What causes PlateSolve2 to Fail?


I have almost never had problems with PS2 plate solving, but tonight, it failed repeatedly. I know there are several parameters that can be adjusted, but tweaking a couple of those had no benefit. I ended up using Blind Solve (Astrometry.net) as a failover, but of course it is slower. Interestingly that too failed at the end. No, there were no clouds. I was using 30 second exposures. Aren’t those long enough? The focus seemed reasonably good, at least good enough that plate solving should have worked I thought.

I see from the forum archives others have experienced this behavior as well. Has an answer ever been found why this sometimes happens even on the same target? What are the things that make PS2 fail? What do I look out for? What do I adjust?


A year ago I had many nights with PS being off for very well known targets or failed entirely. PS2 and Astrometry. Didn’t matter which. Some solves failed while the object was in the center of the screen. Sometimes PS would place the object in the center, yet another object situated nearby couldn’t PS, failed.

What worked for me is doing a manual PS of 8sec/2xbin image, near the pole. Not exactly on it, I’m typically 88deg or so. I don’t have permanent setup, so I polar align and such, then park the scope to 90deg (then unpark), and then offset a bit before taking the image. I right click and choose solve, blind solve, the image taken from this position, it gives the thumbs up as 100 confident, and after that every slew/center on is good the rest of the night.

This is what works for me going on a year later now. I’m sure others will say not to use the pole area and its wrong as was the case in my other posts on this back when I had the problem. I just know this works for me. Solved the problems I was having with PS. Nothing else did.

Can’t hurt to try it. If you find an alternative solution by all means come back and let everyone know. Might be useful for someone else down the line.



You don’t mention what camera you are using but 30 seconds seems like a long time for a plate solve image and there might in fact be too many stars and or noise for the program to come up with a resolution.

Usually when I see PS2 having issues it boils down to one of two things. Either poor ‘hint’ information (most common) or a bad image, washed out, way out of focus,

I am using an ATiK383L+ with a lum filter binned at 2x2 and shoot 8 second frames and am amazed at how plate solve 2 can still resolve images that are out of focus, or with star trails, and satellite trails.

Here is an example of a frame that actually has a successful resolution!

crash by Tom Whit, on Flickr


Thank you for replying. I am using a QSI 660 which has very little noise. I don’t think there are too many stars and usually PS2 solves immediately. I actually think the problem may be when it fails that there are too few stars. One of the steps in the plate solving process is to estimate the background which is then subtracted from the image. If the sky background is too bright, I speculate that PS2 is not detecting enough stars to solve.

As to poor hint information, I am not supplying any. That is entirely under SGP’s control. Whatever SGP passes to PS2 during auto centering is what PS2 gets.

I agree, PS2 usually works amazingly well. That is why I was puzzled at its failure a few nights ago. It just would not solve hardly at all. Last night it worked flawlessly. If too light a sky background is indeed the problem, I have no control over that either, but I hoped that perhaps there were PS2 parameters I could adjust in that case to enable better operation. However, I have no idea what to change or by how much so I just leave them set at their default values.

Thanks again.



There is no need for a ton of stars, i’ve set it up to do 1sec @ bin3x3 and i can’t remember it ever having a problem solving an image even if it’s out of focus or if it’s a little cloudy with very few stars.

Earlier i have tried longer exposures thou and it caused fails once in a while so i’d say start with 1 sec binned and see how that works out for you.


i think PS2 may fail when presented with too many stars - and somewhat randomly… earlier in the year i was working on the eastern veil nebula and maybe 50% of the time PS2 would fail (depending on the exact pointing.) i never have failures in less busy parts of the sky…