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Astrophotography Equipment and Techniques

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posted on Jun, 6 2012 @ 10:26 AM
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Astrophotography has always fascinated me and I have seen some beautiful pictures and videos from ATS members with the latest installment in the ATS thread My Humble attempt at capturing Venus Transiting the Sun posted by Cohort. This is something I would like to get into for myself and be able to show to my 3yr old son as he grows up.

My question for all stargazers out there is what equipment do you use and do you have any tips, advice, or even guides for getting great pictures and videos?

Maybe we could use this thread as an astrophotography resource thread?

Thanks in advance for any info.




posted on Jun, 6 2012 @ 10:31 AM
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reply to post by LevelHeaded
 

Funnily enough I too became interested in this. I can't afford a telescope and probably wouldn't use it much if I did have one but it's still fun to have. Anyway, I came across this link which goes into quite some depth and detail and does give some recommendations for "My First Scope".
www.rocketroberts.com...
No affiliation to the site, I just googled one day when bored.



posted on Jun, 6 2012 @ 10:58 AM
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Here's my setup in alt-az mode.

And here's what it can do (when polar aligned, of course):

I would have put it to good use yesterday to photograph the transit as in 2004, but rain and clouds conspired to keep me from seeing it this time.
It's an 8" LX200 Classic with a piggybacked 80mm Orion ST-80 refractor. For cameras I have a Samsung SDC-435 for lunar/planetary/solar video (I use a type 2+ thousand oaks solar filter) as well as some deep space video as a secondary camera. For deep space video I primarily use a Mallincam Hyper Color Plus, which does a great job but lacks the resolution of an SLR.

The advantage is speed; what takes an hour to do with the SLR takes 60 seconds or less with the Mallincam. I can use it with either the Orion refractor for a wide field view which is necessary for large nebulae, or shoot through the main LX200 for a close-up shot of smaller objects.

For still shots at high resolution I use a Canon XTi SLR. That's what produced the image of the lagoon nebula posted above, which I shot through the Orion refractor while autoguiding through the LX200 using an Atik Titan-C and PHD on my laptop. Like the Mallincam, I can also swap the cameras so that I'm autoguiding through the refractor and imaging through the LX200. It all just depends on what my target is.

Last, but not least, this setup can also track satellites and see detail in ISS.

For bright satellites (like ISS) I use the Samsung camera and for dim satellites I use the Mallincam (though the latter is a recent acquisition, so I used to be stuck with the Samsung for all satellites). I also attach a Meade LPI webcam to the viewfinder by unscrewing the eyepiece and using small bungee cords wrapped around the camera and hooked onto the rings - cheap but effective. This gives me a two camera view, one through the viewfinder and one through the main scope, at the same time on the laptop. I use Brent Boshart's Satellite Tracker software to automatically track the satellites, which puts them into the viewfinder camera, and manually adjust it with the mouse until they land in the main camera view. To save on processor overhead, instead of rendering a crosshair in the computer's video window (which would be doable if I had a faster computer) I use a small piece of scotch tape to show me where to put the satellite in the viewfinder window to get into the main camera.

So there you have it, that's how I do astrophotography. I don't have the best equipment out there, but I've learned some tricks to make what I have work well. It's quite versatile and portable too; I can take it to a park and run the whole thing off an external power pack for a few hours if desired, which is important for astronomy outreach events.
edit on 6-6-2012 by ngchunter because: (no reason given)



posted on Jun, 6 2012 @ 10:59 AM
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reply to post by ngchunter
 


I can only drool over your setup



I have the Celestron 8" and a Lundt 60mm Ha telescope. For photography I use my Canon 7D for a wide angle, and for solar photography and planetary photography I use a Imaging source DMK camera. Whilst the 7D works great for white-light solar photography, I am less than happy about it on the Lundt. Somehow I can just squeeze a lot more detail from the DMK, which doesn't quite make sense to me, but on the other hand, it was more expensive than the Canon.....

For solar white-light photography I have a Baader filter over the Celestron, and I normally use a Baader Solar continuum filter in conjunction with that. I do mainly prime photography, and one day, when I'm big I'll splash out for a 14" Celestron with a Fastar attachment....

Last but not the least are the software. For planetary stuff I take mainly movies, and the stack the frames with Stacker, and do the final processing in MaximDL. I also have AIP4WIN software that I use every now and then.

