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robmichael81

DSO with no guide??

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I have a Celestron 130 EQ MD and a Canon 40d DSLR. Whilst I am aware that there will be limitations with this scope and camera, I was wondering what objects I could expect to see/image other than planetry/lunar objects. I live in Liverpool so light pollution is an issue.

If anyone has any examples using this scope that would great.

Cheers,

Rob

I've attached my best attempts at the Moon and Jupiter so far.

post-39243-0-41119400-1414680784.jpg

post-39243-0-83660600-1414682322_thumb.j

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Globular and open clusters will be fine for imaging. I'm guessing that with good balance and polar alignment, 30-46 sec exposures shouldn't be a problem. Also some bright nebula such as m42 will come out ok too. A light pollution filter will probably be a good investment also.

hth

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M45 etc can be done with relatively short exposures

your mount will determine what exposures you can run (the better the mount, the better the tracking)

with a goto EQ5 I could get 3 min exposures with no guide scope just the mount tracking

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The best thing to do is try it, there are plenty of objects that can be captured with around 20-30 sec exposures you could also try piggybacking your camera with a lens for some widefield stuff too and would probably get exposures upto a min or so.

Alan

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You can still make really good images with short exposures you just need to take lots of them. Of course it's gonna take poor old DSS a bit longer to stack 180 x 20 second exposures than 6 x 10 minute exposures but it is the same amount of data in the end, the longer exposures will just have less noise.

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I'd be chuffed with those images Rob.

Cheers Dave,

I'm pretty new to all this and was really pleased with my Jupiter image until I've seen what other people/scopes can achieve. Still, I know where I can improve things without shelling out 1000's. So here's to some clear sky's.

Rob

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Hi Rob, all the above info is quite correct. For long exposures, over 90secs, you need autotracking and a very sturdy mount. I'm having similar problems as I've no tracking capability only a motor drive on right ascension. One of the major contributors to good images is with the processing. Loads of people swear by Photoshop, (megabucks!!!). Corel Paintshop is cheaper and Gimp is free but I have found these to be a little difficult, interesting, but a little difficult. You could try StarTools. I got the trial a couple of weeks ago and my images seem to be a lot better. Their tutorials are pretty good but without narration. Most importantly, it can get rid of light pollution and other bad stuff that can appear on the original. The program is for astrophotography, Photoshop is for Vogue and other glossy mags. The trial is open ended, no time limit, problem is, you can't save anything, they've got you by the bits but it is great for practice. I'm getting it for Christmas so I'll be able to save stuff after that. If you want to keep in touch we can compare notes as I'm pretty new to this game myself. One other essential bit of kit is a Batinov mask. Even slightly out of focus will ruin everything and just by the way, mine's a 40D as well. Best of luck, P.

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You can still make really good images with short exposures you just need to take lots of them. Of course it's gonna take poor old DSS a bit longer to stack 180 x 20 second exposures than 6 x 10 minute exposures but it is the same amount of data in the end, the longer exposures will just have less noise.

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I'm not sure about the 2nd and 3rd points made here? I agree about being able to take good pics unguided but don't very long exposures bring out the fainter regions much better than short exposures?

e.g if you image M42 with lots of very short exposures you will bring out nice detail in thr bright core, but if you take very long exposures you will bring out detail in the faint outer regions at the expense of over exposing the core, this is why both long and short exposures are useful because you can process two layers, one with the faint outer regions and one with the bright core detail :)

lots of very short exposures would  show less noise than a few long exposures with an un-cooled camera. With long un-cooled exposures the noise builds up over time reducing the signal to noise ratio (this is why cooled CCD's are a good thing for long exposures), with lots of short exposures both the noise doesn't have a chance to build up and the noise gets averaged out with stacking with a lot of subs. 

