[brenski]

Hi, please excuse this post, but I'm completely new to Pentax cameras and (in particular) the Astrotracer functionality (all of my photography experience being Canon-based).

I've just purchased a Pentax K-3 II and I'm hoping to get some good astro imaging done.

Can anyone help with:
♦ Complete step-by-step setup for Astrotracer, including GPS, Bulb mode and imaging.
♦ I've read (somewhere) that configuring the lens is important, if so, why? and how is this done?
♦ Remote Android control of Camera

Any other settings required? ie white balance, colour etc?

thanks

[Bob 256]

You might find some help in this thread (see below). Post #2 has some good references. There are a lot of other Astrotracer related posts in this forum and you can search for them using the forum search tool. So far as I know, no one has written a definitive users manual which covers all Pentax cameras offering Astrotracer as a feature. That would be a good "Article" for this forum if someone out there has the knowledge and would consider it. However, by referring to the user manual and the various posts here, you can get a good start in using this beneficial Pentax tool.

https://www.pentaxforums.com/forums/210-pentax-k-3-iii/449261-using-k-3iii-a...-type-3-a.html

https://www.pentaxforums.com/forums/search.php?searchid=61032920&cx=partner-...&q=ASTROTracer

Typically (and I'm coming from a K-1 reference), the user switches the camera to bulb mode and does a calibration of the GPS system. The camera is typically used in manual mode, and lens f-stop is experimental depending on what is being captured (generally, you'll be working toward the wide open end of the f-stop range for a given lens). You may have to tell the camera what the lens focal length is if the camera can't read that itself. The camera is placed in Astrotracer mode (on mine using the 4-way pad) and an open-shutter time is set (again experimental). After getting an exposure, you can adjust f-stop/exposure time combinations to alter the next exposure. Note that there is a maximum time limit on exposures due to limits of sensor movement and this decreases as the focal length of the lens increases.

Taking astrophotos goes beyond using Astrotracer and can involve considerable post processing so take baby-steps and get familiar with what your camera can do and what area of astrophotography you want to master as you go.

[brenski]

thanks for that - really useful.

I do already do post-processing of astro images I take using my Evostar 72 ED. But, I've bought the K-3 II as a portable option for trips away etc.


What are the recommendations (or not) for taking dark frames?

What about Noise Reduction settings?

[MossyRocks]

Havign successfully used astrotracer with a K-3 and K-3ii hopefully I can offer some advise.

The general procedure for using it is:
1.camer on with the GPS on (I always have it on with my K-3ii so I forget what menu this is in)
2. Put the camera into bulb mode
3. Depending on what you had previously done in bulb mode it may be in regular bulb mode or in astrotracer mode. If in regular bubl mode press the green button to switch to astro tracer mode
4. Perform the coarse calibration under the GPS menu item
5. Perform the precise calibration under the astrotracer menu
6. Take a test shot and see what you get for trailing. For perspective with the GPS based astrotracer I can get 20s exposures all day with a 400mm lens along the celestial equator so a good calibration will scale with lens length so I would expect 40s at 200mm or 10s at 800mm.
7. if you are fairly close to getting no trails back the time off by 10s but if not redo the calibration process.

That is the ideal however there is a lot that can throw it off or things that can fail. Sure signs that a calibration has failed is when I haven't done the rotation through all 3 axis and it gives me a success message. When that happens redo what ever calibration you were doing. I also find that when doing calibrations going beyond the 180 degrees of movement helps and I probably am close to 210 to 240 degrees of rotation in each direction. Another thing that helps getting a good calibration is doing fairly quick smooth movements. The quick seems to help with the internal accelerometers getting good data and by smooth you really need to keep the movement to only 1 axis at a time. There are also times when you may not get it to calibrate correctly. Here move to a slightly different location or change the direction you are facing. Sometimes no matter what you do you will get bad tracking or it will fail to calibrate and this is usually caused by iron or magnetic fields so things like fence posts, your vehicle, buried power cables, nearby power transformers, electric motors, soil with excessive iron in it, etc.so try to get farther away from those things. The camera will also give you an estimate of how long it can track for and I have found that to be very optimistic and in reality using 1/4 the time suggested I find works better.