Problem is, I now live in a flat in the city, so I cannot do a much astrophotography as what I would like, and 4 months of the year it is day without night over here...
I really wish I had a nice setup as what I have now when I lived in Africa, far away from city lights.
edit on 6/6/2012 by Hellhound604 because: (no reason given)



posted on Jun, 6 2012 @ 07:41 PM
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People usually assume that to do astrophotography you need a telescope and/or a star-tracking mount, but you don't need either for some targets.

You can get started with just a camera (DSLRs are preferable but old film cameras will still work if you want to keep initial costs low), a lens (some work better that others, but the relatively cheap 50mm F1.8 is a good starter lens), and a tripod (don't skimp on this - get a good one).

See Astrophotography Techniques by Jerry Lodriguss for lots of info on the subject and examples.

There is one other thing that you will need - access to dark (light-pollution free) skies if you want the best results, although you can sometimes get away with a less than perfect location, depending on your target and what you are trying to achieve.

I specialize in photographing meteors, and I currently use DSLRs and wide angle lenses for that purpose. Before DSLRs came along I used to use 35mm film cameras, but DSLRs make life a bit simpler in some respects so I made the switch to digital.

Here's a shot of Ursa Major (AKA "The Big Dipper") I took with a DSLR and a wide angle lens (I think I used a 35mm lens) mounted on a tripod. Note the reddish glow, especially in the distance, which was caused by light pollution. I'd have to check the exact details but the exposure would have been somewhere in the region of 10-15 seconds @ F1.8, ISO 1600.



posted on Jun, 7 2012 @ 01:50 AM
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reply to post by FireballStorm
 


Yes, you can start off very cheaply with just a SLR on a very simple tracking mount and get quite nice wide-field results.

here are simple instructions for a barndoor mount:
www.astunit.com...

a more sophisticated one:
www.astunit.com...



posted on Jun, 7 2012 @ 09:50 AM
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Thanks to all for the replies so far. Those pictures are wonderful and I hope to be able to show off images like that some day soon.

It seems that with just a some up front costs it's not to hard to get started. I already have a Nikon D5100 camera and and use Lightroom 4 for image processing. It sounds like I will just need to save up for the telescope, aux equipment and some frame stacking software.

So new questions for me, what would you recommend for a beginner telescope (type and size)? I'm nowhere ready for a setup like ngchunter (WOW!!) but would like to get something that I will not outgrow too quickly.

Hellhound mentioned some software called Stacker and MaximDL for image processing. Could we also include software used as part of the discussion? Are Stacker and MaximDL the standards used in astrophotography? Any other softwae recommendations?

Again, Thanks for the input and info...



posted on Jun, 7 2012 @ 10:16 AM
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reply to post by LevelHeaded
 


I try to save money wherever I can, so i use mostly free software for everything. For stacking I use Registax for planets/moon/sun/ISS, and Deep Sky Stacker for deep space images.
www.astronomie.be...
deepskystacker.free.fr...
For image editing I use PixInsight LE, which was a free version of PixInsight. Unfortunately they stopped providing the free version and claim it's illegal to distribute the previously-free version now, so I couldn't even give a link to it if I was able to find it, nor can I give it to anyone else (which is absurd imho, but whatever). PixInsight has some very nice tools specific to astrophotography, especially if you're taking high bit images (16 or 32 bit) and stacking them. PixInsight can not only allow you to edit levels, curves, all the usual stuff, but it has some interesting de-noising and sharpening algorithms as well as dynamic background subtraction to effectively cancel out any vignetting in the image. Unfortunately the full version is something like $300.

For telescope control I use Cartes du Ciel, which is free:
www.ap-i.net...



posted on Jun, 7 2012 @ 03:03 PM
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Originally posted by ngchunter
reply to post by LevelHeaded
 


I try to save money wherever I can, so i use mostly free software for everything. For stacking I use Registax for planets/moon/sun/ISS, and Deep Sky Stacker for deep space images.
www.astronomie.be...
deepskystacker.free.fr...
For image editing I use PixInsight LE, which was a free version of PixInsight. Unfortunately they stopped providing the free version and claim it's illegal to distribute the previously-free version now, so I couldn't even give a link to it if I was able to find it, nor can I give it to anyone else (which is absurd imho, but whatever). PixInsight has some very nice tools specific to astrophotography, especially if you're taking high bit images (16 or 32 bit) and stacking them. PixInsight can not only allow you to edit levels, curves, all the usual stuff, but it has some interesting de-noising and sharpening algorithms as well as dynamic background subtraction to effectively cancel out any vignetting in the image. Unfortunately the full version is something like $300.

