The "No EQ" DSO Challenge!

[Filroden]

33 minutes ago, SteveNickolls said:

So do you have dark frames arranged by temperature to use off the shelf Ken?

Cheers,

Steve

 

Yes. For the ZWO I have darks in 5C bands and multiple gains. For the Canon I only keep one set as it seems to settle to a standard temperature after about 30 minutes after aligning. 

[Filroden]

57 minutes ago, Nigel G said:

I had a go at NGC 7000 last night, a beautiful mild and clear night, went to bed as the morning chorus started 4.20 am

Those are stunning. There is so much to see. 

 

[Nigel G]

Thanks Ken, I think the 5 x 90 frames helped quite a bit , the mount was spot on last night, very clear and no dew at all, all big bonuses helping the imaging session. 

Nige.

[SteveNickolls]

35 minutes ago, Filroden said:

Yes. For the ZWO I have darks in 5C bands and multiple gains. For the Canon I only keep one set as it seems to settle to a standard temperature after about 30 minutes after aligning. 

That's very helpful to know Ken, it will certainly make imaging a lot simpler with the Canon and free up time for the important light frames :-)

Regards,
Steve

[The Admiral]

4 hours ago, Filroden said:

Well, I've just spent 4 hours reprocessing my North America Nebula subs. I gave StarTools a try and although I actually managed to create an image I liked, the process still felt like doing surgery with a mallet! So I downloaded a trial copy of PixInsight to see what a real pro piece of software could do. First I had to retake my bias and dark frames so my camera moved to the fridge for a couple of hours. With bias, darks and flats at the ready, I went through the whole calibration, stacking and processing using PixInsight with only a few minor modifications made in Photoshop at the end.

Very different images! (And I apologise that they are both low resolution. The final TIFF image for the second version weighed in at over 350Mb.)

I think the biggest differences in processing were around being able to remove the background and controlling the stretching.

As you say Ken, very different renditions of the same image, it's hard to believe that they are the same! I think I still prefer your original version using ST, it shows the nebula very well. I suppose purists might argue that the second one is more realistic? I know what you mean about ST, but the more you use it, the more sensitively one can tune it. I had a trial of PI too, and although the workflow is supremely logical there are so many facets to it that I wasn't really prepared to commit. It isn't cheap either. I wish it was possible to directly set the black-point in ST, but on Steve's suggestion I tried the Life module and it does seem to give one a bit of control over that. Else I set it after ST in a final polish in my standard photography application. Do you think you'll migrate to PI?

Ian

[Filroden]

1 minute ago, The Admiral said:

As you say Ken, very different renditions of the same image, it's hard to believe that they are the same! I think I still prefer your original version using ST, it shows the nebula very well. I suppose purists might argue that the second one is more realistic? I know what you mean about ST, but the more you use it, the more sensitively one can tune it. I had a trial of PI too, and although the workflow is supremely logical there are so many facets to it that I wasn't really prepared to commit. It isn't cheap either. I wish it was possible to directly set the black-point in ST, but on Steve's suggestion I tried the Life module and it does seem to give one a bit of control over that. Else I set it after ST in a final polish in my standard photography application. Do you think you'll migrate to PI?

It definitely has merits over DSS for calibration and stacking but it took 4 hours compared to 20 minutes. I need a few more serious attempts with it to compare results. There is no way I could have achieved the second image with Photoshop. There are batch processes that might speed things up but I first want to know what it's doing within each module.

[The Admiral]

4 hours ago, SteveNickolls said:

Hi Ken,

Thanks for posting the two versions of NGC 7000, you have been busy. Have you any plans for further imaging the object? I was tinkering with the idea of trying to image either this nebula or the cocoon Nebula tonight if it is clear and the wind drops here.

I was just posting Ken notifiaction of yours came in. 

