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alan4908

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Posts posted by alan4908

  1. 11 hours ago, MartinB said:

    A proper soap suddy bubble Alan and nice and smooth thanks to the time you've given it.  Excellent!

    Thanks Martin. :smile:

    Yes, the extra time definitely helped with the bubble definition, although I still struggled getting good star colours. I think I need more practice.

    Alan

  2. I thought some of you might be interested in seeing an odd looking artifact in one of my recent images of the bubble nebula (see below). 

    At first, I thought this was due to incorrect settings within Pixinsight's Winzorised stacking algorithm. However, on examining the individual subs everything was OK - no artifact, just a star.  On closer examination of the individual subs,  I noticed that the star sometimes appeared clearly and sometimes appeared hardly at all.  So, I decided to see if the free ware program Aladin (https://aladin.u-strasbg.fr/ ) could identify the star. Plate solving the object in Pixinsight allowed me to locate the RA and DEC co-ordinates of the artifact (23 20 43.535, +61 14 43.54), after typing these into Aladin it turns out to be the variable star V*MOCas of Mira Cet type.  Since I gathered the data over many months, I presume the star was varying over this period and hence confusing the stacking algorithm and creating the artifact.

    Alan

    temp_artificat.jpg.c8d8c3317b4d80ca75bfa1059cb7c149.jpg

     

     

    • Like 3
  3. In an effort to improve on my image of the Bubble Nebula from a few years ago, I decided that my existing data needed a longer integration time...... so at a total integration time of just over 26 hours here's the result.  The image, taken with my Esprit 150, is an LRGB rendition with an Ha blend into the Red and Lum channels.  I was particularly interested in seeing how much detail I could extract on the bubble itself, so I decided that it looks best cropped. 

    Alan

    439212506_33.Finalcrop.thumb.jpg.20d2072de1e0a492d9670fc2cff992bb.jpg

     

     

    LIGHTS: L: 33, R: 27, G:27, B:23 x 600s, Ha:16 x1800s, BIAS:100, DARKS:20, FLATS:40 all at -20C. 

     

    • Like 16
  4. On 17/10/2019 at 23:21, Ken82 said:

    Normally using pixel math in pixinsight i dont have any issues combining rgb with ha but on this occasion its not working as well as i would like. Ive followed the procedure as normal from the light vortex tutorial but still not great. Any guidance would be really appreciated.

    Thanks Ken 

    Both images are stacked and have had background extracted but no processing. 

    HA

    https://drive.google.com/file/d/1z5Ufk2hq4QdP2TgYl-wBSCcCSquaGJqD/view?usp=sharing

    RGB

    https://drive.google.com/file/d/1OUOwLHKNG8apvbVV4fCqx2jaDuuu_Dca/view?usp=sharing

    I tend to follow the process steps as advised by Adam Block's PI tutorials  - see https://adamblockstudios.com/categories/PixInsight if you want to watch a video of all this. 

    1. Align Ha image with the Red channel of the RGB image

    Given that your Ha data is actually encoded as RGB, you first need to extract the Lum. To do this correctly, apply RGBworking space, with all the parameters set to 1 to the Ha image and the RGB image. Then extract the CIE L* from the Ha (RGB) image and use channel extraction to extract the Red channel from the RGB image.   Now apply star alignment to the Ha (Lum) and the Red channel, taking the Red channel as the reference.  You now have unstreched but aligned Ha and RGB images.

    2. Make stretched versions of the Ha (lum) and RGB image

    Use the STF and HT functions until you are happy with images - I just used the auto stretch function.

    3  Blend the Ha and RGB red channel together

    Before you do this you need to manipulate the Ha data by:

    a) To make this process a little easier, perform a linear fit on the Ha information using the red channel as the reference. This makes the intensities of the two images similar, making then easier to blend together. 

    b) Given that you don't wish to put the Ha into the stars, one option is to use PI's starnet++ to make a starless image of the Ha which you can do by simply applying starnet to the stretched Ha image. 

    c) Run TGV denoise on the Ha starless image - this is to minimize the chance of raising the noise floor of the red channel when you do the subsequent blending.

    d) You now need to create an image that only has the brightest parts of the Ha information.  This involves black clipping the Ha data so that you don't end up creating a red cast on the RGB data. This is the critical step in the process.  

    e) You now have two images: a starless Ha black clipped image which only has the brightest parts of the Ha image and the Red channel of the RGB image.

    f) Use the script Blend script (download at https://www.skypixels.at/pixinsight_scripts.html) to blend the two images together you end up with an Ha enhanced red channel. Select the screen blending mode on the script. 

