M57 central star

[jetstream]

Another night of VGtrans and nice darkness around 21.7mag, scope-15" f4.8 dob. I figured I better start trying to view faint stars better and tonight gave a VG chance with the M57 area chosen for simplicity. Really I was just trying out different eyepieces, mags etc to see what works on this faint stuff, which was a real eye opener. So far when I up the mag too far I lose stars... but the 7mm KK ortho had the 13 mag star near M57 easy and also the 14.7 mag stars held in direct vision.

Once I started to roll my eye around a bit in averted vision I had a few more stars (4 or so) very near M57 popping in and out of view and I'll be danged if the central star popped out too - a first!

Ok now to confirm as this mag -261x/15" dob-... I threw all I had at it the 5KK ortho, Docter 12.5mm/VIP,more orthos with and without barlows, a 6.7mm ES 82 etc etc nothing, no central star.

Back in with the 7mm KK ortho, in comes the the central star in and out of view, I did hold it for a couple of seconds a few times. Well now I have quite a situation...out of all these eyepieces I have one of them can do this... and I'm shocked the 5mm KK killed the view.

So it was a great inadvertent catch!

Is there a lower limit for exit pupil for people (it must vary) when trying to observe faint stars? I think I'm around 15.7mag so far in averted vision, any thoughts would be appreciated.

edit: I meant M57's central star can we please fix this.

[Littleguy80]

Excellent report, Gerry. M57 is so small in my scope, it's hard to imagine seeing the central star. Interesting that higher magnifications were causing you to lose stars. I'd always understood that stars were one of the objects that wouldn't be lost with high magnifications 

[Stu]

Title fixed Gerry, I was intrigued by the M75 comment  

Really interesting findings, and great job seeing the central star!

Reading Bartel's comments, he states that limiting magnitude does not improve beyond 1.5 to 2mm exit pupil because the sky background is already dim enough not to be a factor any more.

Your 7mm gives almost bang on 1.5mm, so it seems anything beyond that is probably not helping (perhaps by over magnifying the airy disk and making it too faint???? That really is a shot in the dark though!) It is a known factor though that seeing say the E & F stars in the Trapezium is a matter of using the right mag, not necessarily the highest mag. I've seen this effect with Saturn's moons too. Too high and they disappear, I assume they approximate to a point source so behave the same way as a star?

All good stuff, keep the reports coming. These eyepieces had good reputations for a reason I guess?

[John]

Great report Gerry

I've glimpsed this star with my 12" but not in a sustained way. Maybe I'll need to drop back in magnification for a clearer view ?

As Stu says E&F Trapezium seem to need the "goldilocks" magnification to make them "pop". For me the 8mm Ethos or the 7mm XW are the ones for these stars.

I think the key thing is to have a range of high power options - that way you can play around to find the session / target "sweet spot".

I found the Baader GO 6mm the best for spotting Sirius B. Just the right tool for that task with my 12" dob, my observing eye and from my back yard. Change one of those variables and maybe the eyepiece would need to change ?

On the smallest effective exit pupil, I think this will vary person to person. Perhaps if there were a few of you observing M57 on that occasion with that scope the "right" eyepiece might have varied depending on the observer ?

[alanjgreen]

Jetstream,

What magnification does the 7mm KK ortho give in your scope? (i.e. what was the successful magnification to see the central star?)

Alan

[faulksy]

don't believe you gerry

so you and mr alan potts have seen it and i havn't . damm you gerry

[John]

Just another comment I'd like to add.

I have found that the first time you manage to get a tricky target like this, getting the eyepiece right seems to be very important.

Re-visit the target a number of times and often I find that I can repeat the observation with a wider range of magnifications simply because I now know what to look out for and any observing techniques that help. Usually the original formula remains the most effective but others can also get a result.

 

[mikeDnight]

That's a great observing report Gerry.

It may be that the 5mm ortho was just a bit too much for the seeing conditions on that particular night, and that the 7mm was the perfect match. The upper atmosphere can play havoc with stars at high power, but its great to see orthoscopics being used for something other than lunar and planetary. 

[Piero]

Very interesting Gerry!  15.7 mag... wow!  

Now,.. going against common logic, could you try the HR 2.4mm on those faint stars, when you have a chance? 

[Stu]

3 hours ago, alanjgreen said:

Jetstream,

What magnification does the 7mm KK ortho give in your scope? (i.e. what was the successful magnification to see the central star?)

Alan

I think Gerry mentioned this, x261 with an approx 1.5mm exit pupil.

[jetstream]

6 hours ago, Littleguy80 said:

I'd always understood that stars were one of the objects that wouldn't be lost with high magnifications 

Me too.

After using my zoom I figured this wasn't the case though and I've found it best to keep ones mind open when trying things (after many trying nights lol!).

[jetstream]

6 hours ago, Stu said:

Reading Bartel's comments, he states that limiting magnitude does not improve beyond 1.5 to 2mm exit pupil because the sky background is already dim enough not to be a factor any more.

