[captainbert]

Hi. I am looking to start shooting the night sky and primarily i want foreground like trees and buildings rather than deep space telephoto type shots. I have two wide angle lenses for my K5: Sigma 10-20 4-5.6 and the DA 15 f4 limited. It seems that both lenses are less than ideal as both have to be stopped down for decent performance, however, if I was to use the Astrotracer would i be able to stop either of these down to about f8 and still get decent results? Or would i be better of buying something like the Samyang 14 2.8 which i could probably use closer to wide open and get good results without the astrotracer? I am also wondering how one goes about shooting one shot for the foreground and other shots for the night sky and then combining them. Any advice is most welcome! I don't know if this is posted in the correct section too as am unsure where i should go.

[Stone G.]

Before you buy anything else, have you tried to capture the kind of scenes you want, with the lenses that you already have? I would be surprised if they turned out to be completely hopeless.

Using Astrotracer (I have one myself) with wide lenses stopped down as much as to f/8 will be probelematic: Stars are pointlike sources of light and are recorded quite differently from extended surfaces such as the Moon or your foreground subjects: The amount of light captured and recorded from a star of given brightness depends only on the area of the entrance pupil of your lens - and NOT the f-number. Furthermore, the parallel bundle of light from a star will be diffracted and spread over a diffraction pattern, effectively a small circle whith a diameter that grows (!) proportionally to the f-number. So, if you stop down to f/8 your star images will be very spread out and faint and therfore, you will have to expose for a very long time to capture anything at all.

With a decent lens in the 15mm range you should be able to expose for about 20s without getting too annoying star trails using a fixed tripod only.

[captainbert]

Before you buy anything else, have you tried to capture the kind of scenes you want, with the lenses that you already have? I would be surprised if they turned out to be completely hopeless.

Using Astrotracer (I have one myself) with wide lenses stopped down as much as to f/8 will be probelematic: Stars are pointlike sources of light and are recorded quite differently from extended surfaces such as the Moon or your foreground subjects: The amount of light captured and recorded from a star of given brightness depends only on the area of the entrance pupil of your lens - and NOT the f-number. Furthermore, the parallel bundle of light from a star will be diffracted and spread over a diffraction pattern, effectively a small circle whith a diameter that grows (!) proportionally to the f-number. So, if you stop down to f/8 your star images will be very spread out and faint and therfore, you will have to expose for a very long time to capture anything at all.

With a decent lens in the 15mm range you should be able to expose for about 20s without getting too annoying star trails using a fixed tripod only.

Thanks very much for that! Actually no, I have not as yet experimented with shooting stars so maybe i should explore that before buying anything else. I have virtually no understanding a yet as to how astrophotography works so i had no idea as to the effect of using smaller f-numbers. I shall head to the country on the next dark night and try some shots with what i have before buying anything else. Thanks very much for your guidance!

[pixelsaurus]

Stopping down to f/8 will have a greater effect on nebulosity (ie it will not record very well as they are extended sources) as opposed to stars (point sources). The good news is that background skyglow (natural and man made) will not be significent.

[captainbert]

Stopping down to f/8 will have a greater effect on nebulosity (ie it will not record very well as they are extended sources) as opposed to stars (point sources). The good news is that background skyglow (natural and man made) will not be significent.

Thanks and wow love that image! Can i ask the procedure for producing such a mighty shot?

[pixelsaurus]

Thanks and wow love that image! Can i ask the procedure for producing such a mighty shot?

It is Comet McNaught which was around Dec 06/Jan 07. It was shot on a Pentax *ist DS, 30s and f/3.5, 18mm (Pentax DA 18-55mm), tripod mounted.The image has a lot of noise in it and processing it has been a work in progress for the past 6 years. I finally bit the bullet several weeks ago and had a stab at processing it in IRIS (freeware at Iris software )

It is still a work in progress but half an hour in IRIS produced better results than 6 years in PSE6.

[captainbert]

It is Comet McNaught which was around Dec 06/Jan 07. It was shot on a Pentax *ist DS, 30s and f/3.5, 18mm (Pentax DA 18-55mm), tripod mounted.The image has a lot of noise in it and processing it has been a work in progress for the past 6 years. I finally bit the bullet several weeks ago and had a stab at processing it in IRIS (freeware at Iris software )

It is still a work in progress but half an hour in IRIS produced better results than 6 years in PSE6.

Well that is most certainly worth the effort as it is an absolute gem of a shot! I'd be very happy if i could produce something like that!

