Using the ASI294 Bin Modes

It's finally time to start using the ZWO ASI294MM camera I bought several months ago. I've been waiting for nebula season so that I can get better resolution out of my William Optics Redcat 51 and GT 81 with smaller Bin-1 pixels of the 294MM. Bin-2 mode is a great match with a long focal length telescope, like an SCT. We review the specs for ASI294MM and compare them to the ZWO ASI1600MM I've been using.

[@razorwind5949]

I love the tooltips and summary!

[@celts88-78]

Golden information James 😃👍

[@emuhead]

Amazing work as always! That nebula detail comparison is quite something. Looking forward to more of those to really drive the smaller pixel argument home.

[@Aero19612]

Thanks, Andy! I am pleased with the improved detail these smaller pixels provide. Keep on imaging!

[@1MoreMojo]

Great work , thanks for sharing!

[@Aero19612]

You bet, James. Thanks for watching!

[@AstroCrescent]

Nice detailed review. I’m thinking of upgrading from my current ASI533MC Pro to monochrome. Your review will definitely be very helpful. Thanks a lot.

[@Aero19612]

Glad you found it useful!

[@agastrophotos]

Great video, I just "upgraded" to this camera from the OSC version, pairing with an 8" edgehd. Lots of info, thanks for sharing!

[@Aero19612]

Hope you have a big hard drive!

[@danjensen9425]

I just got into narrowband and bought the 294 mm . I have the redcat , the Stellarvue 102 apo and the C8. I just got the zwo autofocus motor for the C8 . Great videos thanks again.

[@Aero19612]

Good assortment of scopes, Dan. The 294 should work well with all of them. Thanks for watching!

[@DavidSilesIT]

I also have the 294mm and a similar setup as yours (275 mm and 640mm). The duality of that camera was the critical point to buy it. I'm very pleased with the results.

[@Aero19612]

I’m getting used to it. Still have a mental image of a fire hose pointed at me when I’m in Bin-1 mode. Poor computer.

[@CaptRescue2]

533MC Pro is my first camera so I'v been square from the begining. Great video and look forward to the next one!

[@Aero19612]

Maybe the only case when it’s good to be “square.” Haha. What am I saying? I’ve always been square.

[@LogansAstro]

Very useful video. Still trying to decide whether or not to get this camera for use with my Redcat.

[@Aero19612]

Hey Logan. Go back to a few of your best subs with the Redcat and let Pixinsight determine the FWHM. If smaller than about 4.0 arc-sec, then the smaller pixels of the ASI294MM won't help you much and you'll take a hit with the 12-bit ADC. In that case, stay with 2600 (is that what you're using with the Redcat?) and the 16-bit tonal resolution.

[@TomDastrup]

It's interesting that we've ended up with such similar gear. My first good scope was the edgeHD 9.25 on an eq6-r pro. First camera was OSC with the 294mc pro. When I decided I wanted to go mono, I got rid of the 294mc and bought the 1600mm pro. That was like 2 weeks before the 294mm was released. I told them I wanted the 294mm instead and they actually let me send it back and upgrade to the 294mm. I knew one day I would eventually get a small focal length scope, so when they announced the bin 1 mode, I was ecstatic. This week, after 3 months on backorder, I finally got the Askar 400 and .7x reducer, so I'll be able to shoot wide field at 280mm focal length. It's going to be awesome. Still waiting on the guide scope and a couple other accessories before I can get first light with it, though. Thanks for the videos. Keep 'em coming. 🙂

[@Aero19612]

Wow. That was nice they let you switch out the 294! After I bought the Redcat, I became much more concerned about focus. Your Askar 400 has a standard rack/pinion focuser that is more amenable to attaching a standard focus motor to it much easier than the Redcat. It's a good focal length, particularly with the 0.7 reducer. Now you just need a 700 mm focal length scope! Thanks for watching, Tom.

