K5 Astrophotography

A clear sky with light cirrus and the Moon at a high elevation made me test the K5 for astrophotography. I used my Takahashi FS 128 (1040mm, f: 8.1) apo refractor at prime focus.

As expected, the Moon image (stack of 2 exposures at ISO 400) was very fine. The great surprise was the result of a stack of six 5sec exposures at ISO 12800 of the Orion Nebula which was still close to the light-polluted horizon with strong moonlight after I had finished the Moon photos.

The K5 performs beautifully, and I anticipate the results to be obtained in a dark clear sky.
Moon:





Orion Nebula:

Very, very cool! Can't believe you were able to take the second shot--just beautiful! Cindy
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What lens did you use for the orion nebula? i've been planning to do this myself. Did you use a normal tripod or was it on some kind of EQ mount?

--
Justin
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http://www.pentaxphotogallery/justinwatson

I think both shots are stunning.

Keep posting more.

Pete

--

The most remarkable thing about my mother is that for thirty years she served the family nothing but leftovers. The original meal has never been found.

• Calvin Trillin

Fantastic!

Please tell more about the lens!

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K5 / K20 / K10D/*istD
MZ5n/Z70/SF7/MESuper/MX/Spotmatic F
Pentax since Spotmatic F

Awesome work, both great but the nebula is great, would love to be able to shoot that myself. Hahah why is it whenever you think your kit is complete someone posts a shot that makes you want something new.
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Dale

Very nice. It's amazing how clean images at high ISO can be from the K-5.
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Mike Herdering
http://www.mcherderingphotography.com

Does stacking help in anything other then noise?
--
Mike from Canada

'I like to think so far outside the box that it would require a telephoto lens just to see the box!' ~ 'My Quote '



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I have no idea how you did these (even though you said how).
But they are both great - I especially like the moon photo.

We done!

Xon

Oops, my above post was supposed to be posted to the original poster's post.

D'oh!

Xon

Great! Thanks for sharing.

--
reygon
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Take nothing but photos... Kill nothing but time... Leave nothing but footprints...

Your moon shot is OUTSTANDING (the Tak just might have something to do with how well it turned out)!
Orion is guided or unguided? For a 12.8K iso i'm impressed!

Ray

Thank you all for your kind comments ! Here is some information regarding the photos:

The Takahashi is a very fine apochromatic refractor. Its lens consists of only 2 elements, one of which is made of calcium fluorite that allows an optimal correction of chromatic aberration. The FS 128 has an opening of 128mm with a focal length of 1040mm (effictively f:8.1). It is mounted on an equatorial mount (EM) that compensates for the Earth's rotation. But, with exposures of 1 to 5 seconds made possible by high ISO values, an EM is hardly necessary.

The Moon photo was made at 1/500 sec with ISO 400 and Manual Settings. The shutter was actuated with the 2 sec delay so as to minimize vibrations. I stacked 2 images, but the individual images were just as good. The most important thing is the possibility to focus precisely thanks to live-view at 10x. Very good photos can also be made with a long telephoto (> 300mm) and a steady tripod. Choose the diaphragm for which the lens performs best - and experiment with settings.

The Orion Nebula results surprised me by their quality... The K5 gives very clean images at high ISO without artefacts such as banding. You get something akin to "granularity" of high sensitivity film, which is statistical "noise". That can be reduced by stacking images. The noise is averaged out. The beauty of the electronic captors is their lack of "reciprocity failure" at low light levels, and the possibility of going to high ISO values with the newer devices. The Orion photo was taken under very "bad" conditions: my balcony with suburban light-pollution, bright moonlight, and Orion was also fairly low on the horizon. The exposures were just 5 sec long at ISO 12800. Here too, live-view is essential for precise focussing.

The original exposures are quite "grainy". But the stacked image (I used the JPG images for the test - the raw images would be better) is much less noisy. I then used "auto tone" in photoshop to clean up the "fog" in the image and deepened the black tones with "selective color" under Mode> Adjustments. Finally, I applied Topaz Denoise with the "moderate" adjustment.

For stacking images, there is an excellent freeware program called "RegiStax" at:

http://www.astronomie.be/registax/

Its use is intuitive and it is useful - not only in astrophotography - for reducing noise and enhancing detail.

thanks for the info. I've used deep sky stacker to do stacking in the past. My issue was the number of shots needed and without an EQ mount i found it difficult.

