Telescopes
Celestron CGE1400 XLT Fastar SCT
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I
received my CGE1400 in June 2006. It was an upgrade for my Celestron
C9.25 - both for the OTA as well as the mount (CGE versus CG-5). C14 is
a big scope, it dwarfs C9.25 with lots of aperture, CGE mount is also
much sturdier than CG-5, and well equipped for imaging. It is much
bigger and heavier so it is not as easy to set up
as C9.25, but I still managed to set it up
myself with no help. However, it wasn't practical anymore to keep it
in my dining room and move out as necessary - too much work. I have
decided to keep it outside in a shed - on my deck. I bought and
assembled Rubbermaid BigMax plastic shed and moved most of my equipment
there. The scope was assembled on JMI Wheelie Bar, it allowed me to roll
it out for observing very fast. I was only worried about possible long
term effects of outdoor storage, where
temperature can go from a very low in the winter to very hot in the
summer. I bought a min-max thermometer and soon I found that max temperature
in the shed in summer reaches between 110-125F. Well, I am writing this
in March 2010, almost four years later, the scope is still stored
outside (now in the observatory), and there are no signs of any
problems, so I guess the scope can withstand reasonable temperature
extremes very well.
The shed telescope storage was a big winner - it takes 15-20 minutes to roll the scope out, connect it and observe. It allowed me to observe more often, but it still wasn't a "moment notice" telescope: 20min + 20min = 40min ... I used to use 10" DOB for "instant observing", especially when I was not sure the weather will cooperate or when I needed just to look at a few objects fast. Complete assembly/disassembly of CGE1400 takes longer, say 30-40min for one person, so it is a portable setup, but not the fast and easy one.
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The
scope's home changed when my backyard observatory
came true in the summer of 2008 and my CGE1400 has been moved to its
permanent location. It now sits on the top of Omega-2 pier equipped with CGE
Adapter Plate from Dan's Pier Plates. And since
CGE1400 is now permanently mounted I have a new portable visual
telescope: Obsession 18" Classic.
Until the summer of 2008 CGE1400 was both visual and imaging scope. The
aperture rules
, the views are incredible,
C9.25 or any other of my previous scopes could not compare. I spent lots
of time just looking at old Messiers, and for a long time I was just
rediscovering all the objects that were so familiar from the nights with
C9.25. All the old stuff was like new now!
I was lucky with my old CG-5 that it worked well, but CGE is an order of magnitude better (I
never used CG-5 with the new version of the hand controller though). Without precise polar align it was able to bring objects close to the middle FOV
of 20mm Expanse eyepiece (0.34 deg), and at least to the edge of 15mm
Expanse all the time. At the beginning I have measure the accuracy
of pointing on a few examples, like on Struve 2308 (RA18:00.2 DEC+80:00
– it was the largest Dec on my list for this night) and the error was
slightly less than ~10 arc min this time. On Cat's Eye Nebula
(DEC+66:38) the error was smaller, ~5 arc min. I stopped doing 2+2
alignment - I am getting very good results with just 2 alignment stars,
the mount remembers cone error and misalignments and they probably stay
very similar from one observing session to another. And those days I
used to roll the telescope out of the shed each time and set it up on
the deck only in the approximate same position (I had 3 marks for the
wheels). Now that the scope sits in the observatory I stopped doing even
2 star alignment - I just use "last alignment" for a few months.
When
imaging at long focal length (f7 or f8) I usually use "precise GOTO"
command, it requires a sync on a bright star in the neighborhood of the
target, but then it always places the target object on the camera sensor
with no further ado.
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I have added Celestron C80ED refractor on the top of C14 with Ken Millburn's
dovetail bar and rings. In order to balance it's weight I had to add
third full 22lb counterweight, as shown on the left.
CGE1400 works very well for astrophotography - I used it with Canon Digital Rebel (XTi), then with Canon40D and filanlly with CCD-Labs QHY8 in various configurations. It is extremely versatile tool for astrophotography: from f11 to f2 (with Hyperstar). The payload of my setup is close to the maximum for CGE mount at about 58lb: 45lb C14 OTA, 8lb Celestron C80ED refractor and 5lb rings/dovetail. I asked Celestron if it is too much when I was about to buy it, and they answered that the maximum useful payload (NOT including counterweights) for CGE mount is 65lb. There are no problems with autoguided exposures of about 6 minutes at any focal length - see "Astrophotgraphy" section for images and "Imaging with CGE1400" for more details about imaging setup.
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In the past CGE mount received some criticism (C14 OTA reviews were always very enthusiastic), but recent reviews of the mount are very good (like these two reviews on Astromart site here and here). It looks like Celestron fixed all the initial problems and the quality is now consistent and good. I am a very happy owner!
C14 does not require frequent collimation, even when used with Hyperstar from time to time. However, correct collimation is important, especially for planets and the Moon. There are many articles on SCT collimation, both online (here or here) or in print (Rod Mollise "Choosing and Using a New CAT"). In practice, one usually has to do final C14 collimation on a slightly defocused star, in-focus diffraction rings are too small for an average seeing, but this level of accuracy is more than enough.
C14 does not require corrector cleaning almost at all. So far (March 2010) I have done it only once in the summer of 2009, after I moved the scope to the observatory and I discovered quite thick layer of dust (inside and outside) that I wasn't able to blow away. If it is only dirty outside one can clean it without removing it from the OTA, otherwise it needs to be removed and cleaned on both sides. It is not difficult to do, but you have to be VERY careful at all times, and preserve the original corrector orientation / secondary centering. There are many good online articles about it, especially on C14 Yahoo group site.
OK, so now: have I had any problems with it? Yes, I have, but only a minor one: tripod legs locking screws. The original screws that are supposed to lock extended tripod legs in place are sloppy, and allow for slippage, my setup is more susceptible to this than average since with C14 and C80ED on the top if it I am pretty much at the weight limit for the mount. There are two simple solutions. You can get a regular screw from a hardware store and tighten it properly, but then you may dent your tripod leg and scratch the paint. The other is to use hose clamps and install them on the extended part of the leg – you still may scratch the paint. I applied both and no problems since! Before fixing screws I had to adjust level every time I rolled the scope out, this is how found the problem. I would strongly encourage new CGE1400 owners to address this problems since if you don't notice the slippage your tripod may get very uneven and then trip over ...
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When CG1400 was my primary visual scope the most used eyepieces were for wide field Orion Optiluxe 40mm and UWAN 28mm (82 AFOV); Orion Expanse 20mm and 15mm for middle field of view; then Tele-Vue Radian 10mm for higher magnifications. Sometimes, on exceptionally steady nights I used 2x Barlow on the planets and the Moon. The table below shows viewing parameters of the eyepieces I used at that time.
NOTE. 1.06 degree FOV in the table above is purely theoretical - using 0.6 reducer and 40mm eyepiece will result in severe vignetting. The widest field I used was 0.63º ...
There are two good discussion groups devoted to this hardware C14 Yahoo group and CGE Yahoo group, and an excellent general Schmidt-Cassegrain Yahoo group SCT-User with lots of more information. Highly recommended!