5200 Heavy Index files

[Grant Privett]

Hi there,

A few years ago I grabbed the 5200 Heavy series of Index files to provide my default electro-optical Index files.

At that time I think the advice was to use those plus the 4100 series to fill in some gaps.

I today noticed that the 5200 series is now larger. Does that mean I can now drop the 4100 series entirely and just download the extra 5200s? 

Thanks.

[Dustin Lang]

Hi,

That advice is the same.

The 5200 series only goes to "scale 6"; for larger angular scales you want the 4100 series.

The extra files in the 5200 series are "52m1", which are "scale -1" -- containing quadrangles 1.4 to 2 arcmin on a side.  Very few people will need these, and the files are huge.  They're useful for JWST images, eg.

cheers,

dustin

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[Grant Privett]

Is there a list of the scales for each ie what scale is 5200, 5201 etc. I realise I only had 4107 -4119 and also 5204-5206

It might explain why a dataset that is a smaller FOV than usual is not solving with my code but works fine on your website.

[Dustin Lang]

Yeah, there's a table here,

https://astrometry.net/doc/readme.html#getting-index-files

That lists the size of the quadrangles in the index files; I think ideally that's 1/3 to 1/2 the size of your image.  For example, scale=2 works great for SDSS 13' x 9' images.

cheers,

dustin

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[Grant Privett]

I have added the 5203 series to my index files, but am still having trouble with one image series taken with an f/11 14" SCT. FOV is only 9x7.5 arc mins.

Its an image of an area of dark nebulosity with >100 stars mainly round the outside edges of the image.

Presumably, I need to download the 5202 series as well. Ah well, may come in handy some time...

[Dustin Lang]

In the web version, if you look at the log files (the link is on the first submission status page), at the end it should tell you which index file the solution was found in.  This can be useful for reproducing the web results.

cheers,

dustin

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