Fellow Pentaxians.

I'm looking to achieve some decent star shots this summer when I'm out in Yellowstone.
Ideally I want to hit some wide angle shots of the MilkyWay and way to minimize my chance of introducing star trails.

I'm currently shooting with a K-30 and I have the Sigma 8-16 for my UWA...
Question is, I know I want wide and fast to get as much light as possible. at 8mm I'm f4.5.

I haven't seen any posts of astro using this lens... I wonder why?
Should I consider something faster and not so wide, such as a 16mm f2?

I figured the Sigma at 8mm would allow for roughly 40 second exposures using the rule of 500 (plus crop factor).


Another option I suppose would be the OGPS-1, (it works on the K-30, right?!)

But I'd rather make my gear work for me as is and not spend more money on things I may not need.


Let me know what you UWA Astrophotographers think!
Cheers!

I have the lens also, and have tried it. For star trails it is great. For star fields or the Milky Way, its is a bit slow. When coupled with the O-GPS unit, it will perform well, however any landscape elements within the frame will be blurred (due to the star tracking of the sensor). It's and excellent lens but is somewhat limited in this application.

Thanks!
What lens do you prefer for star field/ MilkyWay shots?

I am more into that style of shooting and wouldn't mind trading the Sigma 8-16 for a better fit lens...

I shy away from ultra wide unless I really need it for a foreground, otherwise the wider the FL, the tinier the stars will read. 15mm is ok for milky way and I often do a pano with the FA31, my favorite astro lens for mw shooting.

Here's one from this morning with the DA15 and O-GPS1

Stone House
K5 & DA15

nice mike......use a 28/2.8 sears for the longest time (fine with what I got) and a bower 14/2.8(recently acquired and really like it!) sometimes I will use 50/1.8 and even higher depending on what i'm trying to frame...the following uses K-r with 14mm and Olympus E-510 with 50/1.8

I can only echo what Mike has written. I spent most of last year learning what he just posted. I have also been sorting out post processing, trying to layer images together to reduce/eliminate the blur from the GPS.

I have also been doing a lot of reading and Canon/Nikon folks use relative short 15 to 30 second exposures with the Sigma 18-35/f1.8 producing some excellent results - with just a single shot. I have also tried a 25/2.8 and the results are good, but the 1.8 aperture is so much better. A few weeks ago I sprung for the 18-35 after thinking about it for 6 months (Milky Way season is Feb to October). Last weekend was the new moon, but it rained most of the weekend here. 18mm would be about the widest I would think would be reasonable for this.

So I thought the 8mm would be key for a single shot around 40 seconds... Maybe I should look into something not so wide and a bit faster?

What about the Samyang 16mm f2?

I've got a 50mm f1.7 I could try out too, never really thought of putting that to the test...

That was my first inclination last year when I started with astro. I thought that the GPS would make up for the slower lens in terms of gathering light. It does, but the wider lens brings in the landscape elements just because it is so wide. So with the landscape elements, you get the blurring, which puts you into this vicious circle of going a bit narrower in terms of field of view, faster lens, etc. It basically comes down to how you shoot with or without landscape elements, which determines the use of GPS, which affects the length of the exposure, which pushes you on the aperture.

I have read that the 16/2 is very good. I don't see a lot of difference between f1.8 and f2. You are still going to need to be at ISO 1600 to 3200. There is a difference between 16mm and 50mm. But go to the astro threads in the main forum body and you will see that folks are getting wonderful images at 135mm to 200mm of nebula and galaxy objects, using the GPS, taking multiple shots and stacking them. You can go up to 300 seconds with a 200mm lens. There is usually no worry about landscape elements, so it's a pure sky shot.

At 50mm you still should get general sky shots with lots of stars and other items. You will not have the definition of longer lenses, but you can still take multiple images and stack them for very interesting shots. I too have an A50/1.7 that I have not used in this way, but I think that it would be very useful and interesting to shoot into the heart of the Milky Way for say 10 shots at 300 seconds each and just stack them and see how it turns out.

Check out the following threads. They are both like 40+ pages long, loaded with tons of information and images...

• https://www.pentaxforums.com/forums/115-pentax-k-5/143409-k-5-astrophotography.html
• https://www.pentaxforums.com/forums/6-pentax-dslr-discussion/113178-astrophotography.html

Also, take a look at this link for what you can do with a 50mm lens....

• Photographing the Milky Way with a Smartphone and the Future of Photography – Lonely Speck

Practice a little bit at home to avoid wasting precious time at Yellowstone trying to learn astrophotography in the dark.

