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Forum: Pentax K-1 & K-1 II 08-27-2020, 10:33 AM  
Astrotracer vs Tracking Mount
Posted By MossyRocks
Replies: 20
Views: 3,271
Ok, that makes more sense. One thought someone over in the astro group had was using an alt-az for the go-to ability, stopping it taking an astrotracer shot, then doing a go-to to the object again so it basically remains centered all the time. I'm not sure if that would get better results than manually reframing every few shots since you would lose a bunch of exposure time doing the go-to after each shot.
Forum: Pentax K-1 & K-1 II 08-27-2020, 07:45 AM  
Post your K-1 pictures!
Posted By Botanizer
Replies: 38,023
Views: 3,733,918
K-1 with 300mm f/4
Forum: Pentax K-1 & K-1 II 08-27-2020, 08:53 AM  
Post your K-1 pictures!
Posted By Mike.P®
Replies: 38,023
Views: 3,733,918
Sigma 180mm f/3.5 DG EX Macro


Wasp
by Mike.Pursey, on Flickr
Forum: Pentax K-1 & K-1 II 08-02-2020, 12:22 PM  
Question about compatibility of APSC-designed lenses with K-1
Posted By cometguy
Replies: 16
Views: 2,213
Yes, I've been able to see the comet on numerous nights. I only have a K10D (but am getting a K-1 Mk II soon) so I don't have the astrotracker feature and I just bought an iOptron ProGuider Pro clockdrive to mount my camera on (but it arrived in bright moonlight so haven't had a chance yet to really test it -- though it tracks stars well (I've tested it in moonlight, but no good pics of the comet).
Attached is a photo that I took of the comet before moonlight, perhaps 10 days ago, taken with my K10D camera and my DA 12-24-mm f/4 lens on a tripod (no tracking), exposure 20 seconds wide open; this photo is interesting because I caught a meteor up near the bowl of the Big Dipper, as well as the comet just above the central tree (taken overlooking the Atlantic Ocean from Gloucester, Massachusetts).
Forum: Pentax K-1 & K-1 II 08-20-2020, 07:28 PM  
Astrotracer vs Tracking Mount
Posted By Bob 256
Replies: 20
Views: 3,271
Tracking times for the Astrotracer are determined by three factors; magnification, the camera sensor's ability to slew (move), and the area of the sky being tracked.

When longer focal length lenses are used (higher magnification), edge tracking becomes almost as good as center tracking but the stars will move faster across the field so the sensor must slew faster. This uses up its range quicker so decreases the time allowed for tracking. Any tracking errors will also be magnified so tracking can worsen. Shorter focal length lenses don't require the sensor to slew as fast and for a given slew range, this results in the ability to track for longer times. Tracking errors are "de-magnified" so to speak and become less serious although now edge tracking can suffer more leading to poor tracking towards image edges (at the sensor, star images move at different rates towards the edges compared to the center field so it's impossible to accommodate all the star images and get good center and edge tracking).

Stars near the equator move faster than stars nearer the poles (whose fields also have rotation) so that has to be taken into account when determining how long a tracked exposure can last.

All this makes a table for a given camera a guide and not a spot-on reference.

With a tracking mount, tracking errors depend on how good the mount is, and how well it's set up. The best tracking comes with a high power guide scope and manual (or auto-guided) tracking corrections using a tracking mount but that's for the serious sky photographer using long lenses. Exposures using the latter technique can be hours long with good results.
Forum: Pentax K-1 & K-1 II 08-20-2020, 09:17 AM  
Astrotracer vs Tracking Mount
Posted By MossyRocks
Replies: 20
Views: 3,271
Probably not coma but geometric distortion and poor tracking with wide and ultra wide lenses is the likely cause.



The table you are looking for is this one that gives tracking time for the O-GPS1 which should match the inbuilt ability of the K-1. However for going after deep sky objects I find the provided tables to be on the optimistic side of things by a lot and often find that I can get good result at 1/4 the time suggested.

