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08-13-2013, 11:21 AM - 1 Like   #466
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Got myself an Astrotrac TT320X-AG tracking module recently and have been familiarizing myself with the unit. An impressive piece of kit. I have ordered a geared head to attach the Astrotrac to since it will make polar aligning much easier. I also need a right angle eyepiece attachment for my camera so the targets near the zenith do not cause neck strain. I hang a jump starter battery by a bungee cord from the bottom of the center column of my tripod to stablize the setup. This also allows me two 12VDC outlets, one for the Astrotrac and another for my camera. The camera input has an inline voltage regulator to knock it down to the required 8.3VDC. Can't get much more portable. Many of the Perseids the past few days have been too faint to see with the unaided eye as you can hopefully see in the attached picture where one streaked top left to bottom right below M31. There must also be another meteor shower happening since I caught many faint ones coming in at right angles to the Perseids. Too many coming from the same direction for sporadics.

Jack

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Last edited by jbinpg; 08-13-2013 at 11:45 AM.
08-16-2013, 04:34 AM   #467
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There is just a nova brightening in Delphinus. I managed to get two photos on Aug 15 at 2100UTC with K-5 & oGps Astrotracer.
Picture no 1 135/2,8 35 s. ISO800 and picture 2 50/2,8 55 s.
The arrow of Sagitta is directed towards this nova! The brightness of the nova was 5,5 mag, it could be seen with naked eye. It is expected that the nova will brighten more during coming weeks.

Jorma Mantyla
Kangasala
Finland
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09-17-2013, 10:14 AM   #468
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I just recently purchased the O-GPS and will be giving it a chance to do some astrophotography once the midwest humidity level drops in the autumn and winter. I have a few decent lenses, but wonder whether the mirror lenses would be good. There are usually some used Tamron or Sigma 500mm-ish mirror lenses available. All things equal (like a decent tripod etc) would these be worth pursuing for said adventures?
09-17-2013, 01:21 PM   #469
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QuoteOriginally posted by TER-OR Quote
I just recently purchased the O-GPS and will be giving it a chance to do some astrophotography once the midwest humidity level drops in the autumn and winter. I have a few decent lenses, but wonder whether the mirror lenses would be good. There are usually some used Tamron or Sigma 500mm-ish mirror lenses available. All things equal (like a decent tripod etc) would these be worth pursuing for said adventures?
I wouldn't expect too much with any 500mm lens. The Tamron mirror lenses have fine, aberration free and sharp optics, (I use the 350mm f/5.6 , Model 06B myself), but for the 52B and 52BB lenses the long focal length as well as their relatively small f/8 aperture ratio speak against use with Astrotracer.

My own experiences are that success rate remains acceptable - just - up to some 300 - 400 mm focal length, (somewhat depending upon what one will accept as "acceptable").

https://www.pentaxforums.com/forums/pentax-camera-field-accessories/195236-pe...l-lenghts.html

09-18-2013, 05:25 AM   #470
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Thanks for that info.
09-27-2013, 02:27 PM   #471
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Astrotracer, Pentax DA* 200mm f/2.8 lens and Rear Converter A 2X-S

QuoteOriginally posted by TER-OR Quote
Thanks for that info.
I recently acquired the Rear Converter A 2X-S for my DA* 200mm f/2.8 lens. That lens needs to be stopped down to f/3.5 to produce reasonably round star images and thus, with my converter I now have a 400 mm f/7 system - not too far from the 500mm f/8 system discussed.

The other night, my (urban, light polluted) night sky finally cleared. Seeing was rather poor, but I still got some first results:


Southern part of constellation Lyra with M57, the Ring Nebula.
Downsized stack of 5 + 5 images at 15 sec exposure time; f/7; ISO 2000 and 4000 respectively.
Click to see larger (1280 px wide) version.

As said, seeing was poor - the brighter stars were litterally boiling at 8X magnification in Live View, but the following 100% crops are good enough to demonstrate what can be achieved with Astrotracer and a 400mm system - up to 15s of exposure time:


Star Beta Lyra and surroundings. 100% non-resized crop of the above image.


The Ring Nebula, M57. 100% non-resized crop of the above image.

As I have said before, I belive that 400mm and some 15-20 seconds of exposure time is about the upper sensible limit for Astrotracer. But, of course, there is only a little way to go up to the 500mm.............
09-28-2013, 08:47 PM   #472
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The stars are bright deep in the heart of Texas

I took this shot a few weeks ago and overlooked it until tonight. It was taken at the entry to a corral near Fort Griffin, Texas with the Pentax K5 IIs and the DA* 16-50mm. Post work was done in Lightroom and Photoshop CS6.

Any suggestions on how to get a better quality image would be appreciated. This a 20 second exposure at f/2.8 ISO 1600. I am still bothered by the amount of noise at these settings. Don't know a thing about stacking and my only logical conclusion would be to use a faster lens at a lower ISO. Am I wrong?

Noise reduction programs such as that in Topaz DeNoise and the noise reduction feature of Lightroom seem to blur details a bit too much for my taste.

I've just begun shooting the night sky in the last two months so I am sure there are tips and tricks I am unaware of.. share your secrets if you feel the urge.

Even at 20 seconds there are minute star trails, not all that noticeable unless you really pixel peep but short of using some kind of tracking mount I feel the best solution would be a faster lens.

I've seen similar shots in which the colors ranged anywhere from blue to almost red, I guess that is a personal choice and sometimes a result of ambient light from man made light pollution and atmospherics.

