ZWO ASI120MM Review & Tutorial

I finally updated my planetary camera from the once popular Philips ToUcam 740K to ZWO’s ASI120MM. This was after reading a number of positive reviews and seeing plenty of amazing photos produced by the ASI120MM. During my second night out with this camera, I realized it would push my imaging results to a much higher level. The detail in Jupiter’s cloud belts and the clarity of the Great Red Spot on my laptop screen was much better than I had ever seen before.

This article is a review of the ZWO ASI120MM camera with a basic tutorial of the methods I used to capture the footage of Jupiter and process it into a detailed composite image in Registax and PhotoShop. All of this is based on my second night out with the camera so I should improve my skills as I use it more. I will make more posts here on AstroPhotography Tonight to share what I learn.

Below is a comparison of my best work on Jupiter with the ToUcam Pro 740K (back in 2005) vs. my second imaging session with the ZWO ASI120MM. I realize there are more factors involved than just different cameras. For one, my 2005 telescope was an 8″ Celestron SCT and my current scope is a Celestron 9.25″ SCT. There may have been differences in sky conditions and how close Jupiter was during the imaging sessions. Still, the difference in the amount detail I obtained from each camera is significant. This really is a testament to the advancements in imaging devices.

Jupiter May 15th, 2005 Jupiter December 1st, 2013
Jupiter with ToUcam 05-15-2005 Jupiter 12-01-2013 with ZWO ASI120MM
This represents my best work the Philips ToUcam Pro 740K and 8″ Celestron SCT. This image is from my second imaging session with the ZWO ASI120MM and Celestron 9.25″ SCT.

ZWO’s ASI120MM Details

Here are some of the main features and spec’s:

  • Sensor (monochrome): 1/3″ CMOS MT9M034 1280 X 960 @ 35 FPS
  • Resolution: 1.2 Mega Pixels 1280×960
  • Pixel Size: 3.75 µm
  • Exposure Range: 64µs-1000s (62 millionths of a second – 16.7 minutes)
  • Interface: USB 2.0
  • Dimension: 62mm X 28mm
  • Weight: 100 grams
  • Anti-reflective coating on sensor protection window
  • Full aluminum housing with standard 2″ interface
  • Integrated ST4 autoguider port allows the ASI120MM to be used as an autoguiding camera
  • Wide exposure range allows camera to be used for planets, Moon, Sun, and deep space objects
  • Can be used as an all-sky camera with the 150º wide angle lens attachment that is included
  • 35 FPS at full resolution of 1280 X 960 / 215 FPS at lowest resolution of 320 x 240
  • Threaded screw ports on back housing for installing thermoelectric cooler
Supported Resolutions
  • 1280 X 960 @ 35 FPS
  • 1280 X 720 @ 46 FPS
  • 1280 X 600 @ 55 FPS
  • 1280 X 400 @ 80FPS
  • 960 X 960 @ 46 FPS
  • 1024 X 768 @ 54 FPS
  • 1024 X 600 @ 69 FPS
  • 1024 X 400 @ 101 FPS
  • 800 X 800 @ 66 FPS
  • 800 X 640 @ 82 FPS
  • 800 X 512 @ 102 FPS
  • 800 X 400 @ 108 FPS
  • 800 X 320 @ 158 FPS
  • 640 X 560 @ 98 FPS
  • 640 X 480 @ 113 FPS
  • 512 X 440 @ 123 FPS
  • 512 X 400 @ 135 FPS
  • 480 X 320 @ 165 FPS
  • 320 X 240 @ 215 FPS
  • 2X2Bin: 640 X 480 @ 35 FPS

Equipment Used

Here is all of the main equipment I used to image Jupiter.

ZWO ASI120MM Camera ZWO Color Filter Wheel ZWO LRGB Filter Set Orion 12.5mm Illuminated Reticule Eyepiece
asi120mm ZWO Color Filter Wheel ZWO Color Filters reticule-eyepiece
 Celestron 9.25″ on CGEM Zhumell SCT Dual Speed Focuser TeleVue 2.5x Powermate 1-1/4 Inch Rigel QuikFinder Compact Reflex Site
cgem-asi120mm Zhumell Focuser Televue Powermate Rigel Quikfinder

Here is an image showing how the components of the optical train are attached. Click on image to see it full size.

