82 replies to this topic

[Dave Mitsky]

There's a star hop to M13 at https://www.skyledge...ssier13-hop.htm and a Telrad finder chart at http://www.star-shin...charts/m013.htm

 

When I'm binocular observing and can't see the Keystone directly, I do a sweep from gamma (Sulafat) and beta (Sheliak) Lyrae to rho and pi Herculis, which in turn point towards M13.  M13 lies about 6.5 degrees southwest of pi Herculis.

Here's a screen capture from Stellarium (click to enlarge) set at 10:00 p.m. EDT with the four stars mentioned above highlighted in yellow.

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[Dave Mitsky]

Here's a close-up view.

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[Slip]

Last night I had a palm tree covering my view of M13. Luckily, I was able to switch over to the south and bring up M4. I love those Globular Clusters.

 

Aloha and Clear Skies. 

[edsmx5]

Last night I had a palm tree covering my view of M13. Luckily, I was able to switch over to the south and bring up M4. I love those Globular Clusters.

 

Aloha and Clear Skies. 

Must be tough

[edsmx5]

Must be tough

I kid because . . . well, because I'm jealous !!

[Slip]

I kid because . . . well, because I'm jealous !!

No worries. I thought I had great skies in Wisconsin before I was into astronomy but here it's a whole new level. We certainly are blessed to live here in many ways. I do have to battle some clouds on days but they do move through quickly and are more of a nuisance that anything else. 

 

Those fires sure have put a damper on the skies in the mainland for sure.

[Jon Isaacs]

M13 is relatively easy to find if you can see the Keystone.

 

I'm sure the OP can't see the Keystone with a full moon in Bortle 8. I doubt he can see it in Bortle 8 even without a moon. I recommend waiting until there is no moon. It will look a lot better anyway

 

 

The stars on the Keystone are magnitude 2.8, 3.1, 3.5 and 3.9. In a "True" Bortle 8 they should be visible without the moon and with the moon, three of the 4 should be visible.

 

Binoculars are a help as well.

 

https://en.m.wikiped...ki/Bortle_scale

 

Jon

[WillR]

The stars on the Keystone are magnitude 2.8, 3.1, 3.5 and 3.9. In a "True" Bortle 8 they should be visible without the moon and with the moon, three of the 4 should be visible.

 

Binoculars are a help as well.

 

https://en.m.wikiped...ki/Bortle_scale

 

Jon

Jon I am supposedly Bortle 4, and the Keystone is barely there some nights for me without the moon. I probably have bad eyesight compared to most people, because my limiting magnitude seems to be around 4 with an occasional 4.5. Most nights I can't see all of the Little Dipper.

 

 

 

Perhaps

[Freezout]

I was about to give the advice to use the mental picture of Hercules himself, as the constellation is drawing him in the sky. I have been doing so for years. But with some search I realize the stars do not represent the parts of Hercules anatomy I thought.
For me M13 was on the torso, left upper ribs, of the hero. I discovered now the image is not supposed to be so. I am a little bit traumatized!…
M13 is on the right hip of Hercules…

[Tony Flanders]

The stars on the Keystone are magnitude 2.8, 3.1, 3.5 and 3.9. In a "True" Bortle 8 they should be visible without the moon ...

Yes, they are -- but they sure aren't easy!

 

Limiting magnitude as strictly defined means the faintest star that you can just barely see using averted vision. Experienced observers deploy averted vision instinctively, and develop some degree of confidence about seeing things that are right at the limit of possibility. Same is not true of a newbie -- not even the best and brightest.

I can see stars one to two magnitudes fainter than inexperienced people with identical eyesight. And I know precisely where the Keystone is and what it looks like in every possible orientation. So I can see it quite easily from my local city park, which is Bortle 8 on a night of typical good transparency.

