Category Archives: Equipment

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The source to the halo around bright stars

When I moved to the Sky-Watcher Quattro telescope I noticed some bizzare halo’s around bright stars in my images, this was evident in both my Atik 383L+ CCD Camera as well as my QHY183M ColdMOS Camera, if you browse my galleries you will see what I mean, and it was more noticable in my Narrowband images. Below is one of my recent images where you can see the halo around Magnitude 3.9 star 15 Mon in the Christmas Tree Cluster / NGC2264.

I contacted Baader back in February 2019 since all of my filters were Baader, and I noticed that the Halo was present in all of my filters but significantly less in Red, but more prevalent in Narrowband filters, so the logical cause would be the filters. Baader immediately dismissed this to be the fault of their filters and suggested that my Coma Corrector be the root cause.

Not convinced that the Coma Corrector was causing the issue, I did some research online and came across a brilliant page on the Astronomik website where they claim to have resolved the majority of the Halo issue, and after reading the following line from the page I was convinced the filters were my issue:

In recent years very fast optical systems have become popular for imaging. The energy in a filter induced halo grows exponentially as the f-ratio decreases. Additional to this, the smaller the FWHM band pass of the filter, the stronger the halo.

The above line described my issue perfectly so I mentioned this to Baader who again dismissed the possibility of it being their filters and again put the blame firmly to my optical train. Again not happy, I contacted Astronomik and Eric emailed me back very promptly and offered to send me out one of their 6nm Ha filters to test. A few days ago the filter arrived and I was able to perform some testing against the Baader filter also for comparison on the same star.

Since the star in my image above was of magnitude 3.9, I wanted to find something similar, so I found star Alhaud VI and proceeded to obtain 15x300S Exposures for each filter, and here are the results:

Astronomik 6nm HA filter, 15x300S with Darks and Flats applied
Baader 7nm Ha filter, 15x300S with Darks and Flats applied

So as you can see the Baader filter shows a high amount of Halo around the bright star and the Astronomik filter does not, now if this was something to do with the rest of the optical train there would be evidence in the Astronomik filter also.

Now I agree there will be some reflection in the optical train, all that glass in the coma corrector, the glass on the camera etc, so I thought I would have a look at both images in a bit more detail, zoomed in on the stars there is what appears to be a slight halo in the same place on both images:

Astronomik 6nm Ha Filter
Baader 7nm Ha Filter

So both filters show the Inner Halo which in my opinion would not be visible in an image, but again clearly the Baader filter has some reflection issues happening as you can clearly see two additional Halos. The interesting thing about all three Halos is that the central one visible in both filters has no relationship to the distances between the other two in the Baader, however the two outer Halos on the baader are the same distance apart as the middle halo is from the star, so clearly this is some sort of reflection.

Astronomik have done a fantastic job at eliminating Halo artifacts around bright stars, clearly the Baader filters are causing major Halo artifacts because if this was the optical train then it would be evident in the Astronimik filters also, I suspect that the Baader filters are not optimised for faster focal ratio imaging systems. I have provided this information to Baader and await a response from them.

Good job Astronomik Filters

PrimaluceLabs Sesto Senso Robo Focuser

Getting the best FWHM in your images is something that I have struggled with when imaging a whole night. As the temperature fluctuates, so does the FWHM in your images, this was a problem I had with my images at the beginning of the season. I looked around and the only focuser I could find was not a stepper motor focuser, so it didn’t offer predictable results. Since I am using the stock focuser for my Sky-Watcher Quattro 8-CF (and it’s a solid focuser at that), I did not really want to change focuser mid-season, so I did some research and landed upon the PrimaluceLabs Sesto Senso ROBO Focuser.

Now my expectations here were pretty low since I tried an electronic focuser and tried to use some sort of Auto Focus routine without any length of success, but when the Sesto Senso arrived I was excited as I looked at it and thought to myself that this would do the job.

Out of the box the Sesto Senso is very solid, good quality feel to it, and came with a bunch of different adapters for different focusers, one specifically for my Sky-Watcher Focuser too. I read the installation instructions a couple of times and set to work on upgrading my scope.

Installation was fairly easy and straight forward, I removed the slow focusing knob off the focuser and attached the adapter for the Sky-Watcher that came with the Sesto Senso, so within 30 minutes it was successfully fitted. And I can still manually focus with the fast focusing knob on the other side of the focuser:

After all the physical installation was done, I then needed to install the software on the observatory PC, since I image using Sequence Generator Pro, I proceeded to install Sesto Software and the ASCOM driver so that SGPro could talk to the focuser, again this was relatively simple to do. Once this was completed it was important to load up the Sesto software and perform a calibration so that the Sesto Senso knows where the most innner and outer focus positions are.

