Chasing star trails with an 8x10

[John Kasaian]

I've got permission to spend as much time as I want between 7:00PM and 7:00AM in a special place, directly South of a landmark I want encircled by star trails. I have an idea where the moon will be rising and setting to avoid getting it in the shot courtesy of
https://www.cambridgeincolour.com/tu...calculator.htm
Aside from the 1/2 mile hike in and out sugar anting the 8x10, tripod, thermos bottle and lawn chair, I have my choice of HP-5+ or FP-4+ emulsions.
Which film do you recommend?
The lens will be either a 14" Commercial Ektar or 10" Wide Field Ektar
I also have to select an evening that will be cloudless, like under a high pressure system, which should be easy enough to predict this time of the year.
I also have to determine which phase of the moon will offer the best light for my purpose---I'm thinking a full moon might be too bright, washing out the night sky.

It has been a long time since I did any night photography and I can't even recall shooting any star trails using large format.

If the North Star is directly behind my target, the star trails should make complete circles, right?

Is there anything else that needs taking into consideration?

[Gary Beasley]

Personally I would use Acros for its reciprocity characteristics. Faster film will give you fatter trails on the bright stars so you should previsualise with that in mind.

[John Kasaian]

Personally I would use Acros for its reciprocity characteristics. Faster film will give you fatter trails on the bright stars so you should previsualise with that in mind.

I'm tending towards shooting during a New Moon with HP-5+, for 1 hour at f/8. I wasn't aware that Acros is available in 8x10 although I think Tmax 400 may still be?

[LabRat]

The sky is a 24 hour "clock", so for full circles you need to expose for that, but there is that pesky thing called daytime that will blow out the exposure...

But don't fear, after a long enough exposure, other stars will help fill the incomplete circle...

To really get a complete-like effect, you need to expose from after sunset, to before sunrise... Light pollution will start fogging dark areas after not too long time... That can be kept lower by shooting through a dark red filter... Stars themselves are quite bright and will record as they move well...

This is a better project to do if you stay up all night while camping, while one camera is open the entire time... Shorter exposures only record shorter segments of the arcs...

Bring mosquito repellent!!!

Steve K

[John Kasaian]

The sky is a 24 hour "clock", so for full circles you need to expose for that, but there is that pesky thing called daytime that will blow out the exposure...

But don't fear, after a long enough exposure, other stars will help fill the incomplete circle...

To really get a complete-like effect, you need to expose from after sunset, to before sunrise... Light pollution will start fogging dark areas after not too long time... That can be kept lower by shooting through a dark red filter... Stars themselves are quite bright and will record as they move well...

This is a better project to do if you stay up all night while camping, while one camera is open the entire time... Shorter exposures only record shorter segments of the arcs...

Bring mosquito repellent!!!

Steve K

Definitely mosquito repellent. Thanks!

[Vaughn]

Aperture will affect the width and sharpness of the trails. Aim of those middle ones, f16 or f22 or so, for narrow sharp trails.

Unless you are bringing it or there is lighting on the landmark, it will be siloletted (sp?), so choice of film is not that important...faster film for more contrast between the sky and stars at the same aperture (more exposure of the stars while sky remains black). Reciprocity failure will not affect the exposure of the stars themselves and will help keeping the sky dark. So the exposure you want on the landmark will determine a lot of your exposure needs.

[John Kasaian]

Aperture will affect the width and sharpness of the trails. Aim of those middle ones, f16 or f22 or so, for narrow sharp trails.

Unless you are bringing it or there is lighting on the landmark, it will be siloletted (sp?), so choice of film is not that important...faster film for more contrast between the sky and stars at the same aperture (more exposure of the stars while sky remains black). Reciprocity failure will not affect the exposure of the stars themselves and will help keeping the sky dark. So the exposure you want on the landmark will determine a lot of your exposure needs.

Lighting will be an issue. There's no power to the site and it's in a pretty dense forest, so I'll be stuck with a silhouette I'm guessing. Thanks!

[Vaughn]

Lighting will be an issue. There's no power to the site and it's in a pretty dense forest, so I'll be stuck with a silhouette I'm guessing. Thanks!

Pop a handheld flash a few times. The exposure does not have to be too long to get the feel of a circle. There should be plenty of examples on-line with the length of the exposure noted to give you an idea of length of star trails over time. And unless you need (and can get) detail in the landform, reciprosity failure can be your friend and a conventional film will help to keep the sky black as the stars will not be dimmed by reciprosity failure.

I have 2 boxes of 8x10 Acros you can't have. Bought them in Kyoto a couple years back.

[John Kasaian]

Pop a handheld flash a few times. The exposure does not have to be too long to get the feel of a circle. There should be plenty of examples on-line with the length of the exposure noted to give you an idea of length of star trails over time. And unless you need (and can get) detail in the landform, reciprosity failure can be your friend and a conventional film will help to keep the sky black as the stars will not be dimmed by reciprosity failure.

I have 2 boxes of 8x10 Acros you can't have. Bought them in Kyoto a couple years back.

Ilford is what I have, so I'll roll with that

[LabRat]

Lighting will be an issue. There's no power to the site and it's in a pretty dense forest, so I'll be stuck with a silhouette I'm guessing. Thanks!

If you need some lighting, consider some large flashbulbs... Compact, require some low voltage batteries to power, and even if not enough power to cover scene, at least will start reaction on film to allow ambient light to help build image during long exposure...

Steve K