The astrotracer ability in the cameras that support it functions as an alt-az mount that also does field rotation. It is dependent on knowing your latitude fairly precisely (a +/- a few hundred meters north south is good enough), what cardinal direction the camera is pointed, and how it is oriented in relation to the center of the earth. It gets this info from the compass, level sensors, and GPS and then does a bunch of math to figure out how much to move the sensor. If you look at the tables for the O-GPS1 it gives times depending on declination however most people don't understand declination correctly. A declination of 90 degrees is not looking straight up into the sky at the zeniuth and a declination of 0 is not looking straight out at the horizon. Instead a declination of 90 degrees means that camera is point at the celestial pole and if you are in the norther hemisphere you would be very close to having polaris centered in the frame. A declination of 0 degrees means you would have the camera pointed along the celestial equator and a good object basically on it is the upper most star in Orion's belt which is really close. If you are pointed directly at the celestial pole all of the movement is rotational, and if you look at the tables you will find that point at a declinatio nof 90 always gives the longest tracking time and is independent of focal length. this makes sens as the movement in the frame is all angular speed and the sensor can only rotate so much so the time it takes the stars to rotate the most the sensor can is about 5 minutes. However if you are pointed along the celestial equator the movement is entirely linear so the linear speed of the stars is all that matters. Here focal length matters since with longer focal length lens things move across the frame faster which is why you see decreased tracking time with longer lenses. Depending on where you have the camera pointed between the celestial pole and celestial equator there will be varying amounts of linear and rotational movement needed for accurate tracking.

Now on to quirks of astrotracer beyond it being rather finicky to get calibrated well. The biggest one that comes to mind is that with wide and ultra wide lenses it will almost always produce some trailing in the corners. The only time when it wouldn't is when you have it pointed exactly at the celestial pole in which case it it is functioning as a equatorial mount with a very short tracking ability. The reason for the trailing is caused by 2 things. The first is the geometric distortion that these lenses have that tends to be worse in the corners and along the edge. This distortion causes the tracking to not be as accurate as you move from the center of the frame out to the edges and corners. The other issue is that these lenses cover such as huge area that the amount of rotational movement vs linear movement varies substantially across the frame such that as you move from the center of the frame the tracking gets worse. As mentioned before this isn't a problem when point at the celestial pole since all the movement in the frame is rotational, but if you point it at the celestial equator the movement of the sensor will be entirely linear but as you move away from the celestial equator there will be more of a rotational component to the star movement.


The nice thing is that with wide and ultra wide lenses the need for tracking is greatly diminished as you can get very good results using the rule of 200 (a better variation of the rule of 500) which basically says to use as your maximum untracked exposure time 200/(focal length). So with my 12mm lens I can use a 15 second exposure and get really good results, but in reality since the stars are so small in the frame found I can push it to 20s and still get pretty good results but at 30 I don't like the trails. With a 50mm lens I can do 4 seconds untracked, but with my 400mm I could only do .5s untracked. The reason to use 200 instead of 500 is that 500 was from the film era where reciprocity failure was a thing so it worked well enough, but 200 works better with modern digital sensors that don't suffer from reciprocity failure. However this still takes advantage of the fact that our sensors have a bayer mask on them and interpolate pixels and to get truly sub 1 pixel movement with things along the celestial equator you would have to use 50/(focal lenght) and I have done some shots like that with some really long glass just to see if it was possiable. I did some moon shots at f/20, 2000mm, ISO 100, and 1/40s that way because I could and the f/20 wasn't by choice but a results of the f/10 mirror lens and 2x convert in the mix so I could get it to mount and still achieve infinity focus.

I recently got a small equatorial and the 2 biggest benefits I've found with it are first that I don't have to recompose all the time. Once I get an object framed up with a short lens I just put the camera in continuous low shooting mode and filp the switch on one of my release cables and let it take pictures until I decide to pack up. The second benefit is that with playing around with getting a good polar alignment does take longer than calibrating astrotracer it doesnt' get thrown off by things like astrotracer does so I can get good alignment up in places like the Iron Range of northern MN where astrotracer never seems to get a good calibration or any other place with magnetic items or magnetic fields. With wider lenses like a 50mm one doesn't need even a very good polar alignment to get good results at 30s per shot as I found out the other day with my first real attempt. I do need to get an intervalometer so that I can go beyond 30 second exposures with it.

