ASI1600mm cool

[Guest]

Thanks both - just getting things ready for tonight - going to reshoot NA neb with the Pelican as well this time :-)

David

[trev27]

2 hours ago, Gina said:

Well, I like to use a high gain setting and cool the camera to reduce the noise - I believe in getting as much as possible out of my equipment and this camera just gives!   I just can't believe how good it is compared with the Atik 460EX mono CCD cameras that I've been using in the past!!   I thought the 460EX was the "bees knees" but I really love this new ZWO

Amazing isn't it? Coming from a DSLR I can't quite believe how much signal gets picked up. And the smaller chip is way more forgiving than the full frame cam on my refraftor. I am finding the whole monochrome imaging a challenge though. Learning time! 

[SkyBound]

On 28 August 2016 at 20:44, MattJenko said:

A matched colour and mono for LRGB would be good for some targets, although you would have too much Green data relative to the R+B. If you bin a colour camera it basically turns into a less sensitive mono camera. The thought of trying to get 2 scopes aligned and taking images at the same gives me nightmares just thinking about it though.

Thanks for the reply

first of all could the green Chanel not be lowered by 50% during processing to counteract the extra green relative to R and B ?

secondly, could you explain a bit more about the binning of a colour camera, making it into a less sensitive mono ?

and thirdly.  I think I would image with the same scope, doing say mono first, then collect the RGB afterwards...

sorry for all the questions

[SkyBound]

On 28 August 2016 at 21:43, wimvb said:

On the zwo website I noticed that their rgb filters are designed to exclude the sodium and mercury lines between green and red. This gives an advantage for the mono with filters, in high LP areas. The colour model would need a LP filter.

So if  i just put a LP filter on the colour camera, that would have the same effect ?

and surely that would be cheaper than a set of LRGB

[Gina]

Using this camera is a "whole new ball-game" for me - enormous amounts of data to shift!  I'm running at over 3GB an hour currently.  APT is storing the data on drive C: and I can't persuade it otherwise.  I'm having to move data manually to D: and then transfer it from there to my desktop indoors.  This is rather silly and I'll have to sort it out.  Saving to an external USB drive on the laptop would be good but I haven't got any spare USB ports.  I could get a better laptop I guess but I'm planning to change over to Linux and the Raspberry Pi 3 - probably more than one of them.

[Gina]

Now have the first OIII sub to show.  Changed from FITS to TIFF and then histogram stretched in Ps, resized and saved in PNG format.

[wimvb]

13 minutes ago, SkyBound said:

So if  i just put a LP filter on the colour camera, that would have the same effect ?

and surely that would be cheaper than a set of LRGB

No, not quite.

Here's the transmission spectrum for the RGB filters (all three filters shown in the same spectrum). Note the low transmission at 580  nm

Here's the transmission spectrum for a Baader UHC-S L-Booster light pollution filter, in almost the same wavelength range

The ZWO filters cover a much broader wavelength range. All three filters allow more light to pass in their respective range. This will affect exposure time for stars.

Note that for the main spectral lines (Ha, OIII, SII), the transmission is comparable for ZWO and Baader. The difference should therefore be less for nebulae that emit in these wavelengths

[MattJenko]

 

32 minutes ago, SkyBound said:

Thanks for the reply

first of all could the green Chanel not be lowered by 50% during processing to counteract the extra green relative to R and B ?

secondly, could you explain a bit more about the binning of a colour camera, making it into a less sensitive mono ?

and thirdly.  I think I would image with the same scope, doing say mono first, then collect the RGB afterwards...

sorry for all the questions

#1 - yes you can balance the channels, its just not the most efficient way of capturing data with an RGGB colour combination.

#2 - when you bin a colour camera (if it allows it) what tends to happen is that all 4 pixels in the 2x2 binned section contribute to the overall value of that bigger 'pixel'. Because the 4 smaller pixels have colour filters in front of them, the total number of photons that hits the bigger "pixel" is less than if there were no filters there at all, as in a mono camera.

