ASI178MM

[Lucas Barclay]

Hello all, 

I'm currently looking at some of the ZWO camera's and the 178MM has caught my eye however, I found out the sensitivity of the sensor is much lower compared to the ASI224MC... Yet the resolution and sensor size is much larger on the 178MM. Would the 178MM still be valid for some deep sky imaging? Any other recommendations of cameras by ZWO or other cameras around the price of £200-£400 would be much appreciated!

[CraigT82]

The 178mm is a monochrome sensor and has small 2.4 micron pixels, whilst the 224c is a colour sensor and has larger 3.75 micron pixels. Larger pixels are generally better for DSO imaging as they collect more light, but there are some other factors involved in the choice of pixel size. Do you have filters and a filter wheel? If not you can discount monochrome cameras straight off the bat. Have a look at the ASI385mc

[Lucas Barclay]

12 minutes ago, CraigT82 said:

The 178mm is a monochrome sensor and has small 2.4 micron pixels, whilst the 224c is a colour sensor and has larger 3.75 micron pixels. Larger pixels are generally better for DSO imaging as they collect more light, but there are some other factors involved in the choice of pixel size. Do you have filters and a filter wheel? If not you can discount monochrome cameras straight off the bat. Have a look at the ASI385mc

Oh yes I should have mentioned, I do have access to some coloured filters and considering getting a H-alpha filter soon too.. Those images look very impressive, will have to look into the ASI385mc, looks very interesting.

Thank you for the help!

[tomato]

I use ASI 178 mono cameras on an Esprit 150 exclusively for small galaxy or tight galaxy cluster imaging, as the FOV with this setup is only 0.4 x 0.27 degrees, usually binned 2x2  unless the seeing and guiding are exceptional.

They have significant amp glow on extended exposures (> 2 mins) but this calibrates out OK. They are retro-fitted with Peltier coolers which maintain them at a constant 3 deg C to assist with calibration.

 

[Lucas Barclay]

17 hours ago, tomato said:

I use ASI 178 mono cameras on an Esprit 150 exclusively for small galaxy or tight galaxy cluster imaging, as the FOV with this setup is only 0.4 x 0.27 degrees, usually binned 2x2  unless the seeing and guiding are exceptional.

They have significant amp glow on extended exposures (> 2 mins) but this calibrates out OK. They are retro-fitted with Peltier coolers which maintain them at a constant 3 deg C to assist with calibration.

 

Ah I see, how would you compare it to the ASI385MC? I've heard the resolution is worse but sensitivity is a lot better on the 385, would be interested to see how it compares to the ASI178MM!

[tomato]

I have no experience of the ASI385 MC, I note it has larger pixels than the 178 which will improve the sensitivity, but on the other hand it is available as a colour sensor only so it will suffer on sensitivity when compared to an equivalent mono camera. The FOV is also a bit smaller than the 178. 
 

If you have a filter wheel and filters already its worth considering a mono camera.

[Lucas Barclay]

57 minutes ago, tomato said:

I have no experience of the ASI385 MC, I note it has larger pixels than the 178 which will improve the sensitivity, but on the other hand it is available as a colour sensor only so it will suffer on sensitivity when compared to an equivalent mono camera. The FOV is also a bit smaller than the 178. 
 

If you have a filter wheel and filters already its worth considering a mono camera.

I do have some filters and was hoping to go for a mono camera but sadly the ASI385 doesn't come in a mono option.. Noticing the sensitivity was higher on the 385 I thought it may be a better option to the 178 but I am not exactly sure. Have you tried deep sky imaging on the 178MM? If so could you show me some examples and give your experience? It would be a great help! 

[CraigT82]

12 hours ago, Lucas Barclay said:

I do have some filters and was hoping to go for a mono camera but sadly the ASI385 doesn't come in a mono option.. Noticing the sensitivity was higher on the 385 I thought it may be a better option to the 178 but I am not exactly sure. Have you tried deep sky imaging on the 178MM? If so could you show me some examples and give your experience? It would be a great help! 

Sorry I missed the part earlier where you said you had filters. What filters do you have?  Imaging filters have different properties to visual filters so you would need to use specfic imaging filters with a mono camera. Also a filter wheel is pretty much essential as you really don't want to be taking the camera out and swapping the filters manually in the dark each time you want to switch. 