I still use astro tracer as my little equatorial can't support my big lenses by themselves so I either shoot untracked or using astrotracer with them. I use astrotracer all the time with my SMC A* 400/2.8 and will even throw the 1.4X-L converter in the mix to have a 560mm f/4 and have had astro tracer work great. Granted for deep sky objects I still am stacking and the tracking times to get good results are still pretty short but I can consistently get 20s shots at 400mm and 10s shots at 560mm all the time that don't shot any trailing. Eventually I will move up to also having a big equatorial that can support a 16lbs lens and the camera and other gear you hang off of it but for now I am still using astrotracer for the big glass. I often am running multiple cameras and the last time I was out I had the 12mm lens not tracking at all but continuously shooting 30 second shots so I could do a star trails image with Polaris and the milky way, a 50mm lens on the equatorial following Cassiopeia through the sky shooting continuous 30 second shots, and I was using astrotracer with my 400mm on Andromeda.
Forum: Pentax K-1 & K-1 II 08-20-2020, 09:01 AM  
Astrotracer vs Tracking Mount
Posted By kypfer
Replies: 20
Views: 3,271
Just a quick note regarding Astrotracer calibration accuracy ... from experience with the external O-GPS1 on my K-70, the results a lot more reliable if I calibrate and set up at least 10ft/3m away from my car and/or other adjacent magnetic metalwork such as garden furniture etc. I've no (known) experience with power-lines, overhead or otherwise, but would anticipate problems from them as well. A handheld compass, checked against the North Star, will give a good indication of any major influences in the immediate vicinity ;)
Forum: Pentax K-1 & K-1 II 08-20-2020, 08:46 AM  
Astrotracer vs Tracking Mount
Posted By Bob 256
Replies: 20
Views: 3,271
The issue of stars not tracking in the corners is due to the fact that moving the flat sensor can only accommodate an image that is mapped to a flat plane (and at that, only with a perfectly rectilinear lens). Stars basically map to a sphere and while tracking at the center of the field can be pretty good, the further away a star is from center field, the more error there will be in tracking. This is particularly seen with wide angle lenses where those errors greatly increase towards the edges. A tracking mount works differently and the field of the entire lens changes over time staying on the same sky area which means stars all across that field will be tracked. Even the widest angle lenses will work to the edges with a tracking mount (though there are still lens aberrations in play as previously mentioned but a good lens stopped down a bit will perform well). As you alluded, there is a certain amount of work involved in setting up a tracking mount in order to achieve its advantages. A polar scope helps in this regard and familiarity and experience makes the setup easier. Some trackers specifically designed for cameras are reasonably priced nowadays such as the Sky-Watcher or the iOptron.
Forum: Pentax K-1 & K-1 II 08-20-2020, 07:34 AM  
Astrotracer vs Tracking Mount
Posted By DeadJohn
Replies: 20
Views: 3,271
I've used the K-1 astrotracer, iOptron Skytracker (similar to Vixen Polarie), and larger telescope mounts.

The main limitation of the Pentax astrotracer for me is inconsistent calibration. The process is sometimes finicky. I can do a precise calibration, get bad tracking, redo the calibration the same way, and it mysteriously works better. The K-1 has been more reliable than the original K-5 plus hotshoe astrotracer accessory.

The main limitation of a Skytracker (or Polarie) is an extra item to buy, carry, and make sure batteries are charged. Aligning it has not been a problem; I can aim it near Polaris in the same amount of time as it would take to calibrate the astrotracer.

IMO the biggest advantage of any physical tracking mount over the astrotracer is for stacking sky images. The tracker keeps the camera aimed at the same target for every exposure. Stacking for widefield Milky Way shots, though, has become less important as camera sensors improved in low light. I rarely stack. (stacking is still needed with deep sky photos of tiny objects through telescopes, such as a single galaxy or nebula, but neither the astrotracer nor Polarie are designed for that)
Forum: Pentax K-1 & K-1 II 08-20-2020, 05:16 AM  
Astrotracer vs Tracking Mount
Posted By cdw2000
Replies: 20
Views: 3,271
I think you are referring to the "500 Rule". This website explains it: Use the 500 Rule for Astrophotography | Useful Chart to Avoid Star Trails

There is also a more complex rule that is said to apply better to digital cameras called the NPF Rule. This is also mentioned in the above article.


I have only used the Astrotracer so can't comment on your other question other to say that, even with the Astrotracer, its best to keep the exposure time as short as possible. I typically use a 60 second exposure with the Astrotracer.
Forum: Pentax K-1 & K-1 II 08-20-2020, 06:37 AM  
Astrotracer vs Tracking Mount
Posted By jgnfld
Replies: 20
Views: 3,271
ANY x-y mount (whether internal as with the Astrotracer or external as a mount) will rotate w.r.t. the sky on a long exposure--think Foucault pendulum here which is the same basic principle at heart. There exist alt-az mounts that compensate by counter-rotating the sensor various ways, but a motorized equatorial mount is a much simpler solution. At lower latitudes, a simple barn door mount (easily googled) is often a cheaper alternative--though motorizing them still adds bucks.

