ASI1600mm cool

[Filroden]

3 minutes ago, David_L said:

Its looking good so far :-)

I can't figure out how to keep the background black (like your image) without clipping the histogram

I've noticed many images from this camera with nice sharp black backgrounds and try as I might I can't replicate it

I'm sure it's all down to the levels/curves adjustment so I'll keep working at it but your image is a really good benchmark for me to work too :-)

David

 

It's far from black. The background in my image is between about 15 and 20 RGB - very dark but not black. I stretch using the iterative MaskedStretch first (allowing 0.005% clipping), then, if necessary, tweak it a little further in HistogramTransformation, and do the fine work in CurvesTransformation. I work the curves at later stages in the process too using various masks to protect or target various elements (stars, nebula, background).

[Guest]

56 minutes ago, Filroden said:

It's far from black. The background in my image is between about 15 and 20 RGB - very dark but not black. I stretch using the iterative MaskedStretch first (allowing 0.005% clipping), then, if necessary, tweak it a little further in HistogramTransformation, and do the fine work in CurvesTransformation. I work the curves at later stages in the process too using various masks to protect or target various elements (stars, nebula, background).

Thanks - I guess I was just saying it was better looking than mine - more black :-)

I'll try the techniques you mention too - I haven't used MaskedStretch before - that's what I love about PI - always something new to try 

Thanks 

David

 

[Gina]

Very good Ken - lovely image

[MattJenko]

MaskedStretch is a great way to stretch an image without bloating out the stars. It can struggle with nebula in a star field, so I tend to loosely follow Harry's method of using a masked stretch for the stars and a histogram stretch for the nebula in a copy and then put them together with the aim of getting the best of both worlds. The key to that is matching background levels between the 2 images.

[Guest]

35 minutes ago, MattJenko said:

MaskedStretch is a great way to stretch an image without bloating out the stars. It can struggle with nebula in a star field, so I tend to loosely follow Harry's method of using a masked stretch for the stars and a histogram stretch for the nebula in a copy and then put them together with the aim of getting the best of both worlds. The key to that is matching background levels between the 2 images.

I'm a huge Harry's Astroshed Tutorial fan - I need to revisit them as I missed the maksed stretch guidance from the look of it - thanks!

David

 

[Andyb90]

Desperate to start imaging with the camera. I'm just waiting on the Esprit 100 I ordered.

Andy.

[Guest]

I tried to image at higher gain (380) and offset (from 10 to 50) but the preview was terrifying! lol

Completely washed out before any stretch - I didn't have the courage to press on and commit the 2hrs of data I got to these settings and went back to 139 (unity gain) and 10

One thing I did notice was that switching from 10 to 50 on the offset made a noticeable difference to the brightness of the preview image

I don't understand why I'm getting such an overexposed result when others are clearly imaging at gains of up to 500?

Sounds like a mission for a partly cloudy night when I've got nothing to lose har har

David

 

 

[MattJenko]

You should check the actual pixel values of your higher gain image tests, not how the preview looks. Lots of things can fox a simple auto-stretch I have found.

[Demonperformer]

Maybe (hopefully) a silly question:

I am currently running off some darks on this camera at various exposure-lengths and temperatures. Do I need to consider different sets of darks for different 'gain' levels as well?

Thanks.

[Gina]

I think so but could be wrong.

[MattJenko]

I would say yes, because the amplifier might well cause the dark current to vary. However, for short exposures, I have found I don't need darks with my images at all. Because so many subs are being taken, a little dither or natural drift will get rid of most of the noise. I only needed darks for 5 min exposures when I was doing narrowband subs when there was a glow on the right hand side in a couple of places. 30 sec shots show no glow whatsoever. I just use Bias and Flats for those, and it works great.

[Demonperformer]

That's what I was afraid of - gain adds noise (otherwise we would all be using max gain all the time) so that is going to alter the darks. Mmm. In light of this, I will abandon my 'get darks in advance' plan [for some reason windoze decided to switch off the laptop halfway through my 180s set], taking them after the event, so I know I've got the gain right.

Thanks.

[Guest]

I just reprocessed my image of the Bubble Nebula using dark frames - absolutely no difference :-)

David

[Gina]

Well this camera isn't all that noisy   Particularly when well cooled.

[Zakalwe]

30 x 3minute exposures through a 7nm Baader filter. I am blown away by the sensitivity in narrowband. 3 minute subs are giving me more detail than a 10 minute sub with with old Atik 428.

