M31 - The Great Andromeda Galaxy - 3/11/2012

[Gina]

M31 - The Great Andromeda Galaxy - from last night. SW ED80 with FR, 1100D cooled to -10C, 120s at ISO 3200, 50 lights, 50 darks, 42 flats stacked in DSS and processed in PS CS5 resized to 1024px no crop. Saved as PNG. Guided with ST80, QHY5, PHD. I think this could do with more data.

[swag72]

A couple of things Gina - If your flats are working, I am surprised that there is still a dark artifact at the bottom left, also there seems to be a rather blue hue - Are the colours balanced in processing?

[StarRaver]

Very nice shot Gina love the detail in this absolutely stunning

[Gina]

A couple of things Gina - If your flats are working, I am surprised that there is still a dark artifact at the bottom left, also there seems to be a rather blue hue - Are the colours balanced in processing?

Yes, that must be a big piece of muck Must take camera off and clean the sensor/filter. The colour is certainly off but correcting the galaxy colour resulted in a magenta background. I'm not satisfied with this image.

[Gina]

Very nice shot Gina love the detail in this absolutely stunning

Thank you

[ItIsOnlyMe]

Great image Gina, how do you cool the camera to -10?

[Gina]

Seeing noise in the image I decided to take some biases and have another go. This next image is with 25 bias frames added and restacked etc. I tried adjusting the image in DSS and it looked much better this time so I used this in PS instead of the unadjusted TIFF.

[Steve Ward]

I had much the same result the same night Gina , 3hrs of 5 minutes certainly should have worked but the Moon killed it .

I was having a bit of a play with camera settings too , do you use the "Standard" or "Neutral" picture style setting ?

I shot that night in Neutral for a change , need to do a few more tests when the Moons gone .

Steve.

[cfpendock]

[ament=76334:IMG_1057x.JPG]I am always very impressed by these photos. But it seems one needs a lot of equipment for tracking etc, as well as lots of software and expertise on how to use it. This is my untracked effort, single shot, 10 seconds at max ISO and close to full moon. Any more time and I am sure there would be extensive trails, hence max ISO and minimum detail. But I have been inspired by your modifications Gina, so I think I must save up for some sort of tracking device and learn to use it ......

Chris

[fwm891]

Hi Gina, I think a lot of your noise is from the hi iso 3200, try 1600. With 100 mins of light data you should be seeing a much cleaner image than that. The new bias frames are an improvement - still think the flats aren't working properly - that big dust/muck bunny should have been removed. Glad your getting some clear weather to do some testing.

[reddoss]

Hi Gina,

Nice work. I had a similar artefact which turned out to be a shadow caused by a bit of dirt on the glass in front of the CCD chip. I got a good quality bulb type blower from a camera shop and it came off after the first puff.

[Gina]

[ament=76334:IMG_1057x.JPG]I am always very impressed by these photos. But it seems one needs a lot of equipment for tracking etc, as well as lots of software and expertise on how to use it. This is my untracked effort, single shot, 10 seconds at max ISO and close to full moon. Any more time and I am sure there would be extensive trails, hence max ISO and minimum detail. But I have been inspired by your modifications Gina, so I think I must save up for some sort of tracking device and learn to use it ......

Chris

Thank you As for yours... Good start You should be able to go to 30s or even a minute if your tracking is good but beyond that you'll probably need guiding.

[Gina]

I had much the same result the same night Gina , 3hrs of 5 minutes certainly should have worked but the Moon killed it .

I stopped when the moon came up, I could see it washing out the subs. That's why I only got 50. Next clear night I'll try to get set up earlier and get more data. I'll also set up to take some short subs for the cantre part.

I was having a bit of a play with camera settings too , do you use the "Standard" or "Neutral" picture style setting ?

I haven't changed it so whatever is the default

I shot that night in Neutral for a change , need to do a few more tests when the Moons gone .

Steve.

Yes, the moon can be a nuisance.

[Daniel-K]

what are the gradients traveling vertical in the image?

[Gina]

Hi Gina, I think a lot of your noise is from the hi iso 3200, try 1600. With 100 mins of light data you should be seeing a much cleaner image than that. The new bias frames are an improvement - still think the flats aren't working properly - that big dust/muck bunny should have been removed. Glad your getting some clear weather to do some testing.