For telescope control I use Cartes du Ciel, which is free:
www.ap-i.net...


I fully agree. The free astronomical applications are just wonderful. I know (and use) Registax, but sometimes I get better results with another stacking program, called AutoStakkert, but didn't know about Deep Sky Stacker. (Thanks for that tip). The rest of my image processing I split between MaximDL (not free), AIP4Win (Free if you buy the book on astronomical image processing
), and another freebee called ImageJ. ImageJ is actually a program that I use for processing pics that I take with my microscopes, but it makes a great astronomical image processing program too. I know I should be able to do everything with a single program, but I jump around too much between the software to learn any one in perfect detail. I did, and can get some great results, without reverting to any other imaging software by just using Matlab, (or the freeware version, SciLab), but that takes too much of a mental effort. (The older I get, the less I want to be bothered with spending days just learning software, I just want results. My bad, I know).



posted on Jun, 7 2012 @ 03:55 PM
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reply to post by Hellhound604
 


I forgot about imageJ, good recommendation. I usually use it for my job, but sometimes I'll use it for raw fits files in a pinch for quick preview purposes. It's a very lightweight program, which I love. Here's another free program I forgot to mention before, IRIS. Veeery handy tool to have, imho. It does a ton of things, it'll even handle astrometry and photometry with some effort. I mainly use it for its background subtraction capabilities (similar to PixInsight, but sometimes IRIS works better), but I can't even begin to list all the things it can do.
www.astrosurf.com...
Speaking of astrometry, here's what I use to astrometrically solve my images. I normally use the offline version in Linux locally, but you can also just use their website and upload your images for solving.
astrometry.net...
This software is absolutely awesome; it will solve virtually any image you give it as long as the image contains stars. If the image is extremely noisy, and I mean extremely, sometimes it won't solve properly, or if you only have a couple of stars in the picture it won't have enough to go on, but generally you just feed it an astronomical image containing stars and it will tell you the exact coordinates of the image.

Normally with most astrometry you need to specify things like your telescope's focal length, size of the imaging CCD, and the approximate coordinates you were pointed at, but not with this. It will solve it based on the image alone with no further human input. You can speed up the solution by specifying the width of the field of view, approximate coordinates, etc, but you don't have to. Even very high focal length/narrow field of view images can be solved without a problem.

Once you have the solution from the astrometry software, whether running it locally on your own computer or on the web, you can then use the "new fits file" it generates to examine the coordinates of any pixel within your image. For doing that I use this free program, you just open the fits file that the astrometry software refers to as the "new fits" image and then mouse over the spot of interest.
hea-www.harvard.edu...

Now why would you want astrometric data like that? Well there are many reasons, but one of the most common is to measure the orbit of an object in space. Once you have a series of astrometric measurements from a known location, you can calculate the orbit of an object. Measuring and plotting orbits is one of my bizarre interests, along with orbital mechanics. Combined with your own astrophotography you can measure the orbit of any solar system object you can see in your images simply by monitoring its position over time. Here's the program I use for measuring the orbits of objects beyond earth orbit:
www.projectpluto.com...
And for objects within earth orbit I use these two programs in combination with each other (last time I tried to download them the links seemed to be dead, so if anyone wants these just let me know and I'll send you the files):
satelliteorbitdetermination.com...
satelliteorbitdetermination.com...
You can also use this program to identify unknown satellites that appear in your images provided you know "when and where" it was for at least two points in space and time:
satelliteorbitdetermination.com...



posted on Jun, 8 2012 @ 03:44 PM
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reply to post by ngchunter
 


Interesting to see your telescope (in the pic) is not on a fixed pier. Do you have a permanent installation, or do you carry your stuff outside, and set it up when you need it?

In my old place in Africa, I had a permanent setup outside, but so often, I would get to my observatory the next night, and half of my stuff was gone
.....



posted on Jun, 8 2012 @ 04:35 PM
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Originally posted by Hellhound604
reply to post by ngchunter
 


Interesting to see your telescope (in the pic) is not on a fixed pier. Do you have a permanent installation, or do you carry your stuff outside, and set it up when you need it?

In my old place in Africa, I had a permanent setup outside, but so often, I would get to my observatory the next night, and half of my stuff was gone
.....


