ZWO colour camera's

[bomberbaz]

Hello everyone and hope your all well. I have a couple of questions regarding my existing ASI224MC and a possible new ZWO camera.

I currently have a 224MC and i have so far enjoyed using it a very lot.  I have played around with and got good lunar and planetary results with more limited success on DSO's.

The other night I did some imaging of the ring nebula which I realise it a fairly easy target and then swung it around to the crescent nebula for another go at something more challenging but no matter what I did with gain or exposure it failed to show up.  I was using a a 130 P-DS with the camera unguided on a WIFI GTI mount.  Q1) Am I doing something wrong or is this camera not up to the crescent with this scope?

Next I have been toying with the idea of buying something a little more powerful than the 224 which I also realise is something of an entry level camera so I was looking at the 178 version or 183 at a push. I don't really understand it when the information given start discussing some of the technical stats for camera's.

Based upon (178 =6.4/3096*2080) or 183=20.18/5496*3672) the maths appears to give a pretty much same result with the same pixel size albeit with a larger overall sensor from the 183. Q2) Am I missing something on the comparisons?

I know this is a 2 in 1 query and so would be grateful for answers on either or both depending on personal experiences.

cheers

all

Steve

[TerryMcK]

Hi Steve. The 224MC is really a planetary camera and you are trying to image the crescent which is a deep sky object. For this generally use longer exposures (preferably guided) with cooled cameras or a modified DSLR to get the generally fainter deep sky objects. Also some objects are a lot bigger than planets in the FOV. 
Your scope will be great for deep sky in conjunction with a camera like a 533 Pro or 183Pro (both cooled). I’m not familiar with the mount so can’t comment on that. It sounds like a upgrade is in the pipeline.

Edited November 22, 2020 by TerryMcK

[vlaiv]

1 hour ago, bomberbaz said:

Q1) Am I doing something wrong or is this camera not up to the crescent with this scope?

I think that your setup is up to the task, but it really takes a lot of exposure to make it work.

Here is Crescent nebula only starting to show after about hour or so of exposure with similar sized camera (equivalent of ASI120mc) on a similar sized scope - Skywatcher ST102 F/5 achromat (hence blue around stars).

1 hour ago, bomberbaz said:

Next I have been toying with the idea of buying something a little more powerful than the 224 which I also realise is something of an entry level camera so I was looking at the 178 version or 183 at a push. I don't really understand it when the information given start discussing some of the technical stats for camera's.

Based upon (178 =6.4/3096*2080) or 183=20.18/5496*3672) the maths appears to give a pretty much same result with the same pixel size albeit with a larger overall sensor from the 183. Q2) Am I missing something on the comparisons?

Don't replace 224 if you don't really need the funds - add ASI183 cooled version (pro) if you have the budget for it.

224 is the best planetary camera of the three mentioned, but ASI183 has the largest sensor - which translates into larger field of view.

Cameras tend to be more expensive than the optics these days and ASI183 will be faster camera than ASI178 if you pair it with proper scope (I know - this really needs very good consideration - larger scope means larger mount and all of that and AzGti can only hold so much).

Just for the sake of argument, look at this for example:

That is 130PDS and ASI178 and 200PDS + ASI183.

Second combination gives you slightly larger FOV, but it is 8" of aperture vs 5" of aperture. 8" will collect much more light.

In the meantime, have you tried simple 1.25" x0.5 focal reducer by GSO for ASI224 and 130PDS?

[bomberbaz]

1 minute ago, vlaiv said:

I think that your setup is up to the task, but it really takes a lot of exposure to make it work.

 

Here is Crescent nebula only starting to show after about hour or so of exposure with similar sized camera (equivalent of ASI120mc) on a similar sized scope - Skywatcher ST102 F/5 achromat (hence blue around stars).

Don't replace 224 if you don't really need the funds - add ASI183 cooled version (pro) if you have the budget for it.

224 is the best planetary camera of the three mentioned, but ASI183 has the largest sensor - which translates into larger field of view.