Scope Setup with ASI120mm

Basic Method for Capturing Jupiter with ZWO’s ASI120MM

Here are the overall steps I took to image Jupiter. The telescope used was a 9.25″ Celestron SCT on CGEM mount.

1. First I balanced my optical tube with the ASI120MM installed. Adjustments were made to the counterweights and optical tube position in the saddle to get everything in perfect balance. This helps minimize the stress on the mount’s gears while tracking and allows smooth operation of the scope.

2. Next I removed the ASI120MM and inserted an Orion 12mm Illuminated reticule eyepiece and performed a good drift alignment. This is important for keeping the planet in the field of view (i.e. on the computer screen) while taking the video of it.

3. After the drift alignment, I collimated the SCT. Optical alignment is super important when imaging the planets. I started out with the ASI120MM installed so I could see the defocused star on the screen (using Firecapture software. More on this later). I tweaked the 3 adjustment screws for the secondary mirror until the shadow of the secondary mirror was centered as good as I could get it. Then I removed the ASI120MM and inserted a 25mm eyepiece to fine tune it. The eyepiece provided a crisper view of the defocused star. Next time I’ll probably just use the eyepiece.

4. Since Jupiter is bright and easy to find, I didn’t bother with goto. I slewed the scope to Jupiter and centered it in the eyepiece. Once centered, I removed the eyepiece and inserted the ASI120MM / color filter wheel into the eyepiece holder.

5. Now it was time to focus. Jupiter was very much out of focus so I adjusted the SCT focusing knob to get it close. Since this causes image shift, I had to keep re-centering Jupiter after making small adjustments. But then I was able to use my Zhumell SCT Dual Speed Focuser which is nice for making fine adjustments. Plus, it’s a zero image-shift type of focuser so there was no need to re-center Jupiter after focusing. I spent a LOT of time trying to get the focus a good as possible.

6. Once I got Jupiter focused, it was finally time to capture some video! This was done using FireCapture software which is a nice program with lots of features. FireCapture free download here. Screenshot of FireCapture:


7. Since the ASI120MM is a monochrome camera (rather than a color camera), the videos must be taken through Red, Green, and Blue (RGB) color filters. The videos of each color are combined later to obtain a color image. More on this in the processing section below. With FireCapture, you select the filter (from the drop down menu) for the color you are about to image through. This was the first thing I set in FireCapture.

8. Next, I selected the resolution, gain, exposure time (Exp. ms), and gamma for the red channel. Then, I selected the recording time for the video of 60 seconds. Since Jupiter has a very short rotational period, the total time (for recording all three color channels) shouldn’t go much past three minutes. Thus, I selected 60 second videos for each color channel. I took several videos of Jupiter using different settings to see which combinations turned out the best. Below are the settings for the videos (of each color channel) that were used for my best photo from that night. Note that these are not necessarily the best settings since I didn’t have a lot of experience with the camera. In fact, I figured out during the wavelet processing in Registax that the gain for the green channel should have been higher. It produced a bad “onion ring” effect which I couldn’t remove. This limited the amount of detail I could bring out in the green channel. The gain should probably be closer to 50 from what I have read.

  Red Green Blue
Resolution  512 X 440  512 X 440  512 X 440
 Gain  41  19  58
 Exposure Time (ms)  13.65  12.49  5.0
 FPS  72  79  111
 Gamma  26  60  52
 Video Duration (sec)  60  60  60


9. Now it was time to capture the AVI video. I made sure the red filter was selected in the color filter wheel and also re-centered Jupiter in the field of view on the computer screen. Then I recorded the 60-second video. This process was repeated for the green and blue filter.

This was the method I used to capture the videos with the ASI120MM. It was quite exciting to see Jupiter looking so clear on the screen! It helped that the seeing was better than normal. The stars were hardly twinkling that night which was a good sign of a very stable atmosphere. I remember thinking that I needed to take advantage of the clear skies. It was hard to pack it up for the night. In fact, I stayed up until 4:00am taking my last video for the session!

