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defining 24" capability


jetstream

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Conditions last night were superb with only my best winter observing beating it. The MW was sharply defined with bright billowing clouds reaching to the horizon to the south with the split so obvious. The Cygnus area showed its huge dark lanes with great definition. It took until about 1am for these conditions to maximize.

I'm curious as to the DSO performance with the 24" so I went for a few galaxies again.

I never realized how many galaxies are in Hercules... I tried a nice group starting with NGC 6146, no issues here, actually I bagged all of the group including the tough NGC 6147 in averted. So, NGC 6141, NGC6145,NGC 6146, NGC 6147, and NGC 6138.  There are galaxies all over the place here!

What a great beginning!

Next was a couple of galaxies in Draco- IC1258 and IC 1260- I thought these would be toughish but the were bright in direct vision. Strange how some of the galaxies seem easier than others regardless of listed magnitudes and size.

Another Draco success included NGC 6338, NGC 6345, NGC6346 and IC1252. I thought IC1252 would give me grief at 15.7 mag but the .8 armin size helped I think.  The 10mm BCO really helps on the fainter galaxies.

When I ordered this telescope my goal was to easily see galaxy clusters, not being limited to the brighter ones the 15" allowed (it went deep though!) and the 24" is living up to expectations- actually beyond them. If it can get the Einsteins Cross or the Andromeda Parachute I'll be ecstatic!

A few more things: M16/Docter 12.5 UWA /Lumicon UHC- extremely bright with a very dark knot in the wings- what a sight!

M17, the Swan: the Docter gave the best high power views yet, extremely high detail in the neck, under neck body area- so many lanes with bright mottling!

M57: central star came into view with the 10mm BCO first try- no issues at all.

To recap: an ortho is needed for very faint galaxies in a scope, the 12.5mm Docter is outperforming the Nikon 14mm HW for transmission and bright nebula appearance and the Sky Commander might not be my dark adaptation issue. My little red flashlight is to bright. After sketching out some galaxy positions using it my eyes were blown! The galaxies disappeared for a good long bit after using it. More investigation needed.

Question: what do members use for a red light to sketch etc at night? 

A great night!!:thumbsup::biggrin:

 

 

Edited by jetstream
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Great report again Gerry - I'm green with envy at that scope under your skies :Envy:

Interesting observations on eyepiece performance as well. I've long been convinced that you need to be pushing the performance envelope on challenging objects to get to a point where the performance differences between good quality eyepieces start to show.

Alvin Huey in the US was the first person who reported how good the 10mm Baader Classic Ortho was at teasing out faint galaxies - he rated it as second only to the Zeiss ZAO 10mm and a touch better than the 10mm Delos (which he also rates highly). Personally I really like the 18mm Baader Classic Ortho as a deep sky eyepiece as well. It's great that these eyepieces are available for a touch under £50 a throw or even less on the pre-owned market :smiley:

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17 minutes ago, John said:

Great report again Gerry - I'm green with envy at that scope under your skies :Envy:

Interesting observations on eyepiece performance as well. I've long been convinced that you need to be pushing the performance envelope on challenging objects to get to a point where the performance differences between good quality eyepieces start to show.

Alvin Huey in the US was the first person who reported how good the 10mm Baader Classic Ortho was at teasing out faint galaxies - he rated it as second only to the Zeiss ZAO 10mm and a touch better than the 10mm Delos (which he also rates highly). Personally I really like the 18mm Baader Classic Ortho as a deep sky eyepiece as well. It's great that these eyepieces are available for a touch under £50 a throw or even less on the pre-owned market :smiley:

Thanks John, it was your excellent review that led me to the BCO series- the 18mm and 10mm are super DSO eyepieces- your reviews are very very helpful for us! I think now that I have an idea how this scope performs I;m going to settle into some Arps etc and have some fun.

it is unbelievable that this 10mm BCO will outperform some pretty expensive glass!

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14 minutes ago, Stu said:

Sounds like Mag 16 is within reach under the right conditions Gerry?

I think so Stu, but the size and predominant flux(s) could make a difference. I'll need everything in control of the dark adaptation too- I need to work on this, including getting a monks hood. Not having that much experience I find that having a brighter galaxy in a group of near fainter ones helps too so I can stare right at the spot for averted.

NGC6147 can be rated over 16 mag I think but the numbers are all over the place..no idea what all these mags mean really. Steve Gottleib rates it at V 15, Stellarium 16.3...

from Steves site:

"

NGC 6147 = MCG +07-34-023 = Holm 747b = PGC 58077

16 25 05.8 +40 55 44

V = 15.1;  Size 0.4'x0.4';  Surf Br = 13.0

 

18" (7/29/08): very faint, very small, round, 20" diameter.  Located 2.3' NNW of NGC 6146 and 1.4' SSE of NGC 6145 within AGC 2197.  The three galaxies are collinear.

 

17.5" (7/24/95): extremely faint and small, 15" diameter, round.  Only able to glimpse repeatedly <25% of time with averted vision.  Faintest of trio and situated 1.4' SE of NGC 6145 and 2' NW of NGC 6146 in AGC 2197.  Incorrect identification in the RNGC.