09-28-2013, 10:04 PM   #473
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Hi, Jim. What I notice in your shot is that the center stars are roundish and those near the edges are elongated. This is a sign of coma which may not be correctable to a great degree in a zoom lens, even a good one such as the 16-50. Astro photographers use gadgets called field flatteners on their scopes to take care of this. Primes are able to be coma-corrected more easily. You are correct that wider apertures will allow lower ISO to be used. However, you will need to find the sweet spot between maximum exposure length before star trails show up and ISO setting. Only with a tracking mount will it be possible to use ISO80 to great effect. I shoot my astro photos in raw but still set the WB to daylight. Then if I set a dark (hopefully) part of the sky to black, all the colours will fall in line. Nice photo, btw!

Jack

09-29-2013, 08:17 AM   #474
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QuoteOriginally posted by Jim Radcliffe Quote
...Any suggestions on how to get a better quality image would be appreciated....
Here are some tips that don't need a tracking mount or multi-exposure stacking software.

Consider reprocessing that image if you used RAW. The WB looks too blue, try changing WB to "daylight". Experiment with the exposure, highlight, shadow, black sliders to make the stars brighter on a dark gray background.

For future images, turn on "Slow Shutter Speed NR" in your camera. That takes a 2nd dark frame and stacks in-camera to reduce noise. Turn it off if you ever try timelapses of the night sky, though, because the dark frames will cause gaps between photos and drain your battery twice as fast.

Note that some of the "star trails" you are seeing are probably coma distortion instead. Coma stretches stars from the center to the corners and causes the brightest stars to look fan-shaped. Astrophotography-specific lens reviews talk about coma. Normal lens reviews rarely mention it because you don't notice coma in well lit photos. Fixed focal length lenses tend to show less coma than zooms but not always (my FA43 is otherwise great but has more coma than the kit zoom). The Rokinon/Samyang/Bower/etc 14mm/2.8 is popular for astrophotography but practice more with your existing lenses before buying something just for this. With some lenses, stopping down a little reduces coma but then you have to take longer exposures or boost ISO to compensate.
09-30-2013, 06:23 PM - 2 Likes   #475
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Jack & DeadJohn

Thanks for the input... and yes, I think most of my issues here are with coma rather than star trails as the stars in the center do not exhibit the "stretch" that those on edges present.

Here is one of those lucky shots that could have been so much better. A couple of weekends ago I was in the Wichita Mountains in Oklahoma shooting the Milky Way with a rock formation in the foreground when a meteor crossed. I was also painting with light at the time. Extremely lucky shot, just wish I knew more about what I was trying to do at the time.

This was a 20 second exposure with the Pentax K5 IIs and the DA* 16-50mm at f/2.8.

As for the blue color.. well, I am to blame for that.. while not technically correct, I found it appealing... still learning from my mistakes.



And I guess I should describe the kind of images I am interested in shooting. I want the earth and structures (man made or natural) to be a part of my photos such as the shot below of an abandoned bridge out in west Texas. Photos of this nature really appeal to me. I found this abandoned bridge by using Google Earth, literally hovering above and traveling back roads in an area in which I knew there would be a good dark sky in Google Earth.



Thanks again for the suggestions and info.

Last edited by Jim Radcliffe; 09-30-2013 at 09:23 PM. Reason: added additional photo
09-30-2013, 10:41 PM   #476
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Star Bridge is a stunner, Jim !! A worthy source of inspiration. Looking forward to more in this vein.

Jack
10-01-2013, 09:04 AM   #477
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QuoteOriginally posted by Jim Radcliffe Quote
Thanks for the input... and yes, I think most of my issues here are with coma rather than star trails as the stars in the center do not exhibit the "stretch" that those on edges present.

Here is one of those lucky shots that could have been so much better. A couple of weekends ago I was in the Wichita Mountains in Oklahoma shooting the Milky Way with a rock formation in the foreground when a meteor crossed. I was also painting with light at the time. Extremely lucky shot, just wish I knew more about what I was trying to do at the time.

This was a 20 second exposure with the Pentax K5 IIs and the DA* 16-50mm at f/2.8.

As for the blue color.. well, I am to blame for that.. while not technically correct, I found it appealing... still learning from my mistakes.



And I guess I should describe the kind of images I am interested in shooting. I want the earth and structures (man made or natural) to be a part of my photos such as the shot below of an abandoned bridge out in west Texas. Photos of this nature really appeal to me. I found this abandoned bridge by using Google Earth, literally hovering above and traveling back roads in an area in which I knew there would be a good dark sky in Google Earth.



Thanks again for the suggestions and info.
Nice shots! This is the kind of shot I'm generally after at night too. I like something to anchor the image to the earth for context.
That meteor shot was a great stroke of luck!
10-07-2013, 08:25 PM   #478
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Some pretty impressive shots coming out in here guys! I took a holiday during the long weekend here in Australia to a little town by the Ocean called Clairview in Queensland and set up the K5 at about 2am in the morning with the Sigma APO 70-200 F2.8 and Astrotracer - I took about 40 shots (everytime I had to move the camera I had to let the gps position recalibrate so got quite a few images with startrails) - I finally got lucky with the 2nd last shot!

Single shot @200mm F3.5, ISO2500, 15 seconds. Can see the running man too! I have made an enquiry about the "vacation package" for the astrotrac - the O-GPS isn't cutting it for me with it being very hit and miss at the best of times.

10-07-2013, 10:33 PM   #479
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Wow, nice!

I went out for meteors and the moon with Venus nearby tonight. Saw a big meteor but didn't catch it. Got some small ones.

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Draconid meteor & petroglyphs
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10-08-2013, 05:38 AM   #480
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QuoteOriginally posted by mattb123 Quote
Wow, nice!

I went out for meteors and the moon with Venus nearby tonight. Saw a big meteor but didn't catch it. Got some small ones.

K-5 & DA* 60-250



Draconid meteor & petroglyphs
K-5 & Rokinon 8mm f/3.5

Very nice shot!
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