What has happened to my lens?

[loki78]

The past 2 nights in a row, trying to shoot the milky way in the exact same way i have done in the past with no problems, using all the same gear, eos 600d, 10-22mm lens at 10mm F4.5 and ISO 3200 35sec subs.. Ive used this many times to good effect, but last night and tonight something has gone awry.

Now after stacking in DSS (without any processing as its hardly worth it) im getting massive coma? Are those single subs (1 included) bad enough to do that?. I thought it was a one off so i went back tonight and replicated it and had the same problem. I'm not sure what has gone wrong between in the past and now, or if I am forgetting something.

[bartman]

Hi Jon,
I can only think that the settings in DSS have changed since last time you used it to make the 'good picture'
I had a similar prob a while back ( n
I believe DSS remembers the last settings you have made ( from a previous run). You might have accidentally 'saved' those settings and DSS is using those settings.
So you might have to review the settings in DSS.......
Sorry thats all I have
Bartman

[bartman]

Or maybe its the tip of the tree/branch in the bottom right that DSS is focusing on as a reference point?
I might be wrong ....just a thought
Bartman

[jjjnettie]

Wow. I've not seen that before.
I would remove that version of DSS from your computer completely, as well as the set up files, then download a fresh copy.
Let us know if that fixes the problem.

[loki78]

Thanks guys, I have had foreground trees before so I don't think that's the problem. I completely reinstalled and was having the same problem so i started experienting with settings.

I have always altered my star detection threshold to get around 50 stars in the past (as this has always worked for me and a few guides/tutorials pointed me in this direction)

But I dropped it low and it was 500+ stars this time with a much better result.

I'm not sure why this is the case this time *shrug*

What sort of settings do you guys routinely use with DSS?

[LAW]

It looks to me like detail is preserved in areas where there is less field rotation or less data (the centre, east/west ecliptic and the edges with less stacked frames). This leads me to believe that DSS is overcompensating for field rotation (presuming you're using an Alt-Az mount?)

Depending on how many frames you stacked I'd try doing them in batches of 5. I've only used DSS a few times so I can't remember if there's a specific setting for field rotation compensation?

[loki78]

No these are just off a tripod, it's how I usually do it. It was 25 frames stacked. 25 X 35sec frames.

[Poita]

Have you checked your exif data to make sure the settings were actually the same as before?

[loki78]

I haven't and have no idea how :D

I have heard of exif data, that's about it I'm afraid

[silv]

you probably googled EXIF by now. ?
DSS shows some of it in the file list once it has inspected the images.
ISO, f/x and and exposure time is what is interesting and whether these values are the same compared to the photos that lead to good DSS results.
(if you have other photo editing software you can look up ISO, f/x and exposure time in the photo properties, too)

would you upload one of your good DSS results for us?

[silv]

DSS has a setting: "use x% of the best". try setting that to 80% which is the default.
The stacking mode: try setting it to Mosaic.
Did you use flats and darks? If so, try a stack without them.

:)