[@TomDastrup]

​@@Aero19612 I have a strange problem with my 294mm that I'm hoping you'd be willing to help me troubleshoot. My darks calibrate out the sensor's amp glow for my Ha subs, but not for my Oiii or Sii subs. I don't know how that's possible since the subs were taken on the same night with the same camera temp, gain, and offset settings. I found that when I multiply the master dark by 1.75 (or so), then subtract that from the Oiii and Sii subs, that more or less neutralizes the amp glow. I've asked a couple astro communities on discord and no one had any ideas. I'd very much apprciate any help/suggestions you'd be willing to offer!

[@JoesAstrophoto]

Great video Jay! I love my 294MM and use it in both modes depending on the telescope. For the money, it’s the best cmos camera available in my opinion. That being said though, I also really like my 2600MM, it’s a tough choice sometimes. I think the 294 in bin 2 does a much better job with the longer focal length scopes unless you can guide consistently around .3” total error which I am unable to do.

[@Aero19612]

You can't beat the 16-bit ADC of the 2600 and its field of view. A shame we don't have more 16-bit astro cams with smaller pixels that work better with focal lengths < 600 mm. Guess we're at the mercy of the security cam business.

[@textandtelescope8199]

Great piece. I have the 294mm but never understood the application. This laid it out nicely. Thanks. Now if only the skies here deep in the heart of D-FW would clear up for a fair amount of time!

[@Aero19612]

I’ve been using the 294 as I describe in the video and will put out a follow-up commentary later. We had so many good imaging nights from July to August that I was begging for rain. The we got the rain, and more rain. I got out last night and hope to get three more nights…famous last words. Thanks for watching!

[@textandtelescope8199]

@@Aero19612 Well, this liberal arts type is unashamedly taking advantage of those like you of a more mathematical/engineering bend to do the leg work!

[@Aero19612]

Glad to do it. But it's your job to pull out the wheat from chaff!

[@textandtelescope8199]

@@Aero19612 True, true!

[@davidschaeffer5322]

Told you it was a cool camera. 😎 I love the video. Gonna have to try gain 0 for rgb and 100 for narrowband in bin 1. Thanks for the info. And yes the files are filling up my storage space like crazy. 🤪

[@Aero19612]

I think I'm going to enjoy using it...as soon as I crack the code on the best way to do that, that is

[@leeratliff7588]

I saw a video of a lecture by Robin Glover, the developer of SharpCap, which indicates that we don’t need to cool modern cameras nearly as much as we often do. More accurately, the point of diminishing returns is at a higher temperature than you might think. I won’t go into all the reasons because he explains it much better than I would. The same video talks about many other aspects of CMOS cameras which really expanded my knowledge. Highly recommended. Search for “robin glover” and it should be the first result returned. It was published by AstroFarsography, who recorded it live.

[@Aero19612]

Hi Lee. Agree! I've watched that video several times. It is good and very informative. I've been using the ASI294 (cooled to -5C) and have noticed no issues with that vs the -10C I get out of my ASI1600. I think the most valuable part of the Glover talk is that really long exposure times don't but you anything image-quality wise (you do get the benefit of reduced hard disk space and processing time, which is worth something). The key is to use a long enough exposure so that read noise doesn't dominate. Thanks for watching!

[@DamianVines]

Amazing video as always thank you very much! I too have the Redcat51 paired with the 294MM.... I'm curious, when in Bin1, have you settled on Gain 0 for RGB and Gain 100 for narrowband? Also... is it true that the time need to achieve the same SNR would be 4x longer in Bin1 vs Bin2?

[@Aero19612]

Hey Damian, Yes. I'm satisfied with Gain 0 for LRGB in Bin1 and Bin2 (I never shoot L in Bin2). I continue to use Gain 100 for SHO in Bin1 and Gain 120 for SO in Bin2. The 100 is a total judgement call - no firm justification for it. I want high enough gain to keep exposure times reasonable (< 10 min for me), but I want max dynamic range (i.e., need low gain). I settled on 100. It's not magic. I'll shoot every filter in Bin2 when I pair this camera with the C9.25. Not sure about the SNR question. I'll have to think about that. Mostly, I wanted the smaller pixels to improve resolution with my Redcat and GT81. Thanks for watching!

