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Old 17-12-2018, 07:52 AM
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Astrofriend (Lars)
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Astrofriend is offline
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 235
What field flattener do you have? My experience is that it is very difficult to get an image with low vignetting and sharp stars all the way out to the corner at full frame.

The Pentax 67 & 645 ED lenses I always read that they deliver top quality for normal photographing, good to hear that they deliver also in astrophotographing. I know a Pentax 67 ED 400 f/4 for sale.

What a lot of details, no one sales the Borg in Sweden nowadays, have to import then with taxes and customs fees.

Lot of planning here and I have decided to my light weight mount it must be with a focus motor, then only Canon, Sigma etc lenses are avalible.

Earlier I also put in an offer on a Canon 400 mm f/2.8, very used but with good optics, didn't get it. I don't think this lens is usable at f/2.8, more f/4 at full frame. But this is also a bit to big to my portable equipment. Max 300 mm and f/4. It was more that it had been fun to have a lens like that once a lifetime.

My permanent EQ6 and TS 130 f/7 I maybe can have an extra shorter telescope or lens in parallel with. In that case I can have a separate focus motor when the weight and simplicity is not that important. Here the Pentax 67 ED 400 f/4 lens fit perfect.

I have been prepared now one week to take photos of comet 46P/Wirtanen, clouds every night.

Luckely I have other hobbies than astronomy :-)

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