Yikes, that's terrible. No, I don't use a fixed pier, but I have a couple of regular observing sites whose locations are stored in memory (though at times I'll drive to an entirely different location either for an event or just to get out from under clouds). I do have to re-polar align each time I do deep space astrophotography, which I do using the iterative method. I've helped set up a few permanently mounted telescopes before, and for that I usually do a drift align since it only needs to be done once. I've used this software for that purpose and found it works pretty well if you're careful about camera image orientation vs eyepiece orientation:
wcs.ruthner.at...
One day I'd like to have my own permanent observatory, but in the meantime I'm getting plenty of practice doing rapid, accurate polar alignments.
edit on 8-6-2012 by ngchunter because: (no reason given)



posted on Jun, 12 2012 @ 11:17 AM
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reply to post by LevelHeaded
 


Firstly let me say an excellent choice of camera (guess what I've recently got
) Seriously though the sensor in the D5100 is the same as the D7000 and works very well at high iso's. Some may say that Nikon cameras don't do true RAW files but I've read that if the camera is switched off during processing (when the green light is on) it is cancelled... but this isn't the D5100 thread.



Originally posted by LevelHeaded So new questions for me, what would you recommend for a beginner telescope (type and size)?


This is a tricky one. Your choice of 'scope is a very personal one. Ask yourself: What do you like to observe? How portable does it need to be? Is it primarily for Astrophotography? What are your local sky conditions like? etc...

The quick and easy answer for beginning Astrophotography would be a GOOD QUALITY 6 - 8 inch Newtonian on a sturdy Equatorial mount (EQ5 +) with drives. A good all round workhorse but is it right for you?

All telescope types have their own pros and cons. Check out "Cloudynights" and other Astronomy forums for info and reviews also magazines like "Sky and Telescope". Please try to avoid looking on places like Ebay for bargains, it's very easy to buy a nice, brand new, shiny "lemon". I would always go to a "proper shop". 'Scopes look much more portable in photo's. I was considering a 6 inch f8 refractor till I saw it in the flesh.

For me, I like to observe and photograph the Moon. I live in a flat above a shop with a small backyard surrounded by fast food shops. The light pollution here is awful. I don't drive so dark skies are difficult. So a quality 5 1/2 inch (modified) Maksutov was my final choice. It's reasonably light weight and portable, long focal length and has a very flat sharp image plane (it wasn't cheap but I plotted and schemed for years to get it).

So... Good luck on your quest, I hope you find what you're looking for. To quote a well known 'scope manufacturer "There are good telescopes and cheap telescopes. There are no good cheap telescopes."

Here's what my baby does:

Mosaic/composite image.


Some crops.




These were taken with my old D40. I hope the D5100 can squeeze a bit more detail out (higher iso = faster shutter).
edit on 12/6/12 by cassegrain140 because: I'm dumb
edit on 12/6/12 by cassegrain140 because: spelling



posted on Jun, 12 2012 @ 11:46 AM
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Thanks for making this thread. I received a 12" Orion telescope for chrismas and I'm just getting started in learning how to use it.

The first thing I want to learn about is the lenses. It came with a 10mm lense which works great on the moon, but what size lense do I need to see Jupiter?

And then I'll need to learn how to connect my camera to the telescope.

I'm way behind you guys



posted on Jun, 12 2012 @ 12:09 PM
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reply to post by Julie Washington
 


If your camera is a DSLR you'll need an M42 and T2 type adapters, if it's a bridge/compact, "gizmos" are available to mount the camera looking down the eyepiece. I won't post links to vendors as it will likely break T&C. Hint: the name on your 'scope might be worth a google then photo accessories


As for Jupiter I'd stick with the 10mm on a 12 inch Newtonian perhaps a 4/6mm if the mirror is good and you've got really good seeing (steady sky/stars not twinkling). A 25mm and a 40mm for deep sky would be nice too.

p.s. You must have been on Santa's nice list.
edit on 12/6/12 by cassegrain140 because: still dumb



posted on Jun, 12 2012 @ 12:32 PM
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Hey LevelHeaded, i just got into astrophotography a couple months ago so i'm still a newbie myself. You dont need to break the bank to get good results. I use a Canon 1100d, which by the way is amazing for the amount of money you spend on it. Got mine for around £320. All i needed after that was a tripod which i picked up for less than £20, and i just use the 18-55mm lens that came with the camera. Heres a couple of the results-





What i didnt know when i first started this hobby is that the majority of the time you will have to edit your photos after but if you dont wank to fork out more money yet on the many different softwares out there, some of the free ones are just as good. A google serch will bring up plenty but i just use Windows Live Photo Gallery that came free on my laptop untill i can afford something better.

