The back on my Mak? SCT adapters and such

[xnomad]

Does anyone here also have a Skywatcher Black Diamond Maksutov Cassegrain or do you know an answer to these questions?

I have the 127mm version and I'm looking to get a Crayford style focuser for this OTA but I'm not sure if the back on the BD Mak is standard. It certainly looks very different to the standard SW Maks and other Maks (from what I can tell searching Google Images) The back on the BD Mak is kitted out for 2" accessories and I've measured the back and it appears to be around 6.6cm or so wide.

My next question regarding this is if I do get an SCT Crayford Focuser that fits my Mak will I be able to attach an SCT diagonal to the focuser or will I have to use a standard diagonal?

[xnomad]

No answers?

Does anyone at least know the dimensions of the standard SCT thread to give me an idea what I need to find? Or if there is another type of Crayford I could get for this?

[marki]

G'day

I don't have the same scope as you but do have a etx125. The thread on the back of you scope looks like it is a similar size. What I did was buy an adaptor from scopetronics in the US which screwed onto the original thread whilst having the standard SCT thread on the outside. This allows me to attach SCT accessories as well as a 2" visual back. Problem you have is the diameter of the baffle tube which is not quite big enough to fully utilise 2" diagonals etc.

Mark

[xnomad]

Thanks Mark,

Do you know roughly how large the thread is on yours? In terms of the baffle tube 2" accessories are fine. The scope comes from the factory with a 2" diagonal and a 2" eyepiece. I'd just love to get a fine focuser as the image shift is annoying at 254x magnification.

[marki]

If yours came with a 2" diagonal and focuser then it has probably already got the standard SCT thread. The ETX has its own flip mirror system and a photo port at the rear of the tube. The port has the standard T thread (M42 - 0.75 or metric 42mm with a 0.75 mm pitch). From memory the meade SCT thread is imperial and a little less then 2" (~ 1.997") with 24 TPI (threads per inch). Celestrons are similar I believe. Now the large visual back on the meade lx200 series is 3.5 inch with a 16TPI. Realisically you will need to find a crayford manfacturer who also makes visual backs suitable for your scope. I know Moonlite will do a custom job for you if necessary but it will cost plenty and I don't think it would be worth it on a 127mm scope. All the crayfords I have came with a adapter ring to allow mounting of the focuser (usually 3 bolts into a milled groove). Hope this helps but I fear it may confuse you even more.

Mark

[xnomad]

Hi Mark,
Thanks for your reply.

I think I found another solution. I'm going to get one of these:
http://www.scopestuff.com/ss_taep.htm
But I'll buy one from an Aussie shop instead (I've found 2 suppliers so far) They are going for around $50

My back has a 2 inch eyepiece barrel screwed on to it. So I'll just slot the adpater in it and it and will then have a male 2" SCT thread on the end. I'll then just attach the SCT Crayford to that.

I'm not sure if it's a bad thing if the focuser is a bit further back from the actual back of the baffle tube. It's not going to be any further away than the diagonal would be (without focuser) so I guess it should work. I have a bit of doubt about this solution because if it works well why don't all manufacturers sell MCT focusers with just a male 2" barrel that slots into an eyepiece holder.....?

If that doesn't work for me, in the long run, I'll get a custom ring made that adapts my 66mm thread to the 2" male sct thread.

[marki]

Good Luck