Setting the Focus Control module in SGPro was a breeze, for this I used a Focusing Mask to get a rough focus and set that point for all of my filters, now the following setting are what works for me really well, but basically:

  • I use 20 data points to achieve focus.
  • Step size between focus points is 20
  • Focus frame is 10 seconds for all filters, this is to get a better normalised focus frame, I was finding 5 seconds was too short and gave un-predictable results.
  • I set it to re-focus after a temperature change of 3.0 Degrees C since the last focus.
  • I re-focus on any centering action which is useful if you use a mirrored telescope like me.
Sequence Generate Pro Auto Focus settings
You can see here that my start off point is 50146, so it will go 10 points either direction of this point at 20 steps per point

I have now been using the Sesto Senso for a few months now and it has not failed me, I maintain a good FWHM value throughout the night and it an awesome piece of kit, well done Primaluce Labs. Is there anything that I would change about it?

Only one thing…….It requires separate power, which in all honesty I can understand why but if I could run the power through USB that would be a bonus.

One problem I have with the Auto Focus routine in SGPro is that in the image sequence, since my filters for LRGB are all parfocal, but my Narrowband filters are not, I only wish to focus on a filter change if it’s going from LRGB to Narrowband to LRGB or Narrowband to Narrowband, unfortunately SGPro doesn’t have that intelligence in the sequence, I am trying to persuade Jared to have that in there to make life that bit more simple.

Anyway I hope this review inspires you to consider this awesome piece of kit, it’s certainly helped me!

Pegasus Astro Ultimate PowerBox

I spent a lot of time looking at PowerBoxes/USB Controllers, the late Per Frejvall had developed a very nice Remote USB Hub but of course with the passing of Per, these are no longer available. I looked at two hubs, the HitechAstro Mount Hub Pro abnd the one I settled for was the Pegasus Astro Ultimate PowerBox.

Unboxing the PowerBox I was pleased with the build quality, they even ship mounting brackets for you to be able to mount it onto your setup, here’s an image of mine mounted on top of my Sky-Watcher Quattro:

Pegasus Astro Ultimate PowerBox on Imaging Setup

I loaded up the software onto the observatory PC and again pleasantly surprised at how easy it was to get started and configure the names of the powered devices connected as well as names for each of the dew heaters, in the following image you can see my power connected devices and my dew heater for my guider camera:

Screenshot of Control Software

I configured the software to automatically power my devices the moment the unit is switched on, so what do I have connected to the PowerBox?

  • QHY5L-II Guide Camera
  • StarlightXpress USB Filterwheel
  • PrimaluceLabs ROBO Focuser
  • EQ8 Pro Mount PC-Direct Cable

I didn’t connect my QHY183M at the moment as I discovered that during image download it seemed to cause a timeout on the QHY5L-II Camera, I have raised a ticket with Pegasus Astro on this one. From a Power perspective, I only have my QHY183M and my Rear Fan assembly/heater connected as I currently do not have the power cable to connect directly to the hub for the EQ8 Pro (On Order). There is also a temperature sensor for the ultimate version, which works well as an interface for Sequence Generator Pro and my Auto Focuser routines.

I have been using the Hub now for a good few months, I am pretty happy with it, am I totally happy you might ask, well to be honest there’s a couple of niggly things that I have emailed Pegasus Astro about (awaiting a response):

  • Voltage. I am running 13.8V regulated bench power supply capable of delivering up to 15A which is powering the hub, however when devices such as the camera, dew heater, fan assembly are all running, the voltage level drops down to around 12V according to the software, I would not expect this to do so, I would expect it to remain 13.8V. My EQ8 Pro mount is powered by the same supply (but not through the hub currently) and during slew the voltage in the software does not change, so it’s obviously something being caluclated within the hub somewhere.
  • Issue with USB3 Camera (QHY183M) is still outstanding
  • When you set the power to the dew heater for example I always run it at 170, however when the software restarts you have to manually go and set this again
  • Ability to reboot or “Disconnect” a specific USB Port remotely would have been nice.

The main reason I wanted something like this was the ability to reboot the hub remotely, with standard USB Hubs this is not possible, as above, I would love to have a bit more granularity on this and have it on a per USB port but it works well for me right now.

