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An Update
Ok did another test this weekend. I attached the 40D to the OTA and tried to focus it on the trees in the nearby paddock (distance of 400m or so). With the Tak extension in and with the focusor only 20mm extended out and with the complimentary extension in place between the focusor and the OTA I acheived focus. I noted the following in my viewing through the view finder:
- There is some flop in the focusor. I applied a small amount of pressure on the underside of the camera and this managed to change the field of view. Not by a lot but enough to convince me that this focusor will have to be changed in the end. I will have to do several images to determine whether the focusor is flexing too much during an imaging run. Perhaps a better focusor will be the better option.
- I had to use a Takahashi extension to obtain focus. This means that from the rear of the OTA there is something like nearly 10"s ( guess really but looking tonight at the tape measure it seemed the correct length) to the focus point. I would expect that it would be better to have the screwed in extensions in place rather than using an extension from the focusor out.
- With the Takahashi extension I kept the flattener in place. It appears that this flattener might well be ok for imaging. The image looked nice and flat, but proof will be in imaging star fields. I also noted that there appeared to be vignetting to the corners in the view finder. I suspect the light cone is not wide enough to illuminate the whole of the chip. Again imaging will no doubt tell us the truth.
So with that I will hopefully next week obtain my first images through the OTA. I will most likely image Eta Carina. Being a region with lots of stars and nebulosity I see this as the idea test subject
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