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Red flashlight for astronomy

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#26 Cestus

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Posted 23 October 2020 - 11:41 AM

https://www.cloudyni...210619-kfiscus/

 

   He's the gent that makes them/ sells them     Regards, Pat

Thanks.



#27 ihf

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Posted 23 October 2020 - 01:30 PM

Some more red 660nm lights. While more pricey, the Zebralight is a headlamp and can be regulated extremely far down.

 

Sofirn C01R (USD 10-15)

Simple 3 Modes: High: 36 lm(1h, 30min), Mid: 9 lm(14h, 43min), low: 0.5lm (25h, 11min). Twist the light head to switch the mode Group ( low- Mid- high)

 

Zebralight H502pr Photo Red AA Flood Headlamp (USD 54-70)

Low:         L1   1 Lm (4 days)   or    L2   0.13 Lm (2.8 weeks) / 0.02 Lm (1.8 months) / 0.003 Lm (2.8 months)

 

https://www.reddit.c...vs_sofirn_c01r/


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#28 Gordon Rayner

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Posted 24 October 2020 - 12:02 AM

There was an article about night vision preserving lights in Sky and Telescope within 5 years (?), maybe within 10 years ago. It suggested that red was not ideal, at least in some conditions, IIRC.

#29 Jon Isaacs

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Posted 24 October 2020 - 02:26 AM

There was an article about night vision preserving lights in Sky and Telescope within 5 years (?), maybe within 10 years ago. It suggested that red was not ideal, at least in some conditions, IIRC.

 

There was a discussion of the article in one of the forums here. The actual testing for the hypothesis was poorly done, a computer monitor was used to provide the colors so the colors used were not actually anything like monochromatic but synthesized and the red used was not a deep red. 

 

It seemed pretty much discredited.  

 

Jon



#30 ihf

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Posted 24 October 2020 - 10:23 AM

Here is a good article on the subject: "THE RELATIVE EFFECTIVENESS OF RED AND WHITE LIGHT FOR SUBSEQUENT DARK-ADAPTATION" by

S. M. Luria and David A. Kobus. It discusses this in the context of surfacing a submarine into a dark, starry, quarter/full moon night. You can read the summary of the paper. Also a discussion here and here.

 

My takeaways are

1) A starry sky is much brighter than dark adaptation.

"Another question now arises. Is complete dark-adaptation always necessary? Probably not. Absolute threshold is around .00001 to .000001.mL for the average young man (37), although this will vary somewhat with age (38), the size of the target (39), and other variables (40, 41). However, the presence of starlight raises the brightness of the sky to .0001 mL, and a quarter moon raises it to .001 mL. This is two orders of magnitude greater than absolute threshold. Furthermore, a full moon raises the brightness of the sky an additional order of magnitude (.01mL)." [page 12]

 

2) Red light still damages night adaptation. It damages a little less than white light, but both do damage at any light level.

"Despite the fact that red-adaptation is not equivalent to dark-adaptation, it is still better for subsequent dark-adaptation than exposure to an equivalent brightness of white light." [page 11]

 

3) Dark adaptation after low levels of red lights can be as fast as 2-3 minutes while with white light (at levels discussed in the paper) requires 90 seconds more (pages 11 to 14).

 

4) There are clear drawbacks to using red light. For instance

"There is little question that the long wavelengths produce some physiological discomfort and degradation. They require more accomodation to focus them on the retina, which could be uncomfortable for older or far-sighted crewmen." [page 12, bottom]

 

The paper argues there are clear benefits to accepting this 90 seconds penalty. I think I agree on this. For instance I regularly hike in the darkness and have better contrast and see details better with full spectrum (high CRI) light - even and especially at very low output levels which barely illuminate the trail.

 

I think what some people get wrong on this topic is they assume that using red light causes no damage at all and they can blast it at full power. It is much less damaging at high levels than white light (graph on page 13), but there is still damage and no astronomer should ever use such bright lights. On the left part of the graph on page 13 the damage and recovery times between red and white light is very similar. So what astronomers need is a light (any light really) that can be regulated down. Way down.


