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Worth getting an 8SE in Bortle 7 skies

Beginner Celestron Equipment SCT LP
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#1 Willarkin

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Posted 05 December 2021 - 01:59 PM

I have a small back yard in the outskirts of London, suburban skies, Bortle 7 according to the dark skies maps. I've bought an Astroview 90mm refractor with some good eyepieces and I'm enjoying learning about the night skies - planets and the Moon look good - but even a bright nebula like Orion isn't very visible and is fairly underwhelming in these skies.

 

I'm wondering about a Celestron 8se - it's a lot of money, but I feel it would be worth it if it makes a considerable difference to viewing anything in the deep skies, Messier objects and so on. 

 

Does anyone have any experience of using an 8SE in Bortle 7 suburban skies? Am I going to see much more than with the 90mm - will any difference be worth paying £1,500 for?

 

Thanks!!!

 

 



#2 PETER DREW

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Posted 05 December 2021 - 02:29 PM

You will always see more with an 8se than a 90mm if both in a Bortle7 sky.  I have an 8se that's used in less than ideal dark sky conditions and it does surprisingly well on DSO's, specially ones that benefit from higher magnifications as it darkens the sky background.  Moon and planets will be much better as well. It could be argued that an 8" or 10" Newtonian would be even better at much less cost but more to physically manage.



#3 Anony

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Posted 05 December 2021 - 02:31 PM

I'm in Bortle 6-7, and an 8" dob definitely shows more than my 80mm refractor (or any scopes I have in the 3.5-5" range).

 

However, I'm not sure I can say it's worth £1,500 unless you want the go-to aspect of things.

 

Otherwise I'd say it's worth the $450-$500 or so for an 8" dob... but the pricier things get, I kind of lean the other way, sort of diminishing returns when things get super expensive.


Edited by Anony, 05 December 2021 - 02:32 PM.


#4 macdonjh

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Posted 05 December 2021 - 03:01 PM

Willarkin, welcome to Cloudy Nights.

 

I use an 8" scope in Bortle 9+ skies.  However, I gave up trying to observe DSO from home a long time ago.  The reason I use an 8" scope to view the moon, planets and double stars is brightness at high magnification, resolution and color.  Previously I used 4" and 6" scopes at home and the Great Red Spot, for example, was tan.  With my 8" scopes it's at least pink, sometimes red.

 

Maybe Bortle 7 skies are darker enough than those above my driveway to let you see some DSO.  If you don't have a way to look through an 8" scope in town, a fairly risk-free way to find out if it's worth it to you is purchasing a used 8" Dobsonian.  If you like the views, either keep it or sell it to fund the 8SE you're considering today.


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#5 Willarkin

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Posted 05 December 2021 - 03:59 PM

Thanks all, that's all very sensible advice. Thank you for the warm welcome too! 

 

It does make sense to look for a second hand 8 inch Dobsonian - I have to confess I'm put off by the idea of having to collimate it, I can imagine it being something I'm not good at, or unable to tell whether it's collimated or not. I understand the 8SE needs collimating a lot less.

 

I'm also thinking that, with greater magnification, I would need a computer tracker to keep objects in the viewfinder. At the moment I'm enjoying trying to learn what's up there with a manual telescope, using charts and books, but I can also imagine that the GoTo ability will ultimately help me much more. I'm fairly limited in that the skies to the south/west and overhead are good for viewing but the north/east is practically blinding with two uncovered street lamps and a neighbour's security light - so in those sections of the sky I'm wondering if a GoTo might find objects for me which I could never normally find

 

I'll start searching online for 2nd had Dobs anyway :) Thanks again


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#6 sevenofnine

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Posted 05 December 2021 - 04:17 PM

