alan4908

3 hours ago, MarkAR said:

Lovely pair of galaxies. Superb image detail and colour.

Thanks    -  I was pleased with the amount of detail - this was helped by the creation of a so called "super luminescence"  which increased my SNR for the lum without impacting detail.  This in turn allowed me to perform a stronger deconvolution, thereby extracting more detail.

Alan

NGC4725 is the brightest member of a galaxy group in the constellation Coma Berenices and is about 40million light years distant and 130,000 light years in diameter. The structure is somewhat unusual, consisting of just one spiral arm which is tightly wound around the core and can be followed for about 1.5 revolutions. The spiral arm consists of dust and gases including bright blue stars and pinkish Ha regions which indicate star forming regions. Towards the center, much older, yellow stars can be seen. The galaxy is classified as a Seyfert Galaxy, indicating that the center contains a supermassive black hole.

The smaller galaxy on the right side is NGC4712 is within the galaxy group but is at the much greater distance of about 200million light years.

The LRGB image below represents 12 hours integration time and was taken with my Esprit 150.

Alan

LIGHTS: L:21, R:13, G:20, B:18 x 600s; DARKS:30, FLATS:40, BIAS:100 all at -20C.

On 07/05/2020 at 23:27, Adam J said:

I am having some issues with setting up my filter offsets on my Esprit 100 I keep ending up with slightly bloated red channel when I average focus based on HFR.

I would appreciate it of anyone with an Espirt 100 could share their offsets for comparison, I know mine will be different so its just a wet finger in the air thing.

Mine are currently set as:

Lum = 4

Red = 7

Green = 0

Blue = 0

 

Thanks,

Adam

Hi Adam

Whilst I don't have an Esprit 100, I do own an Esprit 150 which is set up for automated imaging using filter offsets.  I explored the details of this a couple of years ago and understanding the theory a little more greatly improved my results. So,  you might want to take a look at this post: 

On 05/05/2020 at 09:41, alan potts said:

Really lovely image there.

Alan

Thanks Alan 

14 hours ago, Whirlwind said:

Hmm I think they should be more pink in the main galaxy.  From the larger images they appear to be star forming regions and hence you'd have some red from the emission nebula as well as the hotter stars.  The very intense blue would be representative of very hot stars and relatively they are rare.  As for the Franke image I'd have the same argument.  The smaller galaxies are too blue.  The cores of galaxies are generally old and hence cooler.  Such intense blue is generally only seen in galaxies that are interacting (at least nearby anyway) and still in the tidal tails rather than the core.  The core of them would be more akin to M109 pinky blue at the edges and cooler towards the centre (and if it is an elliptical then cool all the way).  I've included a basic photoshop image of the areas.

Of course it is artistic licence and still an excellent picture but I just find the intense blue areas 'distracting'.

Thanks for your detailed comments.

In acquiring the image, I did wonder if I could detect some star forming regions, so in acquiring the image, I also decided to try to capture some emission data via my 3nm Astrodon Ha filter. Unfortunately, even after 7.5 hours (15 x 1800s), the resultant stacked Ha image just looked like a grainy version of the stacked red channel. So, unfortunately, no more detail, only noise was revealed. I therefore decided not to use the Ha data.  I should point out that I'm not implying that there aren't any star forming regions in M109 - it is just that I didn't detect any  

On a general point, it is quite interesting trying to compare my image with others, high resolution M109 images seem to be in short supply. 

10 hours ago, MarkAR said:

I think the only difference between Alans' and Block/Gendler is very slightly more colour saturation.  Nothing to worry about at all.

 

Thanks for the comment !

Alan

13 hours ago, MarkAR said:

Lovely image especially as you've picked up the disc formations of the tiddlers.

Thanks for the comment.   Yes, I was quite happy with the amount of detail that I managed to acquire.

11 hours ago, Whirlwind said:

It's a lovely image.

Can I ask though what's happened with the blue element of the processing? It seems to make the image look a bit 'spotty' and there are areas that have a very blue tint (e.g. PGC37700 / PGC37621)

Thanks for the comment. 

On your blue processing point, I believe the blues are an accurate representation.  For instance, take a look at these images from three accomplished astrophotographers:

Adam Block - http://www.caelumobservatory.com/obs/m109.html 

Robert Gendler - http://www.robgendlerastropics.com/M109.html

On the small blue stars and the blue tint of the small background galaxies, these also appear accurate - for instance,  have a look at this APOD from Bob Franke:   http://www.star.ucl.ac.uk/~apod/apod/ap130523.html 

6 hours ago, geoflewis said:

An excellent image

Thanks Geoff !