Cameras tend to be more expensive than the optics these days and ASI183 will be faster camera than ASI178 if you pair it with proper scope (I know - this really needs very good consideration - larger scope means larger mount and all of that and AzGti can only hold so much).

Just for the sake of argument, look at this for example:

That is 130PDS and ASI178 and 200PDS + ASI183.

Second combination gives you slightly larger FOV, but it is 8" of aperture vs 5" of aperture. 8" will collect much more light.

In the meantime, have you tried simple 1.25" x0.5 focal reducer by GSO for ASI224 and 130PDS?

Thanks for the reply Vlaiv.

I wasn't thinking of replacing the 224mc, I was thinking of adding the 183 uncooled for the larger FOV also I thought it would be more sensitive than the 224 due in the main to having more pixels per area on sensor so overall being a little better for DSO's

I have cheap reducer yes and I had considered it but wasn't sure how effective it would be overall. 

As confused as ever now 😂

(Nice work on the crescent btw) 👍

[vlaiv]

7 minutes ago, bomberbaz said:

I wasn't thinking of replacing the 224mc, I was thinking of adding the 183 uncooled for the larger FOV also I thought it would be more sensitive than the 224 due in the main to having more pixels per area on sensor so overall being a little better for DSO's

I see. Smaller pixels usually mean that camera will be less sensitive. That is, if you use it as is.

ASI183 is good because you have very large number of pixels. It natively has 2.4µm size pixel but has 5496 of them in width. ASI224 has 3.75µm pixel and has 1304 of them in width (if I'm not mistaken).

With binning 4x4, you can easily get from 5496px to 1374px and pixel size will grow from 2.4µm to 2.4 * 4 = 9.6µm

Suddenly you have about the same resolution as ASI224 with 1374px in width - but pixel size is much larger.

This is the same logic I did with FOV above, except this time we did it on pixel level. You can choose which one you want to "keep fixed" - either FOV or pixel count, but in either case, you end up with increased sensitivity.

If you can - get pro / cooled version, it really makes significant difference. ASI183 has amp glow and you want to be able to calibrate it out.

13 minutes ago, bomberbaz said:

I have cheap reducer yes and I had considered it but wasn't sure how effective it would be overall. 

Try that one as well on ASI224, as you already have it and it won't cost you to try it out. Only problem will be reaching the focus, so you might want to use reducer on 1.25" nosepiece but use 2" barrel of camera to attach it to the scope (sinking nose piece inside focuser to get some back focus that way).

ASI224 is small sensor and you might get away without much coma on F/5 scope. I used same sized camera on F/6 newtonian and did not have coma in the corners.

This was with that 1.25" reducer.

[bomberbaz]

6 hours ago, vlaiv said:

I see. Smaller pixels usually mean that camera will be less sensitive. That is, if you use it as is.

ASI183 is good because you have very large number of pixels. It natively has 2.4µm size pixel but has 5496 of them in width. ASI224 has 3.75µm pixel and has 1304 of them in width (if I'm not mistaken).

With binning 4x4, you can easily get from 5496px to 1374px and pixel size will grow from 2.4µm to 2.4 * 4 = 9.6µm

Suddenly you have about the same resolution as ASI224 with 1374px in width - but pixel size is much larger.

This is the same logic I did with FOV above, except this time we did it on pixel level. You can choose which one you want to "keep fixed" - either FOV or pixel count, but in either case, you end up with increased sensitivity.

If you can - get pro / cooled version, it really makes significant difference. ASI183 has amp glow and you want to be able to calibrate it out.

 

Ok thanks for that, I think I am getting a better idea of where you are coming from now. Still not 100% but understanding a little more.  Do you think a read of every photon counts would help?

6 hours ago, vlaiv said:

Try that one as well on ASI224, as you already have it and it won't cost you to try it out. Only problem will be reaching the focus, so you might want to use reducer on 1.25" nosepiece but use 2" barrel of camera to attach it to the scope (sinking nose piece inside focuser to get some back focus that way).

ASI224 is small sensor and you might get away without much coma on F/5 scope. I used same sized camera on F/6 newtonian and did not have coma in the corners.

This was with that 1.25" reducer.