What other kit to you have? Scope? Mount? What are your skies like in rerms of light pollution? 

Just for info here are a couple of links to astrobin (hopefully the links work and you can see the images without having to log in to astrobin)

This one to an image taken with a 178m camera:

https://www.astrobin.com/n2vxd2/?page=2&nc=user

This one to an image taken with a 385c camera. Note that this this particular user has opted to go for lots of short exposures (3000x 3 seconds).

https://www.astrobin.com/jf24tx/?nc=user

So see that very nice deep sky images are possible with both cameras. Deciding which one is optimal for you requires a bit more info from yourself on your kit and circumstances

[Lucas Barclay]

8 hours ago, CraigT82 said:

Sorry I missed the part earlier where you said you had filters. What filters do you have?  Imaging filters have different properties to visual filters so you would need to use specfic imaging filters with a mono camera. Also a filter wheel is pretty much essential as you really don't want to be taking the camera out and swapping the filters manually in the dark each time you want to switch. 

What other kit to you have? Scope? Mount? What are your skies like in rerms of light pollution? 

Just for info here are a couple of links to astrobin (hopefully the links work and you can see the images without having to log in to astrobin)

This one to an image taken with a 178m camera:

https://www.astrobin.com/n2vxd2/?page=2&nc=user

This one to an image taken with a 385c camera. Note that this this particular user has opted to go for lots of short exposures (3000x 3 seconds).

https://www.astrobin.com/jf24tx/?nc=user

So see that very nice deep sky images are possible with both cameras. Deciding which one is optimal for you requires a bit more info from yourself on your kit and circumstances

Oh! Thank you for the links they are very helpful,

In terms of my equipment I have a Nexstar 5SE with the mount it came with. Granted it may not be the best deep sky telescope. At the moment I have some coloured filters (RGB) however I am looking towards buying a Ha filter for shooting some nebulae. I live around Surrey, the light pollution isn't amazing yet surprisingly I have been able to get some good sights which I was not expecting. A filter wheel does sound like some good equipment to have at hand, Ill have to check that out too..

I imagine my circumstances are more suited for planetary imaging but I would love to hear your take on it. 

Thank you!

[CraigT82]

OK so your scope's FL is 1250mm which is pretty long for DSO imaging. You will also be limited to short exposures as the mount is an Alt Az and so long exposures will suffer from field rotation. 

These factors point you to a large pixel camera, as large as you can get to be honest. The larger pixels will give you a larger pixel scale which will help to hide mount tracking errors and will also gather more light to make most use of the shorter exposures you will be limited to.

If we are talking ZWO then I'd recommend seeing if you could get your hands on a used 174 which would put you at a smidge under 1 arc second per pixel. Be warned though, that you're most likely not going to ever achieve nice tight round stars with this scope and mount. Getting a scope of 1250mm focal length to track precisely enough to produce nice little stars takes quite a meaty mount and some good guiding kit. 

Saying that though you should certainly be able to get some beginner level images of nebula and galaxies to show your friends and family.

Regarding the colour or mono question... if you want to shoot Ha then you will want a mono sensor. You could then add later some S2 and O3 filters and produce nice tri-colour narrowband hubble palette images but the downside is  that narrowband filters let in so little light that long to very long exposures are needed, which your kit isn't likely to manage.

Another option, if your LP isn't too bad, is to get a colour camera and one of the Optolong L-enhance or L-extreme filters, these will let you produce pseudo-narrroband images which are quite attractive and very popular at the minute. 

Considering that your exposures will be limited to short ones, your best bet will likely be taking the kit out to a nice dark site and shooting broadband (i.e. normal colour camera or mono with RGB filters). 

Hope that helps

 

Edit: here is an image of M42 taken with a 5se and a ASI385c, the user doesn't state what the exposure length was.

https://www.astrobin.com/x30krw/?nc=user

Here is another M42 taken with a 5se and a dslr (240x 5 sec exposures)

https://www.astrobin.com/lzv1g9/?nc=user

 

Edited March 23, 2021 by CraigT82

[Lucas Barclay]

22 minutes ago, CraigT82 said:

OK so your scope's FL is 1250mm which is pretty long for DSO imaging. You will also be limited to short exposures as the mount is an Alt Az and so long exposures will suffer from field rotation. 

