Astrotrac for AP? Any users care to chime in?

[Poita]

This thread came about as an offshoot to another discussion, so I thought I'd better clean it up and start a dedicated thread.

Are there any Astrotrac users out there that would care to share their experiences, pros, cons, hints and tips?

I'm becoming more enamoured with wide field photography and the Astrotrac looks like a great setup that is easy to transport to dark skies, but I'd love some feedback as to the pitfalls and advantages of the system. Any input appreciated!

[naskies]

Following on from the previous thread (http://www.iceinspace.com.au/forum/showthread.php?p=806620#post806620) , I find polar alignment pretty simple for wide angle and/or very short exposure work.

Accurate PA has been a bit fiddly for me so far - probably because I'm used to how sturdy and precise the EQ6 is by comparison.

I do have the polar scope, but haven't been terribly impressed with it - I don't bother with the EQ6 scope either. I've always used PHD-assisted drift align though... the AT's polar scope seems to get rave reviews from some people.

Based on six full nights of use so far, I'd say the AT is excellent for wide angle shots and travel portability, but it's definitely no replacement for "proper" imaging on a GEM. Since there's no Dec axis, you'd have to dither the frames by hand (release the ball head, move the camera slightly-but-not-too-much, reattach, hope you haven't screwed up the PA, etc)... you might go nuts having to do it every 3-5 mins :)

I'd be very interested to hear what other AT users have to say.

[Liz]

Looks good Peter, but a bit pricey, for those on a budget.
http://www.astrotrac.com/

I was looking at the set up in this months AS&T - a 'simple' hinge tracker. Obviously not as good as the Astrotrac, but maybe an alternative. One of the members in our club is having a go at it for me.

I am also a fan of widefield AP. :)

[Poita]

This is the big question for me, does the astrotrac significantly outperform a dual arm barn-door tracker like Rowlands one here:
http://synergous.com/flatpress/?x=entry:entry111127-004915

Has anyone used a guide scope with an AT?
I'd be interested to know if it was stable enough for my modified PST (effectively about the same size/weight as an ED80) for solar imaging.

[adman]

Hi Peter - I know your OP asked for info on using the astrotrac - but have you seen the Losmandy StarLapse (http://losmandy.com/starlapse.html)system - basically 1/2 of a GM-8 with a controller for timelapse astro and terrestrial use. Thread here (http://www.iceinspace.com.au/forum/showthread.php?t=84738&highlight=starlapse)

[Poita]

I have, but the size/weight/cost of a full setup doesn't sway me from just using an EQ6 for photography. The attraction of the Astrotrac is the ability to throw it into a backpack.

[rogerg]

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.

[naskies]

Roger - You've taken some beautiful photos! The laser polar alignment approach is ingenious - I can often see the SCP by visually star hopping between Crux, LMC, SMC, and the Octans, but lining it up through the polar scope is a challenging to say the least. The laser would make it very quick and easy.

Peter - Astrotrac claims a peak-to-peak periodic error of <= 5 arc seconds. From what I've read by people who have actually tested it, this is accurate. I'd say that poor polar alignment and tripod/ballhead flexure would be the usual culprit behind trailed stars.

I've used a guide scope with the AT - very good for drift aligning, and PHD works just like with my EQ6 except it doesn't have Dec guiding obviously.

[barx1963]

Hi Roger
Well done on using the Astro Trac so successfully. The laser idea was one idea I had thought of when I have been considering the AT as a possibility. The issue I saw with this was how to ensure that the laser itself is accurate, so the bean is actually pointing exactly parallel to the barrell of the laser and how to mount it accurately on the AT itself.

Malcolm

[rogerg]

Thanks.

Interesting to hear of someone who's done autoguiding with it, I haven't tried that myself.

FYI, PE seems to not present its self in my images, but I haven't measured it myself.



I have two theories and I think either works fine, or at least seem to for me in practice. I used the first initially but then realised the potential of the second and use that more now but can't say I've had a problem with polar alignment being off either way.