There's very little processing with this image- no darks or bias. Just some flats, which I need to redo as there is a bit of ampglow in the top righthand corner.  Processing was limited to levels and a tweak of curves.

 

Mel 15

 

In comparison, here's 8 x 20 minutes with the Atik. Everything else is the same (scope and focal reducer). A lot more processing and calibrated with darks, flats and bias.

 

 

 

[Andyb90]

26 minutes ago, Zakalwe said:

30 x 3minute exposures through a 7nm Baader filter. I am blown away by the sensitivity in narrowband. 3 minute subs are giving me more detail than a 10 minute sub with with old Atik 428.

There's very little processing with this image- no darks or bias. Just some flats, which I need to redo as there is a bit of ampglow in the top righthand corner.  Processing was limited to levels and a tweak of curves.

That looks excellent. What gain setting did you use?

Andy.

[Zakalwe]

Just now, Andyb90 said:

That looks excellent. What gain setting did you use?

Andy.

Unity gain. I haven't really played with this element yet.

[MattJenko]

3 minutes at unity. that is seriously good. I was doing 5 mins and getting good results - looks like I could drop down as well for Ha at least. Marvellous.

[Zakalwe]

10 minutes ago, MattJenko said:

3 minutes at unity. that is seriously good. I was doing 5 mins and getting good results - looks like I could drop down as well for Ha at least. Marvellous.

I think that even shorter sub lengths will work. The noise is low on these cameras, so it collects signal very quickly. I was looking at a thread on CN and it looks like the exposure times can be seriously short. Like 90 seconds short when using a 3Nm H-a filter

http://www.cloudynights.com/topic/549417-asi1600-experiments-with-high-gain-nb-imaging/?hl= 1600

These CMOS cameras have, IMHO, the potential to revolutionise DSO imaging. Why bother spending a fortune on a high end mount when you can do NB imaging with sub lengths of 90 seconds? Emil Kraaikamp is producing superb images using 1 second exposures on his Dobsonian.

http://www.cloudynights.com/topic/536494-m51-in-poor-seeing-20001s-asi1600mm-cool/

 

[Alien 13]

I think you guys are right I does open the door to unguided imaging even with lightweight portable mounts, can only be a good thing for UK sky's.

Alan

[SkyBound]

1 hour ago, Zakalwe said:

I think that even shorter sub lengths will work. The noise is low on these cameras, so it collects signal very quickly. I was looking at a thread on CN and it looks like the exposure times can be seriously short. Like 90 seconds short when using a 3Nm H-a filter

http://www.cloudynights.com/topic/549417-asi1600-experiments-with-high-gain-nb-imaging/?hl= 1600

These CMOS cameras have, IMHO, the potential to revolutionise DSO imaging. Why bother spending a fortune on a high end mount when you can do NB imaging with sub lengths of 90 seconds? Emil Kraaikamp is producing superb images using 1 second exposures on his Dobsonian.

http://www.cloudynights.com/topic/536494-m51-in-poor-seeing-20001s-asi1600mm-cool/

 

Wow, that is incredible for 1 sec exposures, 2000 of them, so under 34 mins of exposures... ? so a good solid tripod is all that's needed in theory..... very impressive indeed, I am seriously thinking of selling my Atik 383L+ mono and getting one of these, the sensors are pretty much identical in size, what do you guys think about that ?. Good or bad idea ??

[Demonperformer]

Depending on your finances, I would be inclined to buy one first and make sure that you are happy with what you are getting before letting your 383L+ go (this is what I have done with my SX camera).

[Zakalwe]

27 minutes ago, SkyBound said:

Wow, that is incredible for 1 sec exposures, 2000 of them, so under 34 mins of exposures... ? so a good solid tripod is all that's needed in theory..... very impressive indeed, I am seriously thinking of selling my Atik 383L+ mono and getting one of these, the sensors are pretty much identical in size, what do you guys think about that ?. Good or bad idea ??

Bear in mind that that M51 was done on a long focal length....

The 383 is a good camera. I doubt if you would create worse images with the 1600 though. The final image will probably look the same, it's just that you will get there a lot quicker with the 1600.

[SkyBound]

I am still waiting to hear any reviews on the colour version, could it be even quicker to get a superb image with the OSC, ?? I realise that having the bayer matrix will lower the sensitivity but by how much on this camera, if 90 second subs are good with the mono, would you get the same result with 4x the exposure, 360 second subs with the OSC....

[SkyBound]

I also realise that with the OSC you only really get  1/4 of the resolution, but at 16 megapixel you can afford to go down to 4 megapixel images..! As it's still a lot more than some high end mono CCD cameras