Haw Wood star party

The skies didn’t clear until 4am on Sunday during the weekend of the Breckland autumn star party at Haw Wood Farm. By then the winter constellations were rising and this posts subject makes an early appearance this year.

I’d gone equipped with the Astrotrac and Canon 75-300mm zoom lens. Using this with the QHY9 camera requires a Geoptik adapter between the two. As the focus adjustment on this lens is so sensitive I’d previously purchased a set of fine focus rings that clamp to the lens and provide a fine adjustment as well as locking the focus once achieved.

Before the sky got too light I acquired 11x 5 minute frames of the belt region of Orion along with some dawn sky flats. Processed in Pixinsight.


Lynd’s Bright nebula 534

I last attempted this object last year using the Zenithstar 70mm and resolved to make another attempt with more exposure and a darker sky. This year I’ve assembled a lot more exposure time (8 hours in 10 minute sub-frames) over several evenings using the Baby-Q. The location is still my garden though so I didn’t manage to find darker skies.

LBN534This time I’ve managed to capture more colour in the stars. In addition to the main nebula there are also fainter dust clouds visible in the image this time.


Setting up a Pulsar Dome (Pt 2)

In part 1 we looked at getting a Pulsar dome to follow movements of the telescope when slewing from within Cartes Du Ciel. This time we’ll build on this foundation and add Maxim DL to the mix.
Recall from part 1 that both EQAscom and Shelyak dome driver have only POTH connected to them. POTH intercepts mount movements and calculates dome movements to match. This is required as the planetarium does not have the ability to connect to a dome.
Maxim DL does have the ability to directly control a dome so by connecting it’s dome output to POTH we can control the dome either via Maxim or the planetarium. POTH acts as a hub enabling us to connect more than one program to a single device. The telescope device EQAscom also acts as a hub and multiple programs can be connected to it so we’ll select EQAscom directly as the telescope device in Maxim. The main reason behind this is that we can’t use pulse guiding if Maxim is connected to POTH; it must be connected directly to EQAscom. In addition, as we’re sending dome commands from Maxim we don’t need POTH to intercept mount movements.
All of the dome slaving measurements that we made previously have to be entered in Maxim as well from the Options button on the dome tab of the observatory window. The setup screen specifies inches as the unit of measurement but this is not important provided the same unit is used for all values within this screen. Don’t forget that the dome size is specified here as the radius and not diameter.
The telescope type should be set manually as German Equatorial and the pier side as ASCOM Normal. These setting are available from the observatory setup tab’s Options button.
The dome home azimuth can be set but leave the sync option unticked as the driver will do this for us.
And that’s it! Additional programs can be connected provided you follow the same rules as we’ve adopted here for Cartes Du Ciel and Maxim. If you’ve entered all of the measurements and the home azimuth position accurately then the dome should follow the telescope as it slews and tracks around the sky driven from both Maxim and your planetarium program.

Setting up a Pulsar dome

Having recently worked through the issues of slaving a Pulsar dome to a telescope and helping someone else through the same process I thought it would be useful to document the setup here.  I have an Avalon Linear Fast Reverse mount but from a software point of view this is identical to an EQ6 and I use Maxim DL for image capture, CCD Commander for automation and Cartes Du Ciel as a planetarium. With a few peculiarities, the setup is applicable to other programs that you may be using.

The first step is to run the Shelyak Test_DomeTracker.exe program. This is supplied on the CD and you’ll need to run ‘Do Calibration’ several times. What you’re looking for is that the number of steps per rotation remains very similar from run to run. Any large differences here means that mechanical problems are causing you to lose steps. This must be rectified before continuing. Make a note of the number of steps per rev and acc/decc steps obtained.

Next up we need to run POTH which is available in Scope-Dome hubs under the Ascom Platform 6 program group. We need POTH because we can only connect one program to the Shelyak ASCOM driver. With POTH, we connect it to the dome driver and then connect our other programs to POTH. There’s a fair amount of information to add to the dome setup screen and it will require some careful measurements of your mount and pier and it’s position within your dome. Within POTH, click Setup. If dome data isn’t displayed then press Dome>> to expand the screen.

