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Warning...nasty trick Maxim can play!

RobH

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RobH

RobH

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Hello folks.

Don't do what I just did.....

If you use Maxim, and use the 'batch save and convert' function to calibrate lots of files, make sure you don't try to calibrate any files that have already had calibration performed when you have the 'overwrite' box checked.

I had about 5 hours of data from a few nights ago, plus what I've taken tonight, and had forgotten that the earlier data was already calibrated.

When I ran it through, I got a box appear telling me that calibration couldn't be performed on these frames, with a choice...try again or quit.

I pressed quit and it dumped all the files that had previously been calibrated....not into the recycle bin or anywhere else on the computer....just gone :)

I know you have the choice to add a suffix, but I've not been doing this (although I will now!) as I didn't want to end up with double the amount of files.

Cheers

Rob

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RobH

RobH

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No...gone!

Did a really thorough search of course, but nothing.

It didn't ditch last nights data, but I had some half decent IC410 narrowband stuff and that all went.

Bad programming on Maxims part as there was no warning at all!

Cheers

Rob

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RobH

RobH

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No Daz, I was foolishly saving hard drive space by calibrating the original data....never again :)

On the bright side though, apparently, when something is erased on a computer, what actually happens is that the data is still on the hard drive, but the space used by it is allocxated as free space which can be overwritten.

Matt Garwood pointed me in the direction of a free tool for getting at this data so I will give it a go and let you know how I get on. (This is how PC worls etc can recover lost data for you, and how forensic searches are done on computes used in criminal activity).

Fingers crossed...there was some good narrowband IC410 data, and if I can get it back, I'd be quite happy ...if not, at least I've learned something about computers!

Cheers

Rob

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SteveP

SteveP

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That's bad news, Rob

Have you thought about posting your bad experience on the Yahoo MaximDL Tech group to warn others? Also, Doug George from Cyanogen is a regular contributor to the group and picks up on these issues for future upgardes

Steve

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RobH

RobH

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Hello chaps.

I downloaded a program and got the files, but I think that perhaps they are corrupted, or changed in some way, as they won't open, in either Maxim, or PS.

In PS (CS2) I get an error message saying theat the 'file format module cannot parse the file type'

At this point, my knowledge of the inticacies of computers stops :)

Cheers

Rob

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Tim

Tim

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What a shame. Sounds like they are corrupted as you say Rob. I wonder how badly. It is probably more effort than it is worth, but you may be able to repair them manually in a hex editor, i've never looked at a FITS or TIFF in one to see how they are put together.

If you like, send me a known good copy of a file as it should be saved, and one of the corrupted files, choose one with the nearest size in kb to the known good one, and i'll dust off my old software and take a look.

I bet you get a nice fov on the tadpoles as well with the tmb?

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michael.h.f.wilkinson

michael.h.f.wilkinson

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One problem with TIFF is that it may store the "header" (actually Image File Directory in TIFF parlance) anywhere. If the format is not recognized at all, the Image File Header if corrupt. In TIFF with should contain II or MM (ASCII) to indicate Intel or Motorola byte order. The next to bytes give a magic number (42 (cough)), and the next 4 the offset in the file to the first Image File Directory. This location contains the actual image header. Some programs store it right at the beginning, but in my own TIFF-write code the the IFH is at the end.

You could try to locate the image description data which is usually plain ASCII, but it is not in the IFH itself, unless it contains fewer than 4 characters.

Hope this helps a bit.

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RobH

RobH

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Hello all.

Firstly, a massive thanks to Lee, who has put his own valuable time into sorting out my problem for me….

Here, in his own words, is what he’s done….

What I did was create a logical evidence file with a forensic

application called EnCase (commercial and very expensive), I could

then look at the structure of the file without making changes. It

shows me a view of the file as its written and stored to disk, and I

then did a copy/unerase with it to pull the filw from the disk image.

That seemed to get the header straight. Sometimes running it through

email can do the same thing if its not too bad. Converting it to an

octet stream, emailing it, and then it being reassembled by the mail

client can do the same.

After then I opened it in Maxim DL 5, and saved it to a new location

to for maxim to write it out as a new file completely. I figured that

would ensure backward compatibility with earlier versions, and other

apps.

And.....

When you attach a file to email, it gets handled as an application/octet-stream (just a flavour of a binary file really), then by emailing it the TCP/IP stack within the Operating System chopped it up and sent it as individual packets, and it was then reassembled at the other end. Now in many cases this wont work to fix corruption issues with a file (especially in the body of data), but I reasoned that as this was a recovered / deleted file, it was likely to be a formatting problem with the header, and sometimes they will get re-ordered correctly when transmitting them over the network.

We got lucky, I looked at the FITS header with Maxim on a dark and bias frame I'd taken just over a week ago with my DSLR, and the structure looked slightly differently, but not knowing the format as intimately as I do with say JPEG and BMP (I've worked bad kiddie picture cases before, so you have to be very familiar with the 'real' header as they will often try stupid things like renaming the extension which doesn't actually change the header). I reasoned what I was seeing was really just a normal change of data in the header in the hexidecimal view in EnCase, so I tried to open the emailed file directly by Maxim 5 just now, it opened it first time without my interactions with EnCase so that just proved that the emailing actually resolved the issue, which must have been in the header. Data corruption would likely have never opened for us, or it would have opened and showed garbage in parts of the image.

I'vemailed the files to myself and they now work.....just need another 21 hours of data Tim :)

Cheers

Rob

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