That is a cracking image, although you also have star bloating which I get when I try DSO imaging, interesting. Which galaxy is it btw Vlaiv, fireworks?

[stash_old]

49 minutes ago, bomberbaz said:

Ok thanks for that, I think I am getting a better idea of where you are coming from now. Still not 100% but understanding a little more.  Do you think a read of every photon counts would help?

That is a cracking image, although you also have star bloating which I get when I try DSO imaging, interesting. Which galaxy is it btw Vlaiv, fireworks?

Think that is M82 - here was my attempt live stacked Bin x 1 - 224mc plus c9.25 no reducer but guiding - it is possible but need very clear nights and lots of stacks IMO.

So using a better F will produce a better pic than the one below - sky was very bad and out of focus a bit - plus 50% moon

 

Edited November 23, 2020 by stash_old

[roelb]

You must be able to image the Crescent nebula with the 224MC.

See my trial with Evolution 8" @ f/5

20 x 15 s

 

[roelb]

Consider the ZWO ASI533MC-Pro which is a very sensitive camera without any amp glow.

Evolution 8" @ f/5

25 x 30 s

 

[vlaiv]

9 hours ago, bomberbaz said:

That is a cracking image, although you also have star bloating which I get when I try DSO imaging, interesting. Which galaxy is it btw Vlaiv, fireworks?

It is M82 - Cigar.

Star bloat in that image is due to several factors:

- I used very large telescope for my mount. This was taken with 8" F/6 telescope (OTA from SW 8" Dob) mounted on stock HEQ5. That scope is a sail - any wind will make it move.

- I used x0.5 reducer - questionable optical quality. Those GSO reducers are just finder scope / binocular lens mounted in a cell.

- I was not guiding and I used relatively long exposures. You can see that star shapes are not the best in the image.

In any case, star bloat is always due to inappropriate resolution of the image. In this case I was using ~1.29"/px which is rather optimistic for stock HEQ in average seeing conditions.

In fact, stars in that image are quite good compared to some other images of that galaxy I took. Have a look:

Above is crop from M81/M82 wide image. This was taken with 80mm apo scope again on Heq5, this time with ASI178mcc (color cooled version)

If I reduce above image to approximately the same size, we get very nice pin point stars:

[bomberbaz]

Thanks to you all @stash_old @roelb @vlaiv for your pictures and input. I think I will do nothing for now and try to learn skills better than I currently have. If you are managing such good images then with a bit of practice I should hopefully be able to improve my own results. 

44 minutes ago, vlaiv said:

In any case, star bloat is always due to inappropriate resolution of the image. In this case I was using ~1.29"/px which is rather optimistic for stock HEQ in average seeing conditions.

It is things like this that confuse me vlaiv, one of the stated resolutions on the FLO page for the asi224 is this "1304×976 150fps / 64fps", which is nothing like 1.29"/px as you stated above. Is this a simple calculation to work out?

Cheers all

Steve

[vlaiv]

7 minutes ago, bomberbaz said:

Thanks to you all @stash_old @roelb @vlaiv for your pictures and input. I think I will do nothing for now and try to learn skills better than I currently have. If you are managing such good images then with a bit of practice I should hopefully be able to improve my own results. 

It is things like this that confuse me vlaiv, one of the stated resolutions on the FLO page for the asi224 is this "1304×976 150fps / 64fps", which is nothing like 1.29"/px as you stated above. Is this a simple calculation to work out?

Cheers all

Steve

Indeed that is confusing as term resolution is used in so many cases:

- resolution as number of pixels in image / on sensor

- resolution as in resolving capability of telescope

- resolution as in sampling rate - arc seconds per pixel

 

Sampling rate - resolution that I was referring to - depends on pixel size and focal length. It can be thought of as "zoom factor" when taking a image. It depends on how many arc seconds - angular size in the sky, is covered by a single pixel - hence "/px unit (arc seconds per pixel).

There is simple relationship between object size in the sky and object size in number of pixels - size_in_sky / resolution = size_in_pixels. For example 200 arc seconds galaxy with sampling rate of 2"/px will be 100px wide in image.

