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I noticed when processing my latest image today that a lot of my subs had elongated stars that were very noticeable so I had to throw out quite a few. My guide scope was a bit loose on the first night so the likely candidate was differential flexure. I don't think that was the only issue though. I hadn't weighted down the carbon fibre tripod and given how light the AM5 mount is, particularly with a Redcat 51 on top, it occurred to me that this could be a problem with any amount of wind or vibration. As I was also imaging with the Redcat 51 and 2600MC Pro the images are under-sampled so Ive been aiming to collect a lot of subs to facilitate drizzle integration in Pixinsight. I was dithering every sub frame and I noticed it would take my guiding a long time to settle down after dithering. I also feel like this was affecting my guiding performance and the numbers were fluctuating from 0.6 ArcSeconds up to 2-3 ArcSeconds. I'm aware of the complexities of guiding but I'm just curious if anyone has faced particular challenges with ASIAIR/AM5 guiding in this respect?  |
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I had trouble with my AM5 because I thought the defaults were specific to the mount. What are your Max Dec and Max RA guide settings? Try 200-400 ms Check the RA Aggr and DEC AGGR settings, they are usually too strong. Mine were 100 and 70%. Try 35-50% range If possible, use 1 sec exposures on guide camera at 0.5 (or 0.25) guiding speed. |
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| I used to use my AM5 with my Apertura 75Q (FL 405mm) (with EFW, EAF, etc it's about 11lbs) without weights on the end or tripod and through windy nights. The only time I had consistent elongation across the field was when I had poor polar alignment. The ASIAIR protocol doesn't always get it right and it's cost me a couple of nights in the past. I usually run polar alignment 2 times in two different starting locations such as one at Polaris and one starting from zenith. When the alignment is on, I usually get 0.2-0.6" guiding. I typically guide with 2s subs as well shooting through dual narrowband filters. My parameters are 15-20% on RA and 55% on DEC. I had those set after hearing I needed to lower aggression but I have never fine tuned them since I was happy with my guiding. These settings worked on my Esprit (30 lbs) as well but I have that weighed down with a counterweight and a 20lb weight in the pouch for peace of mind. |
7.12
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Hard to judge if it has anything to do with the settings or not. I agree with the comments above regarding the aggression. AM5 needs fast exposures to correct for the large PE. So probably won't go more than 1s. I have used it from an Askar FRA400 all the way to a C11 at a fl of 2065mm. Your image scale is 3.1" per pixel. You are significantly under sampled, so it would be very difficult to have trails unless something is massively off. In your case it like was just the winds. On those windy days you might just want to cut your exposure durations to 30s-60s and deal with the significant more data, but can salvage a lot more integration time. |
7.90
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| Ah, my 120 USD mount does better than an 2K USD AM5, that something to celebrate! |
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andrea tasselli: Just today my Toyota Corolla also beat a broken F1 formula car too! All around a joyous day indeed. |
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| Was the F1 car running or just by the side of the road by any chance? Because my "Corolla" has been running for past two hours with 0.58" rms in Ra and 0.28" in Dec. Considered that basically I rescued it from the tip it ain't too shabby, this "Corolla". |
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andrea tasselli: Well when that F1 is running, it was carrying a 35 lb C11 payload at a FL of 2065mm at 0.3-0.4" for hours on both the Dec and RA, while weighing a fraction of the payload, and not needing anything more than a 10lb unbalanced counterweight. I also didn't spend any of my precious time building it or saving it. Here is a thought. Maybe build a company that produces those amazing $120 Corollas, and sell them for $500. You'll beat all the giants. |
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Might be relevant, or irrelevant, but I wish ZWO would put an "Auto" setting for both DEC and RA guide aggressiveness settings It's a pain to manually get it just right It caused me 2 whole arcminutes of guiding accuracy (which is horrible for my setup) at default settings, and I had to spend literally 30-40 minutes trying to find the right aggressiveness I finally made the conclusion to set both numbers between 45 and 65 percent (I forgot which was which; one was 45, the other was 65) Then I could finally get a good 0.70" total guiding accuracy Sometimes I was even getting 0.45", but my AVX cannot handle that accuracy for too long |
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I used the default guiding settings on my AM5 with ASIAIR for a long time. It was only one night recently that I started playing with them, when it was quite windy with some challenging seeing conditions - the default settings struggled. I think prevailing sky conditions play a big part in whether the default settings will be successful, or not, and indeed play a part in what you should change them to. I can regularly guide my AM5 at ~0.3" RMS, sometimes slightly less. For me, a good night is 0.3", a standard night 0.5-0.6", a poor night 0.7-0.8" - give or take a little. |
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If you want a good answer for why I proposed the settings earlier, is comes from someone that knows a lot more about this than me. If you can follow the math and the logic, look at this: https://bbs.zwoastro.com/d/15989-getting-the-best-performance-from-my-am5 |
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Michael: *** Thanks mate. I do tweak RA and Dec aggr spending on how my guiding is performing. Good point about max guiding setting. I think it's set to something ridiculous like 2000ms and now I recall some of the advice from the PhD2 documents about reducing the max particularly when it's windy. I always thought guide exposures should be 2-3 seconds otherwise you just end up chasing seeing? *** |
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Ashraf AbuSara: *** Ye, my stars came out fine in the end and that's by virtue of the image scale. I guess that's also why I'd recommend beginners start with small wide field refractors. It's a lot more forgiving. I still aim to get the highest quality data I can get though. I hadn't actually heard about the need for short exposures with the AM5 so I'm glad I posted this question. I have a feeling my issue was to do with the mount settling down after dithering. I was dithering every frame and the guiding wouldn't take time to properly settle down each time. And this affected shorter exposures more. *** |
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Ashraf AbuSara: There is a setting in the ASIair to adjust the settling time for how many seconds once it reaches below certain error in arcseconds. For example you can say that you want it to start the exposure after it settles under 1" for 3s or 5s if you want. As to exposures for a harmonic mount with no encoders, you have to correct frequently due to the large PE, so exposures around 0.5-1.5 seconds are preferred. |
1.20
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I noticed when processing my latest image today that a lot of my subs had elongated stars that were very noticeable so I had to throw out quite a few. My guide scope was a bit loose on the first night so the likely candidate was differential flexure. I don't think that was the only issue though. I used a 130/900 triplet Apo on my AM5 without counterweight guiding at 0.4-0.5 without any problem. I use short guiding exposure, 1 sec or sometime less. When driving is worse than 0.5 it is because there was a small earthquake (as you can see in the graph). It's true, I'm not joking.  |
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Michele Campini:I noticed when processing my latest image today that a lot of my subs had elongated stars that were very noticeable so I had to throw out quite a few. My guide scope was a bit loose on the first night so the likely candidate was differential flexure. I don't think that was the only issue though. *** Thank you 🙂 Ye, I've had some useful tips on here. I wouldn't have considered shorter exposures usually but I'll give it a go*** |