Alan

My first attempt at M109, a galaxy located in Ursa Major which is about 55 million light years distant. In the image below you can also see quite a few other background galaxies - the ones marked PGC37553, PGC37700 and PGC37621 have recession velocities very similar to M109 and are classified as dwarf companion galaxies.  

The LRGB image below represents 16.5 hours integration and was taken with my Esprit 150.

Alan

M109

M109 (annotated)

LIGHTS:  L:37, R:21, G:23, B:18 x 600s. DARKS: 30, BIAS:100, FLATS: 40 all at -20C.

8 hours ago, Davey-T said:

Nicely captured and processed Alan, another of my perennial unfinished projects 😂

Dave

Thanks Dave !

Alan

On 30/04/2020 at 08:28, carastro said:

Excellent result and processing.

Carole 

Thanks Carole 

12 hours ago, Jkulin said:

Hi Alan,

Of course, sometimes you want to use a different mask for one area and then another masks to work on another are etc. The work around for me is to create a black mask and then apply that to a range mask to block out specific areas by cloning from the black mask, but rather than make a mask up like that it would be nice if you could make a specific mask up for one area, then apply an exisitng different mask to a different area and so on and then apply the changes.

Hope that explains things a little better.

Hi John

Yes - masks are interesting objects to experiment with..

In Pixinsight, I found that the free GAME script (http://www.skypixels.at/pixinsight_scripts.html) is very flexible, allowing you to create "elliptically holes" of specific sizes in your black mask at specific locations. 

Alan

11 hours ago, Jkulin said:

Thanks Alan, Yep you hit that on the head, have you ever wished you could apply 3 or 4 masks at the same time so that you can work on a specific area?

I have got the galaxy virtually as I want, but need to then concentrate on the other areas, I will get there but doubt that it will look as good as yours.

Good luck with your processing, I'm sure you will get there  !

By the way, I didn't understand your comment on applying multiple masks simultaneously, could you elaborate ?

Alan

8 hours ago, Jkulin said:

That's Lovely Alan, I have been doing the same image and have about 20 hours on it so far, there is so much going on in the image, I have processed it about 5 times so and I'm still not happy with the outcome.

How did you find it to process?

Thanks for the comment John 

I found it quite difficult. The main problem for me was the background and the starfield, rather than the galaxy.  Specifically:

1.  There are some quite bright stars around the galaxy which if you stretch them at the same level as the galaxy,  become too bloated.  I resolved this by stretching some of these separately and then blending them into the image.

2.  Since I image in non-ideal conditions (eg the UK), I often obtain red halos around blue stars, this arises from the FHWM of the red stack being slightly larger than the blue stack. I resolved this problem by creating a halo mask around the stars in the red channel and then applying an erosion filter to only that channel.  I did this in Pixsinight but you can perform the equivalent task in Photoshop. 

In general, I'd suggest you examine your five results and decide which parts of the image you like and which you don't for each of your five attempts.  I sometimes find that processing the main object and the background separately  and then blending the results can give a better overall result.

Alan

21 hours ago, Spitfire said:

Nice Image.

I enjoy looking at these unusual galaxies.

Geoff

Thanks for the comment Geoff. 

21 hours ago, MarkAR said:

That's a cracker of a galaxy. Superb image.

It looks like that at sometime during formation it was knocked off its initial axis giving a twist to the dark band.

Thanks - yes, it looks like it has gone through a lot - also the interaction with its companion galaxy is interesting. 

21 hours ago, Knight of Clear Skies said:

Superb image of a candy-wrapper of a galaxy. Personally, I'd consider cropping off the left hand side of the image as there is not a lot going on over there.

Thanks - on the cropping front, I did consider a much tighter crop  but this time I opted for the interesting object suspended in space look.  

17 hours ago, Brian28 said:

that very nice Alan 👍 

Thanks Brian

Alan

My first attempt at NGC3718 which lies at a distance of about 49 million light years from Earth. 

It's a very unusually looking galaxy, featuring a twisted dust lane in the central region.  To the right you can also see the companion galaxy NGC3729 which, occurring to radio measurements, appears to be interacting with its larger partner.  At the top of the image, Hickson 56 can be seen, a grouping of five small galaxies that are estimated to be about 390 million light years away. 

The LRGB image represents just under 16 hours and was taken with my Esprit 150.

LIGHTS: L: 35, R:23, G:20, B:16 x 600s, DARKS:30, BIAS:100, FLATS:40 all at -20C.   

