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#1 Kalox

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Posted 26 June 2013 - 04:35 PM

Hey guys,

I have a Celestron CGE 1400 and a SBIG ST-2000XM CCD camera which I'm just getting to know. I started looking at the sky through the telescope and I think I know the basics. However I'm a bit more interested in the astrophotography part.

Could you please give me some hint on how exactly everything goes? I mean - I have read quite a lot on the internet and in spite of this I still can't figure out how to make a decently good picture of... something.
The thing I started off with is the Andromeda galaxy. My telescope is facing north (west-north-east) and in the last few days the only good thing I could see was the Andromeda galaxy (and Venus). So I tried and I took a couple of pictures of both of them. Well it didn't go very well... or... to be honest I don't really know how it went.
I have attached the picture of Andromeda that I got (a single picture, no processing, nothing).
Could you guys give me a little bit info - firstly I don't know if a raw picture should look like this (attached file) and then... could you please give me like a guide to... what I should do in order to get a good picture in the end? I'm pretty convinced that when I do it once (with Andromeda for example) I'll get the hang of it and then will be able to shoot other objects on my own. I don't know what exposure times I should be using, how many frames, how many dark frames, when to subtract the dark frames (before I stack the images, or after, or should I do a stack of dark frames also or...??) how to take and use "flats" and what about cold and warm pixels and...

Any information that you guys could give me would be greatly appreciated.

Thanks :)
Kalox

Attached Files



#2 mmalik

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Posted 26 June 2013 - 06:19 PM

You have picked a large and difficult target to practice on; try something more discrete and not so distributed, like a globular cluster may be. Don't know much about your camera but if it is cooled you may be able to get by without taking darks. Focusing the object is important. Not sure if you are guiding? Guiding will be needed for longer than few seconds exposures. If you are not guiding, just take may be 10-20 sec lights and stack a bunch of them.

Retrospectively, DSLR may have been an easier start than a CCD since most DSLRs have live view that you can use to frame/focus, etc.

Here... are some basic stacking and processing instructions if you would like to try. Some of the trial/eval software will be good starting point and will not cost anything.

This info may not be enough to get you started but keep asking questions. Regards

#3 WarmWeatherGuy

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Posted 26 June 2013 - 08:07 PM

Hey guys,

I have a Celestron CGE 1400 and a SBIG ST-2000XM CCD camera which I'm just getting to know. The thing I started off with is the Andromeda galaxy.

Any information that you guys could give me would be greatly appreciated.

Thanks :)
Kalox


You need to calculate your field of view.

Field of view calculator
http://www.12dstring.me.uk/fov.htm

This says your field of view is 10.41' x 7.81' which is 0.17° x 0.13°. The Andromeda Galaxy is over 3° wide. It looks like you got the core of the galaxy. I did the same exact thing with my C8. Then I got this book:

The 100 Best Astrophotography Targets: A Monthly Guide for CCD Imaging with Amateur Telescopes
http://www.amazon.co...s/dp/1441906029

It shows 100 cool things to take pictures of. Each image has information about the field of view, telescope used, and exposure time.

If you're going to use your C14 I would recommend a focal reducer and then choose some of the items that are small. Try M57, the ring nebula.

Your life will be much easier if you start with a short refractor. If you don't have one then you can't go wrong with this one:

AT72ED
https://www.astronom...scope-black_...

#4 Rick J

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Posted 26 June 2013 - 08:31 PM

If you take up tightrope walking you will likely start with walking across the Grand Canyon. That's pretty much what you are trying here for your first try at CCD imaging. That camera and a C14 at f/11 has an image scale of less than 0.4" per pixel. Virtually no one here would do that even after years of practice. Your field is about 10.4 minutes by 7.8 minutes. That's only a very tiny fraction of the galaxy. That's like photographing a close up of a cloud. Virtually no detail to be seen.

Start by using a 0.67 reducer then bin 2x2 for a still very difficult 1.16" per pixel. Learning to track at that image scale is difficult. Yes I did post an image taken at 0.5" of a small portion of the galaxy but I have decades of experience and still needed 5 months to get enough usable frames at that image scale. But even then I used a chip that had a field of view of about 750 square minutes of arc at that scale while yours has only a bit over 80 square minutes. Then you used that tiny field on the core which has the least detail. I picked a region of unusually high detail. Someone with lots of experience stretching and thus coaxing detail out of low contrast features might have a chance with the core given an hour or more of exposure time (total) but not a beginner.