#3 - The order in which you do LRGB doesn't really matter, but seeing as Lum is the most important in terms of detail, it usually pays to get that right first and then get some colour data afterwards.

#4 - no worries.

 

[SkyBound]

Can anybody comment on the sensitivity of the colour version of this camera, compared to the colour versions of other popular CCD cameras, such as the Atik range....

being new, not sure I want to jump straight into mono...and the OSC version seems the next best logical step, but not if the colour version is not recommended...for any reasons...

[topgearuk]

On 29/08/2016 at 14:08, Gina said:

This camera will work perfectly well with 1.25" filters in a filter wheel provided the distance from filter to camera is kept small.  eg. I have an Atik EFW2 which takes 9 1.25" screw-in filters with the camera directly attached using the adapter filter ring and the supplied gender changer on the camera.  The Asahi Pentax old film SLR camera lens is attached to the FW with a short adapter and easily reaches focus on the image sensor.  It also works fine with the FW attached to scopes in the usual way.  This provides a superb widefield imaging rig.  FOV is about 7x5 degrees with 135mm lens.

After a DSLR the ZWO ASI1600MM-Cool camera will "blow you away"!  It is extremely sensitive and has very low noise when cooled.  Cooling only works down to about freezing point with a DSLR I found but these cameras, although also with CMOS sensors, are completely different and cooling down to -23°C (about the lowest I have achieved consistently on these warm nights) removes most of the noise even at high gain settings.

As for filters, I have Astrodon narrowband filters which aren't cheap but I believe them to be the best available and needing only 1.25" ones the cost is far less than for the bigger ones.  You may find the cheaper Baader filters adequate if funds are limited.  The production quality of Baader filters is very good but they are slightly wider bandwidth which means the stars come out bigger and brighter compared with the DSO.  For LRGB, I find Baader filters fine but I haven't yet tried them with this camera.

Thank you so much for your very informative reply, this has been really helpful.

I'm glad 1.25" filters will work, I'm looking at this filter wheel, 7 x 1.25", https://www.firstlightoptics.com/starlight-xpress-accessories/sx-filter-wheel-1.html, can anyone see any problems using this one? it's cheaper then the EFW2? And can be be brought with T-mount front and back, which I think is the correct fittings

Then a set of LRGB Baader and possible the Astrodon's 3nm, if I can bring myself to part with that much cash on 3 bits of glass.

One question, will this set-up work/match my Canon 70-200mm F2.8L lens or would I need bigger filters? Or do I just use this set-up on my ED80

[Andyb90]

42 minutes ago, topgearuk said:

I'm looking at this filter wheel, 7 x 1.25", https://www.firstlightoptics.com/starlight-xpress-accessories/sx-filter-wheel-1.html, can anyone see any problems using this one?

I've ordered the asi1600mm cool and that filter wheel. I checked with FLO and they said it would be fine with the camera.

Andy.

[MattJenko]

I use the ASI1600 and the SX filter wheel with 1.25" filters and while there is slight vignetting in the edges, it calibrates out fine with flats.

[Guest]

I tried some new setting last night on the North America Nebula - including the Pelican as well this time

20x30 seconds on LR and B and 10x30 seconds on G (same amount of time as my first attempt but halving the exposure times and doubling the quantity of subs)

I increased the gain from 70 to 139

No darks (can't figure them out yet) but I have used flats on each channel

Processed in PI

I think it looks about the same - very noisy of course as there's not much time on it - but pretty cool for 30 second exposures - next test will be 10 minute subs :-)

David

[MattJenko]

1 hour ago, David_L said:

- next test will be 10 minute subs :-)

I think this camera's strength is clean, shorter subs. If you go for 10 minute ones, then you will need vast total integration times to get the dynamic range a 16 bit camera would give you with 10 min subs, in the order of 8 hours worth per channel at least for 48 frames a channel. Also, I have noticed some glow at 5 mins which is completely absent at 2. For LRGB imaging, with my setup, I reckon unity gain (139) and loads and loads of 30 second subs hits a bit of a sweet spot. I am yet to dare to try 1 sec subs and use Autostakkert though, but think it should be a fun experiment once my narrowband image is all done and out of the way and I have seen some images made this way on the ZWO site.

