[MacLoz]

Probably, the HD Pentax-DA 16-85mm f/3.5-5.6 ED DC WR is not the most convenient lens for astrophotography, but I do not pretend to compete with astrophotography prefessionals, just to take nice pictures of the Milky way and the most brilliant constellations using that lens and the K-70. Sometimes, I use Sigma 10-20mm f/4-5.6 EX DC HSM but, occasionally, I prefer the longer focal distances available with the 16-85.

The main problem I found is the absence of any dial or marks in the 16-85 focusing ring, when manual focus is a must and the only brilliant objects to focus are just the tiny stars.

I would thank your comments to tackle this subject in a convenient way, in remote locations with no objects available to focus manually.

[Greg1956]

I've just been using the 18-55mm kit lens on my K 70, 15s at ISO 6400 and f4.

I autofocused on a light some 200m+ away and then switched to manual focus, and left it there for all my photos.
Alternatively light paint a distant object with a torch, autofocus on that, then switch to manual focus.

You can see 2 of them here
Milky Way - Pentax User Photo Gallery
Milky Way - Pentax User Photo Gallery

processed in Paintshop Pro X9

hope this helps
Greg

[AstroDave]

The main problem I found is the absence of any dial or marks in the 16-85 focusing ring, when manual focus is a must and the only brilliant objects to focus are just the tiny stars.

Do some experimenting during the day to check whether "infinity" focus (distance end of travel of the focus ring) is really infinity. For many modern lenses it is not - you can focus beyond infinity (thanks to Buzz Lightyear?).

Not sure about the K-70, but on my K-3 and K-1, live view in magnified mode on a bright star lets me focus adequately. Or, if the moon or planets are up, use them (Venus, Jupiter, Saturn, and Mars are conveniently arrayed across the night sky at the moment!).

[dsingley100]

Tried astrophotography with the 16-85 mounted on a K-70. I used the GPS module and so was able to get longer exposure times in the . Focus is hard in the dark. The two approaches seem to be focus in the light and tape or mark the lens. Second approach is to use live view and focus on a star - or as I found, any bright object in the sky. I focused and then being careful not to move the focus ring composed the shot. Also, bear in mind that with the 16-85 on a cop sensor camera, you will need to take into account the crop factor when determining the maximum length of time the shutter can remain open without getting star trails. With a 1.5 crop factor, the 16mm end of the 16-85 is 24mm, which yields a maximum exposure time of 20 seconds. So exposure will look something like 20 seconds at f3.5, ISO of 3200. With the GPS module, I was able to bring the ISO down to 800, which yielded exposure times in the minute and a half range. That would be a starting point. You will likely have to adjust the ISO to get a usable image. Bear in mind that shooting in raw will allow some exposure compensation in post. Couple of other stray thoughts - view finder was not useful - might have been just me, but could not compose through the view finder. Also, live view was not real helpful for composition either. Again, might have just been me. One last thought - I left the long exposure noise reduction “on” for the images I took. The immediate consequence of doing so is that the time to take each exposure doubled - the actual exposure and then the “dark frame” noise reduction capture. If you do a Google search on photographing the Milky Way a lot of helpful sites will surface. Also, there are a couple of useful pages on the Pentax Forum - Astrophotography I think. Hope that is of some help.

[MaineNative]

A couple of ideas. I often use steeetlights to check focus from a long distance away--the further away the better. If you are out in the wilderness with no lights, you could use a car light or a flashlight laying on the ground.

It is often hard to zoom in enough to see a star, but the key is you are after the smallest dot of light—that means you are in focus. If you go in either direction the dot of light gets bigger as it goes out of focus. That also means you could take a long exposure of a bright star (1 minute or more). Make adjustments to the focus until you get the thinnest star trail. The star trails can be easier to see than a single star.

I live near the ocean and when I was testing the focus on my Samyang 14 mm, I used the bright red channel markers on a nearby bridge for checking focus. I went down river about 1/2 mile and took pictures of the channel markers. In that case the Samyang has distance markings, but I knew they were wrong and wanted to find the correct infinity setting.

Make sure you camera is in manual focus so the camera doesn’t adjust the focus once you’ve set it. Definitely easier to do Astro if you have distance markings.

[Greg1956]

Probably, the HD Pentax-DA 16-85mm f/3.5-5.6 ED DC WR is not the most convenient lens for astrophotography, but I do not pretend to compete with astrophotography prefessionals, just to take nice pictures of the Milky way and the most brilliant constellations using that lens and the K-70. Sometimes, I use Sigma 10-20mm f/4-5.6 EX DC HSM but, occasionally, I prefer the longer focal distances available with the 16-85.

The main problem I found is the absence of any dial or marks in the 16-85 focusing ring, when manual focus is a must and the only brilliant objects to focus are just the tiny stars.

I would thank your comments to tackle this subject in a convenient way, in remote locations with no objects available to focus manually.

MacLoz,

have you anything to show from your trips.?
I'd be interested in seeing how the Sigma 10-20 goes especially at 10mm???

I am considering a Pentax/Samsung 12-24mm, Sigma 10-24mm or Tamron 12-2x as my next lens buy for astrophotography and landscapes.

thanks
Greg