Beginners, monochrome is fastest and easiest!

[ollypenrice]

Since I'm always arguing that mono is the fastest imaging system of all, I thought I'd set myself a challenge and produce a 2 hour image using one of our monochrome CCDs. These are large format, relatively low sensitivity Kodak chipped cameras. So here we have the Heart Nebula data captured recently with Gnomus using an F5 Tak refractor. I used just 2x30 minutes in Ha and 2x10 minutes per colour, so two hours all in. In keeping with the spirit of the excercise processing was done on the fly and the subs were not cherry picked. They were chosen at random.

It is not a great image but could you do this in two hours with a DSLR at F5? I'm tempted to say that I'll eat my head torch if you can (but there are some clever people out there so maybe I won't!)

Of course monochrome CCD remains expensive but it is so, so fast.

Olly

PS Here's the Ha. 2x30 minutes. There's a column I haven't fixed. Lazy boy!

 

 

[geoflewis]

Well there's little arguing with that....!! Awesome

Geof

[Alien 13]

I have a realy daft question, why when using a mono camera do you throw away photons by using filters? wouldn't it be better and faster just to shoot in mono, it would also be a better representation of what we see.

Alan

[ollypenrice]

2 minutes ago, Alien 13 said:

I have a realy daft question, why when using a mono camera do you throw away photons by using filters? wouldn't it be better and faster just to shoot in mono, it would also be a better representation of what we see.

Alan

When shooting in luminance you don't throw away photons and if you want to give a black and white image then that's the filter to use. It passes all the visible spectrum.

I can't speak for other imagers but the last thing I'm trying to do is replicate the eyepiece view. I'm interested in presenting things as we can't see them at the EP - which is to say in colour, above all.

As for other filters, like narrowband, the idea is to select light from a single source to isolate that source from all other light so that you see, for instance, only the ionized hydrogen and not all the other things around it in the view.

The choice of filter in solar imaging and observing allows you to select the depth into it's 'surface' that you see.

Olly

[Gina]

Absolutely, the hydrogen gas ionisation gets lost in all the other (brighter) light.  Unless it's very bright you just can't see it.

[alexbb]

Nice result, Olly! But 30 min subs will be pretty difficult at the beginning.

Alan, shooting narrowband allows you to image by using a not so good colour corrected scope (ie. achromat) and let's you select a narrow band of the light and filter the unwanted light pollution and glow. Also the stars' glow is smaller by using narrowband filters, but the combined colour of multiple narrowband images doesn't look natural. Anyway, Olly replied as I was typing. And Gina.

[ChrisLX200]

Have to agree with Olly here - a mono camera rules, and whilst my 16803 sensor is 'old hat' in terms of sensitivity by today's standards it can do this with a single 20min sub (no callibration - i.e., no flats, no dark, no bias - hence pretty mucky)

ChrisH

 

[ollypenrice]

11 minutes ago, moise212 said:

Nice result, Olly! But 30 min subs will be pretty difficult at the beginning.

Alan, shooting narrowband allows you to image by using a not so good colour corrected scope (ie. achromat) and let's you select a narrow band of the light and filter the unwanted light pollution and glow. Also the stars' glow is smaller by using narrowband filters, but the combined colour of multiple narrowband images doesn't look natural. Anyway, Olly replied as I was typing. And Gina.

I don't think that the 2X30 minute subs would be significantly different from 4X15 or even 6X10. I prefer long NB subs but for the purposes of this rough and ready demonstration this isn't a significant preference.

My main point was to scotch the idea that using filters is slower than using one shot colour.

14 minutes ago, Gina said:

Absolutely, the hydrogen gas ionisation gets lost in all the other (brighter) light.  Unless it's very bright you just can't see it.

Yes, the point being that filters cannot increase light transmission, they can only block such parts of it that you don't want. In processing, however, there would be no point in adding Ha if we respected the relative brightnesses of the captures in each filter. The Ha would always be fainter than the red so it would have no effect. But what we do is stretch the Ha harder because we can, the background having been held down more severely by the filter. We then add the Ha so that it is brighter than the red in places, allowing it to reveal new detail. Such new details are, therefore, real but not in a 'real' proportion with the other light sources in the image.

I was entirely satisfied that a 2 hour mono image would beat a 2 hour DSLR image but I must say that I was surprized by the signal strength in 2 hours.