Right now i am saving for a 300mm lens so i can do some moon photography but after that i will be looking for an affordable but reliable telescope so i can hopefully start taking pics of planets and nebula ect. And then eventually when i know what i am doing and what to look for, i will upgrade all of my astro-gear and hopefully end up with something like ngchunters or cassigrains setup


Like i said, i would start out basic to make sure you are enjoying yourself first before you fork out a few thousand for a serious setup. Best of luck


Also, the settings i use - manual focus (dont think auto is possible), ISO of 1600, 3200 or 6400, exposure of 15-30 seconds (bulb if you want star trails) and appeture of f1.8-11. This probably all sounds like jiberish if you are not familiar with photography but after a while it clicks. Took me a couple of weeks haha you just have to play around with the settings to get used to what does what. Peace
edit on 12-6-2012 by iksose7 because: settings



posted on Jun, 12 2012 @ 01:58 PM
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Originally posted by cassegrain140
reply to post by Julie Washington
 


If your camera is a DSLR you'll need an M42 and T2 type adapters, if it's a bridge/compact, "gizmos" are available to mount the camera looking down the eyepiece. I won't post links to vendors as it will likely break T&C. Hint: the name on your 'scope might be worth a google then photo accessories


As for Jupiter I'd stick with the 10mm on a 12 inch Newtonian perhaps a 4/6mm if the mirror is good and you've got really good seeing (steady sky/stars not twinkling). A 25mm and a 40mm for deep sky would be nice too.

p.s. You must have been on Santa's nice list.
edit on 12/6/12 by cassegrain140 because: still dumb

\
Yes, I didn't even mention all the adapters. You get the normal T-ring that goes into your eyepiece, for prime-focus photography. You get others with a build-in Barlow lens (to give you 2x magnification at prime focus), but I've seen others that give you 1.6x or 3x.

Then you get a huge adapter that allows you to use your SLR through the eyepiece, and lots of other things. What you need depends on your telescope. If you have a fast Newtonian (F4.0 or F4.5) it won't be the best for planets, but you will get excellent wide field photos. (But on the other hand, the fast Newtonians have a very pronounced coma at the edge of the field). For planets you will have to use eyepiece-projection photography to get a large pricture (but the quality goes down) (For planets it is also the best to take a movie, and use a stacking program). Best is, first get yourself a T-adapter for your SLR, and first master prime photography, and progress from there. (just remember, that your photo's will never look as beautiful as those from Hubble, or ESO, or any of the other huge telescopes...)

Be prepared for lots of frustration and experimentation, and be aware that astronomy (and astrophotography) is a black hole for money.... You are never satisfied enough, and will always keep on getting new adapters and filters and then the tracking of your mount isn't good enough, or your mount vibrates too much under the weight of your equipment, and want a new mount, and so on....



posted on Jun, 12 2012 @ 03:17 PM
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Originally posted by Hellhound604
Yes, I didn't even mention all the adapters. You get the normal T-ring that goes into your eyepiece, for prime-focus photography. You get others with a build-in Barlow lens (to give you 2x magnification at prime focus), but I've seen others that give you 1.6x or 3x.

Oh, speaking of barlows. I use a shorty celestron ultima barlow that is spec'ed as a 2x, but you can milk a little more out of it by putting it farther from the camera's CCD. If you can increase the spacing you can increase the effective magnification even more. By using a longer series of adapters between my video cameras and the barlow (c-mount-to-t-thread, t-thread-to-1.25", rather than c-mount-to-1.25" directly) I can get the barlow to act more like a 3x than a 2x. Another way to do this with a catadioptric (like a schmidt-cassegrain or maksutov) is to put the barlow into the visual back of the telescope (the tube where the star diagonal usually goes) and then put the star diagonal into the barlow so that any accessory (whether an eyepiece or a camera) that you're using has more space between it and the barlow.

In any case I highly recommend prime focus photography whenever possible. I started off with eyepiece projection using cheap point and shoot cameras (as well as a film SLR way back in the day) and I feel like I could have saved myself considerable headache by going straight to prime focus had the accessories we have today been around back when I started.

