Friday, 12 March 2021

Varying Degrees Of Imaging Success

IC405, Orion and M51

I've been grabbing the imaging opportunities when I can of late.  The weather has been so hit and miss that it was nice to get at least something under my belt.   As I continue my imaging journey, I try to post all my images, and let's face it, a lot of them are rubbish.  Some are results of experiments with processing techniques and others are results are from different capture techniques.  Occasionally, it all comes together in a rather pleasing fashion.
So, I kick this little collection off with an experiment that didn't exactly go wrong, but was an interesting learning curve.  My first image is of the nebula IC405.  I have imaged this target before, but this is the first time I have done so using the quadband filter and the results are not entirely what I expected.  This might be down to poor understanding of the different light wavelengths emitted or reflected by the nebula, or an all out mistake somewhere in my processing workflow.  Whatever the reason, I have really struggled to get any significant colour to the target.
Otherwise know as the Flaming Star nebula, this is a completely different outcome to the last time I tried this.  The last time, I got plenty of blue, violet and red coming through.  This time, just a yellow or orange finish.  I might have to go back and reprocess using a different workflow on this one.

Next, we have an all time Winter favourite for visual observers and astrophotographers alike.  I've had a few goes at imaging the Orion Nebula over the years but as yet have not been able to get an image which I am truly happy with.  The search for the great image still continues.  However, there are mitigating factors for this image.  The thought of imaging in mono intrigues me, but I am firmly in the one shot colour camp at the moment.  And a lot of that has to do with time.  I simply don't have the time to spend taking upwards of 10 hours per image which is often required when using mono cameras.  My general mantra has been to use a capture time with a maximum of 3 hours, and OSC cameras allow me to do that.
With this image of Orion, I reduced that capture time even further producing this image with 6 x 5 minute exposures.  That was down to the great British weather.  The forecast says one thing, but nature decides on taking it's own course.  The tricky thing I find with Orion is producing something which doesn't blow the core of the nebula out.  It's such a bright target (visible to the naked eye under the right conditions) that it's easy to get carried away with getting as much detail as possible with the outer reaches of the nebula, but then lose the structure around the core.  Knowing that the final image was generally quite poor, I tried something a bit different by removing all the stars from the background.  The result, well, it shows some potential and one day I will nail that image of Orion.  Perhaps next Winter instead.

Eventually, when everything comes together I still continue to knock together something I'm genuinely quite pleased with.  M51 is a really pretty target.  A pair of interacting galaxies in the constellation of Canes Venatici and relatively easy to pick up and image with my 80mm refractor, M51 is instantly recognisable.  Other images I have seen of M51 always seem to have a pleasant blend of blues and reds in the arms of the main galaxy structure.  Traditionally, I have struggled to replicate this and I wasn't expecting too much different this time.  I wasn't sure how M51 would look after being imaged with the quadband filter so that was an unknown in itself. 
In the raw data, for some reason many of my subframes seemed to have horizontal banding across them.  I have read forums where other people have had the issue and have struggled to resolve it, but until now, I have never experienced it myself.  I hope that it's transient, one off in nature and doesn't start plaguing my imaging.  
I decided to use a workflow in PixInsight which starts off splitting the stacked image into different (R, G and B) colour channels, carrying out background extraction and then recombining them in slightly different ratios using PixelMath.  Towards the end of that particular workflow, I have learnt some new masking techniques which allows me to really enhance specific colours either just within the target, or the wider background.  
Anyway, 3 hours ish of subframes under near new moon conditions and then another 3 hours of calibration frames and few hours of processing have enabled me to put together this final image.

So there we are for another post.  Thanks for reading and clear skies!