1 hour ago, barkis said:

I was looking at focus max 4 to compliment my newly acquired Lakeside focuser.
After visiting ccdware's website.  (having had to exclude their website via my Malware Prog.owing to a Trojan warning. ) 
I was a bit staggered by the price of $129. Not sure the advantages of the software will justify that price, 
which will be around £105 I reckon. I'm not a mean Git, so If anyone using it will give it a 10/10,
then I will re consider.

Ron.

I use the freeware version of FocusMax in conjunction with Maxim DL and ACP Expert and find it gives excellent results, so I've never had the need to get the paid version. 

The main reason I suggest using FocusMax is that it works out the focusing from a defocused position, which helps to combat the effects of seeing.  To further reduce the impact of seeing, I'd also recommend you choose the FocusMax option of convergence which takes (say) 5 exposures at the defocused position and attempts to pick the best one.  Seeing will also be minimized by picking a focus star near the zenith, since this minimizes the amount of atmospheric distortion.  If you want to best possible focus then you should also look at the various FocusMax tutorials and select a focus star and exposure that puts you on the linear part of your camera. It is also quite fast, in my system, it takes a total time of about 80s to achieve focus, with the slower but more accurate option of convergence selected.

On the downside of the freeware version, I seem to recall there is an issue with using the FocusMax acquire star feature,  this doesn't impact me since I use ACP Expert to select the focus star.

Alan

SH2-115 is a faint emission nebula in the Cygnus constellation about 7500 light years distant. It is normally imaged in narrowband, however, since I prefer natural looking colours, I went for a LRGB composition with an Ha blend into the red and lum channels.  The image below represents about 17 hours and was taken with my Esprit 150.

I encountered an interesting challenge in the processing stage of the above image in that I discovered that I had also acquired high levels of scattered light from an out of field star. These rays appeared in all the Lum, Red and Green subframes.  Having analysed the likely candidates in the direction of the rays, led me to the conclusion that the most likely cause was the star Deneb, reflecting off some surface in my scope. I occasionally encounter this problem, but this was extreme, presumably due to the very high relative brightness of Deneb compared to the nebula.  On the good news side, the scattered light was not evident in the Ha captured by my 3nm filter and was only just visible in the red data. So, after Pixsinsight and PS manipulation, I think I've managed to reduce this effect to acceptable levels. 

Alan

LIGHTS: L:9, R:22, G:11, B:17 x 600s; Ha:14 x 1800s; DARKS:30, BIAS:100, FLATS:40 all at -20C.

22 hours ago, Brian28 said:

Hi Alan , don’t you think it’s amazing just how far these targets are from us and it’s hard to comprehend , but we can take pictures of them ..  

it’s a cracking shot 👍

Hi Brian

Thanks for the comment 

Yes, I find it amazing how amateur equipment can capture such faint and distant objects in such detail. I guess it is primarily due to the advances in digital cameras and digital signal processing. 

Alan

Located in the constellation Bootes, approximately 52000 light years from Earth, lies the globular cluster NGC 5466. It is designated as a class XII cluster, meaning that it has relatively non-concentrated stars towards the core compared to a class I cluster.  This last fact starting me wondering if my scope would be able to resolve the "gaps" in the central core...... note also the various background galaxies. 

The LRGB image below was taken with my Esprit 150 and represents just over 9 hours integration time.

Alan

LIGHTS: L:12, R:17, G:10, B:17 x 600s, DARKS:30, BIAS:100, FLATS:40 all at -20C.

On 25/03/2020 at 07:41, Laurin Dave said:

Very nice, certainly looks Much better in LRGB than my attempt in HOO. Good framing too

Dave

Thanks for your comments Dave.  The LRGB image was improved by my first attempt at creation of a super luminescence (a noise weighted result of the individual L, R, G, B stacks - my RGB data is binned 1 x 1 so, it increases SNR without decreasing detail).

23 hours ago, gorann said:

Like you I prefer RGB or images with a plaette looking like RGB even with some NB added, and you clearly succeded! Great image!

Thanks Goran 

17 hours ago, alan potts said:

Keep looking at this, so so nice, one of the best images of this I have seen!!

Alan

Thanks Alan ! - apart from the superlum creation (mentioned above) I was also experimenting with a couple of new PI techniques that I also recently learnt from Adam Block's PI tutorials ( https://adamblockstudios.com/) - the first was to boost nebula contrast via the fuzzy logic script (LocalFuzzyHistogramHyperbolization) and the second to boost the blue contrast in the nebula via a specific Adam Block technique.

