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Buying First Real Scope

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#1 gcdouglass

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Posted 11 August 2019 - 06:44 PM

For the last two years having been using a Celestron Travel Scope 70mm and been happy with it. Got me into the hobby and allowed us to see starts in a very light polluted area that otherwise it almost starless. About a year ago bought a Meade 4500 telescope at a yard sale. Recoated the mirror.  Like that can see more with the Meade but prefer the contrast with the refractor. 

 

Most of viewing is at home in an area with high light pollution.  Mainly go outside for an hour or two and enjoy the planets and a few of the brighter Messier objects. Have kids and once an object is framed they will come out look for a minute and go back inside. 

 

After a couple of years of saving looking to buy first real scope.  Torn between a Sky-Watcher ProED 100mm on a Porta II mount and a 10" Dobsonian. Since most our viewing sessions are brief and the planets thinking of going with the refractor. I know the mount may be lacking but seems like the best bang for the buck.  Should be an improvement over the camera tripod currently using with the travel scope.

 

But torn as I think the dobsonian will be less expensive and views should be good.  In 7 years when kids are older and I can get to dark sites, I think the dob might be better.

 

Keep changing my mind each day.

 

 

 

 



#2 Barlowbill

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Posted 11 August 2019 - 07:01 PM

Dob, Dob, Dob

9X50 Raci finder and a green laser on a dual mount.  Heavenly!  Good luck


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#3 grzesznypl

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Posted 11 August 2019 - 07:21 PM

10 dob is pretty capable telescope regardless if you use it in the city's environment or dark site. On the other hand good refractor (Apo/ED) on light alt/az mount has its own advantage. In the perfect world you want to have both, each serving its own purpose. If you can only have one then dobsonian will probably be not only much cheaper but will allow you to gather more light and simply see more.


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#4 vtornado

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Posted 11 August 2019 - 07:41 PM

Hello Douglas,  I have a synta f9 100mm refractor on the porta, and it is a bit shakey.  I found it hard to focus at high power.

It would work on a cg4, but then you are on an equitorial mount, which is not as intuitive, and has the counter weight which

makes it heavier than the alt-az. 

 

Astro-tech makes an f7 100mm ed.  I don't have one to try but theoretically, it would be more stable on the mount.

 

An 8 inch dob will show you more even on bright objects.   A 10 inch will show you more, but it is bigger and has a longer cool down.

I have many scopes, it I had to cut it down to one, it would be a 8 or 10 inch dob.

 

Do you have access to a star party where you could look through some of these?



#5 SteveG

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Posted 11 August 2019 - 08:10 PM

The 10” dob will slaughter a 4” ed on planets, and everything else. You should get the 10” to really show you the sky, perhaps all you will ever need. A 4” refractor is a nice complenmentary scope to the dob, for quick looks.


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#6 gcdouglass

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Posted 11 August 2019 - 08:26 PM

Went to a star party a while ago. Saw M13 in a 10" dob and 8" dob. The improvement in the 10" decided for me to go with the larger dob if I every get one.  

 

Preferred the sharpness of the Saturn on the refractors vs the dobs. 

 

I see there is another one coming up at locally the end of August. Put on calendar so I can see if anyone there has a 100mm refractor I can compare to the dobs.



#7 MalVeauX

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Posted 11 August 2019 - 09:01 PM

Heya,

 

Tough call. Both are excellent for the same thing. The 10" will do better for DSO. The 4" will do better with less time and no preparation on a planet with only minutes of viewing time and be effortless to use. Convenience plays into this. And the 10" mirror to show its best image is going to need thermal acclimation. Seeing conditions play a lot into this. If your seeing is great, regardless of light pollution, the 10" will show a lot on the planets. But if seeing is poor, and thermal acclimation isn't achieved, you may not see much better on planets than from the 4" in the same night. So it makes it tricky to choose. If you do swing towards the 4" APO, you might want to look into a better mount (Skyview Deluxe comes to mind). At the end of the day though, if the 10" is too heavy and becomes a chore to setup and use versus the refractor, then it makes it pretty obvious what to do. You get more scope for the money with reflectors in dob mounts. Going from 70mm to 100mm isn't going to be life changing, it's better, but not profound, the contrast difference going from fast achromatic doublet to ED doublet will be significant though, so going from your 70mm to a 100mm ED APO will mostly be nice from contrast but not a huge change in what is actually resolved. The 10" will actually increase resolution significantly. There totally is a thing to refractor views, its the contrast (due to unobstructed optics). In a perfect world you'd want both of these scopes honestly. It's a hard choice either way. Regardless of the light pollution, the 10" will simply show more than what the 4" can offer, ever.

 

My opinion: get the scope that will get used the most often and the fastest with the least put away time so that its not a chore and you can do it any time, all the time. It will simply be the "better" scope because you'll actually want to do it. If DSO is more is more important more often, get the 10". If planets are your things, all day, the 4" makes sense under poor seeing conditions.

 

My kids can use refractors on a mount with slow motion control WAY better than a reflector with no controls.... if you think about it and it matters.