Sunday, 28 February 2021

NGC 2244 The Rosette Nebula

 The Rosette in Quadband

Casting my mind back over the last 4 or 5 years, I try to remember when the last time was when I imaged NGC 2244.  The answer, well, I can't actually find any record of imaging it before which I suppose means that this is my first crack at it.  Usually, images of NGC 2244 are almost purely in red in appearance, but over the last year or so, I have favoured using the Altair Quadband filter.  This, in combination with continuing to learn new processing techniques in PixInsight as allowed me produce an image with a twist.
We're currently in a run of clear nights here in Herefordshire which also coincides with February's full moon.  Usually, this would mean slim pickings for both visual and imaging with a OSC camera areas of astronomy as the moon is so bright, trying to see anything is a tough ask.  But this is where the quadband filter really comes into it's own.
NGC 2244 is in the constellation of Monoceros and remains high in the sky for a great deal of the night, and is actually the designation given to the cluster of stars at the centre of the nebula.  To be more accurate, NGC 2237 is more commonly given to the nebula as a whole.
So, onto the image itself.  This image consists of around 3 hours of data made up of 5 minute exposures.  Then on top of that, approximately another 3 hours of dark frames, and finally the flat frames used for calibration.  The subs were all collected using Sharpcap and then the processing was done in PixInsight.  I think the absolute key thing with the processing workflow for this image in particular was being able to split the image into 3 colour channels (R, G and B) and then using a feature called PixelMath to re-blend those channels in different ways and I think this is the thing which has helped me to introduce the different colours to the final image.  To be perfectly honest, it really has surprised me when I see how it turned out.
Of course, with every image, there are positives and negatives.  Unfortunately after stacking the image using the calibrated frames to produce my base image, I saw that I had once again failed to deal with the amp glow and sensor noise which appeared in bands across the very top of the frame and the bottom of the frame.  I had put so much time and effort into getting the image that far, that I didn't want to start over and try to understand why my dark and flat frames hadn't removed all the regions of amp glow and noise they were supposed to so I decided to just crop the image to help improve the image.
Without further ado, here is the final image of the nebula, and I really look forwards to having a play with this data again to try and get even more detail out of it.

Thursday, 18 February 2021

A Horse and a Jellyfish

Good day to you and thanks for stopping by.  It's been a quiet start to the year in astronomy terms because of the weather.  Here in the UK, winters tend to be wet, wet and mild, wet and cold, wet and windy or very very occasionally clear and a bit chilly.  The common theme amongst most scenarios obviously being wet.  But for a couple of nights a week or so ago, we had several clear nights during which time I managed to get the roof off the observatory and get a few hours of photon collecting under my belt.  Over those evenings, I concentrated on 2 targets.  Both are reasonably common to amateur astrophotographers, but one of them was new to me.

Horsehead Nebula - Barnard 33

To kick off proceedings, let's take a look at my first effort.  The Horsehead nebula is in the constellation of Orion, and is often imaged in the same field of view as the neighbouring Flame nebula.  It's an area rich in Hydrogen Alpha, although the Horsehead itself is a dark nebula caused by what we think is a massive dust cloud in front of the dominant HA region.  As well as the Flame nebula and often overlooked, there is a third nebula in the vicinity designated NGC 2023.  This is a reflection nebula, quite small in apparent size and showing up in a blue white colour.

This attempt at the Horsehead nebula was a bit of an experiment (as you could argue are all my images!) where I used some new tools in PixInsight like the Game script, to try and really enhance the areas of nebulosity around the image.  This image is made up of 24 x 300 second images plus calibration frames all stacked and processed in PixInsight with some light touch ups in GIMP.

Jellyfish Nebula - IC443

My next images are of another nebula known as the Jellyfish nebula.  This is found in the constellation of Gemini.  It's one nebula in a massive area of nebulosity visible in much wider field images of the region.  IC443 is thought to be the remnant of a supernova which occurred circa 10000 years ago, although estimates range from 3000 to 30000 years ago.
I collected the data for these images during a night of particularly good quality seeing, and when ambient temperature was around -7 to -8 Celsius.  My Altair Hypercam doesn't have any TEC cooling, relying purely on a small fan to cool the internal workings of the camera down.  This means that I can never really cool the camera down much below whatever the ambient temperature is.  Therefore, the colder it is outside, the better the individual frames are being created by the camera.
In PixInsight, I generally use the same settings for pre calibration and stacking to give me a base image to start from.  After that, my workflow is somewhat less structured.  I have one workflow which I used for my OSC processing for quite a while with some reasonable success.  In more recent times I have started to use an Altair Quadband filter in my imaging train and I have started to experiment more with RGB and different palette techniques.  I have to remember that the likelihood of me being able to produce two identical images from the same base image using an identical workflow is incredibly small.  There are so many stages and steps that are subject to on the hoof interpretation, and so many little settings and sliders to tweak along the way that I'm far from knowing exactly what I'm doing at each stage.  Fun, isn't it?  Nevertheless, I can really appreciate the difference between these two workflows.
Both these images were created from the same master image composed of 78 x 145 second images (188.5 minutes total) plus calibration frames captured in SharpCap Pro.  Again, a majority of the processing was carried out in PixInsight with some final touches applied in GIMP.