Here is how to calculate sampling rate (sometimes referred to as imaging resolution):

Online calculator can be found here: http://www.wilmslowastro.com/software/formulae.htm#ARCSEC_PIXEL

If you are using 130PDS and it has 650mm of FL, and you are using ASI224 with 3.75µm pixel size, you'll get 1.21"/px

Here is like a break down of resolutions (sampling rates) and what they are useful for:

>4"/px - this is wide field imaging with lens and such, any star tracker should give you decent results

3-4"/px - wide field imaging with telescopes - good resolution in almost any seeing, any decent mount should be able to do it unguided with relatively short exposures - any mount guided will be ok. Aperture of 50 or above

2-3"/px - medium to wide(ish) field imaging with telescopes - good resolution in decent seeing, better mounts required unguided, decent mounts guided, 70-80mm or above

1.5"/px-2"/px medium resolution. You need good seeing for this. Very good mounts can do this unguided, you want decent to good mount for this even guided, 100-120mm and above.

1.2"/px-1.5"/px high resolution. You need good seeing this one. Again, only best mounts unguided, good mounts guided, 150mm and above

1.0"/px-1.2"/px very high resolution. You need excellent seeing for this one. Only few premium mounts with encoders will do this unguided, otherwise you need very good / excellent mount guided (stock HEQ5/EQ6 and such will not do it). 200mm and above required

Above is if you want to have tight stars that is. You can sample at 1.2"/px - even with gear that is not up to it as we have shown above - but you get bloated stars, but if you reduce size of your image by x2 to x3 - which makes it go from 1.2"/px to somewhere in 2.5"/px - 3.5"/px range - we get good star shapes since we are in totally different league equipment and seeing wise.

 

 

[bomberbaz]

Super explanation @vlaiv that really does help make things a lot clearer to me.

So my bloated star M57 image was down to the fact I am using the 127 P-DS on a relatively basic model mount unguided. I actually thought it was down to having too much brightness or exposure but now this all makes sense.

So if I am right using a 0.5 reducer increases this to 2.4"/px (I used the calculator and have bookmarked it) which will reduce but not remove the bloating and at the same time shortens exposure times as a result of reduced F ratio. 

Edited November 23, 2020 by bomberbaz

[stash_old]

This might also help -  "simpler site" (still uses the same calculation) for those ,like me, who like to see a traffic system rather than just numbers is https://astronomy.tools/calculators/ccd_suitability

[vlaiv]

55 minutes ago, bomberbaz said:

Super explanation @vlaiv that really does help make things a lot clearer to me.

So my bloated star M57 image was down to the fact I am using the 127 P-DS on a relatively basic model mount unguided. I actually thought it was down to having too much brightness or exposure but now this all makes sense.

So if I am right using a 0.5 reducer increases this to 2.4"/px (I used the calculator and have bookmarked it) which will reduce but not remove the bloating and at the same time shortens exposure times as a result of reduced F ratio. 

I'm a bit confused now. In original post, you mentioned 130PDS, which is this scope:

But now you mention 127 - with added PDS for some reason - there is no 127PDS scope as far as I know, and your signature says SW 127mak which is of course this scope:

Now, second scope is very good planetary performer and matched with ASI224 will give you excellent planetary images, but is probably the worst combination with ASI224 for DSO imaging.

Natively it will give you 0.52"/px, and it certainly won't be able to show you Crescent nebula:

as FOV will be significantly smaller than the target.

If you are indeed using 130PDS then it will indeed be as you say - coarser sampling rate will reduce star bloat, but there is also a bit down to processing - which is whole another topic.

Sometimes star diameters will depend on the way image had been processed / stretched. Stars are in principle gaussian bell curves (or very similar in shape) - when you observe image as 3d graph rather than 2d pixel brightness (in 3d graph - height is equivalent to brightness in 2d - a bit like old maps where mountains are in one color and valleys in another). Look at this diagram:

Horizontal bars represent "white point" or max value - if you stretch hard - then you make that max value be lower and then it makes star cross section larger - star looks like it is fatter - but it is the same star.