 

George Johnstone Stoney, LdR's assistant, discovered NGC 6147 on 26 May 1849.  He noted "2 new neb, alpha (on diagram) eF st, Beta small."  The diagram clearly shows NGC 6147 = PGC 58077 (labeled as Alpha) on a line between NGC 6146 (not labeled) and NGC 6145 (labeled Beta), with NGC 6147 slightly closer to NGC 6145.   The direction of drift is not shown but is presumably down in the diagram. Dreyer later added the parenthetical comment "Query h1957 [NGC 6145] and h1958 [NGC 6146] and one Nova."  One faint star (labeled alpha) is shown on the diagram and it appears to correspond with MCG +07-34-022 = PGC 58078.  Since Stoney didn't record it as nebulous, it didn't receive a NGC designation."

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If anyone is interested:more from Gottleib

" Specifically, the Lupton formula:
V = g - 0.5784*(g - r) - 0.0038; standard deviation = 0.0054

or equivalently, V = .4216*g + .5784*r - .0038 (round as you wish and the last term can probably be dropped)

For example with NGC 1, the SDSS gives:
g = 13.55
r = 12.70

Plugging into the formula results in V ≈ 13.05.
For comparison, RC3 lists V_T = 12.89.

Even if you just average the SDSS g and r, you'll be in the same ballpark. "

 

It appears that formulas are used to calculate V mag from color (flux?) data I think? Doesn't really matter to me, I'll just point the scope and wish for the best lol!

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Just now, Stu said:

Sorry to be thick Gerry, what are g and r standing for?

I think red and green- the galaxies have different measurable light or something, possibly also called fluxes?(not sure). Averaging them might give a useable number, not sure. Lots I'm not sure about lol!

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Fantastic stuff Gerry wish we had your skies over here.

Galaxies really jump out with the larger apertures. I would be interested to see what the optics perform like on targets like hickson 55 and 57.

M57 central star straight away must be nice as I've only glimpsed it once and it was a maybe at that. Struggled quite a lot the last two seasons with getting the weather and transparency.

I don't sketch but use a home made dimmable 12v led strip light fashioned like a bankers light  to read my star charts. I don't have a pic of it to hand but it works really well going down to nothing. 

Spent quite a few hours chasing the galaxies in Hercules and it has a great mix of targets in there for shape and magnitude variations.

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34 minutes ago, mapstar said:

Fantastic stuff Gerry wish we had your skies over here.

Galaxies really jump out with the larger apertures. I would be interested to see what the optics perform like on targets like hickson 55 and 57.

M57 central star straight away must be nice as I've only glimpsed it once and it was a maybe at that. Struggled quite a lot the last two seasons with getting the weather and transparency.

I don't sketch but use a home made dimmable 12v led strip light fashioned like a bankers light  to read my star charts. I don't have a pic of it to hand but it works really well going down to nothing. 

Spent quite a few hours chasing the galaxies in Hercules and it has a great mix of targets in there for shape and magnitude variations.

Thanks Damian, observing these objects is a process to get good at, for me anyway. This scope is really helping me out and I hope to try those Hicksons when in view, I'll look up 57 too. From Cals info it looks like some good mag is needed to separate 55. I've noticed with stars that there is a sweet spot to observe them for mag when in theory we should be able to go as high as we want but for me too much mag and they disappear... M57 central star is such an object for me, too little nothing and too much nothing. It might be possible that faint galaxy cores begin to look like point sources and act like them, so I'll keep this in mind on Hickson 55- I know Huey will use a pile of mag on some galaxies with orthos.

For me the way to get M57 star is orthos, and they have to be good themselves and it seems as if 250-270x is a good place to start in scopes like ours. All you guys have great dobs and I like the style of yours in particular Damian, what a great job you did!

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On 29/06/2019 at 18:42, jetstream said:

Doesn't really matter to me, I'll just point the scope and wish for the best lol!

I think there’s a lot of merit to that approach, Gerry, especially with your skies. I use published Deep Sky magnitudes solely as a rough guide to “might be possible” vs “definitely impossible”. If it falls into the former camp, I give it a shot.

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1 hour ago, FenlandPaul said:

I think there’s a lot of merit to that approach, Gerry, especially with your skies. I use published Deep Sky magnitudes solely as a rough guide to “might be possible” vs “definitely impossible”. If it falls into the former camp, I give it a shot.

I spend more time trying to figure out what I saw than I do observing them, the other night was no exception- frustrating really. This is where the "doesn't matter to me" comes from lol!

The galaxy magnitudes are very puzzling to me...

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Aw man the recent spate of new dobs on SGL here isn't good for the ol' ap fever...

Great stuff - sounds magnificent! keep the reports coming ;)

I was thrilled to see the Antennae pair several weeks back - would love to see what detail could be discerned in a 24".  Can't wait for a camping trip to the nice dark skies of the Skellig Star Party in August here ;)

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