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06-14-2014, 07:25 PM   #16
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Wow, that's professional and quite ingenious work you have done.

Flex is a constant problem for my reflectors. Not for visual, but with digital everything needs to be so precise. One would think I would have come up with better ways to manage it after building a dozen Newtonians, the biggest being a 16" dob. But I make everything from junk yard parts with PVC pipe and wood so they flex more than metal. Flex is one of the reasons why I'm keeping exposures short, so I don't trail.

Looking through the big astronomy thread, it seems some people are using the O-GPS1 thingy with their K5's and quite long lenses. These days I primarily use my ED80, ED100 and a small 6" F5 Newt for imaging, with maybe the GSO 8" F4 astrograph in the near future. Is there a way to integrate the O-GPS1 (if I had a K5) for use with these scopes? I have a Skywatcher HEQ5 pro goto mount with guidescope for tracking, but there's got to be a way to take advantage of Pentax's moving sensor to iron out the small amount of flex and tracking errors. From the menu in my K-x, it seems I can only use shake reduction in movie mode? Is there a way of doing this for time exposure on the K-x or K5?

This is me some 24 years ago grinding the 16" and some of the dobs I've built. 24 years.... where did the time go?

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06-14-2014, 07:31 PM   #17
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Wow. Biggest telescope I have is an 8 inch dob. I am jealous.

Also, with the pics I've seen that you take I can only imagine what you could get with my full spectrum K-01. The only thing I've had luck with is the moon, the sun, and some star fields with no objects at all.
06-14-2014, 08:30 PM   #18
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Don't succumb to aperture fever. It's too hard on an older body lol. These days I have reverse aperture fever, trying to get away with the smallest scope I can, which is why I like my ED100 refractor.

I have a full spectrum Nikon D70s, but it's waaay outdated now with amp glow and noise. I think what I need is a full spectrum K5.
06-14-2014, 09:05 PM   #19
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I saw where someone posted a heck of a deal on a K5iis in the price watch section. I don't think it is quite enough of an upgrade over my K5, but if I were still with my old Kx that would be incredibly tempting. The K-01 I have seems to have a little less noise than my K5, though my K5 definitely has more dynamic range. I can only imagine the K5iis converted to full spectrum for astrophotography. I've seen some decent stuff with astrotrace used, and so I have one on order. I just wish it would also work with the K-01 too.


I did see your pics and I have to say they are incredible. So far the only telescope I've tried using my cameras with is my 12 year old 130mm Meade reflector with the go to controls and tracking which I've never gotten to work right. I get bad CA with that. Any advice for a nokbie on astrophotography?

06-14-2014, 09:33 PM   #20
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Is that the Meade Star navigator 130? Being a reflector it shouldn't have any CA if you take photos at prime focus. If through the eyepiece then you may need a better eyepiece. Not being familiar with that model, I'm not sure if the focuser allows enough in travel for prime focus.

Looking at your signature, you have many fine lenses that you could do deep sky with. You just need a good EQ mount for them, something like the SW HEQ5. The greatest expense in deep sky astro is often the mount.

Having read the links from Interested_observer, I believe I now know why my Canon fiends are in the lead over my K-x. Bit depth and thermal noise are the two main culprits it seems. 14 bit rules for pulling detail out of shadows and yikes, that noise verses temperature photo is my downfall. Night temps here in the tropics hover near 30C for 9+ months of the year. I need a cooled, full spectrum K5 lol.
06-14-2014, 09:36 PM   #21
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That is some array of telescopes!!!!!!! And to build them also - my hat is off to you. About 10 years ago, when I decided to go into digital, I decided to go Pentax and just stay with them, come hell or highwater - just too much work and expense to change. With the advent of the GPS unit, for all intense purposes, the camera is it. Actually, I am having a pretty good time with it. Pentax's integration of the GPS with the sensor stabilization is wonderfully brilliant. The moment I heard about it, I knew how they did it. Just a re-purposing of the existing functionality with the GPS integrated in providing essentially guiding (in the blind). It knows where you are located on the earth's sphere and where you are pointing with its electronic compass. So in theory, it knows how the stars are going to move in reference to your current location and the section of the sky you are pointing at, and thus - it just assumes the opposite track - in order to maintain a relative stable view. That is all it does. Also, after about 4.5 minutes in wide field, you can start to see the stars beginning to make a circular track along the edges and in the corners. So, there are limitations to all of this - which is a function of the absolute distance the sensor is able to actually move).

I also spent quite a bit of time doing GPS systems on and off since 1975, so - I am having a difficult time trying figure out how you could integrate a K5 using the sensor stabilization/astrotracking within your telescope system. The K5 (and the other bodies) are integrated in to essentially a closed system. That is why folks use lenses, where the longer the focal length, the shorter the tracking period offered by astrotracker. At 300mm you are under a minute.

The most the K5 is going to be able to offer you when mounted to a telescope is the high ISO, with the 14 bit D/A and the clean 16MP sensor.

