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  #21  
Old 19-07-2017, 03:21 PM
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Nebulous (Chris)
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Originally Posted by xelasnave View Post
Chris
I think there is a problem called field rotation.

Alex
Thanks Alex, Yes, that's clearly a problem, and I had just edited my post to mention that, (before reading yours - believe it or not ) because I'd left it out originally ...doh...


But there's always a period of time before the effect of field rotation cuts in. I can take simple exposures on a tripod for up to 20secs without losing star shape. Once I use a scope the time drops dramatically, but I can still get clear shots. I'm imagining that I could possibly take a whole row of short shots, realign them to correct the rotation, and then stack them. But I may be way off the mark! I've never tried stacking, so I may have a completely wrong idea about what it can achieve.

There's a site that I have visited before which explains the field rotation issue very clearly. They say that it rules out "long exposure" photography, but it left me unclear as to how long is "long" I suppose it depends on the telescope. I guess I'm just going to have to try it out and see.

http://www.astronomyasylum.com/teles...stutorial.html

I'd like to know how the guy in that video did it though.

EDIT: He says "Programs used were, Deepskystacker to stack the images & StarTools to process the images. Because of field rotation I am limited to around 60s depending on position of DSO. The mount is not modified in any way."

60 secs sounds like an age to me. Is his location so much more favourable than mine as far as the general effects of field rotation go? I know that it makes a big difference how far out from the centre of rotation an object is... but 60 seconds sounds like a long time. I guess I'll just have to give it a go...

Last edited by Nebulous; 19-07-2017 at 04:40 PM. Reason: more typos... more corrections...
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  #22  
Old 19-07-2017, 03:54 PM
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I have not tried it but I bet if you used a static tripod with a high iso on your camera and stacked and cropped you would get a pleasing result result for many objects.
When I started with astro photos I was lucky to get 30 seconds problems so I would stack 50 or more ...not the best but that had to do until I got a decent mount.
And if I start again I will get say a canon 70d forget auto guide and expose for as long as possible and stack those ...
But like all things try what you think works even if something does not work you learn stuff.

Alex
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  #23  
Old 19-07-2017, 03:56 PM
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And you can have fun doing the Moon and learn things...
Alex
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  #24  
Old 19-07-2017, 04:02 PM
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Originally Posted by xelasnave View Post
But like all things try what you think works even if something does not work you learn stuff.

Alex
So true.

I've spent a lot of my life learning by trial and error and i still enjoy the method.

I need to find a site to read up about stacking, because I still really don't know what it achieves. I'm assuming that it can combine details that appeared in one frame but not another, but I don't know if you can end up with a brighter star from 20 dimmer shots, or whether you just get a nicer looking dim star?!
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  #25  
Old 19-07-2017, 04:12 PM
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I am not up with what's available these days but there was a program registax? And deep sky stacker both free but get your hands on a stacker program and start learning...
I will have a look what's around but you could have a look...use google...its new but a wonderful thing
Alex
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  #26  
Old 19-07-2017, 04:14 PM
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Try this.
http://deepskystacker.free.fr/english/index.html
Alex
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  #27  
Old 19-07-2017, 04:22 PM
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I took photos of the Moon thru a six inch refractor by holding a 2 meg camera at the eye piece..came out pretty good. I was very happy. Played with it in a photo shop program..brightness contrast sharpness not knowing what I was doing but I was so proud of those early shots...back in 2003 I think.
We would use web cams and stack those...you would be surprised to see how 3000 captures of Saturn stacked looked.
Good luck.
Alex
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  #28  
Old 19-07-2017, 04:23 PM
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Originally Posted by Luca.C View Post
Hi,

my name is Luca and I am from Melbourne.

I've been interested in astronomy for a very long time, and now it's time to finally get a telescope, though I am still quite confused.

Hi Luca,

Apologies for taking your thread in a somewhat different direction... so I hope that the digression threw up something of interest to you.

It's perfectly normal to be "quite confused", as you say - even after buying a telescope or two! As others have said above, there's no single perfect answer as the different mounts and telescope designs all have their pros and cons.

There's a good pair of articles in the stickies at the top of this forum - Article 1 and Article 2, which cover a lot of the aspects. Worth a read.

