Suitable camera for planetary & guiding purpose

[Gaurav Mk]

I own a Skywatcher 200PDS with EQ5 mount(not a goto mount, but has motors installed with a controller that has auto guiding port) and currently I am using a Nikon D5300 camera for capturing images through it.

I intend to buy an astronomy camera from ZWO ASI within a budget of 400$ with the following requirements-

1. For planetary imaging. I would prefer going a colour camera as using a mono with filters would be a little tough for me. 

2. Biggest motivation to buy is for auto guiding. I see that mono cameras are best for this. But I was wondering if i could get it done with a colour camera and as to how effective will be the guiding with colour camera? 

Autoguiding is to aid long exposure DSO imaging, as currently I am able to get only 30-60sec subs. So autoguiding port is a must.

3. Given my SW 200PDS has D=200mm & f=1000mm and I also own a 2x Barlow that can be used if required, I would prefer that the sensor size of camera be apt for the best sampling. The sky here gives about 0.5 to 1 arc sec viewing conditions.

These 3 are my primary requirements while a high fps camera that could help get ISS transits is a plus point. 

I have narrowed the options to 178MC & 290MC. It would be helpful if you could suggest which one of the two would be best fit for my 3 requirements

Edited November 7, 2021 by Gaurav Mk

[Ags]

ZWO also have a new camera you might consider:

https://www.firstlightoptics.com/zwo-cameras/zwo-asi-485mc-usb-30-colour-camera.html

The sensor is twice as large as the 178MC. 

I have my eye on this camera but I am waiting for more reviews.

[barbulo]

4 hours ago, Gaurav Mk said:

I have narrowed the options to 178MC & 290MC.

And why not the ASI224MC or the ASI462MC (evolution of the 290)?
What you want for planetary is a high capture speed ("lucky imaging" is the technique), so 244 or 462 should be your targets (290 is discontinued but you may find some stock out there).

4 hours ago, Gaurav Mk said:

sensor size of camera be apt for the best sampling

As far as I know, the sampling rate is determined by the pixel size not by the sensor size. Bigger pixels = higher sampling rates. Besides, higher resolutions = bigger/heavier images = lower capture speeds.

4 hours ago, Gaurav Mk said:

So autoguiding port is a must.

Although all of the above have ST4 ports, you can use the camera for guiding using its USB port: camera -> computer -> mount. IMHO it is the best configuration since you will have one less cable. Using the ST4 you would have the same connections as before plus the camera->mount (ST4).

Hope This Helps

[johninderby]

The ZWO ASI 290 MC is discontinued but the 290 MM is still available.

Edited November 7, 2021 by johninderby

[barbulo]

38 minutes ago, johninderby said:

The ZWO ASI 290 MC is discontinued but the 290 MM is still available.

Correct, but the OP is looking for a color camera.

[vlaiv]

For planetary imaging you want camera with highest QE and lowest read noise.

Pixel size is not that important as you can actually vary amplification given by barlow - by changing the distance from barlow element to sensor - more distance, greater amplification.

You say you have F/5 scope and x2 barlow. This gives F/10 setup.

2.4µm pixel camera needs ~F/9.4

2.9µm pixel camera needs ~F/11.4

3.75µm pixel camera needs ~F/14.7

They are really all quite close. For 3.75µm pixel camera you should really get x3 barlow, but other two are quite close and placing element closer or further away will get you there.

Mind you - with regular barlow it is easier to get higher magnification as it is easier to move sensor further away - just pull it out a bit or add small extension. If you have barlow with removable barlow element - then it is just the matter of getting required distance with extenders.

As far as guiding goes - you'll have no trouble guiding with color camera. I do it all the time and it just works. Maybe mono cameras have slight edge there - but I've used my ASI185 with OAG and haven't had issues with it.

If you plan to use OAG - then larger chip would be waste of chip size - because neither do planets need large chip - nor OAG can illuminate one. OAG prism is 8mm and depending on distance, full illumination can be as small as 3-4mm.

If you plan on imaging the moon and to use guide scope - then yes, look into larger sensor, but be aware - your F/5 newtonian won't have very large coma free field.

On F/5 scope, coma free zone is ~2.8mm in diameter. If you add x2 barlow to that, you get 5.6mm diameter. All sensor in the table above have larger diagonal.

Larger sensor will help with guiding as it will allow you to pick more stars (multi star guiding with PHD2 and finding suitable guide star in general).

ASI224 or ASI485 would be my choice, with ASI485 as preference as it opens up more options (like larger FOV with scope that is capable of it or some DSO imaging with fast lens as it has bigger sensor size). With ASI224 - consider that you might need x3 barlow if your current one proves not too good at x3 amplification.

