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Moonlite Focuser Installation Questions


greglloyd
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I've a moonlite focuser plus installation kit arriving on Monday and have just been checking out a few things beforehand which are throwing up some questions :-

p.s. I'm fitting this to a skywatcher 300p (1500mm F/4.92). The existing focuser is the Skywatcher Dual Speed 10:1.

1. My secondary mirror central screw head has stripped, so at the moment I cannot move the mirror up and down the tube. But.. It is perfectly aligned under the existing focuser right now. Did anyone have to move their secondary mirror up or down the tube after changing your focuser? The tilt screws are fine, so I will be able to realign the tilt of the mirror just fine, if required. If I need to move the secondary mirror up or down the tube then I have a dilemma because I need some way of getting that stripped head screw out.

2. I've measured the existing focuser and it is 3.25" high from the the OTA at minimum rack height, and 4.75" at max rack height. However, for 1.25" eyepieces Skywatcher also supply a 2" to 1.25" adaptor which is approx 1.5" long. So this means that in effect, my 1.25" eyepieces are being fitted at a height of 4.75".

I plan to fit the Moonlite with all three spacers (1", 0.5", 0.25") + the focuser (1.5") to give a total height of 3.25" which is the same as the existing focuser. Does this mean I will need to use the 1.25" Skywatcher adaptor or could I get away with just fitting the eyepieces to the moonlite low profile 1.25" adaptor included with the focuser? I would prefer not to use the Skywatcher adaptor and take advantage of the compression rings on the Moonlite. Im not sure if the length of the Skywatcher adaptor is actually needed for back focus or if they simply provide it to allow the 1.25" eyepieces to be fitted?

3. If a 2" to 1.25" (1.5" long) adaptor is going to be required for back focus, what is the best option? I want a snug and well aligned fit.

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1.you might need to adjust your secondary but might as well not,all depends how accurate you are with your installation and how you align your focuser to secondary mirror.

2.With Moonlite installation kit you have the option to raise or lower position of the focuser.With original Skywatcher you will ALWAYS need to use the extension tube to reach focus,where with moonlite installation kit you can raise the focuser up so you dont need any.If the existing raiser plates are not sufficient,you can buy additional and install them and that what i would suggest to do.They are not expansive,just make sure they are for your size of the scope.

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I've a moonlite focuser plus installation kit arriving on Monday and have just been checking out a few things beforehand which are throwing up some questions :-

p.s. I'm fitting this to a skywatcher 300p (1500mm F/4.92). The existing focuser is the Skywatcher Dual Speed 10:1.

1. My secondary mirror central screw head has stripped, so at the moment I cannot move the mirror up and down the tube. But.. It is perfectly aligned under the existing focuser right now. Did anyone have to move their secondary mirror up or down the tube after changing your focuser? The tilt screws are fine, so I will be able to realign the tilt of the mirror just fine, if required. If I need to move the secondary mirror up or down the tube then I have a dilemma because I need some way of getting that stripped head screw out.

2. I've measured the existing focuser and it is 3.25" high from the the OTA at minimum rack height, and 4.75" at max rack height. However, for 1.25" eyepieces Skywatcher also supply a 2" to 1.25" adaptor which is approx 1.5" long. So this means that in effect, my 1.25" eyepieces are being fitted at a height of 4.75".

I plan to fit the Moonlite with all three spacers (1", 0.5", 0.25") + the focuser (1.5") to give a total height of 3.25" which is the same as the existing focuser. Does this mean I will need to use the 1.25" Skywatcher adaptor or could I get away with just fitting the eyepieces to the moonlite low profile 1.25" adaptor included with the focuser? I would prefer not to use the Skywatcher adaptor and take advantage of the compression rings on the Moonlite. Im not sure if the length of the Skywatcher adaptor is actually needed for back focus or if they simply provide it to allow the 1.25" eyepieces to be fitted?

3. If a 2" to 1.25" (1.5" long) adaptor is going to be required for back focus, what is the best option? I want a snug and well aligned fit.

The best option is to get that screw fixed as you cant collimate with out it.

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Ok, was out fiddling with the scope and I managed to undo the screw. It was stripping because I hadn't undone the tilt adjustment screws enough. So I can now adjust the secondary tube position. I will replace the screw but didn't have a ruler to hand. I know it's an M5 screw but not sure of it's exact length. It seems about 40mm. Anybody know the exact screw?

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The Moonlite is now installed :-)

The installation wasn't too bad at all. The existing holes in the OTA lined up well with the holes in the Moonlite install kit base and it only took about 15 minutes of careful attaching to get it on the scope.

I'm glad I sorted out the secondary screw as although the mirror was fairly well aligned, it did need a little tweaking just to get it perfectly square to the focuser - plus I did a full recollimation of the secondary just to get everything perfect. Collimation of the primary was a joy as the Moonlite has absolutely zero play!

The focuser is a piece of quality. There is absolutely no slop or play. Period. The focusing action is extremely smooth and precise. It's going to be a joy to use hopefully.