    4. Recreate the RGB by taking the extracted Blue, Green and Ha enhanced red channel. 

    You are done.

    From your data, I ended up with the following blended image + after application of SCNR green. I didn't do any subsequent processing eg noise reduction/colour enhancement since I thought you would want to see if just with the Ha blend (which looks quite good to me). 

    A few minor points that are nothing to do with Ha blended that you might find useful - these only show up if you zoom in.

    1. If you look at the Fits header information of the source images, something appears to be incorrect with your image integration. On the RGB image you appear to have zero rejected pixels from the integration of 10 images.  you can see the effect of this if you pixel peek eg a satellite trial is visible.  You should be ending up with 1 to 2 %. On the Ha image you have more than 10% rejection, from a stack of 42 which seems a bit aggressive to me. 

    2. Overall your stars look good but on the right hand side that are elongated, I presume this is camera tilt. 

    Alan

    RGB_ha_R_blend_scnr_green.thumb.jpg.1a6e4c25659840e27699e9c3838c7179.jpg

     

     

     

    • Like 2
  5. The galaxy NGC 4216 is located in the Virgo constellation and is approximately 55 million light years from Earth. It is one of the largest and brightest galaxies in the Virgo cluster. It appears at an inclination of 89 degrees such that its core is partially obscured by its outer dust lanes.  Numerous other background galaxies can also been seen in the image below, some of which I've annotated below.  

    Due to the poor UK weather, this object disappeared below my local horizon before my imaging run was complete, however, I'm reasonably pleased with the result. 

    The LRGB image represents 10 hours integration time and was taken with my Esprit 150. 

    Alan

    760676497_23.Final.thumb.jpg.64c1e9d1a6129c9592f7d73ef41818de.jpg

     

    880273071_24.annotated.thumb.jpg.f2a29645835d213543b1fe1ea7cd8ad7.jpg

    LIGHTS: L: 18, R:12, G:15, B:15 x 600s; DARKS:30, FLATS:30, BIAS:100 all at -20C.

     

    • Like 14
  6. 12 hours ago, Grierson said:

    Perhaps the following is naïve comment. My current setup is a SkyWatcher ED80 on a belt modified HEQ5 with either a ZWO 294 or ZWO 1600. (Both CMOS cameras) Having watched SharpCap's Robin Glover's presentation where he recommends lots of short subs rather than fewer longer subs I get to thinking that running a guide 'scope and software on my rig does not contribute significant benefit.  I typically take 30-40 x 180sec. subs.

    All the control gear, ASIAIR, power distribution, focuser and guide 'scope are mounted on the ED80 and I WAS giving some thought to lightening the load by fitting an OAG. But then I hesitate and wonder if guiding on my setup is worthwhile. I should say that clear nights in recent times have not allowed any experimentation to answer my own question but on the occasions when I have not guided I see reasonably round stars. I wonder what more experienced imagers think.  

    It is an interesting question.

    When I started astrophotography I noticed that with my SW ED 80 on an NEQ6 mount (non belt modified) I found that imaging at 1.4 arc seconds/pixel that I could get acceptably round stars (eg star aspect ratio < 25%) with up to 120s seconds exposures.  However,  I also discovered that for my site taking lots of short exposures significantly limited me in imaging faint objects.  After a bit more investigation, I discovered that my optimum broadband exposure sub frame length for my site/set up was around 600s.  A detailed discussion this subject can be found in the book The Astrophotography Manual by Chris Woodhouse - basically more light pollution lowers this figure.   I 'd therefore suggest you determine your optimum exposure time for your particular site/set up. 

    In terms of improving your mounts performance, I'd suggest you quantify the situation by firstly determining your maximum load weight for imaging and then weighing the sum of all your attachments (dovetail bar, guide scope, camera etc).  If you well within the mounts load limit, then you are unlikely to see any performance improvement. 

    Alan 

  7. 18 hours ago, MartinB said:

    These small galaxies are such a challenge and this has been beautifully captured and processed.

    Thanks Martin - yes, they do make it a little more challenging. FYI I would have liked to gather a little more data on this one but it disappeared below my local horizon before my normal integration time was complete.

