Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-26-2016, 09:18 PM   #1
Pentaxian
schnitzer79's Avatar

Join Date: Jul 2013
Photos: Albums
Posts: 1,192
Which lens for Astrophotography?

Will be going with some friends soon to shoot some stars. Being totally new to Astrophotography, even though I read up on the basics, which of my lenses in my sig do you think is best suited for the occasion? I was between the DA 15mm and the Sigma 35mm f1.4

05-26-2016, 09:32 PM   #2
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 17,016
My only tiny fraction of knowledge in this area is that the DA 15 seems too wide to fully freeze the stars using the sensor shift features. This is not based on personal experience - just reading here. Also the 15 has a lot of coma from what I recall.

Here's an example thread that may help:
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/312579-da-1...ce-wanted.html

Search DA 15 astrophotography for more threads.
05-26-2016, 11:37 PM   #3
Pentaxian
schnitzer79's Avatar

Join Date: Jul 2013
Photos: Albums
Posts: 1,192
Original Poster
Thanks for the reply UncleVanya. But since im not interested in buying another lens for astrophotography since it wont be something I will be doing often, Im basically interested which of the 2 i mentioned will give better results. The DA15 has the advantage of being wider, but the Sigma is definitely sharper and faster.
05-27-2016, 12:01 AM   #4
Site Supporter
Site Supporter




Join Date: Sep 2014
Photos: Albums
Posts: 1,017
Your answer, definitively is the samyang 8mm. You'll need to de-fish it later though. I personally use the samyang 10mm f/2.8 and get rather nice results. 35mm is too narrow FOV wise to give a nice astro landscape image. It's fine for starfields and particular constellations though. You can even get decent results from an 18-55 kit lens if set to 18mm f/3.5. If you're using astrotracer, I suggest ISO 400 f/3.5 for about 115 sec. using the samyang 8mm. If you're using standard manual shutter, keep it around 13 sec, f/3.2, ISO 1250 or 1600, with medium or high NR for the High ISO NR setting.

05-27-2016, 12:31 AM - 1 Like   #5
Senior Member




Join Date: Dec 2015
Location: Brisbane, Australia
Posts: 134
QuoteOriginally posted by schnitzer79 Quote
Will be going with some friends soon to shoot some stars. Being totally new to Astrophotography, even though I read up on the basics, which of my lenses in my sig do you think is best suited for the occasion? I was between the DA 15mm and the Sigma 35mm f1.4
DA15 is usable, but it depends on what you are trying to capture. If you want a star field with some terrestrial items of interest (ie. landscape) it will do the job, you just have to step it down to at least f5.6, if not f8. Problem is you need to increase your ISO or exposure time to compensate. Without astrotracer you will get decent results with 10 to 20 second exposures. Astrotracer will make life easy for you if you have it.

The Sigma is faster, and you may be surprised at how much sky 35mm will capture. Try it with a 10 second capture wide open. If you get streaky stars, shorten the exposure. If the edges look bad, stop it down. And keep experimenting. Remember you can raise the ISO to show more stars, but you need to play around to find a balance between sharpness, visible stars and noise that you are happy with.
05-27-2016, 02:28 AM   #6
Junior Member
scopedude's Avatar

Join Date: Apr 2013
Posts: 43
DA 35/2.4 (and Sigma 35A) and DA50/1.8 should be good wide open or stopped down a bit. DA15 is ok but only f/4 unless you do tracking with EQ mount, Polarie, or Astro Tracer.

ANY focal length is usable, just for different targets. With DA 35/50 you can shoot Milky Way's core (around Sagittarius), widefield of Orion constellation with the M42 visible. In the southern hemisphere the DA50 will allow you to image the Large Magellanic Cloud galaxy. You might want to experiment with DA 55-300 too. If you want to capture the milky way wide, try the 18-135 since that's what you have. Maybe there will be some coma and CA in the corners but if the shoot is well-tracked I wouldn't mind some aberration in the corners. Tracking is the key for well exposed astro photos, then do stacking. That way you could keep the ISO rather low (800 or 1600).
05-27-2016, 03:35 AM   #7
Loyal Site Supporter
Loyal Site Supporter




Join Date: Jun 2009
Location: Tumbleweed, Arizona
Photos: Gallery | Albums
Posts: 5,512
Good Morning,