 

[Gaurav Mk]

6 hours ago, barbulo said:

And why not the ASI224MC or the ASI462MC (evolution of the 290)?
What you want for planetary is a high capture speed ("lucky imaging" is the technique), so 244 or 462 should be your targets (290 is discontinued but you may find some stock out there).

As far as I know, the sampling rate is determined by the pixel size not by the sensor size. Bigger pixels = higher sampling rates. Besides, higher resolutions = bigger/heavier images = lower capture speeds.

Although all of the above have ST4 ports, you can use the camera for guiding using its USB port: camera -> computer -> mount. IMHO it is the best configuration since you will have one less cable. Using the ST4 you would have the same connections as before plus the camera->mount (ST4).

Hope This Helps

Yeah that makes sense. The other two options you suggested seem to better. I had some bias towards 224 n 462 because of something I had read, but I feel I need to reconsider. 

And yeah, I meant pixel size. Not the sensor size. Thanks for the correction. 

Thankyou for your suggestion 

[Gaurav Mk]

5 hours ago, vlaiv said:

For planetary imaging you want camera with highest QE and lowest read noise.

Pixel size is not that important as you can actually vary amplification given by barlow - by changing the distance from barlow element to sensor - more distance, greater amplification.

You say you have F/5 scope and x2 barlow. This gives F/10 setup.

2.4µm pixel camera needs ~F/9.4

2.9µm pixel camera needs ~F/11.4

3.75µm pixel camera needs ~F/14.7

They are really all quite close. For 3.75µm pixel camera you should really get x3 barlow, but other two are quite close and placing element closer or further away will get you there.

Mind you - with regular barlow it is easier to get higher magnification as it is easier to move sensor further away - just pull it out a bit or add small extension. If you have barlow with removable barlow element - then it is just the matter of getting required distance with extenders.

As far as guiding goes - you'll have no trouble guiding with color camera. I do it all the time and it just works. Maybe mono cameras have slight edge there - but I've used my ASI185 with OAG and haven't had issues with it.

If you plan to use OAG - then larger chip would be waste of chip size - because neither do planets need large chip - nor OAG can illuminate one. OAG prism is 8mm and depending on distance, full illumination can be as small as 3-4mm.

If you plan on imaging the moon and to use guide scope - then yes, look into larger sensor, but be aware - your F/5 newtonian won't have very large coma free field.

On F/5 scope, coma free zone is ~2.8mm in diameter. If you add x2 barlow to that, you get 5.6mm diameter. All sensor in the table above have larger diagonal.

Larger sensor will help with guiding as it will allow you to pick more stars (multi star guiding with PHD2 and finding suitable guide star in general).

ASI224 or ASI485 would be my choice, with ASI485 as preference as it opens up more options (like larger FOV with scope that is capable of it or some DSO imaging with fast lens as it has bigger sensor size). With ASI224 - consider that you might need x3 barlow if your current one proves not too good at x3 amplification.

 

This was really helpful. Thanks a lot. I will check about the two options you suggested.

I am gonna do OAG and I was worried about guiding using color camera. So needed to hear it from someone who had used it. 

[Gaurav Mk]

15 hours ago, vlaiv said:

For planetary imaging you want camera with highest QE and lowest read noise.

Pixel size is not that important as you can actually vary amplification given by barlow - by changing the distance from barlow element to sensor - more distance, greater amplification.

You say you have F/5 scope and x2 barlow. This gives F/10 setup.

2.4µm pixel camera needs ~F/9.4

2.9µm pixel camera needs ~F/11.4

3.75µm pixel camera needs ~F/14.7

They are really all quite close. For 3.75µm pixel camera you should really get x3 barlow, but other two are quite close and placing element closer or further away will get you there.

Mind you - with regular barlow it is easier to get higher magnification as it is easier to move sensor further away - just pull it out a bit or add small extension. If you have barlow with removable barlow element - then it is just the matter of getting required distance with extenders.

As far as guiding goes - you'll have no trouble guiding with color camera. I do it all the time and it just works. Maybe mono cameras have slight edge there - but I've used my ASI185 with OAG and haven't had issues with it.

If you plan to use OAG - then larger chip would be waste of chip size - because neither do planets need large chip - nor OAG can illuminate one. OAG prism is 8mm and depending on distance, full illumination can be as small as 3-4mm.

If you plan on imaging the moon and to use guide scope - then yes, look into larger sensor, but be aware - your F/5 newtonian won't have very large coma free field.

On F/5 scope, coma free zone is ~2.8mm in diameter. If you add x2 barlow to that, you get 5.6mm diameter. All sensor in the table above have larger diagonal.