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#31 ihf

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Posted 24 October 2020 - 10:25 AM

All this said I've ordered the red Zebralight. Because, why not have another light? And it does promise to regulate down. ;-)



#32 Chuck2

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Posted 24 October 2020 - 11:12 PM

The two I use:

https://www.amazon.c...t/dp/B005NXPVKS

 

https://www.amazon.c...8-6&tag=mh0b-20

 

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#33 Albie

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Posted 25 October 2020 - 08:47 AM

I have had one like this one for years .  It does the job well enough .https://www.astronom...flashlight.html

 

A few years ago I wanted to buy myself a decent high lumen flash light and came across the Pelican 7600   It's a wonderful flashlight . Very bright(crazy bright),programmable , chargeable and has separate green and red leds . https://www.ocli.ca/...-led-flashlight


Edited by Albie, 25 October 2020 - 08:49 AM.


#34 Cali

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Posted 29 October 2020 - 08:53 AM

BE SURE to remove the batteries in your flash light after use. I left my batteries in and after a few months of non use the batteries turned into crud and I had to toss the flash light.

 

If you use your flashlight every night, no problem. I now remove the batteries, put them in a plastic bag and rubber band it to the flash light.

 

Just say'in.

 

- Cal


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#35 PhilA

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Posted 29 October 2020 - 09:35 AM

There is a good one, IMHO, on Amazon called a Carson RedSight. It is all red light with two brightness settings and costs a whopping $6.59. Runs on 3 AAA cells. I usually have one on a lanyard and hang it around my neck. Also have a red head light, but end using the flashlight more often.



#36 Cestus

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Posted 29 October 2020 - 11:07 AM

I decided to go ahead and get a fiscus light. Pay a bit more, but get one that comes highly recommended. Thanks all.


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#37 PEterW

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Posted 29 October 2020 - 12:22 PM

Lumens are no use as they’re just a measure of total output, what you want is lux, the brightness that hits a surface at a given distance and takes into consideration the beam spread.... a laser would help you read charts a long way from the laser, but spread the same light over a whole hemisphere and you’ll not be able to read a chart mere inches away.
Dim is the key, avoid light when you can, use an eyepatch to protect one eye.... lots of stuff to do. Just watch out that fellow observers don’t have red searchlights strapped to their foreheads!

Peter
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#38 ihf

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Posted 29 October 2020 - 02:11 PM

I agree with everything, except that if you buy a flashlight you purchase lumen (output). When you use the flashlight you see lux (distant area brightness). As the brightness depends on ambient and flashlight head geometry[*] all a user can do with a light is dial in the lumen.

 

[*] Flood or throw mirror/lens assembly.



#39 Herr_Alien

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Posted 30 October 2020 - 12:11 AM

One can also increase the distance between the flashlight and the chart, thanks to the inverse square law.

#40 eyeoftexas

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Posted 30 October 2020 - 07:51 AM

 

My favorite is this Zebra one. Strictly red. Several levels of intensity. Takes a single AA battery. Last a good long time.

 

 

I just received my Zebra (same as noted: http://www.zebraligh...amp_p_175.html#).  It takes some getting to use to the various number of clicks to set light levels, but the second level of low red (L2) is very dim!  I compared it in the dark and found it almost as dim as the dimmest setting on Ken Fiscus' light, which I received a few weeks ago (yes, I have many red lights).  I think this will be a nice combo, with the Fiscus light laying flat on the Star Atlas and the Zebra light on the head band.


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#41 ihf

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Posted 30 October 2020 - 09:35 AM

My Zebralight is still in the mail. IIUC L3 is supposed to have a total of 3 submodes. I assume you are comparing with the first mode of L2 (0.13lm)?