Alan

18 hours ago, alan potts said:

That is a lovely shot Alan, one I should try and get closer up on with my longer scope. Like the way you have framed it too.

Alan

Thanks Alan. Yes - it seems a very good target with my field of view, I was also somewhat pleased on the tadpole details.

15 hours ago, MarkAR said:

Lovely image, I think you've nailed the natural colour balance.

Thanks for the comment 

Alan

My first attempt at the Tadpole Nebula (IC410).  

Located in the Auriga constellation, the nebula is about 12000 light years distant and is approx 100 light years across.  The red tadpole like objects are believed to be  about 10 light years across and consist of dust and gas that have been shaped by stellar winds. The nebula also contains an open cluster (NGC1893) that contains newly born stars that are estimated to be only 4 million years old (in the center of the image and a little to the right).

Since I prefer natural looking colours, on the acquisition side, I decided to go for an LRGB image with the details enhanced with some narrowband Ha data.  The image was taken with my Esprit 150 and represents 16 hours integration time.

Alan

LIGHTS: L23, R:19, G:15, B:18 x 600s, Ha: 7 x 1800s, BIAS:100, DARKS:30, FLATS:40 all at -20C. 

18 hours ago, ngc1535 said:

Alan,

 

Great job on the use of the technique. I appreciate you taking it to heart. As I mentioned in my tutorials on this- even if you do not like outcomes of combinatorial means of processing an image (I used this "trick" as part of a larger thing to de-emphasize stars)- sometimes the individual small methods are useful in and of themselves. 

-Adam

Thanks for the comment Adam 

Alan

22 hours ago, Adreneline said:

An awesome result Alan - the time and effort invested has really paid off. Love the colours and the clarity of the whole image.

Excellent!

Adrian

Thanks Adrian 

18 hours ago, Sunshine said:

Is that ever beautiful! one can stare into such an image and get lost in all the detail, such fine points of light.

Thanks  

The open cluster M37 contains almost 2000 stars and is spread across 20 light years. Most of the stars are young blue/white but it also contains red giant orange suns which provide considerable colour contrast.  I first imaged M37 a couple of years ago but I decided to add to the data since I was never entirely happy about the quality of the some of the sub-frames.  I also decided to try out some of my newly learnt stellar processing techniques to improve the data which I describe below for anyone that might be interested. 

Since I often image in non-ideal conditions, I sometimes find that the red stacked channel has a larger FWHM values than the blue or green channels, if I combine this data to obtain an RGB image. the result is a red fringe around the stars. For blue stars, this is particularly apparent and creates magenta halos. This time, I decided to shrink the red channel via a ring mask using PI's erosion filter.  The ring mask protects the star core, minimizing damage and core dimming.  The main issue is generating a good ring mask which captures the majority of the red fringing. After watching one of the Adam Block's Pixinsight's tutorials ( https://adamblockstudios.com/) on how to de-emphase stars, I decided to apply a technique he recommends.  Basically, you first create a star mask which includes all the stars and all the halos. This mask should be white across the star and halo and slightly feathered around the edges.   Having done this, you then subtract from this the Red channel lum information to create the ring mask. The reason this creates an accurate ring mask is that the lum data contains accurate information on how the light profile various from the stars center. So, for example, at the stars core, the star mask will be close to 1 (in PI everything is normalised to 1), whilst the lum information will also be close to 1, so if you subtract one from the other you end up with something that is close to 0 (eg black) at the core.  Thus, at the core you will be protecting the star's core almost 100%. Outside of the star mask (eg outside of the halos) you will have 0, whilst in the lum channel you might have 0.2 (say representing a non-stellar structure), if you subtract 0.2 from 0 you get 0, since you cannot have negative values in PI, so outside the star mask the ring mask will be 0 eg black. Within the halo, the ring mask will mimic the stars halo hence generating an accurate ring mask.   

The LRGB image below was taken with my Esprit 150 and represents just over 15 hours integration time.

Alan

LIGHTS: L:23, R:26, G:23, B:21 x 600s, BIAS:100, DARKS:30, FLATS:40 all at -20C.

I had a look at your data and used Pixinsight and Photoshop to process the result (below). As you can see you've captured quite a lot of detail. 

On the vignetting issue this seems to be mainly in the RGB data, your Lum data is much flatter. I eliminated both with the use of Pixinsight's DBE function - you can do a similar function in PS but you will require the use of the plug-in Gradient Xterminator. 

