Focuser for 150/1900 Saxon Mak

[nikolav]

Hey there.

After a few attempts to focus on Jupiter I began the meaning of the focus shift. I don't have any experience with other Maks or SCTs, but with mine Mak focusing with high magnification eyepiece if virtually impossible for me.

Enough with the intro, now I'm after some external focuser I can attach to the back of my scope. Crayford or helical. The thing is I have no idea what type of focuser I can physically attach there. The current eyepiece holder (1.25" or 2") is screwed on a thread, but I have no idea what type of thread is that. Is there any king of standard for this?

Here's the back of the scope:

The plan is to use the scope for visual as well as for some planetary imaging and my budget is probably in the vicinity of $100-$150 or so.

[George Gearless]

Hey Nikolav.

I know this doesn't answer your question completely, but I have a tip that you might want to try before purchasing some expensive equipment.

I have a Maksutov 180mm. And yes, it is quite difficult to focus. I started by using a clothes peg on the focuser. You can see what I mean in this video (Jump to 01:00 to see).

By using the same principle, I went a little further and made a little wooden stick that I can mount on the focuser instead. It is a little bit longer than a clothes peg and I can now focus my telescope perfectly. Also, I felt a bit silly with a bright pink clothes peg on my fine equipment. A painted black stick seemed to be more respectful to my telescope. But, as they say; if it looks stupid but it works, then it isn't stupid.

Edit: If you are asking because you eventualy want to make the focusing automated or remote controled, you will definately need to purchase some 'professional' equipment. But I don't know much about that. Luckily there are many on the forum who do.

Edited July 6, 2019 by George Gearless
Addendum regarding automation.

[Cosmic Geoff]

The focal length of your scope is close to that of my C8 SCTs (~2000mm).

I found that focusing the C8 for visual was not difficult, but when focusing for planetary imaging it bounces around a lot on the SE mount.  The imaging-class CPC800 mount is far more stable and focusing by hand is not a problem.  It was stable enough for me to see what this mirror shift thing meant - not a problem either.

The mount in your picture looks rather small.  If you are considering imaging, you might consider upgrading to a heavier mount, e.g. a HEQ5, for extra stability. The planetary processing software will compensate for a wobbly mount, but it is much less trying all round if you mount is stable.

No doubt somebody can advise you on adapters to fit a Crayford or helical focuser to the back of your scope. For my Newtonian I got a Chinese helical focuser (designed for guidescopes) for about £20 and it screwed into the bigger part of the 2"/1.25" adapter.

[nikolav]

I removed the light blue clothes peg just for the photo-session  The thing is that even with it the focus shift makes say Jupiter to get out of the view completely. From what I've read I see I can use the internal focusing system to focus it near enough the target and the external focus for precise focusing.

I know the mount is not the best possible, but still I'm gonna give it a try for planetary imaging and I'm in the process of making a DIY motor drive for it (OnStep). Time will tel, but I hope it'll be good just for that.

Cheers!