For planetary photography I use my Samsung video camera, but any webcam-based imager will work nicely as well, something like a celestron NexImage. That's when that barlow will really come in handy. Stacking planetary/lunar images with Registax is a must imho, but can really work wonders. You're effectively able to average out atmospheric distortion with fast exposures and achieve nearly diffraction-limited images. To do it you need as many exposures as possible, and the easiest way to get that is with a video file from a video imager. If you get really obsessed you can even split a long video into chunks for stacking, then re-assemble them as a timelapse of planetary rotation:



For deep space photography, prime focus is an absolute must; you don't want any field distortion due to an eyepiece and you want every photon you can get so you want as little glass as possible between your CCD and the telescope. You also generally want to have the opposite of a barlow, a focal reducer. A wide variety of options exist, and on some schmidt-cassegrains you can even use a Hyperstar type system to remove the secondary mirror and turn your telescope into what is more or less a "schmidt-camera." That's probably too advanced for the purposes of this thread, but the bottom line is that you want to reduce the effective focal length rather than increase it. This will give you more wiggle room for periodic error so that your stars look more pinpoint, and decrease the f/ratio so that you need less time on each exposure to properly capture the details of dim nebulae and galaxies. You also need autoguiding and a very good polar alignment. Again, the options on how to do autoguiding are many and varied, but I prefer a separate guide scope and autoguiding camera as opposed to "off-axis" autoguiding which gives you a very narrow field of view and few stars to choose from to guide on.

Another poor man's tip for you; when I first started autoguiding I simply used my bungee corded Meade LPI strapped to the viewfinder as my "guide scope." It wasn't very sensitive, so I couldn't always find a suitably bright guide star for the LPI, but it was dirt cheap (as in, it cost absolutely nothing since I already had everything I needed). All you need is a cheap webcam based imager (Meade LPI, Neximage, or similar), some short bungee cords, and a viewfinder with about 50mm of aperture or more. Hook the webcam up to your laptop, load up PHD to autoguide (PHD stands for push here dummy www.stark-labs.com... ), connect the telescope to the computer, and then play with the settings in PHD a bit until you get nice round stars. It takes a little experimentation, but it works surprising well considering how cheap it is. The key is to make sure the bungee cords are pulled tight by loosening the viewfinder in its bracket, pulling it back to stretch the cords, then re-tighten. Be careful not to over-tighten, of course, but it should be snug. I use about 4 cords all wrapped around the camera at various angles.

The not-as-cheap version is to simply buy an autoguider with a small optic that's fairly small and easy to mount (www.optcorp.com... - performs the same as my idea, but "done right"), and the really-not-cheap-at-all version is to do what I eventually did and buy a full blown refractor, rings, and mounting bar. Cheaper is nice when you're just starting out though.



posted on Jun, 12 2012 @ 05:16 PM
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reply to post by ngchunter
 


LOL, about your use of bungee cords ..... I always use duck tape, and ALWAYS feel embarrassed about it (when other people look at my telescopes), but I guess bungee cords are tackier (but better) .....

Yes, I have focal reducer too that I use sometimes ....

For planetary work you need a camera with a small sensor, else you will have to revert to eyepiece projection, as the results are not exactly stellar (or should I say planetar?). So, for wide field work, you need your SLR with possible a focal reducer. A Scmidt-Cassegrain is slow (F8 or thereabouts, so you have a fairly long focal length). A focal reducer reduces your telescope's F-ratio to something that is more like that of a Newtonian. My photography of wide-field areas through a Newtonian were very nice (except for comas), whereas planets I always had to do with eye-piece projection.

With a Schmidt-cassegrain (or refractor) the opposite are true. With a SC you have to use a focal reducer for wide-field, but then, mounting your camera piggy-backed to your tracking telescope with a nice lens, (or on a barndoor mount) gives you the best very-wide angle photographs, without trying to reduce the focal length of your telescope, or getting frustrated with the comas from a Newtonian.

