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The tracking mounts of the (affordable) lower and middle class all show a more or less prominent "periodic error" that is caused by imperfections of the worm gear that drives the two mount axis. This error can be corrected by the mount itself (more or less good). But besides this there is always a remaining inaccuracy in the polar alignment that leads to a drift in the dec-axis of the mount. These two factors limit the exposure time especially with long focal lenghts.

To solve this there is (free ) guiding software in the market that connects to the drive and a little guiding camera that is connected to a separate guiding scope that is mounted parallel to the imaging scope. The whole thing is called "autoguiding). The guiding cam transmitts an image of a star to the software and if the star shows a relative movement the software sends correction orders to the mount. The costs lie around 200$ - 700$ I think. No serious astrophotographer with lenses > 400 mm or so who wants to reach imaging times of > 3 minutes will be able avoid the extra stuff and money for autoguiding techniques on the long hand .

I did not want do use a notebook for autoguiding and I decided very early to invest into a little ingeníous box from Austria called MGEN. It is tiny like a smartphone and keeps the whole gear in track over the whole night and completely autonomous. And it controls and fires the exposures besides other tricky features.

MGEN | Lacerta MGEN-II Superguider, mit Sony CCD-Chip. (der Autoguider Verwendbar sowohl in Remote Betrieb, aber auch ohne Computer). Handbox, MGEN Kamera, Verbindungskabel, USB und ST4 Kabel, Zig Anzünder Kabel. | Teleskop Austria | LACERTA

Yeah, I need to start autoguiding. An MGEN is likely the next purchase. Also, thanks for the DSS advice again! It works for me! Posted things at CN, and will post here too.

I can do up to 5 minutes unguided with my mount at the lens/tc combo at 630mm. May be able to go further, but I have not yet. Once I get my astrographs in (should be delivered this week) I expect less coma, astigmatism, and bloating, so I should see an improvement.

OK, thanks. For some reason I never saw a website indication about this response.
Ouch. That's probably over AUD$2000 for a tripod, motorised head and the autoguider, aside from needing a way to precisely align the spotting scope with the camera. Easier to attach it to a telescope, but then there's the additional cost of a telescope. As much as I'd like to get some better photos of the stars, I can't justify that sort of money. I think I'll persist with the hit and miss astrotracer. It's a shame - it's a beautifully clear sky tonight but I'm too tired to go out and enjoy the stars!

For wide field I also use the Astrotracer/K3ii. What I said about autoguiding beginns to strike for lenses a telescopes above 300 mm focal length in my opinion. If you use shorter and faster DSLR lenses a "normal" mount gives time enough to do wide field astrophotography. I started with the O-GPS-1 on the K5 and "upgraded" to a Skywatcher Star Adventurer which is a cheap little light weight equatorial mount which was fine for my 2.8/70-200, 4/200 and shorter. I could live with the 30% junk that came from periodic error and the stars were round enough for me. Compared to the work with the O-GPS1 it was extremely comfortable to shoot DSOs with the little mount. The additional autoguider became necessary after I acquired a 400/5.6 which I had to stop down to F6.3. And the bigger mount (Skywatcher AZ-EQ5 was then necessary after I was seduced by a used 80/480 mm Triplet APO that was too heavy for the Star Adventurer together with the DSLR and the finder scope.

Looking back and extrapolating foreward I think AP is fun in all stages of experience and on each level of equipment if one does not overstress the own expectations and/or the capabilities of the equipment.

Greetings from the cloudy side of the planet to the downunder side

The ability of the Equatorial mount to track for long periods depends on the accuracy of the polar alignment. The better the alignment the more accurate the tracking. As a practical matter it's difficult to get extended exposures without autoguiding to provide feedback correction to the mount. Periodic error is inherent in any tracking mount no matter how high the quality and precision of the construction. Better mounts provide a method to correct for it but it does exist in even high end mounts. Because of these things better results can almost always be realized by taking multiple exposures then stacking them as part of the post processing workflow. The tracking only extends the length of time the shutter can be left open for each exposure.

In addition, air currents, extraneous light sources, aircraft flying through the image area, heat distortion, transient cloudiness all combine to make an image less than ideal. By taking multiple exposures and stacking them these effects can be removed in the process of creating the final image.

You can get a tracking camera mount for a little as $300 US and get some really spectacular results. Also look for some gently used equipment which will be fully functional but a lot less $$$.

I can get dead on tracking up to about 3 minutes at 630mm with mine unguided pretty consistently. I bet if I am super careful with a polar alignment and vibration pads I could double that, maybe more. I am going to try to get 2+ minutes unguided with 1624mm fl on my TPO 8RC.

I went low end but I think it works well. I got (what I think is) a planetary camera - no markings - thrown in with my purchase of a nexstar. I added an Orion Mini 50mm guide scope, Orion Mini 50mm Guide Scope | Orion Telescopes , and it works with PHD2. I've seen excellent images coming from a similar setup - using a ZWO cam instead of the cheap one I have.

PS: I put in an order for the ZWO ASI120 because the freebee appears to lack sensitivity - don't always find a star to track.

What mount did you get? Also, I now know that 5 minutes unguided for 600ish fl is doable with the zeq25 and 3 minutes with over 1600 fl is fine. I may see how long I can push it, especially after a slight tune I did on my zeq.