A little Moonlite-ing.....but which order?

[Tim]

I have just bought via ebay in a roundabout way, a moonlite focusser for my C9.25 SCT. I am lead to believe they are quite good?

At any rate, I struggle with the inbuilt focusser, especially with freezing fingers in the winter, and consequently I have been over-using my WO72 just because I get on better with the Crayford style focussing. And so I am hoping this Moonlite jobby will help me get more from the SCT.

But I have a few questions;

1) What to do with the inbuilt focusser, does it need setting to one extremity or the other, or a middle position? Is there a way to prevent the mirror shifting etc?

2) What order for the filters? I have a skylight filter which usually lives on the back of the SCT, then other things are the focal reducer etc. Do I mount these before the Moonlite?

3) Any tips for getting the most out of the focusser? I will be trying DSLR focus if I can get it to work with Vista.

4) What would be a good price for the 2nd hand Moonlite? It's too late now of course, but just out of interest?

Thanks

TJ

[Kai]

#1 You use the std focusser to get focus and then use the moonlite to achieve fine focus.

[bazza]

TJ, you don't say if your Moonlite has the PC control or not.

If it has - you're gonna love it.

If it hasn't, well no worries - you can get it installed at a later date.

Use it by setting the moonlite to a mid point, then focus the object using the course focus of the SCT, then fine focus with the moonlite.

Using a program such as Focus Max connected to a PC, makes focusing a doddle...just watch the PC do all the work!

There is a type of Moonlite focuser that you screw the Focal Reducer into - made specifically for SCT's - is this the one you have?

Barry.

[Tim]

Thanks Barry. I dont know the exact model, but the thread on it will screw right on to the back of my C9.25.

I am assuming that the things like skylight filter and reducer go on first, and then the focusser. (It isn't a PC operated one btw)

TJ

[bazza]

TJ,

It would be best if you could screw the focuser direct onto the C9.25 as it's designed to do.

I mentioned the focal reducer type, link here:

http://www.focuser.com/cgi-bin/dman.cgi?page=productdetail&plugin=dstore.cgi&product=CS

(The dark red one is the focal reducer type).

If you haven't got one of these, (I'm not familiar with the others), I would still suggest the focuser goes direct onto the C9.25.

Maybe someone else is familiar with the other varieties?

Barry.

[Tim]

Hmmmm, now I'm really confused!

I can see that it would be better for the FR to travel with the tube, and I THINK I have the model in the link there.

I'm gonna try loosening the two allen grub screws and see if they remove the thread bit, and then should be able to get the FR in.

I think........

Cheers

TJ

[bazza]

TJ,

On mine, there is a grub screw that secures the threaded portion after you have screwed the whole focuser onto the tube.

Then, behind that, are three more grub screws (& a large sticking out knurled screw), which, if you loosen slightly, allow you to rotate the focuser, to enable you to change camera angle.

To screw the reducer onto the drawtube thread, you will have to unscrew the focuser from the OTA tube, screw in the reducer, then refit the focuser.

This is really difficult to describe, but you can see all these in the link to the Moonlite site.

Hope this helps.

Barry.

[Tim]

Thanks for your help Barry, think I have it sussed now. On this model for the C9.25, the FR doesn't fit in, thats just for the 10" and bigger jobs.

I am testing it out right now. It's possible that there is a little distortion in the stars, but I will need to do a comparitive test to find that out for sure. It was certainly easier to find fine focus with it though.

Are the electric bits an option to add at a later date? Or are they model specific too?

Thanks

TJ

[bazza]

TJ,

I think you can add the stepper motor and PC stuff to any of the models - the drawback is that it has to go back to Moonlite to have it done. You can't do it yourself.

Barry.

[RobH]

Stepper motor and PC control is well worth having TJ.

With Robofocus, you can get a much better focus than any other method and also use temperature compensation.

To do this, you simply focus at different temperatures (at least 3) and save these into a file. This allows the software to work out a temperature curve for your particular scope. FR, camera combination and then applies it as the temperature changes.

No more going inside for a couple of hours only to come out and find that you've lost a whole bunch of subs because the temperature shifted and you lost focus!

Cheers

Rob

[Tim]

Hmm, thanks Rob, I wasn't even aware that temp changes would affect the focus. Is that because of contraction? If so, what is expanding contracting?

Geez, the things you have to learn for this malarkey!!

TJ

[MartinB]

The Moonlight stepper motor focuser is every bit as good as the Robofocuser and has temperature compensation. As Bazza says, the focuser does have to go back to Moonlight to be fitted. You can do this through Ian King. I don't know how the cost would compare with fitting a Robofocuser to the Moonlight.

[MartinB]

Here's my moonlight which has the adaptor which can house a focal reducer. It is the 4" adaptor.

(click to enlarge)

[Tim]

Crikey! And here they are worried about the LHC being too powerful!!! That's some serious kit there Martin!

So my fr WONT fit into the focusser, will I have problem with that? If so, how will they manifest themselves?

Thanks

TJ

[GazOC]

:shock: Jeez Martin!!!