The first of these images I produced using my standard OSC process.  There's plenty of colour to work with coming through, but the background stars really illustrate how much there is going in this region of the sky.

The second image is cropped slightly closer into the nebula and I have also managed to reduce the impact of the background stars (not exactly sure how though, but it'll be in the process somewhere).  I used a workflow which allows me to split the image into 3 channels (RGB) and work with them and mix them at different ratios using PixelMath in PixInsight.  I've also started to learn about some other masking techniques which I can use to help protect or expose the different areas of the nebula more specifically and enhance it.  The noise reduction steps in this workflow are also a bit different and appear to me to make a significantly larger difference.

I always enjoy my images, even if they never turn out great, but I particularly enjoyed working on the second of the Jellyfish nebula images.  Technique wise, I think it has got to be one of my best images although it's not the most stand out to look at.  I find myself looking back over the previous efforts and wanting to give them another go using the quadband filter in my newly developed workflow.  I just need the sky conditions to cooperate!
As always, thanks for reading, and clear skies.

Sunday, 27 December 2020

M1 - The Crab Nebula

M1 - The Crab Nebula

In what might turn out to be the last post of 2020, I thought I would round off the year with an effort on M1, The Crab Nebula.  The Crab Nebula is a supernova remnant found in the constellation of Taurus.  It's quite small compared to many other imaging targets, but it's also visible with a decent pair of binoculars or telescope.  The challenge with imaging this particular nebula is to try and tease out the detail within the nebula.  Undoubtedly, a longer focal length telescope will help with this but I need to make do with my 80 ED-R.

I've also made some changes to my imaging set up to try and get the best out of it.  Since I bought the Hypercam 183c, I have just been using it connected to the telescope sometimes with the reducer, and sometimes without.  To get the best out of the camera and telescope combination, I needed to introduce some spacers between the camera sensor, and the telescope.  In theory, this should deal with the 'stretched stars' around the edges of the full frame, in particular the corners.  The correct spacing needs to be very accurate though.  So, I have introduced a 15mm spacer, a variable spacer and a filter drawer into the imaging train.  Bearing in mind, this is the first image with the new spacers in place, I quite pleased with the result, although I think I still need to make some small tweaks with the variable spacer.  That's for another time though.

Finally, before I move onto the image itself, I have also made an experimental change with my pre-processing workflow in PixInsight.  When I first started using the software, I initially used the Batch Pre Processing script to help pre process all my raw light, flat and dark files.  As I got to know and use PI more, I moved onto manually performing the calibration steps to try and achieve better results.  Recently though, I once again have started to struggle with dark from subtraction from my light frames meaning that I am still getting the sensor interference appearing on the right side of the final image.  Since I put my workflow together, numerous enhancements and updates have been released for PI and I now think that there are some additional settings which I need to find out about to help removing this phenomena fully again.  One of the improvements which has been introduced is a new script called WBPP, or Weighted Batch Pre Processing.  Very similar to the original BPP script, it's had some improvements of it's own, so I thought I would give it a go.  I'm really pleased with the result.  The resulting image it produces once again has no sign of the sensor interference.

So, onto the images themselves.  I've produced 2 images of M1.  The first has been processed in PI using PixelMath to help develop the colours of the supernova remnant a little further.  The second image is a cropped version with the background stars removed using he StarNet tool in PI.  Both images were then lightly processed in GIMP.

Finally, thanks to anyone who has given their time to read through my ramblings over the last 12 months.  Feel free to subscribe to my blog if you wish.  You'll get an email anytime I post something.  Have a great and more importantly, safe new year and I will be back in 2021 with more astro related drivel :-)

Thursday, 24 December 2020

My Top 5 of 2020

 My Top 5 of 2020

What a 12 months it's been.  A great year for space science, space travel and amateur astronomy.  2020 has seen some fantastic things happen like the first crew dragon capsule to meet up with the ISS and China performing lunar missions.  It has also seen some sad things like the demise of the popular Arecibo observatory and also courted with controversy with the first formation of a satellite constellation.  But in terms of my astronomy activities, it's been quite some year with unexpected opportunities and other opportunities taken away.  So, in reflection I've put together my top 5 highlights of this, the most challenging of years.