[Jon Isaacs]

Jon I am supposedly Bortle 4, and the Keystone is barely there some nights for me without the moon. I probably have bad eyesight compared to most people, because my limiting magnitude seems to be around 4 with an occasional 4.5. Most nights I can't see all of the Little Dipper.

 

 

 

Perhaps

Will:

 

Did you read the link to the Bortle ratings ?   If you can barely see the Keystone, the skies that night are not Bortle 4. 

 

"True" Bortle ratings do not come from a website, they are evaluated by the observer on the night in question. Somehow the use of the Bortle scale has been hijacked and misused by Lightpollutionmaps and other websites. 

 

So, when I wrote that under "True" Bortle 8 skies one would see the Keystone comes from the criteria John Bortle created.

 

I do not rate my skies using John's system, I measure them with Sky Quality Meters and estimate the transparency and seeing. Last night I measured 21.3-21.4 mpsas with mediocre transparency and seeing.

 

I could see the keystone.

 

Early in the evening, not too long after twilight, I was able to find M13 despite looking through high clouds. , M13 was at about 40° elevation and the sky overhead measured 17.5 mpsas.  I could not see the Keystone but I was able to locate it using 10x42 binoculars due to my familiarity with the region. 

 

I would not expect a first timer to have found it because of the clouds, fortunately they dissipated.

 

Jon

[WillR]

Will:

 

Did you read the link to the Bortle ratings ?   If you can barely see the Keystone, the skies that night are not Bortle 4. 

 

"True" Bortle ratings do not come from a website, they are evaluated by the observer on the night in question. Somehow the use of the Bortle scale has been hijacked and misused by Lightpollutionmaps and other websites. 

 

So, when I wrote that under "True" Bortle 8 skies one would see the Keystone comes from the criteria John Bortle created.

 

I do not rate my skies using John's system, I measure them with Sky Quality Meters and estimate the transparency and seeing. Last night I measured 21.3-21.4 mpsas with mediocre transparency and seeing.

 

I could see the keystone.

 

Early in the evening, not too long after twilight, I was able to find M13 despite looking through high clouds. , M13 was at about 40° elevation and the sky overhead measured 17.5 mpsas.  I could not see the Keystone but I was able to locate it using 10x42 binoculars due to my familiarity with the region. 

 

I would not expect a first timer to have found it because of the clouds, fortunately they dissipated.

 

Jon

I have read it and we both know the Bortle scale is very subjective and we could veer off into a discussion of that. It assumes great eyesight and transparency, which we pretty much never have here. I know my site is more like a 5, but I am using the rating from the various astronomy weather predicting apps and the light pollution map. I don't have a meter, but using the Dark Sky meter app I get readings from 19.75 to 20.5.

 

My point was that someone in a city basically ( Bortle 8 by the OPs definition) is going to need some other way of finding M13 other than the keystone, although now that I see Tony's post, I'll have to amend that to an inexperienced observer.

Edited by WillR, 10 June 2023 - 08:13 AM.

[Takuan]

I will never forget what it took for me to find M13 with my first telescope (Vixen Newton 100/1000) from the city when I was in my early twenties.
Of course, at that time I did not know that I had to protect myself from ambient light, my wide field eyepiece was a 20mm Kelner and I could barely identify the constellation naked eye...
A little patience is essential in the Hobby.

Cheer up and, when you have a little experience and can, escape the city lights. Enjoy.

Edited by Takuan, 10 June 2023 - 08:44 AM.

[Researcher]

Thanks for your replies everyone 

 

Actually  i can see zeta herculis with naked eye but not the entire keystone, still its a good point of reference to start with. Its a good idea to use some binoculars first, i will use some 10 x 42.  This night i hope its clear skies so i can have another go

[Jon Isaacs]

I have read it and we both know the Bortle scale is very subjective and we could veer off into a discussion of that. It assumes great eyesight and transparency, which we pretty much never have here. I know my site is more like a 5, but I am using the rating from the various astronomy weather predicting apps and the light pollution map. I don't have a meter, but using the Dark Sky meter app I get readings from 19.75 to 20.5.