When I started (a whole 3 months ago!) by far the hardest thing for me was simply finding my way around the sky. When i looked through a telescope what I could see was a whole lot busier and more complex than what i could see with the naked eye, or on basic star charts. So I was glad that my first scope was a basic fairly low powered refractor. I still couldn't see, for instance, the whole of the Southern Cross, only a part of it at one time. But at least everything was "the right way up" so I was able to slowly get the hang of navigating through star hopping.

What scope you buy first depends a lot on your priorities. Mine was to learn more about the layout of the skies first, before diving into deep space object and/or astrophotography. So a basic refractor with a simple alt-az mount was a good choice - easy to carry about, easy to set up (open tripod and start viewing, no real setup to do) and easy to use. It even works with a camera attached. Then, as i got more familiar with navigating I bought a more powerful telescope.... and got lost all over again...

But it's a great hobby and whatever you choose will have more plusses than minusses.

Good luck with it.

Cheers.

Chris
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  #29  
Old 19-07-2017, 04:54 PM
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Hi Alex,

I have been using sharcap with a zwo camera in the focuser to stack images. I use this to take video of the planets and run the video through autostakkert and registax. The deep sky stuff like orion i stack the image and change the exposure and gain levels through sharpcap in realtime. Ita quite fun

The guys on the forums have helped me heaps on the eaa stuff.


http://www.iceinspace.com.au/forum/s...d.php?t=150472

Jupiter attached using sharcap and a goto dob.

Regards,

Mel

Quote:
Originally Posted by xelasnave View Post
I am not up with what's available these days but there was a program registax? And deep sky stacker both free but get your hands on a stacker program and start learning...
I will have a look what's around but you could have a look...use google...its new but a wonderful thing
Alex
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  #30  
Old 19-07-2017, 05:34 PM
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Hi Mel
Great work with Jupiter better than anything I ever did.
We are very fortunate that Mike started this site and that so many folk take the time to help folk.

Alex
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  #31  
Old 19-07-2017, 05:50 PM
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Originally Posted by xelasnave View Post
Hi Mel

We are very fortunate that Mike started this site and that so many folk take the time to help folk.

Alex
+1

I've been on a lot of different forums over the years, for a variety of hobbies and topics, and this one is head and shoulders over the pack. Unlike many forums, even the arguments seem to be conducted in a respectful manner.

Does astronomy attract a more thoughtful and type of person than some other hobbies, or what? Perhaps we're all just slightly mad in a similar way, but I can only say that I've been very impressed by the friendly helpful atmosphere here.
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  #32  
Old 19-07-2017, 06:50 PM
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Question

Thanks for that. I am still a newbie and still learning - lots of fun and frustration at the same time

Totally agree that this site ia a great resource and a credit to Mike.

Thanks,

Mel

Quote:
Originally Posted by xelasnave View Post
Hi Mel
Great work with Jupiter better than anything I ever did.
We are very fortunate that Mike started this site and that so many folk take the time to help folk.

Alex
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  #33  
Old 19-07-2017, 07:46 PM
m11 (Mel)
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Hi Nebulous,

Couldnt agree more

Mel


Quote:
Originally Posted by Nebulous View Post
+1

I've been on a lot of different forums over the years, for a variety of hobbies and topics, and this one is head and shoulders over the pack. Unlike many forums, even the arguments seem to be conducted in a respectful manner.

Does astronomy attract a more thoughtful and type of person than some other hobbies, or what? Perhaps we're all just slightly mad in a similar way, but I can only say that I've been very impressed by the friendly helpful atmosphere here.
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  #34  
Old 20-07-2017, 12:01 PM
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Alex, all stacking does in a deep sky sense is reduce noise, a common misconception is that it makes the image brighter/more details, but in the end a 60 second shot if always a 60 second shot, even after stacking. It is really hard in my opinion to bring any faint detail out with 60 second subs, maybe impossible.
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  #35  
Old 20-07-2017, 12:22 PM
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Originally Posted by Lognic04 View Post
Alex, all stacking does in a deep sky sense is reduce noise, a common misconception is that it makes the image brighter/more details, but in the end a 60 second shot if always a 60 second shot, even after stacking. It is really hard in my opinion to bring any faint detail out with 60 second subs, maybe impossible.
Not impossible but certainly not for novices. You really need to start thinking in terms of signal to noise ratio with astrophotography.

Signal is the information in the field of view you want to keep.

Noise is introduced information by the capture system that you dont want. Its very weak and not often seen but its always there.

