What went wrong???

[Lee]

Thought analysing a dud image (or at least one sub) might help some people out.... I've always found learning from disasters quite effective.....

This is a 5 minute sub at the Helix in Ha taken last night. 100mm f/5 achromat scope, DSI Pro II, guided by PHD on G-11. Outback cooler at 18degC. Dark subtracted only processing - only slight stretching to show the problem.
The dark subtracted .fit for the really interested. (http://www.betweentheclouds.com/pics/pproc_Helix-Ha-5min-sub-1_003.fit)

Can anyone suggest what is going on, what's going very wrong in this??? I eventually worked it out, then went to bed early!

[[1ponders]]

Is it fogging on the chip from the cooler?

[citivolus]

Hmm, you left a Hartmann mask on the scope?
(Been there, done that!)

Cloud moved in front 30 seconds in?

[leon]

There seems to be some of the same at the left of the images as well, could there have been some electrical interference, just a thought.

leon

[turbo_pascale]

I vote for fogging, although you could have been shooting through trees.

Turbo

[Lee]

OK - the foggers have it - the right hand side of the frame was fogged (with an angular section on the left end clear) when I pulled the camera off. The left looks so white from the histogram stretching to bring helix out of the fog I believe.

Topped off a crap night really, with average guiding as well....

I initially thought it must have been a light leak around the silly filter holder on the DSI. I have usually checked the chip for fogging by looking down the objective with a torch - but the Ha filter is a tad hard to see through!

Seriously though - people - post your duds too - there is a lot to be learnt from others' wasted hours!

[turbo_pascale]

You want to see real serious (and obvious) fogging....
Try this sequence from my ST7 from a few nights back while I was starting a set of flats.
Images were about 30 seconds apart, at -10C.
Decided to call it a night as the clouds rolled in shortly thereafter anyway.

Will be baking the desiccant shortly!

Turbo

[[1ponders]]

Then there is always this thread.
http://www.iceinspace.com.au/forum/showthread.php?t=24960

with this animation of fogging http://www.iceinspace.com.au/forum/attachment.php?attachmentid=33386&d=1192838628

:rolleyes: Dem ST7 can get frustrating at time, turbo. ;)