What are flats please ??

[spaceboy]

Hi All

I think I get darks. Put on dust cap and capture nothing other than the data. What are flats ??

[spaceboy]

Astrophotography For those who are in my boat I found a useful link.

[JohnnyD333]

I think your article sums it up well. They really help with DSLR images, getting rid of any vignetting or dust in the photo. Flats are not really difficult to take once you have done it a few times. The popular methods are covering your scope with a tshirt or pointing it at the horizon. I hold a white screen (my laptop) up to my telescope and adjust the exposure time until I see vignetting in my images (usually about 1/100 exposure) I leave the ISO the same. Take 10 like the article says. Good luck

[LukeSkywatcher]

So flats are the opposite of darks?

[Quatermass]

Flats are just like darks in that they are a pain in the bottom..

but they are not that hard to do for darks just put the cap on the end of the scope and take another 30 shots at the same setting as your normal shots. Then for flats an easy way to do this is to put a white t shirt or pillow case over the end of the scope like a muslin bag over a jam jar. Then get a 25 led torch or similar and arrange it so its in front of the scope end, I hang mine on off my camera tripod so its directly in front of the scope and take another 30 shots.

Then for the Bias/offset shots just put the cap on again and set the camera shutter speed to as fast as it will go and take 30 shots. I'm finding that generally 30 main shots with 30 darks flats and bias/offsets gives pretty good results depending on what your imaging. Using a remote camera shutter release is means I can set it to take 30 shots for each batch and just go in the house to warm up till its done.

Darks and flats improve your images no end so don't skimp on them about 30 is a good number to take for general use.

This is the torch I use.

And this is my set up.

A brolly to block out the neighbours lights and my camera attached to the telescope with a t adapter and a remote timer for the shots so I don't have to freeze outside. I have an extension lead running to an adapter that plugs into my RA axis control pad and keeps the tracking well powered the battery pack is a pain to use. Telescope is a skywatcher 200p with an eq5 mount and single ra drive motor. the camera on this photo is the old Lumix G1 now replaced with the canon 350d

Its a basic astrophotography set up but it works well.

Camera is a canon 350d unmodded.

and the all important Bahtinov Mask for focusing with.

[spaceboy]

I have a mask but I just don't get on with them. The image is so tiny in the camera view finder / live view that I find I'm guessing even with the mask. With out the mask I have the choice between several stars in the FOV and once fainter stars become apparent I know I have a reasonably OK focus. Any tips on using a mask would be appreciated though

[Quatermass]

The secret with the mask is to get a rough focus first using live view or if you dont have it take a quick 15 second shot and refocus after checking your picture on the cameras screen view. Then put the mask on and take another shot. This time zoom in on the image to see where the spikes are lining up and refocus if needed. You also need a bright star like vega to get a good set of spikes in the masked image. You can guess it but the mask insures a sharper focus. Stacking blurred images is a waste of time so I allways use the mask now

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[spaceboy]

You can guess it but the mask insures a sharper focus. Stacking blurred images is a waste of time so I allways use the mask now

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Tell me about it. I must have wasted 10 minutes last night taking blurred pics. 10 minutes I could have spent looking at the object instead of standing there freezing twiddling my thumbs. It is fun to see the end result but the actual process of getting the images is like watching paint dry IMHO. I doubt imaging is for me but I have enjoyed having a mess.

[JohnnyD333]

So flats are the opposite of darks?

I dont believe they are the opposite. In a way, darks and lights seem like the opposite because the images are dark and light, but in imaging they both serve specific purposes. Darks are dark, but their purpose is to produce noise from long exposure imaging, which will be subtracted from the lights. Lights produce the data you will be pulling and stretching from the final image.

Flats seem like a challenge, but they are not that difficult. Point your scope at an even light source and adjust your camera settings until you have photos that produce vignetting. You dont want bright white images, they should show some vignetting and possibly dust from the lens. Give it a shot:icon_salut:

[Quatermass]

Tell me about it. I must have wasted 10 minutes last night taking blurred pics. 10 minutes I could have spent looking at the object instead of standing there freezing twiddling my thumbs. It is fun to see the end result but the actual process of getting the images is like watching paint dry IMHO. I doubt imaging is for me but I have enjoyed having a mess.

It only takes about 5 minutes to get your camera focused if you concentrate on a very bright star and just zoom in to check the spikes are in the middle with the mask on. That done I point at the subject say the Orion nebula and take a few more quick shots adjusting the axis knobs to centre it up in the picture then I'm good to go.

Just set my remote camera shutter controller to take 30 shots and let it get on with it. Mean time I get my binoculars out and use them to look around. If I get cold its back in the house for a cup of coffee and a biscuit then after 20 mins the camera has done its work, the timers stops taking pictures and I can check out what I have captured. But another cool use for the camera is to find those faint fuzzy's .

I find this a most useful method to spot galaxy's and nebula that are hard to see. Point the telescope where you think it should be and take a 15 or 20 second shot. Take a look at the picture and 9 times out of ten you can find what your looking for far quicker then just looking through the eye piece because the camera can capture what your eye cant see.

Now if I can just figure out how to blow the clouds away

[spaceboy]

It only takes about 5 minutes to get your camera focused if you concentrate on a very bright star and just zoom in to check the spikes are in the middle with the mask on. That done I point at the subject say the Orion nebula and take a few more quick shots adjusting the axis knobs to centre it up in the picture then I'm good to go.

Just set my remote camera shutter controller to take 30 shots and let it get on with it. Mean time I get my binoculars out and use them to look around. If I get cold its back in the house for a cup of coffee and a biscuit then after 20 mins the camera has done its work, the timers stops taking pictures and I can check out what I have captured. But another cool use for the camera is to find those faint fuzzy's .

I find this a most useful method to spot galaxy's and nebula that are hard to see. Point the telescope where you think it should be and take a 15 or 20 second shot. Take a look at the picture and 9 times out of ten you can find what your looking for far quicker then just looking through the eye piece because the camera can capture what your eye cant see.

Now if I can just figure out how to blow the clouds away

TBH I have not looked at the manual and didn't realize you can zoom in. I take it you mean when in live view mode ?? I will have to flick through the manual when I get 5 minutes rest bite from my noisy lads shouting Dad every 10 seconds

I have ordered a remote for the camera so at least I can get some observing in while I wait. With clear skies so far and few between I don't want to miss out for the sake of £10

I agree regards finding faint and fuzzes. M33 is always a challenge where I am and even with a 30 sec exposure it didn't show up in the images so it will be a nice challenge to see if I can get some thing in the future.

If I'm honest I prefer visual observing but it has been fun to give imaging a go. The wife has showed enthusiasm saying the images I have captured she wants up on the wall. Usually she cocks a deaf un when I'm chatting about astronomy.

I gave M42 a go the other night and while not very good compared to most posted on SGL it shows a great deal more detail than I could ever wish to see looking through the scope.

[Quatermass]

Space boy thats a great shot you should be very happy with that. Yes zoom in on your picture when you take a shot and that will show you were the spikes are. Getting the timer is going to make a big diff no point standing there waiting and you can grab a coffee. Try the unsharpmask in photoshop and highpass filter as well theres tutorials for that on my blog. ;-)

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[spaceboy]

I have Adobe photo shop 8 which is very tempremental on Vista so any adjustments are kept to a minimum (curves, contrast) but I will give it a try.

Thanks for you help!