I also noticed that your lum data is very slightly misaligned with the RGB data, so I realigned this to get better stellar profiles.

Alan

On 22/02/2020 at 11:32, vlaiv said:

I'm having difficulty understanding their explanation, some of the things they've written don't make much sense to me. I'll outline what confuses me, maybe someone will understand and explain to us what they meant so we can get to the bottom of this green color in the image.

So far, so good - I agree completely, if you want to document true color of the object - you can, and same as them, I object the notion that "color is arbitrary" in astrophotography. It can be arbitrary - but by choice only.

Emphasis on last sentence is added by me as it is root of my misunderstanding of what they are saying. They say that they want to exclude human vision component - that is ok, light reaching sensor is physical thing and as any thing in nature that we measure - we should exclude our subjective sense of it.

This is where things go south ... In introduction we are talking about measurement and we are excluding notion of human vision and such, and yet tool itself does - what they describe as white balance and most of document is about choosing reference white balance value.

Here is the thing - white balance is directly tied to human vision and perception. Absolute color spaces like CieXYZ does not have a white balance. It does not need white balance. White balance is used to define how color of particular object would be perceived by observer under certain illuminant. Our brain is funny thing. In an environment where we don't have pure white color - we choose closest color and that becomes white balance reference for our brain. All other colors in that scene are perceived "shifted" in hue to match that white point. Our brain does a bit of color balancing - although we have same spectrum - we perceive color as being different.

Astronomical images don't need white balancing in this sense - this is typical sense of daytime photography - we do white balance to adjust colors and convert our perception from environment that image was taken in to environment that image is viewed in. This is why we have different presets in cameras - like sunny, cloudy, incandescent light, fluorescent light, etc ... to tell the "camera" what was illumination like and then camera will convert that to "standard" viewing conditions.

In astronomy we don't have illuminant - we have sources of light and those don't depend on if it is sunny or cloudy day or we are using artificial illumination. No white balance is necessary or wanted.

What we want to do in order to produce what we colloquially call color balanced image is color space transformation. From raw tristimulus values produced by our camera sensor - to some standard color space tristimulus values. One can either choose to perform conversion to CieXYZ or to sRGB Linear - as there is well known linear transform matrix between the two. For final color that is displayed on our computer screens we need to do sRGB standard gamma correction - and voila, we will get true color, or rather - we will see on our computer screen closest representation of that particular color.

If we don't want to go as far as display - we can stop at CieXYZ value - that describes color well enough and is standardized, or we can choose to represent color in some other "color space" like BVR from UBVRI where we would use BVR filter response as matching functions instead of XYZ matching functions of CieXYZ color space).

What we should not do - is take tristimulus value that we have - arbitrary assign that to RGB and then wonder why such RGB triplet is green when displayed on the screen.

Back to the actual color of that thing:

We have R_raw, G_raw and B_raw to be (1, 1.06, 1.03) and this is our starting point - we have camera, I suppose it is Starlight Xpress Trius SX-814, and we have Astrodon RGB filters that produced these values?

Hi Vlad

I thought you might be interested in seeing the Pixinsight screen show (below) which I've taken with the cursor hovering over part of the green blob located at x= 51 and y = 40. The image is after I've performed DBE but before any PCC. 

This shows what happens to the linear RGB values as they are put through the non-linear stretching function (called Histogram Transformation in Pixinsight). So, for example, the red value before the stretch is 0.0066  and goes to 0.48 when it is stretched. 

If you make a table of the values you get:

So, at the linear stage the green blob is 8% more peaky than the red whilst introducing a non-linear stretch makes the Green component 18% more peaky than the red. At this point it looks green. This is without any increase of saturation, application of PCC etc.  

In subsequent processing I would boost saturation, perform noise reduction etc to create a final image, these steps further increase the differences between the values (in my case the final image as a green component that is 60% more than the red component.  

My point is that even a very small percentage differences when in the linear stage can lead to very large percentage differences in the non-linear stage. 

Alan

screen shot

7 hours ago, vlaiv said:

Do you have any idea of what "units" PCC is in? Or rather what color space it is in?

Here's some documentation of the Pixinsight Photometeric Color Calibration tool which might help answer your question: https://pixinsight.com/tutorials/PCC/index.html

7 hours ago, vlaiv said:

I wonder how almost equal values in red green and blue (green being only 7% higher and red and blue equal) can suddenly change to red being 33% less than both G and B?

I presumed this was the consequence of the various non-linear operations performed between the linear to the final processed state. 

Alan