24 inch dobsonian under Bortle 1. Saw the pillars of creation with my own eyes.
Posted Aug 14, 2023, 2:29 PM UTC
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Sounds like a dream! Nice capture as well.
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Wonderful photo! I happy if I can see M16, let alone insane details! Filter or no filter and what magnification? I'm guessing OIII and insane mag with excellent seeing.
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For M16, I found the UHC filter to be the most useful, along with mid-range magnifications (which come out to be in the neighbourhood of 150-200x in this telescope).
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Thanks! Have you seen the central star in M57? If I had excellent conditions, first thing I'd look for. Next would be Polarissma Borealis!
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Surprisingly I didn't see the central star in M57. It only rises 30 degrees above horizon from Namibia, also the transparency might have been slightly below average when I tried.
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It probably needs to be higher. But you have more interesting things to see in the South! :)
You can't get Borealis, but you could go for Polarissima Australis! https://www.cloudynights.com/topic/292043-polarissima-borealis-and-australis/
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I have seen it a few times in my 16; occasional outstanding seeing around here.
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Nice! Mind sharing your observing report?
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I don't really have any, sorry. But here are some of the most memorable sights:
- M17 with an OIII filter is extremely detailed, with thin gas filaments scattered everywhere across the field of view.
- Omega Centauri is so large, it barely fits the field of view at the lowest magnification.
- the Homunculus Nebula around Eta Carinae has a vivid yellow color.
- NGC 7009 (Saturn Nebula) looks exactly like on photographs.
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Sounds like an amazing experience! Thanks for sharing.
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You can actually see colors with your eyes, just through the telescope??
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Bright nebulae look greenish because we can see OIII and H-beta emissions fairly easily. Very few objects have other colors, like the yellowish Homunculus Nebula mentioned earlier. I haven't seen any red color from H-alpha, human eyes are almost blind to this wavelength in the dark. There are people who claim you can see some pinkish hues in the Orion Nebula, but it's not an easy object for July/August and I haven't even tried observing it.
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There are many bright planetary nebula that show color with modest scopes from moderately dark skies.
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In April 1986 in Botswana I saw with binoculars two Omega Centauri super clusters next to each other. But one was Halley's Comet.
Minutes later, there was a strange cloud on the eastern horizon. Long and thin, and strangely bright (no electric lights within 50 miles of this safari camp), it had a dark center. Then I realized the cloud was backed by the Milky Way, perfectly outlined.
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I have always wondered, doesn't the increased focal length of very big telescopes magnify the image more basically canceling the higher luminosity given by the bigger aperture of the f ratio is the same?
I have a 10 inch f/5 dob, If I had a 20 inch f/5 dob the view, with the same eyepiece, would be twice as magnified, but of the same surface brightness.
Obviously this applies to extended objects only, not point sources like stars.
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The surface brightness doesn't change, but larger overall size allows us to see more detail. Similarly most galaxies have similar surface brightness, but the nearest ones (largest, in terms of apparent size) are the easiest to see.
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Just to clarify I meant the surface brightness in the eyepiece view, not the surface brightness inherent of the object.
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For geometrical reasons the surface brightness of any object with a real surface (non-stellar) cannot get higher by any optical means. It sounds stunning, but it's true. It's actually all about the possible higher magnification at the same surface brightness. The larger areas of details under higher magnification just help the eye to see low contrast differences better. There's even a formula for how large an area has to be at a certaing difference in contrast.
Take a white paper, print a lowest possible contrast grey blob on it, and then look at it from different distances. Then you'll see the effect.
It's btw not all about the maximal achievable surface brightness! The exit pupil of 2mm, which is widely considered as the optimal exit pupil for weak nebulous DSOs, gives at least under average Central European conditions significantly better views (e.g. of Stefan's Quintett in my 18") than the objectively higher surface brightness in a 3mm exit pupil. It's something strange, that has seemingly to do with the background darkening at smaller exit pupils.
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It's something strange, that has seemingly to do with the background darkening at smaller exit pupils.
There's two effects at play:
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Is that generally the eye loves magnification more than brightness to a certain degree. Keeping the exit pupil around 2mm tends to balance size with brightness in a way that is favorable to the human visual system, with the emphasis being on size.
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There is indeed a kind of "apparent or perceived contrast" effect that happens at certain exit pupils, light pollution levels, and certain targets. Even though strictly speaking the contrast does not change from one exit pupil to the next for all extended targets, the brain really does think it does at certain points. Some observations of this phenomenon: Using a zoom against M31 can really make the dust lanes "pop" at a specific exit pupil. Also, when I compared the view of M27 in an 8" SCT and 12" reflector, both at 127x, the view in the 8" (1.6mm exit pupil) actually looked better / more contrasty even though it was the same size, but dimmer. The 12" looked washed out at 127x (2.4mm exit pupil). Very strange, but definitely a real effect nonetheless.