5.  The Pier Goes In

It was long an ambition to get a permanent set up for my kit.  Moving house in recent years provided me with that opportunity, and with the construction of the observatory over a year ago I finally had chance at the start of the year, to get a pier built and put in place.  It was the last piece of the jigsaw which allowed me to get everything set up and in place.  It has proved to be a fantastic timesaver and mean that I can now be switched on an imaging in as little as 10 minutes.

4.  Awesome Astronomy Does Live Streaming

2020 Was full of firsts.  My next highlight was provided by one of those firsts, and that was the live streaming of the Awesome Astronomy recording of one of their podcast episodes.  At a time when people were restricted in what they could do, it provided an excellent distraction from day to day life.  It provided an excellent opportunity to link back into the astronomy community and see some familiar faces.

3.  ISS Solar Transit

Long have I seen images which fellow amateur astronomers have taken of the Sun with a silhouette of the ISS passing across the front of it.  I have always wanted to attempt to capture an image of it myself, but hadn't made time or opportunity to do it.  Towards the beginning of Summer, I did a piece of research to find out when the next transit path was and found that there were 2 transits in the coming days.  The first attempt was a fail.  I just didn't get a quick enough frame rate to capture the image.  The second attempt a couple of days later was almost scuppered by cloud, leaving me no time to get a good focus.  However, I succeeded in capturing my first image of an ISS transit.

2.  Dither

It seems an odd choice, at first, to call this a highlight of my year, but I firmly believe that learning how to incorporate this into my image capture process has made, and will continue to make, a big improvement to my images.  It wasn't until later in the year, quite recently in fact, that I adopted the technique, so I haven't produced many images at all using the dither function, but it is undeniably well worth doing.  And what's more, it's so easy to do.  This was my first proper image produced using the dither function, and while it's not especially amazing, I am really pleased with it.

1.  Comet Neowise

Without doubt, the big thing which captured the public imagination this year was the first naked eye comet to be widely visible since the 90's.  At a time when we were all being encouraged to take some exercise, but avoid contact with everyone else, Comet Neowise proved to be an excellent opportunity to get out of the house. Even the weather decided to cooperate.  The comet was visible back in the Summer, so it meant that it called for some late nights to be able to see it at it's best.  It felt somewhat adventurous, taking off on my mountain bike at sunset with my camera on my back heading out to a farmers field and then returning in the small hours when all was dark.  But what it lead to was a collection of images which I was really pleased with.

2020 has been full of challenges, and 2021 is going to be much the same, but there is so much to look forwards to.  Clear sky permitting, I shall be taking every opportunity to image and observe as I can this year.  I hope to get back to a star part or two and who knows what else I am going to discover.
Thanks to anyone who has read my blog over the last year, or ever actually.  Have a great Christmas and New Year.  Here's to 2021!

Thursday, 17 December 2020

NGC 7331 - More than meets the eye.

 NGC 7331 - More than meets the eye.

Greetings!  Sitting here listening to the latest Awesome Astronomy podcast, it's time to put fingers to keyboard and put together a post about my most recent image.  In truth, I wouldn't post this image normally.  It's quite poor in quality because of the conditions that the data was gathered in.  The night of the image capture was back at the start of November when the initial dark sky quality was not too bad, but as the evening went on the sky filled with a thin mist until a point where the only starts visible were at azimuth, directly overhead.
My target for the night was NGC 7331, which I picked out of one of my astrophotography books.  Also known as Caldwell 30, it is an unbarred spiral galaxy in the constellation of Pegasus.  So, why did I decide to post this image anyway, despite it overall being quite poor.  Well, when I started looking more closely at the image, I realised something which I hadn't appreciated when I first chose the target and that was the number of galaxies that could be seen in the image in poor conditions with just 3 hours of exposure and a small 80mm refractor.  
At a relatively quick glance when zoomed into the image, I picked out at least 24 other galaxies, aside from the main target in the centre of the image.  To help point them out, I have added red lines pointing at each galaxy or galaxy cluster.  It's amazing to think that these are just the ones I can see at a glance.  The numbers of galaxy in the image's field of view probably is much more.

In case you can't see the galaxies pointed out, I've taken zoomed in image snips of many of them to illustrate what's visible in a full resolution image.  Perhaps my most favourite one is the last but one image which shows a perfect face on spiral galaxy in which the arms of the galaxy can clearly be defined.  In the main image, it's in the bottom right corner.

