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What should I be able to see?


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Evening all, according to apps I have bortle 5 sky and moderate light pollution from where I view in my garden in North Colchester, Essex.

Realistically what should I be able to see with my set up?

What's the minimum  magnitude I should expect to see.

Trying to maximise my limited viewing opportunities.

Thanks in advance.

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What should I be able to see? is the most natural question, and it would be very easy to answer if there were no light pollution, and no personal differences between observers, but these factors are too variable. So the answer is look at everything, starting from the brightest things, and build up your own experience.

47 minutes ago, Gottzi said:

according to apps I have bortle 5 sky

Light pollution maps are not nearly detailed enough; you might live in a theoretically very bad Bortle zone and have real life decent skies if your site is shielded by walls and trees. The closest lamps are the worst enemies, and just having no direct light in your spot makes it much better. Dry air makes a big improvement, too, so the weather forecast has to be watched, too.

 

52 minutes ago, Gottzi said:

Realistically what should I be able to see with my set up?

Depends on your eyes' sensitivity and what view you find satisfying but that's personal taste so infinite variations. Try viewing the obvious targets like the Pleiades, and then fainter and fainter clusters till you reach your individual don't bother limit. 

 

55 minutes ago, Gottzi said:

What's the minimum  magnitude I should expect to see.

Depending on the night's humidity rate, the scope's magnification (higher is darker), your experience, and the target's height above the horizon, the response will change by two or three magnitudes, so no steadfast answer from others, only your own practical findings.

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Along with @Ben the Ignorant informative post, it is worth recalling that point light sources are easier to observe. These include the moon, stars, planets, open clusters and double stars. Targets which are more sensitive to light pollution and aperture are galaxies, nebulae, planetary nebulae, globulars and comets. These objects have a tendency to spread their light over a larger area, lowering their contrast, so they're more difficult to resolve.

 If it helps with planning a DSO session a very general rule of thumb could be useful:

  • Take the limiting magnitude of your scope, subtract at least 2 or 3 from that number to begin with and choose objects accordingly, making a list from brighter magnitudes to fainter. If after working through the list the faintest objects were observable, work on a magnitude less, and so on.
  • For DSO objects of any given magnitude the smaller it is in size, brighter is the object as opposed to a larger object with similar magnitude.
  • Edge on galaxies are easier to observe than face-on elliptical galaxies.
  • Estimate how big the object will be in the eyepiece. If your field of view (FOV) is a degree and the object is 10 arcmin in diameter then it should occupy about one-sixth of the FOV. Knowing this will help you know what to be looking out for. 

Bearing this in mind, with your scope under reasonable skies you should be able to observe all of Messier's objects, a thousand or more NGCs, countless double stars, all the solar system's planets, the moon, orbiting satellites, comets, large asteroids and with appropriate filters the sun in white light. All you have to do is dodge the clouds and rain and go out and observe. At the end of the day/night there is no magic formula. It must be you who experiences your own successes and failures and come to appreciate what works and what doesn't :smiley:.

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On a phone I cant see anyone's sig so since u didnt specify I dont know what u have.

Also I'm not really sure what the bottle zone 5 is i only go by the colour zone like white red orange etc which I think came out first to my knowledge,  so I stuck to that.

I'll look later when I get to a comp

Joejaguar 

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that link doesn't really say what zone it compares to the coloured zones but that's ok ill figure it out now

so 9 should be a white

8 a red

7 a orange

6-yellow

5-green??

so your a green zone? if so that's great. I have said in many other posts that in a green zone is where the really fun sky starts begins.

iam on a computer now so now I can see your sig its a 4.5" scope. ok its not huge but since I think your in a decent sky conditions I think you can see a lot.

the number one thing even if your in the white or red zones or in any colour zone is to get away from any light sources like streetlights, house lights, portch or garage lights, by doing this you can have your eyes get dark adpted and you can and will see more. Most of my life iam in a white zone which is the worst zone, but I also have been to just about every zone and observed from all zones cept the black zone.

only issue u may have is your scope being 4.5" has a focal length of 1000x mm fl which means it has that barlow in the focuser so views may be softer, also it will be hard to get low power views if those large extended objects.

