Celestron EdgeHD 1400

c14 The C14 EdgeHD was bought in August 2010 after a 2 Months wait. After my experience with the C11 I was not originally planning on getting another Celestron OTA, but Franck Valbousquet at Optique&Vision here in France convinced me of otherwise. What convinced me is that Optique & Vision controls every single OTA by measuring the accuracy of the optics. They will only deliver tubes which are up to standards. That, added to the C14 price to size ratio, made the C14 extremelly attractive. I must say that I have not been disappointed, as the drawbacks common to the older Celestron tubes have been adressed with the EdgeHD version. Mirror flop and shifting are virtually nonexistent because of very accurate mechanical plays. Furthermore, there are 2 plungers which can be screwed in to lock the primary mirror in place (one has then to use a Crayford focuser). The optics are pretty good for an SCT telescope and meet Raleigh criteria (see report below). Perfect collimation is touchy to achieve as collimation screws have phillips heads and you must loosen 2 screws before tightening one. At the moment I have not be able to collimate on a in_focus star since turbulence has been too high. Also, the few nights I could have done it, I preferred observing as it does not seem so bad anyway (perfectly centered donuts). It has delivered some truly stunning views of Jupiter through the eye-piece, so I just could not be bothered… I like the old rule of “your scope will almost always be better than your air” as far as turbulence is concerned so I do not want to start developping a compulsive behaviour disorder over collimation!      c14-hd-961696-50

Losmandy Titan Mount

losmandy2 As for the Losmandy TITAN, I was so happy with my old G11 that it was an easy choice.The mount is absolutely superb. There is nothing to say about quality of manufacture, it just screams Losmandy all over. My mount is equipped with the Gemini Goto system Level 4 and Maxon motors. The system was developped by a Doctor Göerlich. At first, I found the menus of the Gemini controller pretty cumbersome to use until I got used to it… Once you get the hang of it, the goto is dead accurate and even for an old dog such as myself (who likes his coordinate circles) it is fantastic. But, and that’s a big but, there are  bugs in the system, and most Gemini owners will not tell you about it. Bug one, when you slew the scope in RA using the paddle, there is a bug which will cause the mount to carry on slewing until you have to switch off the main power switch to avert disaster! That happens 33% of the time. Bug two, if you try using the “polar align assist”, after a couple of iteration, the mount will point the Eyepiece toward the star, which makes the whole procedure no use whatsoever. For a system that has been on the market what? Ten years, I find that really unacceptable. I am an Embedded Electronics engineer by trade, Hardware and Software, and I can tell you I could have designed a better system sitting in my kitchen! Also, the encoders on the motors are really weak, and I had the one on the DEC motor blow 4 times and needing replacing due to a faulty cable (lots of downtime)… I’ve had so many problems with it that Optique & Vision has promised me an upgrade once Gemini 2 comes out.
Well, now I got that out of my system, it’s a great mount nonetheless.

Celestron Telescope collimation

What follows are my thoughts and technique for collimating the EdgeHD 1400, but I guess it’s relevant to any Celestron SCT.

c14front Collimating the C14 accurately is crucial for planetary imaging. Even though it’s not as important for deep sky imaging, I’ve never seen so much details on deep sky shots than since the scope has been aligned properly…
Now, the only way to collimate an EdgeHD scope is to do it on a star, real or artificial. Using an artificial star implies positioning  it a couple of hundred yards from the telescope to allow focusing. So unless you have a large garden, and, your observatory design allows you to aim the scope horizontally, you cannot do it or only so by removing the scope from the mount. For me it’s just too impractical. That only leaves a real star to collimate with. But, again, at my location, you can almost never see the Airy disks because the sky is just too turbulent for a 14 inches aperture. So, I’ve had to wait 6 months for a night of poor transparency but good stability to collimate the C14 properly. Aiming at Capella which was just about overhead, using a 5 mm Takahashi eyepeace, resulting in a magnification of 782, I started looking at the slightly unfocused star and at the “Fresnel disks”. I adjusted the 3 collimating philips head screws until the rings were all centered on the star in the middle. My advice when doing this is take a few minutes breaks after each adjustment, as you brain tends to see everything centered even though it’s not. Also, use a little cardboard box which you can position on the corrector plate by the screws to get your bearings as to which one you need to adjust. Also, you need a ladder as a C14 pointing straight up is just too high to reach the adjusment screws. Once the rings are centered, see picture below) then focuse the star as much as you can depending on turbulence for further adjustments. airy_collim

Airy patterns (courtesy of Thierry great website: http://legault.perso.sfr.fr/collim_fr.html)

Celestron claims for the EdgeHD family is that, because the secondary mirror is spherical, the telescope is not as sensitive to misalignment, but I cannot believe it as alignement still is sensitive to a 1/20th of a screw turn. Also, when the screw you are tightening becomes too tight, then you need to loosen the 2 opposite screws. Similarly, if you are loosening a screw, then you should tighten the opposite ones. It is good practice for the last adjustment you make to be tightening a screw so that everything is nice and tight and rigid. From what I’ve noticed, slewing the scope about has no effects on collimation, the mechanics being really good.

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Celestron Telescope, 9.5 out of 10 based on 11 ratings