Ah, OK. Do they still sell "wedges" to place these fork mounts into equatorial mode? (I have one on a 8" Meade, but it was purchased some 20 years ago).
In any case, the forks (either single fork [kinda oxymoronic name, but that is what they call them], or double forks) don't usually have as precise and smooth tracking even when mounted on a wedge.
Even if the alt-az mounted forks are precise enough to track a centrally located star, the entire image will rotate around the central star (or the star that is being used in autoguiding) over a long exposure.
Unlike professional telescopes, the amateur forks are really meant for casual, visual work where simplicity trumps accuracy. If you get further into astrophotography you might consider deforking the OTA and mount it on a German mount, or designs adapted from German mounts like the iOptron CEM or RainbowAstro harmonic drive mounts.
I forgot to mention that the star detection will also ignore stars that are too sharp (1 pixel in size) since those are likely to be hot or warm pixels on the camera sensor.
Oh, if you can't get the tracking accuracy to improve, try to use much shorter exposures. Just bump up the gain of the camera to compensate.
I have successfully plate solve for polar alignment (with the very low read-noise ASI2600) with under 0.5 second exposures (in fact, shorter exposures are the only way to plate solve while we are still in astronomical twilight). When it gets darker, I would bump the exposure up to 1 second (on a 85 mm aperture refractor). I have never needed more than a 2 second exposure to successfully plate solve in the star starved polar region. But -- make sure the OTA has tack sharp focus to use short exposures.
The Detect Star Tool has also successfully found Deneb and Vega one hour before the Sun has set, by using very short exposures, like 0.05 seconds. Again, if the OTA is in very good focus, otherwise the flux from the star is spread over too many pixels and fall below the sky background brightness or camera read noise.
Try getting good focus first (get a Bahtinov mask for that) and then reduce the tracking error (good polar alignment, reducing exposure time, etc). Then play with exposure levels. If you have a very bright star in the frame, you may have to expose so that the Max ADU saturates (above about 65520) to make the dimmer stars appear over the read-noise of the sensor. Once a star is over the read noise, exposing for much longer does not really help since the sky background will be climbing too.
Good luck,
Chen
