I No success with ASTAP . .

Just tried ASTAP in SGP v.451 last night. I get a fail with the notation to the effect “warning too small image” or something like that? I am imaging at 4.86 a-s/px with a FOV of approx. 5.4x3.6 degrees.

Here’s a screenshot my directory for the ASTAP catalog . . .

It’s as if, I need additional catalogs or something? If so, are they available?
My PS2 and failover astrometry.net are both fine. I was just curious to try ASTAP.

The warning is indicating that ASTAP works better with a higher resolution image. It can still solve the image but if possible reduce binning. The recommended resolution is something like 1500x1000 pixels or more. At what resolution are you working?

The G17 catalog is fine. It goes up to magnitude 17 and will work up to very long focal lengths. More then adequate for your large field/short focal length.


Thank-you, Han. I have been using PS 2 with plate solving images binned 3X3 for several years.
next time out, I will try ASTAP again, but with binning 2X2. The window closes too quickly for me to get a screenshot, but ASTAP failed to solve the image. Astrometry.net, as the designated failover quickly kicked in and solved successfully.

The reason as said is most likely binning, one thing to note is that there’s binning of the plate solve images in SGP, but ASTAP also has a setting to downscale the image, both these options together can create a tiny image that you can’t be plate solved, there’s info about this setting in the ASTAP documentation.

Terry, usually there is no need to wait until “next time out”. You can set up the plate solvers (PS2, ASTAP, ANSRV) and test them during daylight hours by loading FITs test images into SGP, right-click on the displayed image, and choose “plate solve”. This way you won’t be wasting any precious imaging time, and you can test the robustness of the solvers with a wider selection of images.

Yes as indicated you can experiment with local files. Note that ASTAP is most happy with resolutions something like 3000x2000 pixels so depending on your camera there is no binning required.

ASTAP checklist for solving:

  • at least 30 stars are visible
  • reasonable round stars
  • image size at least 1.5 megapixels
  • correct pixel scale (arcsec/pixel)


Thanks Xplode, Ross and Han.
But . . . .

As suggested, I just tried solving without being connected. But all my images are binned 1x1! During a session, all plate solves are done at 3x3.

Here’s what happens when I attempt to solve a FITS sub taken on a previous session. . .

1/ Open the unbinned fits in SGP.
2/ Solve with my usual PS2 settings, i.e. binned 3X3 and “max regions:” PS2 goes off on a wild goose chase and fails. Keep in mind PS2 works fine with these settings when actually imaging. Has for years! But it won’t solve an unbinned image loaded into SGP?
3/ Same unbinned fits file, same settings, i.e., binned 3x3 and “max regions.” ASTAP solves all but instantly. But it would not work with these settings when actually acquiring a binned image during a session.

It occurs to me that the difference is that the FITS I am trying to solve is NOT a binned image! My plate solve images are binned but my “real” subs are unbinned.

Camera is an STL, 4008x2672 px.

So, I remain puzzled.
ASTAP will not solve at 3x3 binning when acquiring binned images during a session. But it solves unbinned subs taken during that session all but instantly.

PS2 solves during a session during a “slew and center” operation but fails when used on an unbinned sub acquired during that session? It fails irregardless of the binning setting. Changing to 1x1 has no effect. Of course the actual image is 1x1.
I have no 3x3 binned images on disk to experiment with as I only bin for reasons of focusing and plate solving and none of those images are retained.

So, back to having to wait for another imaging session and trying ASTAP at other than 3x3. If I have to shoot unbinned, I may well have to increase exposure time on plate solve images and thereby lose any speed advantage ASTAP may have over PS2.

Here’s the setting most likely causing you trouble, if it’s set to downsample 2 and you’re already binning 3x3 it will be like you binned 6x6…a tiny image

Thanks, Xplode. My setting for “Downsample” is the default value of 0.

Set it to 1, that way you force it to not downsample.
I would also suggest bin2 for binning in SGP since you’re imaging at such a low resolution

Leave the binning in ASTAP at 0. This is mode automatic and will select then 1x1. Set it in SGP at 1x1 or 2x2. For DSLR, OSC cameras it is normally better to bin 2x2 but I don’t know your native resolution. Just keep the final binning result above 1500x1000 pixels.



Thanks, Han. I will see how it goes next time out.

“Next time out” has just occurred. :slight_smile:
ASTAP solved successfully on my images when I reduced binning from 3x3 to 2x2.
Of course, my camera is notoriously slow to download. An SBIG STL11002.
PS 2 will solve at 3X3 binning.

While the 3X3 binned images download considerably faster than the ones binned 2X2, ASTAP still beat PS2 for speed. PS2 binned 3X3, took 33.4s. ASTAP binned 2X2, took 23.7s. My plate solve images for LRGB filters are of 5 s duration.
So, I’m going to stay on ASTAP for a while.

Thank-you all for the help.