I see you asked about dark frames and noise reduction. Here I suggest turning off the incamera noise reduction as it is really doing single dark frame subtraction. Instead at the end of your shooting session take your own dark frames while you pack everything else up. I believe that all astro stacking programs will take dark frames and from them create a master dark (average of all the darks) and subtract that from each light. The master dark is a much better representation of the systematic error than a single dark so subtracting a master dark destroys less real data and removed a better representation of the systematic error. Also by taking darks at the end while packing up you capture more light frames while out actually running the camera for a given time. When taking dark frames you have the lens cap on but also cover the viewfinder so you don't get light sneaking in there as you pack up.

For an idea of what can be done with astrotracer this is what I manage with my K-3 using the O-GPS1 for astrotracer and my 400mm lens in the core 7 county Twin Cities metro area:

[Papa_Joe]

First of all I would like to express my utmost respect for the master of night photography on this forum, Mr. MossyRocks. You can't go wrong following his advice.


That said I would in addition to MossyRocks directions propose to also try not using darkframes at all, i.e. take some as suggested by MossyRocks and compute with and without darkframes. Compare, if there is a difference. Modern cameras, yes also a K-3ii, have quite good darkframe suppression allready. Read more:
https://clarkvision.com/articles/dark-current-suppression-technology/

[brenski]

Havign successfully used astrotracer with a K-3 and K-3ii hopefully I can offer some advise.

The general procedure for using it is:

For an idea of what can be done with astrotracer this is what I manage with my K-3 using the O-GPS1 for astrotracer and my 400mm lens in the core 7 county Twin Cities metro area:

First of all I would like to express my utmost respect for the master of night photography on this forum, Mr. MossyRocks. You can't go wrong following his advice.

thanks both. and Bob 256 - lots of really useful help for a new user there. fingers crossed for a clear sky this evening here.
The only lens I have for my K-3 II at the moment is a Hoya HMC F/3.5 200mm
I'll maybe set the thing pointed at Pleiades and Orion to begin with. See what it can capture.

[amrocha]

Oh, man, I am glad I found this thread by accident today. Thanks brenski for starting it.
MossyRock, thank you for all the info you've shared here. And what an amazing image of Orion you've presented us with. That is really impressive!
I will update my calibration procedures following your instructions. I've got an used K-3 a few months ago that I haven't had the chance to test with the O-GPS1 yet but hopefully will next weekend.
And Papa_Joe, you made me curious, so I will try to make that comparison on stacking with/without the dark frames.

If I may extend the topic here, can I ask you guys what software you recommend for stacking? I don't have experience with stacking, I only do singles, but I feel the need to improve to get better images.

[brenski]

If I may extend the topic here, can I ask you guys what software you recommend for stacking? I don't have experience with stacking, I only do singles, but I feel the need to improve to get better images.

generally I use Deep Sky Stacker, but Sequator also produces some good results. One thing about Sequator - you can create a landscape "mask" and just stack the sky - it has mixed results, but you may want to look into it.
There's also Siril which stacks as well.

All of the above are free, but at a cost Photoshop and Affinity Photo also have stacking functionality.

---------- Post added 02-15-23 at 12:59 PM ----------

hmm, well just did a couple of test shots:

7.69s @ 6400


8.9s @ 1600


stars definitely a little mishapen. maybe better GPS config required?

[gifthorse]

It looks to me like a focus issue not a motion issue.

[AstroDave]

stars definitely a little mishapen. maybe better GPS config required?

It looks to me like a focus issue not a motion issue.

Yeah - focus. Use zoomed live view (check the manual (available on line from Pentax if your "new" camera didn't come with one) on how to do this, if you are not familiar) on a bright star to get the focus (or use some light on the ground as far away as possible) and be sure that autofocus is turned off.

[MossyRocks]

I'll maybe set the thing pointed at Pleiades and Orion to begin with. See what it can capture.

Those are some great starter targets at 200mm. On orion you can get M42, running man, horsehead, and flame nebula all in the frame with ease. Here is what Pete_XL did with an old Pentax M 200/4 on his K-3.

hmm, well just did a couple of test shots:

stars definitely a little mishapen. maybe better GPS config required?

As others have said that looks like a focus issue. Do you have a Bahtinov mask that you can use to nail the focus?

can I ask you guys what software you recommend for stacking?

