Wednesday, 20 October 2021

NGC 6888 The Crescent Nebula

Time for my latest image.  This Autumn, I've started taking data from several nights, and then combining it all to make a single image.  Previously, I have always tried to get all my data for a single image on the same night.  Added to that, I've also started doing meridian flips during my imaging so I can continue imaging as the target moves across the meridian.  It's so straight forwards, I can't believe it's taken me this long to actually having the confidence in doing it!

Anyway, onto the image.  I'm still really enjoying using the Altair Hypercam 183c v2 and combined with the quadband filter, it continues to impress me.  Learning a bunch of new processing techniques in PixInsight has made me appreciate how different images can be produced from exactly the same start point in the same dataset.  

NGC 6888 is well place for imaging as soon as it gets dark at the moment for people in the UK.  It's almost direct overhead and is well framed in the field of view of my imaging rig.  It's an emission nebula, around 5000 light years away in the constellation of Cygnus.


The nebula itself when looked at in a proper wide view image, sits in amongst a vast area of fainter nebulosity visible in this area of Cygnus.  The base dataset for this image consists of around 3 hours of data taken in brief windows of opportunity over 3 nights, and using the quadband filter, it is possible to start to bring out this nebulosity in the background.  Also, the more I use PixInsight, the more I am learning about the use of masks to help protect or enhance specific areas of the image.  Using some of these techniques slightly differently from one attempt of the data processing, produced a different image where some of the background nebula was really pulled out a bit more.


There's a huge amount more detail to come out from the background.  Some images produced by other imagers I have read about are composed from two different datasets.  The first concerning the target of NGC 6888 itself, and then a second dataset concentrating on the background nebulosity.  Nevertheless, I'm extremely pleased with how both the images have turned out.  The higher resolution versions which haven't been resized and compressed show much better clarity when zoomed in, so I have lost a bit of detail in these images.

Thanks for reading, and clear skies!

Tuesday, 19 October 2021

Smartphone Astrophotography

 Evening all.  A few weeks ago, I was fortunate enough to attend my first Star Party for 2 whole years.  The famous AstroCamp was back with a bang.  Every camp I have been to in the passed, I have summed up in a blog post when I got home.  Not this time though.  For once I decided to give the blogging part a miss.  But that doesn't mean I didn't love the whole experience as usual.  This camp was obviously different and truth be told, for me wasn't necessarily about the astronomy, but an excellent chance to meet up with all my friends who I hadn't seen for the last two years.

The forecast for the weekend was generally quite poor, so I took the unusual decision of not taking any astronomy equipment with me.  I know that there would be others there with their telescopes, so I could always visit someone else's eyepiece for any views.  In what turned out to be one of the wettest AstroCamps I can ever remember, the most bizarre happened.  Despite all the cloud, all the wind and all the rain, we still got quality time under the quality sky of Cwmdu for 3 evenings.  Typical.  Stuck at a star party, under clear sky with no astro kit.  What was I going to do?

I started thumbing through my phone and I decided to read up on how people manage to get some quality images just off their smart phones.  At the moment, I use a Google Pixel 4, so I started my search there and it was soon obvious that unbeknownst to me, the Pixel 4 is actually rather good at this astrophotography landscape thing!  From using it before, I knew that the phone had 'Night Mode' which has always been an option when working through the camera settings.  I thought that was it.  But I couldn't understand why all my efforts only come out mediocre at best...

Ursa Major in 'Night Mode' with the Google Pixel 4

Don't get me wrong, it's kind of impressive that a smartphone can pick out any stars with a sensor and lens as small as that at all.  But it's no where near the type of photo I had seen elsewhere.  It was while I was swiping through some web page about smartphone photography that I found an article written on astrophotography specifically with a Pixel 4 and it presented me with an answer which was annoyingly so simple that I can't believe I hadn't found it before.

Once the phone's camera is in 'Night Mode' the phone then starts monitoring for any sort of movement caused by the phone being held in the hand.  I set the phone down on the top of a near by post, and propped it up against a half drank bottle of beer.  Lining it up roughly where the Milky Way was visible all the way down to the horizon, I then left it.  Once the phone detected no movement, it automatically switched into the magic 'Astrophotography' mode.  Then, it is just a question of pushing the shutter button (being careful not to nudge or disturb the phone) and leaving the phone do it's thing.  Over a period of 5 minutes, the phone starts taking a whole series of images, aligning them and stacking them as it goes.  After the 5 minute counter reached zero, the phone produces two things.  The final stacked and aligned image, and also, a very short time lapse of the whole series of images.  The results were so pleasing, and actually even better than I had though possible.

My first test shot taken with the Google Pixel 4, looking across my pitch towards my camp neighbours.



The second test shot, this time from 'The Common'  There's slight evidence of trailing if you look at some of the starts closely, but this was much more in line with what I expected.


Now, getting more used to how the settings work, I started looking for more of a classic portrait Milky Way shot.  The phone now even started to pick up dust lanes.  This image hasn't been processed at all.  It's come straight off the back of the phone.


