In early 2004 I purchased a new ST7-ME by SBIG. I quickly realised the troubles of CCD astrophotography as compared to relatively simplistic film based astrophotography. A CCD camera with parallel download (USB 2.0 may be different) can be extremely hard to focus (even when using sub-framing to reduce download times). Consider that the 12″ LX200 at F/6.3 has a focal length of about 1920mm (3048mm at F/10). This is a very long focal length to focus a small chip like that of the ST7-ME at!
Because of the focussing problems with the CCD camera I knew I had to purchase a crayford style focusser for the SCT and/or a motorised focusser before I would achieve any reasonable rate of astrophotography with the ST7. With manual focussing using the standard meade focusser (classic LX200) I could occasionally get a good focus but this took a lot of time and only occasionally worked.
First I purchased the JMI NGFC. While I always had the intention of upgrading it with a motorised focusser I didn’t really have the cash for the NGFC let alone the Robo-Focus! This is why I was hoping the NGFC might solve the problem without the need to purchase a motorised focusser. The JMI NGFC definitely helped the situation. I could now focus in and out without image shift and backlash concerns and this alone dramatically reduced focussing problems. The NGFC is an excellent focusser with great precision and backlash-free operation. I have no problems with the basic unit other than I quickly found didn’t want to have to shake the telescope every time I focussed. Every time I touched the telescope to re-focus I would have to wait a good 5 or more seconds for vibrations to dampen down. Also the manual focusser was the only thing stopping me from operating the telescope completely remotely from comfort & warmth of the house.
Then enter the choice of motorised focuses. I was tempted to buy the JMI motor for the NGFC. I am usually happy to work with what I have and I knew no matter what the complains about the JMI motor vs. RoboFocus I would live with it and get good results (their performance really doesn’t seem to be that different). But considering all the hassles I’d had with focussing (since I purchased the camera in April I had barely any reasonable images to show for at October!) I hesitated and considered the Robo-Focus option a more “sure” and accurate choice. Also more people recommended the Robo-Focus for accurate motorised focussing.
The choice between RoboFocus (by home dome) and MotoFocus by JMI I still occasionally wonder about. Personally, if I did it all again I would probably stay with the same RoboFocus because it has been such an accurate, compatible and reliable solution. However I wouldn’t have said that in the frist few months, when I would have considered the JMI solution better – Why? Well at the time I was choosing the JMI NGFC including motor and control unit was about AU$590. The NGFC on it’s own, with the RoboFocus then purchased separately and fitted totaled easily AU$1000. Is the huge cost difference worth it? It’s easy to say it is now because I’ve long forogtten the cost. I have never seen in person or tried the JMI motorised version of the NGFC. Also I was comparing the NGF-S with MotoFocus.
Another thing to mention here is that when I ordered the RoboFocus I didn’t realise it had never yet been fitted to the then new JMI NGFC (the NGFC was extremely new at the time). While I don’t doubt it was a tricky and time consuming process for Jerry (at Home Dome) to fit the RoboFocus to the NGFC this meant a substantial 3 month delay on the delivery. I was the unlucky first it seems! He kept me up to date during those 3 months and in the long run I’ve been very happy with the service provided.
Once the Robo-Focus unit arrived I soon fitted it and had the unit operational. I have absolutely no complains about the final result. The unit (RoboFocus together with NGFC) seems flawless and operates perfectly for me every time, with precise focussing.
Software Control
Regarding the use of the RoboFocus from software: Manual operation through it’s custom software is easy and includes preset buttons, ability to go exactly to a position, temperature comphensation (focus changes with temperature, it can automatically adjust for that) and lots more. Operation through CCDSoft is OK but I find not as user friendly as through the RoboFocus softare. The auto focussing using CCDSoft’s @focus has worked for me but again I have not found it particularly user friendly and is often inaccurate. In contrast, auto focussing using FocusMax (google for it) is extremely precise, extremely easy and achieves best focus almost every single time. I can’t recommend FocusMax highly enough, the combination of that and RoboFocus means I rarely adjust the focus through the RoboFocus software.
It is a shame that the Robo-Focus unit needs an old style “com” communication port. With the introduction of that and a weather station in my observatory I had to buy an extra 2 com ports (adapter card) and now have 4 com ports in use (LX200, RoboFocus, weather station and UPS). This could be a problem if you run your setup from a laptop that only has one or none COM ports. I am unsure if the RoboFocus works through a COM to USB converter.
Conclusions
So, recommendations for someone getting in to CCD astro photography and/or contemplating a crayford style focusser for their SCT and/or a motorised focusser? Well the solution I have (above) works 100% great. The JMI NGFC motorised version with MotoFocus would be a cheaper solution and I suspect work as well as what I currently have (but suspicion not confirmed). The Robo-Focus fitted direct to the SCT focusser is another option which I did not choose because I also wanted nice easy manual focus (by way of the NGFC) for occasions when I do visual observing and choose to do things “the good old way”. The disadvantage of this is that when I change equipment (CCD Camera to Film, Focal reducer or not, etc) I also have to change the focus of the LX200 manually before then using the RoboFocus unit for fine focussing.