I do a fair amount of astro (both with and without GPS star tracking), and a lot of low level ambient light stuff. So from the lenses you have here is a run down of what I would use.
  • General overview - For each lens that I am considering using, the prior afternoon while still light out, I would take it out and pre focus it on something very distant (a mile or two away). Using Gaffer's tape (or really any wide tape), I would then tape down the focus ring so that it would not be moving. Other wise you will be out in the dark trying to manually focus (even with zoomed in live view) and it will take about an half an hour for each lens. Will not be a real pleasant initial experience. Also, clean the front lens element.
  • Pentax K-3 II - I would shoot at ISO 1600 minimum, and possibly slide up to possibly ISO 8000 or so. Out in the dark for framing purposes (and with wide angle lenses, I am assuming you are wanting elements of landscape in the shots), I would initially crank the ISO up to 51200 (not a typo), and take a 5 second or so shot. This will give you a very good indication of your framing and composition on the rear monitor. Shoot, look (chimp), adjust framing. Wash and repeat until you are happy. Then turn down the ISO to 1600 to 8000. Shutter speed depends on a couple of things. With NO GPS - 500/focal length if you are just interested in a shot for the web (1000 pixels on edge). You will get some star trailing with this (small web images will mask this). If you desire the stars to be nice points of light then use 200/focal length. The problem is that this will really limit the exposure time (due to the earth's rotation) - and since your lenses apertures are not terribly fast, you will get some dim images. The way around that is pushing up the ISO (which will result in more noise in the images). So with you lenses, your main adjustment will be pushing up the ISO to a degree. Just remember to shoot in raw and then push the images in post processing. Also, shoot with your aperture wide open. You need to be able to gather all the light you possibly can. You don't have to worry about depth of field. With GPS - I would use about 60 second exposures. This will limit trailing around the extreme edges of the frame. If this is not a concern, then go with the maximum exposure duration the camera/gps will allow you to use. You can use ISO 1600 here all the time in order to limit the sensor noise. Shoot with the lens wide open to get all the light possible.
.
So here is a quick run down on your lenses.....
  • Samyang 8mm - at f3.5 this would be a good lens to use.
  • Pentax DA 15mm Ltd - at f4 it is a bit slow, but overall good to use. You will need to push up the ISO to compensate for the f4.
  • Pentax DA 35mm f2.4 - defer to the Sigma
  • Sigma 35mm F1.4 Art - This will be your best lens for wide field astro. Yes, it is not really a wide anle, but it is FAST. You can stitch and use Microsoft ICE to stitch the resulting images together.
  • Carl Zeiss Flektogon 35mm f2.4 - defer to the Sigma.
  • Pentax A 50mm f1.4 - This too will be useful because it is really FAST. You can just aim this at the stars with out any landscape elements and take multiple frames (like 20 to 50 images) and then use star stacking software to stack them together.
  • Pentax DA 50mm f1.8 - defer to the f1.4
  • Samyang 85mm f1.4 - bring this one along too, for deep sky (just star shots). Take lots of frames and then stack them together.
  • Sigma 24-70mm f2.8 - Actually at f2.8 at 24mm, this is extremely useful. Wider than the 35, but faster than either of the 8mm or 35mm. This will probably be your main wide field lens due to the combination of 24mm and f2.8.
Overall, fast lenses are better. I have seen good results with f4. If you are concerned with wanting landscape elements, shoot 1 image with low ISO and very long exposure for the landscape element and then shoot the star images and then composite them together. Just shooting star fields adds some freedom, where by you can shoot a lot of frames (using GPS too) and then stack them together for even better results.

05-27-2016, 04:21 AM   #8
Veteran Member
k5astro's Avatar

Join Date: Apr 2012
Photos: Albums
Posts: 383
As an amateur astronomer I can tell you what you don't want to hear... it depends on what you want to look at. But I know those answers are useless so I'll say go for the wider lens since you are starting out and I think you'll get nicer images in general. When you decide there are specific areas of the sky you want to capture, then you can get a longer lens. But always fast primes! Good luck!

Oh by the way! This is not why I answered your post but I made and app for polar alignment of camera mounts. Its called AstroBuddy and is available for iPhone. Check it out and hope you like it.

https://www.facebook.com/gbastrobuddy/?

05-27-2016, 04:23 AM   #9
Loyal Site Supporter
Loyal Site Supporter
WPRESTO's Avatar

Join Date: Aug 2010
Location: Massachusetts
Photos: Gallery | Albums
Posts: 44,987
For starting astrophotography:

1) large aperture, short FL are the easiest for starting (fast primes are almost always the best bet, regardless of FL). As focal length increases, the challenges of getting a good image go up exponentially;
2) use manual exposure = "bulb" (talk about a term left over from the earliest days of photography)
3) push the ISO up (6400).
4) because the Earth moves, longer exposures = stars recorded as streaks rather than points.
5) If you know how, use image stacking = multiple short exposures combined in PP; There are programs dedicated to stacking astrophotos, but a general-purpose stacking program such as Zerene will serve a beginner very well.
6) WAIT until long after sundown if you want stars against a black background.
7) in PP, experiment with the contrast settings, the "highlight" and "shadows" sliders. Astrophotos are typically very high contrast, but increasing the depth of the black can reduce the number of stars visible (the faint ones disappear). Fiddle.
05-27-2016, 09:19 AM   #10
Pentaxian
schnitzer79's Avatar

Join Date: Jul 2013
Photos: Albums
Posts: 1,192
Original Poster
Thanks for the brilliant replies. A lot of useful info here.