    18 hours ago, ollypenrice said:

    Ooh yes, that's a thriller! Lovely stuff.

    Olly

    Thanks Olly :hello:

     

    17 hours ago, domstar said:

    That's great. I love the way it's set with a large background. It really makes the picture. Hats off.

    Thanks for the comment. I'm not normally a large background fan with small objects, however, in this case, it seemed the best option.

    Alan

  8. The galaxy M58 is located in the Virgo constellation and is approximately 65 million light years from Earth with a disk diameter of approx 110 thousand light years. 

    It's relatively low in new star formation, having little hydrogen gas which is concentrated in its elliptical core. The core is relatively dim and is believed to contain a  super-massive black hole of 70million solar masses.  Images of this object are rare on SGL, so I thought I would attempt to capture it. 

    The LRGB image below represents just over 10 hours integration time and was taken with my Esprit 150. If you look closely,  you can see a few details of the core. 

    Alan

    1941903018_7.Final.thumb.jpg.2c48b9b70c8968db724514efdf0a98ef.jpg

     

    LIGHTS: L: 24, R: 12, G:12, 14 x 600s. DARKS:30, FLATS:40, BIAS:100 all at -20C. 

    • Like 20
  9. 54 minutes ago, glowingturnip said:

    ooo, I'd still be tempted to have a go though - red channel as luminance in lighten mode through a super-nova-only mask maybe ?

    At least let us have a look at the subs with it in

    Hmmmmmm.....however, just for you Stuart: here is the result of the image which results from the stacking of the three 600s red sub frames which contain the supernova.  Unprocessed, apart from the stretch and the arrow !

    415322307_30.SupernovaM1003redframes.jpg.8471682aa8276f074db2514a6e841d69.jpg

    • Like 1
  10. 17 hours ago, David Crane said:

    Apart from Pixinsight, can anybody recommend good image processing software. Thanks

    I use the following software for processing my images - you can see the results by going to my gallery. I seem to have collected quite a lot of software over the years....

    1. Pixinsight - now my main processing source.

    2. Photoshop - now mainly used for cosmetic corrections and colourisation.  This used to be my main processing source along with CCDstack. 

    3. CCDstack - I still use this for calibration and sometimes permanently stretching images since it is so easy to use. One day I shall move to using PI for calibrating my images. 

    4. Registar - I use this for registering images that other programs cannot.  It is very useful for moasic construction. I also find that it is sometimes useful to re-register RGB mages in this program if you are having problems with star colours. 

    5. Gradient Exterminator - a plugin for Photoshop that eliminates gradients. I sometimes use this but now find it is largely replaced by PI's DBE. 

    6. Noels Actions - a plugin for Photoshop that has a variety of excellent actions, some of which I still use (eg increase star colour).

    7. Straton - a stand alone program for removing stars in images.  

    8. NeatImage - a stand alone program to reduce noise in your images. This is very good but I find that I'm using this less as I gradually get more proficient with PI's TGV Denoise. 

    Alan

     

  11. 12 hours ago, tomato said:

    Great image of a subject not so frequently targeted. Was this taken with the SX Trius 814?

    Thanks ! - yes, it was taken with my trusty SX Trius 814 - which gives me an imaging resolution of 0.7 arc seconds per pixel. I was a little concerned when I first used it with my Esprit 150 since I thought the imaging resolution might be too small, however, it turned out that for my set up/site that it appears about optimal.

    Alan

  12. 14 hours ago, alan potts said:

    That's really nice Alan, why didn't I get a 150 Esprit when I had the chance, can you not change the setting to get the SN in shot?

    Alan

    Thanks Alan. On the Esprit 150 - Yes, I'm very happy with the scope, it is excellent quality for the price.

    On the SN - unfortunately, the SN only appears in three of my Red sub frames so, attempting to force their inclusion isn't going to work - I'd just end up with a red SN :).  Personally, I doesn't bother me since a SN just appears as another star, albeit in an unexpected position. 

    14 hours ago, MartinB said:

    Ooh that's outstanding!  Beautifully processed.  Do you have quite a dark sky.  Who wants a supernova messing up the image anyway!?

    Thanks Martin :hello: - yes, my site (aka back garden) in East Sussex is quite dark (no street lights), it is also relatively high which seems to help with good seeing. The only downside is that it does get quite windy, although my roll-off roof observatory protects most of the scope from the gusts. 

