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11/9/2018 9:21:38 PM
Posted: 8/12/2018 10:18:48 AM EST
Need suggestions please. I set the camera up last night, pointed North-North East. Set the camera (Nikon D7000) to take 100 (15 second) images every 2 min. The last hour or so, the lens started getting condensation and blurred everything. I have heard to use hand warmer packs wrapped around the lens.
Would this be the best route to use to prevent the condensation on the lens?
Link Posted: 8/12/2018 10:41:18 AM EST
[Last Edit: 8/12/2018 10:42:24 AM EST by captainpooby]
Yes.

It may work but whatever you do, do not use any anti fog stuff.

ETA: If you aren't using a clear filter, the use one. It will help.
Link Posted: 8/12/2018 10:49:07 AM EST
Make sure you are using a lens hood, and also remove any UV or protective filter you may have. The hood will help to cut down some of the thermal radiation loss that drops the glass below the dewpoint, causing condensation.
Link Posted: 8/12/2018 10:58:17 AM EST
You also need to increase your duty cycle. A 15 second exposure every 120 seconds means that you are missing 87% of what's happening. You're going to have to get very lucky to capture something. Maybe see if you can get 15 second exposures every 17 or 18 seconds? Try this in a closet with your wristwatch to see what the minimum interval is. If you set your interval too short, it's going to drop frames (with the interval timer in the loop, the camera won't be able to get the mirror re-opened for the next shot, so it sits it out, waiting for the next interval), and gives you a 50% duty cycle, at best. For instance, for star trail stacks, I set my D800 for a 30 second exposure at 33 second intervals. A 31 second interval guarantees dropped frames, and a 32 second interval sometimes causes frames to be dropped.
Link Posted: 8/12/2018 11:59:14 AM EST
[Last Edit: 8/12/2018 12:00:04 PM EST by GlockSpeed31]
Yes, was using a lens hood with no filters, just bare lens. I can set the intervals to 18-19 secs with an exposure of 15 sec.
Link Posted: 8/12/2018 12:09:12 PM EST
Make sure your camera is acclamating slowly. Don't bring it from cool inside air to warm outside air quickly. Let it sit In The garage or vehicle for an hour or 2 before you set it up.

Not sure if this is your problem but it can cause fogging.
Link Posted: 8/12/2018 12:17:34 PM EST
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Originally Posted By aeroworksxp:
Make sure your camera is acclamating slowly. Don't bring it from cool inside air to warm outside air quickly. Let it sit In The garage or vehicle for an hour or 2 before you set it up.

Not sure if this is your problem but it can cause fogging.
View Quote
It did fog up at first when I took it outside. I left it out for about 30 min and then went and did a final wipe of the lens. It didn't fog anymore until about 3 hours later, which was about 1am.
Going to try again tonight, weather permitting. Use a quicker interval, probably 30 sec for a 15 sec exposure and wrap a heater pack around the lens.
Link Posted: 8/12/2018 12:54:53 PM EST
What type of lens?
Link Posted: 8/12/2018 2:22:40 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By L_JE:
What type of lens?
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Tamron 28mm-200mm f/3.8-5.6 72mm

My other wide angle is Tamron 17-50 f/2.8 but have some problems with the front retaining ring staying tight, which allows dust into the front element.
Link Posted: 8/12/2018 3:31:20 PM EST
Dew point got you. This is a common problem with telescopes. I use a Kendrick heater on my 10" Schmidt-Cassegrain.

Here is an article from Sky and Telescope on the subject. You can probably fashion some kind of dew shield for your lens but you'll need to be careful with the length and flare of the shield to avoid vignetting. There are heaters for guide scopes and such, haven't really looked but you can probably find one small enough for a camera lens. They work great.

Don't be put off by the term heater. They don't really heat things up so much as they keep the lens warm enough to avoid your lens reaching the dew point and having condensation start forming.
Link Posted: 8/12/2018 5:15:43 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By GlockSpeed31:
Tamron 28mm-200mm f/3.8-5.6 72mm

My other wide angle is Tamron 17-50 f/2.8 but have some problems with the front retaining ring staying tight, which allows dust into the front element.
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Discussion ForumsJump to Quoted PostQuote History
Originally Posted By GlockSpeed31:
Originally Posted By L_JE:
What type of lens?
Tamron 28mm-200mm f/3.8-5.6 72mm

My other wide angle is Tamron 17-50 f/2.8 but have some problems with the front retaining ring staying tight, which allows dust into the front element.
Ok, so your hood should provide decent coverage.

If you have some hand warmers, cut an old sock, put it around the lens hood, and stick some hand warmers in between the sock and the hood. The hand warmers will breathe ok through the sock.
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