HOW TO MEASURE SKY QUALITY

Hi Tsula, as ever, clear concise information. As someone who is dogged by light pollution and bad skies anything relevant to better seeing is of interest! I dream of moving to a dark sky area one day! I was shocked to read you’d had such a bad accident. I’m so glad you are alright, remember, equipment can be repaced….. you can’t be, so be sure to take care of yourself. I wish you well, what a year you’re having….stay positive, it can only get better! Here’s to dark skies for both of us! 🤗✨🌙

very true i got used the LP maps before the bortle scale came out. In many of my videos i just used the color of the LP map. like what red orange, these are rough gauging but it just gives an idea. The Bortle rating was always wrong to me too BUT its what almost everyone is used to now so i now say. Iam located in a white zone or bortle 8, my country setting is a grey zone or a bortle 2 zone. That way most understand what iam talking about. Cheers

Excellent and clear explanation for a key element of any astro activity.

Very enlightening and interesting video. Have taken all on board because you got it over so well. Thank you for sharing.

Your video was fantastic and I enjoyed it. I do need to get a Unihedron Sky Quality Meter unit. So much quicker and can be quantified. Awesome:)

To judge brightness limit with the naked eye you must have your eyes well dark adapted. They say takes about 40 minutes in complete darkness to have our eyes perfectly dark adapted. And then you would take your sight at the zenith without seeing absolutely nothing else. I agree, it’s time consuming as you say.

Thank you for making this very interesting video, I learned a lot Tsula!

Very well explained and presented. Thank you! 😎👍

speaking of sqm, in 1 month i'm going to head up to wyoming for 2 months, ungh, i need to put together a rig and work out it's kinks and quick if I'm going to get any imaging done while I'm there.

Thank you Tsula.

I'm puzzled by this paragraph in the SQM meter's user guide: "TYPICAL READINGS: Magnitudes per square arc-second is a logarithmic measurement. Therefore large changes in sky brightness correspond to relatively small numerical changes. A difference of 1 magnitude is defined to be a factor of 100^1/5 [the number 100 lowered to the 1/5 power] in received photons. Therefore a sky brightness 5.0 mag/arc-sec² fainter corresponds to a reduction in photon arrival rate of a factor of 100." I'm not a mathematician, and I don't get this math at all. I understand why we're dealing with 100 instead of 10, because we're dealing with area instead of pinpoints. But how can a sky brightness five magnitudes dimmer be only 100 times dimmer? Is the 5.0 a typo for 1.0?

I absolutely can see mag 6.5 stars in Bortle 4. I think his scale is very accurate, and have seen examples of all his classes. It is very well thought out. OTOH zenital brightness measurement is dependent on all sorts of extraneous factors, and the overall quality of the sky may be poor even though it is very dark near the zenith. In Bortle 3 I can easily see the spiral structure of M51 with direct vision, like looking at a book, with my 10".

I can see the pleadies from bortle 9, but it is tough. They look great in binoculars though. And don't forget that when the milky way is straight overhead, it can fool the sqm into giving a slightly worse reading. And sqms vary a bit unit to unit, so some will use 2 or 3 of them and average the results. When the milky way is at zenith, you can angle the sqm a bit to avoid it

Thank you

Thank You. I can't wait to get to a true Dark Sky location so my little 400mm focal length telescope can shine

So easy to lose your night vision in bottle 8 with all the street and security lights.gonna try the hoodie!

I can usually see to mag 6 or a little better in bortle 4 but I also have really good eyesight and am still young at 23. I have noticed my ability to see faint stars get slightly worse compared to when I was 18-20.

I'm going to say something I'm sure you've never heard! :) I actually don't LIKE pitch black skies. It is almost overwhelming. It is always easier to observe when there is SOME skylight to deine the field stop in a medium power eyepiece. The best skies are ones where a high-power eyepiece - 0.5mm exit pupil, produces a black background, but a 1mm exit pupil allows the field stop to be clearly seen. Very little is lost - dim nebulae like the Horesehead and such. I have seen it so dark that every movement you risk tripping over your gear, and have to use the power LED to navigate - and it looks like a red lighthouse! I did not find this enjoyable at all once I got over the inital WOW factor. Reading maps, the handset etc blinds you for some time. I always have preferred Bortle 3 skies - more stars than appear in say Sky Atlas 2000, so many that constellations become hard to recognize from too MANY stars, but enough light to navigate in the dark.

Are you sure it's not SMOKE Quality Measurement, Tsula? 😅 Thanks as always for a great and informative video! I'm glad you revisited your advice about judging sky quality using the Little Dipper. I use it all the time since you covered that last year (I think). Do you know if Astronomical Certificate Programs will accept a SQM using an iPhone app, e.g., Dark Sky Meter? Hope things are going well!

What about using a normal external light meter used in photography ?