Basic Processing Method

I processed the AVI’s in Registax 6 and then PhotoShop CS3. Fortunately, I found an excellent video tutorial produced by David Rankin of Rankin Studio for complete processing of Jupiter. David has produced superb images of Jupiter with the ASI120mm. Click here to view his astrophotography gallery which includes Jupiter and number of other solar system photos as well as deep space work. Thank you David for letting me use your video tutorial in this article! I followed this video very closely for processing Jupiter in Registax and PhotoShop.


ASI120MM Conclusion

I am very excited about the potential with the ASI120MM! I continue to see outstanding work posted by other imagers who are using this camera. I know I need more time with it to perfect my methods, but my goal is to produce images that are close to the spectacular work of others. I know it’s achievable based on my second session with the camera. I plan to share my experience as I go along and at some point, post a more thorough review. I hope this article is useful and please feel free to provide feedback in the comments section below.


  1. David Bleser

    I’m getting the camera and will be needing a laptop pc to run it. What type of laptop do you have and is it fast enough for the photography?

    1. AstroPhotography Tonight

      Hi David- the ASI120MM is a great choice. The laptop I’m using is an older Compaq Presario CQ60-215DX- AMD Athlon X2 Dual-Core 2.0GHz. It has worked fine so far even at full resolution. Ray Shore

      1. Hey don’t buy that laptop. I fix laptops for a living and that laptop is the one I repair the most !
        You just need a laptop with an ssd hard disk and at least 6 gigs of ram 8 gigs would be great. If you use a laptop with the asi200mm the laptop may freeze especially when processing in registax. Dell or Packard bell are good brands that do not break very often. Perfect skies…

  2. Don Sudduth


    Forgive my newbie question since I haven’t imaged before but, you mention in step 4 that you removed the eyepiece and inserted the ASI120MM. In step 5 you mention focusing with the ASI in the eyepiece holder. How do you focus? What are you looking at to get clear focus – the computer screen?


    – Don

    1. AstroPhotography Tonight

      Hi Don,
      Basically, I was focusing the telescope with either the focusing knob or my new Zhumell Dual Speed Focuser that is installed at the rear of the telescope. While turning the focusing knobs, I was watching the live view of Jupiter on the computer screen. I kept tweaking the focus until the detail on Jupiter was a sharp as possible overall. Once I was happy with the focus, then I captured the videos with the ASI120MM. I hope this helps. Please let me know if you have any other questions. Thanks, Ray Shore

  3. David Preneta

    Hello Don,

    Thanks for this review and tutorial it’s extremely helpful. I currently use this camera and FireCapture with a Celestron C8 on a AVX mount with a JMI focuser and motofocus and have a few questions. First of all while using the most current version of Firecapture I sometimes freeze up…have you had any issues with this? I’ve done some research online but really haven’t The computer freezing usually happens after adjusting the ROI. I’ve done some research online but really haven’t found any solid solutions. I have also used SharpCap which works well but I prefer using FireCapture.

    Secondly what are your thoughts on the ZWO filter wheel and filters? Is rotation smooth or does rotating the filter wheel really cause a lot of telescope vibration…or knock the camera out of focus or centering on the object? Have you noticed any light leaks through the filter body opening? And have you tried other more expensive brands of LRGB filters? These are about the least expensive filters I have seen and wonder what the difference is among these and Baader or Orion filters costing 3x as much? I am interested in the filter wheel and filters but haven’t seen any other good reviews.



    1. AstroPhotography Tonight

      Hello David,

      Thanks for the feedback on my ASI1200mm tutorial. I hope to expand on it someday if I ever get a chance to get back out with it! Actually, Firecapture did freeze up a couple of times on me. I can’t remember when it happened during the process though. I’ll have to look into it to see what I can figure out. Hopefully we can find a solution because Firecapture is a very nice program.

      The ASI120mm is the first monochrome camera I’ve used so I don’t have anything to compare the filter wheel and filters to. But it does seem fairly smooth to me. While changing the filters a couple of times, Jupiter moved away from the center of the field of view just a bit. It wasn’t enough to readjust though. I do remember thinking it would be nice to have an electric one! That would cost a lot more. I didn’t notice any light leaks. I wish I could provide a better review of the ZWO filter wheel and filters. To me, it seems adequate and I think if I get favorable sky conditions again, I can turn out a better image of Jupiter than the one in my tutorial. I hope this helps!