[wimvb]

2 hours ago, David_L said:

I tried some new setting last night on the North America Nebula - including the Pelican as well this time

20x30 seconds on LR and B and 10x30 seconds on G (same amount of time as my first attempt but halving the exposure times and doubling the quantity of subs)

I increased the gain from 70 to 139

No darks (can't figure them out yet) but I have used flats on each channel

Processed in PI

I think it looks about the same - very noisy of course as there's not much time on it - but pretty cool for 30 second exposures - next test will be 10 minute subs :-)

David

 

Great result.

There is some green in the background, that can be cleaned up by SCNR.

I took the liberty of downloading your image, and played with it in PI. Did an exponential stretch with a lightness mask to pull out detail in the dark areas (Gulf of Mexico) and a HDRMultiscaleTransform to get more contrast in the NAN and Pelican. You picked up a lot of detail with these short exposures, very impressive.

(Results from processing an 8 bit png are never nice to look at, so I won't show the image here.)

There was quite some noise showing in the final result (surprise, surprise). I think that with short subs like yours, the image would benefit from a larger number (40+ on each colour), or TGVDenoise in the linear post processing stage.

BTW, since this camera has a CMOS, just like a DSLR, does anyone know if it needs dithering???

[Guest]

4 hours ago, wimvb said:

Great result.

There is some green in the background, that can be cleaned up by SCNR.

I took the liberty of downloading your image, and played with it in PI. Did an exponential stretch with a lightness mask to pull out detail in the dark areas (Gulf of Mexico) and a HDRMultiscaleTransform to get more contrast in the NAN and Pelican. You picked up a lot of detail with these short exposures, very impressive.

(Results from processing an 8 bit png are never nice to look at, so I won't show the image here.)

There was quite some noise showing in the final result (surprise, surprise). I think that with short subs like yours, the image would benefit from a larger number (40+ on each colour), or TGVDenoise in the linear post processing stage.

BTW, since this camera has a CMOS, just like a DSLR, does anyone know if it needs dithering???

I completely forgot about SCNR in my workflow so thanks for thinking of that :-)

I'll try the exponential stretch / mask you mention - I haven't done that before

As for HDR - I gave it a brief play but with so much noise I thought I'd leave it until I got more data

I did use TGV, once with 100 iterations then with 200 - probably could go to 300 - I'll give that a shot

I also used MorphologicalTransformation for star reduction (5pt circular)

There's one surprise I've had from both these images and that is the pink! Ghastly stuff and no one has called me on it - I was hoping they would and then explain a way around it.

I don't like to mess around with the colour balance in my images because I feel like I'm "painting" it otherwise - I limit it to the LInearFit process to balance them and then SCNR to get rid of the extra green - I find that acceptable

Is there any thing I'm doing wrong with the L channel perhaps that's feeding the pink monster in both these images ? :-)

Also - zooming in I see little black dots everywhere - byproduct of not using darks? or is that how noise  presents itself in LRGB - never had it with my OSC

Thanks for your advice - SCNR is back on the table lol 

David

 

[wimvb]

For tgvdenoise, have look here

http://wimvberlo.blogspot.se/2016/07/noise-reduction-for-dslr-astroimages.html

Hydrogen clouds can emit in both red (Ha) and blue (Hb). Some more than others. NB imaging only picks up one of these. That's why targets are always red in images. One way around this is to blend Ha in the blue layer. My image of the California nebula, taken with an unmodded dslr, shows a purple/magenta nebula. This the result of a comination of low sensitivity in Ha and emission in Hb.