[@anata5127]

Actual FWHM depends not only from atmospheric effects, but also guiding. Look difference for long and short FL scopes.

[@sbklb1]

Awesome info - I have been using the 294MM for 1 year and really like the ability to bin1 or bin2. one challenge with bin1 is the really large file sizes overwhelm my Raspberry pi when writing to SD card, given you are using small windows pc, will be interested to know how that performs. I might have to rethink how to use the delay feature on my image collection to see if that helps to I can use bin1 for the full frame. part 2 - there are many targets I go for with my 600MM Newtonian where my decision is whether I want the full bin2 FOV or only a portion and I select out a 1/4 frame portion in the middle of the sensor and use bin1 with a portion of the frame and collect just that so I can have smaller file sizes and small pixels on those targets. In my case, I create darks and flats for both versions. I had given up on using bin1 for the full frame, but might have to retry that for M31 based on your video. part 3 - I am down the street from you in Dallas and have had a couple nights where I get and image artifact in the center of my frame that I thought was freezing/dew on the sensor that caused me to increase my temperature to 20 C (yikes), and have considered a dew strap around/near my camera and filter wheel to see if I can lower my temperature at the sensor and keep the freezing off -- not complete on that test, but interested on whether you see anything similar. Great video as always, love your engineering mindset and clear explanations on your thought process and journey.

[@Aero19612]

Isn’t Dallas fun this time of year! On the positive side, we’ve had lots of clear imaging nights. My mini PC is handling the large file size OK. I’m surprised. Heck, it even handles the 0.5-sec flats I take with the Lum filter. I just take flats in Bin1 then resample down to bin2 flats. I haven’t observed dew issues, but dew hasn’t been an issue since I’ve been using the camera. Fingers crossed. Thanks for watching!

[@robertw1871]

Very nice…. That’s the one thing keeping me in the OSC realm is the terabytes of storage needed for mono… When 64g of ram and 16 processors seems insufficient… I’m running the 2600MCP and it’s fairly brutal at 51m per frame, not needing hardly any calibration makes it ideal for my limited time…

[@Aero19612]

File size is a pain. I subscribe to a cloud storage service (iDrive) where I keep all my calibrated subframes stored. I process each night’s set of subs and ditch the raw files. Thanks for watching, Robert!

[@Larstronomy]

Hi James, Great video! I've been using my ASI294mm Pro with my 336mm FL for a while now, so far I've only used bin2 but it's really tempting to start using bin1 because of the higher resolution. Would there be any reason to not shoot all 3 channels (SHO) in bin1 if file sizes aren't a problem? I wish I could experiment a bit more but I live in the Netherlands and the amount of clear skies we get is very limited. Thank you so much and keep up the great work!

[@Aero19612]

The only thing with going all in on Bin1 is that you lose the 14-bit tonal resolution it provides. But it’s hard to say what the visual hit is for that. Who knows? Maybe nothing you can see by eye. Give it a shot and see if you like the results. I know, cloudless nights are like gold. Probably more so for you given your latitude. Good luck!

[@Larstronomy]

@@Aero19612 Thank you so much for the reply! Can't wait to test it out next clear night. Unfortunately running into some pretty bad mount problems, something with the worm probably, can throw away a sub every 10 minutes. Yikes.

[@alimartins6669]

great work James. thanks! Can you quickly elaborate on why 0 gain on LRGB Bin2? Shouldnt one go with 120 as it would give a lower read noise with same DR? Thanks again

[@Aero19612]

Hi Ali. My original thought was that I wanted to use Bib-2 for the RGB filters as I just want color, rather than detail. Also, RGB lets in a lot more light than the SHO filters so I didn't want very short exposures with the gain 120 and went with the 0 gain. In retrospect, I think I'm seeing the bad effect of high read noise that goes with 0 gain in bin-2 mode. Next time I use this camera, I'll either use bin-2 at 120 gain (and see how short the exposures are) or just go with the gain 0 in bin-1. If the bin-2 gain 120 exposure time has to be < 1/4 the current exposure, I may settle for using bin-1 at 0 gain.