I attach my coffee-paint scheme colour chart showing the light pollution to be contended with here. I have also been experimenting with omitting to use dark frames in DSS to see what happens. Please find below two images of M57 using the same x16 sixty second exposures but the first with x50 dark,bias and flat frames and the second image without the dark frames. There certainly seems less background stars and some of the red stars have stayed red and not turned white. Stacking in DSS and processing using StarTools.

Interesting comparison, and I'm not at all clear why ignoring darks should make such a difference. I prefer the colours of the ring in the second image, and it is odd the way the stars are rendered compared to the first one. Not only do they have more colour but some are smaller.

Ian

[SteveNickolls]

Hi Ian,

Thanks for your post regarding the image with and without dark frames. I've had a day questioning what I do and seeing the effect of not using dark frames was one of them :-)

Cheers,
Steve

[The Admiral]

2 hours ago, Nigel G said:

Steve & Ken. Great images, nice work. I love the nebula's always my favourite. 

I had a go at NGC 7000 last night, a beautiful mild and clear night, went to bed as the morning chorus started 4.20 am.

I tried some longer exposures as the mount was on top form last night. The first image is 85 x 45s plus 5 x 90s @1600 iso, I added 2 x 90s darks to 14 x 45s , the flats didn't work again, 50 bias.  The second image is 85 x 45s , darks and bias. DSS and StarTools. The first image with the 5 x 90s seems to be slightly better to me.

I am pleased with these, while taking the subs I could only make out a fairly small amount of emissions but there's plenty in there. I'm sure more could come from these.

Nige.

Fantastic images there Nige, a real credit to the Alt-Az community! I wish I had your endurance . I can't see me getting much imaging done until some interesting objects appear from my vantage point at a sensible time of night, later in the year.

There's a bit more colour in some of the brighter the stars in the second one, and there's an interesting difference in general colour. What the 'correct' colour should be I wouldn't hazard a guess. Knowing that without going through the Startools.log and re-entering the same parameters, it is most unlikely that I can process to give the same finished appearance. To what extent do you think the difference between these two is difference in processing rather than source files?

Ian

[The Admiral]

3 hours ago, Filroden said:

The one advantage of British weather is that our night time temperatures are fairly stable. I find my Canon starts at around 26C as I use live view to align and focus, and cools to about 16C where it stays for the entire imaging session regardless of actual outside temperature. That makes it easy for me to build a dark library.

Olly Penrice reckons that darks for a dslr are a waste of time because without stabilising the temperature the darks won't be representative of the actual taking conditions. Now I realise that this is somewhat at odds with your findings, but he uses a master bias instead of darks, which would save a lot of time if it could be made to work for us. I'm sure that there is more to it than that and I'll have to get more info, but it may be one route to go.

I think he's also said that he uses Astroart for stacking, which is supposed to be a lot quicker than PI. I downloaded a copy but I've yet to make it work, as you can't save on the trial, and it throws up some odd error messages.

Ian

[Nigel G]

6 minutes ago, The Admiral said:

Fantastic images there Nige, a real credit to the Alt-Az community! I wish I had your endurance . I can't see me getting much imaging done until some interesting objects appear from my vantage point at a sensible time of night, later in the year.

There's a bit more colour in some of the brighter the stars in the second one, and there's an interesting difference in general colour. What the 'correct' colour should be I wouldn't hazard a guess. Knowing that without going through the Startools.log and re-entering the same parameters, it is most unlikely that I can process to give the same finished appearance. To what extent do you think the difference between these two is difference in processing rather than source files?

Ian

Thanks Ian, I was rather pleased when I started to develop. 

I tried to keep the processing the same but masks are different every time, the exposure and gamma are identical the colour input is very similar but I didn't take note of everything, a job for a wet night ☺

[The Admiral]

Nige, do you know that ST keeps track of all its settings in the startools.log file, so you don't need to note them down? Don't know how it handles masks though. It's a pity you can't apply the settings instead of having to manually input them, but that's another story.

