Astrophotography with the Travelwide 4x5?

[plywood]

Just came in from looking at the moon in a little 3 inch f6 reflector. It's still daylight here but it got me to thinking. Has anyone done wide field astrophotography with their 4x5? The 90 is so light it would put no stress on a barndoor mount and the wide field of the 90 mm lens could suffer slightly inperfect alignment. Of course, f6.8 is very slow, and if you stopped down to f16 to clean up the edges that could make for some very long exposures, too long for a barndoor mount to trac accurately. So....Is was just curious if any here had used their 4X5 for night sky photography.

[Corran]

Yes, I have, but with the intent being startrails, not traditional wide-field. However, I want a good German equatorial mount some day, and I would do more with that.

See here:
http://www.largeformatphotography.info/forum/showthread.php?108317-Startrails!

I haven't done any in a while. Weather has been generally poor and my time short.

I think the focal lengths for traditional wide field would be longer though. 90mm is fairly wide and will have a lot of foreground unless you are pointed pretty far up.

[Drew Bedo]

Any Astro-Photo enthusiasts thinking of putting a TW behind a serious telescope?

I was thinking of using the TW body with a little spotting scope for thet stacked Telephoto look associated with 35mm .

[plywood]

Yes, I have, but with the intent being startrails, not traditional wide-field. However, I want a good German equatorial mount some day, and I would do more with that.

See here:
http://www.largeformatphotography.info/forum/showthread.php?108317-Startrails!

I haven't done any in a while. Weather has been generally poor and my time short.

I think the focal lengths for traditional wide field would be longer though. 90mm is fairly wide and will have a lot of foreground unless you are pointed pretty far up.

A good German equatorial mount would be very expensive. I was thinking more of a simple 'barndoor' type mount. True, tracking is limited from 10 to 20 min. depending on fl and degree of enlargement but they are simple to construct and cheap. Many years ago I saw a design for a special barndoor mount that had the driven board lifting the mounting board that the camera was attached to. This design, if constructed with care, could tract with amazing accuracy for several hours.

I was thinking along the lines of using HP5 and trying only for stars of mag 5 or more in a short 2-5 min exposure. I don't think even the brightest extended objects would show up at all.

[DougD]

Given that the TW is so light, I am tempted to mount it on my Vixen Polarie (baby EQ mount for light cameras).140034

[Corran]

A good German equatorial mount would be very expensive.

Oh I know, I kinda want this:
http://www.amazon.com/Celestron-Computerized-German-Equatorial-Mount/dp/B0024OEW3Q/

Of course, the telescope is extra! But, I recently bought some lens elements that would make a really nice Dobsonian...

[plywood]

Had to look up that Vixen Polarie. At $380 it seems a bit pricey for what you get. With a 1 rpm Hankscraft motor and a few bits of hardware and some plywood I think I could build something that would work as well for maybe 1/10 that price. It would not be as compact but would still run on batteries and be a completely mobile setup.

[LabRat]

Had to look up that Vixen Polarie. At $380 it seems a bit pricey for what you get. With a 1 rpm Hankscraft motor and a few bits of hardware and some plywood I think I could build something that would work as well for maybe 1/10 that price. It would not be as compact but would still run on batteries and be a completely mobile setup.

You will fiddling with it for awhile... The earth turns at 1 RPD (day)...

The "barn door" mount works, but only for a shorter while that might allow a full exposure with a smaller camera with a high f ratio, but with a longer exposure on a large camera, the "barn door" only tilts on one axis, so the stars will smear as it does not follow the circular path...

Piggybacking the camera on a well set-up equatorial mount using the scope as a guide scope works well...

Another problem with sheet film astro images is with the camera (aiming up), that when the dark slide is pulled in the damp night air, the moisture can cause the film to flex/bulge until it settles, resulting uneven focus as the focal plane is moving with the film... (35mm or digital don't bounce around like that...)

Steve K

[DougD]

Had to look up that Vixen Polarie. At $380 it seems a bit pricey for what you get. With a 1 rpm Hankscraft motor and a few bits of hardware and some plywood I think I could build something that would work as well for maybe 1/10 that price. It would not be as compact but would still run on batteries and be a completely mobile setup.