Start with bright objects with high detail that shows good detail at high power visually like a globular cluster or some planetary nebulae (M31 visually is just a blob at high power).

Your camera requires good master darks. With the small chip you might get away with no flats until dust becomes a problem then a master flat will be needed to remove the dust donuts. At that image scale long guided exposures will be necessary to keep read noise at bay. You can get something with really bright clusters with 30" images. Even that is tricky unguided at your image scale. Without proper darks and stretching little will be seen with that camera. It's a good camera (not so much so for that scope however) but you have to know how to use it.

I'd recommend putting a small refractor atop the big SCT and learn with that before attempting anything further with the big scope. Even a 600mm focal length with that camera will show nice detail and be a better match to your typical seeing than that camera on the big scope.

You don't mention the software you are using but correct software is critical. The learning curve is steep. Don't make it virtually impossibly steep by starting where you tried. If this were easy everyone would be doing it.

There are many places on the net to learn the basics. One is http://starizona.com/acb/ccd/ccd.aspx

You need to know the sky well visually before moving into deep sky work. When you say you only had M31 and Venus as targets that might indicate you need to learn the sky a lot better. I'd see many targets in the area you mention. Also try to image near the meridian so the object is as high in the sky as possible. At your image scale the chances of even getting a star to focus that isn't high in the sky is very low. At 0.5" I only shoot within an hour of the meridian unless the object is near the zenith then I go 2 hours either side and never shoot below 35 degrees of the horizon at that scale. Another reason why a small refractor is the place to start.

Rick

#5 WarmWeatherGuy

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Posted 26 June 2013 - 08:33 PM

I forgot to mention, that book has some chapters at the end to help you with image processing. Also, there are a few words next to each of the 100 targets about what you might want to do, processing-wise, which is specific for that target.

Attached is an animation of Andromeda I took with the AT72ED. The "dark" frame is what you would get if you didn't expose long enough. You can see how the core is way smaller than the whole galaxy. When your field of view is really small you just get the core. When that happened to me I thought I had bought a bad camera or that I would never figure it out. Thanks to Cloudy Nights we can get help from those who've gone before us.

The core is what you might see with your naked eyes. The galaxy itself is 6 times as wide as the full Moon. I've been told that if you go to a dark enough site you can see most of the galaxy unaided.

Attached Files



#6 Kalox

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Posted 27 June 2013 - 01:59 AM

Thanks for the reply guys, now I really know what I'm getting into. However I would like to learn to use the equipment and I wouldn't want to buy a simpler/cheaper camera, telescope or whatever (I know it would be easier to learn, but it would be... a waste of money)
Anyway, thanks for the replies, I'm gonna get a focal reducer and will see what happens. I will also try photographing a globular cluster.
I have some more questions:
1. What kind of exposure times should I be using to photograph Andromeda? How many pictures?
2. Would it be better to use the HyperStar Lens that I already have?
3. The software I use is CCDOPS. How should I connect the camera to the telescope, so that when I try to move the telescope through CCDOPS (on my laptop) the telescope actually moves...
4. How do I get those beautiful colors you guys get... It definitely does not seem to me like I'm gonna get such a colorful picture like the ones I see, just by combining the 3 images with the red, blue and green filters? Am I wrong?

Thanks again, you guys are very helpful :)

#7 WarmWeatherGuy

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Posted 27 June 2013 - 05:34 AM

Thanks for the reply guys, now I really know what I'm getting into. However I would like to learn to use the equipment and I wouldn't want to buy a simpler/cheaper camera, telescope or whatever (I know it would be easier to learn, but it would be... a waste of money)
Anyway, thanks for the replies, I'm gonna get a focal reducer and will see what happens. I will also try photographing a globular cluster.
I have some more questions:
1. What kind of exposure times should I be using to photograph Andromeda? How many pictures?
2. Would it be better to use the HyperStar Lens that I already have?
3. The software I use is CCDOPS. How should I connect the camera to the telescope, so that when I try to move the telescope through CCDOPS (on my laptop) the telescope actually moves...
4. How do I get those beautiful colors you guys get... I definitely does not seem to me like I'm gonna get such a colorful picture like the ones I see, just by combining 3 images from red, blue and green filters? Am I wrong?