Olly

[AKB]

1 hour ago, ollypenrice said:

There's a column I haven't fixed. Lazy boy!

Just for my edification... how WOULD you do that?

 

[parallaxerr]

2 hours ago, ollypenrice said:

It is not a great image but could you do this in two hours with a DSLR at F5? I'm tempted to say that I'll eat my head torch if you can (but there are some clever people out there so maybe I won't!)

Sounds like a challenge for us cheapo DSLR Alt/Azers!

[ollypenrice]

1 hour ago, AKB said:

Just for my edification... how WOULD you do that?

 

I'd use the line repair tool in AstroArt first but, since this is a broad dead column on an old camera, that would still leave a vague line. Then In Ps I'd make a copy layer and run Noel's Actions 'Remove vertical banding' a couple of times on the bottom layer. I'd then run the eraser down the column on the top layer. (This avoids letting the action affect other parts of the image.) It works perfectly and this is a beast of a column.

Olly

[almcl]

2 hours ago, ollypenrice said:

 could you do this in two hours with a DSLR at F5? 

Don't know Olly, could you send me two hours of clear sky, (can't remember when we last had even 1 hour without cloud), one of your Taks, oh, yes and your fabulously dark skies as well?  And I'd probably need to come back to Les Granges for some more image processing instruction, too!

The image below is not a patch on yours, I freely admit, but it required less than 20 minutes (IIRC - away from the notes just now) to obtain, which was all the time available.

I would love to do narrowband on a CCD, but with only about 1 night in 5 having stars here abouts I am not sure it's possible?

[ollypenrice]

1 minute ago, almcl said:

Don't know Olly, could you send me two hours of clear sky, (can't remember when we last had even 1 hour without cloud), one of your Taks, oh, yes and your fabulously dark skies as well?  And I'd probably need to come back to Les Granges for some more image processing instruction, too!

The image below is not a patch on yours, I freely admit, but it required less than 20 minutes (IIRC - away from the notes just now) to obtain, which was all the time available.

I would love to do narrowband on a CCD, but with only about 1 night in 5 having stars here abouts I am not sure it's possible?

If it's any consolation it's been bucketing down here for three days, Al! The sky will soon be empty, I hope!

Olly

[John78]

I can agree that mono is faster than rggb by an amount because you're not gathering the double g and you can bin the colours to speed up further... And I can agree mono almost certainly will be a more sensitive sensor and likely will be cooled.   Great advantages. 

 

My issue as a beginner is in Hertfordshire I'm sky limited to 2-3 minutes before orange/white out using an DSLR so it's going to be worse with a more sensitive sensor, NB is I think the answer?  I've tried a LP filter on a DSLR and it doesn't help too much really. 

 

I've got a mono camera now and lrgb filters on order but as a beginner I'm expecting needing at least Halpha filter before I need guiding...

[Ant]

What I was rather hoping for Olly, was a dSLR image from you as a comparison. 

Its not going to be a fair comparison using an image from somewhere in the UK, with less altitude, more humidity, more Light Pollution and a different scope.

I would be very surprised if you were wrong though - Mono never ceased to amaze me

Ant 

[Macavity]

I have not ventured far into classical imaging. Indeed perhaps resisted!
And, even with limited (colour) DSLR experience, I regret that now... Hey, 
uber-deep Video Astronomy and "Ha-Solar" have boredom thresholds!

As implicitly noted: Once even a modest large format CCD is put in a posh
housing and re-branded for "Astronomy", we're talking cost of a (rubbish)
second hand car or a new kitchen. Or maybe I'm being a TAD unfair... 

I REALLY VALUE people who present actual measurements of stuff.
The UK rarely allows consistent enough conditions for such things.

[Gina]

I have tried both from the same location and mono wins hands down.

[Knight of Clear Skies]

It's a great result when viewed on my screen, any noise and defects only really show up when zooming in a bit.

4 hours ago, ollypenrice said:

It is not a great image but could you do this in two hours with a DSLR at F5? I'm tempted to say that I'll eat my head torch if you can (but there are some clever people out there so maybe I won't!)

I think your head torch can rest soundly, you've hardly set a fair challenge there Olly.  As some scot said, ye cannae argue with the laws of physics. The bayer matrix penalty is too much to overcome on a narrowband target, an OSC camera will put up more of a fight on a broadband target but even there lum + rgb will do deeper more quickly. Mono is unquestionably technically superior.