Thanks for the info Stu, I hadn't read that from Mel- I'm usually so focused on dim nebula. That man is such a wealth of knowledge! I must keep close track of things as I enter this star viewing expedition, oddly enough I rarely observe stars seriously!

I'm going to read Bartels info on this.

[John]

7 minutes ago, jetstream said:

.... I've found it best to keep ones mind open when trying things .....

Very good advice for all there I think !

 

[jetstream]

5 hours ago, John said:

I think the key thing is to have a range of high power options - that way you can play around to find the session / target "sweet spot".

Thanks so much for all the help and info John, I think I'll need all the experience and help I can get for the upcoming targets. I wonder if there is a few things at play here? My 5mm KK is not known to be a "VG sample" but avg whereas the 7mm KK is excellent in comparison to anything I've tried. I don't know if this is an issue...I suspect it is.

However mikeDnight , a very experienced observer makes a great point about seeing...I must revist this target many times and keep exploring eyepiece options and gain experience.

[John]

14 minutes ago, jetstream said:

Thanks so much for all the help and info John, I think I'll need all the experience and help I can get for the upcoming targets. I wonder if there is a few things at play here? My 5mm KK is not known to be a "VG sample" but avg whereas the 7mm KK is excellent in comparison to anything I've tried. I don't know if this is an issue...I suspect it is.

However mikeDnight , a very experienced observer makes a great point about seeing...I must revist this target many times and keep exploring eyepiece options and gain experience.

I think there are a whole lot of factors at play when we are trying to view stuff that is towards the edge of the capabilites of scope / conditions / observer. Small and subtle differences in seeing conditions, optics and even the observer (eg: tiredness) that are not noticed when viewing more mainstream targets come into play and the margin between success and a near miss is sometimes wafer thin IMHO. 

 

[estwing]

well done Gerry....we've had a go in my 18"...Steve's 20"....Damian's 22"...still a no show. Wish our skies were up to the conditions you enjoy...

[PeterW]

..."upcoming target"... what are you planning on going after now?

 

peter

[jetstream]

2 hours ago, PeterW said:

..."upcoming target"... what are you planning on going after now?

 

peter

For a couple of years now I have wanted to see evidence of gravitational lensing with my own eye(s). I'm a long way off as my manual dob finding abilities need work at such small FOV's and I need experience in viewing faint point sources. There are 2 candidates, the UMA lensed quasar and Einsteins Cross.

I'll need luck.

[jetstream]

5 hours ago, estwing said:

well done Gerry....we've had a go in my 18"...Steve's 20"....Damian's 22"...still a no show. Wish our skies were up to the conditions you enjoy...

Keep at it Calvin, you guys will pull it out. I have read so much about using very high mag for stars that I think I missed the boat for a while- find what works for you- try everything you own IMHO. I had about 20 eyepieces out.....one worked.

[John]

On 19/07/2017 at 22:31, jetstream said:

Keep at it Calvin, you guys will pull it out. I have read so much about using very high mag for stars that I think I missed the boat for a while- find what works for you- try everything you own IMHO. I had about 20 eyepieces out.....one worked.

Thats my problem then - I only have 17 eyepieces .......

 

[jetstream]

31 minutes ago, John said:

Thats my problem then - I only have 17 eyepieces .......

 

I really hope that this phenomema was just due to my inexperience and that more eyepieces work as I gain experience....I'm hoping to be able to get up to 16 mag, if not I won't stand a snowballs chance in he'll in my lensed quest

[alan potts]

On 19.07.2017 г. at 11:44, faulksy said:

don't believe you gerry

so you and mr alan potts have seen it and i havn't . damm you gerry

I am sure it is more down to location than anything, don't forget where I live there are not large towns for miles and no industry to talk of. I have done it 4 times now in all but spent longer trying to see the HH if you recall. BTW very well done Gerry. with me it was 10mm amd 8mm on the LX 12 inch giving X304 and X358, on the 18 inch just over x220 was enough, clearer with the 18 inch, as you would sort of expect.

[PeterW]

Easier than the Horsey.... should be no problem then?!

Peter

[jetstream]

1 hour ago, alan potts said:

BTW very well done Gerry. with me it was 10mm amd 8mm on the LX 12 inch giving X304 and X358, on the 18 inch just over x220 was enough, clearer with the 18 inch, as you would sort of expect.

Thanks Alan, I'm glad you see it at lowers mags too... I was almost scared to report the mag as it doesn't seem like a typical one to see it lol!

[John]

Having another go at this tonight.

12" dob under a good sky (for here) and with M57 practically overhead.

No luck with the central star but I've managed to see and hold with direct vision stars marked below (red arrows) down to mag 14.7 which is the best I've done I think. Another .5 mag to go and bingo !

Eyepieces used range from Leica ASPH zoom at 8.9mm (179x) to Pentax XW 3.5mm (454x). For me, the faintest stars were easier at the higher magnifications. Incidentally the Nagler 2-4mm zoom also did well on these faint ones.

So "close but no cigar" but I've pushed my deep limit a bit further, which is pleasing

Perhaps a dark head covering to shroud my head / eye  and the eyepiece from any stray light will reach that little bit deeper ?