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09-10-2010, 11:19 AM   #1
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Astrophotography with Pentax bodies: limitations?

Hi. I will probably be upgrading my K110D to the new K-5 when it comes out. I am thinking of doing some basic astrophotography and I'd like to know what I'm up against with Pentax and the CMOS sensors. I don't have a telescope, but I would like to do some star trail shots or some long exposures on an EQ mount. What are the limitations?

I have done some shots of the moon at 1200mm (300mm f/2.8 with two stacked 2x TC's) and they turned out real nice!

What are the limitation of doing what I have described above, and what are the limitations with more advanced astro (with a telescope)? I just want to know what I'm up against.

Thanks!

09-10-2010, 11:27 AM   #2
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There has been some interest as of late with Astrophotography. Here are a few of the threads from the last week that show some pics, software for stacking images etc. Basically, you don't need an expensive telescope to get into astrophotography;

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/113832-astrophotography.html

https://www.pentaxforums.com/forums/pentax-dslr-discussion/113178-astrophotography-2.html
09-10-2010, 01:00 PM   #3
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To expand a bit, has anyone 'nailed' space station in orbit?
09-10-2010, 05:55 PM   #4
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I am not sure exactly what kind of sensors do this but I know that the K200 was a favorite for star trail pictures because of the option to turn off noise reduction. When you get to advanced astrophotography, some cameras cannot turn this option off, so after a 30s exposure, the camera must take a 30s picture of blackness so it can cancel out the noise. With the K200, I can turn this option off, and take continous photos. Without this, trying to take multiple images of star trails leads to gaps.

That is just one aspect though, there are many more.

09-13-2010, 02:02 PM   #5
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Thanks! I appreciate your comments. They have been helpful.

I have read that CMOS sensors are not good for long exposures because of noise in long exposures. NR is not a solution because it can eliminate small/faint stars. How much of a problem is this.

How does DFS in long exposures impact the possibilities with astrophotography?

Thanks!
09-14-2010, 09:41 PM   #6
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Why I hint around with space station, seen number of times, horizon to horizon
maybe 3 minutes at most. Gives ideal and perhaps solution at star trail attempt in relatively short amount of time. kinda lets one build by expirience.
09-15-2010, 05:19 PM   #7
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QuoteOriginally posted by BillM Quote
To expand a bit, has anyone 'nailed' space station in orbit?
Yeah, I've definitely seen a photo of a space shuttle & ISS docked together taken by a DSLR from ground. I don't have it but it's probably on APOD somewhere.
09-15-2010, 05:22 PM   #8
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found it:
Astrophotography by Anthony Ayiomamitis

09-23-2010, 02:26 AM   #9
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Thanks Guido, have link for locator nasa provides for ISS and other satellites below.
As much as I thought about it never considered using sun for contrast.
Using locator for my location says 29th Sept. only date in month where I can
try(at night, no daytime transit). Someone, somewhere could have a great opp.
with moon phase such as it is now, and next few days as it wanes.
But after seeing this atmospheric interference is only thing standing in way.

NASA ISS & Satellite locator(from anywhere on our earth)

Human Space Flight (HSF) - Realtime Data

Thanks again Guido,only bigger thrill in seeing, is sharing
Best Regards,
Bill
09-23-2010, 07:47 AM   #10
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Astronomical Photography

I am only a newbie to these forums, but I do have a fair bit of experience with Astronomy. So I will answer part of your question as best I can. Without Googling it!

To get the best out of Astronomical Photography, you definately need a tripod with an Equitorial Mount. There is absolutely no other way around it. A motorised one is best, as that will allow you to track the object that you are attempting to capture. And give you much longer exposure times. The equitorial mount will need to be aligned north/south as well. Otherwise it will not track the stars correctly. I am assuming that you will be conducting your affairs outdoors. That will mean that you may be in a field or other environment where wind may be a deciding factor in the images that you obtain. To avoid this, weigh down the tripod with something heavy. But do this from the centre of the tripod, and not on the tripods feet. A bag of sand, or a bottle of water with a handle works best. Tied from the centre of the tripod, and hanging down to as close to the ground you can go, with out touching the ground. Gravity will then pull the whole of the tripod into the center of the globe. Making it much more stable. Avoid light polution like the plague. Especially nosey neighbours that want to see what you are doing outside with a camera, late at night. Download some astronomy freeware which will allow you to set your location, date, and time. There is also sattelite tracking freeware out there as well. If you get into it, or maybe even are, you can do what I have seen some people do. And that is to buy, or make, a mounting system that allows you to attach you camera directly to the telescope eyepiece. Or even a webcam for video captures. Buy a small penlight torch, and coat the lens with red tape. The red is so your "Seeing" is not ruined by white light. And it also allows you to continue working whilst you are taking a shot. Use insect repellant. And what ever you do, don't put your tripod right next to a present that your dog has just left for you in the middle of the night. You "Will" step in it! trust me on that!!!

Hope I have been of some help. TP.
09-23-2010, 07:54 AM   #11
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Star trails you should be ok if you used stacked images using almost any recent Pentax digital cam. As a single exposure: see comment below. Long exposures, it all depends on whether or not you can turn off DFS for bulb exposures longer than 30 seconds. There's still no definitive word on that with the K-5. If you can, that's your cam.
09-26-2010, 03:20 PM   #12
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I know it's impossible with my *istDs. The first shots are noise free. But after a while all you see is noise, even at ISO200 (can't go lower than that). Not sure about newer Pentax. And I think the *istDs uses a CCD sensor.
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