I have the AT, have had it for about a year and used it lots.
Don't bother with the guide scope, it isn't easy to use in the southern hemisphere. Instead I would highly recommed having a fitting machined in which you can mount a laser and align using that. I have done this (the first person that I know of to), and polar alignment is very very very easy to an accuracy ample for 3 minute exposures with a 50mm lens or wider (crop APC size sensor) every time, and I mean every single time I have tried it.
You won't hear much bad from me about the AT, so perhaps it's almost a baised review from me
. For me, it's been the dream mount. I wish I'd bought it instead of my Losmandy GM-8 years ago, but amongst other things I did back then intend doing more portable longer focal length work which would not suit the AT so well. All the time I spent fussing with the Losmandy GM-8's tracking, guiding, many cables, fussy power requirements, worm issues, etc. With the AT, the first night I used it I plonked it down, aligned it, and within 10 minutes was doing 3 minute exposures with a 17mm lens with perfect results. Every night has been the same since.
I often do 5 minute exposures but 3 minutes is guaranteed with my setup, 5 minutes sometimes. I never fuss with fiddling to get a more accurate alingment once I'm set up, so if I wanted to I'm sure I could always get 5 minutes. I haven't had cause to try longer than 5 minutes.
The AT is singificantly compact, about the size of an adult forearm. I have it, the wedge they sell for it, it's battery, dew heaters for lenses, tripd head, and a few other bits and pieces in an aluminium case and that's the complete kit. I can carry that in one hand, the tripod in the other, and my photo backpack on my back, and I've comfortably walked a good couple of KM with that kit to get to a nice scenic location for some photography. I am looking to get a molded case made fo the AT which would make it even more compact - the current case has lots of empty space but it's the only one I have which is long enough to hold the length of the AT (about 43cm with the wedge attached).
Setup time for me is always less than 10 minutes for exposures up to 3 mins. It litterally goes like this:
- Unpack camera tripod and level it (I use the Manfrotto 055xProB)
- Put the wedge (with AT attached) on the tripod
- Rough polar alignment using compass
- Put camera head (I use Manfrotto 488RC ball head) on the AT. Camera on it.
- Hang the battery off the tripod (I have a 6Ah in a carry bag)
- Attach power cable.
- Unfold AT to turn it on, pre-wind forward.
- Put laser in polar alignment holder and clip switched on
- Look through binoculars at Sigma Oct, with ther hand tweak wedge for alignment (takes about 2 minutes).
- Turn off laser, take it out to keep it warm, start AT tracking.
Ready to go.
What's the catch? Well it's tracking is limited to 2 hours before you rewind it. This isn't much of a problem for normal astrophotography but for time lapse video panning it means you video isn't smooth through that rewind period. To do my alignment method (or use the polar scope) you need view of the southern celestial pole. I have often done 3 minute exposures where I have only aligned using a compass due to this but that's more hit and miss.
The AT isn't a goto, doesn't have DEC guiding. This means it doesn't suit everyone.
I've used the AT visually with my megrez 80 no problem. The weight isn't an issue and is fun to use like this, but longer focal lengths you'd want a mount you can at least manually slew to easily centre targets more easily. Although thinking about it I supose you could just put a Manfrotto geared head on the AT and then you have slow motion controls.
I think the AT came at the right time, there are a combination of factors which make it work well:
- It's accurate RA tracking and portaility
- DSLR's having good long exposure capabilities (giving good results in 3-5 minute exposures)
- DSLR's having live view (for focusing)
Those three things combined mean it works well as a self contained no-fuss unit. Without one of those aspects I think the mount its self would not be as useful.
I use a canon cable interval timer and don't take a laptop out in the field.
Regardng the starlapse: The idea of greater than 2 hour tracking time appeals. It's extra electronic capabilities appeal (tracking speeds etc). It's size an weight does not appeal. I often had tracking issues with my Losmandy GM-8 and having the AT which tracks so accurately in RA has hilighted to me just how often my issues were simply poor RA tracking and perhaps other issues with the GM-8. I got tired of always having to fiddle with the RA worm meshing of the GM-8 something I didn't even have to do with my LX200, 8 years it's senior. I'd need to be convinced these issues were solved or absolutely need the +2 hours tracking for me to consider the extra bulk of the starlapse worth it over the AT.
There have been people who have had problems with the AT. The most common is that upon arrival it doesn't track properly - something slips in the mechanism and it doesn't track. This has caused frustration for others, I haven't experienced it myself.
Pictures of my AT setup:
http://www.rogergroom.com/items/astrotrac_equipment
A selection of photos taken using my AT:
http://www.rogergroom.com/items/astrotrac_images
The mount does cost a bit, the starlapse is cheaper. But for me it has been a clear case of worth paying the money for something which "just works" - really, it "just works", I just point the camera where I want or plonk it down on an otherwise inaccessible spot and it "just works".
Roger.