      Ray Shore

      1. David Preneta

        Thanks for the reply Ray. I will do some additional research on the FireCapture freezing issue as well and post any good information I find. I think I will try the ZWO filter wheel and filter set…it sounds like it’s a decent deal at $176.00 for both of them. I don’t think a bit of image shift now and then is a enough to make me think twice about the purchase. As far as electric filter wheels I was looking at the Xagyl Communications 5 position filter wheel. The filter wheel cost is about $250.00 and another $50.00 for their filter set. I know there seems to be an issue with mixing different filter wheels and filters so the set is probable the way to go. Here are two reviews from Cloudy Nights… and Thanks again….David

        1. AstroPhotography Tonight

          Thanks for researching the FireCapture freezing issue. I hope we can find the cause. That’s what I was thinking when I bought the ZWO filter wheel and filters. I didn’t want to chance a compatibility issue. Thanks for providing the reviews!
          Ray Shore

  4. Hi Ray;
    Very nice review. Question: you show a Televue Powermate in your “equipment used” section. Can you describe your optical train? In other words do you have the Powermate inserted directly into the telescope then the filterwheel/camera attached to the Powermate? If you could describe the arrangement that would be great.


    1. AstroPhotography Tonight

      Hi Bruce,
      Thanks for your feedback on my ASI120MM article. Here is how everything is connected. The Zhumell SCT Dual Speed Focuser is attached to the visual back of the SCT. The TeleVue 2.5x Powermate attaches to the Zhumell focuser. The ZWO Color Filter Wheel connects to the Powermate and the ASI120MM camera attaches to the filter wheel. I inserted a new image in my article showing the components of the optical train which should help :-). Here is a direct link to the full size image: I hope this helps.
      Thanks, Ray Shore

  5. Hi Ray – Thanks for the reply and the photo of your image train. That’s exactly what I need to know. I was confused because I was under the assumption that the camera or eyepiece, depending on what was being used, had to be inserted directly into the Powermate (or barlow) but I see I was mistaken.

    Thanks for clearing this up.


    1. AstroPhotography Tonight

      You’re most welcome Bruce. I’m glad I could help! Ray Shore

  6. It’s important to note that aperture is key to high frame rates on this camera.

    I have been using a 5″ apo refractor for planetary imaging (a departure from the current planetary imaging wisdom) and have had great results with a Canon T3i and BackyardEOS. My results were less than impressive with the ZWO ASI120MC on this particular scope. The exposure needed on a 5″ refractor limits the frame rate to about 12 per second. With the T3i and Backyard EOS in planetary mode, I consistently get 30 fps (about the max for this setup) at 1024X680.

    However, it was a completely different story with the ZWO ASI120MC on my C9.25 with just under 60 fps on Saturn and just under 50 fps on Jupiter.

    Aperture makes a huge difference with this line of cameras. Something to consider if you’re looking at buying one of the ZWO cameras.

    1. AstroPhotography Tonight

      Hi Steve,

      Thanks for the info related to aperture. Now I wonder how well my ZWO ASI120MM will work on the Meade 6″ SCT I have coming. I bought the Ioptron ZEQ25GT awhile back and tried my 9.25″ SCT on it. The scope seemed way too big for the mount! So I ordered the smaller 6″ SCT to use with the ZEQ25GT and ASI120MM. I’ll be trying it out soon!


      Ray Shore

  7. I am confused by the resolution issue. I have a Celestron SE8, and a neximage 5. My results are consistently less clear than most others I see.
    My questions are,
    1. A lot of people use a barlow, when I use barlow with the NI5, at 640×480 the image of jupiter is so faint and so fuzzy that it seems pointless. Is the barlow use related to the megapixels of your camera? ie, seems the zwo with 1.2 megapixels always use a barlow, the NI5 has 5 megapixels and so doesn’t seem necessary?
    2. Everyone shoots with 640×480 – the lowest resolution? Wouldn’t it be better to shoot with higher resolution? ( i realise the frame rate lowers as the resolution increases)
    3. Based on the images i’ve seen with the ZWO I am thinking of buying one, but I do not understand how a 1.2 mpx camera can outperform a 5 mpx one?

    Thanks, hope someone can answer me.!