#42 eyeoftexas

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Posted 30 October 2020 - 10:15 AM

My Zebralight is still in the mail. IIUC L3 is supposed to have a total of 3 submodes. I assume you are comparing with the first mode of L2 (0.13lm)?

 

I think so.  There are a lot of variations on the number/type of clicks to get to the various modes.  I know that I now have low set to a lower setting than the starting one (L1), and so I assume like you it is L2 = 0.13 lm.  If that is the case, I think the programmable L2 (0.02 lm) might be dimmer than the Fiscus light.  Either way, I think they make a nice complimentary pair.


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#43 astrohamp

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Posted 30 October 2020 - 10:34 AM

Been using two original CMG Infinity single AA red lights for nearly two decades. A bit bright but a favorite.  Unfortunately just found one with a fused AA cell inside that leaked so bad I don't think I will be able to recover from it.  Bummer.

Earlier I purchased an Explore Scientific Astro R-Lite Red Flashlight - ES-FL1001 as backup. 
It is bigger, bulkier, has 4-level brightness adjustable, single AA cell, and I find it acceptable for low level lighting/path finding. 

I am probably going to finally purchase a ZebraLight H502pr Photo Red AA Flood Headlamp to replace the lost CMG.
The H502pr can go extremely dim (0.003 lumens) or as a dreaded headlamp (100 lumens) using a 650-670nm red led.  It is more than double the ES-Astro R light although I often require a headlamp to access (200' walk) my equipment in the dark.

Being less of a visual observer and ruining my dark adaption using an EAA monitor I still need to be conscious of the folks at star parties. 



#44 ihf

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Posted 07 November 2020 - 03:43 PM

I finally got the Zebralight and I am impressed by it. The three submodes work as advertised. I would say the lowest level might be too dim for anything except finding the light, but I will need to try in the field. I find the UI easy enough and don't seem to go into high mode by accident. Not sure how much I will like the red compared to High CRI output.



#45 ihf

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Posted 13 November 2020 - 08:29 PM

The Astrolux A01 arrived from China. While the manual states Nichia 219C and 0.14lm, the lowest output is much brighter than my Reylights and the Zebralight. Probably a full lumen. I'd say better to stay with Zebralight for build consistency and lowest programmable output.



#46 Sterngucker

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Posted 14 November 2020 - 12:02 PM

The US Army issue MX991 with a LED upgrade and the red filter works well, as does my old Energizer headlamp.

 

YMMV



#47 Lee D

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Posted 14 November 2020 - 12:56 PM

I use the tiny LRI Photon Freedom Micro Covert red. The Covert means it has a tiny snoot over the LED. Brightness can be adjusted from not very bright to not very bright at all. I add the shoelace-type necklace they sell to each one. Clips to attach to hat or whatever are also available. 



#48 Gastrol

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Posted 17 November 2020 - 01:56 AM

I took one of my backpacking headlamps, a ThruNite TH20, and applied red fingernail polish to the lens.   What I like about this single AA or 14500 battery lamp is that light output is infinitely variable and once you set the intensity it stays at that setting when you click back on.  There is no cycling thru different brightness.    Large push button switch, glove friendly.   To change intensity just hold down same button and watch light gradually increase or decrease until desired level and you’re set.    A single AA or 14500 battery will last days left on at the dimmest setting, about 1.6 lumens.



#49 litesong

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Posted 17 November 2020 - 09:26 AM

Im the dinosaur. I use a regular flashlight with red plastic (from a plastic grocery bag) cut and placed just behind the glass protector/diffuser. Has worked well for 40+ years...no reason to change.

30 years ago in our small astronomy business, we scraped out the white lights and installed red LEDS. Got the brightness right to suit customers. Sold hundreds of flashlites.


Edited by litesong, 17 November 2020 - 09:27 AM.


#50 Crusty99

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Posted 18 November 2020 - 04:48 AM

I have been using two Rigel Starlites for over 10 years each. One is red, the other is green.


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