AstronomyWood: September 2020

Otherwise known as using a mono camera with narrow band filters.

My location is a Bortle 7 or 8 class location dependant upon which app you use. This means I have heavy light pollution from lots of sources. When using a one shot colour camera (OSC) or DSLR camera I use either an IDAS IGAD LPS-D2 or Altair Astro Triband filter. The former filters out light pollution including LED street lamps which are prevalent in my location leaving a very decent RGB image. The latter does the same but filters out everything apart from Hydrogen alpha, Oxygen III and Hydrogen beta.

IDAS LPS-D2 filter works great on LED street lamps

Altair Astro Tri-band Filter

Obviously with a OSC camera you have to take longer exposures, more exposures or a combination of both to acquire enough data to be stacked. This is due to the Beyer colour matrix of RGGB covering the monochrome sensor.

However in a purely monochrome camera you have no Beyer matrix to contend with and consequently due to this lack of colour filtration on the chip you have 4 times the sensitivity to light. All you have to do is filter out the wavelengths you don't want and the sensor can be used to capture the light you do.

Step forward the ZWO ASI 183MM, ZWO EFW electronic filter wheel and a set of narrow band filters. In my case the ZWO 7nm Mark II set of 31mm unmounted NB filters. Not the best but if you are on a budget they are fine and produce good results.

ZWO ASI183MM Pro cooled dedication astronomy camera

The filter wheel and filters came first as they were in stock from two UK astronomy suppliers, Widescreen Centre in Ely, Cambridgeshire and FirstLightOptics in Exeter, Devon respectively. However due to the Covid19 induced manufacturing problems affecting deliveries from ZWO in China the camera came several weeks later from Telescope House.

ZWO ASI EFW5 5 position electronic filter wheel

Fitting all the bits together was a doddle as all the parts are included in the boxes from ZWO.

After the inevitable clouds for a few weeks first light was on August 30th 2020 and I managed to image the Crescent Nebula in Ha. I got a good quantity of subs and the camera was set at default 111 gain and 8 offset.

Crescent Nebula in Ha

I had to wait for over 2 weeks to get Oxygen III and Sulphur II to complete the image acquisition but it was worth the wait.

Crescent Nebula in Ha, OIII and SII

I have gone through quite a few applications to choose the right one suitable for my needs so far and list them here.

BackYard EOS - 2012

Starting in 2012 I got an early version of BackyardEOS from OTelescope. I attached my Canon 400D DSLR to my Dobsonsian and took a few pictures of the moon and then forgot about it.

In 2019 my passion for astronomy was reborn and I got a goto equatorial mount the HEQ5 Pro with Rowan belt modification. I paired it up to a William Optics ZenithStar 73. Again I updated my BackYardEOS to the latest version, had my DSLR astromodded and set off taking a few pictures.

At this point the mount was just being controlled by the handset and I was using the capture software purely to open the shutter using a Shoestring Astronomy DSUB box.

ASCOM and EQMOD - 2019

I discovered ASCOM and EQMOD by reading up articles on the internet and bought the nexecassry cables to connect my computer to the mount.

Initially I used Cartes DU Ciel to control the telescope but found it a bit clunky. So I moved on to Stellarium and StellariumScope to control the mount via ASCOM/EQMOD. This proved to be the right way to go.

AstroPhotography Tool - 2019

I stumbled across this software purely my watching AstroBackYard on Youtube where Trevor Jones advocated the use of it. It is reasonable cheap to buy and has a nominal yearly maintenance cost.

I used AstroPhotoGraphyTool for quite a time and used it with Platesolve2/ASTAP to accurately position the telescope. Also I upgrade to a OSC cooled camera and a guide camera to produce better results. Again this was paired with PHD2 guiding software to give the ability to produce longer guided exposures.

All the time whilst using the Windows based software solutions I had the laptop outside in a box and was concious that there must have been a better way to do this without tying up a computer in the elements.

RaspberryPI4 and Astroberry - 2020

I saw a lot of people on various forums were extolling the virtues of using the inexpensive Raspberry PI outside and some were using Astroberry. This is loaded with Astronomy software and is maintained on a free open-source basis.

Astroberry is a full flavor remote desktop system, designed for Raspberry Pi. The system can be accessed via a web browser or VNC client from any location in the world! It sits at your telescope, wherever it is, and lets you remotely control all your astronomy equipment from behind your desk, using recognized astronomy software such as KStars, Skychart/Cartes du Ciel or Stellarium. You can slew your telescope by simply clicking on a skymap, change focus, capture images, plate solve images and much more!

KStars/EKOS - 2020

As the Astroberry comes with Kstars I decided to trial it and found out that there was no need to use anything else as my equipment could all be controlled with the INDI drivers that were installed.

EKOS is the scheduler system that works just like Windows based software such as Sequence Generator Pro.

An EKOS sequence can be setup that does the following (and more):

Slew the telescope to your desired target
Platesolve to get it very close
Change the filters in your filter wheel
Cool the camera and control all parameters of it
Guide the telescope using an internal guider or PHD2
Take a sequence of shots performing a meridian flip if required
Change to another target and repeat the process
Shutdown the observatory and close the dome etc
Take flats, darks.

It can do all this and more automatically.

It was a no brainer and as the PI takes up little room can be mounted inside my power supply box along with an ethernet switch. Astroberry can also use wireless connections for use out in the field for instance.

So in a relatively short period of time I have changed the way I acquire images. The most significant part is I have gone away from a Microsoft operating system to a Linux operating system.