[interested_observer]

For more general shooting the 15-30 is probably the best and easiest single lens solution at the wide end. At 111 degrees wide, it pretty much equals the Sigma 8-16 at 8mm (at 114 degrees field of view), and that should be more than sufficient. Astro Milky Way shooting is probably the most demanding in terms of collection of light, and I usually stitch anyway, so that would provide additional versatility. That would provide me with a single row capability. Sure, I realize I can shoot cropped lenses on the K1, but then you loose the overall collection of light. That brings up just how many lenses that need to be carried. I would like to keep it at 3 - with the smaller the better. Right now with say a 15-30, 43 and the 60-250 (with the baffle removed), 2 of the 3 are not lightweights. But those three would essentially do everything. I could pay for everything with a lens sale (8-16, 12-24, 18-35, Voigt 20, ZK 25, Contax 28 & 85). Just keep what I use.

[Jesse K1]

I have used the K1 extensively for about a year now. I primarily shoot low light and astrophotography. I use the K1 as a dedicated astro camera coupled with with an 8 inch SCT with a FL of 1280mm, a 7.1 inch maksutov casegrain with an FL of 2700mm and an 5 inch triplet APO refractor with a FL of 952mm. I've also an assortment of lenses some very old and some recent. I've tended to get the best astrophotography using astrotracer with my 35mm F1.4 rokinon and believe it or not a 135mm F2.8 old ass $15 second hand store quantaray film era lens, I think it was made in 1978. My Pentax D FA 28-105mm f/3.5-5.6 ED DC WR is surprisingly not nearly as good with astrotracer as the 135mm. I continue to experiment with astrotracer under varying circumstances with different lenses. What I've found is that indeed a compass calibration is helpfull when changing location, lens or tripod. Things that effect magnetic fields definitely have a negative impact on how long astrotracer can go without showing star trails. I've also noticed the cameras relative aim at the sky has a noticible effect on how well astrotracer does. If you point towards a part of the sky that has greater apparent motion than things don't go as well than if you chose a target closer to the south or northern horizon. I suspect that true lens focal length is critical to making astrotracer function properly. Some lenses are not actually at a stated FL depending on if the lens exibets pronounced focus breathing or lens elements are not in perfect position. I've often wished Pentax would include an option to input precise FL into astrotracer but so far only predesignated focal length are available for selection. I also think it's possible astrotracer could be implemented much better perhaps by someone who can gain access to the software that manages the astrotracer function. It would be totally sweet if you could select a few stars during live view to move the sensor in relation too, effectively autoguiding. I'd be interested to hear others stories of ideal lenses to use with astrotracer after all one of the best lenses I've found turned out to be an ancient $15 film era lens.

[wgosma]

Well I am back from Tenerife. I can tell you that the Pentax performed admirably as did the Irix lens. I used many different settings and used it with Astrotracer on and off as well as with the camera on a tracker. I used exposures up to 3 minutes. Used long exposure noise reduction on some shots and on others I didn't. Iso went as high as 6400 but no higher.
Skies were absolutely awesome up there.
I still have to look through all the files to see what worked best, but for now I can share one with you. which was a quick manupilation, so there still is probably a lot wrong with it, but I am really happy with it so far.
Thanks for looking and all of your helpful suggestions!

Peter

Nice Image....I recently acquired a 15 mm IRIX for my K-1 setup; never done any 'astro' shooting so now I'm inspired to got out and try my hand at it.
Thanks/Bill

[darkmunk]

The K1 astrotracer seems to have a rather limited interface, with no real guidance compared to the hot-shoe version. I'm probably missing something obvious, but I feel completely in the dark (sorry ) when I'm using it.
Essentially, I turn on gps, set the camera to bulb, calibrate the astrotracer, then just hope it's doing something.
I keep trying to shoot Orion as a test, but I'm still not satisfied. The shot below was taken hastily outside the house on the road, with the K1 and 300*, 1600 iso, and my finger on the shutter for 24 seconds! I got away with it just and it seemed to be tracking here, but other times the stars are streaks - notably last night with a remote release, from the comfort of my son's bedroom while he was on his computer - magnetic problems?

[photoptimist]

The K1 astrotracer seems to have a rather limited interface, with no real guidance compared to the hot-shoe version. I'm probably missing something obvious, but I feel completely in the dark (sorry ) when I'm using it.
Essentially, I turn on gps, set the camera to bulb, calibrate the astrotracer, then just hope it's doing something.
I keep trying to shoot Orion as a test, but I'm still not satisfied. The shot below was taken hastily outside the house on the road, with the K1 and 300*, 1600 iso, and my finger on the shutter for 24 seconds! I got away with it just and it seemed to be tracking here, but other times the stars are streaks - notably last night with a remote release, from the comfort of my son's bedroom while he was on his computer - magnetic problems?

Nice image!

Are you sure it's not "finger-on-the-button" problems with the shot-to-shot variations?

If you have the latest firmware on the K-1, Bulb mode now has a feature that lets you set exposures of up to 5 minutes. (Note that the K-1 manual claims this was always the case for Astrotracer.)

Shooting indoors would bring magnetic problems, floor stability problems (unless the floor is concrete), and weird atmospheric ripples if hot air is escaping the house through the open window.

[darkmunk]

Nice image!

Are you sure it's not "finger-on-the-button" problems with the shot-to-shot variations?

If you have the latest firmware on the K-1, Bulb mode now has a feature that lets you set exposures of up to 5 minutes. (Note that the K-1 manual claims this was always the case for Astrotracer.)

Shooting indoors would bring magnetic problems, floor stability problems (unless the floor is concrete), and weird atmospheric ripples if hot air is escaping the house through the open window.

Ah, yes, thank you, good points.
I have forgotten the latest firmware, and hot air..... plenty of that in this house

Definitely best outside I think. And yes the image above is probably soft because of my finger on the button.

Anyone got any idea how long an exposure I could get away with, pointing a 300mm at Orion in winter from South England?

[jbinpg]

In my experience, you will be lucky to get 30 seconds with a 300mm using Astrotracer, and that is pushing it. You can always push your ISO higher with the latest sensors, especially if you will be stacking frames.

[DrawsACircle]

darkmunk, 24sec with a 300mm lens is pretty ok for a FF camera, For me, it’s max 10sec with my K-70 with GPS and the 300* lens (also the Orion Nebula).
Check: https://www.pentaxforums.com/forums/groups/135-astrophotography/6833-orion-n...-da-300mm.html

[darkmunk]

darkmunk, 24sec with a 300mm lens is pretty ok for a FF camera, For me, it’s max 10sec with my K-70 with GPS and the 300* lens (also the Orion Nebula).
Check: Orion Nebula, K-70 + DA*300mm - Astrophotography - PentaxForums.com

Thanks. That's a cracking shot!
I had another quick go last night, this time in the garden, but with no luck. It seems my Astrotracer is only safe up to about 7 sec. Ran out of time before trying everything

[SteveinSLC]

Agree with the other comments on longer lenses and the astrotracer. I can't really get more than about 15 secs with the DA*300 and K-1 before I get trailing.

Another thing to bear in mind is that since it's the sensor moving(and not the lens and body on a tracking mount), it's difficult to use astrotracer and a long lens to take a long series of >10 sec exposures for stacking. With a sequence of 30 20 second exposures, the target object might actually move out of the lens frame.