1) I always have the laser rotated the same way, positioned on the same side/place of the AT. I hence very quickly become familiar with where the laser should be pointing near sigma oct for a good alignment, so any misalignment of laser or holder end up being factored in by just knowing where it should be pointing.

2) By putting the laser in and swivelling the polar alignment arm of the AT around the mount you see the extremes of pointing error in the configuration. So, looking through the binoculars you swivel the polar alignment arm around from side to side a couple of times quickly and the centre of the circle that is drawn in the sky by the end of the laser is where the true centre of alignment is and where you need to put the south celestial pole.

Not sure if they're scientifically accurate, but they seem to work :shrug:

:)
Roger.

[naskies]

According to my calculations, a 300 mm lens would give a field of view of 5 arc secs per pixel on the 6.4 um pixels of my 5DmkII - so anything shorter than that wouldn't be affected by PE.

[netwolf]

There are other options popping up for example this one from japan called toast-pro
http://www.tan14.com/Others.htm

http://www.astronomyforum.net/astronomy-digital-cameras-forum/108454-toast-pro-looks-very-cool.html

Seems very compact and portable.

[mithrandir]

Their web page appears to say they are out of stock.

TOAST-Pro Set-B
Body, Polar finder unit, Battery box, power cable, Compact soft carrying case
96,600 Yen - in real currency around $AU1300.

Hmmmmmmmm.

[netwolf]

Andrew, there is a direct website i found for Toat-tech.
http://www.toast-tech.com/

Also this guy has an interesting project going on Project Orion, aims to build something for around 300$.
http://forum.timescapes.org/phpBB3/viewtopic.php?f=17&t=4859&sid=8e54bff7730960dc711b2a32a50feef e
Also has a Project Chronos (link in his signature) for time lapse machine.

Regards
Fahim

[renormalised]

Pity it's in Japanese....would be nice to know what it's going on about the kit:)

[luigi]

Another AT user here.
Roger has said everything very well.

I do use the polar scope, from a dark location it's easy to find the trapezium near Sigma Oct and then the alignment is very accurate. From a light polluted place I use the C&P method (compass & pray).

I've done up to 3 minutes with a 135mm lens and 5 minutes with shorter focal legths even with a very very raw alignment.

The best about the AT is that you can setup in 5 minutes.

In a recent trip we did some tests and without guiding the AT is more accurate than 2 EQ mounts we also had.

[mithrandir]

Fahim, that's where I got the price.



Carl, Firefox asks if I want pages translated. It gets Google to do the work, and does produce Jinglish but you get the general idea. It does a much better job of western European languages.

[renormalised]

I use Firefox, Andrew....got the latest version, actually (9.0.0). Don't have it setup to ask if I want the page translated....suppose I should:):P

[mymoon]

I too am an Astrotrac user. I have to modify the astrotrac to allow me to image at 3 deg N.

http://www.pbase.com/aziz/image/142471813


But the Astrotrac fondly known locally as the Gunting (scissors) is still a lot of equipment to cart around and set up. Ok by car but if there is any air travel involved this Pentax alternative looks interesting especially if it was a combined terestrial and astrophotography trip as it would be for most trips..

Click http://www.pentaxforums.com/forums/pentax-k-5-forum/167500-k5-o-gps1-astrophotography-pix-experiences-namibia.html


Pentax claims their set up on the tripod are as follows:

(Click http://www.pentax.jp/english/news/2011/201107.html)

For 50mm lens up to 300 sec

For 200mm lens up to 300sec at zenith reduced to 160sec at 45 deg.

The FOV for Canon APC cameras at 200mm is 6.5X4.3 deg enough to frame both the flame nebula and Orion nebula

The whole set up camera and lenses and tripod and spare batteries can be carried on a backpack or a a aircraft cabin flight bag.

Interesting.

Any opinions/user experience.

cheers

[JB80]

From everything I have read and seen plus given the reports in this thread it just backs up that the AT is most likely the portable widefield mount of choice, I don't think I have yet to hear a bad word about it.
With that said however I have considered this and don't think it's the mount for me, at least not just yet. Although I can't really say I have any experience of the mount.