If you examine the colour histograms of your image, you'll notice that the red background level is lower than blue and green (after scnr). One of the things I did with your image, was to align the histograms' background peaks. This made the nebula much more intense red.

I'm not at my computer atm, but I can pm you my version tonight.

Cheers,

[Guest]

32 minutes ago, wimvb said:

For tgvdenoise, have look here

http://wimvberlo.blogspot.se/2016/07/noise-reduction-for-dslr-astroimages.html

Hydrogen clouds can emit in both red (Ha) and blue (Hb). Some more than others. NB imaging only picks up one of these. That's why targets are always red in images. One way around this is to blend Ha in the blue layer. My image of the California nebula, taken with an unmodded dslr, shows a purple/magenta nebula. This the result of a comination of low sensitivity in Ha and emission in Hb.

If you examine the colour histograms of your image, you'll notice that the red background level is lower than blue and green (after scnr). One of the things I did with your image, was to align the histograms' background peaks. This made the nebula much more intense red.

I'm not at my computer atm, but I can pm you my version tonight.

Cheers,

Thanks - that would be great

This histogram was aligned after LinearFit but I think I dropped the green channel a bit as I'd forgotten about SCNR and I was trying to kill the pink :-)

I'm going to have another go at this tonight for practice at LRGB processing - unless it's clear - if it is I'm going elephant hunting...... :-)

I found some really useful guidance here too: http://wimvberlo.blogspot.co.uk/

:-)

Thanks

David

 

[wimvb]

3 minutes ago, David_L said:

 

I'm going to have another go at this tonight for practice at LRGB processing - unless it's clear - if it is I'm going elephant hunting...... :-)

I found some really useful guidance here too: http://wimvberlo.blogspot.co.uk/

:-)

Thanks

David

 

Bring a big gun. 

Cool, didn't know I had a uk site as well.

[Andyb90]

I checked with FLO and should be getting my 1600, wheel and filters next week. 

Andy.

[Guest]

32 minutes ago, Andyb90 said:

I checked with FLO and should be getting my 1600, wheel and filters next week. 

Andy.

....welcome to the New World Neo.....

 

LOL!

[jimboozle]

Troops - thank you for the comprehensive review of this camera - it's really making me think now.... I'm so torn between this and a 490ex... Is this really that much better than a well cooled modded DSLR? Is the CMOS really on par with CCD?

 

i image through a 120ed-ds pro and a wo66, currently with an 1100d Astro modded, and building a cooled 1100d

 

Second question - if I'm using 36mm unmounted filters, which filter wheel would you go for???

 

such a difficult decision, and not an insignificant amount of beer tokens involved. 

 

Hmmmm

[jimboozle]

On 31 August 2016 at 10:36, David_L said:

Thanks - that would be great

This histogram was aligned after LinearFit but I think I dropped the green channel a bit as I'd forgotten about SCNR and I was trying to kill the pink :-)

I'm going to have another go at this tonight for practice at LRGB processing - unless it's clear - if it is I'm going elephant hunting...... :-)

I found some really useful guidance here too: http://wimvberlo.blogspot.co.uk/

:-)

Thanks

David

 

 

On 31 August 2016 at 10:39, wimvb said:

Bring a big gun. 

Cool, didn't know I had a uk site as well.

Just checked out your blog @wimvb thank you for sharing your expertise, and I'll be swotting up next time work calms down!

[wimvb]

Glad if some of it can be of use.

Cheers,

[topgearuk]

I'm just about to push the button, does this look like a good combination and will it mount straight on to my SW80ED with Field Flattener?.. Will I need any additional spacers? Am I missing anything (other than knowledge, I looked but can't find that)

I live in an area with reasonable LP, I currently use a CLS clip in filter in my Canon.. Will this new setup require something like this also?

I already have planned my first target with the above equipment, it will be to get a reasonable image of M31 and then in the near future I will be adding some Astrodon filters to my arsenal.