06-14-2014, 11:20 PM   #22
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QuoteOriginally posted by interested_observer Quote
The most the K5 is going to be able to offer you when mounted to a telescope is the high ISO, with the 14 bit D/A and the clean 16MP sensor.
Well, baby steps in improvement are better than none. I'll start saving for something from the K5 family. The lower, high ISO noise and 14 bit AD Converter will be worth it. And maybe mount a big fan on it.
06-15-2014, 03:36 AM   #23
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Good Morning,

Its 3am and I just got up for a drink of water (we are in the middle of the Sonoran Desert). In thinking about applying a astrotracking or tracing to telescopes there are two basic systems, the camera body would need to deal with....
  • Refactor - This would be the simplest, as the telescope would be a straight replacement for the lens. Just dial in the focal length (it would need to be a FL the body already knows about - i.e., something on its list). In this way, the camera body would just move its sensor (to the extent of its range of movement) to track the OUO (object under observation).
  • Reflector - This is the more complicated approach, and would need some software modifications - more user inputs. First due to the way that the camera is mounted on the tube, the GPS unit would not know the direction that it is pointing (it would be off by 90 degrees. Also, the elevation angle of the tube would be taken as a roll angle. Then the camera body would need to know the size of the mirror, since it would be tracking the OUO not across its sensor size, but across the face of the primary mirror. Also the tube would need to be unguided, and stationary (analogous to a fixed elevation Arecibo). The reason why the Pentax system works as well as it does, is that it is able to assume that all the inputs it is sampling are directly related to its own primary axis of observation, and it know the exact extent of the limits of movement of the sensor.
Also, just as a point of reference, I saw a K5 up on the Marketplace (here on the forum) for $350.



06-15-2014, 04:23 AM   #24
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Thanks for the observations io. Yeah I'm not sure I can integrate the GPS unit into my setup. That would have been a bonus, but it's okay if I can't. I have more traditional methods already in place for astro tracking with the HEQ5 goto and guidescope.

As much as I like the power of the bigger reflectors, the ED100 refractror is a pleasure to use. No collimation, easy setup, no flex, handles air currents well. It's weakness is a relatively slow native F ratio of 9, but I have a 0.8x focal reducer to take it to F7.2. Still slow though compared to faster Newtonians, hence the need for speed at the camera end. And if I get a good camera, I will get better pictures from all my scopes.
06-23-2014, 06:52 PM   #25
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Hi Kevin,

I have a K5 (just upgraded to the K3) that you can borrow to test out the performance if you like - the K5 is great for high ISO. I did a heap of Astro with the K5 and loved the results - the K3 is a little noisier at higher ISO due to more megapixels on the same sized sensor but still very usable. Here's a pic of Orion I got on the K5 + ED100 Skywatcher with NEQ6 Pro mount last November at Seaforth:



Cheers, Mike
06-23-2014, 08:00 PM   #26
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Hi Mike, nice M42!

Well I went and did it, I bought a used K-5. Low noise high ISO was the main deciding factor. Plus in time I will get the GPS unit for portable work. Getting it by EMS from Japan. Should be here this week hopefully!
06-23-2014, 08:26 PM   #27
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Awesome! You definitely won't be disappointed with the K5's performance. I have the O-GPS and it works quite well (when it decides to calibrate). It is a bit heavy on batteries though so make sure you keep plenty of rechargable AAA's with you.
06-23-2014, 11:46 PM   #28
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Thanks, I'll remember that when I eventually get one. Just getting the camera for starters.
06-24-2014, 12:10 AM   #29
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QuoteOriginally posted by interested_observer Quote
Reflector - This is the more complicated approach, and would need some software modifications - more user inputs. First due to the way that the camera is mounted on the tube, the GPS unit would not know the direction that it is pointing (it would be off by 90 degrees. Also, the elevation angle of the tube would be taken as a roll angle.
Would one of these solve that problem?

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06-24-2014, 04:05 AM   #30
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QuoteOriginally posted by weathermon Quote
Awesome! You definitely won't be disappointed with the K5's performance. I have the O-GPS and it works quite well (when it decides to calibrate). It is a bit heavy on batteries though so make sure you keep plenty of rechargable AAA's with you.
Well, so far for mine, it has calibrated right away without any problems. Knock on wood. I have been careful to not be near any large metal items - like a truck or car, and have a clear view overhead. Going back out Friday night to do some more shooting, so another opportunity to test it out.

QuoteOriginally posted by lytrytyr Quote
I believe Kevin is using a T mount on his telescope's tube. This would replace the T mount and then provide another couple of problems; 1) how to connect this to the telescope; and 2) if you were able to connect it, at best it would be aiming down rather than up, and that would mess up the compass heading used in the calculations. Re-thinking it a bit, depending on the diameter of the telescope's tube, you might be able to mount in heading in the right direction, but at a different elevation angle, but then you would have focusing problems - and the quality of light would have a large dropoff.

Good thought, but Pentax''s system is designed to be closed loop - camera and lens into a single assembly.

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