Aperture, light pollution & your back

[spaceboy]

If you live under Magnitude 3-5 skies with St lights and next door neighbours security lights flashing on and off at random and boiler vents spewing out hot air every 10 minutes, would a large telescope be worth the hassle of lumping outside only to have to wait to cool for 50-90 mins just to see that tiny bit deeper than a smaller more manageable scope? For this example I would say anything solid tube up to 8" is easily manageable and anything up to 16" hassle but also realistically manageable by a single person for back yard observing. I know truss dob's of most sizes can go even larger and still be manageable but I think the thought of going through assembly each and every gap in the clouds would rule them out of the running for me.

OK so I know this one has been asked and answered in various forms on various forums. I've also seen a universal trend in replies that no matter what part of the world you live and seeing you get up high, light pollution often dictates what goes on, on the ground. 

Unfortunately this trend also seems to include mention of several scopes so just say for one moment to get the large scope you have to sell other smaller scopes to afford it. So your left with one large light bucket that demands all your enthusiasm to get out in to the garden under skies are not all that brilliant anyway. Aperture is king so it does offer something deeper over a smaller scope but the LP robs the views of any contrast. Any astronomer knows that next to the king there sits a Queen and the Queen in this tale is dark skies.

So you can go deeper at home under LP skies but contrast is never great and there is considerably more effort required to set up. A trip maybe once or twice a year to dark skies would probably make all that effort seem worth while but as always that is weather permitting. Or do you stick with a scope that never really goes deep under LP and while offers great improvements under darker skies, comes no where near to that of a larger instrument ? Or is it that those who do have larger scopes found that they had no choice but to get a second more manageable scope? It does seem to be the case there are multiple scopes when similar questions have been asked. So I guess I could also ask, do you go large and add smaller or small and hold out for large ??

If you have never owned or handled a large scope it is difficult to contemplate what is involved other than through imagination. It is also hard to appreciate the improvement that might be seen in the views that make it all seem worth it so please forgive me if this comes across as an already much debated question.

I ask on this occasion if you have a large scope do you:-

1) use it as often as you would like or does the thought of all the effort put you off more often than not?

2) inevitably ended up getting a smaller more manageable scope ?

3) would give up the larger scope for the smaller scope if you could easily replace the larger scope at a later date?

4) feel the views are significantly better between the larger and smaller scopes under LP to let the smaller scope go?

5) wait until a point where you can have both larger and smaller scopes?

6) the money from the larger scope would come in more handy than it sat gathering dust so get / stick with a smaller scope?

7) the improvements of a larger scope are subtle under LP skies so stick with what you have?

[Demonperformer]

I do not currently own a "larger" scope, but did previously.

1) It was a 10" dob and I found the struggle of getting it in and out of the door to set it up meant that it got used about twice.

2) I eventually sold it and replaced it with an 80ETX which was so easy to set up it got used every night I could.

3) ANY scope that gathers photons produces far more satisfaction from this hobby than one that gathers dust.

4) With the streetlight just across the road (plus another seven that are deemed necessary to keep my garden safe!) I was still able to get down visually to between mag 10 & 11 with the 80ETX

5) I have since "upgraded" to (firstly) a 6SE and (now) an 8SE and use the 80ETX never - and, yes, they produce much better viewing than the 80ETX did.

Maybe not totally answering your questions, but this was my experience.

HTH

[parallaxerr]

Very good question(s), I'll follow with interest........

One factor you don't mention, which is critical in my case is time. Me personally, I get fed up lumping my ED80 about the garden (steep garden to be fair, lots of steps) on a Nexstar SE mount and I'm supposedly "young & fit". To that end I've just bought a 66mm Apo and a carbon fibre photo tripod with fluid video head! Will see which gets used more!

[DHEB]

I will second DP's suggestions, particularly #3. A scope that is easy to setup and use is always better than one that causes head- and back ache to the point of rather notusing it. Living in cities means having to deal with a lot of hinders to astronomy. Better enjoy often a more modest instrument than getting a "cannon" that sleeps in the cellar.