[pixelsaurus]

Thankee, I forgot to add it was ISO 3200 Weather was a shocker at the time. For the 6 odd weeks of the apparition, I got to see it 5 times only. On this particular night, I had a half hour of intermittent cloud before the night turned to custard. If you get into astro, all I can say is "Welcome to the Dark Side".

[captainbert]

Thankee, I forgot to add it was ISO 3200 Weather was a shocker at the time. For the 6 odd weeks of the apparition, I got to see it 5 times only. On this particular night, I had a half hour of intermittent cloud before the night turned to custard. If you get into astro, all I can say is "Welcome to the Dark Side".

Ha ha thanks for the welcome!

[pixelsaurus]

Some of us hang out here Astrophotography - PentaxForums.com

[captainbert]

Good to know! Hope fully i'll be a contributing member in the near future!

[Docrwm]

https://www.pentaxforums.com/forums/pentax-news-rumors/198792-pentax-astrotr...-tomorrow.html

http://www.astroarts.jp/news/2011/06/03hoshinavi/pentaxgps.jpg

NHK WORLD TV | Great Gear
Normally, taking great pictures of the night sky requires expensive equipment that tracks the movement of the stars. But recently, a major Japanese camera company has come out with a simple and affordable device that helps do away with all the conventional equipment.
Everyone would agree that photographs of the starlit sky look amazing. However, unfortunately, it may not be easy for anyone to take good photos, except for astronomy enthusiasts who build homemade observatory domes in their backyards.

Astrotracer by PENTAX RICOH IMAGING. It follows the movement of the stars when taken photographs. During the few minutes of exposure time, the camera calculates the movement of the stars, and the image sensor follows the movement.

We check out this exciting new device, made by astronomy fans for astronomy fans, and easy to use, even for beginners.

[Stone G.]

Thanks very much for that! Actually no, I have not as yet experimented with shooting stars so maybe i should explore that before buying anything else. I have virtually no understanding a yet as to how astrophotography works so i had no idea as to the effect of using smaller f-numbers. I shall head to the country on the next dark night and try some shots with what i have before buying anything else. Thanks very much for your guidance!

Since you are new to this field, you migtht want to consult a few simple guides before your first attempts. I suggest you follow the steps described here:

Fixed Tripod Astrophotography

and in particular here:

Quick Start Guide for Beginner Digital Astrophotography

You will note that stopping down the lens isn't recommended here either. With a 15mm lens at f/8, your entrance pupil ("free aperture") will be only 1.9 mm in diameter. Compare that to the pupil of a dark adapted human eye, which will be some 4 - 9 mm depending upon age. I doubt you will capture any stars with camera on a fixed tripod. You can also see some examples of this effect on my homepage:

Camera Settings for Astrophotography

First of all: Do experiment with various settings and exposure times - and HAVE FUN!!!

[captainbert]

https://www.pentaxforums.com/forums/pentax-news-rumors/198792-pentax-astrotr...-tomorrow.html

http://www.astroarts.jp/news/2011/06/03hoshinavi/pentaxgps.jpg

NHK WORLD TV | Great Gear
Normally, taking great pictures of the night sky requires expensive equipment that tracks the movement of the stars. But recently, a major Japanese camera company has come out with a simple and affordable device that helps do away with all the conventional equipment.
Everyone would agree that photographs of the starlit sky look amazing. However, unfortunately, it may not be easy for anyone to take good photos, except for astronomy enthusiasts who build homemade observatory domes in their backyards.

Astrotracer by PENTAX RICOH IMAGING. It follows the movement of the stars when taken photographs. During the few minutes of exposure time, the camera calculates the movement of the stars, and the image sensor follows the movement.

We check out this exciting new device, made by astronomy fans for astronomy fans, and easy to use, even for beginners.

Really impressive! I think i will definitely be going for it once ive tested with what gear i have first.

[captainbert]

Since you are new to this field, you migtht want to consult a few simple guides before your first attempts. I suggest you follow the steps described here:

Fixed Tripod Astrophotography

and in particular here:

Quick Start Guide for Beginner Digital Astrophotography

You will note that stopping down the lens isn't recommended here either. With a 15mm lens at f/8, your entrance pupil ("free aperture") will be only 1.9 mm in diameter. Compare that to the pupil of a dark adapted human eye, which will be some 4 - 9 mm depending upon age. I doubt you will capture any stars with camera on a fixed tripod. You can also see some examples of this effect on my homepage:

Camera Settings for Astrophotography

First of all: Do experiment with various settings and exposure times - and HAVE FUN!!!

Fantastic stuff! I've had a good read through and found other links so i'm going to experiment on the next clear night. Thanks for all the help!