Click ‘Choose Dome’, select the Shelyak ASCOM dome driver and click Properties.

Capture1Enter your COM serial number, then look at the Dome Azimuth settings. Enter the values you obtained from your calibration runs, your best guess for the home azimuth position and the dome diameter (in metres). Now we need some measurements from your dome and mount so a tape measure will be required.

All measurements are made from an imaginary point at the intersection of RA and DEC axis on your mount. This will be inside the body but make an estimate of it’s position. From this point make the following measurements:

  1. Any East-West offset referenced to the dome. Usually this is zero but check to make sure
  2. Any North-South offset, again referenced to the dome. If there’s any offset, it will usually be to the south so this will be entered as a negative number
  3. The height of the intersection above or below the base of the dome hemisphere

All these measurements are made in metres and are entered in the relevant dialog boxes under ‘Telescope position wrt dome’.

You’ll need one more measurement; the distance between the intersection and the optical axis of your telescope. Don’t forget that a top mounted guide scope will significantly increase this distance. This is entered as the German mount offset and you’ll also have to set the mount management here as per the illustration above. Click the OK button

Once all this information is entered you’re most of the way there. Now we check the home position azimuth that you entered.

Start the test_ASCOM_DomeTracker.exe program from the CD, check the Setup dialog to ensure the information you entered is all correct and then Connect.


Park the mount so it’s pointing due north and using the Actions buttons in the program ‘Find Home’. The dome should move to it’s home position with the silver tape in front of the sensor. Next Slew to AZ 0 degrees and the dome slit should end up directly in front of the telescope. Failure at this point indicates that either your tick count or home position is incorrect. As you’ve carefully made multiple calibration runs earlier we’ll assume it’s the home position. Using the setup dialog, make an adjustment to the home azimuth setting and re-home the dome. Slew to AZ zero again and compare the dome position to the previous position. Repeat this process until the dome slit stops reliably in front of the telescope when slewed.

With all this done the dome should be set and it’s time to bring the mount into play. Once again, like the dome, we will connect POTH to the ASCOM mount driver and then connect other programs to POTH. The reason for this is that POTH will intercept mount moves for us and command the dome to move as well to follow the telescope pointing. Using the POTH setup screen choose the EQ6 driver, setup and then connect. The screen should look similar to this:


Note that you need to enter your mount/dome measurements again in the Geometry section. Pay attention here as this time the dome radius is required.

In your planetarium program (for this example we’ll be using Cartes Du Ciel) open the telescope dialog and select the POTH.Telescope driver.

Capture4Once you’ve pressed the Connect button, slews initiated within the planetarium will move both the telescope and the dome in sync.

In Part 2 I’ll look at connecting Maxim.


It’s been a while since I posted here. A good part of that has been the summer weather and general lack of night time at UK latitudes. I’ve also has an observatory build project running which has consumed time but is now nearing completion.

My last post mentioned the globular cluster M4 in Scorpius. M4 never gets very high from the UK and the window of opportunity for taking pictures is really small; really limited to just one new moon period in early summer. The southern horizon at Suffolk was exceptional and whilst scanning the sky with binoculars I noticed that this object was looking as good as I’ve ever seen it from the UK. Due to an oversight when parking the van and setting up the telescope I had the onsite wind turbine directly to the south so had to wait a short while for M4 to clear this and then took 3 10 minute exposures.

With M4 only 10 degrees above the horizon light pollution is normally a big problem and when looking at these images it did appear that I had a sizeable gradient across the image. However, further processing revealed that this is the due to the reflection nebula around Antares (just out of frame) and not the more usual sodium lighting.

…and the AirMass (Relative optical path length through atmosphere) at 10 degrees altitude? 5.1.


The Suffolk Coast

A bank holiday beckoned and the forecast was much better on the coast for Saturday night so we packed the van and headed for a new destination near the club dark site at Haw Wood Farm. This site is a little further south at a small village called Middleton and closer to the towns of Leiston and Saxmundham than Haw Wood but the light pollution was still pretty minimal for the UK. The site is a Camping & Caravan club certificated site called Golden Acres. It’s a grass field with good horizons spoilt only by a small wind turbine in the middle so site your telescope carefully. The light switches for the toilet block were easy to find and I turned them off after everyone else had gone to bed after midnight and the full beauty of the sky here was revealed.

