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I bought another 300 mm lens as an alternative to the Canon 300 mm L lens I already have. The main reason is to achive a lower vignetting. I have very positive experience from an earlier medium format lens. This is the Pentax 645 300 mm ED f/4 lens with good reputation. If I get some positive results from this lens I maybe replace my Canon 300 mm lens with this one.

Here is some photos and data about the lens:
http://www.astrofriend.eu/astronomy/projects/project-pentax645-300ed/01-pentax645-300ed.html

I bought it mostly because I'm curious about it and want to test it. It's more than ten years older than the Canon lens.

Lars

Edited by Astrofriend
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  • 1 month later...

My Canon 300 mm lens setup is ready for some test in the night, I have already done some test in the opening of the clouds and could see that it works very good.

 

Now I planning for my next 300 mm lens, the Pentax 645 medium format f/4 ED lens. The last days I have 3D-printed two tube rings. It feels very stable and I hope it will not fall apart during the night.

 

This is how they look:

http://www.astrofriend.eu/3d-printing/pentax645-300mm-bracket/01-pentax645-300mm-bracket.html

 

Only the 180 teeth pulley missing for the motor focus.

 

/Lars

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  • 2 weeks later...

First light with the Pentax 645 300 mm ED f/4 lens.

http://www.astrofriend.eu/astronomy/astronomy-photo/galaxies/m101/m101-galaxy.html

Click on the image to bring up the full resolution image and inspect the corners. Look very good to me except one of the corner.

This old medium format lens is impressive. There are not many old cheap medium format lenses with ED glass elements, they are too old for that. The never APO medium format lenses are very expensive and have electronic aperature and focus which can be complicated to use in an astrosetup.

/Lars

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7 minutes ago, Astrofriend said:

First light with the Pentax 645 300 mm ED f/4 lens.

http://www.astrofriend.eu/astronomy/astronomy-photo/galaxies/m101/m101-galaxy.html

Click on the image to bring up the full resolution image and inspect the corners. Look very good to me except one of the corner.

This old medium format lens is impressive. There are not many old cheap medium format lenses with ED glass elements, they are too old for that. The never APO medium format lenses are very expensive and have electronic aperature and focus which can be complicated to use in an astrosetup.

/Lars

Utmarkt, tack for forkaringen. 

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