My new deep-sky imaging setup

 Deep Sky, Equipment, General Astronomy  Comments Off on My new deep-sky imaging setup
Sep 292021
 

Since the early Summer of 2021 I have been building up a new deep-sky imaging setup based around the beautiful and venerable Takahashi FSQ-85EDX Refracting telescope. I’ve always wanted a ‘Tak’ and decided to go for this model known ad the ‘Baby-Q’. The optics are glorious and the focuser is incredibly rugged and can carry heavy cameras and filter wheels.

The idea, eventually, is to turn this setup into a fully robotic system which will be mounted low to the ground and housed in a simple box-like structure with a sliding roof. For now, I’m testing out the system to see how it performs.

Here is a small gallery of photos of the current system. I will add more details about the components below.

Here’s a list of the main components that you can see in the above photos:

  • Telescope: Takahashi FSQ-85EDX F/5.3 Apochromatic Refractor with 1.01x field flattener.
  • Mount: Skywatcher AZ-EQ6 Pro
  • Camera: QHY268C cooled CMOS camera (one-shot colour, full 16-bit)
  • Filter Wheel: Starlight Xpress 5 x 2″ filter wheel
  • Guide Scope: ZWO 60mm. Focal length is 280mm, F/4.67
  • Guide Camera: ZWO ASI290MM Mini mono
  • Auto Focuser: Pegasus Astro FocusCube2
  • Power, Dew Heater and USB Hub: Pegasus Ultimate Powerbox V2
  • Dew Heater bands on both scopes
  • Windows Computer: Beelink Mini PC (in the plastic box on the ground running N.I.N.A.)

If you look at the photos with all the cabling, you will see a plastic box on the ground below the mount. This contains a ‘headless’ mini PC running Windows 10. Think of an Intel NUC and you will get the idea, but this is a Beelink with an Intel i5 CPU which comes cheaper than a NUC. This computer has all of the software installed to control the rig. I’m using the free N.I.N.A. software here and the little PC is connected to the wireless router I have in my dome just a few feet away. This allows me to use remote desktop from the comfort of my dome, office or house.

The thing that really was a ‘game-changer’ for me is the Pegasus Powerbox which is mounted just below the lens of the main scope. This provides all of the 12-volt power ports I need to run the various bits of kit and also has a USB hub with 6 ports. Additionally it can power and control the heat of three heater bands and can detect the dew-point so that it can intelligently adjust the power to the bands to keep the lenses free from dew. Because nearly everything connects to this hub, there are only two cables that need to be connected to the big plastic box on the ground. One is the 12V power to the hub and the other is the USB3 port to the Beelink mini PC.

I run the amazing free N.I.N.A (Nightime Imaging ‘N’ Astronomy) software on the mini PC and the recently added Advanced Scheduler is amazing allowing me to power up the system before dark and set up various targets to image during the night. The system will do everything such as cooling the camera, auto-focusing, slewing and centring targets, flipping across the meridian and shutting down at dawn. It can also deal with re-focusing during the night if the focus drifts and re-centring after a cloudy spell.

Assuming I get some clear nights over the Autumn months, I will hopefully be posting some new images soon.

 Posted by at 3:21 pm

The Veil Nebula – a mosaic

 Deep Sky, General Astronomy, Image Processing  Comments Off on The Veil Nebula – a mosaic
Sep 292021
 

The beautiful Veil Nebula in the constellation of Cygnus (the Swan) covers a large apparent area of the sky. When I say ‘large’ I mean it in a relative way. It covers a large enough area to make it hard for the average telescope to cover in one frame. To put this into perspective, the full Moon (or the Sun) is about half a degree across, but we need a field of view (FOV) of about 3 by 3 degrees to encompass the whole of the Veil Nebula. Thus, we can say that the full Moon would fit about 6 times across the apparent span of the Veil Nebula.