This was taken around 3am of the second night of camp.  After going to bed while it rained, the forecast was for a clear sky in the early hours of the morning.  I got up and managed to get this image of Orion, the Hyades and the Pleiades.  

The last of my images taken from camp, complete with red light lighting up some of the caravans on site.


Tuesday, 28 September 2021

New Season and Technique Updates

Testing and Rediscovering

Hello!  It's been a while 😏.  Very little has happened since March in my astronomy world, but with the return of darker evenings my mojo has been found and I'm now back at the helm of the good ship Astro.  I thought I would kick this post off with a couple of images which I have put together in the last couple of weeks.  As with many things, if you stop doing them for a period of time, you can get a bit rusty so this was a chance for me to get some practice in ahead of the coming Winter.
I've imaged two targets, the first of which is part of the Veil Nebula.  Shot over two evenings with around 3 hours of exposures, I didn't want to waste this trial data which I collected so I run it through my processing plans and come out with a reasonable effort to be honest.


I had a bit of fun with the colours in this one as I retaught myself the little nuances of PixInsight's PixelMath feature.

A week or so later, again over a period of a couple of nights, I gathered another set of trial data to play with.  This time, of the Iris Nebula.  Again, this is a target I have imaged before, and one which probably requires much more data to really start pulling the detail in the darker areas of the image.  Nevertheless, it gave me a great chance to run the whole process from start to finish and rediscover my processing workflows.



Technique Updates

Many moons ago, back in February 2019 I put this post together as I continued my journey of using PixInsight to process my astrophotography images.  It was intended to help anyone who wanted to get an idea of where I got my information from and how I like to process my information.  Since then, quite a few updates have been released to PixInsight, and I have also starting to use a quadband filter which opened up a whole new series of processing tools and techniques.  I decided that it was time for an update and so I have updated my documentation to take into account the updates to software and workflows.
At this point, I have also got to put a big shout out to GIMP, the opensource alternative to some of the more popular and hugely expensive image processing software like Photoshop.  I've found it so useful to help putting the finishing touches to my images, that I thought it's worth adding those final few steps I take before considering an image complete.  I always carry out the GIMP part of the process after all my PixInsight work is done.

Before you start...

Remember that some of the settings in these workflows are specific to the Altair Hypercam 183c and the focal length of my Altair Starwave refractor.  If you want to use these as guides, you may need to change some settings to reflect your gear.
The colours of the extracted layer during the background extraction steps could differ for you depending on your camera or filters.  That shouldn't matter, nor affect the image you continue to work on.
These really are best endeavour guides and documents.  I make no secret that I have watched, read and listened to many other astrophotographers much more accomplished than me and taken snippets of info and steps from their workflows to develop my own set of steps.  I really couldn't of got anywhere without the willingness of the astro-community to share their knowledge on how to achieve results.  I hope that this feeds back into the community and helps others a little.

Calibration Through to Stacking

This is the first update to my processing workflow.  You've been out imaging all night. You've got all your light frames, your darks and your lights.  This document has been updated to include some minor changes and screen shots and goes through how I stack and calibrate that data to produce an image which can then be taken forward for processing.

WBPP

Sometimes, no matter how hard I have tried, I have struggled to get PixInsight to calibrate and stack my data.  It can turn into a minefield, trying to track down which options in the workflow to tweak, miss out or substitute for something else.  At times like this, I have turned to a script in PixInsight called WBPP.  It's kind of a one stop shop for all the calibration steps you need to put together an image which you can then carry forward to the remainder of the processing stages.  Some people use it all the time for all their images.  Others, like me, only use it occasionally.  Either way, I thought it would be useful to include the workflow I use in this document if I go down this route.  Something to be aware of though, these scripts are updated quite regularly, so appearance can change and the screenshots will be outdated.  But, the principle of it will generally stay the same, so with a bit of a rummage around you can still get it working quite well.

Post Stacking Processing

Depending on what filters I have used to collect all my data during the imaging run depends on which processing workflow I use to work on producing my image.  This document goes through a typical workflow I go through if I have been using either no filters, or something like a light pollution filter.

Post Stacking Processing - Quadband

My most recent addition to the astro hardware cupboard was been an Altair Quadband Filter for use with CMOS cameras.  This, in combination with my Altair 183c Hypercam has kind of revolutionised my image processing and brought me on a step when I started learning more about it over the last couple of years.  I was able to add in a different set of techniques to my workflow which I have put into this document.

Preparing for HiRes Printing

At the end of all this, hopefully you have an image you are pleased with.  Some people decide they are so pleased with the image that they want to print it our.  This is a whole other ball game and you can quickly disappear down into a rabbit hole of different colour profiles, printer types, resolution etc.  Admittedly, these aren't steps I do very often, but I put a couple of pointers in this document on how to perform some initial steps on getting your image ready to print using some features in GIMP

So, there you go.  The end of another post which I hope is full of information and resource that others might find of interest.  Of course, comments are always welcome (but moderated before being posted) and I'm always interested to hear from others on things they might do different, what works for them and what doesn't work.
Thanks for your time and clear skies!

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.