    1. Hello Greg,

      Key point *In order to capture sufficient detail of a planet the disk of the planet must cover as much of the imaging chip as possible, yet our image should not be so large that it slows our FPS down. We must image at a fast enough frame rate to grab as many good images as we can based upon seeing conditions.

      The larger the image size is the slower the FPS we will be able to achieve. We want to capture as many images as we can before the planet rotates enough to cause blur in the image. Download time of the image from the camera is one important consideration. We will come back to this in a bit.

      The single most important aspect is seeing conditions. The optimal image scale we use during average seeing conditions is 0.25″ per pixel. In the best of skies, which I would not even shoot for an image scale of 0.1″ per pixel would be used. Personally, I would never even consider using that number, a more realistic number would be around 0.18″ or 0.20″ per pixel during the best seeing conditions.

      Jupiter which is the largest of planets at opposition covers only 45″ this equates to about 180 pixels at the recommended image scale of .25″per pixel for average viewing conditions. As you can see Jupiter even at it’s closest approach to us is very small.

      The apparent size for several common planets to image in best case scenario are listed here:

      Jupiter covers 45″
      Saturn covers 21″
      Mars covers about 25″

      We have to calculate what focal length we need to be at to obtain the recommended image scale of .25″ per pixel during average seeing conditions.

      The formula for required focal length is:
      Pixel size of camera in microns X 825= Recommended FL

      The typical webcam has a pixel size of about 5.6 microns.

      5.6 microns X 825= recommended focal length of about 4600mm.

      For this example I will use my 8 inch SCT with a native Focal Length of 2032mm. My webcam or planetary cam has the 5.6 micron pixel size we used from formula above. I now know that for average seeings conditions I want to image at an image scale of .25″ per pixel. In my case I need to extend my Focal Length to about 4600mm.

      4600mm/ 2032mm= 2.2X So I now know to achieve best results during average seeing conditions I would need a Barlow which is 2x or 2.5x to achieve optimum results during average seeing conditions. This would get me close to the recommended Focal Length I require of 4600mm.

      In the best of skies which is extremely rare I would be lucky to shoot for an image scale of 0.1″ per pixel. The Formula for this image scale to find out required focal length is:

      Pixel size * 2060= Recommended Focal Length for this image scale of 0.1″per pixel.

      In this case above using the typical webcam pixel size of 5.6 microns X 2060= Recommended FL of 11,500mm. I can do the numbers real quick in my head on my 8 inch scope with a 5x Barlow. I am imaging at f/50 and a focal length of about 10,100mm. The skies will never be this good and I still am not close to where I need to be. This shows us why a native long focal length scope is recommended for planetary work. It is much easier with a very long focal length scope to reach the recommended focal length using barlows. The downside is the size of the scope you would be lugging around.

      The average recommended image scale of .25″ per pixel is a great starting number. Realistically, on best of nights I would use an image scale of between 0.15″ and 0.20″ per pixel during best of seeing conditions on those very rare nights. Now we must know the formula to calculate for a variety of image scales.

      To calculate out the formula for image scale:

      206/FL = arc secs per micron

      (Pixel size X 206)/FL = resolution in arc secs per pixel.

      Knowing this we can now solve using the following formula:

      FL = (Pixel Size x 206)/res. in arc secs per pixel

      *where FL is my recommended focal Length

      Using same numbers and solving for seeing conditions which are a bit better than average, we will use 0.20″ per pixel we get:

      FL= (5.6 * 206)/0.20″per pixel
      FL= 1153.6/0.20″ per pixel

      Recommended FL = 5768mm in this case.

      My scope is 2032 FL so I now need to know what I should use for a barlow.

      5768/2032= 2.8x

      So in this case I would most likely choose a 3x barlow.

      Now we need to get back to download time of the image, image size and planet rotation.

      We have learned that even during the best of times that the diameter of a large planet even Jupiter covers very little area of an imaging chip. We know we want to capture as many frames as we can and as fast as possible so that we have enough clear images in our video to choose from so that we can have a pretty final product. We also have learned that during average seeing conditions an image scale of 0.25″ per pixel is ideal. Small pixels are better, larger pixels if you do the math require an extremely long focal length scope. Larger file size is not a good thing because it slows down our FPS and due to the small size of planets we do not require a huge chip to fit an image of a planet. This is why when imaging with a ccd or DSLR we choose to image with a smaller subframe. This keeps the FPS rate up high and leaves us plenty of room to fit the planet onto image space.
      We now need to consider one last factor which I started talking about in the beginning, image blur and planet rotation.

