auto-select function will identify up to 12 stars in the field of view that have adequate
SNR. No more than 9 of these will be used at any one time, but the remainder will be used to replace secondary stars that are lost or rejected for
some reason. The "primary" star is the single best candidate, the same one that will be selected if multi-star guiding is disabled. As guiding
proceeds, some of the secondary stars may be rejected because they are too dim or have drifted outside the field of view. This is of no concern,
the multi-star guiding algorithm handles the secondary list automatically. When multi-star guiding is active, the PHD2 image display will show the
usual rectangle around the primary star and circles around the secondary stars. All other UI features associated with a guide star - brightness
properties, SNR, FWHM, etc - relate to the primary star, not the entire list. Multi-star guiding can be enabled or disabled while guiding is active.
However, enabling the feature will force another 'auto-select' procedure. The multi-star algorithm uses the secondary stars to refine the centroid
position and reduce its volatility, so there is essentially no way for it to degrade guiding performance."

So there you have it.

Ian

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  • 2 weeks later...

I will follow with keen interest.

I am in the process of selling off some little used gear to partially fund one of these if the reports are good.

I don't use extreme focal lengths so hopefully the guiding is good enough.

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