What stacking Astrotracer photos does is essentially provide the counter-rotation necessary to prevent edge trailing in software through some extra work on your part.
Forum: Pentax K-1 & K-1 II 08-04-2020, 12:16 AM  
Hiking with a K-1ii
Posted By Paul the Sunman
Replies: 74
Views: 8,465
I'm sticking with the f/2.8 (the weight doesn't worry me too much) but your choice is entirely understandable. Good luck with the f/4; it looks a great lens for outdoors.
Forum: Pentax K-1 & K-1 II 08-01-2020, 05:48 AM  
Post your K-1 pictures!
Posted By Franc
Replies: 38,023
Views: 3,733,918


taken with the dfa*85
Forum: Pentax K-1 & K-1 II 08-03-2020, 08:06 AM  
Focusing (magnifying the view)
Posted By Bob 256
Replies: 6
Views: 1,022
On some lenses, You need to switch to manual to engage the lens focusing mechanism which is disengaged from the focus ring otherwise. On those, it's probably more important to have the lens in the AF position (when not using MF) so if you accidentally turn the focus ring, you don't force the lens focusing motor to do something it may not want to do. It can also put a bit extra load on the focus motor if left in the MF position (the focus ring can be somewhat stiff on some lenses) when using the camera's AF. - just a good idea to have the lens and camera AF/MF selectors agree.
Forum: Pentax K-1 & K-1 II 08-03-2020, 07:45 AM  
Focusing (magnifying the view)
Posted By LsM
Replies: 6
Views: 1,022
Im not sure if im understanding correctly but i can digitally zoom in live view by simply clicking the ok button and using the rear dial as you have described.
Forum: Pentax K-1 & K-1 II 07-26-2020, 05:57 PM  
Post your K-1 pictures!
Posted By northcoastgreg
Replies: 38,023
Views: 3,733,918
Thanks. Your comments much appreciated. I do try for a natural look, with maybe just slightly better color and contrast. That's what seems to do best over at fineartamerica.com.

With the FA 80-320:

Forum: Pentax K-1 & K-1 II 07-24-2020, 07:21 AM  
Hiking with a K-1ii
Posted By texandrews
Replies: 74
Views: 8,465
Yes, I'll chime in and say that it's all about the pack and the straps. Unless you're loading up with a lot of other stuff, I would think that your weight would be 9kg or less. A good pack carries that very comfortably, especially if you are not in a hot climate. Heat and humidity make even sitting still miserable.

On the tripod front, I highly recommend Acratech ballheads---best grip for the weight. Not cheap, but very durable.
The legs....I have an older model Feisol 3224, which had the best combo of compact/weight/height. But with a lightweight tripod, in windy situations you've just got to weight the tripod, either with a fillable weight bag or with the pack. And this is very important: whatever is used for weight MUST be in contact with the ground!

Love the Dales, btw.
Forum: Pentax K-1 & K-1 II 07-24-2020, 09:44 AM  
Hiking with a K-1ii
Posted By normhead
Replies: 74
Views: 8,465
We haven't done real hike in years, we walk through the bush all the time. My preferred kit is the K-1, DA 55-300 PLM and DA 28-105. That covers pretty much everything. IF I think they might be needed I'll bring the DA* 55 1.4 and 100 macro as well as the 1.4x TC. I have light weight tripods as well, but rarely bring one on a longer hike.

We did do a 19 day canoe trip, which is different from hiking in that most of the time the gear is in the boat, we aren't carrying it. But we do carry the camera gear up to 4 km a day, along with the rest of our stuff.

Lots more info here.
A few shots from our 19 Day summer canoe trip, and a link to Tess's trip report. - PentaxForums.com
Forum: Pentax K-1 & K-1 II 07-24-2020, 03:24 AM  
Hiking with a K-1ii
Posted By 3by2
Replies: 74
Views: 8,465
I think I'd separate things out into hiking and photography. I've walked a lot in the Lakes, Wales and Scotland. I generally carry an SLR with a single lens on in a hip pouch. I don't think I'd go out taking landscapes without a specific purpose and aim in mind having already scouted what i wanted and consulted the Ephemeris, ymmv.

I tend these days to use an Osprey back pack and carry any gear in separate pouches, jjc ones, which fit in around other stuff. I'll also carry stuff on a hip belt, an old CCS one though jjc and others do more modern ones. I've tried one of these blended Lowe packs, camera/rucksack thing. Awful beast, the worst of both worlds so I prefer a normal rucksack.