But then I have no want to put anything larger than a dslr and lens on it. The Pentax system looks good but that would require a change of camera kit. The losmandy doesn't look portable enough and the toast is just too expensive.
Basically my mind has settled on the Vixen Polarie and I don't think I can be talked out of it, it offers supreme portability given it's not much bigger than an old VHS tape and the results I have seen are every bit impressive.

[MrB]

Not trying to talk you out of it, but have you seen the new iOptron mount?
The SmartEQ has goto but can only take an 11pound(5kg) payload, tho it looks pretty good for the US$399 price. It's not on their site yet, but there are a couple of Youtube sneak preview vids from NEAF an they are listed at the following site:
http://www.altairastro.com/product.php?productid=16498

[JB80]

I have briefly skimmed over that before, I think it would be a great option at that price. I best not think it over too much. Plus I'm after something before it's June release.
For me I want something that is easy with air-travel, recently we did a trip and it was easy enough to take my camera tripod, camera & accessories and with the polarie that's essentially all I would need on top of what I would already be taking.

I think the other mount options would be great as a 'put in the car' portabilty option and maybe one day when I don't have to drive so far to find dark skies I would consider it more seriously.

I wonder if Peter decided to go the AT route in the end?

[Poita]

I bought the Pentax kit to try it out, it works just as they claim it does, it is really neat. I bought the k-r pentax DSLR and the GPS unit that has the startracking feature. You just do a 30 second calibration and you get great tracked shots from a standard tripod, it is amazing.

I will be selling it up shortly though as I have caught the solar bug, but for anyone interested in wide field, it doesn't get any more compact that just a DSLR on a tripod and nothing else to worry about! The Pentax can take just about any lens with inexpensive adapters too.

[rogerg]

Interesting. What was the battery life like? Ever try running it for 4 hours of photography for example?

[JB80]

The Pentax did always look good, hopefully more companies will follow a similar path.
That's a good question too, did it have any extra overheating issues aswell by running the GPS unit for an extended period?

I just ordered the Polarie so it's inbound from Austria as I type.

[Poita]

I have only run it for about two hours at a time, with no issues.

It can also take AA batteries which is extremely handy, and you can get a power adapter to run it from the mains or an external battery.

[Kimbo]

Hi Roger,

I'm considering an AstroTrac setup & was wondering if the wedge is a 'Must Have' accessory or is it just a nice extra? Does it make the imaging process easier/better? Your view would be appreciated.

Cheers,

Kim

[rogerg]

Kim,

You need one type of wedge/mount or another to put the AstroTrac at the right angle to align with the south celestial pole. The two most common options are the geared Manfrotto head or the AstroTrac made wedge. A lot of people use either of these, I haven't heard specific complaints about either.

I prefer the wedge because I think it's machined nicely, is solid, is made for the job, has fine adjustment, etc. I also think it leaves the AstroTrac more centrally balanced on the tripod to what the Manfrotto geared head does.

A lot of other people seem to use the Manfrotto geared head with success, so it can't be that bad.

I think the cost is comparable.

I hope that answers your question?

[rcheshire]

The advantage of the AT is weight, the electronic package and reliability. I have agonized over buying one for several years.

EDIT: so as not to be misleading and referring to the potential of these devices in general, favouring the design over similarly priced conventional drives, including the capacity to produce very low PE values - the need for correcting the drive because of inherent geometrical characteristics is noted...

The tangent arm design is attractive because of the effective diameter of the RA gear and the very fine resolution of the worm itself. Even without a microprocessor the AT would track accurately.

EDIT: given the capacity to fabricate this kind of performance with relative ease...

I think the <5 arc seconds peak to peak (no correction) is conservative. A good tangent arm is quite capable of that.

The reason I didn't buy it, was concerns about rigidity - I think these are unwarranted providing the tripod / pier /wedge is solid enough.

A second reason was the quality of the finder scope. Which I hope is fixed, after mentioning its shortcomings (build quality) to the manufacturer. I bought one to align the Tracker - and it worked very well with some modification.