 

My point was that someone in a city basically ( Bortle 8 by the OPs definition) is going to need some other way of finding M13 other than the keystone, although now that I see Tony's post, I'll have to amend that to an inexperienced observer.

 

A Bortle rating does not assume anything about the observer's eye sight. It assumes nothing about the transparency, those are both included in the rating. If John Bortle and I were standing side by side, he would rate the site differently than me because he has, or at least had, exceptional eye sight. And the Bortle rating changes from night to night.

 

This thread and this discussion is an example of the confusion the misuse of the Bortle ratings causes. I wish people would stop misusing it.

 

Jon

[Lizardman]

Get a Goto mount ; problem solved.

[Researcher]

A Bortle rating does not assume anything about the observer's eye sight. It assumes nothing about the transparency, those are both included in the rating. If John Bortle and I were standing side by side, he would rate the site differently than me because he has, or at least had, exceptional eye sight. And the Bortle rating changes from night to night.

 

This thread and this discussion is an example of the confusion the misuse of the Bortle ratings causes. I wish people would stop misusing it.

 

Jon

Yea, Im very aware that bortle scale has nothing to do with eye sight. I remember one day when i was watching at saturn through a 127mm scope and clearly saw titan, and my brother couldnt see it. Also one day i a cousin was pointing at a star that i couldnt see with naked eye.

 

Since i live in a big city i suppose its always bortle 8 (or probably 9), but sometimes even polaris isnt visible because transparency i guess

[Researcher]

Get a Goto mount ; problem solved.

I think goto isnt that exciting (but its up to someone's preferences, circumstances and probably personality). I like the challenge of find objects by myself, its very rewarding when i find them. Also i think you become more familiar with the sky when using manual scopes, you get better skills

[Aaron Zhang]

In my Bortle 7 skies, when I locate an object but have trouble seeing it in my low power eyepiece, I find that increasing the magnification can make a considerable difference. There are many objects that were hard for me to see at low power but that popped into view at medium or high power. In your 8" Dob, an eyepiece in the 6-12mm range might help with a lot of objects. Clear skies!

[Lizardman]

I think goto isnt that exciting (but its up to someone's preferences, circumstances and probably personality). I like the challenge of find objects by myself, its very rewarding when i find them. Also i think you become more familiar
with the sky when using manual scopes, you get better skills

Absolutely. But my observing time is limited and it has to coincide with clear skies. Last time out with my nifty Goto I observed about 15 DSO’s and 10 double stars in a couple of hours . And they didn’t continually drift out of FOV . It was great fun. As I’ve said in past threads l previously left the hobby out of frustration of not finding things and then keeping them from drifting away when I did find them and trying to find them again. Got tired of torturing myself. I love Goto; just me I guess.

Edited by Lizardman, 10 June 2023 - 07:41 PM.

[WillR]

A Bortle rating does not assume anything about the observer's eye sight. It assumes nothing about the transparency, those are both included in the rating. If John Bortle and I were standing side by side, he would rate the site differently than me because he has, or at least had, exceptional eye sight. And the Bortle rating changes from night to night.

 

This thread and this discussion is an example of the confusion the misuse of the Bortle ratings causes. I wish people would stop misusing it.

 

Jon

So the Bortle rating is a rating of the current conditions with no consideration of one's experience or eyesight? Or does it rate different sites in optimum conditions, and therefore tell us something that is true of one site vs. another? In other words, under the same conditions Cherry Springs is darker than my home, which is true. Not sure I catch your drift.

 

If my eyesight is worse than John Bortle's, then I might rate a sky at 6 that he might rate at 4. What is the rating of that sky?

Edited by WillR, 10 June 2023 - 09:22 PM.

[payner]

So the Bortle rating is a rating of the current conditions with no consideration of one's experience or eyesight? Or does it rate different sites in optimum conditions, and therefore tell us something that is true of one site vs. another? In other words, under the same conditions Cherry Springs is darker than my home, which is true. Not sure I catch your drift.