Thanks again, you guys are very helpful :)


The guy who wrote the book I mentioned used 3 or 4 different telescopes. It is not a waste of money, you will eventually want several scopes with different focal lengths. Even with Hyperstar there will be targets that are too large. It makes sense to cut your teeth with the shorter scopes. Hyperstar may be the best way to go initially.

1) For Andromeda I took 9 ten minute exposures at f/6. I would have taken more but I got bored and things were getting wet (dew). More is better but you get diminishing returns. My Andromeda is not processed correctly because I still haven't learned how to use PhotoShop. Half my image is washed out in the center. The AT72ED is a very capable lens for wide-field astrophotography. It sucks if you want to use it to look at Mars though.

2) f/2 gives you over 30 times as much light per pixel as f/11. You can do Andromeda in 20-40 seconds. Although you might not fit the entire galaxy in the picture you should get most of it.

4) Some targets have more color than others. The most colorful targets will be wide-field such as the Trifid or Lagoon nebulae. Globulars don't have much color. You can get some color with small galaxies. Planetary nebulae often have lots of color. Try M57 or M27. I am an OSC (one shot color) guy so I've not done the red, green, blue filter thing. It looks like you will also be taking a "luminance" image which is done without any filter. You combine the four images and get color.

#8 Ekyprotic

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Posted 27 June 2013 - 06:24 AM

What would be a good range of scopes to have? I have SCT, MAK and refractors, have never owned a reflector in my life (I want something I can use for daytime imaging as well as night time)..... keep in mind the following would be with a DSI II Pro, DSI III Color, or LPI

1 Celestron 8 SE SCT..... without focal reducer 2032mm, with focal reducer/field flattener 1280mm, with 0.5x reducer 1016mm, with both together, 640mm

2. Meade ETX 90 MAK..... without focal reducer 1250mm, with 0.5x reducer, 625mm..... a lot of overlap with the SCT, but I could do L imaging with the DSI II Pro and RGB imaging with the DSI III Color simultaneously (I just need to adjust for the different apertures.)

3. Meade DS-90 refractor, without focal reducer 1000mm, with 0.5x reducer, 500mm

4,5. Meade ETX 60 refractors (2), without focal reducer 350mm, with 0.5x reducer (do I even want to try this), 175mm. I can do L imaging with the DSI II Pro and RGB imaging with the DSI III Color simultaneously with this set up.

I am in an area of very high light pollution near NYC so that needs to be factored into this. I also have an array of LP filters available to me, including Astronomik CLS, CLS-CCD, UHC and the Celestron O-3. I also have the regular LRGB filters for tricolor imaging.

#9 WarmWeatherGuy

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Posted 27 June 2013 - 07:35 AM

What would be a good range of scopes to have?


The guy in this book

The 100 Best Astrophotography Targets: A Monthly Guide for CCD Imaging with Amateur Telescopes
http://www.amazon.co...s/dp/1441906029

uses a 12" f/7 SCT for small targets like M57 (3 arcminutes), a 5.5" f/7 refractor, a 4" f/6 refractor, and a 3.5" f/4.5 refractor. These scopes have focal lengths of 2134mm, 978mm, 610mm, and 400mm. He uses the ST10XME and ST2000XM cameras.

You will want a similar range of field of views. Use this to calculate your field of view:

Field of view calculator
http://www.12dstring.me.uk/fov.htm

The book has 100 different photos and the field of view is given for each one. I would look at the pictures and decide which ones I would like to be able to take and then get the CCD / focal length combos that will give me those field of views.

Note that at f/7 you have twice as much light per pixel as f/10 so you cut your exposure time in half by using f/7 instead of f/10.