There's something funny going on - my low temperature tests show negligible noise at much longer exposures than the 2m used here. Also, I'm not sure cooling the sensor to -10C is as helpful as it seemed. The thermal noise is reduced to a very low level but there seems to be other noise associated with the signal. Cooling to around freezing seems around optimum.

Anyway, I'm going to use ISO 1600 next time as you suggest and as I was already thinking. I shall also cool to either -5C or 0C. 4m subs should be the same as 2m at ISO 3200 but I'm far from sure that the signal varies in direct proportion to the ISO.

I agree that 100mins of lights should have given a better result - I was surprised to see all that noise. My previous images with ISO 3200 have shown a lot less noise. I also agree about the flats - they normally work better than that. I have taken the camera unit off the scope and cleaned the filter - there was a great big blob of dirt on it which I was able to blow off. I've done a flats test since and that big bunny has gone - still a couple of smaller ones but I think the flats will sort that out for imaging.

I think I was so surprised to get a clear night last night that I wasn't really prepared and it took a little while to get back into things.

[Gina]

Hi Gina,

Nice work. I had a similar artefact which turned out to be a shadow caused by a bit of dirt on the glass in front of the CCD chip. I got a good quality bulb type blower from a camera shop and it came off after the first puff.

Thank you My bit of dirt was on the filter in front of the sensor and I blew it off. I have a "rocket" blower which works very well

[Gina]

Great image Gina, how do you cool the camera to -10?

I used a copper cold finger onto the back of the inage sensor and this is cooled with a Peltier TEC. THe resulting heat is dissipated with a CPU heat-pipe cooler with a big fan. See my TEC cooling thread in the "DIY Astronomer" forum.

[Gina]

what are the gradients traveling vertical in the image?

I don't know - it's strange.

[Auntystatic]

I was having a bit of a play with camera settings too , do you use the "Standard" or "Neutral" picture style setting ?

I shot that night in Neutral for a change , need to do a few more tests when the Moons gone .

Steve.

Camera styles are only used if shooting jpg, when shooting raw it doesn't matter what you set it to as they are ignored, it can be changed in DPP to what you want.

[allcart]

The second image is better and has more contrast although you lost the core. The first image does seem to lack any colour. Not what I expected to see with the setup you have.

There is definately some sort of vertical banding I haven't seen in your pics before. I have no idea what caused it. The normal sort of vertical banding is much wider. Maybe 3200 is a step too far.

Now you'll be thinking...........would it have been better using 25 x 240secs @ iso 1600

[Gina]

The second image is better and has more contrast although you lost the core. The first image does seem to lack any colour. Not what I expected to see with the setup you have.

There is definately some sort of vertical banding I haven't seen in your pics before. I have no idea what caused it. The normal sort of vertical banding is much wider. Maybe 3200 is a step too far.

Now you'll be thinking...........would it have been better using 25 x 240secs @ iso 1600

Something definitely wasn't right! I've used ISO 3200 plenty of times in the past. The camera is in a new box with a new (different) cold finger but I wouldn't have expected that to make any difference. Also though, I ran the cold finger at a set-point temperature of -15C giving about -10C at the sensor. A slightly longer cold finger meant more temperature drop but I can cope with that. It also means the dew or frost will form on the exposed part of the cold finger rather than the filter covering the sensor.

I shall be trying a higher temperature next time - I have a nasty feeling that running the image sensor and processing chip at -10C might not be a good idea. I shall also try ISO 1600 as you suggest - with longer nights extra time is less of a problem.

[jezhughes]

Nice going Gina had a play in PS as that's how i spend my Sunday nights. Hope you don't mind

[ian_bird]

Gina - I am intrigued by this "cold finger" set up. Any chance of posting a link or a picture?

Ah! Never mind. Google is my friend.

Just out of interest - how much does that Mod cost?

Cheers

Ian

[Gina]

Gina - I am intrigued by this "cold finger" set up. Any chance of posting a link or a picture?

Ah! Never mind. Google is my friend.

Just out of interest - how much does that Mod cost?

Cheers

Ian

Links to my threads :-

http://stargazerslounge.com/topic/157627-air-cooled-tec-with-cold-finger-dslr-cooling/

http://stargazerslounge.com/topic/163752-dslr-cooling-to-near-ambient-with-fan-cooler/

[ian_bird]

Thanks Gina!