First Imaging Impressions of the ZWO ASI294MM - Part 1

I've finally put some serious imaging time in with the ZWO ASI294MM so I thought I'd share my observations to date with you. I am enjoying the camera and there is real improvement in image resolution when using it with my William Optics RedCat 51 and Gran Turismo (GT) 81iv. And there are some things we need to discuss...
Earlier video discussing the ASI294MM specifications:
kzbin.info/www/bejne/l3irgGuCn9RpfrM

[@AF29007]

I changed from the ASI533MC to the 294MM and have been very happy with it. The unlocked 1x1 bin mode gives some more versatility.

[@Aero19612]

Absolutely! Hard to find options with 3.8um being the "standard". So far, so good (well, except for that "noise net"). Thanks for watching, Andrew!

[@Astrogator1]

Thanks for a really useful video can’t wait to see how I apply it to imaging with my 294

[@Aero19612]

Thanks for watching, Mark! Good luck with your 294.

[@mohammadranjbaran1897]

Thank you James. I liked your presentation very much.

[@Aero19612]

Thanks Mohammad!

[@jjjscharf8059]

Great analysis and insight. Thanks much :)

[@Aero19612]

Thanks for watching!

[@celts88-78]

James, another fantastic video 👍 How lucky am I to find your channel as only yesterday I received my GT81 IV, and I also have the ASI294MM Pro with 3nm Chroma LRGB & SHO Filters. As you have these combinations I will learn soooooooo much valuable info from your videos (I'm completely new at Astro). Thank you again for your fantastic videos 😃

[@Aero19612]

The GT81 is a great scope. You'll love it. And the ASI294 is a good match for it.

[@joebiscoeiv747]

Love the videos! I am really learning allot with the simple breakdowns! Thanks for putting these together. 👍🏽💯

[@Aero19612]

Sorry for the late reply, Joe! Must have had an astrophotography emergency or two. Glad you’re getting something out of the videos!

[@AZ4Runner]

great info James! love your videos.

[@Aero19612]

Thanks Jason!

[@mikelockwood2104]

well done James. I purchased the 294MM back in summer 2022 - other than the amp glow ( which calibrates out ) it's a great camera. You taught me a thing or two in your vid....using Bin 1 on Ha & Lum.... Bin 2 on RGB & Narrow band. Very good tip

[@Aero19612]

Hey Mike. Welcome to the “294” club. We don’t have T-shirts… try the mixed-mode imaging and see what you think. It’s a pretty versatile camera. You might check your stock portfolio and buy shares of Seagate or Western Digital. Thanks for watching.

[@mikelockwood2104]

@@Aero19612 I agree on Seagate & Western Digital - those Bin 1 files are HUGE ! I process all of my files in Astro Pixel Processor

[@JoesAstrophoto]

Great video James! I love the process and image container tips, I'll be using those. I've never seen that issue with the read (looks like walking noise) with my 294, but I always use gain 120 on both modes.

[@Aero19612]

Ha. Don’t waste time with Pixinsight’s image containers! Make yourself a nice container out of inlaid wood. You got mad skills buddy. Fortunately, I have no such useful/artistic skills so I’m stuck with astrophotography. Regarding the 294: Absolutely. I’ve learned my lesson the hard way. It’s Gain 120 in bin-2 mode. Period! Remember us sleep-deprived folks when you’re rich and famous, ok?

[@LogansAstro]

Very interesting video James. The noise pattern you showed really looks like walking noise that you get when not dithering as it's all oriented in the same direction (raining noise), I presume greatly accentuated by being at gain 0 in Bin2..... but I am certainly no expert. I must remember to use the process and image containers you nicely demonstrated.

[@Aero19612]

Hi Logan. I’ve seen the “raining noise” before, but it’s rare. This is sort of similar, but the scale of this noise is much larger so +/- 10 pixel dither wouldn’t make a dent. Oh well, I’ll experiment in galaxy season. To make matters more challenging, my [only] 3-yr-old Ultimate Power Box decided it didn’t want to work anymore last night. That solves my noise problem. Been trading emails with Pegasus Astro support so I’ll see where that leads. Hope all is well for you and that you’re off to a fast start in 2023!

[@MichaelDuFresne]

Thank you for posting this video. I'm currently looking into which camera to get, and the two I'm looking at most are the ASI294MM or the ASI533MM. I haven't made up my mind just yet, but the 294 edges out on resolution, while the 533 seems to have especially good noise and efficiency.

