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Old 08-03-2020, 12:42 PM
kimrichards (Kim)
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Need some advice on which ZWO camera for planetary imaging

Hi,

I have a C14 that I use part of the time for planetary imaging mostly Mars, Jupiter and Saturn with a 2x Powermate and a ASI120MC camera.

I would like to improve the quality of my imaging and am considering the following cameras.

ASI290MM or MC or an ASI385MC.

Can anyone help me decide?

1. The Color option:
The 385 has the same pixel size as the 120 at 3.75 so still would be sampling at roughly 0.1 arcsec/pixel. Would the more sensitive sensor and faster frame rate of the 385 help. For example would 2x binning help.

2. Mono option:
It seems generally accepted that a mono camera with color and UV/IR filters is superior to a color camera. However is it a significant jump in quality?
How much does the need to de-rotate the filter sets individually degrade the image?
If I go with the ASI290MM the pixel size drops to 2.9 and sampling is down to .08 arcsec/pixel so would probably bin to reduce the oversampling. At 2x binning that puts it at almost exactly 1/2 my Dawes limit of 0.33.

The color option is obviously the easiest and cheapest but am willing to go to mono if I am really going to see an improvement.
Thanks for any advice

Kim
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Old 08-03-2020, 10:50 PM
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Camelopardalis (Dunk)
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Kim, it’s a tricky one, as I’m sure you appreciate.

There are so many factors involved that are beyond our control. The biggest wildcard is undoubtedly the weather.

If you’re unhappy with the results you’re getting from the 120, a new camera may not solve the problem.

One thing I would try, given your focal length with the Powermate, would be to try it without, and perhaps with a different Barlow multiplier...say 1.5x? It could be that the atmosphere just isn’t giving you what you want, and reducing the effective focal length might give you more promising results.
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Old 23-03-2020, 12:35 PM
kimrichards (Kim)
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ZWO camera choice

Hi Dunk,
Thanks for the reply. You are undoubtedly correct about seeing being the biggest issue.
My thinking was a more sensitive sensor would enable a faster frame rate so less atmospheric effect and more frames to pick from.

Any thoughts on color v mono?

Cheers

Kim
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Old 23-03-2020, 02:14 PM
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Camelopardalis (Dunk)
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Kim, the 385 (and 224) have comparable sensitivity to the 290. The former are available in colour only, and the latter mono or colour. They're both great sensors, so it's kind of a rock and hard place situation.

It's possible you may see better colour resolution with the mono (+ filter wheel) setup because each pixel has real colour information collected, whereas with the OSC the colour is interpolated in a cluster of 4 pixels because of the Bayer array, but the (typically) high number of captured frames being stacked on top of each other really makes that a bit of a non-issue.

In practice it's really hard to objectively compare, since we'd perfect and stable conditions to be able to switch them out and run a capture.

Both 385/224 and the 290 are capable of some pretty phenomenal frame rates, it's just that with the mono you need to capture data using each filter separately. This changes the processing required. I'm not going to say one way is easier or harder, they're just different techniques.

Pushing efforts of objectivity/neutrality aside, I'd expect that the 290 mono at your native focal length would be pretty impressive all by itself as you'd get lots of light throughput that would give good signal even at high frame rates. On exceptionally good nights, you can always drop in-line a mild Barlow.
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Old 23-03-2020, 03:36 PM
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My 2 cents worth.

I think it's well established that under the same conditions and the same system, the mono camera will be superior to a colour camera.

Don't worry about the pixel size element so much - it's not like deep sky because you will change the FPS and Gain settings to suit the object.

A more important consideration is the effective F ratio you will end up with and the FPS that the camera can generate. The faster the camera in FPS the better!

Most planetary guys imaging with a C14 are using a 290mm or equivalent camera and a 2.5x Barlow - surf the web and have a look - the ALPO website is a good area to investigate.

If you have already been doing colour planetary work, go the next level to a mono - once you make the jump there's no going back once you see the results!

Clear skies.

John Kazanas.

Last edited by John K; 23-03-2020 at 04:12 PM.
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Old 23-03-2020, 11:18 PM
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Hi there, I use an ASI224MC exclusively for planetary, it's probably the best bang-for-buck colour camera out there, and still used by C14 owners. As John says, the ASI290MM is probably the most commonly used mono camera for planetary and while I'm sure it will produce a better result, it's a lot more effort to capture and process the images. Motorised filter wheels, 3 video captures required instead of 1, more processing to de-rotate and combine them together, etc.

Is it worth the extra effort? Have a look at Darryl's (aka Kokatha Man) website, he uses both the 224MC and 290MM to good effect.

http://www.momilika.net/WebPages/AstroIntro.htm

Andrew
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Old 24-03-2020, 11:54 AM
kimrichards (Kim)
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ZWO camera choice

Thanks to everyone for all the input.

I am leaning towards the ASI290MM for the following reasons.

- I am not worried about the extra processing time.
- Generally accepted that mono is better.
- I can add a fourth filter.
- Fastest frame rate
- Binning 2x would keep me just below 1/2 the Dawes limit

I am still a bit concerned about the "now needed" de-rotation being detrimental but presume that has been accounted for in "Generally accepted that mono is better."
Thanks again
Kim
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Old 24-03-2020, 12:35 PM
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Quote:
Originally Posted by kimrichards View Post
Thanks to everyone for all the input.

I am leaning towards the ASI290MM for the following reasons.

- I am not worried about the extra processing time.
- Generally accepted that mono is better.
- I can add a fourth filter.
- Fastest frame rate
- Binning 2x would keep me just below 1/2 the Dawes limit

I am still a bit concerned about the "now needed" de-rotation being detrimental but presume that has been accounted for in "Generally accepted that mono is better."
Thanks again
Kim
Hi Kim,

No need to Bin or worry about the Dawes limit with planetary.

Below are my settings when I imaged Mercury last week. As you can see I am imaging at double the dawes limit for a 12" scope. Results attached.

FireCapture v2.6 Settings
------------------------------------
Camera=ZWO ASI290MM
Filter=IR685
Profile=Mercury
Resolution=0.25"
Filename=2020-03-15-2006_2-IR685-Mercury.ser
Date=150320
Start=200519.690
Mid=200616.492
End=200713.295
Start(UT)=200519.690
Mid(UT)=200616.492
End(UT)=200713.295
Duration=113.605s
Date_format=ddMMyy
Time_format=HHmmss
LT=UT +10h
Frames captured=16427
File type=SER
Binning=no
ROI=584x534
ROI(Offset)=624x328
FPS (avg.)=144
Shutter=6.916ms
Gain=359 (59%)
AutoGain=off
Brightness=1
AutoHisto=75 (off)
HighSpeed=on
USBTraffic=85
SoftwareGain=10 (off)
Gamma=0 (off)
AutoExposure=off
FPS=100 (off)
Histogramm(min)=1
Histogramm(max)=248
Histogramm=97%
Noise(avg.deviation)=5.90
Limit=none
Sensor temperature=18.7C
Attached Thumbnails
Click for full-size image (Web Image Mercury.jpg)
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