      Jupiter at opposition is only 45″ in size.

      Time for each of these planets at opposition to rotate .25″

      Jupiter= 60 seconds.
      Mars= 280 seconds
      Saturn=150 seconds

      I hope this was helpful.

      Best Regards,

      Jeff Turner
      aka “DaltonSkyGazer”

      1. Henri-Julien Chartrand

        WOW! This is useful information and food for my brain at the same time. Thanks to you, I learned a ton more than just reading those instructions manuals. Manufacturers should hire a guy like you. to rethink those manuals. A review and tutorial like this are priceless. And thank you for sharing your experience and how to’s. Respectfully, HJ (Montreal)

        1. I GET IT NOW!! I have just managed to get my head around this and after reading this article it confirms that for my f9 ED100 refractor a 3.75 micron camera is probably better for me than a 5.86 micron camera. For the larger pixel I would need a barlow approaching 6, or given the smaller aperture would the larger pixel be better? I would really appreciate your thoughts on this?

          Yours Sincerely

  8. Sid Cormier

    I recently bought a ZWOASI120MC based on good images I had seen. I seem to have a problem, right now I have the camera mount on my piggy back Orion 80mm short tube refractor. When I take an image I get a lot of hot pixels. With the cap on and a 20second exposure the screen fills with different color hot pixels. Am I doing some thing wrong, do you experience hot pixels and if so how do you deal with the issue?
    Is ASI120MC the same as FireCapture. I have downloaded FireCapture twice and it does not show up in my list of programs, only ASI120MC, and when I click on this I get a screen with “AMcap” on top. I also use SharpCap2 and get the same results, hot pixels.
    I need some help because the camera as is, is useless to me.


    1. AstroPhotography Tonight

      Hi Sid,

      I haven’t done any long exposures with my ASI120mm yet but it sounds like an issue with thermal noise. These cameras have CMOS sensors which are more prone to thermal noise than CCD sensors. The longer your exposures are and the warmer it is outdoors, the more noise you’re going to encounter. You might try subtracting a lot of dark frames from the light frames which should help. One thing about these cameras, they excel at planetary imaging which involves exposures of a fraction of a second thus limiting the amount of noise. But they are not cooled so the noise can be quite a factor with long exposures.

      I hope this helps.

      Regards, Ray Shore

  9. Sid Cormiers

    Is ASI120MC the same as FireCapture. I have downloaded FireCapture twice and it does not show up in my list of programs, only ASI120MC, and when I click on this I get a screen with “AMcap” on top.


    1. AstroPhotography Tonight

      You should be able to use FireCapture for imaging with the ASI120MC. It’s the only one I’ve used so far. Not sure why it’s not showing up in your list of programs though.

  10. Hi Ray,

    Did you consider a flip-mirror arrangement with a cross-hair eyepiece on top to viewing/centering in order to avoid switching eyepiece & camera?

    1. AstroPhotography Tonight

      Hi Tom,

      I didn’t think about this. Are you doing it this way?

      Thanks, Ray Shore

  11. I’m returning the color version of this camera. I loved how you wrote How you centered Jupiter in the eyepiece and began focusing. I have had a terrible time trying to get an image to come up on my computer (center on the chip). Seems a couple times I just got lucky and was able to take some wretched photos of Mars and Saturn, but getting the image to come up on my monitor was worth a week of frustration at work, and this is supposed to be fun. Seeing was bad, but the worst part was the complete lack of color. Both planets showed only shades of gray regardless of the adjustments I made.
    The stakker program that came with the camera did not work on my 1 year old computer (PC). The directions for the camera itself were lacking much detail at all. Very disappointed. Anyone have an old Meade LPI they want to sell? It was a superior camera.

