Moonlite Focuser question and Hitecastro mount hub pro

[redbeard (Damien)]

Hi IIS folk,

I'm thinking of purchasing a Moonlite focuser for my 10" Meade LX200 GPS and I have a couple of questions if any one can help.

In relation to how the focuser attaches to the scope, I was wondering if it is best to get the 3 1/4" large thread fitting because I have read that this lets more light through as opposed to getting the SCT 2" type which fits on the standard Meade adapter which has an internal diameter of 1.5".
I have a Canon 450D camera which I will be using for imaging. I have also read that the draw tube should be .95" travel as I plan on using a focal reducer most of the time and this can be fitted inside the focuser.

So my first question is, is this a good idea for this scope and camera setup? (One of the reasons for this question is there is an ad on IIS for a Moonlite focuser that has a 2" SCT connection and it's cheaper than a new one, but is there a noticable difference between 2" and the 3 1/4" connection for imaging). I also wonder if the focal reducer itself has a smaller internal diameter that would affect anything and does brand matter. I currently have a Hirsch 6.3.

My second question is the Mount hub pro looks like a cool piece of kit and should control the Moonlite focuser as well as lots of other cool features. Is this really any good and is that a good combination with the Moonlite focuser? I like the idea of 2 cables to the ground instead of heaps as I have the QHY5, Canon 450D, dew heater and standard micro focuser have quite a few cables to manage.


Any help/advice appreciated.

Cheers,

Damien.

[Astro_Bot]

Hi Damien,

I can only help you with one of your questions.

I recently acquired a Moonlite (manual version, tri-knob) for visual use with a Meade LX200-ACF 10". During my deliberations, I obtained the illumination and vignetting analysis for Celestron SCTs from the Yahoo SCT users group and interpolated for a Meade 10" SCT (though I doubt that made any difference as the conclusions were clear enough).

As measured by me, the LX200 10" baffle ID is ~51mm while the SCT adapter opening is ~40mm (a tad bigger than Celestron's 38mm). For visual with a wide-field 2" eyepiece, the penalty of adding a Moonlite with 3 1/4" flange is moving the focus point back about 100mm compared to an SCT diagonal, which induces vignetting of (IIRC) ~4% and a slightly smaller TFOV due to longer FL. However, decreasing the baffle opening from 51mm to 40mm induces vignetting of around 35-40% (my interpolation), with the effect being most noticeable at the edges. The effect of additional backfocus of that order is negligible compared to the smaller baffle opening.

For imaging, the additional backfocus should only have a relatively small effect, but I'm no expert in that area. The effect of the additional ~30mm for the tall FR style flange should also be virtually negligible, IMHO.

Be careful with focal reducers. Does the GPS have ACF optics or standard SCT optics? My research in that area is far from complete, but for ACF optics, only two look promising - the Optec Lepus 0.62 Telecompressor and AstroPhysics CCDT67 - the Meade and Celestron 0.63 FRs don't work with the ACF optics but will be fine with standard SCT optics.

I've been impressed with the build quality and performance of the Moonlite. Although the mirror flop in my LX200 isn't too bad (compared to others' reports online) nevertheless, achieving good focus using only the "coarse" focus knob was virtually impossible, whereas it's easy and repeatable with the Moonlite even with heavy diagonal and eyepieces. The Moonlite's fine focus knob works smoothly enough (and with a light finger touch) that I see no particular advantage for visual work of an electric focuser. Imaging may be different, however.

[redbeard (Damien)]

Thanks for the reply RG,

I'm a bit dumb at all this but may I ask a comparison question.

First of all I'm using the non ACF version of the GPS scope.

In my current setup, I'm using the standard Meade adapter with a Hirsch 6.3 focal reducer screwed on to the adapter, I then have the Meade standard zero shift focuser connected to the Hirsch focal reducer via the 3 thumb screws. I then have my Canon 450D with T-ring and nosepiece, (about 1 inch in length), connected to the focuser. My question is, with the Moonlight focuser, will I still be able to connect the Camera to the back of the focuser as I have been doing or will I have to add the draw tube as well making the camera sit a lot further away using the 3 1/4" flange. (With the focal reducer in the focuser).

I currently get vignetting when I take shots, so will I be worse off with the 3 1/4" flange or worse off with the 2" to meade adapter. Also is the amount of light that gets through even applicable as to whether I use 3 1/4" or 2"?