So, an image and a post more for posterity than publishing on the blog, but it's a great reminder that when imaging, it's always worth having a scout around to see what else is lurking around the main target.  

Sunday, 22 November 2020

Dither Fish

 Dither Fish

Recently I took the opportunity to take advantage of around 4 hours of clear sky here in Herefordshire.  I didn't have much planning time, so I opted to revisit a target I first imaged back in December 2019.  This was back when I just started using my Altair Quadband filter and I was sticking religiously to a tried and tested processing workflow in PixInsight.  As well as learning a bit more about the filter and processing, there has also been one other big step forwards with my data collection.  In my last few outings, I have started using the dither feature in SharpCap pro.  In my traditional way of imaging using SharpCap, I couldn't dither as the feature is only available when using the Live Stack feature.  However, I read that you could get around this by simply saving each of the subframes by clicking on a tick box in the Live Stack feature.  This sorted the sub frame saving issue which meant that I could then utilise dither when guiding.  I'll post more on the technique and settings I use another time, but for now, let's take a look at the results.
The two images below are cropped around the main part of the target showing a good proportion of the nebula itself, but also so well defined background.

The first image is quite noisy throughout the colour and background.  You can also just about make out that there seems to be a pattern where the noise appears to run diagonally top left to bottom right down the image.

The second image is part of my most recent image.  It shows the same cropped area, but notice the significant reduction in noise between the images.  While this is undoubtedly partly down to improved processing, the use of drizzling during the data gathering phase has made a huge difference, completely removing the diagonal noise patterns throughout the image.

IC1795 - The Fish Head Nebula

Having taken that big step forward and produced notable improvements, I shall undoubtedly dither on all my deep sky imaging from now on.  This only leaves me one thing left, and that's to show off the finished final image.  I seem to have a little problem with sensor noise coming through on the right side of the image.  A new dark library would of probably sorted that out.  Nevertheless, I'm still very pleased with this dithered quiet fish head.

Tuesday, 17 November 2020

Autumnal Trio - M57, M53 and NGC 6888

 Autumnal Trio - M57, M53 and NGC 6888

Back in September, we had a run of poor weather which meant I had the chance to revisit some old data and apply some new processing techniques.  Though astrophotography in my opinion is always going to be a case of continual refinement, it's been nice to get the chance to collect some new data.  Generally speaking, weather conditions have been a bit rough, so I haven't been able to do as much as I would like to do and it's just been a case of grabbing any opportunity I can without much in the way of thought or planning.  I've also come across a few bugs in my set up which has lead to a bit of frustration, knowing that time has been precious but needing to sort out these issues before I could proceed resulting in bit of a change in the way things are connected in observatory.  More on that later.  

M57 - The Ring Nebula

The first of the images I've had chance to put together is of this Autumn classic, the planetary nebula M57.  It's in the constellation of Lyra and during late Summer into early Autumn, can be found almost direct overhead as it gets dark.  While small, it is quite bright, so on this particular night in October, after addressing a few technical gremlins in the observatory and with cloud forecast, I couldn't spend hours and hours collecting data.  I was limited to around 90 minutes or so, but as you can see, that was more than enough to get some good data and colour using the Altair 183c Hypercam.  Through the eyepiece of a telescope, this target can easily be missed, not because it is that dim, but more often because it a quite small.  At higher magnification, you do lose a bit of brightness, but the ring can be resolved.  With the use of a UHC filter to help darken the background sky, the nebula can really be pulled out from it surroundings, but it will still only be visible as a wispy grey ring.  It's still though, an absolute favourite target for my observing list at this time of year.

M57 - The Ring Nebula in the constellation of Lyra.

  M33 - The Triangulum Galaxy

Given the choice of galaxies to image at this time of year, M33 has got to be one of my favourites ahead of some of the more traditional and well known galaxies of Andromeda and the Fireworks galaxy.  It frames well, responds very well to OSC imaging cameras and is well positioned throughout the night.  As is the case with most targets, the more data that is collected, the better.  This time around, again battling against deteriorating conditions, I was fortunate to get around 2.5 hours of data on it.  I wanted more.  I wanted way more, but cloud and bonfire night got in the way.  It wasn't until post processing did I really appreciate how much the sky quality decreased through the evening as more moisture condensed in the atmosphere combined with air pollution from fireworks and bonfires.  In the end, much of the data towards the end of the imaging was useless so I had to bin it.  Nevertheless, playing more with some new to me techniques of processing in PixInsight, I was able to pull out a pleasing amount of colour and data from the subframes I had collected.
Compared to my last effort, It's good to see that in my opinion, my imaging and processing skills seem to have improved somewhat.