[@Aero19612]

Hey Michael. Yep. I looked at the 533 as well. Really like the 14-bit ADC and efficiency. Also, no amp glow. Calibration handles the 294 amp glow, but still. As I said in the video, the smaller pixel size did it for me. Lots of competing issues when comparing camera specs. There's probably no wrong answer. Good luck!

[@emuhead]

Hi James, I learnt about the ImageContainer concept from your video, thanks! To me that noise looks clearly like walking noise that a simple dither would take care of. Which then begs the next question, because you've dithered you can then take advantage of Drizzle. I do both in all my images always and the difference it makes is night and day when it comes to improving detail, star shapes (blocky to round), and also reducing noise. Id love to see a comparison of the 294 in Bin 1 vs 294 in Bin2 (or even the 1600) dithered & drizzled. I would bet it's very close.

[@Aero19612]

Ha. I will NEVER learn everything in PixInsight. Take it step by step. Yes, the noise does look like walking noise, but the scale of it is so big. A typical dither is within 10 pixels or so. Here, the "noise ellipse" is about 300 pixels, so I don't see how dithering erases that. Also, I don't see it in Lum at all. I'll get a chance to attack this issue in galaxy season. Who knows, dithering may solve it. Thanks for watching, Andy!

[@addos999]

it is indeed read noise james. i had the same experience, and you also can get cross hatching in some circumstances. this is even with over 25 hrs on a single channel - unless you're in ultra dark skies you simply cant swamp the read noise and still get usable background. the answer for me was if imaging at bin2, must be at hcg.

[@Aero19612]

Thanks for the confirmation! Will definitely be shooting Bin2 RGB at 120. Thanks for watching!

[@tezza0905]

James, interesting video as always. I have an ASI294MC-Pro and a QHY294MM-Pro, so same sensor as you are using but not the same configuration. I used to have trouble with flat frame calibration until I read somewhere that there is an issue with the electronics on the ASI294 with shorter frames and the recommendation was to use a minimum exposure time of 3 seconds for flats. So that’s what I do with both cameras and I have a home-made flat panel that allows me to use the dynamic brightness feature in NINA to create all my flats with this exposure. The advantage of this is that I can use a master dark in creating the master flats. Using this approach, I’ve never had a problem with calibration on either camera. I see from your slides that your L, G and B are all shot at

[@Aero19612]

Hey Terry. I have also heard various comments about the need for a minimum exposure for flats. Actually, we have different sensors. The MC is a Sony IMX294 and the MM is a Sony IMX492 (not sure of difference except being able to unlock the bin1 mode in the MM. Also odd that 4-9-2 is just the reverse of 2-9-4). For the 294MM, I have not experienced problems with low-exposure-time flats (at least not that problem). That said, because I keep shooting myself in the foot with dew issues, I keep having to re-take flats. So my next video will be my Flat-taking along with the stupid "experiment" I performed.

[@tezza0905]

@@Aero19612 Hi James, I've just done a quick set of measurements on my QHY294MM-Pro, doing dark exposures from 0 up to 30 seconds. In both Bin1 and 2 modes, there is definitely something odd below about 3 seconds in Bin1 and below maybe 4 seconds in Bin2. If I could attach the graph I would (I assume I can't in comments on KZbin). I know this is not a ASI294MM-Pro, but I am sure that the mono cameras do use the same Sony sensor. The other thing about these low exposure times is that the ADU numbers jump about a bit in a way that they don't at longer exposures. I have no idea whether this is related to your calibration problems, but it does seem to suggest that the 294MC and 294MM cameras share similar quirks. t Bin2 Bin1 0 1942.01 1882.5 0.1 1941.88 1882.16 0.2 1941.73 1882.04 0.3 1941.82 1882.02 0.4 1941.85 1882.13 0.5 1941.93 1882.04 0.6 1941.99 1882.06 0.7 1942.02 1882.09 0.8 1942.17 1882.04 0.9 1942.15 1882.06 0.99 1942.23 1882.03 1 1942.2 1882.28 1.5 1942.53 1882.11 2 1942.12 1882.44 2.5 1942.23 1882.58 3 1942.28 1882.62 3.5 1942.29 1882.7 4 1942.35 1882.78 4.5 1942.38 1882.71 5 1942.42 1882.78 6 1942.49 1882.77 8 1942.61 1882.88 10 1942.69 1882.95 15 1943 1883.16 20 1943.31 1883.2 30 1943.78 1883.51 I couldn't show the graph, but these are the numbers from just single exposures.