If I carry a tripod, it's the travel kind, with a hook to hang your bag on for stability. I also keep a Manfrotto MP3 on the bottom of my camera which is a superb little thing but it will only work with a small prime or small tele like the DFA 100 WR, saves balancing your camera on a rock. I don't carry a tripod unless I know I'm going to use it.

I've never found the perfect combo, I don't think there is one. I think most of us have different bags and kit for different purposes and we all have to find what works for us.
Forum: Pentax K-1 & K-1 II 07-24-2020, 01:47 AM  
Hiking with a K-1ii
Posted By noelpolar
Replies: 74
Views: 8,465
Wish I could paint (or play a piano).... anyway I guess I don't hike.... just sorta disappear for hours and hours in the bush.... I find setting out with goals just a bit too organised for my liking.... my idea of organised is to ... have coffee with me.
Forum: Pentax K-1 & K-1 II 07-23-2020, 03:46 PM  
Hiking with a K-1ii
Posted By photoptimist
Replies: 74
Views: 8,465
I hike with the K-1 with 7 lenses but no tripod (between SR and the high-ISO abilities of the K-1, a tripod is not required and takes too long to deploy when hiking with friends).

Monday's hike was 18 miles, 2,500 feet total elevation change in the Rocky Mountains to up to a glacial valley shown below. Carrying the K-1 can make the arms sore the first few times, but the body adapts to the load fairly quickly.

Forum: Pentax K-1 & K-1 II 07-23-2020, 03:21 PM  
Hiking with a K-1ii
Posted By gatorguy
Replies: 74
Views: 8,465
Yeah, my 10 mile+ hikes are going to be rare anymore. When I refer to a hike on weekends its more of the 3-7 mile variety. I think there was one 12 mile hike early last year but otherwise...

EDIT: With all that said my hike a couple weeks ago was about 5 miles, carrying a K1 and Sigma 70-200 on one hip, a K-70 with DFA100 on the other, plus an HD DFA50 and DA12-24 in the bag. I'm north of 65 so you kids should be just fine. :)

Go on and get out of the house, go play.
Forum: Photographic Technique 07-21-2020, 06:12 AM  
Astro Interval shooting and the camera's buffer.
Posted By DeadJohn
Replies: 15
Views: 1,536
That's a very good learning step. Star trails can often be done when sky conditions are less than optimal, such as some clouds or light pollution.


You can also use those images to create a single still image with the stars forming curves. Photoshop can do it, but StarStax is much easier StarStaX – Markus Enzweiler
Forum: Photographic Technique 07-20-2020, 01:16 PM  
Astro Interval shooting and the camera's buffer.
Posted By MossyRocks
Replies: 15
Views: 1,536
I figured they would show what is doable and at least the results I get. In the description on their respective page I have the info on what camera, lens, iso, shutter speed and I think even the f-stop that was used. One was shot with a 50mm and I think a 4s shutter and the other was shot with a 28mm and 10s shutter if I remember correctly.
Forum: Photographic Technique 07-20-2020, 12:20 PM  
Astro Interval shooting and the camera's buffer.
Posted By MossyRocks
Replies: 15
Views: 1,536
I don't have the K-1 but with my K-3, K-3ii, and K-500 when I do things like that I just put the camera in manual mode with a drive mode of continuous fast, connect my release cable and flip the switch. I've never hit the buffer with exposures longer than a few seconds, at 1 or 2 seconds I likely would, but at and beyond 4s I've never had a problem. I've done 2+hour night time lapses that way several times and not had a problem.

I see that the mention of dark frames has been brought up and my advise there is to turn it off in camera. Instead take your own dark frames at the end of the session and take a bunch of them. Almost all astro image processing software supports dark frames and will combine and average out a pile of them giving a much truer representation of the systematic error which is then removed from each light frame. This produces much better results than the in camera dark frame subtraction. The reason for this is by averaging a bunch you drive the true random noise down dramatically which is actually surprisingly strong. So by driving the random noise in the darks down you are better able to correct just the systematic error instead of randomness. To overcome true random noise you just need a bunch of light shots which increase the signal to noise ratio. When I take dark frames I do so when tearing down and packing up which takes 10 to 15 minutes so I end up with around 60 to 75 darks (I am usually doing astrotracer shots of 20s). Be sure cover the view finder as well as have the lens cap on so you don't get light sneaking in and always take them at the same ISO and shutter speed as your light frames.

A couple of timelapses I did:















You Tube


















You Tube



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