M33 - The Triangulum Galaxy

NGC 6888 - The Crescent Nebula

This is a fascinating nebula.  NGC 6888 is found in the constellation of Cygnus, and it is one of those nebulae which when observing, often gets overlooked as it's tricky to pick out unless you're using some sort of massive light bucket and filter.  Imaging wise though, it's a different story.  Capturing a reasonable amount of data for the image is fairly straight forwards.  However, this truly is an example of more data the better the image.  The initial shape of the crescent is the first part of the nebula to be revealed.  However, I don't think OSC imaging really does this target justice.  To really bring the full extent of the nebula structure would mean adopting mono imaging techniques with filters and perhaps putting hours and hours of time into each channel.  What amazes me is that this nebula was first discovered back in 1792 by William Herschel using the equipment of the day.  Though he would of had far less light pollution to deal with (one assumes), he would of been using inferior quality optics, small aperture and no filters.
This data was obtained on November 6th. Unfortunately, the bonfire night antics this year seemed to spill over into a 2nd, 3rd, 4th and even a 5th night.  I knew I needed as much data as I could to help bring out more of the structure within the crescent shape, so in the creation of this image, I did include some poor quality sub frames which I would of otherwise ditched.  One day, I would love the opportunity to collect perhaps 6+ hours of data, but this time I've made do with around 2.5 hours or so.

NGC 6888 - Crescent Nebula

Bugs and Gremlins

For some reason following on from Summer, I have had a couple of issues with frames being dropped from the camera while imaging.  Since buying my quadband filter, I've been trying to adapt my imaging techniques to make the best I can of the filter.  Some of these changes have included using SharpCap smart histogram to analyse the optimum camera settings for me to use.  What's become evident to me is that I needed to increase my exposure time from 2 or 3 minutes up to around 10 minutes, if SharpCap is to be believed.  I've tried to adopt these new settings, but I noticed not all the sub frames were consistently being written back to the NUC PC in the observatory.  Now, there are a plethora of reasons why this might be the case.  The Hypercam I have is one of the earliest versions, so it has no on board memory for buffering.  But theoretically, given that it's been working predominantly fine, I can't think of a reason why this should be the root cause this time.  Secondly, it's a USB3 camera plugged into a USB3 port on the NUC PC and it's commonly advised by Altair, that the length of the USB3 camera used is kept to a minimum.  I use the cable supplied with the camera, so that shouldn't be causing the issue either.
Considering these requirements, I was left with two easy options to try.  I had a bit of a change around on the observatory pier.  Originally, I had 2 3 pin power sockets, the NUC and it's power supply and the all the associated cables coming from from the mount, cameras and controller all contained within one plastic weatherproof box mounted on the pier.  I wanted to change the USB3 port the Hypercam was plugged into on the NUC which needed a reworking of the cabling.  To help make room, and potentially remove some strain off the cables and ports, I took out the 2 3 pin sockets and put them elsewhere on the pier.  The other thing I did was to remove a connection to a spare USB2 hub which I also had on the mount.  Strictly speaking, I don't need this, but it makes life a bit easier when it comes to transferring data to USB stick at the end of an imaging run. 
The second thing I have applied is a simple driver update.  I noticed during my checks that the driver I was using for the camera was from early 2018.  Usually, manufacturers will update drivers as time goes on, especially if they still use those same drivers for their most recent products.  I couldn't get the camera drivers from Altair on their own, but they do come bundled with their imaging software, AltairCapture.  So, I downloaded the latest version of the software and updated my installed version.  I was pleased to see that the driver was also updated with a 2020 version.  In some initial testing when taking some dark calibration frames, it was good to see that only a single frame was dropped right at the start of the run.  This is often the case though as I will make last minute tweaks to camera settings while the first from is being captured.
Hopefully this work has got rid of the bugs and gremlins which have appeared.  Alas though, I will need some clear nights to get everything up and running.  