[@alfredobeltran611]

As usual, great video James.. I’m considering the 294MM to use it with the C9.25 EdgeHD. It’s a good mid point between the small 533MM and the 2600MM. Nevertheless, two things make not consider it and I’d like to know your opinion as a user of that camera with also a C9.25. First, amp glow. Is this or isn’t a problem, and can it be calibrated? Second, I’ve read also in forums that the sensor coatings are very prone to produce a mottled pattern when used with red filters and specially with very narrow band Ha and SII filters. Is that the case? Can it be also calibrated?

[@Aero19612]

Hi Alfredo. There is significant amp glow (I’m taking 600 sec subs), but the darks completely compensate for it. I have not noticed the mottled appearance at all. If it’s there, it must be subtle. I might be inclined to assume the flats would take care of it if it’s a legit issue. Hope that helps. For what it’s worth, I’m enjoying using the camera. Planning on a video discussing my experience using the camera with my Redcat 51 as soon as I can find the time…

[@alfredobeltran611]

Thank you very much James. This camera is interesting for imaging at f10 with the C9.25 EdgeHD because of its high QE and bigger pixel size than the 2600MM. Please let me know If you could share maybe a raw frame taken with it (maybe an Ha if possible)

[@Aero19612]

Alfredo, Here are two Ha raw files and the calibrated versions: drive.google.com/file/d/1Cbp4LyOGEakVdRRRmf07IqnpDHQIVUOO/view?usp=sharing

[@alfredobeltran611]

@@Aero19612 Thank you James. I appreciate it. The calibrated files show no amp glow nor any trace of the dark pattern on the lower right. I can see this were shot with the bin1 mode (with the smaller pixel size). Seems like a very versatile and sensitive camera.

[@MethiasZa]

The spending never ends. New mount ordered (mine was tracking like a dog - mechanical issues). Been wanting to get a shorter focal length telescope, and I have a 1600mm, now I'll need a new scope, and a new camera 🤣.

[@Aero19612]

Such a slippery slope hobby. I’m pleased with the EQ6-R. A good balance between cost and performance. Good luck, Wayne!

[@AstroQuest1]

Excellent video as usual James. I have color versions of the ASI294 and 2600 both of which I love but I do wish I had the money to buy the mono versions as well. My reasons for color had to do with poor FOV and bad weather. The 2600 does have a great view but that also has a large file size at 52 MB vs. the 32 MB for the 1600 so you better have a fast computer. Cheers Kurt

[@Aero19612]

Hey Kurt. Totally understand about selecting OSC to maximize imaging time. I'd love to have the 2600MM, but that means a new (larger) filter weel and filters. So it's not just the camera, it's the additional $1000 to $2000 for the other stuff...keeps on adding up.

[@AstroQuest1]

@@Aero19612 Good point, that was my other concern, I was planning on upgrading my filters to the Antila and there is a big difference between the 1.25 vs 2". When the time comes to upgrade my 1600MM, I am leaning towards the ASI294MM or the ASI533MM (which is out in other brands). The 533 has the same pixel size as the 1600 and 2600 but the sensor is smaller. The good news is it has no amp glow.

[@Aero19612]

The amp glow with the 294 is very apparent. The darks take care of it ok. All things considered, the 294MM is just "OK." I just wanted the small pixels to improve resolution of my shorter focal length scopes. Vast majority of cameras have 3.8um pixels, which is good for focal lengths > 700 mm.

[@sbklb1]

@@Aero19612 Agree on the amp glow on 294MM -- when > 120 second exposures I get a plumb on the side about 1/4 to 1/3 in on that side. it is cured with calibration, but is annoying.

