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06-12-2018, 07:10 PM - 1 Like   #1
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DA* 11-18mm f/2.8 is to have a defog option for astrophotography?

I don't know if this has been seen here before..

Apparently, the DA* 11-18mm f/2.8 is to have a defog option for astrophotography?
Got that from: First Hands-on photos of new HD PENTAX-DA* 11-18mm F2.8! | PENTAXever.com
Original: https://www.yaotomi.co.jp/blog/used/2017/10/hd-pentax-da11-18mm-f28.html

"The fundamental constriction of the hood mounting frame is designed not only for design but also for winding “string-like dew condensation prevention heater” for star shooting"

"A lens that I would like to sell as a starlit lens High resolution lens and high performance from aperture opening, high performance lens in which the point source in the peripheral area introduced as a “star-lens lens” appears as a point, that is, the aberration is suppressed as much as possible Expecting that a wonderful lens is a finished one I hear a story that considering the installation of “dew condensation prevention heater” to support it "

Can anyone here confirm this? Or is that website like 'The Onion' or something..


Last edited by FozzFoster; 06-12-2018 at 08:36 PM.
06-12-2018, 07:53 PM - 1 Like   #2
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Never heard of that site before ... suspicious?
06-12-2018, 07:56 PM - 1 Like   #3
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QuoteOriginally posted by jpzk Quote
Never heard of that site before ... suspicious?
well-known Japanese shop with blogs
06-12-2018, 08:23 PM - 1 Like   #4
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Interesting photo, why is the AF/MF on the lens body??

I thought that was on the camera body, change in direction? or wrong labeling? or something to keep the world occupied?

From the magical land of Australia
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06-12-2018, 08:26 PM - 1 Like   #5
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Interesting! Are these heaters a common thing in astrophotography, or something new?
06-12-2018, 08:47 PM - 2 Likes   #6
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Telescopes with secondary mirrors exposed to the elements i.e. Newtonian) do use such heating to reduce condensation. One can wire up some resistors, buy pre-made devices or use small hair-dryer type blowers to occasionally reduce the temperature differential as the cold air hits the secondary and chills it. The catadioptric design has the second mirror enclosed but heaters are still helpful, I understand.

edit - kendrickastro.com also makes heaters for the primary mirror; I'd never felt a need for that myself.
06-12-2018, 09:06 PM - 1 Like   #7
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QuoteOriginally posted by Greg1956 Quote
Interesting photo, why is the AF/MF on the lens body??

I thought that was on the camera body, change in direction? or wrong labeling? or something to keep the world occupied?

From the magical land of Australia
Greg
All DA* (and DFA*) lenses has this feature. It iwas introduced over 10 years ago when DA* 16-50/2.8 was released.
SMC Pentax-DA* 16-50mm F2.8 ED AL [IF] SDM Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database
06-12-2018, 09:11 PM - 1 Like   #8
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I think this lens is high on a lot of people's wish-lists so hopefully it isn't delayed as well.

06-12-2018, 09:33 PM - 1 Like   #9
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Dew heaters are a common thing for astrophotography in humid climates. The goal is to slightly heat the front element to keep it dry. A few degrees is enough.

Common dew heaters:
1) A wire with high electrical resistance, connected to a battery, often with a pulse controller to manage heat output and battery drain. Can be found places that sell astronomy equipment.
2) Disposable handwarmer and a rubber band to hold the handwarmer. Sold in skiing and hunting stores.

Lenses aimed at the night sky get colder than air temperature due to thermal radiation. The front glass is warmer than space so some of that heat tries to escape (similar to how sunlight heats things up, in reverse). Humid air then condenses on the cold lens (similar to how a cold glass collects water on the outside). Dropping night temperatures also contribute to dew collection because colder air can't hold as much water.

Use of a hood can reduce dew because it reduces the amount of moist airflow over the lens. That applies more to telescopes and telephoto lenses that can use a deep hood, than to wide angle Milky Way lenses.
06-12-2018, 09:35 PM - 1 Like   #10
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QuoteOriginally posted by Fogel70 Quote
All DA* (and DFA*) lenses has this feature. It iwas introduced over 10 years ago when DA* 16-50/2.8 was released.
A MF/AF clutch mechanism was first introduced even earlier than that. F* and FA* lenses had this feature, introduced from the late 1980's
06-12-2018, 09:39 PM - 2 Likes   #11
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QuoteOriginally posted by jimr-pdx Quote
The catadioptric design has the second mirror enclosed but heaters are still helpful, I understand.
In my experience, catadioptrics (Schmidt Cassegrain) collect the most dew. Both mirrors are enclosed and stay dry, but the front corrector lens is a big target for dew. A dew shield and/or heater is essential on humid nights.
06-12-2018, 10:03 PM - 1 Like   #12
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QuoteOriginally posted by DeadJohn Quote
In my experience, catadioptrics (Schmidt Cassegrain) collect the most dew. Both mirrors are enclosed and stay dry, but the front corrector lens is a big target for dew. A dew shield and/or heater is essential on humid nights.
Thanks for that clarification; I've only played with Newtonians. The corrector lens is a huge heat/cold sink indeed!
06-12-2018, 10:28 PM - 1 Like   #13
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This sounds like very, very interesting news.

QuoteOriginally posted by DeadJohn Quote
Use of a hood can reduce dew because it reduces the amount of moist airflow over the lens. That applies more to telescopes and telephoto lenses that can use a deep hood, than to wide angle Milky Way lenses.
Yes, the big, exposed front element of a UWA/fisheye lens is a dew nightmare. My Rok 8mm needs a blower which I haven't taken the time to build yet.

I also have a newtonian telescope, but all the dew collects on the barrel, not on the mirrors, so I just let it in a ventilated area for a few days after use.

That's the reason most telescope arrays are on top of dry, deserty locations. Atacama being one of the driest.

If this feature really is getting incorporated into the lens, then I'm taking my hat off to Pentax. They'd be stepping up their astro game, which already makes their cameras the go to (astro tracer), to a whole new level.
One would certainly need a few spare batteries, since I think that would drain some current, but it's easier than buying and lugging an external heater, which still requires a battery. And it would be all incorporated into just one system. Bravo!

Rainforests, mangroves, swamps and wetlands here we come!

Gesendet von meinem Mi A1 mit Tapatalk
06-12-2018, 11:20 PM - 1 Like   #14
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Yes - the most intriguing 'evidence' to my mind is, as the japanese writer points out, that the pictures all have the rear cap on - if there was an extra contact point - for whatever reason - people would be all over it in an instant (not me, I wouldn't even notice )
06-13-2018, 02:33 AM - 1 Like   #15
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I read this as a design choice in the hood bayonet mount to allow some type of external accessory (that's also externally heated) attached, not as an electronic feature of the lens itself. When I look at the hood and the mount however, I don't see anything really different from the hoods/mounts on other premium Pentax lenses. Or am I missing an important bit?
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