4x5 Astrophotography

[konakoa]

I wanted to find out what Kodak High Speed Infrared would do, and this was my result.

Sadly my box of KHSI film is quite old and that had a significant and unfortunate effect. It expired in 1989 and has age related fog. It’s still just usable for general work and landscapes (impressively so) however astrophotography was asking a lot of it in its current state. In an attempt to boost contrast I also gave extra development and that didn’t do the film any favors either. Exposure time was one hour with the lens at f/5.6, a dark red B+W 091 filter was also used; my primary interest was to see if this combination would cut through my city light pollution.

There is a faint image of Sagittarius along with some of the milky way just barely visible. I rather inelegantly did some further contrast adjustments to the digital photo of the negative bring out a bit more detail. If the film was still fresh and new, perhaps the result would have been much better. We’d all like for things to work perfectly, yet less than ideal results are no less useful. I’ve been curious for a very long time what an infrared film would record!

[James Cormier]

Trying new films, either hypered or out of the box is a time consuming labor. Many were looking for the holy grail stock. Kodak Tech Pan, when hypered was that stock. Prior to that, Kodak's Spectroscopic Emulsions were the best shows in town.

Fujifilm Acros was the last great film stock, actually surpassing Tech Pan in raw recording power, but without the sought after red sensitivity desired to photograph Hydrogen-alpha emissions in nebulae.

There were many succesful color films in years gone by. Kodak Ektachrome E100S and E200 produced excellent color transparencies. Fujifilm Fujichrome Provia 400F was nearly as good.

Astrophotography was almost always persued in 35mm format. Few mastered 6x7 in the 70s and 80s, but in the 90s 6x7 use exploded with the availability of proper films in 120 format. This step up in quality kept film going into the early 2000s, at least in wide-field work.

Large Format astrophotography was practiced by a few in the 60s and 70s. These were mostly accomplished by amateurs using WWII surplus lenses, commonly the Aero Ektar 7" and 12". They were fast, even when stopped down - and they needed to be. Oftentimes, this also required yellow filters to squelch ultraviolet and blue light, causes of lens aberrations.

Under dark skies, I find exposures as little as 45 minutes at f/5.6 to provide a minimally dense negative to work with. This is with the now discontinued Fujifilm Acros. I use a Toyo 45AR, which is quite rigid, ideal for this purpose. Of course it must be driven equatorially. For this the Losmandy G-11 does the fine work of tracking during exposure.

I use Xtol 1+1 and 13 minutes at 68° F. The negatives look quite nice on the light table. No sky fog at 45 minutes exposures if shot near the zenith. I could probably do 90 minutes before I see density on the negative from natural sky glow at f/5.6.

Near the horizon is a different story. Sky glow is generally more intense, as is atmospheric pollutants mixed with humidity, when exposing within 20 degrees of the horizon. Starlight is dimmed and the ideal exposures may not be realized. Chances are much better in the crisp air of autumn or God forbid, winter!

[James Cormier]

Last October, with good clear and dark skies and night arriving at a reasonable hour, I made this image of the constellation Cygnus on Fuji Acros. This was nearly overhead during the exposure, which lasted 45 minutes. I used the Toyo 45AR and 210mm Sironar N wide open at 5.6.



A crop section to show detail



Both images look a bit soft on this forum.

The setup is as you see here. The two 6x7 cameras with 165mm glass act as ballast as this mount does not even recognize the weight of the Toyo by itself. All three cameras were exposing film at the same time. I figured, why not?



No guidescope or correction was needed. The Losmandy was guiding within about 10 seconds of arc for the long exposures. That is not a challenge for even 400mm lenses.

Lenses were capped for the occasional aircraft passing overhead. Faint satellites, and there's allot of them, do not register on the film. One brighter satellite did corrupt the exposure, but it is hard to see in this small image.

Zero light pollution and no sky glow noted on the negative. Meaning that the exposure could (should?) have been longer.

This was the inaugural exposure for the new observatory built last summer. This is a photo of inside the observatory the night the photos of Cygnus were taken.



Into the dark skies above......

[tgtaylor]

The sun is extremely active these days. This is how it has been looking for the past few days:

Looked pretty much the same when I observed it Monday with a 80mm Pentax spotter. While not LF, I have a planetary camera coming-in but I could, I imagine, mount a LF camera with the 760mm Apo-Nikkor lens and solar filter and get something on film. The sun's contribution to climate change/global warming is under appreciated IMO.

[tgtaylor]

There is a huge sunspot (AR3780) on the sun right now that is visible to the unaided eye. I am able to see it using only the Eclipser HD safety solar glasses I got from B&H a while back. This posting on Cloudy Nights shows it with a superimposed planet earth for size comparison, and several other sun spots currently visible: https://www.cloudynights.com/topic/9...a-and-wl-8824/

[tgtaylor]

VERY STRONG GEOMAGNETIC STORM: Multiple CMEs hit Earth over the weekend, sparking an ongoing geomagnetic storm. Storm levels are currently fluctuating between strong (G3) and severe (G4). This plot from NOAA shows the progress of the storm so far:



Last night, auroras were spotted in more than 30 US states as far south as Texas, Mississippi, Arizona, Colorado and California. The lowest latitude naked-eye sighting so far is +32 N. If the storm continues (a big IF), there could be a repeat display tonight, Aug. 12-13. Source: Spaceweather.com

The auroras were visible all last night in Yosemite.