alan4908

Thanks for the comment Alan

Thanks Martin. 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

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

Thanks Giorgio - I'm pleased that you like it ! 😀 Thanks

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

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

That is impressive ! I've also made some progress into Pixinsight and away from PS. I was helped enormously by the Adam Block tutorials on Pixinsight which you might also find of use: https://adamblockstudios.com/categories/PixInsight Alan

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

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

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. Thanks Olly 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

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

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 !

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

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

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. Thanks Martin - 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.

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

Thanks Knobby Thank you Alan.

Thanks Peter. 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 ! Alan

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

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