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Large format astrophotography

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#26 Nightfly

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Posted 09 November 2013 - 08:02 PM

Nice find Michal. Looks like some fine work. Looonnnggg exposures for sure.

#27 Hikari

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Posted 20 November 2013 - 11:26 PM

Fuji made 400mm and 600mm telephoto 4x5 view camera lenses, so 300mm is not the upper limit. Since they are telephoto designs, the flange distance is less than the focal length. The 400mm I believe has a shorter flange distance than the 300mm. They also produced a 1,200mm lens, but at f/24, it is slow.

#28 Kona

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Posted 21 November 2013 - 03:29 PM

Certainly Hikari! :) There are definitely longer lenses out there--I put forward 300mm merely as the most practical limit in terms of what a standard large format camera can handle and the availability of the lenses. Likewise, a camera with a 300 will readily work on the majority of equatorial mounts as it will be in the four to ten pound weight range.

Anything over 300 is definitely in the area of specialized use. The lenses are unusual and harder to find. Extra long bellows beyond the normal are needed as is physical extension of the camera. Vibration becomes an issue at these magnifications, so extra-solid camera support is also mandatory.

As an example I've attached a photo of my 600mm f/9 telephoto lens. To make this optic work it needs a minimum of 480mm of bellows. To focus closer than infinity (such as landscapes), it needs even more bellows than that. The lens by itself is five pounds. The metal camera and extra fittings place the whole setup around twenty pounds of weight. The camera assembly in its entirety is over two feet long--for a camera that's not compact by any means. At this magnification vibration in the system can easily render the image on film unsharp so it also needs very solid support.

To use this lens for astrophotography it would need a substantial equatorial mount far more robust than what I have. While the requirements of this lens on a camera are tough, it is an amazing optic. (This lens allows me to isolate details in landscape photos with great clarity). Yet it's not for everyone--one look at the setup readily shows the extraordinary requirements needed for a long focal length optic.

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#29 whwang

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Posted 22 November 2013 - 08:20 AM

Wow. This is very impressive, Kona.

I quit film astrophotography not a long while ago. Until 2009, I shoot medium format. The reason is exactly what you said, print quality (although I don't do real dark room work myself). I thought about going to large format for years, but I'd never pulled the trigger, primarily because the limited choices of films. Another reason is the worry of camera flexure. I was not convinced that large format cameras can be rigid enough for hour-long exposures. (Your results proves me wrong.) To overcome this, I was thinking about making an astrophoto-only large format camera without using any moving parts like the monorail. I never had a chance to actually do this. On the other hand, I mosaicked digitized medium format images (from 2 6x7 images, to mosaics as large as 20 6x7 images) to achieve the print quality that's equivalent to large formats.

Now I am a completely digital shooter, but your pictures remind me the good old days. Hope one day I will pick up film again. Please do share with us if you make new pictures.

Cheers,
Wei-Hao

#30 galaxy_jason

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Posted 22 November 2013 - 10:10 AM

That is going to flex like crazy during a long exposure on a moving mount. Not only flex relative to the tracking mount but the lens relative to the film plan

#31 Kona

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Posted 22 November 2013 - 03:48 PM

Thanks Wei-Hao! Much appreciated to hear your thoughts.

Jason, that's very likely true. That a normal large format camera with all the moving and folding parts can be used at all for astrophotography still strikes me as amazing. Every instinct would say it couldn't be done and yet surprisingly it can.

The 600 is an extreme example. It's a seriously long lens on a 4x5 and rare to see. Its use is within possibility yet I figure with my equatorial mount it would also be about as stable as a tank balancing on toothpicks. That's why I suggested 300mm as the comfortable and practical limit. I've successfully used my 300mm f/5.6 (pictured at the beginning of the thread) for years without problems.

#32 gillmj24

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Posted 26 November 2013 - 08:00 AM

Is it an 8x10 lens?