8mm is arguably too wide unless you include some foreground details. The Samyang 14/2.8 and 16/2.0 get good reviews for astrophotography.

You have a 50/1.7 lens? That's another option for tighter views of the Milky Way. You'll need either O-GPS1 (money), motorized tracker (more money), barn door tracker (cheaply built if you are handy), or stack (look up the free software Deep Sky Stacker).

For stacking, set your 50mm to f2.0 or maybe 2.8 if the lens shows coma distortion at the edges, around 4 second shutter, ISO 3200, then take 30 consecutive shots plus 8 "dark frames" at the same shutter speed. Each frame will look noisy if you push the exposure to enhance the Milky Way; stack first to reduce noise before brightening the final image.

Plus 1 for practicing at home. Especially manual focusing in LV mode - i thought i knew how until i tried it at night

Got a question. Let's say i've take a few pictures using the GPS device. Now i want to take a picture of the foreground with the GPS device off. But in the same orientation so i can stack/merge it with the astro photos such as Mike did, i assume
So how do i switch from GPS astrotracer mode to bulb mode in as graceful manner as possible. What i've been doing seems cumbersome but here it is:
1. Turn off astrotracer
2. Set K3 in bulb mode
3. Focus on foreground if possible/desired
4. Hook up cable trigger
5. Trigger the cable to start the exposure, manually time the exposure
6. Turn astrotracer back on again

Feels a lot more cumbersome than described. Any tips on getting that foreground shot for stacking??? Thank you!

Afternoon Phil,

I am thinking of going out this evening and shooting the MW, doing exactly this. Last weekend it was raining here. I'm also thinking that the process for the K3 is slightly different than my K5. What I do is...

• After shooting the stars,
• Via the menu, exit the GPS menu of the camera body
• On the K5, you are already in Bulb mode - and Manual Focus
• I lower my ISO from 3200 or 1600 down to something like 800 or 400 to get a better IQ, then shoot the landscape foreground
• I already have the external shutter release attached, so I just shoot for what every amount of time I desire. If the external shutter release has a timer, I can use that.
• Then I am done.

Last year I was experimenting with several packages for layering in the landscape. Topaz suggested that I use Elements, since it supports layering, and does a better job than their control package. I just picked it up on sale a couple of weeks ago, so I think I most of the items in place.

Also, as a side note - for manual focusing, on the way to the site, I stop down the road from the last real light source, and focus the lens on the camera (if its a AF with an undefined infinity area), or use one of my old lenses that has infinity at the end of the focus throw.

I'm tired and might be misunderstanding. Why do steps 1 & 6? Maybe the K-3 implements the astrotracer menu differently, but on my K-5 I have to dive into a menu to activate tracking. If I just use the shutter button or cable release while backed out of the GPS menu there's no tracking going on.

Perhaps it just the way I am using it, but in order to change the ISO you need to back all the way out of the GPS specific menu. That is one of my main irritations with the GPS (it would have been nice to just let folks to push the top ISO button and select a value). Last year I was trying to find the best ISO value to use, so I was changing it a lot. Also, to capture the landscape foreground, I lowered it to smooth out the noise, and to get a better IQ.

My mistake - I though that the comment was towards me.... Sorry.

I might also toss in, I crank up the ISO all the way to 51200 and take a 3 to 6 second shot (just counting to myself - nothing exact) to check the framing of the shot and the focus. Its really grainy, but it works very well. Its so dark out, that is the only way that I came up with to do a quick check of everything.

Greetings,

Like interested_observer mentionned just turn the gps off and you're in B mode, turn it back on and you're back in astrotracer mode (as long as "Action in B mode" from the gps menu is set to "astrotracer" and not "B"). Calibration information for the tracer is stored in the camera so you don't have to worry about recalibrating after turning the gps back on.

Stacking images with lots of foreground objects doesn't always work well with DSS. It will tolerate some but seems to get confused if you have a lot and produces multiple star images on some part of the picture. So when I try to do a picture with a foreground I usually don't stack. A 28 f/2.8 for 3 min at iso 1000 will reveal lots of details in the milky way. A 50 mm f/1.4 @ f/2.0 for 90 s at iso 1000 goes even deeper and makes nice pictures.

Good luck.

all i do is turn off the astrotracer and take the next shot. I was already shooting in Bulb mode for astrotracer and my cable release is my de facto method of triggering the shutter always. because i am wide, i am pretty much at infinity focus too, so no focusing. so, it is just the one step. way easy
good luck!