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12-01-2012, 01:13 AM   #1
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K-30 for Astrophotograpy

Hello, First time posting but have enjoyed reading so many great posts throughout the last couple of years.

Anyway, I currently own the Kx and I try to in all modest attempts (and I mean that literally) to take astro images, long exposure, or anything in the dark... Unfortunately, I live in light pollution purgatory, but that's another day and discussion I suppose.
I am considering the k-30 for astrophotography but can't really find to much about it online as I did in the past with the Kx. I'm wondering if anyone has any input or comparison. And also if the Pentax GPS module works with the K-30 and if it's worth the $.
I'm pretty sure it doesn't work with the Kx from what little I've read.


Thanks again for the great reads past and present, and in advance for any thoughts on this topic


Kenny

12-01-2012, 01:55 AM - 1 Like   #2
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The GPS module will work with the K-30, but you're right, it doesn't work with the K-x: only the K-r or newer.

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12-01-2012, 11:12 AM   #3
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Thanks Adam... Appreciate the input.
12-07-2012, 06:33 PM - 2 Likes   #4
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One example with the K30.

This picture was done with the K30, my Pentax 55-300mm DA-L lens and the O-GPS1 module. The camera was on a tripod in my backyard pointing to Orion and I took 3 pictures of about 1 minute and 30 seconds which was the longest I could expose at 300mm without getting elongated stars. I then combined the three pictures in Photoshop Elements using layers. Don't look at the moon, it wasn't there at the time, I just added it later. This is a printed picture that I scanned because I didn't keep the original files. I sold the GPS and am not doing astronomy anymore, this was only an experiment. This picture was taken on the south shore of Montreal where light pollution is horrible. I would have to travel about 50 miles south to get darker skies and it's too much trouble. Feel free to ask questions if you want. Take care.

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12-08-2012, 12:36 AM   #5
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QuoteOriginally posted by VE2CJW Quote
This picture was done with the K30, my Pentax 55-300mm DA-L lens and the O-GPS1 module. The camera was on a tripod in my backyard pointing to Orion and I took 3 pictures of about 1 minute and 30 seconds which was the longest I could expose at 300mm without getting elongated stars. I then combined the three pictures in Photoshop Elements using layers. Don't look at the moon, it wasn't there at the time, I just added it later. This is a printed picture that I scanned because I didn't keep the original files. I sold the GPS and am not doing astronomy anymore, this was only an experiment. This picture was taken on the south shore of Montreal where light pollution is horrible. I would have to travel about 50 miles south to get darker skies and it's too much trouble. Feel free to ask questions if you want. Take care.
Nice work! Is the GPS worth the money? And how does it work with astrophotography? Does it just show R/A and DEC coordinates or are celestial object programed. Lastly, is it worth a step up to a K-30 from a Kx for this sorta thing and just in general. Thanks in advance for the great advice!
12-08-2012, 12:41 AM   #6
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QuoteOriginally posted by kennyes Quote
Nice work! Is the GPS worth the money? And how does it work with astrophotography? Does it just show R/A and DEC coordinates or are celestial object programed. Lastly, is it worth a step up to a K-30 from a Kx for this sorta thing and just in general. Thanks in advance for the great advice!
Have you seen this?

Pentax O-GPS1 GPS Unit - Sample Astrophotography - PentaxForums.com

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12-08-2012, 03:05 AM   #7
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QuoteOriginally posted by Adam Quote
Thanks again Adam, I did not see this until your link. Very helpful... I'm just trying to figure out the best way for the budget. I as well live in light polluted skies, but want to do some artistic, nature stuff with long exposure. That being said I also want to do some astrophotography, but never could afford to and it just wasn't doable as a kid growing up in his back yard with a Dobsonian telescope. So I'm thinking the K-30. I currently have a used Pentax 18-250 DA lens and a Sigma 50-300mm lens. I just figured out that the 18-250 DA is not WR and I thought up until now that it was... My bad. As far as the K-30 I don't know if buying a weather proof camera is kinda silly with non weather resistant glass... Sorry to babble on so. This forum has been of great help!
12-08-2012, 09:23 AM   #8
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QuoteOriginally posted by kennyes Quote
Nice work! Is the GPS worth the money? And how does it work with astrophotography? Does it just show R/A and DEC coordinates or are celestial object programed. Lastly, is it worth a step up to a K-30 from a Kx for this sorta thing and just in general. Thanks in advance for the great advice!
Hi. The GPS is worth every penny for astrophotography since it can partly replace a costly telescope drive and it doesn't need a complicated setup like the drive. You just point the camera where you want to shoot and let go. It uses the shake reduction feature to move the sensor in the camera instead of moving the whole camera with a motorized drive. The allowed shutter time depends on the focal length of the lens used and the object angle over the horizon. You take as many pictures as you need and stack them in Photoshop or a special stacking program which you can get for free on the net. A picture at the zenith could last very long compared to one near the horizon. The GPS doesn't know anything about celestial coordinates, that's your job. It is there only to keep the stars from being elongated on the picture by following them for some time. I upgraded from the KR to the K30 for a lot of new features, one of which is a better liveview but it doesn't have anything to do with astrophotography for me but it could help a lot with that. Moving from a KX to a K30 is really worth it. Do a comparison on the dpreview web site which offers that feature.


