Own a telescope? You want this light!

Dude Dudeson

Enlightened
Joined
Jun 8, 2009
Messages
522
Location
Sacramento, California
I posted this somewhere else but figured some here might find it useful as well. I use some terms and explanations for non-flashaholics in the original post elsewhere...

I bought a headlamp (link at the end) with a main beam and two red LED's on either side of it.


The red LED's are intended to alert others to your presence (night jogging or biking), so they aim to the sides, but by wearing the headlamp sideways they're perfect for close up work with absolute minimal excess light (as you want when using a telescope). Then when it's time to pack up just wear it normally. An extremely minor extra step in the big picture of a telescope session...

I'd seen other models that have the reds aimed forward, but some problems I had with those were:

1. Main beams designed like typical flashlights - hotspot in the middle, intended for distance, terrible for close up work. Or no way at all to even know what the beam profile was. This one is advertised as having a wide angle beam. It's not a pure flooder ("wall of light"), it does have a bit of hotspot, but still FAR better for close work than your typical flashlight beam.

2. Three battery design. I dislike devices that use odd numbers of batteries, plus I wanted small and light as possible. I also intend to use this thing at work, so I use Eneloop rechargeables that are a lot heavier than regular batteries. This one uses 2 AAA's.

3. Either too cheap or too expensive. I wasn't going to spend over 40 bucks, nor was I going to buy something rock bottom for ten. This one was $29.

4. Most important of all for a telescope session - INDEPENDENT buttons for the main and the reds. No cycling through modes to get to the reds (as in having to first fire up the main beam). OH, and also a switch guard to prevent accidental activation.

5. No tilt adjustment. An absolute must for close work, especially when said work involves looking downward.

I imagine something else must exist that's just as good for this application, but within my above listed parameters this is PERFECT.

https://www.fenixlighting.com/produc...hl15-headlamp/
 
Last edited:

MeMeMe

Banned
Joined
Aug 27, 2018
Messages
125
Not really ... most red LEDs really don't help that much for night vision, they are just a lot dimmer. You would do just as well with a really dim white light.

Reds only help if they are >650nm.
 

Nev

Banned
Joined
Mar 25, 2017
Messages
195
Most red led lights are more like orange , they look red until you put a proper red light next to them like a zebralight photo red.
 

iamlucky13

Flashlight Enthusiast
Joined
Oct 11, 2016
Messages
1,139
Not really ... most red LEDs really don't help that much for night vision, they are just a lot dimmer. You would do just as well with a really dim white light.

Reds only help if they are >650nm.

Red light helps if you need to preserve your night vision at higher light levels than what is needed simply to move around safely.

At extremely low light levels, we have poor visual acuity, making tasks like reading (such as a star chart) more difficult. Red light allows you to get away with increasing the light intensity enough to read, while minimizing the impact to night vision. However, using red light means effectively no color discrimination, and you can expect poor contrast if you're not viewing black and white or saturated red objects.

I don't think your statement that only 650nm or longer wavelengths help is accurate. Maybe that's more relevant to dark room work where you need to avoid wavelengths that expose the photopaper? As far as I've been able to find, the bleaching effect of light on our night vision decreases progressively with increasing wavelength, so the difference between 600nm and 650nm light should be a lot smaller than the difference between 450nm and 600nm light.
 

Nev

Banned
Joined
Mar 25, 2017
Messages
195
I posted this somewhere else but figured some here might find it useful as well. I use some terms and explanations for non-flashaholics in the original post elsewhere...

I bought a headlamp (link at the end) with a main beam and two red LED's on either side of it.


The red LED's are intended to alert others to your presence (night jogging or biking), so they aim to the sides, but by wearing the headlamp sideways they're perfect for close up work with absolute minimal excess light (as you want when using a telescope). Then when it's time to pack up just wear it normally. An extremely minor extra step in the big picture of a telescope session...

I'd seen other models that have the reds aimed forward, but some problems I had with those were:

1. Main beams designed like typical flashlights - hotspot in the middle, intended for distance, terrible for close up work. Or no way at all to even know what the beam profile was. This one is advertised as having a wide angle beam. It's not a pure flooder ("wall of light"), it does have a bit of hotspot, but still FAR better for close work than your typical flashlight beam.

2. Three battery design. I dislike devices that use odd numbers of batteries, plus I wanted small and light as possible. I also intend to use this thing at work, so I use Eneloop rechargeables that are a lot heavier than regular batteries. This one uses 2 AAA's.

3. Either too cheap or too expensive. I wasn't going to spend over 40 bucks, nor was I going to buy something rock bottom for ten. This one was $29.

4. Most important of all for a telescope session - INDEPENDENT buttons for the main and the reds. No cycling through modes to get to the reds (as in having to first fire up the main beam). OH, and also a switch guard to prevent accidental activation.

5. No tilt adjustment. An absolute must for close work, especially when said work involves looking downward.

I imagine something else must exist that's just as good for this application, but within my above listed parameters this is PERFECT.

https://www.fenixlighting.com/produc...hl15-headlamp/

I hope you're not one of those people who walks over to other astronomers at star parties with your red (orange) 50 lumen headlight.
That's really annoying.headlights are good for the person wearing them but not good for others around you.
 
Last edited:

Dude Dudeson

Enlightened
Joined
Jun 8, 2009
Messages
522
Location
Sacramento, California
I hope you're not one of those people who walks over to other astronomers at star parties with your red (orange) 50 lumen headlight.
That's really annoying.headlights are good for the person wearing them but not good for others around you.

Nope, I've been on a Flashaholic hike with people from this board circa 2009 in the Santa Cruz mountains, but I've never been to a star party. I do know well enough to not make such a newbie mistake though when I do eventually go to a star party. We had like 15 people with SERIOUS "candlepower" (pun not intended) and never ruined anyone's night vision (in trail terms, telescope session, oh yes we'd have all been hated!).
 

MeMeMe

Banned
Joined
Aug 27, 2018
Messages
125
Red light helps if you need to preserve your night vision at higher light levels than what is needed simply to move around safely.

At extremely low light levels, we have poor visual acuity, making tasks like reading (such as a star chart) more difficult. Red light allows you to get away with increasing the light intensity enough to read, while minimizing the impact to night vision. However, using red light means effectively no color discrimination, and you can expect poor contrast if you're not viewing black and white or saturated red objects.

I don't think your statement that only 650nm or longer wavelengths help is accurate. Maybe that's more relevant to dark room work where you need to avoid wavelengths that expose the photopaper? As far as I've been able to find, the bleaching effect of light on our night vision decreases progressively with increasing wavelength, so the difference between 600nm and 650nm light should be a lot smaller than the difference between 450nm and 600nm light.


This is pretty much all wrong and while you may think my statement about > 650nm is not accurate, you would again be wrong.

Bleaching does decrease with wavelength assuming similar power levels, but our visual response is not consistent w.r.t. power, it is consistent w.r.t. photopic or scotopic lumens, hence there is little benefit to short wavelength red light compared to just a really dim light ... except the really dim light is probably going to have more contrast. You may find lots of ad-hoc statements that agree with you, but that is what they are, ad-hoc.

If you use >650nm, it is possible to stimulate the cones ... allowing you to read star charts, etc., without stimulating the rods.
 
Top