[@Aero19612]

@@tezza0905 Excellent work, Terry! You can always send me stuff through email. Go to the Channel Page and click "About". So, it's not the FLAT frame, it's the DARK-FLAT? I just took flats with my ASI1600. If you have the subs from a "good" exposure time and a "bad" exposure time, use PixInsight's batch processing "Statistics" script to create a csv file of the subframes and put that in an email. I won't be able to test my 294MM until I go to the SCT.

[@PhilFXPhoenix]

Very nice review. Was looking at this camera for exactly the same reasons. Just debating now if I want mono or OSC. I will have to put more thought into that as there are good reasons for both but leaning toward mono. Where I live for most of the time in Phoenix my skies are typically bortle 7 at the start of the evening and end just into bortle 6. (obviously when there is little to no moon) I have a new C14 Edge HD arriving in a few days and was thinking of both that and my RedCat51 for use with this camera.

[@Aero19612]

The MC is great for the C14 with the binned pixel size of 4.63um and RGB is perfect for galaxies. Keep in mind that for the RC51, you want to use Bin1 mode for the small pixels (2.315 um vs 4.63 um). But the MC version does not have the "unlocked" Bin1 mode like the MM.

[@PhilFXPhoenix]

@@Aero19612 Ah good point. I wondered about that. I figured the 2.315um pixel size would be great for the RedCat51. I’ll pick up the mono version. Thanks!

[@anata5127]

I noted your FWHM. They are incredibly good. I usually look at it and eccentricity (both are essentials of resolution) when people show KZbin videos and tell about their systems. So, I noted that only people using massive scopes or Tak, TEC and AP get below 2. Majority gets FWHM around 3-4 with 80-100mm scopes.

[@Aero19612]

Yeah, these are my best values so I assume seeing/air mass/guiding were at their most favorable.

[@anata5127]

@@Aero19612 These are really great numbers for 80-100mm scope.

[@JonnyBravo0311]

Interesting approach of upsampling the calibrated images and then registering / integrating. I've always just done a drizzle integration... but it's not often I do mixed mode imaging. Most of my imaging this past year was with the 8" EdgeHD, so it's all been bin2. I became unhappy with my GT81, especially once I used NINA and Hocus Focus to get the proper spacing for a flat field and minimized the tilt. Soon as I did that, the stars on the outer 1/3 of the image were atrocious. It was especially apparent when imaging in bin1 mode. Sad that the glass can't even properly correct across the 294's sensor. Ever since then, the GT81 has sat on a shelf. I tried going back to the best compromise, but... well, now that I saw what it looked like, I can't unsee it. Regarding that noise... I don't see it on mine. I just looked at some old RGB data of the Dark Shark I did at bin2, gain 0. I see some minor banding when I really boost the stretch, but nothing like what you were showing.

[@Aero19612]

Wow. That's disturbing about your GT81. Have you approached the supplier or William Optics? Maybe it's defective and you can get a replacement. Right - I don't see the noise as obvious on other RGB targets. I think a player here is the background light. When I was shooting M33, there was no Moon. Rare. So, I think that low background helped to let the noise come through.

[@actudoran]

Loved it 😅! nowhere near my budget to go mono at this time.... I just took possession of the university loaned C11 for NEO detection testing threshold... yup a Hyperstar would be grand ... unfortunately it came with a 1.25 visual back so I pulled the trigger on an Imx585 paired to a 0.5 reducer.... I'll have to get a secondary vixen on top to fix my 135 f2 as a guider for short exposure guiding and hope for the best :) loved your combo of binning modes! at FL 1400 with that small sensor my exposures should be pretty short for NEO synthetic tracking (under 20 secs) my 135 f2 plays nicely with the 585 ... yup better details than with a DSLR as the pixels are 2.9 as opposed to 3.8 and 4.3 ... it'll take some time to get the C11 up to the task ... hoping to catch the galaxy season with it well sorted :) Happy new year buddy!

[@Aero19612]

Wow, a C11. That's a beast. Congrats, Alex! My C9.25 is a constant learning experience. Happy hunting!

[@robertarmstrong9406]

Well done. Wondering why you're keeping the 1600mm on the ED102. I have the 294mm with ed102. Do you see problems with the set-up? Just got the ed102. Haven't take an image yet. Still trying the get the back focus set.

[@Aero19612]

No. No problems. It turns out that a 3.8um pixel size pairs very well with that focal length. If I used Bin2 with the ASI294, I would lose resolution because the binned pixel size is too larger (under sampled). If I use Bin1, the smaller pixels don't hurt, but also won't provide improved resolution (over sampled), because the scope's aperture will be the limiting factor. Using the ASI1600 on the ED102 lets me spread the imaging load across two cameras and maybe saves some wear. You might experiment with the mixed-mode approach I'm using with my RedCat and GT81. But also try shooting all Bin2 and see if you can tell the difference. You'll be fine with your setup. Enjoy!

