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StargeezerTim

Iris Nebula again... tale of woes!

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I had a go at Iris again last night. It wasn't her fault it was my stubborness!

I still havn't managed to get usable flats or bias frames. This morning, my camera rotated slightly before taking them and the DSS output reflects that fact! So the pic is 6 * 10 min subs, with 4 darks. iso 3200, image is cropped. I used a UHC filter and I don't think it has really added to my last effort. I seem less able to bring out colour from this one than the last.

Anyway, god loves a trier!

post-35654-0-12252800-1432977757_thumb.j

I look in wonder at the detail people get from short subs with low ISO with similar gear. I doesn't help living near an airport but I do wonder if I am doing anything wrong! 

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I'm no expert myself, having only just got started with astronomy, but for what it's worth I'd be thrilled with that image myself. And I suspect from your location we live quite close, and I too feel the pain of the airport!

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Hey, that's very good - don't be tooooo critical! I've had a few goes at this target, and there is something elusive about it. My best results were obtained by stacking all my various subs from all sessions together. 

Couple of thoughts. Most Canon users seem to feel ISO 800 is preferred, and certainly that's what I've used for this. Also you need more subs - DSS seems to come into its own with 20 subs +.  Mayby try that - even if it means reducing each exp time. My best effort was with  - approx 20 *5 minute subs at ISO 800. Not saying that's the best way though!

Also you do need more darks - if you do, say, 20, DSS will keep a master dark which you can re-use. Most folk keep library darks for different ambient temps - but they dont seem to vary much by temp - at least not to my eye.

Bias - just got to click away with shortest shutter speed - shouldn't be any hassle. Again, DSS will keep master bias.

Flats - this will cause outrage, but I'm fussy about keeping optics spotless and so flats for me is just evening the light distribution, rather than getting rid of dust bunnies. I use a library flat if I don't have time to do per session flats. Only had a problem once with this method. If your camera uses vibration cleaning its likely your bunnies may shift (ooo-eer missus) between closing down and doing flats next day. 

Good luck!

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I'm no expert myself, having only just got started with astronomy, but for what it's worth I'd be thrilled with that image myself. And I suspect from your location we live quite close, and I too feel the pain of the airport!

I'm in Stortford, good to know there is at least one stargazer in Harlow! As far as I know, there are no other 'locals', we could be it!

Tim. 

Hey, that's very good - don't be tooooo critical! I've had a few goes at this target, and there is something elusive about it. My best results were obtained by stacking all my various subs from all sessions together. 

Couple of thoughts. Most Canon users seem to feel ISO 800 is preferred, and certainly that's what I've used for this. Also you need more subs - DSS seems to come into its own with 20 subs +.  Mayby try that - even if it means reducing each exp time. My best effort was with  - approx 20 *5 minute subs at ISO 800. Not saying that's the best way though!

Also you do need more darks - if you do, say, 20, DSS will keep a master dark which you can re-use. Most folk keep library darks for different ambient temps - but they dont seem to vary much by temp - at least not to my eye.

Bias - just got to click away with shortest shutter speed - shouldn't be any hassle. Again, DSS will keep master bias.

Flats - this will cause outrage, but I'm fussy about keeping optics spotless and so flats for me is just evening the light distribution, rather than getting rid of dust bunnies. I use a library flat if I don't have time to do per session flats. Only had a problem once with this method. If your camera uses vibration cleaning its likely your bunnies may shift (ooo-eer missus) between closing down and doing flats next day. 

Good luck!

Thanks for the encouragement! I've only just started this but the darks I've created so far can be used again I guess. It's just that so far, I have used different iso and exposures and, as far as I understand it, the darks must be the same as the lights.

Regarding flats, the problem is the orientation of the camera is not fixed. This morning, it shifted a little just before I took the flats so the flats did not produce an even image, there was a kind of halo where, I guess, they 'missed'.

I'm sure I can get this right, it's only the second time I have attempted flats and I just need to be ultra careful to have the camera very tightly attached. I don't have a laptop so I am waiting for daylight to do them. I must look into one of these  light box thingies!

Cheers, Tim. 

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That image is looking good and you are doing a good job, I see a add on tv this week it says ( with out black there no colour) this got me thinking ,

We only every get dark sky in the winter never black skys so with summer we may have dark blue skys for 2 or 3 hours a night,

So we can only do so much with a DSLR camera that not have any mods done .

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Tried the suggestion to stack subs from my two goes at Iris together. Its heavily cropped because the overlapped part was quite small. Does look nice though, and I think it has more detail than either previous set.

post-35654-0-92925400-1433012439_thumb.j

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well I dont think its a bad effort to be fair, I would be over the moon with that

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Love it! I'd personally play with the levels a bit and make the blacks darker, but it would be less accurate (might look a bit more dramatic though). 

I know there is at least one other Harlow amateur astronomer - there may well be others. Perhaps we should form a little club!

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Love it! I'd personally play with the levels a bit and make the blacks darker, but it would be less accurate (might look a bit more dramatic though). 

I know there is at least one other Harlow amateur astronomer - there may well be others. Perhaps we should form a little club!

The Essex and Herts borderlines!

Sounds like a good idea....    

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This is a very tough target even for experienced imagers with sensitive equipment and even tougher to process properly as the bright blue nebula is surrounded by very dark cosmic dust. The other prerequisite for successfully imaging this reflection nebula is dark skies otherwise huge effort is required to correct for the gradients. Your effort is good but the only way to get anything out of your set up is to collect more data. With a DSLR I would suggest a minimum of 25~30 subs of 600s each with a proper LP filter in place ( a nebula filter will do but requires longer exposure ) and the application of full calibration frames including a large number of Bias and Flat frames. You also need to have a look at the collimation of your scope and perhaps the use of a coma corrector as the star at the bottom left shows typical signs of coma. Properly imaged and with enough data you will have the outer halo of the nebula in blue and some yellow orange colour in the core (the core is made up of multiple stars at least visually ) and there is also a hint of colour in the surrounding dark nebula.  Without enough data if you push the processing the end result is just ugly noise. For the sake of clarity I dumped the data from my first attempt even though it was taken with an SW ED 80 and an Atik 428 CCD with over 3 hours of data.

A.G

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