Ian

Edited May 8, 2016 by The Admiral

[Nigel G]

8 minutes ago, The Admiral said:

Nige, do you know that ST keeps track of all its settings in the startools.log file, so you don't need to note them down? Don't know how it handles masks though. It's a pity you can't apply the settings instead of having to manually input them, but that's another story.

Ian

No I didn't know that, thanks for the info,  there is a tab for saving masks I have seen but not sure if it needs to be purchased to access it.

[Filroden]

 

Olly Penrice reckons that darks for a dslr are a waste of time because without stabilising the temperature the darks won't be representative of the actual taking conditions. Now I realise that this is somewhat at odds with your findings, but he uses a master bias instead of darks, which would save a lot of time if it could be made to work for us. I'm sure that there is more to it than that and I'll have to get more info, but it may be one route to go.

I think he's also said that he uses Astroart for stacking, which is supposed to be a lot quicker than PI. I downloaded a copy but I've yet to make it work, as you can't save on the trial, and it throws up some odd error messages.

Olly may be right. Although my processor stabilises at 16C, I have no way of knowing if the sensor also stabilises. It's just my assumption that if the processor is heating to that temperature (it rises as it works harder, e.g. during live view) then it will also be heating the internals of the camera to a similar temperature regardless of external factors. I've read about people building coolers for their DSLRs but the bulky nature of the cameras means this is probably very inefficient. As I've said before, I'm not convinced the darks make any difference but given they are easy to take, I've applied them anyway.

I took 4 hours to process that image as I had to learn PixInsight from scratch. However, there are some amazing step-by-step tutorials and I re-ran the process on 7 images of M101 to see if I could remember what I was doing and that took much less time (and I completed more of the steps once I'd figured how to do masks). With practice and the use of batch processing (which I avoided until I knew what the processes did), I think it could be reduced to about an hour's processing for a target. Given I think the image is more than 3 times better for the effort (and I actually enjoy the processing), it's an hour I will enjoy.

I also learnt a new technique with Photoshop which uses the high-pass filter on a desaturated layer, then applied via a mask created by selecting a colour range. I tried it on the North America Nebula selecting the reds/pinks and it did sharpen the nebula, creating a little more "depth".

One question that's had me thinking today: given we are exposure limited, do you think we could image using filters? I'm guessing not except for the very brightest of DSOs like M42.

[wxsatuser]

If your using the 60D it has on sensor dark current suppression, darks are not needed.
You can also update the bad pixel map by invoking a sensor clean when the camera has stabilised.

I have tried with darks and without when using my 60Da and I could'nt see a difference.

[SteveNickolls]

I feel like a criminal after last night's Alt-Az imaging session. OK, I'll come clean and tell the whole story.

You have to remember everything was running well; I'd planned to set up extra early and like Ken on SGL had advised, I did the dark frames first. Alignment went swimmingly, first Vega then Regulus, return back to Vega and wait until any mount movement ceased. Vega remained bang in the centre of the eyepiece and none of the usual minor adjustments were needed. Tonight was going to be a steal.

Focusing too with the Bhatinov Mask went without a hitch. If I'm being really honest there was a little wind to spoil the mood and I had to wait a few minutes for the sky to darken once slewed to NGC 7000. At fifty seconds Live View was just a white-over but things got quickly better as the sun finally sank below the horizon.

Fifty frames later and how glad am I now that I decided to hedge my bets and next image M29. I wonder did I have an intuition?

Just before the witching hour I honestly thought I'd got away with it, no problems, no major hitches. I was soon packed away then gone like a thief in the night. The perfect imaging job.

Nemesis swiftly followed the hubris of the night before when, processing my images the next morning, a strange blob appeared on all the light frames. Oddly they were only on the first set of frames used for NGC 7000, M29 was fine. Whatever was the cause? The investigation didn't take long and I realised I hadn't got away with things at all, I'd been caught by Spider, man he'd been hiding in the dew shield all along! Here's the evidence-

It's a true story, honest. I'll post my M29 image soon :-)

Cheers,
Steve

 

[Herzy]

17 minutes ago, SteveNickolls said:

I feel like a criminal after last night's Alt-Az imaging session. OK, I'll come clean and tell the whole story.