My Observatory MkII

After deciding to move my equipment from the farm to home, to make my imaging tasks a bit easier, I decided I was going to design and build a roll-off roof oberservatory this time, this will allow me to possibly automate the roof later on, so for this I first had to dig down by 3ft in order to build the base for my Pier, inside this 3ft was also re-inforced bar going out to different angles to the surrounding earth and also straight down into the ground below the 3ft hole, it was then poured with concrete and the template for the steel pier bolts placed resulting in the following:


The base was an 8ft x 8ft base, but my observatory design was to be an 8ft x 6ft because I did not plan on being present in the observatory during imaging so I did not need that much space around the equipment, as you can see my garden slopes down quite a bit too.  The bricks around the outer edge were purely to allow me to pour concrete down the edges to get a smooth finish on the outside prior to be filling the whole base with concrete.

A few days later, the concrete arrived and was poured into the base resulting in the following image showing the concrete “Curing”


After the concrete had cured, I used a thin film of leveling compound on the observatory base just to give it a much cmoother floor and allow me to paint it with a nice clean dark grey concrete floor paint, and once dried I started constructing my observatory which resulted in the final build below:


As you can see from the above image and the image below, I still had my Astro-Tech AT8RC which I have parted with in favour for an F4 Quattro Reflector which is now my primary imaging scope


I am extremely happy with the observatory, I am working through a design to allow the automation of the roof as well.  In total the construction of this obervatory took me no less than a few days to complete, I hope this inspires you folks out there contemplating building your own to get out there and do it!

My Observatory

For those people who are looking to have a more permanent setup for their equipment an observatory is more likely to be on the cards, when I lived in Ireland I had my NEQ6 Pro on a steel pier covered by a special cover to protect it from the elements, when I moved back to the UK I had the perfect opportunity to build an observatory to protect the equipment and not have to keep remounting the camera and scopes for imaging, this is what my setup looked like in Ireland:


When I originally moved back to the UK I had the observatory located on a familly farm where I built a “Bat Wing” style observatory, this took shape by digging a 3ft hole for the pier


Then building the base around the Pier Concrete:


Then constructing the double skin walls around the base:


Once the base and sides were constructed, the per was put into place


And the final result was this:


Since I built this observatory, I have now built another one at home with a roll off roof, which worked out better than the Bat-Wing style, see here for details.

Cooling a DSLR

In the days I used a Canon 500D to produce my Astrophotography Images I set upon a quest to reduce the amount of noise in my images, it would then allow me to capture less frames because there was less random noise to filter out.

In my quest I came across a blog post by Gary Honis on how to cool a DLSR Camera used for Astrophotography, so I followed the information and produced a cooler box.  The design by Gary is to cool the air around the camera whilst in a box.  I built my cooler box but could not yield any substantial results in effectively cooling the CMOS Sensor, so I decided to start from scratch.

Since I had done the Astro Mod to my camera previously, I knew the insides of the camera fairly well, so I thought to myself that there must be a much better and more efficient way of cooling the sensor a little more directly rather then cooling the air outside the camera, I remembered that there was an aluminium shield covering the back of the imaging sensor, so I started working on my cooling system, for this project I puchased the following:

  • A Plastic electronics Project Box with Lid
  • A 1 Square Metre sheet of Mylar
  • An Intel Xeon CPU Cooler
  • A Fan Speed Controller
  • A 20mm x 20mm aluminium block
  • 2x Silica Gel Moisture Absorbing packets
  • 1x 12v Converter for the Camera to replace the battery pack
  • 1x Thermal Heatsink Compound (Arctic Silver)
  • 1x Peltier Thermo Electric Cooler (TEC)

In order to allow the direct cooling of the sensor, it was neccesary to remove the rear LCD Assembly of the camera, which you would not be using anyway as the camera would be in side the box.

The following image shows the actual box assembly with the aluminium cooling block, you cannot see the TEC or CPU Cooler from this angle, but the CPU Cooler was spring loaded to prevent the cooling block crushing the sensor shield, in here you can also see the Mylar as well as the USB Cable for the camera and also the 12v battery convertor for the camera.


The next image you can see the camera cooling box next to the camera where you can see the aluminium shield that the cooling block will directly connect to in order to provide the direct cooling, I also placed some Arctic Silver Heatsink paste here to allow better thermal transfer


When the box was finally assembled, a couple of silica gel packs were included to absorb any moisture inside the box after the box was closed, there was no way for air to leak inside as all cable holes were sealed with sealant also, below is an image of the cooling system complete and attached to the telescope


Since I used to use Backyard EOS to acquire my images when using my DSLR it would report the sensor temperature for each frame acquired and with this design I was able to effectively cool my sensor to at least -20 even with the XEON cooler fan set to minimum during the winter and medium speed during spring.

Since I moved to my CCD Camera a few years ago now, a friend bought my cooled camera from me and it is still going strong and working great