Totally agree that you can still do great things with unguided shorter exposures, I've only ever taken unguided subs between 30 and 180 seconds and have been happy with the results :) 

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Hi Rob, all the above info is quite correct. For long exposures, over 90secs, you need autotracking and a very sturdy mount. I'm having similar problems as I've no tracking capability only a motor drive on right ascension. One of the major contributors to good images is with the processing. Loads of people swear by Photoshop, (megabucks!!!). Corel Paintshop is cheaper and Gimp is free but I have found these to be a little difficult, interesting, but a little difficult. You could try StarTools. I got the trial a couple of weeks ago and my images seem to be a lot better. Their tutorials are pretty good but without narration. Most importantly, it can get rid of light pollution and other bad stuff that can appear on the original. The program is for astrophotography, Photoshop is for Vogue and other glossy mags. The trial is open ended, no time limit, problem is, you can't save anything, they've got you by the bits but it is great for practice. I'm getting it for Christmas so I'll be able to save stuff after that. If you want to keep in touch we can compare notes as I'm pretty new to this game myself. One other essential bit of kit is a Batinov mask. Even slightly out of focus will ruin everything and just by the way, mine's a 40D as well. Best of luck, P.

Thanks for your advice. I agree that processing seems to really help and its something I need to get to grips with. At the moment I have only used registax for processing. Would love to use photoshop but cost is a bit prohibitive and I probably wouldn't have a clue how to use it. At the moment I am trying to increase my fps on live view in order to increase the number of frames I have to stack. I feel a new faster laptop is the solution.

Rob 

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I'm not sure about the 2nd and 3rd points made here? I agree about being able to take good pics unguided but don't very long exposures bring out the fainter regions much better than short exposures?

You are absolutely right. 180 x 20s is not the same as 6 x 10 min. I think, maybe 1000(and more) x 20s will give the similar result as 6 x 10min. Tested many times, but on shorter exposures(5s and 30s) :)

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You are absolutely right. 180 x 20s is not the same as 6 x 10 min. I think, maybe 1000(and more) x 20s will give the similar result as 6 x 10min. Tested many times, but on shorter exposures(5s and 30s) :)

I've noticed the night sky tool that allows you to calculate the maximum unguided exposure length for your telescope.

What I don't quite understand is what the difference is between Dark's, Flat's, Bias etc... 

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Darks are taken with the telescope cover put on so that no light gets to the sensor in the camera. They are taken with exactly the same settings as your main photos, length of exposure, iso number and aperture setting, also at the same time as temperature affects the result. This is because your camera will produce loads of little dots that the final photo doesn't need. The stacking system will  see these in your 'darks' and deduct them from each photo that makes up your final image. Your camera produces different amounts of these dots, and in different positions,  according to the camera settings but same settings equals same amount and position. A good way to see these is to install Astronomy Photo Tool, APT,  (free), and take say a 60 sec. exposure with the lens cap or telescope cap on and with the 'image preview' box ticked. You'll see the little blighters and think where on earth did they come from!!! I haven't a clue what Bias frames actually do, I've googled it but still don't understand,  but the final image is not so good without them. As a general rule of thumb, the number of 'darks' is the same as the number of 'bias' and this should be no less than the square root of the number of 'lights'.

This hobby really does have a steep learning curve but like most things it's practice, practice, practice and the rewards are quite incredible. I found Deep Sky Stacker,(free) really daunting to begin with but once it comes out right it truly is 'eureka'!!! 

Any problems can be sorted by the guys on here, it really is an excellent website.

P.

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So what would be a reasonable expectation for exposure length with full mount tracking?  For the first time I managed to get three minutes the other day on my AZ-EQ6 GT and have often achieved 90 seconds often but would really like to get 3 to 5 minutes routinely.  I am having significant problems with polar alignment, which seems key -  I'm presuming that successful autoguiding will deal with these issues?  

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Just as a point of clarity, Photoshop is a subscription service these days, at around £9 or £10 per month. This works out expensive over a long period of time, but if you wanted to play about with it for a while, it isn't the mammoth cost it might appear.

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Darks/Flats/Bias/Dark Flats are all about removing imaging imperfections from your image, from camera sensor issues like thermal noise, like broken pixels, optical path issues like uneven light distribution (vignetting) and from simple dust/dirt on the camera lens etc. This can all be subtracted from your image through the use of the darks/flats etc to reveal as close as possible the actual photons from the objects you took a picture of.

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Try and find Polar Finderscope by Jason Dale. It's free, and a simple little program that tells you where polaris should look in your polarscope.