    • Like 1
  13. M100 is located in the Virgo cluster at a distance of 55million light years, it is one of the brightest and closest galaxies within the cluster. It's a spiral galaxy with a pronounced bar at its centre.  Quite a few supernovas have been found here, the most recent being in 2019, designated SN 2019ehk which was discovered on 29th April. 

    The LRGB image below represents 12.3 hours integration time and was taken with my Esprit 150

    (For those that might be interested: the data was gathered between Feb and May 19 , so I was wondering why I couldn't see the supernova in the image. On examination of the individual subframes it transpired that I captured it in  only a handful of subframes, it's first appearance was on the night of 29th April.  So, when I stacked the image,  the supernova was simply rejected as a statistical error..... I think I've come to the conclusion that I'm not cut out for supernova hunting :rolleyes:).

    Alan

    333367797_29.Final.thumb.jpg.14d20762cc1fd0fd726aaaf92708148c.jpg

     

    LIGHTS:: L:26, R:19, G:13, B:16 x 600s, DARKS:30, FLATS:40, BIAS:100 all at -20C.

     

    • Like 17
  14. 17 hours ago, Petergoodhew said:

    n excellent image of a target so often overshadowed by its big neighbour.  Well done.  That long integration has really paid off.

    Thanks Peter. :)

    17 hours ago, Rodd said:

    Lovely....makes me pine for LRGB, which I find difficult.  I really like the naturalness of the image...and the scale!  You really "got right in there".  Is this a crop?  Sh2-201 is quite a little gem.

    Rodd

    Hi Rodd

    Yes, Narrow Band imaging is great for revealing detail but in my opinion you cannot beat LRGB from naturalness. I do agree it is difficult, particularly when you have nebulosity around.  Yes, it is a crop, although not very much has been chopped ! :hello:

    Alan

  15. SH2-201 is a small emission nebula located in Cassiopeia. It is often captured as a by product of the commonly imaged Soul Nebula (SH2-199), which is partially shown here to left of the SH2-201. 

    On the annotated image below, I've also marked the location of a Herbig-Haro object (HH-163). These transient objects are  formed when high speed narrow jets of partially ionized gas from new born stars collide with nearby clouds of gas and dust. Typically, they only last a few tens of thousand of years.

    On the processing front, I decided to process the nebula separately from the starfield by firstly removing the stars and then adding them back, which seemed to help in getting better definition of the blue stars within the nebula. 

    This LRGB image has a Ha blend into the Lum and Red channels and represents about 31 hours integration time. It was taken with my Esprit 150.

    Alan

    1664513009_25.Final.thumb.jpg.5815a8ace112622ba27c62fb5d4afd66.jpg

     

    145729043_25.Finalannotated.thumb.jpg.15aebc25c618388711939ded606c3c23.jpg

    LIGHTS: L:40, R:19,G:22, B:17 x 600s. H: 30 x 1800s. DARKS: 30, BIAS:100, FLATS:40 all at -20C

    • Like 13
  16. 13 hours ago, smr said:

    It does seem very good. I've watched quite a few videos and am onto the realm of pixels part... 

    but I'm a bit confused...Adam uses CCDstack and stretches the image / adjusts brightness etc. before Photoshop showing a really nice result already..

    But I use Deepskystacker to stack and then use Photoshop for everything - stretching etc.

    So should I be using a program similar to CCDstack before Photoshop? I also don't record FITS files, and instead capture RAW files as I use a DSLR. But CCDstack only seems to work with FITs.

    It is not necessary to purchase CCDstack (although it is a very good program).  When processing in Photoshop, Adam primarily uses CCDstack for a Digital Development Processing (DDP) stretch of the luminescence image such that the object of interest will end up with a lum level that is around 180 (ish) - if you end up with lum values more that 200 then it will be very difficult to colour.  So if you don't have CCDstack, then all you need to do is find a program that can perform a DDP or similar stretch on the lum data.

    Alan

  17. 14 hours ago, Xplode said:

    Very nice galaxy!

    Color balanse seems a little off.
    What i don't like is the black background, it makes it look a little "lifeless".

    You have lost a lot of faint background galaxies and also the faint dust because of the dark background.


