O-GPS1 Astrotracer function is phenomenal!

... then it moves the sensor for you in B mode, based on the mm of the lens data, at the same speed stars move on the sensor, so the stars stay put. Like an inbuilt equatorial mount, which is the thingamygummy that follows the stars when you're looking through a telescope.

Ah, I'm enlightened. Cheers Nass Surely it couldn't do it for 2-3 minutes though, could it?

Presumably this would depend on where you are aiming, as some stars 'move' more than others as you head away from the poles.

I just read somewhere that the max travel distance changes between Pentax models, which would indicate that some cameras have more travel in their shake reduction systems than others. That was interesting.

But yes, the max exposure time must be limited to the max sensor travel distance available. All jolly interesting really!

EDIT: Actually this does raise a good point, in that stars 'move' at different rates, so if you have a wide angled lens, the sensor will track the centre of the image at a rate that holds those stars still. If you're pointing near a pole especially, you're still likely to get movement of the edge stars on a wide angle. I'd have to do some thinking as to whether this edges movement would still be circular now also...

So, probably best for closeup work perhaps?...

No, I can tell you it doesn't depend on where you're aiming, the max length it allows you depends on the mm of the lens, the unit gives you a maximum time available which differs per lens. Longer for UWA, shorter for bigma, etc. Beyond this though, I honestly can't tell you much more yet... need to use it more first I suspect that what you say about moving at different rates maybe true, there are quite a few ifs and buts I've been reading about googling it so I'm sure I'll report back in due course when I have more of a clue

The unit tells you how much time you have with the lens you use and the direction you're pointing. But these limits seem a bit optimistic. I don't have much experience, I've only used the 135 mm on two nights but the best I was able to do without stars showing trails was 70 sec when pointing Vega. 40 s worked most of the times and 20 s always worked. Meanwhile the gps was allowing more than 2 min exposure! I think the weak point in this system is the electronic compass which has a precision of give or take 5 degrees. And it seems the closer you point to the zenith (the point in the sky directly above your head) the more trouble the compass has finding true north (as I looked at the compass reading, the numbers kept changing wildly).

Anyhow if the results I've had so far with the 135 mm hold, the tracer should keep the stars in line for five minutes with lenses less than 28 mm f.l. which is amazing!

Here is a version after removing a bit of blue and adding a bit of green. It does look more natural, thanks johnriley.

Awesome, really impressed with this. I realise I was wrong earlier in that the outer stars and inners on a photo do all rotate at the same angular speed, so it should all work fine. Potentially wider angle lens use will reduce the exposure time available for a particular shot is all.

Keen, now just need to find a way of financing something I'm probably not going to use much?! You don't see many of these available 2nd hand yet, nor on special much either

Many thanks for the heads up on this

Yeah it's pretty impressive. I can't wait to use it. I have the camera primed on a tripod set up with some extra eq to help get great focus all ready and waiting, now to wait for some clear skies.

So would this work with a K-5 or is it only available on K-30 and later models?

I hope so since I've just ordered one for my K5.

It works with the K-5 too. just make sure you have up to date firmware.
So far I have only used mine as a GPS logger, still hoping for some clear skies here.

Works fine with K5, I'm on latest version

I'm not normally one to post, but I thought I'd come along to sing the praises of a truly great piece of equipment.

The astrotracer is one of my favourite toys - I mean pieces of serious photographic equipment for astrophotography! I use it with a k30.

In my experience, it can be hugely frustrating to calibrate and you never quite know what you're going to get, but some of the results from the unit are phenomenal in amongst the many could have beens!

Hope the image shows up - and is the right size etc - I attempted to follow the instructions!

Wow! What lens? f/ratio? exposure time? I find the pentax sensors very slow with the reds but you even have managed to get a bit of the Barnard's Loop in the picture! How?

Hi Francois,

It was taken with the 77mm lens at 2.8 for 70 seconds - iso 3200.

It's a single frame, pretty much straight out of the camera - no stacking or dark frame subtraction etc. The only thing I altered in the develop module of Lightroom is a small amount of noise reduction.

Possibly the answer to how is an answer of where! I was lucky in that I was at Lake Tekapo - an absolutely stunning place of beauty by day, a dark sky reserve by night - on a cloudless night and around the new moon.