Hello Patrick,

the following is the information I get when clicking on More Info for
4f00048d.fit = imgda079.idx (the latter is an ASCII file, but I don't know what
the values are [maybe starting with RA and Decl in degrees]:

SIMPLE = T /FITS header
BITPIX = 16 /No.Bits per pixel
NAXIS = 2 /No.dimensions
NAXIS1 = 469 /Length X axis
NAXIS2 = 469 /Length Y axis
COMMENT Decompressed w/HDECOMP at Mon Aug 18 10:27:27 2014
COMMENT HDECOMP version Feb 16 2008 11:55:23
DATAMIN = -31711 /Minimum data value
DATAMAX = -16277 /Maximum data value
CONTRAS0= -31711 -29830 -29716 -29640 -29581 -29532 -29487 -29446 -29407 -29371
CONTRAS1= -29339 -29308 -29277 -29248 -29220 -29194 -29168 -29142 -29118 -29092
CONTRAS2= -29069 -29045 -29022 -28998 -28975 -28954 -28930 -28906 -28882 -28859
CONTRAS3= -28836 -28812 -28788 -28764 -28740 -28714 -28689 -28661 -28633 -28607
CONTRAS4= -28577 -28551 -28521 -28491 -28460 -28429 -28396 -28364 -28327 -28292
CONTRAS5= -28256 -28217 -28179 -28138 -28100 -28060 -28015 -27973 -27929 -27881
CONTRAS6= -27830 -27782 -27731 -27674 -27617 -27554 -27489 -27422 -27351 -27278
CONTRAS7= -27198 -27111 -27025 -26929 -26827 -26723 -26606 -26482 -26349 -26211
CONTRAS8= -26060 -25889 -25708 -25515 -25317 -25092 -24850 -24579 -24288 -23963
CONTRAS9= -23606 -23193 -22741 -22247 -21693 -21055 -20384 -19650 -18878 -18079
END

The values for DATAMIN and DATAMAX looks strange, they seem to be shifted by 2^16
= 65536 to the negative.


The header of nearby image of NGC 6756 looks like this:

SIMPLE = T /FITS header
BITPIX = 16 /No.Bits per pixel
NAXIS = 2 /No.dimensions
NAXIS1 = 352 /Length X axis
NAXIS2 = 352 /Length Y axis
COMMENT Decompressed w/HDECOMP at Mon Aug 18 10:27:27 2014
COMMENT HDECOMP version Feb 16 2008 11:55:23
DATAMIN = 2473 /Minimum data value
DATAMAX = 15986 /Maximum data value
CONTRAS0= 2473 3331 3418 3479 3522 3557 3584 3611 3638 3659
CONTRAS1= 3682 3702 3724 3743 3759 3778 3794 3813 3831 3848
CONTRAS2= 3863 3879 3896 3912 3928 3946 3962 3978 3994 4011
CONTRAS3= 4027 4043 4061 4078 4096 4112 4130 4150 4167 4187
CONTRAS4= 4207 4228 4249 4270 4290 4312 4333 4355 4379 4406
CONTRAS5= 4433 4459 4488 4514 4544 4575 4606 4637 4668 4706
CONTRAS6= 4740 4778 4817 4856 4902 4947 4990 5040 5091 5146
CONTRAS7= 5203 5262 5324 5394 5466 5540 5625 5709 5815 5919
CONTRAS8= 6041 6167 6302 6454 6629 6815 7033 7255 7530 7816
CONTRAS9= 8151 8541 9013 9544 10120 10839 11612 12536 13540 14520
END

I don't know if and where it is possible to set the DATAMIN and DATAMAX values
for a single image.

> Hi Bernd,
> I *could* turn off all images, but that's not what I want to do. I can also
> make the white square go away by inverting all images (because then it becomes a
> black square!), but then all my other images are inverted, too.
>
> What puzzles me is why I can't delete the white square - I can delete any DSS
> image, but this damned thing can't even be deleted in its folder - it's
> indestructible!

Perhaps because it is listed in the file "imgcache.dat" in Guide's home folder.

> It's obviously not a serious issue, I don't spend all day looking at NGC 6755.
> It's just a strange thing.

Clear skies
Bernd

Bernd Klemt

Sternwarte Herne, MPC code A18
Herne, Germany

e-mail: info@...
http://www.sternwarte-herne.de