Telescope Reviews: Need advice CGEM, SXD, ?, for AP

Hi Jeff -

I have an SXD mount and I'd say it depends on the OTA you are thinking of mounting to it, and more importantly the focal length you'll be imaging at. You might be happy with the SXD, you might be grumpy depending on the use condition you're planning.

The SXD is pretty light. I have it on a Scope Buggy and its a breeze to pull around the yard. When I was carrying the mount by hand it was easy, but the buggy makes it super simple so I keep the mount attached all the time now. Takes me 15 minutes from opening the garage door to being polar aligned, goto calibrated, and ready to use. No complaints about the portability and set up of the SXD, its nice and light.

Polar alignment is easy, go to accuracy is very good if reasonably well polar aligned and level. The mount hates to be unlevel and unbalanced. Goto suffers a lot if its not polar aligned and level, tracking suffers a lot if its not level and well balanced. The alignment process has some quirks but works very well if you pick the right target stars and are level - I can almost always hit any target within around 0.2 degrees after a 6 point calibration.

I have around 20 pounds on the mount right now between the Pentax 75SDHF, Borg guide scope, Canon camera, adapters, saddle plates, etc and for visual work there's no issue at all with the setup. With my Vixen VMC260L at 3000mm focal length and around 30 pounds (OTA + focuser + eyepiece + other stuff) there's also no issue, the mount works great for visual work even at high focal length. Imaging at 3000mm would be a mess though, and I think a waste of time. I haven't tried it yet but I'm 99% sure I will be disappointed if I try and image with my long FL scope on this mount.

With the Pentax I've had sessions where I cant get 60 second images at 500mm focal length without trailing, mainly due to random declination axis jumps of around 30 arc-sec. Seems to be a random thing as sometimes I have the issue and sometimes I dont. Always accompanied by a small clicking sound from the mount, so I suspect slipping gears on the dec axis due to tightness. Since I've been paying close attention to careful balance and leveling its gotten a lot better, but the dec axis tightness and other weirdness can be a problem. I think as I get more experience with the quirks and have better set ups this will improve, the last few months have been much better than the first few.

I've also successfully taken shots unguided at 2 minutes with no star trailing or dec jumping - at 500mm focal length. I can shoot at 120 seconds all night with around 85% image yield (wind gusts = bad). I've gotten a couple of good strings of guided 5 minute images at 500mm, some good ones at 10 minutes, and a few good ones at 15 minutes. I've settled on 2 minutes for high yields, but I anticipate running this up to 5 minutes as I've been getting much better results by adding the Borg guide scope, PhD, and with a little tweaking my satisfaction has been much improved. Remember this is at 500mm focal length, which should be pretty forgiving. At higher focal lengths the stability will become more and more of an issue though I dont yet have a good feeling where yields will fall apart.

The SXD star book hand controller is easy to use and reasonably intuitive. That said, I barely use it and wish I could turn it off entirely. The LCD back light is ungodly bright, this can be adjusted but at first turn on its as bright as a little nova shining on your mount. Really messes up night vision regardless of what setting you have in the firmware for backlight intensity. In new software builds there is a feature to turn off the display completely after 5, 10, 30 seconds and I keep it set at 5 seconds. I drive the mount via Cartes du Ciel whcih works fine so I never touch the controller after initial setup.

So short answer is, for visual work the SXD is great with regards to its weight vs. carrying capacity. For short focal length imaging I'm getting decent results with a bit of tweaking and learning. Above 1000mm focal length, not sure yet but I can imagine it working up to around 1500mm with under 2 minute exposures.

Some images are up at http://www.astrophotogallery.org/showgallery.php/cat/638. All are shot on the SXD with 60 to 180 second exposures, 120 most common.

Mark

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Vixen VMC260L / Sphinx SXD
Pentax 75 SDHF
Canon 40D / 50mm f1.4 / 100mm f2.8 macro / 28-135 f/3.5-5.6 / 200mm f2.8L

http://www.astrophotogallery.org/u166-doubleglaze.html