Either way, I have a horrible wobbly setup as is and I like the way the Moonlite has a solid thread to attach to the scope without the thumb screws. I also have an eye opener if that makes any difference that I use when I'm not using the focal reducer and the focuser then attaches to that via thumbscrews.
Sorry if I'm confusing things here, but I'm a quick learner sometimes.

Cheers,

Damien

[Visionoz (Bill)]

I believe the 3 1/4" fitting would be suitable for larger Meades or a C11 (which I owned one before and had that size for the visual back flange fitting) and had the MoonLite focuser with the FR6.3 to suit - not sure if your SCT has that 3 1/4" threaded flange or the regular 2" one - so unless your OTA is one which has the 3 1/4" threaded flange then your choice is rather limited

HTH
Cheers
Bill

[redbeard (Damien)]

Thanks Bill,

Yes the 10" LX200 GPS has the 3 1/4" thread and it comes with the Adapter that screws onto the back.

Cheers,

Damien.

[Astro_Bot]

Originally Posted by redbeard

In my current setup, I'm using the standard Meade adapter with a Hirsch 6.3 focal reducer screwed on to the adapter, I then have the Meade standard zero shift focuser connected to the Hirsch focal reducer via the 3 thumb screws. I then have my Canon 450D with T-ring and nosepiece, (about 1 inch in length), connected to the focuser. My question is, with the Moonlight focuser, will I still be able to connect the Camera to the back of the focuser as I have been doing or will I have to add the draw tube as well making the camera sit a lot further away using the 3 1/4" flange. (With the focal reducer in the focuser).

The drawtube is an integral part of the focuser, with standard 2" brass compression ring fitting - see the Moonlite website for detailed photos and descriptions. Assuming your T-adapter nosepiece is 2", it'll slot perfectly into the focuser's drawtube. I've found the drawtube in my setup to be very solid.

You might mean an extension piece to get proper backfocus distance. Since the Meade mirror moves as well as the focuser, I don't see how you'll need an extension piece as well without a FR, but I'm no expert with imaging with one of these things, and with a FR, you need the correct distance between FR and sensor ... but I think that's pretty much catered for in the focuser design, though it will pay to check.

I currently get vignetting when I take shots, so will I be worse off with the 3 1/4" flange or worse off with the 2" to meade adapter. Also is the amount of light that gets through even applicable as to whether I use 3 1/4" or 2"?

I can't see how you'll be worse off with the 3 1/4" compared to 40mm ID of the Meade SCT adapter. As for illumination, I can only comment on visual use - IMHO, it makes a noticeable difference. What is the internal diameter of the Hirsch FR? Will that be the limiting factor given its position in the imaging train? I don't know.

Either way, I have a horrible wobbly setup as is and I like the way the Moonlite has a solid thread to attach to the scope without the thumb screws.

The Moonlite is rock solid even with >1kg of payload in the drawtube.

I also have an eye opener if that makes any difference that I use when I'm not using the focal reducer and the focuser then attaches to that via thumbscrews.

I don't have either, so can't really offer any advice. I thought the zero image shift focuser screwed onto the adapter though?

[redbeard (Damien)]

Thanks again RG,

Sounds like the 3 1/4" flange is the best way to go.

Cheers,

Damien.

[dcalleja]

I recently replaced the stock microfocuser on my 8inch LX200R with a moonlite with stepper motor. It's the standard flange though. It's simply brilliant (but heavy)

I also got a MH Pro. One of the best add ons ever. The moonlight works really well with it. Just two cables running off the scope now. Much neater and faster to setup. Mounted it on the eyepiece rack on the wedge. I also got shorter USB cables to minimise drag and clutter from Lindy.com.au. I think I put some pics on my site about it

Dan

[redbeard (Damien)]

That's awesome Dan, I can't wait now to get the devices and set them up. Do you think it would be good to mount the mhp on the tube itself so there is even less cable movement or is the mhp too heavy or large or perhaps even the fork arm?

Great to hear from you who has already done this.

Cheers,

Damien

[dcalleja]

I think its a bit big for the tube (certainly for the 8inch). You could do the fork arm. I used 4 velcro double sided pieces of tape and eventuallt settled on the utility tray on the wedge.

[redbeard (Damien)]

Cheers again Dan,

I'll get all the bits and start experimenting with the best spot.

I like your website, I've had a quick look but will go back there soon to check it all out.

Cheers,

Damien.