[Stu]

As you know Nick, I've been through a fair number of scopes! I live somewhere near Heathrow, with constant vapour trails and mag 4.5 to 5 skies (best SQM reading has been 19.05 I think).

I used the 16" Sumerian a few times at home before I sold it, but to be honest the best experience I had with it was 4 clear nights at SGL10; just amazing. Although not hard to set up each time, I just had a mental block about it which stopped me using it more at home. The 12" f6 was pretty heavy, so again was an effort to out out. It was also very long, and impractical to fit in the car with anything else, or without knocking it. The 10" f6.3 was lovely, and I would have another in a flash I think. Much easier to carry, faster cool down, easy collimation and suited to planetary and the sorts of DSOs that look good from an urban site ie globs, PNs and doubles.

I know the Dob Mob manage to get away once a month to dark skies, which makes total sense and ensures they make the most of their lovely scopes. Good on them I say. The reality for me though is I just have too many commitments including two older children I see every other weekend and during the week so it would not be fair on my wife (we have a 2 year old daughter); I make an active choice not to even ask because I wouldn't feel comfortable being away that much.

To cut to the chase though, what I have found is that my current Tak FC-100D has turned out to be my most used, and favourite scope of them all. I've been through many small, high quality refractors.

Tak FS-60C

WO SD66mm

Televue 76

Tak FC-76DC

Stellarvue 80ED

Vixen 80M (x2)

Televue 85

Tak Sky 90

Burgess Optical 91mm triplet

AstroTech 106mm EDT

Skywatcher 120ED (x2)

I can honestly say that the FC-100 does as good a job as any of them, and is compact enough to take anywhere I want. For instance it is lighter and easier to transport than a TV85 and gives views which as far as I recall rival the 120ED which is a significantly bigger scope. There is rarely a time when I am somewhere with an observing opportunity when the Tak is not with me. It sits nicely on a good photo tripod, on a Giro-WR mount, cools quickly and the views are stunning. It cuts through poor seeing very well and more often than not gives stable views when larger scopes are struggling.

I use it largely for solar and planetary work from home, often with the tripod on an EQ Platform to give basic tracking. It is quick to set up, and there is also plenty of back focus for Binoviewers with which the solar white light views are incredible when seeing conditions are good to excellent. At a dark site it gives wonderful widefield views of DSOs and does a credible job on globs etc.

Obviously it does not bend the laws of physics. The planetary views in the C9.25 I'm 'looking after' have better resolution and show more colour, but do suffer more from poor seeing; you have to wait much longer for steady seeing. I've joked before about thinking the Tak was better than Derek's 16" on Jupiter, and indeed it was..... Until he collimated it! Outside widefield objects, DSOs are again much better with aperture, if you've got the space for it!

The fact though is I just use the Tak more than any other scope because I enjoy it every time, and find it quick and convenient. Above all I love the quality of the views.

In an ideal world though, and with better finances I would probably have:

Tak FC-100

TEC 140 or APM LZOS 130mm

C8 or C9.25

12" f4 dob

18" Truss dob

That would keep me happy  

[Timebandit]

Hello chaps. Interesting little topic this.

I believe the best scope to have is the one which will get used. There is nothing worse than getting a scope that is to big and you take it outside once or twice before you realise it is just to much trouble and hassle.

I thought long and hard about the scopes of my choosing before committing,as quality scopes do not come cheap and it's an expensive mistake as well as annoying if you get it wrong. That's why I chose the two scope approach as I firmly believe no scope does it all. Therefore a Dob 14 inch and a 120mm apo. 

My thinking behind these choice was that I do love the views of a refractor, in my opinion always just that bit crisper than a Newtonian . And can cut through the atmosphere conditions a bit better. My thinking also was it is a far better grab and go as light pollution is a bit of a problem for me living on an edge of town .As such a refractor on an AZ4 is a nice set up to quickly and easily put in the car and take to a dark site. It also has the advantage of very quickly to set up , no collimation or cool down to really worry about. Therefore if you do want to pop off for a few hours to a dark site, then no real hassel. As I said the best scope is the one that is used.

