Aperture to see DSOs as more than smudges

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Re: Aperture to see DSOs as more than smudges

#41

Post by AstroBee »


There's a big difference between visual and photographic when it comes to astronomy. The human eye is simply not sensitive enough to pick up extremely faint detail and/color.
I tell people if they want to compare the visual experience to the photographic experience think of the human eye and the lens, the brain as the film/sensor, and your dark adaptation as the ISO/gain or shutter speed.
Your eye is continuously letting in light but the brain acts as a shutter in that it refreshes the image constantly, erasing the old data with the new. More aperture will indeed focus more light on the retina but you still have that constant refresh problem to deal with. Dark adaptation is sort of like gain where an un-adapted eye is like ISO 64 film and a very good dark adaptation is like ISO 400.
You can throw a lot of money at the problem, but you need to have proper expectations before doing that.
I would suggest looking at some of the sketches that some of the folks here do to get an idea of what they visualize at the eyepiece and then look at the details of what size scopes they are using. You cannot compare photos to drawings because someone with an 80mm refractor can take a photo of the Orion nebula with much greater detail than someone with a 16" Dobsonian in a drawing.
Greg M.~ "Ad Astra per Aspera"
Scopes: Celestron EdgeHD14", Explore Scientific ED152CF & ED127 APO's, StellarVue SV70T, Classic Orange-Tube C-8, Lunt 80mm Ha double-stack solar scope.
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Re: Aperture to see DSOs as more than smudges

#42

Post by SkyHiker »


Vern wrote: Sat Jul 10, 2021 12:00 am I have a Celestron 9x50 r.a.c.i. finderscope on my meade starnavigator 125mak with an actual 127mm diameter. I started out with just the red dot and that wasn't close sometimes so I bought a meade series 6000 50mm guide scope. While that worked I couldn't bend my neck to see objects straight up. I then got the Celestron and used a dremel tool to slot the holes on the mount to fit my telescope. That worked and I could see through it in any direction, but it was close to the eyepiece on the telescope. Since both were 50mm I was lucky that the Celestron fit in the mount for the meade guide scope, that got it farther from the telescope eyepiece.

I understand that I have a narrow FOV and I use the finderscope to see extended DSOs. I browse different websites a couple of times a week and there isn't much of anything in stock with an aperture of 8" to 12".

I will post a picture of my telescope if I can figure it out
If you want a Dob that you can transport by car consider a Skywatcher collapsible. They come in 8, 10 and 12 inch sizes, are easy to assemble, and available from several websites. If the package has to be smaller look for a truss Dob.
... Henk. :D Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Vern
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Re: Aperture to see DSOs as more than smudges

#43

Post by Vern »


@AstroBee I know our eyes aren't as sensitive as a camera, what I want to know is if I look through a telescope with a bigger aperture will it be brighter than a smaller telescope? Or will if appear bigger with more detail in the eyepiece, but the same brightness?

@SkyHiker Sorry a DOB isn't for me.
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Re: Aperture to see DSOs as more than smudges

#44

Post by AstroBee »


Well, the short answer is YES. Slightly brighter so a bit more detail will be visible. I would just recommend finding someone with a bigger scope and looking through it before just buying a bigger scope. Aperture fever is a real thing.
Greg M.~ "Ad Astra per Aspera"
Scopes: Celestron EdgeHD14", Explore Scientific ED152CF & ED127 APO's, StellarVue SV70T, Classic Orange-Tube C-8, Lunt 80mm Ha double-stack solar scope.
Mounts: Astro-Physics Mach One, iOptron CEM70EC Mount, iOptron ZEQ25 Mount.
Cameras: ZWO ASI2600mm Pro, ZWO 2600MC Pro, ZWO ASI1600mm
Filters: 36mm Chroma LRGB & 3nm Ha, OIII, SII, L-Pro, L-eXtreme
Eyepieces: 27mm TeleVue Panoptic, 4mm TeleVue Radian, Explore Scientific 82° 30mm, 6.7mm , Baader 13mm Hyperion, Explore Scientific 70° 10mm, 15mm, 20mm, Meade 8.8mm UWA
Software: N.I.N.A., SharpCapPro, PixInsight, PhotoShop CC, Phd2, Stellarium
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Re: Aperture to see DSOs as more than smudges

#45

Post by gregl »


AstroBee wrote: Sat Jul 10, 2021 11:58 pm Well, the short answer is YES. Slightly brighter so a bit more detail will be visible. I would just recommend finding someone with a bigger scope and looking through it before just buying a bigger scope. Aperture fever is a real thing.