#10 Phil Sherman

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Posted 27 June 2013 - 09:00 AM

Thanks for the reply guys, now I really know what I'm getting into. However I would like to learn to use the equipment and I wouldn't want to buy a simpler/cheaper camera, telescope or whatever (I know it would be easier to learn, but it would be... a waste of money)
Anyway, thanks for the replies, I'm gonna get a focal reducer and will see what happens. I will also try photographing a globular cluster.
I have some more questions:
1. What kind of exposure times should I be using to photograph Andromeda? How many pictures?
2. Would it be better to use the HyperStar Lens that I already have?
3. The software I use is CCDOPS. How should I connect the camera to the telescope, so that when I try to move the telescope through CCDOPS (on my laptop) the telescope actually moves...
4. How do I get those beautiful colors you guys get... It definitely does not seem to me like I'm gonna get such a colorful picture like the ones I see, just by combining the 3 images with the red, blue and green filters? Am I wrong?

Thanks again, you guys are very helpful :)


If you have the hyperstar, then you should start your imaging using it. You'll be imaging with a very fast, short focal length scope with it, which will be better than the focal reducer.

Get or make a Bahtinov mask for focusing. You'll need to figure out a way to hold the mask in place when using the hyperstar; a dew shield should work to attach it with the camera mounted. You can generate your own mask using an online generator. I had mine printed at a local CopyMax because it was larger than my printer would do. They printed it on card stock, a lot sturdier than 20lb paper.
http://astrojargon.net/MaskGen.aspx
Focus on a nearby star first then shift targets to whatever you're imaging. your images will most likely be limited by sky fog, a consequence of our poor street lighting. Take a series of exposures, increasing the exposure time and look at the background brightness. When the background sky is 10-15% of the maximum value for a pixel's brightness, you've determined a good starting point for a "long" exposure. Don't be surprised if this is less than 30 seconds. I get sky fog with an f/5 scope with less than 30 seconds exposure when I'm imaging from home, an inner ring suburb of a major city.

Stacking multiple images is the way to reduce noise caused by multiple sources that are a consequence of digital electronics. Learn about using darks, flats, flat darks, and bias frames to make better images.

Phil

#11 WadeH237

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Posted 27 June 2013 - 02:26 PM

The advice that you are getting here is spot on.

I would just like to add that the CGE is a very good imaging mount, but the C14 pushes it to it's very limits. I would say that Hyperstar with a CGE1400 will work fine, but that's about all I'd recommend. Even with a conventional focal reducer, the C14 is just too much for imaging on a CGE.

Since you already have Hyperstar, by all means use it to get started. You will learn a lot with that setup. When you want to image with the camera at the back of the scope, find yourself a nice refractor in the 80mm to 102mm range. You won't be sorry. When you want to go with a long focal length, an 8" SCT is well within the CGE's comfort zone, with or without a focal reducer (but that C8 will probably be outside of your comfort zone for a while yet, hence the recommendation to use a factor first).

I hope that this helps,
-Wade

#12 Mike Phillips

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Posted 27 June 2013 - 07:59 PM

I too will be benefiting from this thread as I just purchased a SBIG STF-8300M! Thanks all!

Mike

#13 alpal

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Posted 28 June 2013 - 09:07 AM

Hi Kalox,
are you guiding the C14?
It is not easy to guide at 4 meters focal length.

Unless you have a mount & Off Axis Guider that can do that
then forget the rest.

#14 andysea

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Posted 28 June 2013 - 09:57 AM

I have never used the hyperstar but shooting at F2 sounds like a focusing nightmare....potentially.
The CFZ at that speed is 15 microns.
How do you guys focus and keep focus with that system?
I suppose a Robofocus is almost a necessity at that point correct?

#15 Calypte

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Posted 28 June 2013 - 11:35 AM

Dean Koenig shoots Hyperstar images with scopes set up in front of his shop (Starizona). The images he showed me when I visited in Nov '11 were very, very sharp as displayed on a huge Apple monitor. I don't know if those images were ones shot from his parking lot, a circumstance which implies that not a lot of time is wasted on focusing.

#16 Kalox

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Posted 28 June 2013 - 11:49 AM

Hey,

Thanks for the replies.
I have a few more questions though:

1. What difference would the Hyperstar Lens make? In terms of exposure time, field of view, focus and etc.
2. I'd like to guide using my camera's built-in second chip. However I can't really connect the camera to the telescope itself so that the camera (through CCDOPS) controls/moves the telescope - any ideas how to connect everything? Also, if I wanted to guide using the second chip of the camera how exactly would I do that?