But as we all know like for like you cannot beat aperture. For DSO there is nothing like having a large aperture scope. This is why the 14 dob was acquired . I do have this set up in outside conditions so no real cool down time or collimation to worry about in use. But living on the edge of town you still suffer from light pollution and even though the 14inch is still better IMO on DSO than the frac it cannot stretch it legs until it is in a dark site. Therefore because of the light pollution problems,when deciding to purchase this dob or not ,first of all I made sure it could be fitted in a car , which it can be a tight squeeze though, also the weight of the scope (you do not want to damage your back or the scope on lifting it around). You also have the problem of collimation and ambient temperature mirror issues. Therefore a lot more thought and time and practice  is needed into moving such large scopes. And therefore if you do have considerable light pollution issues where you live and around you surrounding, then I feel you really do need to be a lot more careful with your scope choice and factor this into the equation when making your choice.

There really is nothing like having a quality scope with a large aperture to be able to get the best images possible. But only if you can take advantage of that aperture to use it , otherwise you are better going for a smaller aperture in a scope that will be used.

As the best scope to buy is the scope that will get used☺

[Roy Challen]

While I have never owned a large telescope - my Tal 100RS being the largest - the clouds and light pollution where I live would make it a waste of time and effort anyway. I don't mind setting up my quite heavy mount and using either the Tal or the Skylight in the garden, but they were both soundly beaten by my Pentax bins under a properly dark sky earlier this year.

I would be happy with/prefer that sort of experience one week a year, rather than poor/mediocre-at-best for the rest of the year. Of course, a large aperture at that place would be truly awesome.

[Moonshane]

I have a 16" f4 dob, a 12" f4 dob, a 6" f11 dob ob an eqp, a 120mm ed frac, an 80mm ED frac and a 100mm and 60mm pst mods.

Ignoring solar, in all truth I use the 120ED and the 12" f4 the most. I have not used the 16" for nearly two years but cannot bring myself to sell it.

as far as your specific questions go.......

I ask on this occasion if you have a large scope do you:-

1) use it as often as you would like or does the thought of all the effort put you off more often than not? I don't use my 16" nearly as much as I'd like. If I had a better site / bigger garden, I'd store it outside in a roll on/roll off shed. But I don't!

2) inevitably ended up getting a smaller more manageable scope ? Yes, but I kept the big one too.

3) would give up the larger scope for the smaller scope if you could easily replace the larger scope at a later date? Yes but I'd almost certainly spend the cash.

4) feel the views are significantly better between the larger and smaller scopes under LP to let the smaller scope go?  The views are often better but the effort is rarely worth it at home.

5) wait until a point where you can have both larger and smaller scopes? see above. 

6) the money from the larger scope would come in more handy than it sat gathering dust so get / stick with a smaller scope? see above

7) the improvements of a larger scope are subtle under LP skies so stick with what you have? see above

[acey]

3 hours ago, spaceboy said:

If you live under Magnitude 3-5 skies with St lights and next door neighbours security lights flashing on and off at random and boiler vents spewing out hot air every 10 minutes, would a large telescope be worth the hassle of lumping outside only to have to wait to cool for 50-90 mins just to see that tiny bit deeper than a smaller more manageable scope? For this example I would say anything solid tube up to 8" is easil;y manageable and anything up to 16" hassle but also realistically manageable by a single person for back yard observing.

For any given observing situation there are three relevant limits: magnitude, resolution and surface brightness. Magnitude and resolution are both dependent on aperture: a bigger scope shows fainter stars, and that continues as aperture increases. With resolution you hit a limit imposed by air stability, and there are arguments that a 4" scope is often enough to reach that limit at typical observing sites. So for viewing stars you'd want the biggest scope you can manage, while for fine details on Moon and planets you're not particularly concerned with aperture (there are a hundred other things that count). That leaves DSOs, where the crucial thing is the limiting surface brightness. And here what counts is magnification: a telescope reduces surface brightness, and the more you magnify, the more you reduce. Larger aperture enables you to use a higher magnification without the target becoming too faint to see, so small DSOs, or small details in DSOs, are more easily visible. But only if the sky is dark enough to begin with. No amount of aperture will show galaxies in daytime (though a telescope can show stars in daytime, and the bigger the scope, the more it will show).