DSO's are going to lose some of their WOW Factor in Bortle 7 skies but you will be able to see many of them. M81-82 are always in Bortle 5 skies for me but I still enjoy looking at them. Getting a cheap 8" Dob to start is a good idea. Don't sweat the collimation issue. An 8" Dob is quite forgiving of slight errors and still gives good views. Get an Orion Lasermate Deluxe II. It's good enough for this size and speed of scope and makes the process very easy. Go-to is nice to have but I would save the expense. Locating many of the brighter DSO's is not that tough. Just get a 9x50 RACI optical finder and a Telrad. You will be finding objects in no time and finding them is part of the fun. Best of luck to you!  waytogo.gif


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#7 Echolight

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Posted 05 December 2021 - 07:37 PM

I live on the southern outer edge of the urban light dome, under Bortle 7 skies. I never view to the north. And I have a 20 year old C8 that I bought used last year on a Nexstar mount, the precursor to the SE. The price was right.

It definitely shows more nebulosity and other faint DSO’s far far better than a small scope. It shows M42’s bat wings very well.

But even on the heavy duty 2 inch tripod, it seemed undermounted.

 

I tried it on an AVX, but never really used it much. 

 

So all during that time, when I wanted to use a big scope, I almost always used a 6 inch achromat on a tall manual mount instead of the C8.

The C6R is a terrific deep sky scope itself. These are highly demonized. But I can’t say enough good about it. But it is BIG.

 

Now I use the C8 with a reducer and 2 inch eyepieces for a wider field of view. You’re not supposed to do this. But I like it.

And I have put it on a manual alt/az type mount rated for 40 pounds. It is very stable on this mount.

And I finally feel like I have it like I want it. 2 degree field of view. And because it is so light and easy to use for an 8 inch scope now, and the eyepiece travel is so short and so easy to manage with my mount, I will begin to use it as maybe my most used scope. I really love it now.

 

But I don’t know that would buy a new 8SE. Maybe I would buy a 6SE though. A 6 inch scope is also a big step up from a 90mm.

 

I have an 8 inch dob too. But meh. It’s just not me. It’s not that it’s not a great scope. It is. I just don’t get along with the eyepiece position. Maybe if it was an ES Firstlight (aka Bresser Messier) with the rings so I could rotate the tube to position the focuser and eyepiece like I want. But I got this one used for cheap so I thought I would try it on for size. It just wasn’t a good fit.

 

Edit:  As you can see, even under Bortle 7 skies, I prefer a manual mount. I can find most DSO with binoculars. I may not be able to see more than a smudge. But I can find them. And once I find them in binoculars, I can more easily point my scope at them.

But a C8 without reducer and with 1.25 inch eyepieces only offers a 0.78 degree field of view. So very difficult to get stuff in the eyepiece.Sometimes, even with GoTo, it can be a challenge.
Aside from the initial cost, this is a big reason many suggest an 8 inch dob. They offer a reasonably wide field of view. And they are simple scopes that are easy to set up and use. Also, they are less susceptible to dew than an SCT. Actually, there are no scopes that are more susceptible to dew than a an SCT. Of course you can combat this with a dew shield and heated dew strips. I use neither. But we don’t have a bunch of dew here.


Edited by Echolight, 05 December 2021 - 07:54 PM.


#8 macdonjh

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Posted 05 December 2021 - 09:59 PM

I have an 8 inch dob too. But meh. It’s just not me. It’s not that it’s not a great scope. It is. I just don’t get along with the eyepiece position. Maybe if it was an ES Firstlight (aka Bresser Messier) with the rings so I could rotate the tube to position the focuser and eyepiece like I want. But I got this one used for cheap so I thought I would try it on for size. It just wasn’t a good fit.

 

That sounds like you have a Newtonian scope on an equatorial mount.  That is a pain if you can't rotate the OTA.  A Newtonian on a Dobsonian alt-az mount doesn't require rotating the OTA to keep the focuser accessible.



#9 macdonjh

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Posted 05 December 2021 - 10:04 PM

Thanks all, that's all very sensible advice. Thank you for the warm welcome too! 

 

It does make sense to look for a second hand 8 inch Dobsonian - I have to confess I'm put off by the idea of having to collimate it, I can imagine it being something I'm not good at, or unable to tell whether it's collimated or not. I understand the 8SE needs collimating a lot less.