[@old_photons]

Hey James, great work here and how timely - I just had a 294 delivered this week vice my 1600. I've got a C8 SCT I bought before I knew I'd be getting into imaging and a WO FLT91 I just got in November (and totally love). Anxious to apply your rationale and see what I see. I had always used an offset of 10 on the 1600 and last month I spent some time evaluating what offset vs gain on dark frames via SharpCap and decided on different values to ensure there was no clipping of the histogram for the gain settings I used. Jury is still deliberating on the result of my targets. With a cloudy week ahead - I planned to do the same analysis on the 294. My only question or suggestion was how did you decide on the single offset and wonder if that is a contributor though it is just a stab.

[@Aero19612]

A good pair of scopes there, David. I use Offset 20 for my ASI1600 just because I saw that somewhere and I was brand new to the monochrome game. I did do a study for offset with the ASI294 and found 10 was ok (not gospel, just ok). Since then, I monitor where the tail of the histogram is during imaging and haven't found any need to changes. Depends on your skyglow and exposure times. If you come up with some ah ha observations, please pass them along.

[@MatthewHolevinski]

@11:27 hehe. Excellent video as always, you better get to processing those frames :) They aren't going to process themselves.

[@Aero19612]

That's the truth. It's a pity that eating, sleeping, and a real job keep getting in the way. Thanks for watching, Matthew!

[@DavidSilesIT]

Really good approach, as always. I have been using this camera for more than a year now and I'm quite happy with it. I'm never used it under gain 120 in bin2 mode because of the drop in read noise. Also, I wonder why is better to use bin1 with a focal length of 800mm. I only used it with my 275 mm telescope. I will try it on galaxy season. Thank you again.

[@Aero19612]

Hey David. I'm enjoying the 294 as well. Still climbing the learning curve. You are wise to keep Bin2 gain above 120. I was hoping to be able to use longer exposures with the RGB filters at Gain 0, but I think read noise is eating my lunch. I don't think Bin1 helps above about 700mm. Once you transition to over-sampled, you don't see any benefit of the smaller pixels. One thing however: I am thinking I'll try Lum in Bin1 with my SCT just so I can use a longer exposure and cut down on the number of files. Some more experimenting for galaxy season...Thanks for watching!

[@nathanielcharbonneau1726]

Looking at that rat's nest on the redcat setup makes me feel better about my life's choices. Mine looks 'slightly' better.

[@Aero19612]

Indeed it is a rat's nest. I've thought the same thing. When I use a different scope, all of those cables don't look so bad with a large refractor or SCT, but the Redcat looks like it's burried.

[@nathanielcharbonneau1726]

@@Aero19612 Cable Management is definitely not one of my strong suits. I've gotten much better at it after some deliberate time spent researching techniques... but I still get freaked out every time I slew my rig to a new position while I'm inside the house.

[@nathanielcharbonneau1726]

@@Aero19612 Also, I'm a huge fan of your videos. You speak clear and concise and relay important information very well.

[@McOnni77]

Hi James, absolutely love your channel. Great work! I had the same thoughts about the pixel size of the ASI294MM Pro paired with a RedCat51. So I purchased that camera and I really love it. The only issue I have is: When connecting the camera to 12V it starts immediately to cool down the sensor from 23°C ambient to 13°C within a minute but without setting a target temperature and without sending any command via ASCOM. I contacted ZWO Support and they told me that's not normal, perhaps an issue with the temperature sensor, and gave the advise to contact ZWO in China to open an RMA. They replayed: That's normal. When connecting 12V, the cooler starts with 1% power without any command. No repair required. However, I haven't seen that kind of behavior on any other of my cameras. They start cooling only after sending the command. Question: Does your ASI294MM Pro show the same behavior? Does it cool down about 6-8 Kelvin when connecting 12V? For me it looks weird.

[@Aero19612]

Hey Dominik. Thanks for watching! No. That's not how any of my ZWO cameras work (ASI1600MM, ASI294MM, and ASI294MC). Perhaps it depends upon what software you use to control the camera? I use NINA and when I connect to the camera, there is no cooling until I press the cooling button. Could the auto-cool behavior be common to, say, the ASI AIR? What camera control software are you using?