So it's worth putting a 16" in a light polluted garden if you want to look at stars. If you want to look at Moon and planets it's probably overkill. If you want to look at galaxies you are far, far better going to a darker place, even if all you can take there is binoculars.

An 8 inch scope is an excellent all-rounder and easily transportable. I used one happily for years, taking it to a dark site for deep-sky observing, and when it began to feel way too small and lightweight I moved up to a 12 inch. That scope feels just a little on the lightweight side now, but there's still lots left for me to see with it, so I don't plan on getting anything bigger for the forseeable future.

The people who feel greatest aperture envy are often ones who live in light-polluted places and think that aperture would solve their problem, when really the answer is petrol.

So, to answer your questions (in relation to my 8" and 12" scopes):

1) use it as often as you would like or does the thought of all the effort put you off more often than not?

I'm prevented by weather, moon and life, not by the thought of driving for 40 minutes, setting up the 12" in ten, and observing for hours

2) inevitably ended up getting a smaller more manageable scope ?

I went the other way, 8 then 12.

3) would give up the larger scope for the smaller scope if you could easily replace the larger scope at a later date?

No.

4) feel the views are significantly better between the larger and smaller scopes under LP to let the smaller scope go?

With DSOs it makes no real difference - the views from my garden are poor with either scope. 12 is a bit less poor but not worth the effort - if I could no longer drive I'd use the 8" at home and just make do.

5) wait until a point where you can have both larger and smaller scopes?

I have both.

6) the money from the larger scope would come in more handy than it sat gathering dust so get / stick with a smaller scope?

It's my 8" that's gathering dust - I rarely use it.

7) the improvements of a larger scope are subtle under LP skies so stick with what you have?

I'm sticking with my dark site and the 12" I take there.

[D4N]

I don't have a really big scope but my bigger scope doesn't get used now.

My ,title frac stays on its pier and does imaging, my travel scope gets used for solar and I have four pairs of binoculars for everything else

 

Perhaps if I get a bigger obsy and have room to store more scopes there then I will do so but at the moment I am happy with the compromise I have.

[Mark at Beaufort]

I live on the edge of the City and my East/West horizon facing South - virtually no light pollution. I have a 12" Dob with the base housed in a garden shed and the OTA in the downstairs utility room. Unless I know that the sky will remain clear, with no Moon, I don't normally set it up - too much effort!!. However, I have an Orion VX8 f/4.5 scope which is light and sits nicely on a SkyTee 2 mount and Berlebach tripod. I can set this up fairly quickly and use it more than any other scope for night time viewing.

I also have an Astro Tech 4" APO which I use for solar viewing, Planets, Moon and double stars and this also sits on the Skytee 2 mount. I recently acquired an Orion VX6L which has a 1/12th wave mirror which I wanted for planets and double stars.

So I am lucky with my reasonable skies which are similar to Lucksall the SGL star party site. If I had a light polluted garden I would not have bought a 12" scope but would take the 8" Orion to a darker site because it only weighs 7kgs. I am responsible for organising observing sessions for the local Astro Society and we have an agreement to use a National Trust venue which is dark and I only ever take the Orion to these events.

[GuLinux]

Very interesting question, but it really depends on many other things than just diameter and light pollution.

For instance, I'd consider also the mount type, the presence of a backyard (not everyone can have it), having a car.

For instance, when I lived in Milan, I had an 8" S/C on an HEQ5, no backyard, not even a balcony, but I owned car, so I could go in parks and public gardens. I was both concerned about safety, and annoyed about the long setup time of the equatorial mount, so I did that only a handful times. Also the total weight was not at all helping.

So perhaps, even with just an 8" telescope, if you go for equatorial you might still find that this is way too much, for some particular situations.