 

I'm also thinking that, with greater magnification, I would need a computer tracker to keep objects in the viewfinder. At the moment I'm enjoying trying to learn what's up there with a manual telescope, using charts and books, but I can also imagine that the GoTo ability will ultimately help me much more. I'm fairly limited in that the skies to the south/west and overhead are good for viewing but the north/east is practically blinding with two uncovered street lamps and a neighbour's security light - so in those sections of the sky I'm wondering if a GoTo might find objects for me which I could never normally find

 

I'll start searching online for 2nd had Dobs anyway smile.gif Thanks again

You make good points.  I bought a go-to mount early on for exactly the reason you state above.  Hand tracking with a manual Dobsonian isn't hard, but I prefer a mount with motors so I don't have to track myself.  Others prefer the other way 'round.  All personal preference.  Also, I agree with sevenofnine: an inexpensive laser collimator will make collimation of an 8" f/6 Newtonian (all commercial 8" Dobsonians) simple and quick.  If you decide to sell the scope after your experiment is over, sell the collimator with the scope and get a large fraction of your money back.

 

Good luck, shopping for gear is fun.



#10 ShaulaB

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Posted 05 December 2021 - 10:22 PM

The 8SE optical tube would need periodic collimation. I suspect a lot of SCT owners don't know that collimation is rather easy, and necessary.
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#11 Echolight

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Posted 05 December 2021 - 11:46 PM

That sounds like you have a Newtonian scope on an equatorial mount.  That is a pain if you can't rotate the OTA.  A Newtonian on a Dobsonian alt-az mount doesn't require rotating the OTA to keep the focuser accessible.

I don’t know where you get that idea.

727F5D7C-22C7-460D-8163-DBEB70ABDDEA.jpeg

 

Point it near zenith and you have to crane your neck and wrap yourself around it. With an ES Firstlight you could turn the focuser to the side.


Edited by Echolight, 05 December 2021 - 11:50 PM.


#12 maroubra_boy

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Posted 06 December 2021 - 03:48 AM

Ok, my 2c worth.

I've been doing astro for some 40 years. Hence I started with all manual push-pull star hopping. I am very proficient with star hopping and at my dark site that's how I do things 90% of the time even though I have a fantastic Nexus DSC system on my 17.5" dob.

From my home however, things have changed a lot for me. Light pollution has gotten very bad and star hopping is a real chore now. I have two 8" dobs at home, both manual push-pull, the other has a Nexus ii on it - both Nexus systems are push-to with encoders on both axis to help find stuff in the sky. The mount I use my 9" Mak is a goto. Today I find I need to rely much more these systems from home as light pollution just overwhelms my ability to find what was a cinch previously.

I used to say to people "go the totally manual push-pull dob". Today, my tune is different. I started with better skies and my star hopping skills were honed under these better skies. Today though, if you are under urban skies, and with the affordable push-to & Goto systems that are available, I would argue these may be a better option.

When I started we also did not lead the monsterously busy lives we have today. Learning to be proficient at star hopping is not a necessary skill. Today it is an affordable lifestyle choice instead.

What has not changed is the learning process of looking through the eyepiece. THIS if anything has become harder/more challenging because of light pollution and reduced time. So that's the trade-off...

I would actually suggest instead of making a purchase decision based on what you read, my suggestion is to go to an astro club meet FIRST, and two or three times before you open your wallet. See these different scopes, mounts and systems, manual, push-to & goto in the flesh and in operation, and then you will be making a far more informed decision.

There is a BIG difference between a 90mm to 8" aperture. More sophisticated gear too. More complicated if you are totally unprepared. Do not underestimate this aspect. A dob is very easy to set up, any Goto system involves more time.

Collimation differences between a Newt & an SCT is an excuse really. It takes all of two min at most to tweak my Newts/dobs and it is a process/ritual that helps me get my eye in & SLOW DOWN. The Maks I have sure don't need collimating anywhere as much, but I find I am rushing with them rather than being more "Zen". Trade-off...

