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cuivenion

M51 with a ZWO ASI224

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Hi, This was imaged with a ZWO ASI224 and 130PDS on a Skywatcher HEQ5 using Sharpcap software. This image of M51 was taken on Tuesday night/Wednesday morning.

It is 683 x 10 second exposures with 200 darks. Stacked and processed in Pixinsight. I was shocked at the amount of detail from only 10 second exposures, I'm quite happy with this one. Any comments and constructive criticism welcome.

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Yes, there is a lot of detail there for such short subs. Lots of them helped, no doubt!

I am particularly interested in this, as I have just purchased a 224 and have been interested to know how long I can make useful exposures without cooling. This suggests that one answer is "plenty long enough".

Thanks for posting.

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Thanks, the only problem with the short exposures is I'm losing the star colour because I need to up the gain so there are enough stars for the stacking software to detect. Maybe there's a way to have Pixinsight detect the stars that aren't visible before a stretch, I'll have to look into it. I thought I'd play it safe with this one.

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Very surprising, and excellent! I'll also have a try with my ASI224 on some brighter DSOs.

Chris

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Thanks Michael, I'm really impressed with the 224. I could even see the Galaxy with 1/2 second exposures at high gain! Made framing it a doddle!

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1 minute ago, cuivenion said:

Thanks Michael, I'm really impressed with the 224. I could even see the Galaxy with 1/2 second exposures at high gain! Made framing it a doddle!

Very interesting. I might well use my ASI224MC on my 80mm F/6 with reducer. That should work. Using one of the other ASI cameras as autoguider on the ST80 should even allow longer subs. Very interesting.

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

Very interesting. I might well use my ASI224MC on my 80mm F/6 with reducer. That should work. Using one of the other ASI cameras as autoguider on the ST80 should even allow longer subs. Very interesting.

It has 19k full well at minimum gain and the read noise is still at 3-3.5 or so which is a lot lower than most Canon Dslr's at minimum iso. Should work great.  I'll give longer exposures a go myself on some fainter objects.

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Just realised there is a cooled version of the 224 - I previously assumed yours was uncooled - is this correct? Thanks.

Edited by Demonperformer

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Yeah there is a cooled version, not mine though. Out of my price range at the moment. There's the 385 as well, similar noise and performance but a slightly bigger chip. I'll probably go for that at some point.

Edited by cuivenion
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I have a Peltier cooler lying around somewhere. Must get round to making my own cooler. Really curious what e.g. my ASI178MM would do with H-alpha filter on my Canon 200mm F/2.8 L lens. Should be very interesting.

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

I have a Peltier cooler lying around somewhere. Must get round to making my own cooler. Really curious what e.g. my ASI178MM would do with H-alpha filter on my Canon 200mm F/2.8 L lens. Should be very interesting.

Looking forward to checking out the images.

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12 minutes ago, Demonperformer said:

Just realised there is a cooled version of the 224 - I previously assumed yours was uncooled - is this correct? Thanks.

Just looking on FLO and apparently the cooled version has been discontinued, one left at £390. Wish I had the spare cash.

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Very nice. 
The local deringing on the deconvolution settings are causing some some black ringing around the stars. You may need to refine the star_mask somewhat by adding some convolution to it so it blurs the edges of the mask. 

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5 minutes ago, artoleus said:

Very nice. 
The local deringing on the deconvolution settings are causing some some black ringing around the stars. You may need to refine the star_mask somewhat by adding some convolution to it so it blurs the edges of the mask. 

Thanks for the feedback. I knew the star mask had something to do with it, but I wasn't sure what to do about it as I'm still quite new to Pixinsight. I'll give it another go soon. Cheers for the help.

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Great result! I've dabbled doing DSO's with my ASI120, but nothing close to this. Lovely detail in there.

Edited by Lockie
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just brill, great pic.

                          bob.

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2 hours ago, cuivenion said:

Thanks, the only problem with the short exposures is I'm losing the star colour because I need to up the gain so there are enough stars for the stacking software to detect. Maybe there's a way to have Pixinsight detect the stars that aren't visible before a stretch, I'll have to look into it. I thought I'd play it safe with this one.

Software should be able to pick up stars regardless of the gain - it is SNR that matters, not if star is visible or not on unstretched image.

You also don't need to go that high in gain, unity should be ok - not much difference in read noise between unity and high gain. But if you want to exploit that last bit of lower read noise, use gain that will give you multiples of 2 of ADU to avoid quantization noise. That would be 135 + n*60 so 135, 195, 255, ...

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16 minutes ago, bob-c said:

just brill, great pic.

                          bob.

Cheers Bob!

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5 minutes ago, vlaiv said:

Software should be able to pick up stars regardless of the gain - it is SNR that matters, not if star is visible or not on unstretched image.

You also don't need to go that high in gain, unity should be ok - not much difference in read noise between unity and high gain. But if you want to exploit that last bit of lower read noise, use gain that will give you multiples of 2 of ADU to avoid quantization noise. That would be 135 + n*60 so 135, 195, 255, ...

Hi, I thought that would be the case, but as I wasn't sure I just played it safe, thanks for the info. The last point has gone over my head a bit. I've not come across quantisation noise. Looks like I've got some reading to do. You've obviously got a deeper understanding of this than me, you couldn't finish off that equation showing the correct gains could you please?

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