These factors point you to a large pixel camera, as large as you can get to be honest. The larger pixels will give you a larger pixel scale which will help to hide mount tracking errors and will also gather more light to make most use of the shorter exposures you will be limited to.

If we are talking ZWO then I'd recommend seeing if you could get your hands on a used 174 which would put you at a smidge under 1 arc second per pixel. Be warned though, that you're most likely not going to ever achieve nice tight round stars with this scope and mount. Getting a scope of 1250mm focal length to track precisely enough to produce nice little stars takes quite a meaty mount and some good guiding kit. 

Saying that though you should certainly be able to get some beginner level images of nebula and galaxies to show your friends and family.

Regarding the colour or mono question... if you want to shoot Ha then you will want a mono sensor. You could then add later some S2 and O3 filters and produce nice tri-colour narrowband hubble palette images but the downside is  that narrowband filters let in so little light that long to very long exposures are needed, which your kit isn't likely to manage.

Another option, if your LP isn't too bad, is to get a colour camera and one of the Optolong L-enhance or L-extreme filters, these will let you produce pseudo-narrroband images which are quite attractive and very popular at the minute. 

Considering that your exposures will be limited to short ones, your best bet will likely be taking the kit out to a nice dark site and shooting broadband (i.e. normal colour camera or mono with RGB filters). 

Hope that helps

 

Ah I see that does help quite a bit. I had a little look around for a cheaper 174MM but after looking on ebay and other websites they actually seem more expensive than on the pricing found on the ZWO website, oddly. 

How short would these exposures be on the telescope? 

Thank you for all the help!

[CraigT82]

10 minutes ago, Lucas Barclay said:

Ah I see that does help quite a bit. I had a little look around for a cheaper 174MM but after looking on ebay and other websites they actually seem more expensive than on the pricing found on the ZWO website, oddly. 

How short would these exposures be on the telescope? 

Thank you for all the help!

Yeah used prices are a bit crazy at the minute with people trying to cash in, exploiting the fact that new kit is very thin on the ground due to covid etc. 

To be honest I don't know how long your exposures would be with the 5se. If you can really nail the mount alignment then maybe 10 seconds? I don't have any experience with those mounts. Depends a bit on how sharp and round you want your stars to be! 

You might want to consider spending some of your budget on a used short tube achromatic refractor like an ST80/100. Sure you would get a lot of CA on bright stars but you would be able to expose for longer, get a much wider field of view and get more nebulosity in the images. You could then use the C5 for imaging the moon and planets and the little frac for dso. 

[Lucas Barclay]

4 minutes ago, CraigT82 said:

Yeah used prices are a bit crazy at the minute with people trying to cash in, exploiting the fact that new kit is very thin on the ground due to covid etc. 

To be honest I don't know how long your exposures would be with the 5se. If you can really nail the mount alignment then maybe 10 seconds? I don't have any experience with those mounts. Depends a bit on how sharp and round you want your stars to be! 

You might want to consider spending some of your budget on a used short tube achromatic refractor like an ST80/100. Sure you would get a lot of CA on bright stars but you would be able to expose for longer, get a much wider field of view and get more nebulosity in the images. You could then use the C5 for imaging the moon and planets and the little frac for dso. 

That looks like a definite possible option, do you know any good motorized mounts? I've noticed a lot of equatorial mounts can be quite expensive on the market, cheers for these suggestions! 

[tomato]

Here are a some galaxy images taken with the ASI 178 mono, at 1050 FL, imaging at 0.94 arcsec/pixel by binning 2x2, or in the case of M51, 1x1, 0.47 arcsec/pixel. These are all around 5-6 hrs integration made up of 3 minute exposures.

I should point out the scope is on a mount (Mesu 200) which can track at the required accuracy.

Edited March 23, 2021 by tomato
Mount comment added

[vlaiv]

On 21/03/2021 at 18:39, Lucas Barclay said:

I found out the sensitivity of the sensor is much lower compared to the ASI224MC...

