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Astrotortilla faux par

Nathan_Pembs

By Nathan_Pembs
in Discussions - Software

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Gib007

Gib007

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Really cool advice about moving the "unused" index files out of the way, Louise. Mind if I link back here and credit you for the idea in an update to my tutorial?

I've bookmarked this thread in anticipation of your reply. 

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Thalestris24

Thalestris24

Posted
Posted

Really cool advice about moving the "unused" index files out of the way, Louise. Mind if I link back here and credit you for the idea in an update to my tutorial?

I've bookmarked this thread in anticipation of your reply. 

Hi - no need to credit me!! I'm only a beginner myself and I've learnt stuff from other help guides such as:

http://stuffupthere.com/Astrophotography/Articles/astrotortilla.htm (the tip about using only 2-3 index files is from here)

And of course, the light vortex tutorial:

http://lightvortexastronomy.blogspot.co.uk/2013/08/tutorial-imaging-setting-up-and-using.html

Also, the AT forum, and various other places

Oh there's an AT guide on youtube too:

https://www.youtube.com/watch?v=2_2jKHHxAjI (but poor sound quality!)

Cheers

Louise

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Thalestris24

Thalestris24

Posted
Posted

Thanks Louise. I'm the author of the Light Vortex Astronomy tutorial. I'll definitely add you and your link as credit for the tip once I update the tutorial! :)

Ah - I had a feeling! The tip came from the 'stuffupthere' link above - so they deserve the credit!

Edit:

"Pay attention to the logs after the first few solves. At will tell you which index it used to solve your frame. You'll discover that it's always the same 2-3 indexes, since your FOV remains consistent. Eventually, once you're comfortable knowing which indexes keep getting used, you can move the other index files out of their folder to another location. This, combined with the parameter discussed above, will let you give AT **just** the index files it will need, and place them wherever you wish (perhaps even on a thumb drive) for best performance. "

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PhotoGav

PhotoGav

Posted
Posted

I have a feeling that I'm being a bit of a numpty here, but I can't for the life of me find the index files on my computer! Please help... Where will they be? I have "C:cygwin" and then 10 folders in there, including another cygwin folder. I've looked everywhere in there, but to no avail....

Thanks in advance!

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Gib007

Gib007

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Posted

Ah - I had a feeling! The tip came from the 'stuffupthere' link above - so they deserve the credit!

Edit:

"Pay attention to the logs after the first few solves. At will tell you which index it used to solve your frame. You'll discover that it's always the same 2-3 indexes, since your FOV remains consistent. Eventually, once you're comfortable knowing which indexes keep getting used, you can move the other index files out of their folder to another location. This, combined with the parameter discussed above, will let you give AT **just** the index files it will need, and place them wherever you wish (perhaps even on a thumb drive) for best performance. "

You're very honest, thank you. I will do that. I've been meaning to improve some parameters on my tutorial and this technique of moving index files out of the way sounds like an excellent one to speed things up (that being the main purpose of my tutorial). 

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Thalestris24

Thalestris24

Posted
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I have a feeling that I'm being a bit of a numpty here, but I can't for the life of me find the index files on my computer! Please help... Where will they be? I have "C:cygwin" and then 10 folders in there, including another cygwin folder. I've looked everywhere in there, but to no avail....

Thanks in advance!

From my earlier post:

Assuming you have AT and Cygwin installed on your C: drive, the index files are stored in: Cygwin\usr\share\astrometry\data\

Hth

Louise

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Steve 1962

Steve 1962

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Ray - AT works without having a mount connected. It just takes longer because it searches the whole sky rather than the search area around your scope position.

If it doesn't solve - have a play with downscaling setting, I use the default for binned images and 4 or 8 for unpinned.

Steve

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Thalestris24

Thalestris24

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Hope this is not a silly question!! can you use the astrotortilla simulator to find out what index its using for a plate solve?

Ray

Hi Ray

Yes you can use the eqmod simulator and run Tools -> Goto image in AT. If you keep the Tools -> log viewer open you'll see which index file it's used for that image :)

(It has to be an image that it can solve - i.e. one from a previous session. It should take maybe 10s to solve if you already have isolated the needed index files - probably a bit longer otherwise.