Yeah. I get it. As an apartment dweller, I don't have the kind of workshop access that some folks do.

[plywood]

LabRat,
No, the motor is not for direct drive. It turns a 1/4-20 bolt in a pivoted thread at 11.25 inches from the axis. At least that is the measurement I remember. So that a mark on the edge of a 22.5 inch diameter circle is moving at 1/20 inch per minute. Does that make sense now? Anyway, I was thinking of using a 1/4-20 threaded rod bent to that 11.25 inch radius and have it driven by the 1/4-20 bolt rotating at 1 rpm. That would take care of the tangent error of a straight barndoor mount. You would only need about 12 inches of threaded rod bent around about 1/8 of a 22.5 inch circle, a sector if you will. The motor with bolt can swing away to reset the sector. This idea isn't mine, I saw it in some old Sky & Telescope I think.

[plywood]

Yeah. I get it. As an apartment dweller, I don't have the kind of workshop access that some folks do.

Sorry about the apt situation Doug. I live in an apt too but this one has a garage. Actually my tool selection is pitiful at this time. Need to get a table saw and router and router stand. Money money money, all it takes is money.

[konakoa]

Just came in from looking at the moon in a little 3 inch f6 reflector. It's still daylight here but it got me to thinking. Has anyone done wide field astrophotography with their 4x5? The 90 is so light it would put no stress on a barndoor mount and the wide field of the 90 mm lens could suffer slightly inperfect alignment. Of course, f6.8 is very slow, and if you stopped down to f16 to clean up the edges that could make for some very long exposures, too long for a barndoor mount to trac accurately. So....Is was just curious if any here had used their 4X5 for night sky photography.

It can definitely be done. My little EQ setup below. Been doing astrophotography with a 4x5 for years and years. Not using a Travelwide but my metal 4x5 field camera. Homemade vacuum film holder for the issues LabRat mentioned. You don't need f/16. f/8 is just right for my lenses.

The Polarie is a very nice, wonderfully compact little mount. I've got one as well. It's not substantial enough for the weight of full sized field camera, but perhaps the Travelwide would be okay.

[Corran]

Nice, got any photos made with your rig??

[konakoa]

Nice, got any photos made with your rig??

Sure. Sunset image is a double exposure on a single 4x5 color transparency. Black and white are digital camera images of 16x20 prints I made in my darkroom. You can stick your nose in the prints and the detail just keeps going. 90mm, 150mm, and 180mm lenses used for these photos.

[Drew Wiley]

One serious problem would be the film plane. I'd precisely adjust this for position using a depth micrometer and machine stock reaching the perimeter of the frame. Then there's the filmholder issue. It's not terribly difficult to make a vac filmholder. I prefer the ole expensive aluminum holders. Then you take the backside and epoxy-install reinforcing ribs to prevent the inner septum from deflecting under vacuum. Then drill the correct pattern of small holes thru the septum, install a little vac tube connection thru the end, and permanently seal in the back darkslide, airtight. Film can not only pop during a long exposure, but will never be held flat to begin with. Of course, glass plates were traditionally used due to this problem, and I see that someone is making a vac back for the P67 for widefield photog, though they want you to either use 220 film or strip the paper backing from 120 first. I just purchased a P67 300 EDIF lens, which is popular with MF and DLSR widefield photographers. For LF I'm sure I'd use some kind of Apo Nikkor process lens, though they'd be a bit slow due to needing to be used around f/11 or f/16 for optimal performance.

[konakoa]

A ordinary film holder modified for a gentle vacuum works just fine. I've made several. Just check beforehand that the septum of the film holder is at the correct depth. They do vary. A depth gauge is quick and absolute if you have one, yet it can also be done by simply taking daylight photos; critically focus the ground glass of the camera on a distant object (radio towers work great) with a high power loupe to verify focus, use the maximum aperture on the lens to take dof out of the test, make an exposure with the holder and examine the film after processing to make sure it matches.

[Corran]

Really nice shots konakoa.

[konakoa]

Thanks Corran. Appreciated. The images above really don't do the photographs any justice as they're so small. The detail really is incredible. 4x5 astrophotography can be done. You just have to be a little determined.