What a DSLR does provide is a capable astro-cam at a relatively low cost. The best results will be achieved by respecting its limitations by either mating it with fast optics or choosing targets of suitable brightness. Here's my 38 minute Heart for comparison:

Not a patch on the image above, the Ha signal is much weaker despite shooting at f3.5 and the nebulosity lacks definition. However, it was shot with a 50-year old camera lens that cost me under twenty quid. With careful second hand shopping a comparable imaging rig (Eq3-2, modded Canon 1100D, lens, intervalometer) could be put together for less than £400, considerably less than an Astrodon 3nm Ha filter. This is where DSLRs really shine.

If we're talking about beginners, there are times a simple rig like this wins. I was aiming for 2+ hours  on this target but the weather intervened, if I'd have been guiding and using a mono camera I might not have got anything useable that night with the longer setup time to consider. Once the learning curve has been overcome and a decent gap in the weather arrives a mono guided setup will sprint away, but for a beginner that can be a bit of a hill to climb, especially in UK weather.

[ollypenrice]

I suppose a head torch might make a light snack....

Olly

[ChrisLX200]

Olly wasn't suggesting 'it's got to be mono or nothing', just that if you want something to aim for and perhaps in doubt as to which would be better (and faster) mono or OSC - then mono is the way forward. It IS more expensive with needing to buy filters etc., no doubt.

ChrisH

[Ouroboros]

My unmodded 450D DSLR certainly couldn't compete with Olly's marvellous image.  But then aren't we comparing chalk and cheese here? A more appropriate comparison might be between mono and OSC CCDs. Even so I expect mono would win given all the right conditions.  But Knight of Clear Skies makes a good point too with his lovely image of only 38 minutes. A very satisfactory result.  His points about beginners, the learning experience gained with DSLRs plus getting satisfactory results at a reasonable  cost with limited sky time are well made. 

[spillage]

I would be very interested in seeing the price comparisons of the different set ups. Leaving out the mount cost and scopes.

[ollypenrice]

2 hours ago, Ant said:

What I was rather hoping for Olly, was a dSLR image from you as a comparison. 

Its not going to be a fair comparison using an image from somewhere in the UK, with less altitude, more humidity, more Light Pollution and a different scope.

I would be very surprised if you were wrong though - Mono never ceased to amaze me

Ant 

Yes, it would be instructive. I have little experience of processing DSLR images and even less of capturing them but perhaps someone can come to the rescue?

Olly

[John78]

31 minutes ago, Ouroboros said:

My unmodded 450D DSLR certainly couldn't compete with Olly's marvellous image.  But then aren't we comparing chalk and cheese here? A more appropriate comparison might be between mono and OSC CCDs. Even so I expect mono would win given all the right conditions.  But Knight of Clear Skies makes a good point too with his lovely image of only 38 minutes. A very satisfactory result.  His points about beginners, the learning experience gained with DSLRs plus getting satisfactory results at a reasonable  cost with limited sky time are well made. 

This point is one I don't really get - if you're going to fork out a grand plus on a astronomy specific cooled camera why would you even consider a OSC version, who buys them and then why??  How is it even a marketable proposition?

 

Fully agree people use DSLRs because most people that would consider this hobby already have one, so its logical to use it while dipping ones toe so to speak.

[geoflewis]

7 minutes ago, ollypenrice said:

Yes, it would be instructive. I have little experience of processing DSLR images and even less of capturing them but perhaps someone can come to the rescue?

Olly

Hi Olly and others,

Here is a link to my version of the Heart and Soul nebula taken a few years ago with my moded Canon 600D (T3i) and a Nikkor ED 180mm manual lens that I picked on eBay for £105.

http://www.astrobin.com/126058/0/

Full capture details are below the image in Astrobin, but you'll note that I blended Ha data captured with an Astronimik EOS clip in filter with the RGB data for a total of over 5.5 hours integration.  Please note, however, that the data was collected from my very light polluted former home in suburban Surrey - very different skies to that which I now experience in rural Norfolk.

I was also much less experienced at astrophotography, but I think the contest is over the comparison is stark - mono CCD coupled with superior optics in the hands of an expert wins hands down

Cheers, Geof