Trutek motorised filter wheel

[MartinB]

When I started imaging I thought any sort of filter wheel was a bit ott but after faffing around screwing and unscrewing filters and getting condensation on everything I saw the light and bought a Scopeteknix manual filter wheel. This certainly made life a bit easier but the experience was often marred by getting a muddle over which filter was where. This led to the ruin of more that one imaging session.

When I started guiding I discovered an additional problem - it would often take about 30 seconds or so for the guiding to get back on track after turning the filter wheel. Still these problems didn't seem to justify forking out around £500 on a motorised wheel :shock:

Trutek (ie Nick Hudson) is the UK dealer for Takahashi as well as making filter wheels. When I bought my EM200 mount I was able to secure a reasonable discount on the wheel. I thought I would give you a report on how this little piece of decadence has performed.

The wheel is quite a chunky bit of kit, a good bit heavier than the Scopeteknix with a thicker profile. I always use it with a 2" nose piece but also have an adaptor to allow me to screw it directly into an SCT thread. My H9 screws directly into the other side of the wheel

It comes in a neat pelican case complete with all leads amd software driver cd

It comes with a number of disc options - I went for a 9X 1.25"filter holder. This means the wheel houses my full LRGB, CLS and narrow band filter sets! The wheel is fully enclosed so I no longer have to move my filters around - wonderful!

The wheel needs it's own power supply - the lead provided is a little on the short side but not a problem with careful cable routing. It also needs a serial computer connection - I use a USB to serial adaptor.

The wheel was immediately found by Maxim. It was a very easy and intuitive job telling maxim which filter was where. Maxim then remembers these positions from session to session. There is a home position which the disc is always moved to on connecting so provided the filters aren't actually removed no manual alignment is necessary.

I now set up my imaging sequence in advance in Maxim. Anyone familiar with Maxim will know you can specify type of sub (light, flat dark, bias), suffix, exposure time, binning mode, number of exposures and filter. You can set the details for each filter you need to use during the session. The last time I was out I specified 10x20mins Ha, 20x55 secs R 20x50 secs G and 20x60secs B with the RGB all binned 2x2

Once you start the sequence Maxim will run through the filters in sequence. For the above sequence it will first take an HA then an R G and B. It will run another RG and B then return to Ha - it works out the sequence so that a balanced set of subs are obtained rather than do all the Ha then the red then the green then the blue. This means that if you session is interupted by cloud you still have a balanced LRGB image.

Filter change typically takes around 1-2 seconds and has no effect on the tracking. I have a guider setting delay of 5 seconds to allow the guider to settle down after image download so the filter wheel actually doesn't slow things down at all.

It just works and it has transformed my imaging way beyond the bare description above would suggest. So what I thought was likely to be my most stupidly extravagant astro purchases has turned out to be one of my best ever.

Not much to look at but here it is a picture

(click to enlarge)

[jcm]

Been thinking about one of these , but the cost has put me off

I think AstroArt can also control these motorised wheels.

John

[MartinB]

You won't regret it John!

[jcm]

You won't regret it John!

em... I will let you know

Did you have any problems with the setting up ?

John

[Beyond_Vision]

Just wondered how changing the filter wheel interferes with the guiding. Does that mean you are guiding with the same camera that is imaging ? From your picture it looked like you were guiding with a another scope

Regards

Kevin

[SteveL]

I thik Martin means that any vibrations caused by the filter wheel moving round manage to settle down before the next sub starts

[MartinB]

It's impossible to change the filters using a manual filter wheel without moving the scope a tiny amount (if you shake the imaging scope the guide scope gets shaken to). This causes havoc with the guiding and it takes about 30 seconds for everything to get on track.

When a sub exposure is completed it is downloaded to the hard drive. During this time the guiding stops. With the SXV H9 being USB this is very short but Maxim still allows 5 seconds for the guiding to catch up with itself. This is more than enough time for a motorised filter wheel to change filters. There is no movement of the scope with the motorised wheel. So, no time is lost despite the change of filter with every sub.

Did you have any problems with the setting up ?

John

An absolute doddle to set up in Maxim John and I'm sure Astroart would be just the same.