    Here's an area very close to NGC7331 (upper right corner), lots of faint yellow background galaxies can be seen and also the faint dust.

    image.png.2ffbce90dae4c1d65632d3008fc91605.png

    Hi Ole

    Many thanks for your comment. You raise a very interesting point regarding the background level.

    To me, there are two complementary approaches to the processing of deep sky objects:

    1) Stretch the background and the main object of interest at the same level.  The main advantage of  this approach is that it highlights details everywhere. The main disadvantage is that you can end up with bloated stars, white star cores and white clipped objects which can distract from the object of interest.  This distraction effect will increase the more that the image is cropped since the background details will get proportionally larger. 

    2) Process the background separately from the object of interest.  This has the advantage that you can control the relative emphasis level of the object of interest, star bloat can be better controlled and white star cores along with white clipped objects can be avoided. This also allows you to significantly crop images to emphasize the central object of interest without enlarging distracting background detail. The main disadvantage is that you loose background level details.

    I use both approaches, selecting the approach that is appropriate to what I'm trying to achieve. 

    In the above image, I choose approach 2) and ended up with a background level of about 18 (0= black, 255 = white). This was primarily because I wanted to dim the stars and background to a level that I judged emphasized the object of interest  (eg NGC7331) to best effect.  However, if this was a much wider field of view, say NGC7331 including Stephan's quintet, then I would have used approach 1). 

    To me, this is all very much personal taste with no right or wrong answers. 

    Alan

  18. 8 minutes ago, smr said:

    Thanks for the above books. I'm not sure I need the imaging primer though? I thought that was to do with gear needed and acquisition rather than image processing?

    Although the book "The Deep Sky Imaging Primer by C Bracken" is called a primer I would regard it as an intermediate level book. It's contents are about 50% about processing images.

    Personally, if you want to learn on how to improve your Astrophotography Photoshop skills I'd first go to the Adam Block video tutorials. 

    Alan

  19. 2 hours ago, smr said:

    Hi,

    I'd like to buy some good books for Astrophotography processing. I use Adobe Photoshop so books relevant to this software would be most beneficial. 

    Thanks.

    Joel

    Some excellent books on (Photoshop dominated) processing of Astronomical images would be:

    1 - Photoshop Astronomy by R Scott Ireland - incredibly detailed but maybe slightly dated.

    2. - The Deep Sky Imaging Primer by C Bracken - also covers acquisition.

    3.  Lessons from the Masters - Edited by R Gendler -  Advanced.

    Whilst the above books are very good, I would also suggest that you consider some world class video tutorials from Adam Block - see https://adamblockstudios.com/categories/DimensionsOfPhotoshop

    Alan

     

    • Like 1
  20. 1 minute ago, Rodd said:

    Still-it must be a crop no?   the target is so big in the FOV.  With my TOA 130 at 1,000mm and asi 1600 (also .7 arcsec/pix--.78 actually), the target is much smaller in the FOV.  Is the sensor you are using much smaller than 13.4x17.7?

    Rodd

    Hi Rodd

    Yes - the image is definitely cropped ! - I normally crop away until I get the prettiest picture. :) 

    FYI the camera I'm using is the SX Trius 814.

    Alan

  21. 3 hours ago, Ouroboros said:

    By the title I was expecting a motorway (M76) photographed at dawn. 🙂

    You've got a really lovely photograph there. So good to have the astronomical info too. 

    Thanks !

    1 hour ago, Craney said:

    Great shot.     Have tried this one and soon discovered that I need to move to the Gobi Desert to get enough hours in....

    The image is LRGB.....but you mention that Oiii adds a colour.....   so is it a LRGB/Oiii  Hybrid mix   ??  

    Hello and thanks for the comment.  The image is LRGB, so I'm just using broadband filters.

    The object is quite rich in both Ha and OIII emissions,  which is why you sometimes see narrow band images of this object using Ha and OIII filters.   However, since Ha = Red and OIII = Blue you can also choose to image this with broadband filters, as I have done.  Hopefully this makes sense. 

    25 minutes ago, Rodd said:

    Very nice--is this with the 150?  I would have guessed it was from a much larger scope--well done

    Rodd

    Thanks Rod.

    Yes, this was taken with my Esprit 150. I'm at an imaging scale of 0.7 arc seconds per pixel , so it's high resolution. In addition, I performed a high strength deconvolution on the lum data which revealed more detail. 

    Alan

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