ScopeTeknix Multi-LED Reticule Reflex Finder (MRF)
One of the things about the standard Orion XT10 9x50 Finder Scope is that it provides quite good magnification of the area of the sky you are pointed at, but if anything the 9x magnification is such that it makes it harder to spot the actual object you are trying to pinpoint! That probably seems like a contradiction, when the idea is to be able to easily "find things".
The confusion arises because, with the extra magnification you are suddenly seeing far more stars than you can readily identify as being part of the main constellation when you are viewing with the naked eye.
In this situation I find that to use the 9x50 Finder Scope effectively you need to be familiar with the positions of the stars at that higher magnification, e.g. by having a printed star chart available for the part of the sky you wish to study, or by having a laptop with astronomy software to hand to show the relevant part of sky at 9x magnification. This is just something that comes with practice and knowledge of the sky.
But as a novice I found that I was becoming more reliant on the Intelliscope COL (Computer Object Locator) to point me at the right sky object rather than having to use the finder, but this of course requires correct alignment before a nights observation!
Trying to roughly align the scope by eye on the necessary 2 stars had me wondering whether I was pointing the 9x50 finder at the correct 2 stars in the first place! A bit of a quandry.
So there is a lot to be said for having a red-dot finder on the scope, such as the incredibly popular Telrad finders. After a bit of searching around I discovered that Scopes-n-Skies provide a very reasonably priced finder from ScopeTeknix, with some neat features:-
ScopeTeknix Multi LED Reticule Reflex Finder (MRF)
It is a CNC fabricated reflex finder with a standard quick release dovetail mount, supplied with a quick-release pedestal support to fit standard sized shoes (29.5mm dovetail width), and comes with 2 x CR2032 3v batteries, a soft rubber lens cap, hex tools and instructions. The finder retains its collimation even after repeated removal and refitting cycles.
There are four switch selectable reticules that the LED shines through, and these range from;
- a perfect half-a-degree circle with centre spot (ideal for deep-sky target finding using maps),
- a simple mini-dot for star hopping,
- a punctuated cross - useful for planet finding and feature ID-ing on the Moon, and finally,
- a combined circle and cross.
The chunky brightness control has seven different settings, from extremely dim to bright enough to see in daylight.
After alignment with the main OTA, this red-dot finder makes life very much easier for pinpointing objects in the sky, but of course the problem then was that I could use either the standard finder, or the MRF, but not both together.
Also swapping one for the other resulted in very slight alignment shifts, so it made sense to purchase a second dovetail mount so that both finders could be permanently mounted to the OTA.
Fitting the Second Dovetail Mount
The dovetail mount comes complete with 2 mounting bolts, and the nuts were already painted matt black to reduce light reflections on the interior of the OTA tube.
Before drilling any holes I offered up the complete red-dot finder plus dovetail, with the 9x50 finder also mounted in place, so that I could determine the best location for the finder in relation to the original finder, and the focuser. I considered the following:-
- Keeping it far enough away from the focuser and original finder that it would not get in the way of my face when viewing through either of them.
- Keeping it as high as possible so that I don't have to stoop down too much when sighting objects at high altitude.
- The MRF is quite light, so has little impact on balance, even when positioned right near the top of the scope.
I decided to position the mount very close to the top of the OTA tube, but far enough down so that when making the mounting holes I would not end up drilling through the inner lip of the scope end surround.
Before starting work I rotated the telescope as far downward as it would go and fitted a bungee cord to hold it in place while working.
I always adopt this method when working with the telescope because it would be disastrous for any tools to fall down the interior of the tube onto either the Secondary mirror, or god forbid, the Primary mirror at the bottom!
Doing this also keeps any swarf from the drilling process at the mouth of the tube, where it can be hoovered out before raising the scope again.
I put a piece of white insulating tape in place roughly where I wanted to drill through, then using a set-square and carefully measuring to make sure the dovetail would be absolutely square with the OTA, I used a marker pen to mark through the mounting holes exactly where I needed to drill.
Next I used a sharp-pointed centre-punch and hammer to dent the metal enough for the drill bit to start the holes without skipping/scratching across the surface of the OTA. I used a small drill bit first, then the correct size required for the bolts second. Finally I used a countersink tool to remove any swarf and sharp edge from the drilled holes.
All that remained was to insert the bolts and tighten the nuts onto the threads. This required the nuts to be done up quite tightly to prevent movement of the dovetail mount on the shiny finished surface of the metal.
The two nuts on the inside of the tube were finished in matt black, but even so a touch of paint will finish off the ends of the bolts.
The pedastal support and shoe fits into place on the dovetail mount, and is done up using the knurled thumbscrew.
And here is the red-dot finder mounted on the shoe ready for collimating with the main OTA. This is done using the provided hex Allen keys to adjust up/down and left/right movement, while sighting a distant object such as a telegraph pole or chimney pot through the 10mm eyepiece at 120x magnification.
After collimation, both finder scopes now point accurately at the same target. So now when finding objects to view, I first align using the red-dot finder and then can view through the 9x50 finder, which gives some magnification and a nice view of that section of sky, and finally I can insert the desired eyepiece and view at high magnification.
In this photo I have pointed the telescope toward the dark interior of our garage so as to show the view up the scope, through the finder and one of the LED patterns you can select (click the photo to enlarge it).