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Astrotrac TT320X vs TT320X AG


frostynixon
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Hello everyone,

i`m thinking about buying an astrotrac mount. To save some money i consider buying a used one. I would like to know the differences between the TT320X and TT320X-AG. The TT320X has "solid" arms and no autoguider port as opposed to the TT320X-AG. These are the obvious differences. Are there any other differences especially concerning periodic error?

Thanks for your help!

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I have used both and they are the same as far as I can tell and the specification was the same regarding PE and tracking accuracy.

The original one may be a bit more rigid being of solid construction but not by much. The newer one is a tad bit lighter.

The main difference is resale value, the newer one with the AG port will be more in demand, even though I have never really guided mine.

You can occasionally pick up a bargain original one, just keep your eyes peeled.

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Thanks Stuart! That`s valuable information.  I guess i can live without the outguider port. I would like to do 5 minute exposures up to 200mm. I know that PA is crucial. But i think the astrotrac is the only portable mount that has fairly low PE. I will look for the older model then hoping to find a bargain :)

best regards

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The AstroTrac can handle the Canon 500mm f/4 L IS lens but only on a sturdy tripod and the help of a solid wedge and balanced head, without them it is much trickier.

With regards to 200mm @ 5 minute exposures, that should be quite easy to achieve with a well collimated and aligned polar scope.

Don't dismiss a newer version, they also pop up occasionally as well...good luck!

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The Losmandy StarLapse is about the same money. More versatile with excellent PE and tracking. I was looking at the Astrotrac I bought their pier and wedge for my StarLapse. But I've since added the DEC axis and now I have a full GEM with autoguiding on both axis PEC backlash control and all that.

Most errors you need to guide out occur in DEC. If you are correctly polar aligned that axis won't deviate much just the normal PE. Some of my runs go over 2 hours so that is another reason I didn't go the Astrotrac route. They do track very well low PE I also didn't want to use a ball head. I was able to mount an encoder on the SL camera mount so I could use digital setting circles with it. I'm not that interested in star hopping I just want to take pictures so not having to fuss with finding the stuff is a big positive with me. I also wanted an upgrade path so I didn't have to sell and buy again.

It also functions as a 14 speed motorized panning head.

Another feature the autoguided Astrortrac would have is in polar aligning. Using PHD2 polar align tool. Gets you right on the money in very little time compared to drift aligning. That would be a good reason to go with the one that has autoguiding.

I found using a regular video tripod so I could tilt it to the pole star was a major pain. Getting it aligned took forever. I looked at geared heads but to support the weight the Astrotrac or StarLapse can handle the head would cost more than the pier and wedge. if your tripod has a wide saddle for the wedge it will work great. I had mine on an induro but the base on the induro wasn't wide enough too much of the wedge hung over the sides and with the camera and all on it close to the meridian flip point it drooped quite a bit. With the pier none of that happens. Its very solid. Judging by the quality of the wedge and pier I have no doubt the tracker is excellent. They are very helpful when you contact them even if you aren't using all their products. The machining is top notch everything is strong but very lightweight.

Griz

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Thanks for sharing your experience Griz! I didn`t have a look at the Losmandy so far because i got the impression that it is quite a bit heavier than the Astrotrac. I will have to do a little more research on those candidates. Thanks for your help!

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Its 8.5lbs for the RA axis. It will handle 30lbs. If you add the dec axis you will end up with something like this.

First-Night-sm.jpg

In single axis mode its like this.

StarLapse-new-1-sm.jpg

The tracking is excellent

PhdLog-2.jpg

Couple of ways you can add goto if you want as well. I put encoders and an Argo Navis on mine. I have a setup you can add for the camera mount to allow computerized pointing as well. Costs about 50 bucks to add that in. Drill 3 holes and a cut out for the cable in a box mount the sensor and thats about it.

encoder%20final%20-sm.jpg

Just made sense to me to buy something I can just add onto as I grow and want more sophisticated equipment. The pier wedge and RA axis weighs in at 22lbs so is not that hard to move around. One of the reasons I went this way is it will break down into small chunks that aren't hard for an old geezer to get to the yard.