[@jonrbryan]

I have read on Cloudy Nights and Sharpcap forums that gain between 120 and 200 on the 294 is "problematic," with examples of the kind of noise you are seeing. Supposedly, the Sony datasheet recommends against gains in that range

[@Aero19612]

Hey Jon. Hmmm. Sounds fishy to me. The problem with forums is that there are a lot of people saying a lot of things but only some of it is legit. First, my issue with noise(?) was when I was shooting RGB at Gain 0 in Bin-2 mode. Read noise is VERY high there. Haven’t had clear skies to test RGB at Gain 120. I have a lot of SHO images at Gain 120 in Bin-2 and have no issues with noise. Anyway, I seriously doubt a well-known and widely used camera like the ASI294 behaves problematically at and above the gain where it’s supposed to be used and the High Conversion Gain (reduces read noise and full dynamic range) kicks in. We’ll see! Thanks for watching!

[@Aero19612]

Jon! Just read your KZbin bio. Fantastic! Awesome career. Congrats! This is just the hobby for you. A home away from home.

[@mechkiller31st]

Great work. For my RC51 and 294mm Pro I have been using 20s for RGB. it has worked best for me. at 30s it seems like i get too much LP in the images. I am in a bortle 6 so maybe if you have darker skies you might be able to go longer. for RGB i am using Baader filters. I am shocked you are not Dithering. I know it sucks to dither when you are taking sub 60 second images, but for those i dither every 10 or 15 images. for my SHO i do 240s subs and dither every 5. I can honestly say that after 2 years with this setup I have NOT had any of the artifacting you have shown. I use an EQ6-R Pro as the mount FYI

[@Aero19612]

Dithering is a great thing to do. I had a CGEM before my current mount (EQ6-R). Performing reliable dithering with that CGEM just wasn't doable. I do need to start playing with it with the EQ6-R - much better behaved. I shoot long (~100 sec) for the target and end up blowing out many stars. But then I take ~20 min/filter RGB at 30 sec just to get the stars. That way, I cut down on the number of files to process. Question: Do you shoot RGB in Bin2 at 0 gain?

[@mechkiller31st]

@@Aero19612 I havent shot Bin2 since they released the firmware to do Bin1. I was going to be doing Bin2 with my C9.25 for Galaxy season but up here in the Chicagoland area I havent had a clear night in nearly 2 months. I have been doing Bin1 Gain 108 SHO 180s and Bin1 Gain120 for LRGB. L=15s RGB=20s I do dither and have not had ANY issues since running with these settings. SHO dither every 5 LRGB dither every 25. Yes its a lot of images to process with my Andromeda image being the most subs at a whopping 1707 (11.24hrs)... needless to say my PC was NOT happy with me on that. I do use a 2TB Samsung EVO 850Pro NVME for processing so things normally dont take long... but that was a long wait.

[@Aero19612]

Keep in mind that the read noise in Bin1 is still very low at Gain 0, so you could use longer LRGB sub exposure time and cut the number of files by 4ish. The problem I'm seeing is in my RGB at Bin2 and Gain 0 where the read noise is 3-4 times higher than in Bin1.

[@anata5127]

I use the same camera. I use only 121 gain weather it is bin 1 or bin 2. I never allow to drop resolution below 0.8”. Absolutely counterproductive. So, pixel size and FL must give 0.8-1.4”. In your case, I will not use 294mm with SCT. There is new Omegon camera with 9um pixel. This one to use. 2x bin should be used for FL of 800-1000mm. So, you need additional camera and additional scope, such as 140mm TEC. One more thing, dynamic range of final photos is low. You make them very bright and clip background. Why?

[@Aero19612]

Gain 121 is the right approach for Bin2 - I learned that the hard way. For Bin1, there is no discontinuity in the curves so you have more flexibility. Using 121 for both does help to prevent errors though, so that is an advantage. I disagree that using the ASI294 in Bin2 mode with an SCT is "counterproductive." It's never counterproductive to be over-sampled, you just don't get any resolution advantage. To me, it is counterproductive to buy a new camera just to end up with the same image. Most people in this hobby want to get the best images possible with the least amount of money spent. You can always buy a ton of equipment if you have the money lying around, but the real challenge, for me anyway, is to maximize image quality per $. But everyone plays this game the way they see fit, so be the best YOU you can be!

[@anata5127]

@@Aero19612 Viable approach. I keep alternative one. Upgrade all the time: sell old, get better. Deciding “better” is tricky. I have a SCT, and question was “why to have it?”. Vixen ED103SS duplet generates much better pictures. In reality, it only started to serve it purpose, when I got appropriate camera and mount.