[Outis]

I'd like to get into astrophotography-- I was a huge astronomy nut in high school, and would love to get back into that again. I'm going to be traveling to a dark sky site over New Year's, and I'm wondering if I'd be happy with my current kit, or whether I should get something else.

So, I currently have a K-3, a very nice, portable carbon-fiber tripod, and a selection of lenses-- 18-55, 55-300, 15mm f/4 Limited, 21mm f/3.2 Limited, 31mm f/1.8 Limited, 77mm f/1.8 Limited.

There are a number of things I could get to fill holes in my kit:
O-GPS1, for the Astrotracer capabilities, to be able to take longer exposures with my existing lenses;
Photoshop, for image stacking;
A fast wide-angle lens, probably the Samyang 14mm f/2.8, for better shots of the stars above the landscape;
A fast 50mm prime, because the Pentax M or A 50mm f/1.4s are pretty cheap.

What do you all think? Should I just start with what I have, or try to get one of the things on my list, or something else? How much of a difference would it make for me to have the 14mm f/2.8 versus my current 15mm f/4?

Thanks!

[xanis]

I believe your kit is more than enough. Only thing i see you need is not photoshop for stacking. Preferably startrails.exe which stacks a lot faster and better.

[interested_observer]

Well there are a number of items that you could get - for free...

• The Photographer's Ephemeris - The Photographer's Ephemeris - Web App - this will tell you when the sun sets, directions, etc.
• Stellarum is a free down load - this will tell you where everything is on the dates of interest.
• Light Pollution map

For the rest...

• O-GPS1, for the Astrotracer capabilities, - its great, however if you are planning on having landscape elements in the frame, they will be blurred.
• Photoshop, for image stacking; - A version of Elements 11 or better, has a stacking capability, I have been told

For the lenses - the 31mm f/1.8 Limited, 77mm f/1.8 Limited. would be best with their fast aperture and IQ, followed by the 21mm f/3.2 and the 15mm f/4 Limited. Beyond these, f2.8 is the fastest you can really get - other than the Sigma 18-30/f1.8 (~$700), but I really don't think anything else would be necessary - other than lots of hot chocolate....

[transam879]

Beyond these, f2.8 is the fastest you can really get - other than the Sigma 18-30/f1.8 (~$700).

I just picked up a Rokinon 16mm f/2 to play around with astrophotography. It's fast, sharp (even at f/2) and wide, which should be good astrophotography.

[jbondo]

You didn't say if you had any kind of motorized mount. If you do not, the O-GPS-1 (or a mount) will be your single most important accessory. If you already have some kind of star tracking mount, then you have plenty to start with.

We have an astrophotography social group here on PF. If you're interested in joining, or just checking it out, go here --> Astrophotography - PentaxForums.com

[Digitalis]

Beyond these, f2.8 is the fastest you can really get - other than the Sigma 18-30/f1.8 (~$700)

I have had some good luck with the O-GPS1 and the Sigma 18-35mm f/1.8. Manually focusing with such a fast lens can be tricky, as the infinity stop isn't anywhere near accurate for astro work.


Here are my sample images. bear in mind I live in a coastal area in my city, light pollution will have an impact on the results.


Pentax K5IIs - sigma 18-35mm f/1.8 @ 18mm f/1.8 ISO800 20s Astrotracer on.

And a 100% un-sharpened center crop:

un-sharpened center 100% crop from the Pentax K5IIs with the Sigma 18-35mm f/1.8 @18mm f/1.8 ISO 800 20s Astrotracer mode on.

However light fall off at 35mm f/1.8 setting of this lens is problematic:

Pentax K5IIs - Sigma 18-35mm f/1.8 @ f/1.8 35mm ISO 800 30" astrotrace with the Pentax O-GPS1

[ZoeB]

Get a remote! Just the cheap, $3 IR kind. The last thing you want to do is accidentally knock over your camera when closing the shutter at the end of a 15 min exposure.

[Outis]

Thanks, everyone!

---------- Post added 12-14-14 at 09:19 AM ----------

• Stellarum is a free down load - this will tell you where everything is on the dates of interest.

Ah, I have a star map, which I can use for the same function.

---------- Post added 12-14-14 at 09:20 AM ----------

• Photoshop, for image stacking; - A version of Elements 11 or better, has a stacking capability, I have been told

Oh, forgot to ask, does Lightroom have this capability, too?

---------- Post added 12-14-14 at 09:21 AM ----------

I believe your kit is more than enough. Only thing i see you need is not photoshop for stacking. Preferably startrails.exe which stacks a lot faster and better.

Is this just image stacking for star trails, or image stacking if you just want to stack several non-star-trail-y exposures of the same thing?