If you have a solid tripod that can be accurately leveled and stay in alignment when locking down, the rest is academic.

I think about the AT frequently, like something I should have done. Occasionally, some of the big US stores sell demo packages at a reduced price.

[rogerg]

You are right that rigidity comes entirely down to the tripod it is on, and what you use to angle it at the SCP (wedge etc). The AT its self really doesn't have anything which can not be rigid, it's flat surfaces against flat surfaces. A solid tripod, the more solid the better, is a must.



I wouldn't rely on the polar scope in the southern hemisphere. Bit hard to use. I don't recall them changing the design but maybe if you think so :shrug:



I have never seen error in my photo's which is in RA and not a result of polar-mis-alignment. Most of the drift I see is due to atmospheric refraction because I often image with the horizon included and continuing up to a reasonable altitude (wide field).

[rcheshire]

The AT, from what I can see is very accurate with good polar alignment.

Shorter exposures and more of them perhaps to minimize refraction artifacts?



No short cuts there, even with an EQ mount.

[rogerg]

exactly :) that is what I do but you only learn when you have good RA tracking just how much impact refraction has :) This is where Registar has big advantages over DSS.

[MrB]

The AT has an Isosceles drive, which has even less error than a tangent arm, but both still need the uC to compensate once exposures go past a few mins.

[Kimbo]

Hi Roger,

Thanks for the feedback :thanx:. I already have a Manfrotto 055XPROB tripod & a 496RC2 ball head so all I need to buy is the Astrotrac & the 410 Geared head. My birthday is in three weeks so I might starting giving hints to my family!

Kim

[rcheshire]

http://articles.adsabs.harvard.edu//full/1995JBAA..105...65C/0000067.000.html

This is delightful reading, for anyone interested in tangent (isocelies) drives.

[mbaddah]

I just placed an order on a Astrotrac. I've been contemplating one for over a year and finally decided to just bite the bullet and cough up the dough! Can't wait for it to arrive :D

[mbaddah]

My Astrotrac arrived!!!:D Can't wait to give it a try.

I'll post up the results as soon as I give it a whirl.

[rogerg]

Congrats! :thumbsup: Look forward to hearing how you go :)

[MrB]

Nice!
Who did you order it from and how much was the shipping?

I have a dark-sky trip planned soon but due to work commitments(aaargh!!) I don't get enough time in my metal-shop so my homebrew tracker doesn't look like it will be finished in time :(

[naskies]

Congrats Mohammed! If you haven't found it already, the Astrotrac Yahoo Group is a great resource of information, especially with regards to helpful tips and tricks (just search for "astrotrac yahoo" on Google).

Watch out for the polar scope holder - it's very, very easy to knock it out by accident (I do it virtually every time). Some people use rubber bands, cable ties, etc to hold it in place.

The polar scope is a bit dim (in my opinion) for finding the Sigma/Chi Octans alignment stars, but once you get them the polar alignment is pretty good. My shots from last weekend (in the Deep Space forum) were taken with a 135 mm lens x 3 mins... pixel perfect with no trailing using the polar scope to align.

[Poita]

I've had more of a chance to play with the Pentax system, and it really is impressive. No star trails and no mechanical devices needed, just the DSLR and the GPS unit. It means I don't need to carry any extra gear at all, just the standard tripod, camera and GPS.

I hope they make it standard on all their new cameras, I can envisage a day when it could autocorrect on a guide star as well, now that would be something!

[bfonseka]

I cannot see Sigma Octantis from where I live (in Sydney) due to light pollution. So I used a digila level to do my elevation and fine tuned the azimuth (initially set with compass) with my little mini guidescope and PHD graph. It worked very easily and quickly. I have a manfrottor geared head and I also bought an extra dovetail base and quick release plate to mount the guidescope.
This arrangement easily did 2 minutes with perfectly round stars with a 85mm lens. Its very quick and easy to do. Planning on taking my Astrotrac to Darwin next week and Alice Springs and Uluru next month.