Just to show that things will go wrong if they can.......went out last night to image Triangulum galaxy. Even 60 sec exposures were dodgy. Had to chuck out 42 out of 103. Got really fed up as I couldn't find out why. Backlash, polar alignment, wind, moles!! 3 night ago managed 55x90 secs of Bodes out of 60 and 88x60 secs of Bodes out of 90, and that was after getting the hairdryer onto it half way through each session to get rid of condensation. God I love this hobby!!!! 

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Also, with an EQ6 with full guiding the world is your oyster, 3 minutes, 5 or even try 10 if there's no wind etc.. 

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Darks/Flats/Bias/Dark Flats are all about removing imaging imperfections from your image, from camera sensor issues like thermal noise, like broken pixels, optical path issues like uneven light distribution (vignetting) and from simple dust/dirt on the camera lens etc. This can all be subtracted from your image through the use of the darks/flats etc to reveal as close as possible the actual photons from the objects you took a picture of.

Hi Matt,

Thanks for the reply. It's still as clear as mud to me.

Piprees explained how I get my darks by taking pictures with the telescopes cover on and with the same exposure/ISO/aperture as the main picture.

What are the rules with flats, bias and dark flats? And is this the main (four?) types of pictures I need to get to then go to the processing stage?

Thanks for everyone's help with this,

Rob 

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Hi Rob, all the above info is quite correct. For long exposures, over 90secs, you need autotracking and a very sturdy mount. I'm having similar problems as I've no tracking capability only a motor drive on right ascension. One of the major contributors to good images is with the processing. Loads of people swear by Photoshop, (megabucks!!!). Corel Paintshop is cheaper and Gimp is free but I have found these to be a little difficult, interesting, but a little difficult. You could try StarTools. I got the trial a couple of weeks ago and my images seem to be a lot better. Their tutorials are pretty good but without narration. Most importantly, it can get rid of light pollution and other bad stuff that can appear on the original. The program is for astrophotography, Photoshop is for Vogue and other glossy mags. The trial is open ended, no time limit, problem is, you can't save anything, they've got you by the bits but it is great for practice. I'm getting it for Christmas so I'll be able to save stuff after that. If you want to keep in touch we can compare notes as I'm pretty new to this game myself. One other essential bit of kit is a Batinov mask. Even slightly out of focus will ruin everything and just by the way, mine's a 40D as well. Best of luck, P.

Sorry, but I've really got to say something here. As you say, many people swear by photoshop and there's a very good reason for this. IT'S GOOD... Have a look at any of the really good imagers on sgl and there will be very few if any that don't use it at some point in their processing. PS is not just for glossy mags, it's for people who want to get the most out of there photography, be it terrestial or astro. yes it'snot cheap, but neither is any other aspect of A.P.

I'm not saying you have to have it, but you'll be glad you do if you have :)

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Bias : Cover on. Taken as quickly as the camera can take. This shows the readout noise of the sensor when the sensor is 'read'.

Darks: Images taken with the telescope cover on and for the same duration as your normal images of the object. This will show the noise as a result of temperature buildup etc in the camera.

Flats : Taken with cover off and pointing at an even light source. This shows the effect of any dust particles and the uneven light pattern of the optics so that can be removed from the final image.

Dark Flats : These are with the cover on and for the same time that the flats were taken with. This then accounts for thermal noise etc which can be subtracted from the flats themselves to make a 'perfect flat'

All very complex and something I often don't bother doing (some not all) and it took me a good while to get my head round it.

Matt

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Sorry, but I've really got to say something here. As you say, many people swear by photoshop and there's a very good reason for this. IT'S GOOD... Have a look at any of the really good imagers on sgl and there will be very few if any that don't use it at some point in their processing. PS is not just for glossy mags, it's for people who want to get the most out of there photography, be it terrestial or astro. yes it'snot cheap, but neither is any other aspect of A.P.

I'm not saying you have to have it, but you'll be glad you do if you have :)

Indeed.

GIMP is good for a free piece of software but the last time I used it I couldn't even use 12 bit images. You're going to lose a lot converting to 8 bit images.

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The development release can handle 16 bit images so use that for astro work.

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Edited by D4N

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