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Andyb90

ASI1600mm cool

850 posts in this topic

Hi Everyone,

I read the announcement from FLO about this new camera so thought I'd have a look at the ZWO Facebook site where some DSO images have been posted.

The latest image of part of the Virgo cluster looks very impressive to me.

But I notice the exposure times seem very short. As a relative newcomer to AP I've always thought longer exposures (within reason) are better or have I missed something?

Andy.

 

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I believe that many of the images were unguided as are those on zwo's forum thus many shorter exposures rather than fewer long exposures.

I agree that the images look impressive for short exposures and not just the 1600 but the other cameras in the range.

I have a mono 120 and i am going to try this method as its a much simpler setup than guiding

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The exposures for the Virgo cluster are stated as:

22x20sec L and 20x30RGB

So that would be just over 37 minutes!

Although it doesn't say what telescope was used or where the images were taken.

Would this sort of result be expected for the same exposure times if a larger aperture AP scope (say 10-12 inches) was used under dark skies?

Andy.

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New CMOS based cameras like short exposures and that's what more often will happen - X second exposures, including 1 second exposures in some cases ;)

First - with very low read noise combined with high sensitivity you don't need long exposures to catch the signal at acceptable SNR. Second - you have 12 bit data that during stacking is converted to 16 bit stack and for it to work you need more than just few frames (planetary imaging does that with 8 bit frames). And third - if you can do short exposures then you can use higher resolution normally unusable for DS imaging due to seeing (and guiding) - lucky DS imaging all the way.

For DS imaging you don't use exposures as long as possible, but as short as possible for a good end result.

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Thanks for the information riklaunim that explains alot.

I missed this bit of info in the description of the Virgo image:

'AS300 (300/1200)'

I assume that means a 300mm scope so 12 inch aperture.

Would the larger aperture also be helping to get that result with shorter exposures?

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Faster f/ratio would give the option to go shorter, where as bigger telescope (and thus focal length) would force shorter exposures due to seeing.

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Ok, that makes sense.

I can see there is a table on the Facebook page comparing the ASI1600 to KAF8300.

From what I understand KAF8300 is a CCD sensor, that's correct isn't it?

Andy.

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There's a nice image of M101 taken with the 1600 on facebook:

https://www.facebook.com/photo.php?fbid=1007625802608180&set=o.442194685829760&type=3&theater

The exposure is listed as 45x30sec 22.5 minutes per filter!

There is also a picture of the scope used to take the image on cloudy nights. Looks like a beast :icon_biggrin:

http://www.cloudynights.com/index.php?app=core&module=attach&section=attach&attach_id=690356

Andy.

Edited by Andyb90

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4 minutes ago, Andyb90 said:

The exposure is listed as 45x30sec 22.5 minutes!

That is the total exposure per filter so the total will be 3X or 4X that - still massively impressive though.

 

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Ah yes, just edited my previous post. This looks very tempting as an upgrade from my DSLR. The price seems very reasonable.

Looking forward to seeing more images.

Andy.

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just looking at the asi 1600 colour cooled,would love more reviews though

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I'm very very very tempted by the mono version - trying to raise the funds at the moment. Certainly a step up from my 450D in my light polluted area.  Shame that there are so few images available in the wild. Make sure to check the Beta test thread over on CN. Some great results with lots of short exposure + samples of bias and dark frames. The really long exposures showed some strong glow and noise in the darks, but much less than most of ZWO's other current CMOS cameras.

Have a look at the Crescent shot on this page: http://www.cloudynights.com/topic/535506-asi1600mmc-beta-test/page-32

That's from only 8x5 mins. 

Keeping an eye on this camera!

 

Trev

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I see someone has posted comparison shots of the Crescent nebula with a QSI683 camera in that same thread.

2 hours ago, trev27 said:

Have a look at the Crescent shot on this page: http://www.cloudynights.com/topic/535506-asi1600mmc-beta-test/page-32

But looking at the price of the QSI683 it's far more expensive than the asi1600 mono. Is that really a fair comparison?

Andy.

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Check out a new thread HERE over on CN. Getting some very interesting results. Its looking to be very comparative to the 8300 ccd sensor and even beating it in some aspects. Me personally I would rather go with the 1600 over the 8300. But once you start getting to better sensor than the 8300 the 1600 drops off pretty quick. But this is just the beginning of a CMOS era. 

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Wowsers! I think I'm pretty much ready to pull the trigger, especially since there is 10% off until Tuesday. Have a bid on a C9.25 on ABS but haven't heard back - if I don't the funds will go towards this camera. Still amazed at how much details some of these guys are pulling with such short exposures stacked. Would probably use the camera with Baader LRGB filters in an Atik manual wheel and an IDAS up front.

T

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I'm interested in this camera. What size filters would be recommended?

Would it be best to go with 36mm, rather than 1.25" ?

Or even 2" ?

Andy.

 

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It depends on the thickness of the filter wheel and what else is in the optical train.

You can calculate the minimum filter clear aperture required for full illumination using the formula:

minimum filter size = CCDdiag*(FL-DC)/FL + (DC/f), where FL is focal length, CCDdiag is the size of the chip diagonal, DC is the distance between the chip and the filter, and f is the focal ratio of your scope

Be aware that the minimum size here is the clear aperture not the overall filter size - a typical 1.25" filter has a clear aperture of around 28mm depending on manufacturer whereas the 36mm unmounted Baaders have a clear aperture of  nearly 36mm

HTH

Derrick

Edited by derrickf

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Just to check is the calculation this:

( ( CCDdiag * ( FL - DC ) ) / FL ) + ( DC / f )

Andy.

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 Yes, those 2 expressions are identical.

 

Derrick

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Im not sure if I've understood this correctly but from what I've read this camera works better with short exposures? Like I've  seen some 60 second Sub stacks with this camera that look the same if not better than 20min subs on a ccd. Surely this isn't correct? Or is this the future and guiding is a thing of the past?

Can anyone clear up my confusion?

Matt

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59 minutes ago, matt-c said:

Im not sure if I've understood this correctly but from what I've read this camera works better with short exposures? Like I've  seen some 60 second Sub stacks with this camera that look the same if not better than 20min subs on a ccd. Surely this isn't correct? Or is this the future and guiding is a thing of the past?

Can anyone clear up my confusion?

It's the power of low read noise, and the fact that in many cases multi-minute exposures aren't needed/beneficial even with low noise CCDs. Planetary photographers first pick those CMOS based cameras and started imaging DS objects at short exposures showing that it actually works.

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On 28/05/2016 at 08:44, Andyb90 said:

Just found this image of M8 on Astrobin:

https://www.astrobin.com/250499/

Looks impressive for a single sub.

Andy.

What really irks me about people like this is that they only provide half the information necessary for someone to make any use of his image. If you look at this postings on CN people ask him what his set up is yet he never responds. People on AstroBin also ask the same and yet again, no response. I don't know if I should be impressed or not.

If he can't even reply to a simple question how can I take the guy seriously, was it even with this camera, was it even his own data and so on?

From what I gather, though this is just an assumption, it may have been taken with a Skywatcher MN-190...but then again it could have been taken with the Hubble for all I know.

 

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Yes, I can see on the CN beta testing thread only the exposures are mentioned.

I've been following or at least trying to follow the thread for a while, but it gets very technical in parts so I'm struggling a bit.

The recent posts have mentioned a gain setting and 'unity gain'. What would changing the gain setting normally be expected to achieve?

Do CCD cameras have such a setting?

Andy.

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