Last edited by VE2CJW; 12-08-2012 at 09:57 AM.
12-08-2012, 10:07 AM   #9
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Another thing I tried was using a homemade bracket to hold my K30 on a tripod with the GPS and a Celestron Skyscout at the other end of the bracket. That way, I always knew where to point the whole setup because most of the time you can't see anything in the sky around here. The Skyscout always knows where anything is in the sky and you can then point the camera at the right location. The Skyscout does give you the celestial coordinates if you want them. I sold the whole shebang because it wasn't worth it to play with that around here with the level of light pollution we have. Another thing I hate is the cold and a lot of interesting celestial objects are available only in winter like Orion.
12-08-2012, 10:27 AM   #10
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Another idea.

I forgot to say that you don't have to use a regular lens on the camera. Any kind of telescope with a T-mount could be used. Some interesting models are those small f6 deep sky apochromatic scopes like the one shown below. The camera simply sees it as a standard manual lens and you focus at infinity. Tried that and it works very well even for terrestrial pictures in the daytime. Of course, the longer the focal length, the less time that the GPS can control exposure.
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12-08-2012, 02:30 PM   #11
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Wow! Hey thank you VE2CJW for the above. That pretty much answers all my questions. I'm sure I'll come up with more but you guys have been great! Thanks again...
01-10-2013, 04:26 AM   #12
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Looks like we might finally get some clear skies over Europe to try some astrophotography with the K-30. I thought it might be worth posting on here some useful information for people exploring the challenge of taking pictures.

Firstly in the digital age you can afford to take multiple exposures and stack them. This helps to reduce the noise in the images and bring out fainter details.

Star Trailing
Stars trail because of the rotation of the Earth. The extent to which star trailing becomes important depends on the lens you are using and where in the sky the object is. So we can make the following general observations:
  • An object on the celestial equator (e.g. the belt of Orion) will trail more quickly than an object near the celestial pole
  • The greater the focal length/zoom the less time you have before trailing becomes noticable
Using lens sizes for traditional 35mm film (you will need to adjust for the crop factor of the camera i..e 1.4 on the K-30) we have:
Lens --> Celestial Equator --> Celestial Pole
28mm --> 25s --> 90s
50mm --> 12s --> 50s
105mm --> 6s --> 25s
200mm --> 3s --> 12s
General Technique
Armed with this information we can add the following notes:
  • Use the lowest available focal ratio setting i.e. f/1.7 to f/4
  • While any ISO setting can be used up to around 3200, lower ISO will yield better results even if it means stacking a few more images.

Targets
Again using old lens settings so you will need to convert based on camera
  • Constellations-->50mm lens-->10 to 20 seconds
  • Planets in dark sky-->50 to 135mm-->4 to 20 seconds
  • Planets in twilight-->50 to 135 mm-->2 to 6 seconds
  • Star trails-->28 to 50mm-->5 to 60 minutes (definitely use a low ISO for this, no more than 400 otherwise background will saturate)

Other considerations
  • You might want to a dark current image to subtract electronic noise. To do this take a picture with the lens cap on with the identical settings used to take picture of the sky. Stacking software will do the rest.
  • Can also take a flat field image (effectively an out-of-focus image of the same area to remove variances in light response)

Not convinced?
The attached is an image taken this time last year of Orion with with my 10-year old Sony 4MP camera. Can't remember how many images were stacked but there are probably 20 or so 4 second exposures pieced together. Ultimately though, you have to experiment. Good pictures of the night sky are never captured by simply pointing, clicking and hoping - patience is a virtue.
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01-10-2013, 09:05 PM   #13
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You can also make your own sky tracker for very little cost ... A Beginner's Guide to DSLR Astrophotography
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