I prefered to go to darker sites, preferably every new moon, but as you mentioned, the weather doesn't always allow that (in fact, recently, it never did...). I am overall quite satisfied, anyway: I could do visual deep sky observing from the dark places, and a few interesting planetary shots from the city. Sure, I could have done much more, but now I also know what not to do next time.

 

As for now, I have no instruments because of the relocation. But I do have a backyard . I plan to buy both a medium sized (12") dobsonian, and perhaps a small Mak for planetary imaging.

I would go for a very light truss travel dobsonian (Sumerian Optics, 99% sure), so it will be easier to go finding dark places, and I think I will leave it already assembled: this way observing from the backyard will not require a long setup time.  I just have to find the proper way to protect it from the dust...

Having also a smaller instruments is something I would definitely consider, particularly for planetary shooting, which is one of my favourite subjects, although I primarly want to do deep sky, hence priority to the Dob  

 

[spaceboy]

Thanks to everyone for your replies. They have been both enjoyable to read and very helpful indeed. Giving a perspective from peoples personal experiences along with reality checking advice is the reason why I joined SGL in the first place so again a BIG THANK YOU to all in saving me from making a probably one of my more foolish mistakes.

I think my problem is aperture hunger took hold and all sense went out the window after being offered my dream scope. I think in truth though that dream scope should remain in the south of France along with my chateau and Transit custom.

I do have every intension of going up a notch on the aperture ladder but certainly not to the degree I was contemplating. At least now when the right one turns up I will hopefully be able to keep my much loved refractors and have the best of both worlds.

 

THANKS AGAIN

[LukeSkywatcher]

Give me portability/usage over aperture any day. I've found the best scope for me in the 8se. It has oodles of aperture (im sure some will laugh at this) and it is so portable. I dont need/want anything bigger because it would be a dust collector. 

My other scopes are:

90mm Refractor on an EQ mount (used it maybe 5 times and chucked it in the garage.........EQ mount was too heavy and i am not a gymnast so it was too cumbersome).

Skywatcher Heritage 130P "Dob". Love this scope. So portable even i can carry it with one hand while using a wheelchair. It gives great views of most different types of objects.

Celestron 70mm refractor Travelscope (i use it now as my Solar scope in conjunction with a Hershel wedge).

 

[ronin]

Not fully knowing it as I do not own a big scope, 105mm being my largest, but I would guess that a larger scope would show most benefit in a light polluted area when used with a visual OIII, Ha or the combined item of a UHC filter. It would make sense that you collect more, but remove a greater proportion of the LP then of the object wavelengths and so get a greater contrast.

However that means certian nebula only benefit to a greater extent, I would xpect galaxies and globular clusters to benefit less.

One other factor I will throw in is that I know of 3 people that went bigger to a 16" scope, have met 2 of them, those 3 sold up everything after about 4 months. I can only assume that the 16" meant they found the size too much of a problem or hinderance so did not use the scope and that was it.

 

[spaceboy]

18 minutes ago, ronin said:

Not fully knowing it as I do not own a big scope, 105mm being my largest, but I would guess that a larger scope would show most benefit in a light polluted area when used with a visual OIII, Ha or the combined item of a UHC filter. It would make sense that you collect more, but remove a greater proportion of the LP then of the object wavelengths and so get a greater contrast.

 

It is my understanding that LPR filters only filter out certain wavelengths of light IE: Sodium St lights in particular. Sadly unless the light pollution in your area is predominantly sodium lighting an LPR filter is of no real advantage. Now I'm not 100% sure this is a similar case with OIII & UHC filters but there stands a good chance they work in a similar way ???

[Stu]

1 minute ago, spaceboy said:

It is my understanding that LPR filters only filter out certain wavelengths of light IE: Sodium St lights in particular. Sadly unless the light pollution in your area is predominantly sodium lighting an LPR filter is of no real advantage. Now I'm not 100% sure this is a similar case with OIII & UHC filters but there stands a good chance they work in a similar way ???