I still do use my dobs at home. It takes me all of 4 minutes to set up up the scope & check/tweak collimation, 7 min with the Nexus. With any Goto system I am lucky if I am set up & running in 20min, plus the Gremlins of power...

Take down at 3am in the morning, I know which I would rather be taking down.

This is the sort of stuff people like you are not even remotely considering only because you just don't know & can't ask about. Also stuff that us here often forget to mention. We all see the glitz of the toys but forget certain basics.

This is why I say visit an astro club meet two or three times before making a purchase. The first is all exciting but too impulsive. The second & third visits the shine has dimmed a little & logic takes over.

Alex.
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#13 eric_zeiner

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Posted 06 December 2021 - 12:35 PM

I agree with going to an astro club a few times in order to get your feet wet.  Had I done this in the beginning, I would have saved a ton of money.  Try as many instruments as you can and then decide.  Personally I settled on refractors but that is a whole different topic.  Good luck!



#14 Willarkin

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Posted 06 December 2021 - 04:01 PM

All this is fantastically helpful thanks! I’ve made contact with Hampshire Astronomy Club in the UK - definitely a good idea for me to go along and try some different options. I did enquire today at Wex Photographic about 8 inch Dobsonians and I was told there may be a waiting time of three months for new stock to reach our shores. So I have tome to think anyway.

At the moment I’m enjoying learning to be slow and patient and find my way around the sky in my back yard the old fashioned way. Even with the 90mm I’m amazed and how many more stars become visible in the constellations and then enjoy comparing them with the charts. Ultimately I think I will save a lot of money, forget about the 8se and go with an 8 inch Dobsonian as recommended. I’ll learn how to collimate and do things step by step.

I’m enjoying seeing the wider and more detailed views of star fields and I believe a Dobsonian would give me the chance for a 2 inch eyepiece and more stars to see - even if I can’t see too many faint DSOs, I think better views of wide field will be plenty to keep me intrigued and involved in the skies

Thanks for your welcoming and non patronising advice. Probably saved me dropping way more money than I need to
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#15 macdonjh

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Posted 06 December 2021 - 09:57 PM

I don’t know where you get that idea.

attachicon.gif727F5D7C-22C7-460D-8163-DBEB70ABDDEA.jpeg

 

Point it near zenith and you have to crane your neck and wrap yourself around it. With an ES Firstlight you could turn the focuser to the side.

...from using a 6" f/8 Dobsonian with my son.  We simply repositioned our observing chair and adjusted the chair's height.  No gymnastics required at the eye piece.



#16 vtornado

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Posted 06 December 2021 - 10:57 PM

It does make sense to look for a second hand 8 inch Dobsonian - I have to confess I'm put off by the idea of having to collimate it, I can imagine it being something I'm not good at, or unable to tell whether it's collimated or not. I understand the 8SE needs collimating a lot less.

 

I find collimating an SCT to be difficult.  It has to be on a tracking mount, or use Polaris.  Turbulent skies which I have often make it difficult to really get it accurate.  However ... it is doable.  You are correct in that as long as the scope is not jarred, it does not have to be touched.

 

An f/6 newt may have to be touched up every time it is used, but it takes 1 minute with a barlowed laser.  I don't need a star to collimate

like the SCT.

 

I'm also thinking that, with greater magnification, I would need a computer tracker to keep objects in the viewfinder.

 

Yes tracking is nice.  As you state, objects do not whizz through the field of view. Second when

trying to identify objects in the eyepiece the view does not change.  This helps me going back and forth between the eyepiece and

the chart.  It also helps if you want to share the view with others.

 

For me the 2000mm focal length of an 8 inch SCT is too narrow.  I prefer a c6.  Not as much aperture, but not as narrow.

 

I live in Bortle 9, An 8 inch scope will give better lunar/planetary/globs/and double viewing.  A narrow field of view may hurt open cluster

viewing.   Only the very brightest nebula and galaxies are visible even with large aperture. 


Edited by vtornado, 06 December 2021 - 11:00 PM.



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