 

If my eyesight is worse than John Bortle's, then I might rate a sky at 6 that he might rate at 4. What is the rating of that sky?

One rates a site each night one is observing from it or just curious what the prevailing conditions are at the time. It is not based on any preconceived conditions, only what they are at time of evaluation and assessment and the individual's skill (e.g., proper application of averted vision), general eyesight and experience.

 

One cannot truly assess one location from another since it is a point in time (can't be two places at once) under current conditions. Though over time one could begin to distinguish one location from another. To be of any value, that comparison would need to be generally similar between locations as far as prevailing ambient lighting and infrastructure density (i.e., how many buildings, asphalt and prevailing general population (outdoor lighting). As Jon stated, what he would rate a location and what I'd rate the same location at the same time could well have different results.

 

This may give insight why a static point in time based on satellite data cannot be used to apply a Bortle Scale, which is what light pollution webpages attempt to do. So, those maps have little meaning relative to the Bortle Scale.

[Chad7531]

I just stepped outside from the lit up house with my 10x42 binoculars and was able to see m13 with zero dark adaptation. The sky measures 17.51 mpsas and the only stars I can see naked eye are Vega and Denab. It appeared as the faintest smudge and only with averted vision. I just hopped my way up from Vega. It would be very easy to miss if you didn’t know exactly where it was and what to look for, but should be no match for your 8” dob in similar sky.

Edited by Chad7531, 10 June 2023 - 10:56 PM.

[Jon Isaacs]

So the Bortle rating is a rating of the current conditions with no consideration of one's experience or eyesight? Or does it rate different sites in optimum conditions, and therefore tell us something that is true of one site vs. another? In other words, under the same conditions Cherry Springs is darker than my home, which is true. Not sure I catch your drift.

 

If my eyesight is worse than John Bortle's, then I might rate a sky at 6 that he might rate at 4. What is the rating of that sky?

Will:

 

For you it is Bortle 6, for John Bortle it is Bortle 4. 

 

Bortle ratings are not about optimal conditions, they are about the current conditions as seen by you the observer.   This is part of the confusion websites like Lightpollutionmap.info have caused, they have hijacked the original system and tried to make it something it wasn't meant to be. 

 

In the old days, we used colors to rate the different sites.. This appropriately inaccurate and made no pretense of being universal, my backyard is in a red zone meant it was in a city..  A blue zone was quite dark.  A black zone is as dark as it gets.  

 

The Light Pollution Atlas 2020 still uses the colors and does not try to associate the sky brightness with a Bortle rating.  The author is a member of Cloudy Nights and contributes to discussions of light pollution.. 

 

https://djlorenz.git...tronomy/lp2020/

 

The color scale:  https://djlorenz.git...020/colors.html

 

While the Light Pollution Atlas 2020 is not a slick as Light Pollution Map.info, in my experience, it is more accurate.  It agrees with what I measure. 

 

Based on the fact that Researcher lives in Mexico City and can see only Zeta Herculis, a Bortle 9 seems likely. Since Researcher will be using 10x42 binoculars and can see Zeta Herculis naked eye and it is only 5 degrees to M13 and another 2.5 degrees to Eta Herculis, I think he will find it. 

 

Jon

[Researcher]

I just stepped outside from the lit up house with my 10x42 binoculars and was able to see m13 with zero dark adaptation. The sky measures 17.51 mpsas and the only stars I can see naked eye are Vega and Denab. It appeared as the faintest smudge and only with averted vision. I just hopped my way up from Vega. It would be very easy to miss if you didn’t know exactly where it was and what to look for, but should be no match for your 8” dob in similar sky.

Tonight is cloudy here where i live, so im here at cloudy nights  . I planned to go outside and find M13 with binoculars first and then go with the dob but i think ill have to wait for another night