Griz

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  • 2 weeks later...

Hello,

i just wanted to report back. I`m about to receive a two year old Astrotrac TT320x-AG that i got for a very reasonable price (especially considering that  a new unit is 120,- more than last year). In the end i was more interested in the Astrotrac than  in the Losmandy because it seems quite a bit lighter and also it was easier to get on the used market. Will report back once i got my first results! Thanks all for the information :)

best regards

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Hello,

another follow up from me :). The weather is not really good around here. Today we had 1.5hrs relatively clear skies (but full moon) and i wanted to try out the astrotrac.

Here is an 8 minute exposure with an 85mm f1.8 lens at f4 and a Nikon D5300.

Astrotrac Firstlight

The image scale is 10"/pixel. Especially in the center the stars look quite tight imo, but abberation show up soon when looking towards the corners. Theres a little bit of trailing visible, which means that i need to work on my PA routine. I bought the astrotrac to get 5 minute exposures at 200mm and about 5"/pixel. Given my first try that seems totally doable. I`m very happy :)

best regards

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Hi Frosty, looks good so far, I am sure that you will manage to achieve your goal once you get your polar alignment sorted.

Although I have got the wedge and the head I (usually) image with a heavy 500mm f/4 lens (circa 3.8kg for the lens + ~1kg for camera/accessories). Here's an example of a 3 minute sub @ 500mm on a full frame sensor:

http://stargazerslounge.com/topic/229791-a-3-minute-full-frame-sub-on-an-astrotrac-500mm/

Have a read of these posts regarding collimating the AstroTrac polar scope and aligning the polar scope arm:

http://stargazerslounge.com/topic/179292-astrotrac-first-and-second-light/?p=1858491

and

http://stargazerslounge.com/topic/203486-astrotrac-polar-scope-collimation/?p=2154305

and

http://stargazerslounge.com/topic/194888-astrotrac-polar-alignment/?p=2042260

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Hello,

another follow up from me :). The weather is not really good around here. Today we had 1.5hrs relatively clear skies (but full moon) and i wanted to try out the astrotrac.

Here is an 8 minute exposure with an 85mm f1.8 lens at f4 and a Nikon D5300.

The image scale is 10"/pixel. Especially in the center the stars look quite tight imo, but abberation show up soon when looking towards the corners. Theres a little bit of trailing visible, which means that i need to work on my PA routine. I bought the astrotrac to get 5 minute exposures at 200mm and about 5"/pixel. Given my first try that seems totally doable. I`m very happy :)

best regards

If there is trailing it is minimal, so PA was pretty good.

The lens has varying degrees of abberation as you say, it's not equal in each corner.

Top and bottom right has pretty bad sagittal coma flare.

Think you will do ok with the Astrotrac.

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@Stuart: Thanks Stuart for the links to improving the astrotrac performance! I admire the results that you get with your astrotrac-lens combination. Your pictures were one of the reasons why i bought the astrotrac and not one of the smaller trackers (the losmandy was out of question because it seems much heavier). At the moment i see the astrotrac only as widefield mount, but as you have shown it can also be more than that. For now i`m using my Manfrotto 410 (already owned before) as polar wedge, a Sirui K30x for the camera and a Feisol CT3442 as tripod. For the little weight i put on there yesterday this combo was ok.

On the long run i can see myself buying the astrotrac wedge and maybe a sturdier tripod (but i would like to keep the tripod travel/flight compatible).

@Mike: At the moment i`m trying my two "tele" objectives and so far they are performing not very good. I`m especially disappointed by my 70-200 Nikon lens, which i have to stop down to f5.6 to be coma free (on apsc). According to reviews it actually should be much better and show no noticable coma already wide open. I´m wondering if i got a lemon there. The strange thing is that on my D800 the lens performs much better even if i compare full frame vs apsc frame. So i wonder if something with the astro modification of my D5300 went wrong (replacement filter of bad quality?). I intend to open a thread on that matter once i gathered enough data for comparison.

best regards Matthias

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