Of course, point #2 is going to vary from one location's light pollution levels to the next, as well as for different targets.
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It is true that longer focal lengths will, in turn, result in higher magnifications. However, I believe surface brightness is determined by the exit pupil, at least for visual use.
If the exit pupil is constant, then an increase in aperture will only increase the size of the image. This is because while a bigger mirror captures more light overall, it has to spread that light out on a much larger surface area.
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Focal ratio only plays a role for focal astrophotography. Visually it's all about the exit pupil.
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Yes, though as I understand it, a scope's focal ratio influences the resulting exit pupil.
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It's rather a combination of focal ratio and eyepiece focal length. Given identical apertures, an f/4 telescope with a 16 mm eyepiece will produce the same image as an f/10 telescope with a 40 mm eyepiece.
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That's right. You can calculate exit pupil from focal ratio and eyepiece's focal length.
To me the calculation
EP = aperture / magnification
appears more descriptive. The result is the same either way of calculation.
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But the image at higher magnifications is as bright as a smaller scope at lower magnifications.
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how much time of searching the objective? bortle 1 is my dream and I always follow them:D
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But it's not even viewing through the scope, it's literally a picture of the scope and sky...
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This is an untracked dobsonian, you can't take pictures through it.
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You can just not long exposure
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And long exposure is exactly what you need for deep sky imaging. At 2400 focal length you can expose for just a fraction of a second without blurring out the stars. It's not worth the effort. I travel with 2-3 setups for actual astrophotography, the dobsonian is only for visual.
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That’s awesome. I was chasing a lot of those hard to find objects in my 10in in bortle 2/3 skies a few times a year but I couldn’t get their often enough. I got night vision this year in wanting to see more and can see the pillars and the elephant’s trunk with my 10in from my bortle 5/6 backyard. Although they are kind of faint, but still amazing to see it live!
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Really amazing. Yesterday i went to my parents ranch with my 8" dobby, the bortle was around 3. I cant imagine how beautiful was to be in a bortle 1
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That telescope looks like a lighthouse!
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Not going to see those or get pix of them with any of my scopes under my Bortle 55 sky (cloud deck every night except on some full moons).
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Is this raw image or edited, if this is raw then wow
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where is this place and what kind of eyepiece was used?
England
Nah only kidding, we haven't seen a star in England in over 40 years.
NOT EVEN THE SUN! Perpetual clouds.
I heard summer showed up on a Wednesday. Last year.
Lol almost as bad as Hinernmia!!!
And Scotland what is the sun?
Kiripotib Astro Farm in Namibia. Telescope: https://www.astro-namibia.com/htm_e/e_astro_dobson_24.html
It comes with Ethos eyepieces. I found the 13 mm to be the most useful for most objects.
How was the experience? Would you recommend that place? How much did it cost?
I also want to go to Namibia to look at stars.
Around 100 EUR per day. Flights are usually around 800-1000 EUR for a round trip, but the price fluctuates a lot. I don't remember how much the dobsonian rental cost, but it was also around 100 EUR per night. I suggest finding some people to travel in a group to split up costs. I travel to Namibia once per 1-2 years, it's one of the best places in the world for astronomy. Weather is almost certain between May and September. Just be advised that there's not much more to do than astronomy in the middle of a desert, you're pretty much stuck on a farm without a lot of tourist attractions in a 150 kilometer radius.
A few good books and 50 saved movies on an iPad, I’ll be fine.
I LOVED Namibia. Maybe not much to do at this particular camp, but tons to do in that part of the world! I did a 15-day camping tour and it was mind-blowing. Obviously, there's safari, but also some of the oldest and tallest dunes in the world (in a stunning terra cotta color), Damaraland which looks like Utah crossed with the Australian Outback, and dugout canoing among the hippos in nearby Botswana, to name a few highlights. I also found the interaction of Afrikaner and indigenous cultures, and the lives people live in such harsh conditions really interesting. Definitely worth the flight.
Thanks for the detailed report!! One day!
Thanks for sharing about this! I’m already researching it to see if my fiancé and I want to go. Was there any concern with wind? I’ve heard Windhoek is pretty windy.
It does get windy during the day, you need to put away or cover up all your equipment or you'll get desert dust everywehere. At night, there's typically almost no wind, otherwise it means the conditions are not good to begin with. At any rate, the observation platforms are shielded from wind just in case: https://i.imgur.com/pTL1gN6.png
That is good to know. Thank you for answering my question! :)
Clear skies!