Heres what I intend to do. Definitely use GPS and astrotracer on the K-3II. It will be the first time using it as well. We will be going to the location after 10 pm which is an abandoned village with ruins and deserted houses so will want to capture some landscape too along with the sky. The reason I was thinking mostly of the Sigma 35mm is because it is very sharp wide open and will benefit from the f1.4. Just uncertain if at f1.4 any of the foreground will be sharp since I intend of focusing at infinity. Im also not sure if I will need to do any light painting on the deserted houses and trees or if that will ruin the image. I know its a matter of trial and error, just trying to minimize the tries as much as possible, since it will be dark and changing lenses constantly in the dark is not a good idea.
Havent done any stitching before, but I only use photoshop cs6 so I know you can stack images there too if needed, but that wasnt the plan that I has in mind.
Anyone who has tried astrophotography on the k-3II, will I need to do a GPS calibration on the spot prior to shooting? Also any one know how fast the GPS drains the battery?
05-27-2016, 10:38 AM   #11
Pentaxian




Join Date: Jan 2011
Location: New York
Posts: 4,627
QuoteOriginally posted by schnitzer79 Quote
...will want to capture some landscape too along with the sky...
That's difficult but doable with practice. The astrotracer will blur the landscape. You either need a short enough exposure to keep the stars sharp without using the astrotracer, separate foreground (no astrotracer) and background (with the astrotracer) images to layer in Photoshop, or take a startrail image.

I suggest the startrail. It takes the most time in the field, but the processing is relatively easy. Look at Software - StarStaX or Startrails application for easy to use software. Some notes about my preferences for startrails:
  1. Try focusing somewhere a little short of infinity, and stop down a little. See if you can't get the foreground and background reasonably sharp at the same time. (as you get more experience, then you might want to do separate Photoshop layers, but set low expectation for your first time doing this)
  2. Manual mode. 30 second shutter (star movement is okay, you'll be making longer trails during processing anyway), ISO 1600 as a start.
  3. I prefer to use a wired shutter release instead of the intervalometer menu. Set the shutter to high-speed continuous and you'll get no gaps between images. The intervalometer often causes tiny star gaps between each image.
  4. Use DNG+JPG capture mode. The JPG is what you'll process with the software; JPG is quicker to process than DNG and after stacking you won't have much noise. I like to have the DNG, though, in case I find a need for more processing.
  5. Turn off shake reduction.
  6. Take around one hour of photos.
  7. Aircraft light trails will probably mar your final processed image. There are techniques for fixing them. In short, open the offending JPG files in Photoshop, use smart erase or just paint black over the plane trails, then repeat the stacking process.
While you're out, also take a few Milky Way images if the sky is dark enough. Use the astrotracer and just go for the Milky Way without foreground. This will give you photos to practice processing in Lightroom and Photoshop. Experiment with your 15mm and 35mm lenses. Try a range of apertures: wide open, 1 stop down, 2 stops down. ISO 800, 1600, 3200. That's 18 test photos to play with later. You'll eventually find a favorite lens and favorite settings for astrophotography.
05-27-2016, 10:38 AM   #12
Loyal Site Supporter
Loyal Site Supporter




Join Date: Apr 2015
Photos: Gallery | Albums
Posts: 746
This site has some very helpful info How to Pick a Lens for Milky Way Photography – Lonely Speck

That's a guide for Milky Way stuff, but there's more on other parts of the site. Somewhere in there is a link to a spreadsheet on Google Docs that breaks down lenses by speed and FOV, since they are interrelated for purposes of getting a nice shot without trailing.
05-27-2016, 02:41 PM   #13
Senior Member




Join Date: Dec 2015
Location: Brisbane, Australia
Posts: 134
QuoteOriginally posted by schnitzer79 Quote
Thanks for the brilliant replies. A lot of useful info here.

Heres what I intend to do. Definitely use GPS and astrotracer on the K-3II. It will be the first time using it as well. We will be going to the location after 10 pm which is an abandoned village with ruins and deserted houses so will want to capture some landscape too along with the sky. The reason I was thinking mostly of the Sigma 35mm is because it is very sharp wide open and will benefit from the f1.4. Just uncertain if at f1.4 any of the foreground will be sharp since I intend of focusing at infinity. Im also not sure if I will need to do any light painting on the deserted houses and trees or if that will ruin the image. I know its a matter of trial and error, just trying to minimize the tries as much as possible, since it will be dark and changing lenses constantly in the dark is not a good idea.
Havent done any stitching before, but I only use photoshop cs6 so I know you can stack images there too if needed, but that wasnt the plan that I has in mind.
Anyone who has tried astrophotography on the k-3II, will I need to do a GPS calibration on the spot prior to shooting? Also any one know how fast the GPS drains the battery?
With the astrotracer you will need to stack foreground and background. To be honest, you should do that without astrotracer as well as the exposure requirements are very different for the 2 elements. To take advantage of astrotracer will mean the foreground is blurred by the moving sensor.