Hth

Louise

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Thalestris24

Thalestris24

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Hi again

Used AT more successfully than usual last night :) I took some of my own medicine and monitored the log file... :angel: This was quite interesting. In the end I found it used index numbers 4209-4211.

I previously didn't have 4209 in my data folder. I wondered why it was failing to solve sometimes - now I know! D'oh. Moved 4209 in and it was fine :) Solve times were between 4.2s and 10s with most less than 5s. I use binned 2 x 2 images for AT. The log file returns the pixel scale as 4.22474". This corresponds to a fov 1.83 x 1.19 deg which is slightly smaller than I thought it should be. My only explanation is that my actual focal length is ~760mm rather than the nominal 750mm (which gives a fov of 1.85 x 1.21 deg). The log file also returns 'field sizes' which vary and are not quite the same as the calculated fov.

Anyway, just thought I'd post my experiences in case it helps someone.

Cheers

Louise

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Gib007

Gib007

Posted
Posted

Hi again

Used AT more successfully than usual last night :) I took some of my own medicine and monitored the log file... :angel: This was quite interesting. In the end I found it used index numbers 4209-4211.

I previously didn't have 4209 in my data folder. I wondered why it was failing to solve sometimes - now I know! D'oh. Moved 4209 in and it was fine :) Solve times were between 4.2s and 10s with most less than 5s. I use binned 2 x 2 images for AT. The log file returns the pixel scale as 4.22474". This corresponds to a fov 1.83 x 1.19 deg which is slightly smaller than I thought it should be. My only explanation is that my actual focal length is ~760mm rather than the nominal 750mm (which gives a fov of 1.85 x 1.21 deg). The log file also returns 'field sizes' which vary and are not quite the same as the calculated fov.

Anyway, just thought I'd post my experiences in case it helps someone.

Cheers

Louise

Good to hear, Louise. I will have a play with this myself soon enough. 

Regarding your focal length, you can have it measured directly. Upload a raw FITS image to nova.astrometry.net and once it plate solves, go to the results page. Under Calibration, look at Pixel Scale. You can then use the following equation to calculate the exact focal length:

[Focal Length in mm] = (206.2648 x [CCD Camera Pixel Size in um]) / [image Pixel Scale in arcseconds per pixel]

For example, I uploaded an image of mine taken with a Borg 77EDII and an ATIK 383L+. The Borg 77EDII is advertised as having a focal length of 355mm and the pixel size of the ATIK 383L+ is 5.4um. The pixel scale on the plate solved image was 3.03 arcseconds per pixel. Working with the equation, I got a measured focal length of 367.6mm. Good to know if doing mosaics and for setting up things like AstroTortilla. 

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Thalestris24

Thalestris24

Posted
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Good to hear, Louise. I will have a play with this myself soon enough. 

Regarding your focal length, you can have it measured directly. Upload a raw FITS image to nova.astrometry.net and once it plate solves, go to the results page. Under Calibration, look at Pixel Scale. You can then use the following equation to calculate the exact focal length:

[Focal Length in mm] = (206.2648 x [CCD Camera Pixel Size in um]) / [image Pixel Scale in arcseconds per pixel]

For example, I uploaded an image of mine taken with a Borg 77EDII and an ATIK 383L+. The Borg 77EDII is advertised as having a focal length of 355mm and the pixel size of the ATIK 383L+ is 5.4um. The pixel scale on the plate solved image was 3.03 arcseconds per pixel. Working with the equation, I got a measured focal length of 367.6mm. Good to know if doing mosaics and for setting up things like AstroTortilla. 

Hi

I guess that's what AT did! It probably is a bit longer than the 750mm with a coma corrector + spacer ahead of the camera.

(206.2648 x 7.8 / 4.22474) x 2 = 761.646mm

:)

Cheers

Louise

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Gib007

Gib007

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Hi

Maybe the tutorial link should go on a sticky?

Oh, I noticed it still has August 2013 at the top....

Yup, these are essentially blog posts. The original version was written and published on 27th August 2013. The page link is still the same though and my Tutorials page has a "Last Updated" date stamp on it. 

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