[@hm.salgado]

There are so many videos out there but never seen one discussing the performance of the ASI294 in the two bin modes. Very relevant indeed for us amateur astronomers; thanks for sharing. Just curious, did you have any issues calibrating the lights due to amp glow? Looking forward to your next video.

[@Aero19612]

Hi Henrique. That was something I had meant to show and discuss, but I ended up deleting half the material because the video was so long. In short: No. The amp glow is a "sunburst" type light and is very noticeable. I have found the Darks are doing a great job of eliminating the amp glow (see the right-hand side image at 13:00 in the video). Thanks for watching!

[@hm.salgado]

@@Aero19612 Thanks for the reply. It is good to know since I have plans to buy this camera in the future.

[@sbklb1]

@@hm.salgado I agree with James, same problem, especially when > 120 seconds, but is cured through calibration. I am a lazy data collector and calibrator so have darks at 20, 60, 120, 180 seconds and try to get close to those for exposure time. James and I are both in Bortle 7-8 DFW skies -- you can go longer than 180 second subs, but you end up balancing the amp glow and the light pollution. I have a fixed setup so can good polar align and a good scope with guiding and have thought about trying longer subs, but really just results in more planes and satellites in every sub.

[@DeveshPande]

Hi James, great video. Just bought myself a 294mm. I ache 3 scopes. The Redcat, 640mm Orion 115EDT(Reduced 0.8X) and 8" Edge HD. At what FL would you switch to Bin 2?

[@Aero19612]

Hey Devesh. I would definitely go with Bin-2 on the Edge. You might be able to get away with Bin-2 on the 115EDT if you dither and use drizzle integration. If not, then use Bin-1 for the detail (e.g., Lum and Ha) and, if you want, use Bin-2 for color (RGB and Oiii and Sii). Thanks for watching!

[@DeveshPande]

@@Aero19612 Hi James, Quick follow up. I followed your advice on shooting Gain 0 for LRGB. What is the length of the flats you take for the LRGB filters? Does it need longer flats (>3s) like narrowband filters?

[@Aero19612]

@@DeveshPande Sorry for the late reply! The length of exposure depends on (a) the target ADU level and (b) the brightness of the light source. For me, I don’t care that much about the ADU as long as I’m not clipping on the low end or the high end. I use the Pegasus Astro FlatMaster (this is expensive - plenty of other equally good choices at much lower cost). My L flats are at 0.5 sec and the R, G, and B flats are between 1 sec and 2 sec. Good luck!

[@Aero19612]

@@DeveshPande I apologize for the late reply! Yes, my flat exposures for L,R,G,B are between 0.5 sec and 2 sec. By the way, if you shoot at Gain 0, make sure you're using Bin1. I found the read noise at bin2 and Gain 0 is way too noticeable.

[@DeveshPande]

@@Aero19612 Thanks James. I have been reading conflicting advice about 294mm flats with broadband filters. Some said they need to be > 3s just like narrowband. It's good to know that isn't the case from an expert now :) Thanks for the note about bin1. I shot bin2 for my flats and lights. Are you saying shoot lights at bin 1 too? I will take a look at the noise levels now.

[@valentinotera3244]

Ji James, with 400 mm focal lenght (no flatfiel, reducer and whatsoever) you'd choose Bin1 or Bin2?

[@Aero19612]

Hi Valentino, I’d go with Bin 1 to get detail (Lum and Ha). Alternatively, if you dither when you’re imaging, you can use Bin 2 and use drizzle integration to recover the detail (or at least most of it). Thanks for watching!

[@alanhnatiw1643]

Curious to see how bin 1 compares to bin 2 mode with drizzling…get smaller raw data files and 14 bit conversion

[@Aero19612]

Excellent question, Alan! I haven’t tried that. Add that to the list…

[@alanhnatiw1643]

@@Aero19612 awesome. Was thinking that if you are slightly under sampling then drizzling should help recover some detail

[@davidparadis490]

Curious why is the file size a problem for you?