#33 Hikari

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Posted 26 November 2013 - 02:22 PM

Kona, the Horseman is a fine camera and the 600mm a fine lens.

#34 Kona

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Posted 28 November 2013 - 12:46 AM

Sure is Gillmj! I primarily use it on the 4x5.

Thanks for the compliment Hikari. The Horseman camera is a pleasure to work with. It's my hope to continue to put it to good use for many, many more years to come.

#35 sc hokie

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Posted 06 December 2013 - 02:16 PM

Very nice presentation! Definitely food for thought.

#36 Mopman

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Posted 09 December 2013 - 03:32 PM

Thanks KONA! :bow: You motivated me to assemble my f4 / 24" 4x5 film camera. I drug it out last night and it does seem to focus and have resonably decent optics. You can't see it in the attached pic, but it has an old 2.7" AP focuser. Hopefully images to follow soon (weather is not looking good). Gary

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#37 Nightfly

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Posted 10 December 2013 - 06:10 AM

Looks like a solid setup. Load some Acros 100 in it and make some wide-fields for us to gawk at! Does the 2.7" focuser allow full 4x5 coverage?

#38 Mopman

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Posted 10 December 2013 - 10:22 AM

That is a very good question!!! I could not tell in the driveway, bye eye, what the image covered. It was 10* F with wind ... I'm sure the neighbors think I am insane :roflmao: I might start with HP-5 that I need to burn up; Acros 100 is on my list to Santa though. BTW, this setup has a nifty shutter (air bulb control) and the AP focuser should allow attaching other goodies (flattener, filters, Barlow). Thanks for the encouragment Nightfly. I sure love your work. :bow: Gary

#39 Nightfly

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Posted 10 December 2013 - 06:51 PM

Your too kind Gary. I've been off film for over a year. Lots of things actually. Back again soon.

The 2.7 focuser worked well for 6x7 work if I remember correctly. I think the 4" focuser was used for 4"x5". Either way, I'd like to see what your getting with this setup. I've contemplated a project using a fast Aero Ektar or equivelent lens and a rigid lensholder with 4x5 film holder.

Post 'em when you get 'em.

Jim

#40 Hikari

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Posted 10 December 2013 - 08:47 PM

4" focuser is for medium-format 6x7. You will a 6" focuser for 4x5.

#41 Mopman

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Posted 11 December 2013 - 01:29 AM

I did some playing in the garage tonight. The image is a circle about 90 mm in diameter. Looks to be limited by my film holder/shutter assembly as much as the focuser. I could not tell if there is vignetting. I think 90 mm translates to about 8* FOV with the 24" Focal Length. Thanks! Gary

#42 Nightfly

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Posted 11 December 2013 - 07:18 PM

Sounds like it would just cover a 6x7 frame (89mm image circle) and give a circular field on 4x5 sheet film. Not too shabby just the same. Field illumination might be a different issue as well as aberrations. You'll have to shoot it and find out!

Fun stuff Gary.

#43 Mopman

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Posted 12 December 2013 - 11:12 AM

Should be fun :) There might be a Version 2 in the works ;)
Clear Skies!

#44 Nebhunter

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Posted 14 December 2013 - 08:07 PM

Gary this is great new. Interesting project and I hope it works for you. Another option might be to get a film back for the 4x5 in 6x7 or 6x9. That way you can shoot 4x5 and switch to another film in MF for B&W or E200. Good luck shooting my friend.

Igor

#45 Mopman

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Posted 15 December 2013 - 04:49 PM

Thanks Igor!!! Good idea; my Pentax 67 body should thread right on. I think I have a Mamyia 6 x 9 film back around here somewhere I could adapt.

#46 Stellarfire

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Posted 22 October 2014 - 08:13 AM

Hi Kona,

 

Interesting presentation of your film-based widefield astrophoto technique and equipment. Very impressive, thank you for sharing! 

 

Stephan



#47 Kona

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Posted 30 October 2014 - 01:11 PM

Thanks for the kind words Stephan!








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