And if you have to transport the thing, it's vital to see it in person. The catalog photos don't show you how it will fit into your vehicle.
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Re: Aperture to see DSOs as more than smudges

#46

Post by notFritzArgelander »


Vern wrote: Sat Jul 10, 2021 7:26 pm Wouldn't a focal reducer give me a smaller image in my eyepiece? Would it also be dimmer?
Smaller, yes, with a wider field of view. Dimmer? Not noticeably.
.... When I said DSOs I mean globular clusters and galaxies, not open clusters.
You can see the Sombrero and Pinwheel galaxies in your scope as is. I even saw M74 (aka the great Piscean Bugaboo) which has low surface brightness in my VMC110L. You will not resolve individual stars in globular clusters regularly with less than 6" aperture and then you will still need nights of at least average seeing.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: Aperture to see DSOs as more than smudges

#47

Post by Vern »


I have a chevy equinox and silverado, I can probably fit a bigger telescope/mount/tripod in either than I would want to set up by myself.
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Re: Aperture to see DSOs as more than smudges

#48

Post by Vern »


I saw an 8" lx90 on facebook marketplace that was close to me. I watched the post for a while (too long as it turns out) and was going to make an offer Monday but my water heater started leaking. By the time I replaced the water heater and checked facebook in the afternoon the post was gone. With new ones out of stock and used ones too far away or without a tripod it seemed like I would have to keep checking used or wait until next year for new.

I saw a post on cloudy nights that the evscope was in stock at some vendors and I bought an equinox. I got it this afternoon and am charging the battery now. The sky here is over cast and cloudy so I may have to wait to check the collimation and focus with the bahtinov mask.
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Re: Aperture to see DSOs as more than smudges

#49

Post by OleCuss »


Vern wrote: Thu Aug 05, 2021 9:35 pm I saw an 8" lx90 on facebook marketplace that was close to me. I watched the post for a while (too long as it turns out) and was going to make an offer Monday but my water heater started leaking. By the time I replaced the water heater and checked facebook in the afternoon the post was gone. With new ones out of stock and used ones too far away or without a tripod it seemed like I would have to keep checking used or wait until next year for new.

I saw a post on cloudy nights that the evscope was in stock at some vendors and I bought an equinox. I got it this afternoon and am charging the battery now. The sky here is over cast and cloudy so I may have to wait to check the collimation and focus with the bahtinov mask.
I'm hoping you have a great time with that eVscope1
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Re: Aperture to see DSOs as more than smudges

#50

Post by mikemarotta »


Vern wrote: Wed Jun 16, 2021 10:48 pm... I bought it last year and can see star clusters and the Andromeda galaxy. I have not been able to see other galaxies. At what aperture would I start to see individual stars in star clusters and ... I am near Fenton Michigan and lightpollutionmap.info shows my location as Bortle 5.
Well, what was the outcome. It has been about six weeks. Have you been out since? You live in an area that I know approximately, having lived in Lansing and then Howell and then Ann Arbor for 15+5+5=25 years. Two things about Bortle numbers. One is that your telescope can cut through some of it because it gathers light. On the other hand, what matters most is what from the Eastern Michigan Univesity geography department I learned is "ground truth": the reality of what you perceive on-site, not what a map predicts for you. In other words: knowing the Bortle scale, what is your estimate your skies?

Other than that, I am fascinated by the discussion of backlash and spur gears.

Best Regards,
Mike M.
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Re: Aperture to see DSOs as more than smudges

#51

Post by Vern »


@mikemarotta While the chart shows a bortle 5 in my area Flint is to the north of me and Fenton to the south, so there is more light there. Holly and Grand Blanc are to the east but farther away, it is better to the west but the sun has to have set for a while.

I have been out a few times and nothing has changed in what I can see. I would have been out more but there was lots of rain/clouds, then mosquitoes.

@OleCuss I was only able to get a picture of arcturus yesterday because of the clouds. I like the app it is easy to use, although I had to look some things up online. The forecast here is for another week of clouds, so I will have to check the forecast every day.

I found a couple of interesting things because of the lx90 on facebook marketplace. The lx90 wasn't a gps model and was missing the hand controller. I figured I could use the audiostar from my star navigator and I found an after market gps, the stargps nx. The guide scope adapter for the lx90 isn't available but I found that PHD can send a signal from your computer to the hand controller. Since the lx90's and star navigator use the same hand controller maybe I could use the gps & PHD on the telescope I have rather than buying an older bigger one.

After using the eVscope for a while if I want a higher resolution camera I could try sharp cap, a 5 or 6 mega pixel uncooled camera and either the gps or PHD on my star nagivator. That would be the least expensive way to see if I would want more control of the process and if it gave me a better experience/pictures.
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Re: Aperture to see DSOs as more than smudges

#52

Post by Vern »


Wow doesn't even do justice to what I can see with the eVscope!!!
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Re: Aperture to see DSOs as more than smudges

#53

Post by Vern »


I created a gallery with some pictures I took with my eVscope. The gallery title is my user name.
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