I got focus doing what doug said and it's close to where it normally is with out the MPCC, it's just I don't have the required adapter at that length. If I got a 2 inch adapter the same as my 1 1/4 I wouldn't have a problem.
I was thinking of having two focusors at one stage - my new 2" low profile custom made heavy duty crayford and 90degrees around the tube a 2" ultralow profile helical focusor (stands 1" high fully racked in ! that I happen to have in draw and has never been used) to do prime focus stuff , rating the secondary as required.
Wonder if something like that might be a solution for you ?
well It turns out that the focuser's are unique on the skywatcher reflectors, which is why they are a little bigger, only problem is that there is no smaller 2 inch adapter, I got another one and will have to either cut it in half or go to a machine shop and get them to do it, or I saw the JMI motor focuser there and it's price tag which would be more than the scope.
Ashley, I had this same thought today... looking at my 2" adapter, I thought... I might just take that to work, cut it down so its 1cm tall and get the fitter at work to tap threads in it for the screws... should come up trumps.
yep, thats exactly what needs to be done, I don't have any tools that can do anything along those line but I was given a free 2 inch adapter to get cut down so that good, one for the camera and one for the eyepiece.
The reason the focus tube is larger is to cut down on vignetting which is good but not when you need to attach certain things. Though that JMI is very nice, Costs more than the scope though.
Before you attack the adaptor, ask a friendly machinist. The older the machinist the better I find, as they are normally more inclined to assist.
What I think you want is something that will either fit tightly into the focuser tube, or screw into the focuser tube. On the end of that you need a thread, M42x0.75 I believe, the standard T thread. So you can then simply screw your T ring to this, and have it virtually touching the top of the focuser.
Make sense?
Gary
if you are atleast half serious about taking some images it would be best to replace the focuser completely with something like a gso 10:1 low profile,
they are cheap enough and will save you a lot of bother in the long run.
there are a number of things that can go wrong when imaging but focus is the one thing that you can always nail.
i dont know how easy it would be to fit it to the skywatcher but i guess you would just have to drill 4 new holes, if your still not sure or dont want to do it yourself you could take it to the machinist you were going to take the adapter to (with both mirrors removed from the ota) and say 'i need this to fit here' im sure it wouldnt cost much if you were to get them to roll a bit of scrap flat that would bolt to the focuser and the tube and it would be far superior to the standard focuser.
on top of that i always thought it was a waste of time trying to collimate anything to any degree of precision when the focuser tube slops around enough to ruin it anyway.
I wouldn't recommend the GSO 10:1 low profile focuser. From what I have seen they have issues with tube sagging under weight.
I think the standard GSO 10:1 would be a great focuser. And from what I read in this thread, it would probably come to focus. By that I mean you would be able to sit the MPCC into the GSO focuser and this setup would be similar in height to your existing focuser.
Might be easier and better than trying to machine a new part. If you imaging, your going to want 10:1 focus eventually.
The only problem I have with the focuser is that it's harder to fine tune, other than that it's fine, If I where to update the focuser I would go for the non motorized JMI, after having a play with it at the shop I can understand why it's at it's price, plus the MPCC will fit into it no problems.
I did just make myself a slow control for the stock focuser, a thin screwdriver on the screw in the middle of the focus knob ( just be sure not to undo it), not as good but I can turn the focuser a lot slower with it than the knobs.
i wasnt trying to imply that the gso 10:1 was a high quality focuser just that it would more than likely be easier to drill 4 holes and bolt it on and have it come to focus rather than getting bits machined to fit a standard skywatcher focuser only to upgrade it to a 10:1 later on anyway.
the low profile version may not be perfect or buttery smooth but you have to expect that for $100, the low profile wouldnt come to focus on my newt so i ended up swapping the 10:1 part over to my standard gso focuser, the result when i added motofocus was impressive giving me VERY fine focus control. plus when it comes to imaging id rather be exposing than tweaking focus by hand then waiting for the vibration to settle before inspecting again, now instead of guessing focus by eye i can watch the FWHM on the laptop screen and within 1 minute i know my focus is as good as its going to get.
you could argue that for the price of the gso 10:1 + motofocus you could get a JMI but i can guaruntee that it would be a lot harder to focus with the non motorised JMI even if it is of a better quality than the gso.
i should also mention that if you are into planetary observing, a setup like i mentioned can make a massive difference in the detail visible, only after seeing this did i realise how much of a difference it really did make.
well, it's a bit too late now, I got the new adapter back from the machine shop, as soon as I got home last night I had the dob out and focused on Jupiter, And I could!!
I gave it another go this morning on the moon, not the best time to image it but hey, it shows I can focus finally and I have a little bit of travel left too.
thanks to everyone for going through all this.
here's a pic of the new adapter with the old and the moon test shot (there a bit of JPEG compression).
I think it was about 40 bucks, A little more than I was hoping but If you look around you could find somewhere cheaper, these guys where down the road from where I work so I just picked it up on the way through, more convenience than anything and I needed it done.