    1. AstroPhotography Tonight

      I know what you mean! AstroPhotography can sure be frustrating at times. Trying to get a planet centered on the screen and in focus is one of the most challenging parts to planetary imaging in my experience. It took me awhile the other night to get Saturn to show up on my screen with the ASI120mm. I knew it was a matter of it being way out of focus because Saturn was perfectly centered with the reticule eyepiece. A couple of things helped. First, I removed the ASI120mm and inserted my 2.5x Teleview Powermate and I believe a 12mm eyepiece. I focused on Saturn (and recentered) then switched back to the ASI120mm. Then I turned up the gain real high to detect the faint blurry disk of Saturn. Then I focused it. I need to find a good eyepiece that will be closer to the focus of the ASI120mm though. Ray Shore

    2. I had the same issue with the asi120mc and firecapture. The image was always in greyscale and it had an odd grid like pattern in it. After some research I found that this was normal. Fire capture does no do debayering as it captured data from the sensor so that it can run at higher fps.

      What you have to do is record the video then in the directory with firecapture.exe look for a file called Debayer.exe. Run this select the video, click the start button and it will generate a new video in color without the odd grid pattern.

  12. Hi Ray, congratulations for your excellent information. It is very clear and very helpful. Besides it has been very useful for finally deciding upgrading from the original NexImage to ZWO ASI 120, I understood I don’t need to buy a 5x powermate as I was considering, for my 2032 mm SC nor my 1500 mm XX12g for best imaging. Clear skys and many thanks!!!

    1. AstroPhotography Tonight

      Hi Juan,

      Thanks and congrats on obtaining the ZWO ASI120 camera! You will move to a new level in astrophotography of the planets!

      Clear Skies!
      Ray Shore

  13. Hi, Thanks for the fantactic writeup!

    I am using a Celestron Nextar 6 SE and the ZWO Asi120MC (colour) with built in IR filter.
    I am using a Dew sheild, i am using Goto to track.
    Revelations x2.5 barlow.

    I find that i’m getting very fuzzy images, are there any underlying setting that should be checked to help sharpen/enhance the image?
    I am using 640×480 RES.
    Is there a minimum/maximum for gain and exposure? as you can balance the “brightness” with either but im sure there is an advantage to favour one or the other?

    I find that sharpcap gives me better recordings than firecap, however, i believe firecap is a better app as it allows more control.

    I believe i am getting pretty good focus, the telescope is pretty new, so i believe its in fair colomation, maybe i should re-colomate.

    Thanks in advance

  14. A quick question on centering. Do you put your eyepiece directly into the focuser, or use a diagonal at this stage? Trying to centre with an eyepiece without a diagonal requires the most extraordinary flexibility, and my knees are sore! Thank you for all the marvellous info BTW.

    1. AstroPhotography Tonight

      Hi Sarah- if I remember correctly, I did use a diagonal at that stage. Ray

  15. Hi, I’m in the early stages of astronomy so it’s all very new to me.

    I have a Celestron NexStar 130 SLT and recently purchased a ZWO ASI120MM Monochrome 1.2 megapixel camera. I’m using SharpCap 2.8 for the editing, etc.

    I’m trying to use the camera to get some pictures of Jupiter, but the problem I’m having is Jupiter is all bright white on my computer screen. It’s moons show up fine and the image of the planet itself is clear, just all bright white. I can see normally see those classic red lines on Jupiter when looking through a 1.25″ lens with my bare eye, so I was hoping/expecting the same thing, if not better when using the camera. I have a color filter set of R,G,B,Y. Should I use these, and should I use my Barlow lens also? Because I wasn’t using anything but the camera itself. No Barlow lens, no color lenses. Perhaps some adjustments in SharpCap? I played with the brightness and some other simple adjustments on there, but nothing seemed to bring out any detail of Jupiter, it’s just a bright white-ish circle, no detail at all..

    Any help would be appreciated. I figured I’d ask someone that knows what they’re doing before I started messing around aimlessly.


  16. Hi, I’d like to buy the ASI 120MM or the 120MC (colour version) simply to use it as All Skay cam. I think that the exposure time will be need between 60 and 120 seconds because the monochrome version is more sensitive than colour version.
    The doubt is if the colour version is better than monocrhome for this type of use. Any advice will be welcome.
    Thanks, Daniele

  17. Hi, thank you for this great tutorial. I have an ASI224 MC, color camera, i’m not sure i’ll have the same quality image like you with a monochrome camera but i’ll follow your recommandations (except those for color filters) and i hope to get good images like yours.
    Clear skies 🙂

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