I started with some more images of my current galaxy project (NGC 4236) but once I’d realised that M4 was an easy binocular object even though it was only 10 degrees above the horizon I took a few 10 minute frames before it got too low. It did feel slightly odd taking pictures with the telescope tube almost horizontal and this is something I’d not be able to do at home with the Thetford light pollution due south of me.

The last picture I took was on the Sunday morning just as the sky was beginning to lighten after 2am. This is the Small Sagittarius Star Cloud (M24) and it was only 18 degrees above the horizon. This is a single 10 minute frame taken with the QHY9 and the Baby-Q, processed with Pixinsight.

Small Sagittarius Star Cloud
Small Sagittarius Star Cloud

…and the Whale again

I’m beginning to feel some understanding with Captain Ahab and his obsessive tendency towards Cetacea. This has been rather a mission this spring and with weather keeping the imaging sessions short I’ve had to keep returning whenever possible.

The last two sessions I’ve experimented with increasing the subframe exposure time to 20 minutes. This has some major benefits in increasing the signal to noise ratio with some downsides in increasing bright star saturation and reducing the number of exposures to stack. Some further improvements may be gained by going to 30 minutes but, having shot 9 hours worth of 20 minute dark frames the other night I may as well get some use out of them. A darker sky may be required as the exposure length increases.

To incorporate the new exposures in the existing stack I’ve simply calibrated them and then scaled by 50% using PixelMath to match the existing 10 minute subframes.

I’ve worked rather harder in Pixinsight to retain star colour while, at the same time reducing the colour noise in the background. Star masks are invaluable in this and they’re really easy to create using Pixinsight.

This marks the end of data collection on this target for the year as it’s now past culmination by the end of astronomical twilight and the nights are getting shorter. Total time on this is now about 8 hours.


Back to the Whale

A clear evening, the moon approaching third quarter and a long weekend courtesy of the Easter bank holiday; what to do…

No debate really; add some data to my Whale and Hockey Stick picture. Originally started at the Kelling Heath star party, I’ve subsequently added another 2 hour set and this was the third, taking me up to 6 hours in total.

NGC4631Replacing the Belkin USB hub with a Startech has stopped the lockups of the guider. I’ve still got a dry solder joint to track down in the power supply somewhere. I have my suspicions but I’m aiming to replace the cigarette lighter sockets with something a lot more substantial in the near future.

Stacked in Maxim DL

Processed with Pixinsight

Three in Coma

Despite a first quarter moon in the sky I couldn’t pass up the chance of a clear night so last Tuesday I set up in the back garden. Things didn’t go exactly to plan and a Netbook reboot at 3am for Windows updates cost me a few hours but I did get 2 hours 20 in 10 minute subframes of a galaxy triplet in Coma before then. The central galaxy is NGC 4216.

NGC4216_DBEAs this is part of the Coma cluster there are a lot of other galaxies in the field as well.

Processed in Maxim DL and Pixinsight.

The Whale and Hockey Stick galaxies

In between the high cirrus clouds that were prevalent over the Kelling star party last weekend I got a couple of hours worth of exposures of these galaxies in Canes Venatici. (ngc 4631, 4627, 4656 & 4657). Because they’re both fairly large at 16 arc minutes¬† they make a nice combination for the Baby-Q and QHY9. This combination produces a pixel scale of 2.475″/pixel which is a little coarse for imaging the finer detail in galaxies but with the UK’s pretty average seeing conditions probably isn’t too under-sampled most of the time.

The Hockey stick has two NGC numbers; 4656 which is the core and 4657 which is the bright knot at the distorted eastern end. This distortion is due to interaction with the Whale and both galaxies are at a distance of 30 million light years.

NGC4631-cropAcquiring some more data will help bring up more faint detail in the galaxies. I’m very pleased with the colour rendition by this telescope / camera combination in both this image and the previous Leo Triplet image.