Thanks again for the help everyone :)

#17 andysea

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Posted 28 June 2013 - 11:52 AM

Sorry I wasn't implying that it would take longer to focus a hyperstar. But perhaps it takes a more accurate focusing method than just a focus mask given that it's an f2 system.

#18 Warhen

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Posted 28 June 2013 - 02:36 PM

Kalox,
How about The New CCD Astronomy by Ron Wodaski, a great book still, the ultimate intro to CCD imaging. Check OPT or Amazon.

#19 WadeH237

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Posted 28 June 2013 - 03:06 PM

Hey,

Thanks for the replies.
I have a few more questions though:

1. What difference would the Hyperstar Lens make? In terms of exposure time, field of view, focus and etc.
2. I'd like to guide using my camera's built-in second chip. However I can't really connect the camera to the telescope itself so that the camera (through CCDOPS) controls/moves the telescope - any ideas how to connect everything? Also, if I wanted to guide using the second chip of the camera how exactly would I do that?

Thanks again for the help everyone :)


1) Much shorter exposure times, larger field of view, less focus tolerance (but still quite manageable). I've used Hyperstar on my CGE1400. It's a nice setup. I only moved away from it because I did not have a one-shot-color camera, and my filter wheel was not accurate enough to center the filters precisely enough on a change. I still have a Hyperstar for my C8, which I find a bit finicky for focus and collimation. The C14 was much more forgiving.

2) I am not familiar with CCDOPS. With most software, you have two options for getting guide commands from the mount. You can just use an ST-4 compatible guide cable to connect your camera's guide output directly to the mount's guide port. Alternatively, you may be able to have the guide software connect to the mount (ie. via ASCOM, etc) via a serial port and send pulse guide commands to the mount. That said, one of the main attractions of Hyperstar is that the exposures are usually short enough (30 to 120 seconds)' and the focal length short enough, that you don't need to guide at all.

-Wade

#20 Loden

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Posted 01 July 2013 - 10:48 PM

I think I may be qualified to help here. I own a Canon 60Da, and before that had an Orion Starshoot CCD monochrome with a color wheel. A couple of months ago I bought an SBIG STF-8300M with an 8 position color wheel. Having been all around the block, and run into some really impressive dead ends, I finally think I have the code cracked!

I strongly recommend you get Craig Stark’s Nebulosity and then follow his detailed instructions TO THE LETTER. I tried shortcutting with my first CCD and wound up dissatisfied. With my new SBIG, I took quite a while practicing, using precisely the steps he outlines, whether I thought I needed to or not!

My first target was a rock in my backyard. My scope has a center cap that can be removed for reduced light exposure and the rock was in the shade, about 35’ from my scope. Because of the high level of light I could shoot the images with less than a second exposure time, and could knock out ten exposures in as many seconds. After shooting ten exposures of LRGB (luminance plus three colors), I shot my flats, dark frames, and bias frames, exactly as he suggested. Then I very carefully (after several screwups) went through the pre-processing steps to remove noise, bias, and gradient. Then I stacked. Lo and behold the final color image was so detailed and revealed so much depth of color to that granite rock that the rock looked better on my computer screen than it did when I went out to look at it. And… there were some tiny white specks on that rock that I actually used my guide scope and PhD guiding to track. Only after mastering shooting mundane objects in my back yard did I start night shooting.

While I was practicing on that rock, I tried the various options available at each step. I probably spend a hundred hours or more imaging and processing that rock, but I had nothing to lose, and I could see what I was doing when I needed to fix things. I kept at it until the colors I wound up with were the real colors on that rock, just deeper and more detailed.

Early on, I suggest you target relatively bright nebula that you can get in your field of view. This time of year, the Ring Nebula is a good target. Get your tracking down cold, experiment often with various exposure times and filters. Learning is the objective, not great pictures. Those will come.

Some of my individual colors/frames looked a lot like your shot before I pre-processed them to get the noise out. For whatever it is worth, this journey so far has taken going on three years, and I finally am getting images that the better imagers in our club can’t find anything to complain about!

I found that having a written guide that is directly related to a very intuitive set of software is a great learning tool. Most of the books I got on this subject refer to several programs that I don’t have, and no two of them seemed to agree on the software to use! I eventually may move on to more sophisticated software, but in my humble opinion, Nebulosity is phenomenal for learning.






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