Wednesday, 30 September 2020

NGC 281 3 Ways

NGC 281 3 Ways

 After a summer hiatus, I've got my astro mojo back.  In my last post, I showed off a series of images taken during a recent run of good weather.  Even though Autumn is well and truly here along with the wind and rain, I've been busy on other astro related projects by learning about more processes and techniques used in PixInsight.  
I've spent a few evenings looking around YouTube and other blog sites to see what other techniques people are using and look to introduce some of them into my own workflow.  The newest technique I've tried to introduce is splitting the raw stacked image into 3 RGB colour channels.  In theory, it allows me to work on the three channels individually, before re-combining them to form a colour image.  One day, I will put an example of my workflow in a post, but I need to improve it significantly first.
One of the easiest ways of comparing processing techniques is by starting each workflow with the same original data.  I chose NGC 281 which is a lovely nebula which sits comfortably in the frame of the Altair Hypercam 183c used in conjunction with the 80 ED-R telescope.
Onto the images.  This is the first image processed with my regular workflow for a straight forward OSC camera.

Now it's time to start playing.  To be honest, I can't remember all the different parts of the workflow I used for this next image.  What is certain is that there is still a load of noise and other work to include, but as an experimental image, it's pleasing to get some other colour out of the data, and play with contrast and saturation settings a bit more.  Remember, this is from exactly the same raw starting image as the one used to create the image above.

Recently, there has been a new update released for PixInsight.  It includes the StarNet++ tool which used to be a separate import.  Even though I haven't managed to get it to produce a really clean result yet, it still produces some interesting results.  I think it perhaps will work better on targets that don't have quite so many stars but this next image gives an idea of what it could do.

And there you have it.  It's always good to show some experimental images from time to time.  I wouldn't call either of these last two images anywhere near complete, but definitely encouraging signs of what could be achieved.  Happy days!

Thursday, 24 September 2020

Lockdown Astrocamp 2 - Another One Gets Away

 Lockdown Astrocamp 2 - Another One Gets Away

Earlier this year, I wrote about missing out on one of my highlights of the year, the Astrocamp star party.  Though gutting, cancelling it was the sensible, and only real choice.  Possibly through rose-tinted glasses, everyone looked forward to and hoped that the second scheduled event in September would go ahead.  Alas, continued developments have conspired against the organisers and us, to leave little option but to pull the plug on the Autumn event too.  But it takes much more than a microscopic organism to stop us from doing any astronomy! 
Readers of my past posts will know that we often do battle with the weather at Astrocamp.  More often than not, not much astronomy gets done but everyone still had tons of fun.  This time, should we have all been gathered at Astrocamp HQ, we would of had a straight run of clear nights for the whole camp.  Typical!  So, what do you do with a few days of work, a run of clear nights and a plenty of time?  Get out there and make the most of it of course!

What was it I did before?????

After a comparatively short amount of time out of the observatory (about 2 or 3 months in total) because of weather and generally Summer getting in the way, it's been awesome to get back in there again.  The first clear night was always going to be a bit of a struggle.  Trying to remember how things worked, what settings I used where. and how it all comes together was always going to tax the brain a bit.  That coupled with high cloud whipping across the sky occasionally meant that any thought of getting hours of data on a target was going to be tricky.  Best start basic and build back up I thought.  Gradually, it all come back, and I was able to get polar alignment tidied up, updates installed, get guiding going and eventually grab a few frames of a target.  That'll do for one night.

17th September and NGC 6992

Cygnus is high in the sky at this time of year, and has some truly awe inspiring targets to chose from.  Perhaps the most photographed is the Veil Nebula.  The nebula itself is a huge target, impossible to fit into a single frame of my camera and telescope.  It's obvious why people hone their mosaic skills in this area of the sky, taking sets of data from all different regions of the nebula before stitching them all together in post processing to give one image of the whole area.  I'm not at that stage yet. I wouldn't know where to start, but I did get around 3 hours of data on the Eastern Veil.  That would be good enough for me as a first serious swing at getting an image after the Summer break.

The Eastern Veil Nebula - Cygnus
Altair Astro 80 ED-R, Hypercam 183c and Altair Quadband filter.