Larger sensor will help with guiding as it will allow you to pick more stars (multi star guiding with PHD2 and finding suitable guide star in general).

ASI224 or ASI485 would be my choice, with ASI485 as preference as it opens up more options (like larger FOV with scope that is capable of it or some DSO imaging with fast lens as it has bigger sensor size). With ASI224 - consider that you might need x3 barlow if your current one proves not too good at x3 amplification.

 

I had two doubts here after going through the specs of the mentioned cameras.

1. ASI485 has low FPS. So wouldn't this be an issue for lucky imaging of planets?

2. What is the reason for choosing ASI 224 over ASI 462?

 

 

[vlaiv]

1 hour ago, Gaurav Mk said:

1. ASI485 has low FPS. So wouldn't this be an issue for lucky imaging of planets?

What you see published is FPS for whole sensor - which is not unreasonable given that you need to download 3840 x 2160 pixels or about 8.3MP.

ASI178 for example has 30 FPS for whole sensor read out - again, that is sensible as it is 6.4MP.

In fact - if you do the math

6.4 / 30 = ~0.21

8.3 / 39 = ~0.21

Same readout rate.

You can however use 8bit readout and / or ROI to achieve high FPS. I have no trouble doing that on ASI178:

above is screen shot of expected FPS based on selected bit mode and ROI.

I believe same to be the true for ASI485 - although ZWO did not publish expected FPS like for every other model (maybe they were in a hurry to release the camera and forgot to measure / update website?), I think it is the same - use ROI - high FPS.

1 hour ago, Gaurav Mk said:

2. What is the reason for choosing ASI 224 over ASI 462?

QE.

You want as high QE as you can get for planetary imaging (well, for all imaging, but particularly for planetary imaging as you are limited in exposure length).

ASI462 has high QE in IR part of the spectrum:

Say that you have absolute QE of about 80-85%.

Green peak in part of spectrum used for normal imaging (not IR) will be about 84% * 85% = 71%.

Half of your pixels will have QE of 71% and blue will be worse still peaking at about 68% * 85% = ~0.50%

ASI462 is surely fine camera, but I would use it if I were interested in IR above 800nm. If not, I think ASI224 will be better (it surely is proven performer).

[Gaurav Mk]

31 minutes ago, vlaiv said:

What you see published is FPS for whole sensor - which is not unreasonable given that you need to download 3840 x 2160 pixels or about 8.3MP.

ASI178 for example has 30 FPS for whole sensor read out - again, that is sensible as it is 6.4MP.

In fact - if you do the math

6.4 / 30 = ~0.21

8.3 / 39 = ~0.21

Same readout rate.

You can however use 8bit readout and / or ROI to achieve high FPS. I have no trouble doing that on ASI178:

above is screen shot of expected FPS based on selected bit mode and ROI.

I believe same to be the true for ASI485 - although ZWO did not publish expected FPS like for every other model (maybe they were in a hurry to release the camera and forgot to measure / update website?), I think it is the same - use ROI - high FPS.

QE.

You want as high QE as you can get for planetary imaging (well, for all imaging, but particularly for planetary imaging as you are limited in exposure length).

ASI462 has high QE in IR part of the spectrum:

Say that you have absolute QE of about 80-85%.

Green peak in part of spectrum used for normal imaging (not IR) will be about 84% * 85% = 71%.

Half of your pixels will have QE of 71% and blue will be worse still peaking at about 68% * 85% = ~0.50%

ASI462 is surely fine camera, but I would use it if I were interested in IR above 800nm. If not, I think ASI224 will be better (it surely is proven performer).

Great. Thanks for taking time out to explain these in detail.

[nfotis]

May I also point out that there's the IMX464 sensor available? (double the pixels of the IMX462, same technology)

Currently, only Player One provides a planetary camera with this sensor, it may be useful to know though.

N.F.

 

[newbie alert]

On 07/11/2021 at 08:42, Ags said:

ZWO also have a new camera you might consider:

https://www.firstlightoptics.com/zwo-cameras/zwo-asi-485mc-usb-30-colour-camera.html

The sensor is twice as large as the 178MC. 

I have my eye on this camera but I am waiting for more reviews.

No point of a large sensor on planets,no plantet is going to fill the frame on even the smallest sensor natively unless you're only imaging the moon

[Ags]

Yes, but for DSOs the extra size is quite useful, and a bigger sensor always helps with the Moon.

Edited November 20, 2021 by Ags

[newbie alert]

5 hours ago, Ags said:

Yes, but for DSOs the extra size is quite useful, and a bigger sensor always helps with the Moon.

For guiding, does it... never had issues picking up guidestars on any system that I use,  inc OAG