Doh, forgot to turn the cooler on!

[kirkster501]

Just got 4 x 5 min 1x1 red lights.  Good job i spotted it early!  Just turned the cooler on.

Would you throw the 20mins of data thus far collected?

[nmoushon]

Its only 20min so I would probably just toss it. But thats just me. Would be one thing if it was half the night or a whole night.

[kirkster501]

Yep, agree mate.  Deleted!

Just sanity checking.  Would have been peeved had this been three hours in and I noticed....

[Davey-T]

Did this with a bunch of subs, did a bunch of calibration frames specially for them , then scrapped the lot

Dave

[swag72]

I have done this a number of times and on whole night runs - It all got binned!!

[RobH]

Did the very same last night.......40 x 8 minute and 7x 15 minutes, all with the cooler off. Fortunately Maxim records the sensor temperature so the camera is now on an all nighter shooting darks for them !

[sloz1664]

Yep we've all done it mate. Did you have a look at them, as you don't need

darks with your 460 and the air temp quite low they may have been acceptable.

cheers

Steve

[RobH]

You do need darks with a 460 Steve, they're pretty quiet cameras but there is noise.....I use a 460 also.

You especially need them if you're using an OAG so there's no image shift between subs, thus not allowing outlier reject stacking algorithms to remove any noise. I could parhaps get away without them for the 8 minute luminance subs but not 15 minute Ha ones, but it's much better to use them (as long as you take enough)

[sloz1664]

Hi Rob,

Does that mean I should use darks with my SXV H9 & QHY8 pro?

I usually capture 10 min Lum & 10/15 min Ha.

cheers

Steve

[kirkster501]

I am coming round to the idea of using darks as well.  There is background noise I think on my subs.  I am going to compile a darks library at my used exposure times and CCD temperatures of -20C in winter and -12C in summer.  As long as I run off a new set every three months or so I should be good to go I think.

Do darks need to be binned as well? 

[RobH]

Hi Steve. It all depends on how much noise you're getting and if there's any movement between subs. I have an Atkins 16hr, which I've always shot darks for. this has the same sensor as the H9. Although you hear that this sensor, and the one in the 460EX ,are so quiet that you don't need darks, in practice, unless you are using dithered guiding, the will always be some noise you can remove with darks. You must make sure you have plenty though or you'll add noise. I shoot at least 30. Do 2 identical stacks, one with darks and one without, and see if there's any difference.

[ollypenrice]

I've moved away from darks to bias and bad pixel map. I find this less invasive than dark subtraction, which gave a less consitent result. My camera is the 'noisy' Atik 11000 but, calibrated this way, I don't find it noisy at all.

Be my guest: a linear stack of 7x30 min luminance calibrated this way; https://dl.dropboxusercontent.com/u/63721631/M31%207X1800%20L.tif

I've made bad pixel maps from darks of 10 and 15 minutes but I now use them on anything. It really doesn't seem to matter. Quite relaxing! I stack in AstroArt 5 and put a master bias in the box intended for darks while the bad pixel map has its own box.

Olly

[kirkster501]

Thankyou guys.  I shall do some experimenting and i will report my findings.

@Rob.  I do use dithering.

[RobH]

Sounds really interesting Olly.....never thought of using darks to provide bad pixel maps....I'll give it a go :-)

[sloz1664]

Steve,

I use dithering when imaging with one ccd but cannot

dither when I use both my cameras. So it looks like

dark subtraction or bias/bad pixel map, as Olly suggests,

which I can compile from MaximDL.

cheers

Steve