Why do you think this to be the case?

QE of 178 is higher than 224 (81% vs 75-80% according to ZWO website)

ASI178 has higher read noise so you need to offset that with longer exposure time, but that will depend on your sky conditions and if you are using cooled or non cooled version (thermal noise can also serve to swamp read noise in non cooled models).

Another factor to consider is of course pixel size - you need to match FL of telescope to get good sampling rate.

If you match sampling rate and offset higher read noise then 178 is more sensitive than 224.

[Lucas Barclay]

3 minutes ago, vlaiv said:

Why do you think this to be the case?

QE of 178 is higher than 224 (81% vs 75-80% according to ZWO website)

ASI178 has higher read noise so you need to offset that with longer exposure time, but that will depend on your sky conditions and if you are using cooled or non cooled version (thermal noise can also serve to swamp read noise in non cooled models).

Another factor to consider is of course pixel size - you need to match FL of telescope to get good sampling rate.

If you match sampling rate and offset higher read noise then 178 is more sensitive than 224.

Oh this does change my view quite a bit I hadn't realized that.. I had read on one website it was less sensitive but after what you have told me it makes sense how the 178MM has the potential to be more sensitive. I'm not sure if this would work with my rig and conditions however.

Thank you for letting me know about this!

[michael.h.f.wilkinson]

I have done some DSO imaging with the ASI178MM I have (mainly used for solar white light and Ca-K), but at a much faster focal ratio than the F/10 of the C5. I would certainly get a 0.63x focal reducer, which will make life a lot less difficult for DSO imaging, first of all because more photons hit each pixel, and secondly because guiding errors are reduced. The image below was with am APM 80mm F/6 with 0.8x reducer, LRGB image using a filterwheel.

 

[vlaiv]

2 minutes ago, Lucas Barclay said:

Oh this does change my view quite a bit I hadn't realized that.. I had read on one website it was less sensitive but after what you have told me it makes sense how the 178MM has the potential to be more sensitive. I'm not sure if this would work with my rig and conditions however.

Thank you for letting me know about this!

If you take the same scope and put both cameras on and compare them - ASI224 will win / be more sensitive - but that is just pixel size "talking" there.

You can easily turn ASI178 into winning camera even with above same setup - just bin x2 the data. Then you'll have 4.8µm (2 x 2.4µm) vs 3.75µm and that is easy win.

If you have 5" F/10 scope - except for small FOV, you can still get good working resolution with ASI178.

Natively, at 2.4µm pixel size and 1250mm of FL - this gives 0.4"/px. That is way too high sampling rate. You want to be around 1.5" or above at 5". You can bin x4 your data in software but that will make rather small image at 774 x 520.

Alternative would be to get one of these:

https://www.teleskop-express.de/shop/product_info.php/info/p11425_Starizona-Night-Owl-2--0-4x-Focal-Reducer---Corrector-for-SC-Telescopes.html

but that would double the cost.

If you get one of those - then you would be at 0.99"/px and with simple bin x2 - you would get 2"/px - perfect no fuss working resolution and decent size images at 1500 x 1000px

 

[vlaiv]

Btw, I have ASI178mm-cool version and I've also done some imaging with that and TS 80mm F/6  reduced by x0.79 - I'm in red zone on border of white (heavy LP at sqm 18.5), but here are some examples:

Note that this is color version of the camera and cooled also. Good thing about this camera is that it doubles as rather nice planetary imaging camera (cooling has no significance there).

[Lucas Barclay]

3 minutes ago, vlaiv said:

If you take the same scope and put both cameras on and compare them - ASI224 will win / be more sensitive - but that is just pixel size "talking" there.

You can easily turn ASI178 into winning camera even with above same setup - just bin x2 the data. Then you'll have 4.8µm (2 x 2.4µm) vs 3.75µm and that is easy win.

If you have 5" F/10 scope - except for small FOV, you can still get good working resolution with ASI178.

Natively, at 2.4µm pixel size and 1250mm of FL - this gives 0.4"/px. That is way too high sampling rate. You want to be around 1.5" or above at 5". You can bin x4 your data in software but that will make rather small image at 774 x 520.