You will need to calibrate onsite, make sure you are not near any iron/steel when you do so as you are actually calibrating the compass, not the GPS! Follow the instructions and don't be afraid to recalibrate later if you keep getting small star trails on sub minute exposures.

My starting point for any sky shot with the astrotracer is 60 seconds, 1600 ISO. If the sky is washed out, I have light pollution and need to decrease the ISO (which means less stars, but that's life). If I have trails I either need to recalibrate or shorten the exposure length. Remember to experiment, especially as this is your first time. You will take lots of shots, you will bin most of them, but you will end your night with something you are happy with and a lot more knowledge then you started with! Play with different lenses and find what works for you, what gets you the sort of image you have visualised. Astrophotography can include quite a bit of personal taste!

For the landscape just take shots with different settings until you are happy. You can easily do very long exposures with low ISO and a sharp aperture in bulb mode (as long as there is no wind). Using photoshop means you can focus on getting the foreground exactly as you want it.
05-30-2016, 10:26 AM   #14
Veteran Member
ScooterMaxi Jim's Avatar

Join Date: Jul 2009
Location: Minnesota
Posts: 1,519
As to the original poster, I'm pretty sure the Sigma would be the better performer. The Pentax is slow, so shooting it wide open yields a somewhat compromised performance - and it isn't known for controlling coma or sharpness into the corners.

I agree with all posters who point out that there is no substitute for a fast prime in astrophotography. Those who can astro-track obviously are in better position to use longer exposures and stop down. Not sure it is that important for UWA work, but it does give you some flexibility. Rather than choose a single lens, I would experiment to see what perspective looks best for you. I decided to do my first traditional astrophotography last night (other than various solar sunspot and solar and lunar eclipse shooting). I used low-powered, diffused flash to fill in terrestrial - aiming for realism in landscape and starscape (i.e. - not added saturation or over-brightness).

I had slightly expected the Samyang 14mm to outperform the 8mm with both set at f/4, but the edge goes slightly to the 8mm. Both worked well, capturing the scene in the way I hoped with a minimum of aberrations.

Taos Spring 2016 - James Robins - Powered by Phanfare

I forgot to mention that the EXIF isn't accurate. I chose 12mm, but the actual lens is the 14mm, of course (second shot). The timing isn't properly registered. I chose 20 seconds for the 8mm, and 15 seconds for the 14mm for purposes of freezing star trails. Raising shadow was the main change (other than lowering harshness of flash in landscape). The exposure seemed about right. I process in Capture One (v9.1.1). I use quite a bit of noise reduction and micro-contrast.

Last edited by ScooterMaxi Jim; 05-30-2016 at 10:36 AM.
05-30-2016, 11:03 AM   #15
Pentaxian
Aaron28's Avatar

Join Date: Jan 2015
Location: Huntsville, Al
Posts: 5,138
it's all trial and error! the 35/1.4 would be an excellent choice to begin with (the 15/4 will be fine as well given the extended exposure time the astrotracer can give you, any of yer lenses really)
I would begin with a fully charged strong battery......precise calibration......try 40 seconds 800iso wide open.......adjust out from there.....push the time to maybe 2 minutes or when trailing developes also light pollution will play a huge factor as well.....find a balance between time & iso that suits you and yer conditions and stay wide open for the sky at infinity focusing.....then do whatever it is you do to expose for the foreground....stopdown, different focal point, etc.......then blend a nice composite of the 2 frames which is an editing skill I sorely lack and have a terrible time accomplishing.......good luck, don't give in to frustration and most importantly happy shooting with dark clear skies!
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
k-mount, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Best lens for astrophotography vikranta Pentax SLR Lens Discussion 27 06-17-2016 04:42 PM
P645Z and 28-45mm lens for landscape astrophotography Femtometer Pentax Medium Format 10 03-28-2016 01:32 AM
Which fast 50 for Astrophotography (1.2, 1.4, 1.7) ? LennyBloke Pentax SLR Lens Discussion 18 08-04-2014 04:43 AM
Good Cheap Lens for Astrophotography krp Pentax SLR Lens Discussion 8 10-16-2011 02:27 AM
Affordable lens for astrophotography jamesv93 Troubleshooting and Beginner Help 8 11-04-2009 05:31 PM



All times are GMT -7. The time now is 03:29 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top