For free software on window you can use Deep Sky Stacker (DSS). I believe that Siril will run everywhere but I have never used it. I prefer Astro Pixel Processor (APP), but it is pay software (200 euros) but will run everywhere. I know others use Pixel Insight but that is also pay software. If you are doing night landscapes another option is Sequator which is free but runs on windows only and will only give the framing of a reference frame so no mosaics. Sequator can also do deep sky objects but I found it didn't do as good of a job as DSS but then both are free.

[MarkJerling]

Oh, man, I am glad I found this thread by accident today. Thanks brenski for starting it.
MossyRock, thank you for all the info you've shared here. And what an amazing image of Orion you've presented us with. That is really impressive!
I will update my calibration procedures following your instructions. I've got an used K-3 a few months ago that I haven't had the chance to test with the O-GPS1 yet but hopefully will next weekend.
And Papa_Joe, you made me curious, so I will try to make that comparison on stacking with/without the dark frames.

If I may extend the topic here, can I ask you guys what software you recommend for stacking? I don't have experience with stacking, I only do singles, but I feel the need to improve to get better images.

Here's a +1 from me. Fantastic thread and great post.

[brenski]

@gifthorse @AstroDave @MossyRocks thanks for the help,
yes, I use Bahtinov's with my Canon and SW Evostar.
Will have to dig out the 58mm Bahtinov and use it on the Hoya

One other question: Is the LCD meant to be "that dim"? Only stuff I see are really bright stars like Sirius and Rigel.
Other stuff just isn;t visible "on screen"

[gifthorse]

From your test shots, it looks like you have the Astrotracer set up and working. My routine is to turn the camera on and input the focal length. The focal length is important because that's how the Astrotracer knows how fast to move the sensor. Then I calibrate the Astrotracer. When that is completed I mount the camera on the tripod and compose the image. If you turn the camera off or it loses power, you will have to recalibrate the Astrotracer. For objects like the Pleiades or planets, I leave the noise reduction on. Noise reduction is just a dark frame for each exposure. For meteor showers, since I'm taking many exposures as quickly as possible, I'll turn off both high ISO and long exposure noise reduction. Stop down the lens a couple of stops. Very few lenses are sharp wide open and closing the aperture a little will sharpen the pinpoints. You're using Astrotracer so stopping down the lens a little isn't a problem. Use a remote shutter release if possible to prevent camera vibration. If you don't have a remote shutter release, use the 2 second self timer. Don't rely on the maximum exposure length the Astrotracer says you can have. The actual usable exposure will be less than that. The Astrotracer will easily handle 45 seconds for the Pleiades with a 200mm lens.




Something you need to be aware of if you are going to photograph night landscapes is that the Astrotracer moves the camera sensor to keep the stars aligned with the sensor. That means that the sensor moves relative to the foreground. Instead of star trails you'll wind up with foreground trails. It's very noticeable along the bottom edge of the image below. The stars and planet are sharp, the building in the lower right, not so much. The stars moved, the planet moved, the sensor, moved. The foreground? Motion blur.

[Bob 256]

...............................One other question: Is the LCD meant to be "that dim"? Only stuff I see are really bright stars like Sirius and Rigel.
Other stuff just isn;t visible "on screen"

What you see on the LCD isn't "stretched" so the darker parts are buried in black. If you use post processing, you can move the white point and center point of the curve to bring the darker portions up and make them visible. You would do this in an astro processing app or something like Photoshop or Lightroom. Ideally, you do this to your set of stacked frames after they are stacked (some stacker programs will do it). Unfortunately, most cameras are incapable of doing it for purposes of their LCD display.

This gets us into another topic and that is what ISO is best to use. Really high ISOs aren't good although you might think they would make the camera more sensitive and be an advantage. The problem with high ISOs is they can significantly decrease the dynamic range, allowing brighter portions to "blow out" and lose details. There is an ideal ISO for the type of shot (length of exposure) and the sensor you're using. 800 ISO is a good place to start. I think MossyRocks or someone here made a chart of the best ISO to use for Pentax cameras doing astro shots. Here is an article on choosing the best ISO though it's a bit dated. There are also some good presentations on YouTube concerning the best ISO choice (one added below).

https://skyandtelescope.org/astronomy-blogs/imaging-foundations-richard-wrig...rophotography/

Youtu.be

Youtu.be