If you have a tracking mount, you get nicer images if you set your camera to a slowish ASA-ratio (ASA 400 works fine), take a lot of short-exposure pics (Couple of seconds) (to get rid of tracking inaccuracies), and stack those pics, but you have to take RAW pics, and then first process them before stacking. With my Canons I have found that the RAW processing in MaxImDL is not as good as what I get from the Canon software (but it might be because of operator error). If you take images at a high-ASA, you get pictures with a shorter exposure time, but your pics are also a lot noisier.
In the old film days it was a hit-or-miss affair. You (or at least I) didn't have access to a darkroom, to do the same things, so you had to take very long exposures (and the the film had reciprocal failure, which means you had to expose even longer), and then tracking and alignment issues became very pronounced. I spent months trying to get my old Newtonian to track accurate enough with long exposure pics, but were never successful. (I can't tell you how many films I have wasted). Nowadays it is really a lot easier.



posted on Jun, 12 2012 @ 05:40 PM
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Originally posted by Hellhound604
reply to post by ngchunter
 


LOL, about your use of bungee cords ..... I always use duck tape, and ALWAYS feel embarrassed about it (when other people look at my telescopes), but I guess bungee cords are tackier (but better) .....

Yes, I have focal reducer too that I use sometimes ....

For planetary work you need a camera with a small sensor, else you will have to revert to eyepiece projection, as the results are not exactly stellar (or should I say planetar?).

Well I think small pixels are the real key, but that often goes hand in hand with smaller sensors than what you find in deep space cameras.


So, for wide field work, you need your SLR with possible a focal reducer. A Scmidt-Cassegrain is slow (F8 or thereabouts, so you have a fairly long focal length). A focal reducer reduces your telescope's F-ratio to something that is more like that of a Newtonian. My photography of wide-field areas through a Newtonian were very nice (except for comas), whereas planets I always had to do with eye-piece projection.

With a Schmidt-cassegrain (or refractor) the opposite are true. With a SC you have to use a focal reducer for wide-field, but then, mounting your camera piggy-backed to your tracking telescope with a nice lens, (or on a barndoor mount) gives you the best very-wide angle photographs, without trying to reduce the focal length of your telescope, or getting frustrated with the comas from a Newtonian.

Very true, with my refractor I don't need to use a focal reducer most of the time, indeed I don't even have one for my SLR, which makes imaging through the main telescope quite demanding of good tracking for long exposures at f/10.


If you have a tracking mount, you get nicer images if you set your camera to a slowish ASA-ratio (ASA 400 works fine), take a lot of short-exposure pics (Couple of seconds) (to get rid of tracking inaccuracies), and stack those pics, but you have to take RAW pics, and then first process them before stacking. With my Canons I have found that the RAW processing in MaxImDL is not as good as what I get from the Canon software (but it might be because of operator error). If you take images at a high-ASA, you get pictures with a shorter exposure time, but your pics are also a lot noisier.

Well that's why you need to do good dark frame subtraction. I generally shoot at ISO 1600, the maximum on my camera, but as long as you take RAW images you can correct for the noise using dark frames. Just cover the sensor and take a series of exposures using the same exposure time you used for the pictures and at the same temperature (so don't bring the camera inside to take the dark frames, take them at the ambient temperature outside). You also need to take bias frames, which are just very short exposures (I usually use 1/200th of a second) again with the sensor covered. I usually use a 5 minute sub-exposure, so 5 minutes at ISO 1600 collects a lot of light. With proper calibration (bias frames, dark frames, etc) the results are quite nice. Deep Sky Stacker I mentioned above will automatically take all of your calibration images when it does the stacking. You should more or less ignore the preview image it generates at the end of the stacking, it doesn't know how to handle the levels of the histogram at all, but the actual file output is good. Just load it up in a program designed for high bit images like IRIS or ImageJ and adjust the levels yourself and you'll see it looks great compared to the noisy raw images.


In the old film days it was a hit-or-miss affair. You (or at least I) didn't have access to a darkroom, to do the same things, so you had to take very long exposures (and the the film had reciprocal failure, which means you had to expose even longer), and then tracking and alignment issues became very pronounced.

Absolutely. I was never able to perfect my film astrophotography technique, I only became good at it after switching to digital, but now that my overall astrophotography technique has much improved I'm tempted to return to film for an excursion just to see what I can do. Unfortunately film is dying and most of the good film emulsions are no longer manufactured.


I spent months trying to get my old Newtonian to track accurate enough with long exposure pics, but were never successful. (I can't tell you how many films I have wasted). Nowadays it is really a lot easier.

I was in the same boat, had an equatorially mounted Newtonian with a Minolta film SLR, never got a single good deep space picture out of it. Of course at that time I couldn't even dream of doing half the things I do with my telescope now.
edit on 12-6-2012 by ngchunter because: (no reason given)





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