[bomberbaz]

Sorry @vlaiv it was my error. I do own a 127 mak but also the 130 P-DS which is what I am referring too in this thread.   

Thanks you very much for all the information, you and the others have been really helpful. I think my expectations were as I thought, greater than the camera's abilities although judging by some of the images on here, not by as much as I had originally thought.

I think if I do go up in camera quality then a better mount will be needed and probably guiding. This is a whole new thing for me and not something I am looking to take on at present.

Thanks again everyone.

Steve

[barkingsteve]

Have you thought about filters ? a good tri band filter for colour cameras will help bring out the details in nebulae. Regarding cameras, if i did not have my 294mc pro my eaa camera of choice today would be the 533 as it has good sensitivity along with good pixel size for the 130pds and no amp glow and would give you a decent fov.

[bomberbaz]

3 hours ago, barkingsteve said:

Have you thought about filters ? a good tri band filter for colour cameras will help bring out the details in nebulae. Regarding cameras, if i did not have my 294mc pro my eaa camera of choice today would be the 533 as it has good sensitivity along with good pixel size for the 130pds and no amp glow and would give you a decent fov.

I am taking you mean the 533 pro Steve, I have looked at that but then I probably end up getting a better mount to improve tracking and stability, maybe a new OTA etc.  

Thinks I will up my skills on a 224 and consider options later down the line but thanks for the pointer.

Steve

[TerryMcK]

I noticed a returned HEQ5 Pro turned up on the FLO website yesterday Steve and thought you may have your eye on that. Next minute it had sold so have to be quick in these pandemic times 😊

[stash_old]

Dont forget EEVA is not normal Astrophotograhpy (although there is a massive overlap) - The faster the scope (e.g. F2 abouts) and a decent sensitive camera means you dont need a EQ mount or guiding at all,as Martin and others will testify too. If you look back through the older threads you will see many  good (for EEVA) pictures by Hildon,Martin and lots of others.  While the EEVA section is a broad cummunity maybe being honest with your goals would help - especially on the wallet side - going down the wrong road.  Just saying 🙂

[gilesco]

I may be a little OCD, but the apostrophe in the title of this thread is really nagging me....

 

[bomberbaz]

1 hour ago, gilesco said:

I may be a little OCD, but the apostrophe in the title of this thread is really nagging me....

 

Yes you are and I am not going to change it! 👹   Sorry, not sorry 🤣  🤣

[bomberbaz]

1 hour ago, stash_old said:

Dont forget EEVA is not normal Astrophotograhpy (although there is a massive overlap) - The faster the scope (e.g. F2 abouts) and a decent sensitive camera means you dont need a EQ mount or guiding at all,as Martin and others will testify too. If you look back through the older threads you will see many  good (for EEVA) pictures by Hildon, Martin and lots of others.  While the EEVA section is a broad community maybe being honest with your goals would help - especially on the wallet side - going down the wrong road.  Just saying 🙂

I was simply wanting to grab some basic images of deep sky objects from my back garden with a short stint of getting the required data without going down the all guided, mega processing, several hours worth of capturing etc and all that malarkey associated with full on imaging. 

This has always been my intention.

And to be fair, other than the star bloating I was very happy with my first bash at M57 the other night. 

 

[johninderby]

1 hour ago, gilesco said:

I may be a little OCD, but the apostrophe in the title of this thread is really nagging me....

 

 

[michael.h.f.wilkinson]

Bit late to this discussion, but you can get the ring nebula with these ZWO colour cameras, you just need more exposure time, I used to have the ASI224MC, but haven't used it for DSO imaging. I have used the ASI178MM with filters, and the ASI183MC without, or with the Optolong L-eNhance filter, and that gives good results, but requires much longer exposures than for planets. This was taken with the Meade 6" F/5 Schmidt-Newton, using 151 15s subs, which isn't nearly enough, and the rather big FOV of the ASI183MC makes the ring seem a bit forlorn

The crescent is a more sizeable target (but still needs more data)

Here are a few more recent targets

All taken with the same combination (and all in need of more data ).