I have a lot of different telescopes and cameras! Some telescopes, such as the popular Schmidt Cassegrain design, are good for viewing the planets and small galaxies, but these typically have very small FOVs because they have long focal lengths to provide the high magnification which we need to see the belts on Jupiter, the craters on the Moon, or the rings of Saturn. Think of these telescopes as the telephoto lenses of the astronomer’s toolkit. Then there are the shorter focal length, smaller telescopes. These are the type (typically small refractors) that can give a wider view of the starry sky and they are ideal for delivering a larger FOV on to the camera’s sensor. However, only the smallest of these could cover the 3 by 3 degrees we require, and so I have resorted to the technique of imaging one half of the Veil Nebula on one night, followed by the other half on another night! I used an using an 85mm F/5.3 refractor. The two sets of images are ultimately processed and seamlessly joined together in a mosaic to show the Veil Nebula in one final image. Although this sounds complicated, there are advantages to this approach as the final image provides a much higher resolution of the target than could been obtained with a telescope that could fit the whole thing in in one go. The final image ends up with more pixels too.

The Veil Nebula is a Supernova remnant. The star that blew itself to pieces was 20 times more massive than the Sun and was just over 2,000 light years away. This cataclysmic event happened about 10,000 years ago. The remaining remnant structure is about 110 light years across and contains the beautiful glowing filaments that you can see in the image. The red colour is caused by ionised Hydrogen atoms, and the green from doubly ionised Oxygen atoms. The filter that I used to capture this image allows light of these two colours (wavelengths) to pass through, but cuts off everything else, including general light pollution and moonlight etc. Astronomers call this narrowband imaging.

Click on the image below to see a full-sized version.

 Posted by at 9:48 am

Three new images from the summer

 Deep Sky, General Astronomy, Image Processing  Comments Off on Three new images from the summer
Sep 282021
 

Here, on the south coast of England, the nights get very short indeed for a couple of months around the Summer Solstice. In fact, there are several weeks where theoretical ‘astronomical twilight’ never ends and the Sun never drops below 18 degrees below the horizon. I normally abandon deep-sky imaging but, this year, I was testing out a new system and decided to have a go at a few easy and classic Summer deep-sky targets.

The main thing that helped my productivity during these short nights was a new dual-band narrowband filter from Optolong called the L-Extreme. These multi-band filters are becoming very popular with deep-sky imagers these days. The pass-band spectrum graph is shown below, and you can see that there are two peaks – one centred on H-Alpha and the other on OIII and both are 7nm wide.

I’ve been imaging with Ha, OIII and SII narrowband filters for many years, but so often in the past I have been unable to capture a full set of sub images due to poor weather or lack of time, and this filter brings the possibility of acquiring more finished images as these three testify. By the way, the SII band is not included with this filter but, so often, the SII signal is so weak it rarely adds much to an image. However, since I have this filter in my filter wheel (so that I can use a Luminance filter for RGB imaging) I still have the option of adding my SII filter into the mix if I so desire.

I should mention that these narrowband filters are generally used with one-shot colour cameras. The Ha signal ends up in the red channel and the OIII signal is often mixed between green and blue. My new system includes the amazing QHY268C one-shot colour cooled CMOS camera which is very sensitive and has 16-bit resolution.

I will add a separate article showing the new setup, but it includes the superb Takahashi FSQ-85EDX APO refractor working at f/5.4 riding on a Skywatcher AZ-EQ6 Pro mount. The field of view is 179′ x 120′ which is 3 x 2 degrees (1.72 arc-seconds per pixel).

All three images consist of just over 2 hours of exposures – that’s all the darkness I had on each night! I took 600 second exposures throughout and calibrated with dark, flat and flat-dark frames.

Please click on each image below to see the full size of the images (which are only 50% of the originals).

The first image is the North America Nebula in Cygnus (NGC7000)

The second is IC1396 in Cepheus which contains the Elephant Trunk Nebula near the middle.

Lastly, NGC6888, The Crescent Nebula in Cygnus which is sometime referred to a van Gogh’s Ear!

Hopefully, my next article will not be too long coming. Thanks for reading.

 Posted by at 11:00 am