joejagur

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on another note I have once read that bortle zone and what u can see and it seems wrong and that's y I don't use it and prfer the colour charts better. for instance in the red zone it was m31 can be seen with your eyes and that's wrong I cant even see that in a yellow or maybe a green zone. m31 is HUUUGE so its light is spread out. and I think it also says somewhere where you can her m13 which I have never also seen it yet my eyes is 15/20 based on the last eye test.

to the ones that don't know what that is 20/20 is average 15/20 is a lot better then 20/20

anyway it don't matter if u like the bortle zone compared to the coloured zones its fine it just seems wrong the first times I read it and I stick to the colour zones seems easier and since it doesn't say what u should and shouldn't see I think that may be better as there can be 1000's people each having different eye conditions and sky conds that's will effect bortle zones.

joejaguar

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16 hours ago, Gottzi said:

what should I be able to see

Hi

How about M45 and m15 with your 32mm eyepiece? The first is easy and by the time you've found the second, m42 will have risen. Plan?

Cheers and good luck.

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25 minutes ago, joe aguiar said:

that link doesn't really say what zone it compares to the coloured zones but that's ok ill figure it out now

so 9 should be a white

8 a red

7 a orange

6-yellow

5-green??

so your a green zone? if so that's great. I have said in many other posts that in a green zone is where the really fun sky starts begins.

iam on a computer now so now I can see your sig its a 4.5" scope. ok its not huge but since I think your in a decent sky conditions I think you can see a lot.

the number one thing even if your in the white or red zones or in any colour zone is to get away from any light sources like streetlights, house lights, portch or garage lights, by doing this you can have your eyes get dark adpted and you can and will see more. Most of my life iam in a white zone which is the worst zone, but I also have been to just about every zone and observed from all zones cept the black zone.

only issue u may have is your scope being 4.5" has a focal length of 1000x mm fl which means it has that barlow in the focuser so views may be softer, also it will be hard to get low power views if those large extended objects.

joejagur

Both 9 and 8 are considered white zone, 7-6 is red, etc. In fact there is neat "conversion" diagram that one can use to switch between different designations (like Bortle scale, color scale, NELM, SQM and such):

sky-brightness-nomogram.gif

In any case Bortle 5 ranges from about SQM 19 to 20, so that gives good indication for observable surface brightness. Add 8.89 to magnitude in arc minutes squared - listed in Stellarium for example and if that number is above 20 you will be able to see some of that particular DSO - but that will depend on position in the sky and transparency on given night. It will also depend on distribution of light as magnitudes in arc minutes squared are usually average magnitude for object - galaxies with prominent core will be easier to spot as core will have larger brightness than what average suggests.

Back to original question - you should be able to see quite a bit, just adjust your expectations on what it should look like. In Mag18.5 skies (that is border between red and white zone, so bortle 7-8 border) with 100mm scope I was able to observe a number of M's - mostly globular and open clusters, but some nebulae as well and a couple of galaxies.

27 minutes ago, joe aguiar said:

on another note I have once read that bortle zone and what u can see and it seems wrong and that's y I don't use it and prfer the colour charts better. for instance in the red zone it was m31 can be seen with your eyes and that's wrong I cant even see that in a yellow or maybe a green zone. m31 is HUUUGE so its light is spread out. and I think it also says somewhere where you can her m13 which I have never also seen it yet my eyes is 15/20 based on the last eye test.

I'm at above border of red/white and I can see M31 with averted vision on night of good transparency, so red zone it should not be a problem most of the time. With 8" scope I once observed dust lanes from same location - mind you it was night of very good transparency and M31 was near zenith.

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Good advice everyone, thanks 👍

Just had a couple of hours outside, started with M45, beautiful as always, then spent ages looking for M31 really struggled with it being almost overhead, couldn't get the right angle to be able to see the circles in my Rival Quickfinder. Found it eventually and watched it for a good 30 minutes trying to see as much as possible. Then went to M42 which is always impressive.

So as advised starting again with brighter objects and thoroughly enjoying it.

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