Nick, UHC and OIII could be described as working the opposite way. LP filters only remove wavelengths of light associated with common forms of LP such as sodium etc, whereas UHC/OIII only allow through the frequencies of light associated with certain objects, notably emission nebulae etc.

That does make them more useful as they can actually make certain objects which are invisible without the filter, become visible even under moderate LP. This doesn't change the fact that all these objects, whether filtered or unfiltered, with a large aperture or small, still look much better under a dark sky with good dark adaptation.

[spaceboy]

Thanks Stu. I did think they were maybe different as I know the Rosetta neb responds rather well to my OIII in that I can't really see it without the filter

I agree that dark skies are key to these filtered objects as the difference is like night and day with something like the Veil.

[LukeSkywatcher]

That does make them more useful as they can actually make certain objects which are invisible without the filter, become visible even under moderate LP.

Exactly. I never saw the Rosette Nebula before i bought an OIII filter. It simply wasnt there. The Veil is another which i never saw until i got the OIII. My UHC filter does exactly what it says on the tin: "It enhances the already visible". I can see M42 with my scopes........the UHC just brings it out more. OIII........makes the invisible........visible.

 

[spaceboy]

That's interesting Paul. What scope do you look at the Veil in? While it is a total no go from home I can see it from a dark site with out a filter. No doubting it is more obvious with a filter though.

[Moonshane]

I can see the main curved section of the veil at home with oiii and an 80mm frac

[LukeSkywatcher]

31 minutes ago, spaceboy said:

That's interesting Paul. What scope do you look at the Veil in? While it is a total no go from home I can see it from a dark site with out a filter. No doubting it is more obvious with a filter though.

These days my main scope is the 8se. I have observed the Rosette and Veil in my Heritage 130P using my OIII.

[spaceboy]

I know it's not possible to see the Rosetta with out a filter (or at least I wasn't able to even at a dark site) but I would have thought you could make out the veil in your 8se with out the need for a filter. Pointless in practice as a filter makes it far more apparent and more enjoyable to look at but none the less not impossible with out filtration.

Shane I can just about make it out in an 8" newt OIII at home but it was so poor it didn't hold my attention for long. I should really give it a go in the 10" come to think of it.

[bish]

49 minutes ago, spaceboy said:

That's interesting Paul. What scope do you look at the Veil in? While it is a total no go from home I can see it from a dark site with out a filter. No doubting it is more obvious with a filter though.

The LP living in Dudley is terrible, but on a really good night I can just make it out overhead with a UHC (I have to wobble the scope to be sure). With the Oiii it's easy to see with direct vision (but only on properly clear nights). That's with my 250px.

[Jonk]

My short 2 year astronomy journey so far has been:

Bought a SW 114 on an Eq2 and SW 150P Dob.

Then a SW150 blue on a motorised eq3 - first attempt at DSLR imaging with tracking mount.

Then I bought a bundle - SW150P, HEQ5 Pro, Modded EOS 30D, webcams - all sorts. This got me into imaging.

After I sold the 114, 150 blue and 150 dob, I read and read about what to do for visual.

I bought a better mount, AZ-EQ6.

Along came a SW 250P, so slowly getting bigger.

Sold this and replaced with a 300P - now this was getting silly, and too big to lug in and out all the time.

Sold the HEQ5 Pro, so was left with the 150p and an ST80 on the AZ-EQ6.

I luckily found a Sumerian 16" dob for sale 20 miles away, went to view it and bought it. This would be great for visual and 16" would easily outperform the 300P.

The 300P was sold, so I was back to a quicker, easier, better scope to set up and observe. I'm so glad I bought it and won't part with it unless I can afford something bigger and better in the future.

The moral of my story is, I had to go through various pieces of equipment to 'learn' what I wanted to do over the past 2 or so years.

Money needed to be spent wisely, but mainly, enjoy what you do have, there's no hard and fast answer as everyone is different, and everyone's conditions / requirements are different.

As long as you're enjoying what you do, like someone said above, the best scope is one that's used.