For everyday photography the same applies but in that case the Signal just overwhelms the Noise that you rarely ever notice it.

In astrophotography the signal is often as weak as the noise so you have to amplify it a LOT to see it, but that also amplifies the noise too. Noise reduction only does what it says, it REDUCES noise, does not remove it. By stacking the noise gets averaged down deeper but its still there. What it gives you is more room to amplify the signal up to see it without noise becoming too dominant.

It this that gives people the misconception stacking makes brighter images, it absolutely does not unless you used the wrong stacking method. Its not the point of it, it just gives you more room to adjust your image before noise ruins it.
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  #36  
Old 20-07-2017, 02:53 PM
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Originally Posted by m11 View Post
Hi Luca,

One question I forgot to ask is if you have had experience with looking through a scope?


Mel
Hi Mel,

No, not at all! This is my very first approach to space watching!
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  #37  
Old 20-07-2017, 02:55 PM
Luca.C
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Quote:
Originally Posted by m11 View Post
Hi Alex,

I have been using sharcap with a zwo camera in the focuser to stack images. I use this to take video of the planets and run the video through autostakkert and registax. The deep sky stuff like orion i stack the image and change the exposure and gain levels through sharpcap in realtime. Ita quite fun

The guys on the forums have helped me heaps on the eaa stuff.


http://www.iceinspace.com.au/forum/s...d.php?t=150472

Jupiter attached using sharcap and a goto dob.

Regards,

Mel
Hi Mel,

That photo of Jupiter is amazing!

Is that through your 8 inch skywatcher?
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  #38  
Old 20-07-2017, 02:59 PM
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Originally Posted by Lognic04 View Post
Just to let you know, although it seems like it you CANT do any astrophotography with the 6se, because it is alt-az (tracks the stars the wrong way for astrophotography!), and the fact that is it very slow (f/10) makes it very difficult even on an EQ mount, so in my opinion steer clear!
Hi Logan

Would a wedge resolve the field rotation issue?

Cheers,
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  #39  
Old 20-07-2017, 03:03 PM
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Originally Posted by pfitzgerald View Post
Hi Luca (and welcome to IIS)
Before buying any gear might I suggest that you consider joining the Astronomical Society of Victoria. As well as holding Star Parties - where you would have the opportunity to look at and through a variety of different telescopes - with owners willing to share their knowledge with you - there is also the opportunity to hire, for a very reasonable fee, a Dobsonian type scope which you can then test drive to see if it meets your needs. Just a thought...
Kind regards.
Paul
Thanks Paul,

Attending some ASV sessions and seeking advices from them is a good idea given that I have never looked through a telescope before.

Are you a member?

Luca
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  #40  
Old 20-07-2017, 03:09 PM
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Originally Posted by Nebulous View Post
Hi Luca,

Apologies for taking your thread in a somewhat different direction... so I hope that the digression threw up something of interest to you.

It's perfectly normal to be "quite confused", as you say - even after buying a telescope or two! As others have said above, there's no single perfect answer as the different mounts and telescope designs all have their pros and cons.

There's a good pair of articles in the stickies at the top of this forum - Article 1 and Article 2, which cover a lot of the aspects. Worth a read.

When I started (a whole 3 months ago!) by far the hardest thing for me was simply finding my way around the sky. When i looked through a telescope what I could see was a whole lot busier and more complex than what i could see with the naked eye, or on basic star charts. So I was glad that my first scope was a basic fairly low powered refractor. I still couldn't see, for instance, the whole of the Southern Cross, only a part of it at one time. But at least everything was "the right way up" so I was able to slowly get the hang of navigating through star hopping.

What scope you buy first depends a lot on your priorities. Mine was to learn more about the layout of the skies first, before diving into deep space object and/or astrophotography. So a basic refractor with a simple alt-az mount was a good choice - easy to carry about, easy to set up (open tripod and start viewing, no real setup to do) and easy to use. It even works with a camera attached. Then, as i got more familiar with navigating I bought a more powerful telescope.... and got lost all over again...

But it's a great hobby and whatever you choose will have more plusses than minusses.

Good luck with it.

Cheers.

Chris
Hi Chris,

Thanks for your welcome and please no need to apologise for the (further) discussions you guys have been having...actually I've read them all, it's a great occasion to learn more!

As of the scope, I really don't want to rush things and make the wrong decision wasting money.

What is your second telescope?
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