You have to remember everything was running well; I'd planned to set up extra early and like Ken on SGL had advised, I did the dark frames first. Alignment went swimmingly, first Vega then Regulus, return back to Vega and wait until any mount movement ceased. Vega remained bang in the centre of the eyepiece and none of the usual minor adjustments were needed. Tonight was going to be a steal.

Focusing too with the Bhatinov Mask went without a hitch. If I'm being really honest there was a little wind to spoil the mood and I had to wait a few minutes for the sky to darken once slewed to NGC 7000. At fifty seconds Live View was just a white-over but things got quickly better as the sun finally sank below the horizon.

Fifty frames later and how glad am I now that I decided to hedge my bets and next image M29. I wonder did I have an intuition?

Just before the witching hour I honestly thought I'd got away with it, no problems, no major hitches. I was soon packed away then gone like a thief in the night. The perfect imaging job.

Nemesis swiftly followed the hubris of the night before when, processing my images the next morning, a strange blob appeared on all the light frames. Oddly they were only on the first set of frames used for NGC 7000, M29 was fine. Whatever was the cause? The investigation didn't take long and I realised I hadn't got away with things at all, I'd been caught by Spider, man he'd been hiding in the dew shield all along! Here's the evidence-

It's a true story, honest. I'll post my M29 image soon :-)

Cheers,
Steve

 

Pesky little buggers! I had a big moth fly towards my phone, the only source of light out there. I frantically tried to hit it away and I knocked my scope out of alignment.

[SteveNickolls]

Here's last nights M29 taken with the SkyWatcher 102mm Startravel Refractor, Synscan Alt-Az mount and Canon 600D DSLR. The image is made from x39 fifty second light frames combined with x50 dark frames, x50 flat frames and x50 bias frames. Frames stacked in DSS and processed using StarTools. The stars of M29 are set in a haze of nebulosity.

Cheers,
Steve

[SteveNickolls]

And here is part of the spider hijacked NGC 7000. I managed to crop out the part where the arachnid had left its shadow on the images. What's left is the top most part of the object. I think I will have to get something like a 200mm camera lens to do the object justice. StarTools didn't like the lack of data (there's only x39 fifty second frames at ISO 1600), plus x50 dark frames, flat frames and bias frames. Images taken using the SkyWatcher Startravel 102mm refractor, Synscan Alt-Az mount and Canon 600D DSLR. Images stacked in DSS and processed using StarTools.

Cheers,
Steve

Edited May 9, 2016 by SteveNickolls

[Nigel G]

4 hours ago, Filroden said:

Olly may be right. Although my processor stabilises at 16C, I have no way of knowing if the sensor also stabilises. It's just my assumption that if the processor is heating to that temperature (it rises as it works harder, e.g. during live view) then it will also be heating the internals of the camera to a similar temperature regardless of external factors. I've read about people building coolers for their DSLRs but the bulky nature of the cameras means this is probably very inefficient. As I've said before, I'm not convinced the darks make any difference but given they are easy to take, I've applied them anyway.

I took 4 hours to process that image as I had to learn PixInsight from scratch. However, there are some amazing step-by-step tutorials and I re-ran the process on 7 images of M101 to see if I could remember what I was doing and that took much less time (and I completed more of the steps once I'd figured how to do masks). With practice and the use of batch processing (which I avoided until I knew what the processes did), I think it could be reduced to about an hour's processing for a target. Given I think the image is more than 3 times better for the effort (and I actually enjoy the processing), it's an hour I will enjoy.

I also learnt a new technique with Photoshop which uses the high-pass filter on a desaturated layer, then applied via a mask created by selecting a colour range. I tried it on the North America Nebula selecting the reds/pinks and it did sharpen the nebula, creating a little more "depth".