But as you say the high iso capabilities means several 5 second exposures at a high iso will gather alot of light.

I'll see if there are any nebulas worth shooting with the DA*300 and AF 1.7x TC. that should be effectively 765mm including the crop factor....

--
Justin
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http://www.pentaxphotogallery/justinwatson

Second shot looks interesting.

Alan,

Takahashi are well-known for their fine telescopes. I haven't been in refractor-land since I sold my 4-inch Genesis some time ago, but I believe the Takahashi is a world-class instrument in the $5,000 plus class, if I'm not mistaken.

I still doodle around with my 9.5 inch Celestron, but haven't done any photo work in a long time. Your results encourage me to try again.

You're absolutely right about tracking, though. The need for tracking precision is greatly reduced or even eliminated with short exposures.

--
Mike

There are holes in the sky
Where the rain gets in,
But they're ever so small
That's why rain is thin. ....... Spike Milligan

Thank you for the explanation. How many images are stacked. Do you lessen noise in the camera or in photoshop. Is the camera screwed to the telescope.( mine over 15x eyepiece Quality fails) I have such a tube and how far from the eyepiece is the sensor, as this increases the effective mm of the exposure. Lastly which light ("star") of Orion is the nebulae? I have a pentax 250-600 lens with a doubler this will give me 1200mm. at F 11 and the 1.5 factor should give me 1800mm 35mm. I have not tried the moon or any body with the k5. I saw some pictures of Jupiter on this sight quite impressive.

dock said:

Thank you for the explanation. How many images are stacked. Do you lessen noise in the camera or in photoshop. Is the camera screwed to the telescope.( mine over 15x eyepiece Quality fails) I have such a tube and how far from the eyepiece is the sensor, as this increases the effective mm of the exposure. Lastly which light ("star") of Orion is the nebulae? I have a pentax 250-600 lens with a doubler this will give me 1200mm. at F 11 and the 1.5 factor should give me 1800mm 35mm. I have not tried the moon or any body with the k5. I saw some pictures of Jupiter on this sight quite impressive.

Click to expand...

NGC1999 is part of the "sword" in Orion If you draw a line between Rigel at bottom right and the left had star in Orion's belt which I think is Alnitak the the Orion Nebula is just to the left of that line. Orion is rich in objects that can be photographed and is certainly worth some time. In the Winter it is fairly low on the horizon. Later in the spring and summer it ascends higher and is a better target. This image is really good considering the conditions and how low it is at present.

One of my reasons for buying the K5 was to pair it with my scope and use it's high ISP capability. Just waiting till it gets warm enough to spend time outside currently it's -7!

dock said:

Thank you for the explanation. How many images are stacked. Do you lessen noise in the camera or in photoshop. Is the camera screwed to the telescope.( mine over 15x eyepiece Quality fails) I have such a tube and how far from the eyepiece is the sensor, as this increases the effective mm of the exposure. Lastly which light ("star") of Orion is the nebulae? I have a pentax 250-600 lens with a doubler this will give me 1200mm. at F 11 and the 1.5 factor should give me 1800mm 35mm. I have not tried the moon or any body with the k5. I saw some pictures of Jupiter on this sight quite impressive.

Click to expand...

The images are stacked separately (here by RegiStax). The stacking reduces random noise. Ideally, by a factor proportional to the square root of the number of images (e.g. 9 images reduce random noise by a factor 3). Sensors, however, are also subject to "readout noise" which behaves differently - so, the stacking is somewhat less efficient. You can then photoshop the resulting stacked image.

Quite generally, use as little glass as possible between the objective lens and the sensor. The inevitable defects add up to degrade the image. A focal doubler will only double the defects of the lens and reduce luminosity. Put the sensor at the prime focus when possible.

You should be able to get good Moon images at 600mm. You need to experiment with settings (exposure, diaphragm and ISO). The K5 handles 400 ISO quite well. The best F value will depend on your lens (usually 5.6 or 8). Short exposures are good for reducing blurring due to atmospheric turbulence.

You can also try for the Orion Nebula with 600mm (or less). In that case it is best to go to full aperture. Try exposures of about 5 seconds or less with ISO 6400 or 12800. You should be able to get decent images with a static camera on a sturdy tripod. Stacking will much improve the end result. And of course - do that with a dark sky!