Alternative would be to get one of these:

https://www.teleskop-express.de/shop/product_info.php/info/p11425_Starizona-Night-Owl-2--0-4x-Focal-Reducer---Corrector-for-SC-Telescopes.html

but that would double the cost.

If you get one of those - then you would be at 0.99"/px and with simple bin x2 - you would get 2"/px - perfect no fuss working resolution and decent size images at 1500 x 1000px

 

Oh! Thank you for all this information this is very useful to me! Do you think it would be a good idea to go for the 178MM and a reducer like the one you linked? I'm happy to see that the 178MM can achieve a good sensitivity since it has such a better sensor size and resolution compared to the 224 (although bin x2 would reduce the resolution).

[Lucas Barclay]

23 minutes ago, michael.h.f.wilkinson said:

I have done some DSO imaging with the ASI178MM I have (mainly used for solar white light and Ca-K), but at a much faster focal ratio than the F/10 of the C5. I would certainly get a 0.63x focal reducer, which will make life a lot less difficult for DSO imaging, first of all because more photons hit each pixel, and secondly because guiding errors are reduced. The image below was with am APM 80mm F/6 with 0.8x reducer, LRGB image using a filterwheel.

 

Oh! Do you think this would work with my setup? The reducer and 178MM? Love the image of the cluster! 

[michael.h.f.wilkinson]

20 minutes ago, vlaiv said:

If you take the same scope and put both cameras on and compare them - ASI224 will win / be more sensitive - but that is just pixel size "talking" there.

You can easily turn ASI178 into winning camera even with above same setup - just bin x2 the data. Then you'll have 4.8µm (2 x 2.4µm) vs 3.75µm and that is easy win.

If you have 5" F/10 scope - except for small FOV, you can still get good working resolution with ASI178.

Natively, at 2.4µm pixel size and 1250mm of FL - this gives 0.4"/px. That is way too high sampling rate. You want to be around 1.5" or above at 5". You can bin x4 your data in software but that will make rather small image at 774 x 520.

Alternative would be to get one of these:

https://www.teleskop-express.de/shop/product_info.php/info/p11425_Starizona-Night-Owl-2--0-4x-Focal-Reducer---Corrector-for-SC-Telescopes.html

but that would double the cost.

If you get one of those - then you would be at 0.99"/px and with simple bin x2 - you would get 2"/px - perfect no fuss working resolution and decent size images at 1500 x 1000px

 

Hadn't seen that reducer yet. That would work rather neatly in my C8 combined with the ASI183MC and ASI183MM-Pro I have (15.9mm diagonal). This would mean serious competition for the 6" F/5 Schmidt Newton (762 mm focal length at F/5 vs 812 mm at F/4).

[vlaiv]

2 minutes ago, michael.h.f.wilkinson said:

Hadn't seen that reducer yet. That would work rather neatly in my C8 combined with the ASI183MC and ASI183MM-Pro I have (15.9mm diagonal). This would mean serious competition for the 6" F/5 Schmidt Newton (762 mm focal length at F/5 vs 812 mm at F/4).

Indeed.

Two sample images on TS website show rather nice stars on ASI183 sized sensor.

[michael.h.f.wilkinson]

10 minutes ago, Lucas Barclay said:

Oh! Do you think this would work with my setup? The reducer and 178MM? Love the image of the cluster! 

The 0.63x reducer would certainly work in a C5, in combination with an ASI178MM. The 0.63x reducer is a lot cheaper, and doesn't require a 2" visual back, which the Starizona reducer does require. Note that the image of M13 was taken at just 384mm focal length, whereas the C5 with 0.63x reducer has more than twice that at 788mm. Even with the 0.4x reducer you end up with 500mm. If you invest in something like the Starizona 0.4x reducer, and a 2" visual back, costs all adds up and I would wonder if a small refractor might not be the better investment. You might be able to find the 0.33x reducers solely intended for imaging with small sensors that can be had for very little, but I do not know whether the image quality is sufficient for the small pixels of the ASI178MM.

[vlaiv]

x0.63 reducer and bin x2 could still be doable? It would sample at 1.26"/px - and that is still too high in my opinion, but not that far away from 1.5"/px