One question that's had me thinking today: given we are exposure limited, do you think we could image using filters? I'm guessing not except for the very brightest of DSOs like M42.

I guess it depends on how much noise your chip has, my canons dark frames have about 6 hot pixels in, which are visible in the lights, the darks delete these. My astro webcam dark frames are full of noise, a few hundred hot pixels but that has an automatic add dark frame tab so darks are added to every light frame. But not as good for dso's as the dslr is.

My images without the darks have the hot pixels in which look like bright tiny red and white stars . The white pixels you could get away with  but the red pixels are as obvious as the ring nebula ☺

So darks are working for me I have read that you only need 12 to 20 darks though, same as flats. 

Nige.

[Filroden]

1 hour ago, SteveNickolls said:

Here's last nights M29 taken with the SkyWatcher 102mm Startravel Refractor, Synscan Alt-Az mount and Canon 600D DSLR. The image is made from x39 fifty second light frames combined with x50 dark frames, x50 flat frames and x50 bias frames. Frames stacked in DSS and processed using StarTools. The stars of M29 are set in a haze of nebulosity.

Looks like you have a strong gradient from the bottom. How good is the wipe tool in StarTools for removing this?

And that raises my next question: as altaz imagers, we have to deal with rotation. But that also means that when we stack images, any linear gradient that appears in each frame slowly becomes rotated through our stack created a non-linear gradient in the final stack. Does that mean we should be removing gradients from each frame before stacking?

[SteveNickolls]

40 minutes ago, Filroden said:

Looks like you have a strong gradient from the bottom. How good is the wipe tool in StarTools for removing this?

And that raises my next question: as altaz imagers, we have to deal with rotation. But that also means that when we stack images, any linear gradient that appears in each frame slowly becomes rotated through our stack created a non-linear gradient in the final stack. Does that mean we should be removing gradients from each frame before stacking?

Hi Ken,

The image had WIPE carried out on it, I think the gradient is there because there aren't enough frames to make the data good enough for ST to work adequately and you get blocks of off-colour and gradients appearing. Sometimes you can crop a larger image down and 'fool' ST into thinking the data is better than it is and you can then use modules such as COLOR properly. I put last night down to a learning experience :-)

In DSS field the stacked rotated images take up a 'bow tie' appearance over time on the master image but the software automatically rotates individual frames for you. ST then only has to remove gradients once.

Cheers,
Steve

[Filroden]

1 minute ago, SteveNickolls said:

Hi Ken,

The image had WIPE carried out on it, I think the gradient is there because there aren't enough frames to make the data good enough for ST to work adequately and you get blocks of off-colour and gradients appearing. Sometimes you can crop a larger image down and 'fool' ST into thinking the data is better than it is and you can then use modules such as COLOR properly. I put last night down to a learning experience :-)

In DSS field the stacked rotated images take up a 'bow tie' appearance over time on the master image but the software automatically rotates individual frames for you. ST then only has to remove gradients once.

Cheers,
Steve

What I mean is that DSS rotates based on stars located within the frame but the light gradient does not rotate, meaning it would be rotated as DSS de-rotates the stars...if that makes sense. So instead of each frame having a gradient from base to top, assuming an even light pollution from the horizon (but would still hold true for more complex gradients because of nearby lighting) when they get stacked, the gradient gets added diffently from each frame and creates a bow tie gradient which is probably much harder to remove.

[SteveNickolls]

Hi Ken,

I'm going to have a ponder and pass on that one then. I'm just about getting me 'ead round dark frames :-) Maybe someone else on SGL knows the answer to this one?

Cheers,
Steve

[Nigel G]

A quick question.  In StarTools which tab should I open my image with........., linear, was not Bayered or is white balanced ......linear,was Bayered, is not white balanced. ........modified and not linear ........ or .......I'm not sure. 

Nige.