The new focuser is actually a little higher at min rack height than my last focuser which is a pleasant surprise. I'd say there is an extra 0.5 to 0.75" plus the draw tube on the Moonlite is 2" which is 0.5" longer than the Skywatcher. So all in all that buys me an additional 1" to 1.25" of back focus over the original without it's adaptor. I originally thought it would be the same height, so perhaps I will get enough back focus without having to go with an extension tube. That would be the ideal.

Of course, in this part of the world it doesn't even take a new scope to bring on the cloudy nights. Just the smallest of astro accessory will do it! So of course, despite it being nice and clear earlier before I started this evening's job - the clouds have duly rolled in to spoil the show.

Oh well, I guess the star testing is going to have to wait for another night  :grin:

Edited by greglloyd
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Had the scope out this evening despite the terrible windy conditions - just had to be done! I was too curious to see how the focuser performed and whether the eyepieces would reach focus.

The good news is that the Delos eyepieces all reached perfect focus - no extension tube required  :smiley:

As for the MaxVision 28mm (2"), it got to within a hair's breadth of reaching sharp focus when inserted by itself into the focuser. The focuser had to be racked fully out. So I decided to try the 50mm extension tube and found I had the opposite problem. I had to rack fully in - however the focus was almost perfect (perhaps it might even have been at best focus, as the seeing conditions are not good here this evening). I just didn't like that I could move the focuser just a tad more to see if the image would improve further or degrade. It's a tricky one because my astigmatism in my eyes comes into play with the large exit pupil on the 28mm.

This has me wondering if I could get a little bit of lee way with the focusing by either tightening or loosening the primary mirror adjustment screws at the back of the scope to just slightly move the primary mirror position either towards or away from the secondary?? Ideally I would like to get away without having to use the extension tube and get a little bit more back focus (just a few mm would be enough).

As for the focuser, I totally recommend this upgrade. I'm getting the sharpest views with this scope ever. The focus just snaps. Even with the poor seeing conditions forcing me to do a little refocusing. Everything is just locked tight and aligned so well. If you have a Skywatcher dob, this should be on your shopping list as a upgrade!

I will be out again this weekend giving it a further testing as the forecast have the winds dying down over the weekend.

Edited by greglloyd
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Yep. Focuser aligned perfectly and easy to fit. What I'm talking about is changing the point of focus height at the eyepieces. This is so I can get away without having to use an extension tube with the 28mm. The stock Skywatcher required an extension tube but the increased focus range of the Moonlite means I only need about an extra 1mm back focus to not need an extension tube.

I'm wondering if loosening the primary collimation screws out a little will move the primary mirror the 1mm or so down the OTA that I need?

Edited by greglloyd
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You could use a Baader 2" Click-Lock i have one on the Dob makes changing EP's in the dark so easy and safe....If the movement is tight when you collimate you could find it moves out of focal range....

http://www.firstlightoptics.com/adaptors/baader-2-inch-click-lock-cl-extension-47mm.html

Edited by Tinker1947
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Both are fitted. With the previous Skywatcher Dual speed I had to use a 50mm extension with the ES 28mm.

Also to note though, my scope is the BKP 300 DS (apparently primarily designed for astrophotography) rather than a 300p. So perhaps the secondary and focuser position on the OTA is ever so slightly different from the 300p to assist with in focus for astrophotograph. You can see the scope in my profile pic.

Edited by greglloyd
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  • 1 year later...
On ‎13‎/‎01‎/‎2015 at 14:44, greglloyd said:

The Moonlite is now installed :-)

The installation wasn't too bad at all. The existing holes in the OTA lined up well with the holes in the Moonlite install kit base and it only took about 15 minutes of careful attaching to get it on the scope.

I'm glad I sorted out the secondary screw as although the mirror was fairly well aligned, it did need a little tweaking just to get it perfectly square to the focuser - plus I did a full recollimation of the secondary just to get everything perfect. Collimation of the primary was a joy as the Moonlite has absolutely zero play!

The focuser is a piece of quality. There is absolutely no slop or play. Period. The focusing action is extremely smooth and precise. It's going to be a joy to use hopefully.

The new focuser is actually a little higher at min rack height than my last focuser which is a pleasant surprise. I'd say there is an extra 0.5 to 0.75" plus the draw tube on the Moonlite is 2" which is 0.5" longer than the Skywatcher. So all in all that buys me an additional 1" to 1.25" of back focus over the original without it's adaptor. I originally thought it would be the same height, so perhaps I will get enough back focus without having to go with an extension tube. That would be the ideal.

Of course, in this part of the world it doesn't even take a new scope to bring on the cloudy nights. Just the smallest of astro accessory will do it! So of course, despite it being nice and clear earlier before I started this evening's job - the clouds have duly rolled in to spoil the show.

Oh well, I guess the star testing is going to have to wait for another night  :grin:

I'm hoping you can answer my question on how the spacers should be placed with relative to the hole. Should all of the hole be visible or only part of it. I have attached two images for reference. Thank you in advance!

post-246043-0-84845800-1466570369.jpg

post-246043-0-68767900-1466570476.jpg

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