---------- Post added 12-14-14 at 09:22 AM ----------

I just picked up a Rokinon 16mm f/2 to play around with astrophotography. It's fast, sharp (even at f/2) and wide, which should be good astrophotography.

Cool! I'll look into that, too.

---------- Post added 12-14-14 at 09:23 AM ----------

You didn't say if you had any kind of motorized mount. If you do not, the O-GPS-1 (or a mount) will be your single most important accessory. If you already have some kind of star tracking mount, then you have plenty to start with.

We have an astrophotography social group here on PF. If you're interested in joining, or just checking it out, go here --> Astrophotography - PentaxForums.com

I don't have any kind of motorized mount, unfortunately.

Also, thanks!

---------- Post added 12-14-14 at 09:24 AM ----------

Get a remote! Just the cheap, $3 IR kind. The last thing you want to do is accidentally knock over your camera when closing the shutter at the end of a 15 min exposure.

Thanks! Do you have any recommendations?

[xanis]

I only use it for startrail stacking. Not sure if its able to stack for macro.

[ZoeB]

Wireless IR Remote Control for Pentax Camera (1*CR2025) - Free Shipping - DealExtreme

this is the one that i use. Dealextreme does take a while to deliver, but shipping is free, and the remote works great

[jbondo]

Beware that with the O-GPS1, extreme wide angle lenses will still exhibit trailing around the images, since the sensor can only move in a flat plane, rather than sidereally.

Yes, good point. With planar (sensor) shift tracking there are two side effects that are pronounced with extreme wide angle lenses with long exposures. Planar tracking cannot fully track both the celestial equator and poles simultaneously. This is inherent to the system. A second weakness becomes apparent with lenses that have a lot of distortion. It is geometrically impossible for the sensor shift to accommodate for lens distortion across the entire field in a single exposure. Blurs/trails result as the sensor moves through zones of greater and lesser distortion.

For these reasons, you'll get the very best Astrotracer results with flat field lenses that don't have extreme wide FOV.

Here are tracking devices in order of convenience and results:
1- O-GPS1 Astrotracer: The ultimate in convenience. Super small and easy, but with the weaknesses mentioned above.
2- Mini-barndoor trackers and Micro-mounts such as the Vixen Polarie: Still small, pretty convenient. Require you to align them accurately. Most have limited payload.
3- Alt-Az computerized mounts. Larger, pretty convenient and moderate time to set up. Bigger payload. Good precision. You'll have field rotation with these unless you have a model capable of working in a wedge configuration.
4- Computerized German equatorial mounts. Not convenient. Highest accuracy and payload. Most set up time for best accuracy.

I own and use all of these. It's all about budget and effort. Will I be taking a big mount on my upcoming road trip to Las Vegas? No way! I'm totally throwing the O-GPS1 in the bag. Will I be taking the O-GPS1 for my next serious astro-imaging session? Nope!

Hope this helps.

[gifthorse]

With only a couple of weeks until your trip to the dark sky site, you have already have everything you need to get started and may not have enough time to get the extras. Additions I would add the your kit would definitely include the OGPS-1. I also like the Rokinon 8mm for an ultra wide angle. It's slow but it's relatively inexpensive and has a terrific FOV. I've seen some pretty nice deep sky images done with a 200mm or a 300mm so eventually I might add a longer prime if you're leaning that direction. Certainly a remote. It will really help reduce camera shake. If you can't get a remote release before your trip, use the self timer or the intervalometer. If you're going to do star trails, I'd add a Vello Shutterboss. They're more expensive than a simple remote ($50 for a cabled style, $100 for a wireless) but it's much better for consistent long exposures. If you want to do say, 2 hours of 5 minute exposures, you sit there and stare at your watch for two hours, tripping the shutter every 5 minutes (hopefully). With the Shutterboss you set the exposure length, interval, and number of exposures, trip the shutter and go have a cup of coffee. Make sure you have warm clothing! It's always colder than you think it will be. Post some of your images when you get back. I'd love to see them.

---------- Post added 12-14-14 at 08:23 AM ----------

Oh! Oh! I know! Batteries! Lots of extra batteries. And a torch with a red lens. The ones you wear on your head are good (because they free up your hands so that you can change those batteries).

[transam879]

Get a remote! Just the cheap, $3 IR kind. The last thing you want to do is accidentally knock over your camera when closing the shutter at the end of a 15 min exposure.

A lot of phones now have an IR transmitter built in. You can download one of several apps to remote shutter your camera with your phone. Bonus, phone is usually with us all the time and rarely gets lost in the bottom of the camera bag.

[Outis]

I actually don't have a smart phone-- I mean, that's money I could use for camera lenses!

[transam879]

I actually don't have a smart phone-- I mean, that's money I could use for camera lenses!

Good point. Work pays for mine, that's my excuse.