20th September and NGC 281

After a few days of playing around with that data, and producing the image, I started to remember how far my imaging had come over the last winter.  There were two key things which I had in my mind to tackle next.  One of those was dithering.  For a quick explanation...
When a camera is taking long exposures, some cameras can produce a lot of 'noise' in the image.  It's particularly noticeable in the darker background where the image looks very grainy.  That in itself isn't too bad as you can remove it to a degree in post processing.  But, noise often appears in straight or diagonal lines across the image and I've seen it referred to in forums as 'walking noise'.  Due to it's regular direction, and frequency, it can be harder to eliminate during processing.  This is where the lovely term 'dithering' comes it.  Usually, the telescope and mount will track a target through the sky, and aided by guiding software like PHD2, the target is kept exactly in the same place in the frame for the whole time.  This I believe causes noise to appear in the same pattern for every frame being taken and when all these frames are stacked on top of each other, the walking noise pattern is formed.  Dithering combats this, so it was time for me to learn how to dither effectively.  By luck, it's extremely simple to set up within SharpCap.  A couple of ticked boxes, and a slight amendment to the way I set up my imaging runs, and I had it working.  Dithering now moves the camera on the mount a tiny amount, even just a few pixels, in a random direction in between every few frames.  It means that because the target, and therefor the background has moved slightly in relation to the rest of the frame, that the camera sensor isn't putting all the noise in the same place.  During stacking, PixInsight takes the stars in the image as fixed points, and overlays the images using those stars as reference points.  Any noise produced is therefor not concentrated in the same place every time, and therefor isn't so apparent in the final frame.  Perhaps one day I will do a more illustrative post on that, but it is a pretty basic tactic used in imaging which I should of learnt how to do and adopted from the start.
Nevertheless, dithering sussed and slightly less noisy data to process, I pointed the camera to NGC 281, the Pacman Nebula.  This is a target which I have imaged last around 2 years ago.  This was the result then:
Since then, I have invested in a new filter which isolates emissions of different light wavelengths very effectively.  It brings a whole new appearance to the final image.

Pacman Nebula - Cassiopeia
Altair Astro 80 ED-R, Hypercam 183c and Altair Quadband filter.

21st September and NGC 7635

The last night in a run of good nights for observing and imaging.  The great thing with having an observatory is that it gives me time to get everything on and imaging within around 10 minutes of opening the door.  After that, I'm free to get out the SBT (12" dob) and return to good old fashioned visual astronomy.  This time of year is awesome, especially at the moment where we have Jupiter, Saturn and Mars easily visible, with a couple of other planets visible if you know where to look.  With the Summer constellations visible for a few hours at the start of the evening, it's awesome to be able to see the Witches Broom nebula, the Ring Nebula and loads of the classic clusters.  If you hang around until the small hours, you then start to see the arrival of the more traditional Winter constellations like Orion.  I've also been lucky enough to provide some neighbours with a very quick whistle stop tour of the sky and it's been absolutely brilliant to hear their reactions the first time the clapped eyes on Jupiter and Saturn.  Hopefully something that will stick with them all for a long time.
Back to the imaging.  This quadband filter is making a big difference to my final images and I wanted another opportunity to compare a target imaged with just a light pollution filter (which filters out predominantly sodium, leaving many other wavelengths of light through) to one taken with the quadband.  So, I  looked back through my blog, and picked up NGC 7635 also know as the Bubble Nebula which I first images around 2 years ago.  I collected a very similar amount of data (around 3 hours ish) with the same camera.  This time though, the target seems to "pop" out much better.  It's a small target in the frame, and with hindsight, perhaps I should crop the high resolution image and enlarge it a little to help bring out more of the detail.  The new filter does seem to being out much more red, and fainter nebulosity is definitely more visible surrounding the bubble itself.

Bubble Nebula - Cassiopeia
Altair Astro 80 ED-R, Hypercam 183c and Altair Quadband filter.

Wrapping it up.

Earlier I mentioned that there were two things at the end of Spring into Summer, that I wanted to get to grips with.  On of those was dithering.  Tick.  The other is processing data captured with the quadband filter.  I use PixInsight as my primary software for stacking and processing, but it is quite complex.  I've heard and read of many people splitting their image up and doing some whizz bang processing on the different channels before combining it all back together again to give amazing results.  The bit that I can't find is a step by step guide for that part of the process using a OSC and quadband filter.  I've got a vague idea, but nothing solid which produces the results I expect.  That's my next objective, and one that I hope to have sussed in the coming weeks.  We shall see!
Until the next time, thanks for reading, and clear skies.