New 314L+ Is this a normal amount of bad/hot pixels?

[Sp@ce_d]

Does this look "normal"?

My first chance last night to try out the new CCD & I've just done a quick stack of 10x600 Ha subs. No darks,flats. I'm rather surprised to see this many bad or hot? pixels showing up.. I gave up counting around 60! I know I can do darks but having read so much about this chip not needing darks I'm wondering if this normal? The cooling was set to -10c

(wasn't an ideal night for imaging..Typically, having had my new 314L+ for a couple of weeks, last night was the first chance to test it out properly & it just had to be a full moon..)

[Sp@ce_d]

I know there's also been issues with power & cabling so thought I should also add I'm using one of these for power http://www.maplin.co...r-supply-509268 & using the supplied cables. I haven't added them to the wiring looms yet either so they're well separated.

[jnc71106]

what method did you use when you stacked the frames ? sum, average, median etc ?

they look like hot pixels that have trails because PA and guiding wasn't spot on. they are going the same direction as your star trails as well

try stacking with a median filter as that will remove them

[Gina]

Yes, I think that's the problem. I have dozens of hot pixels with my DSLRs but a small percentage of the total pixels and it's not a problem. Of course, I use darks which aren't supposed to be needed with an Atik 324L+.

[Sp@ce_d]

I used Nebulosity & average. I know I can get rid of them but as this is a new CCD I wanted to see any defects so I didn't bother too much with aligning the target etc. I'm just a bit surprised how many are showing up. I'm used to working with the DSLR so wondering if this is normal at this temperature (-10c) for this chip. What is the optimal operating temp anyway?

Any other 314L+ owners that I can compare with?

[swag72]

I've never used darks with my 314L+ - I would agree that by changing your stacking process they will disappear. I use SD for stacking.

[jnc71106]

from memory i also stacked some frames with average when i first got my 314 and it looked pretty much the same as yours does. that is why i don't use average when stacking. either median or sd for me

[Sp@ce_d]

Ok so it sounds as though this amount of hot pixels are not out of the ordinary then. Being new to cooled imaging I wasn't sure how many to expect, especially at -10c. How do you work out what the optimal operating temp should be before things freeze up?

[Spikey]

Agree with all of the above regarding stacking, these are stacking artefacts - mine does exactly the same; try a median stack and check the results.

[Gina]

Are you using DSS for stacking?

[jnc71106]

no idea what optimal is but i try and gey it as close to -20 as i can. it obviously depends on outside temps as to how close it can get

[Sp@ce_d]

Are you using DSS for stacking?

I normally use Nebulosity these days.. used it for this one. I'll try it with a better algorithm tonight to make sure they do disappear.

no idea what optimal is but i try and gey it as close to -20 as i can. it obviously depends on outside temps as to how close it can get

I'll give that a go see how much difference there is below -10 then.. shouldn't be a problem at the moment as it's been below 0 past couple of nights..

[Sp@ce_d]

Couple of darks at -10c & -20c

[Gina]

That seems a lot of hot pixels

[Sp@ce_d]

That seems a lot of hot pixels

Exactly why I was asking the original question.. It surprised me. For comparison as I've got my DSLR and the Atik rigged up on a dual bar config at the moment, I've just done a couple of 5 mins on the 314 without the cooler on & the 1000D. The temp on the 314 was at 6.4c when I started and rose to 7c by the end of the exposure.

[swag72]

If you go back to the original lot of subs and restack them using Median or SD, does the problem disappear? If it does, then surely it's not a problem really. I've never bothered to fire up any of my CCD's to look at the not pixels. If they were showing on a stacked sub then perhaps I'd take a peek, but until then, I am blissful in my ignorance. If you look closely enough you will always find too much of this and that. Then I have found that can lead to an almost manic paranoia that becomes impossible to shake.

Restack, see the difference and if you don't see them, then forget about them!

[martin_h]

A few pixels out of a few million is not bad at all, even if it was 1000 pixels it still wouldn't be bad, with the right stacking method. I use the KAF8300 chip and have a snowstorm of pixels, which all dissapear with a bad pixel map and sigma stack

[Sp@ce_d]

If you look closely enough you will always find too much of this and that. Then I have found that can lead to an almost manic paranoia that becomes impossible to shake.

... Sshh.... they're watching....

Errr yes Sara.. Think I am starting to drift down that path... well spotted.. expecting perfection to be a bit easier to achieve.. I guess it's a different ball game compared to using the DSLR

A few pixels out of a few million is not bad at all, even if it was 1000 pixels it still wouldn't be bad, with the right stacking method. I use the KAF8300 chip and have a snowstorm of pixels, which all dissapear with a bad pixel map and sigma stack

Yeah I'm realising I'm going through the learning curve again now I've moved onto CCD. Took me a bit by surprise to see them having used the same stacking routine as I do with the DSLR & never had that problem. I'll try the bad pixel map in Neb

[Sp@ce_d]

And yes they will stack out.... used the STD Dev Filter (1.25)

Ok.. moving on.. thanks for putting my mind at rest...

[ollypenrice]

I'd say it was OK. If you have at least ten subs in the stack then use a Sigma routine which will identify outliers and attribute to them the average value of their neighbours. Also use a hot pixel filter. Once you find the right stacking algorithm you'll be laughing.

Olly