For a wide field (~20 deg), I tried a local Astrometry.net (ansvr) in ASTAP using the Tycho-2 catalogue .fits index at
In short, my recommendations for improving ASTAP are:
- fix the reading of star catalogues (from .zip, .rar, etc.)
- include smaller star catalogues for faster solving of wide fields (HIP, Tycho-2, SAO, BD/CD, etc.)
- fix and include the HN_FITS tool (to provide a very good hint for ASTAP)
- implement WCS tools (for blind solve of images not from a digital mount)
Other possible recommendations for improving ASTAP:
The solved .fits files in ASTAP cannot be read in another plate solver such as Astrometry.net, and vice versa.
When a .fits file solved on Astrometry.net is opened in ASTAP, for instance, all I see is a white screen (the
DSO annotations are visible but the image is not).
ASTAP has a dedicated Gaia dr2 (the latest) star database up to magnitude 17 (or 16 or 18 mag versions are also provided). This database is sorted from bright to faint so can easily provide the brightest stars of a 20 degrees section of the sky. It is also ultra compact stored. So an other database is not required. ASTAP can't read any other star database format as indicated.
The solving of large fields will be problematic by optical distortions, not due to the used database. ASTAP assumes a perfect telescope and projection. Also due to the optical laws, stars in the outer regions image will be oval/comet like. ASTAP has successfully solved fields up to 4 degrees. You can play a little with the tolerance (<=0.007) and numbers of stars (50-1000) used but it will most likely fail for fields above 4 degrees.
I considered using only the center of the image for solving wide fields. As long it contains 50 stars, the center solution could be used to extrapolate the solution for the whole image. I haven't worked out this idea since wide fields are normally not considered "lost in space" but probably it is still nice to have an astrometric solution to identify object.
I could try to add this large field solving. Could you provide some 20 degrees image samples to work on?
The HNS_FITS tool is no longer developed. To solve JPEG/TIFF/PNG images, just enter the approximate image center in the ASTAP viewer. The field size of the image can be set in the ∑ menu, tab alignment. The JPEG, TIFF, PNG image will solve fine as long the image is not heavily photo-shopped and not too much saturated. To identify bright stars from faint star, they should have a lower intensity in the image. ASTAP is most happy with raw unsaturated images, sharp in focus. As long star intensity is maintained it will solve either a noisy single 10 seconds exposure or 100 images stacked of 300 seconds each. So as long the the telescope was focused, good tracking was maintained, star intensity preserved and the image scale <=4 degrees it will work fine. For image larger then 3000 pixels wide use the binning option.
>> The solved .fits files in ASTAP cannot be read in another plate solver such as Astrometry.net, and vice versa.
I haven't found a solution for this but you could bypass this by adding the option "--no-verify" to the Astrometry.net call. This option is given in the ASTAP menu for calling Astrometry.net as an external solver.
>> When a .fits file solved on Astrometry.net is opened in ASTAP, for instance, all I see is a white screen (the DSO annotations are visible but the image is not).
Maybe the viewer data range is in manual. Set in the viewer the data range to low or medium or bright.
>> Also, there should be a way of changing the number of DSO's displayed. (Maybe include different levels of the database on the pages of the DSO spreadsheet. For instance, if the observer displays Page 3 on
the spreadsheet then annotations from that page are displayed on the image.)
At the moment is is fixed at 30.000 objects in a simple .CSV file. For a 20 degrees image this will be overcrowded with deepsky objects. Yes probably it is better to limit automatic on DSO size once a 20 degrees image can be solved. Again give me some 20 degrees sample images and I will have a look. Feedback helps to develop this program further.