• Allen Mitchell

Lumicon Easy Guider for 2 Inch Focusers Review

The Lumicon Easy Guider is a two inch focuser compatible off-axis guider for your telescope.  Lumicon has been manufacturing OAG’s since the early 1980’s and have the longest experience in the off axis guiding market.  I trust that because they’ve be

en making guider solutions for a little longer than I’ve been alive, they know what they are doing.  So when they asked me to do a review of their Lumicon Easy Off-Axis guider I felt comfortable that I’d be working with a quality piece of eqiupment.

 I’ve owned off axis guiders by Orion and Meade before.  I sold the Orion to a friend who needed it - and I was having trouble making it work with my SCT anyway.  With its limited 120 degrees of motion, the Orion off axis guider had a heck of a time finding a guide star with the narrow field of view with my Celestron 1100 Edge.  My Meade off axis guider came with a telescope kit purchase I made a few years ago. I’ve never used it. Mostly because the Orion off axis guider was such a pain to use.  The Lumicon Easy Guider was promised by Lumicon to be “...One of the most powerful astrophotography accessories available today.”.

So, are they right?  We all know that the mount is the most important aspect of astrophotography - but can you really count a mount as an accessory?  I don’t think you can. There aren’t many ways to photograph the sky where having some tracking system is not necessary.   A mount is almost universally required for astrophotography. But the add-ons, like guiders, polar scopes, filters, flat panels - those aren’t actually necessary to take a photo, but one could argue they are necessary for taking quality photos.  And high on the list for taking a quality photo is precise tracking of the sky. Many people can’t afford a premium mount costing several thousands of dollars. These mounts typically have very well machined gears which reduce periodic error to the lowest possible values.  They’re build incredibly rigidly and pair with software such as TheSkyX and Astro-Physics Command Center which offer an entirely new way to image the sky unguided.

A guiding solution is an important purchase any astrophotographer needs to make if the mount they own doesn’t offer precision, multi-minute unguided tracking of a target.  Also, guiding solutions are comparatively affordable. In this hobby, everything seems to cost an arm and a leg (and sometimes a kidney). Finding ways to take long exposure photos while not breaking the bank is just as important as every other facet of the hobby.  

Is the claim hyped up?

An off-axis guider such as the Lumicon Easy Guider is one of the most powerful astrophotography accessories you can buy andI don’t think it’s being oversold by the “most powerful” claim.  

How about the easy part?  Being easy is so important to Lumicon, they chose that word as the first word for the product name “Easy Guider for 2 Inch Focusers”.  Is it easy? That’s a bit more complicated to answer. The reason why is inherent to all off axis guiders: exacting back space requirements for two cameras.  It can be tough enough to get it right for one camera - and it’s much harder to do it for two.

Is it easy to install?

Yes.  Though it could be made a little easier to install, I believe that it’s simple enough for everyone.  One improvement I wish the Lumicon had to facilitate an easier installation would be for the flange on top of the guider to be flat instead of diamond shaped.  The flaring out of the flange collides with my filter wheel, making the installation a little tricky. It is easy to use?

Yes.  I have no complaints on the use at all.  The guider does offer a method for finding a guide star a full 360 degrees around the telescopes field of view.  This is important because not all suitable guide stars are going to be in the same position relative to the imaging sensor.  Being able to rotate the Lumicon Easy Guider completely around the optical axis make finding a guide star less frustrating.

Is it easy to set up?

That depends.  If you’re savvy with basic algebra (a+b+c=d) and you already have all the correct spacers you will need then setup is a breeze.  However, it’s not possible to know what spacing you will require until after you open the instruction manual, look up your camera (may have to google for the information) back focus distance, you can’t do the required formulas.  Nor will you know if you need to purchase extra spacer / extension tubes. This is one of my problems with all Off Axis Guiders, and this one is no different. Here is the method for finding the correct optical spacing.

You need to know the following values first: Imaging camera and guide camera back focus distance (distance from the camera threads to the sensor). If you’re using a filter wheel, how thick it is. Any spacer / extension tube rings you may be using. For my setup, I’m using the following: ASI1600MM Cooled pro with 17.5mm BFD

ZWO EFW-9 with 20mm thickness ZWO ASI174MM with 10.5mm BFD

First:  Calculate a the value of “B” (imaging camera end) B = Camera BFD + 17.5 + Filter Wheel Thickness (include spacer and extension tube thicknesses here) B = 17.5mm + 17.5mm + 20mm

B = 55mm Second:  Calculate the value of “C” (guide camera end)

C = B - guide camera BFD

C = 55mm - 17.5mm

C = 37.5 mm If C is greater than 27mm, and less than 48mm the guide camera will come to focus. And here lies the problem.  If my guide camera sat inside the guider barrel like a typical guide camera would, it would have a 10.5mm tolerance for the spacing requirements above (greater than 27, less than 48).  My guider sits on top of the guide barrel.  The barrel adds roughly 38mm of extra space to the equation.  My new value for C is 75.5mm! This means that my guide sensor is way outside the 48mm maximum spacing allowed and still work.

What I’d like to see as a fix for these situations is a method for removing the barrel entirely, and threading a non-specific guide camera, such as the ASI174MM right to the guider, possibly with extension tubes / spacers to help meet the distance necessary to ensure that the distance between the two sensors and the pick off prism are equal.  This is what I tried to do (the distance between the two camera sensors must be equal.).  However, the best I could do was add  an additional 20mm with two addtional 10mm extension tubes

Is it easy to guide with? Not if you don’t have the correct spacing.  I tested this out as best as I could over the course of three nights, and I just couldn’t get The Sky X to lock onto a star and guide on it.  I found plenty of them - that’s not the issue. No. My telescope’s optical abberations distorts the stars into kidney bean shapes when picking them off at the outermost parts of the field of view.  Coupled with the incorrect spacing, and those kidney beans become very out of focus blobs that are not good for guiding.

The simplest solution to my problems would be to just get a proper guide camera to use.  For the purposes of a review, however, buying another piece of equipment to test something that should work doesn’t make much sense to me.  Don’t misread what I’m saying. I think this OAG is brilliant, and it really is easy to set up, use, and feels like a top notch, quality piece of metal.  No, what I’m saying is that sometimes, even the most powerful astrophotography accessory today sometimes cannot solve every situation if you don’t already have the complementing accessories for it.

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