 

Anecdotally, last week, my 5 year old looked outside with bare naked eyes and said "That's Jupiter" and was correct. Later we looked at it with a 8" aperture at 250x magnification, and my 5 year old described the great storm bands and some bright moons and once again proclaimed it to be "Jupiter". So 7mm versus 200mm aperture.... same results for my 5 year old. *Shrug* Hah. I looked and the seeing was bad and contrast was low. I much prefer a planet in a large refractor that is really long (or truly APO). I prefer big aperture reflectors for DSO.

 

Then again... I cave to in to my kids. Get everything! flowerred.gif lol.gif blush.gif

 

6" F10 on an AltAz:

 

39864477391_837d819bbe_c.jpg

 

4.5" on AltAz (really light grab & go, notice no hands on scope!):

 

23978855207_7917318dcc_c.jpg

 

6" F8 in the observatory (huge refractor):

 

45781484261_4e309d6cd8_c.jpg

 

10" F10 in the observatory (SCT):

 

45224513334_f14c0fc848_c.jpg

 

Prepping star party with a field of 80mm refractors all over:

 

45239015264_a994810555_c.jpg

 

80mm F7.5 APO on an alt-az mount, it's still big for kids!

 

32092452548_bd2bf57ac9_c.jpg

 

Just remember... if its for kids, truly, keep it simple and fast. They have low patience and little tolerance for what they are seeing. For you, its different, its more cerebral. Easy and fast is my #1 with kids. My kids love fast small scopes that take zero effort to get and use. I prefer the biggest aperture on DSO and big refractors on planets (high contrast). We're all slaves to convenience. There are days I won't open the observatory because my grab & go refractor is faster!

Very best,


Edited by MalVeauX, 11 August 2019 - 09:30 PM.

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#8 Jond105

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Posted 11 August 2019 - 09:02 PM

 

 

But torn as I think the dobsonian will be less expensive and views should be good.  In 7 years when kids are older and I can get to dark sites, I think the dob might be better.

 

Keep changing my mind each day.

I think the answer to your question is highlighted right here. Get the dob. Couple reasons why, 10” blow out 100mm any day of the week on any target. You’ll enjoy the simplicity of the dob mount. The 100ED is a planet and lunar killer. Had 2 of them now, but that might be your down the road companion to your 10” dob IMHO. 

 

If if you choose the 100ED, truly look into maybe a better mount. The 100ED’s are long. Then again, I sold everything off just to have a 120ED refractor, including a 10” dob, only because it’s fit my style of viewing from my light polluted backyard. Something to keep in mind. Planets, doubles, brighter DSO, and Luna are my main things and the refractor fit that the most for me. 



#9 whizbang

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Posted 11 August 2019 - 09:47 PM

If it's in your budget, get the Orion XT10i.

 

You don't have to use the computer.  You can hunt and star hop the old fashioned way which is a lot of fun, and, very rewarding.

 

But, if you are in light pollution, or, want to observe when the moon is nearly full, the "push-to" computer will help you find objects that you couldn't find otherwise.



#10 GoFish

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Posted 11 August 2019 - 10:12 PM

The difficulty is that you have arrived at 2 really good options. Either way, you’ll have a great scope. 

 

Arguments for the refractor:

  • Little or no time needed for thermal equilibrium
  • Less affected by poor seeing
  • Takes up less room in the car
  • Easier to set up, take down, and store
  • Feasible for a quick 30 minute observing window

Arguments for the reflector:

  • See more on planets (after it’s had time to come to thermal equilibrium on nights of good seeing)
  • More deep space objects will be observable
  • No vibrations while focusing
  • $$$ vs $$$$

You’ll have to subjectively decide which list of strengths carries the most weight for your situation, but there’s not a wrong answer between those choices. 



#11 aeajr

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Posted 11 August 2019 - 11:12 PM

Either option will be a good one.

 

Here are the factors I would want to know about.

 

Where will you store it?

Where will you use it?

Are there stairs involved?

 

Will you want to put it in your car?  What kind of car?

 

What is your budget?

 

You said you want to view the Moon, Planets and DSOs.  That pretty much covers everything.

 

In cars, power is measured in horsepower.  In telescopes, especially for visual use, power is measured in aperture.  So a 250 mm aperture 10" Dob is much more powerful than an 100 mm refractor.  But the refractor is smaller and lighter.

 

So, is physical size and weight a factor?

Can you store it at ground level? 

 

My scopes live in the garage.  My 12" Dob is on a hand truck making it super easy to move it about, but there are no stairs involved.  I just tip and roll it out.  And it slides right into the back of my SUV.

 

So, what are the decision points?



#12 Sky Muse

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Posted 11 August 2019 - 11:16 PM

If you're wanting an alt-azimuth mount for the 4" refractor, consider this one over the Porta II...

 

https://agenaastro.c...ltaz-mount.html

 

...and at the same price as the Porta II, but more substantial, supportive, yet still relatively light in weight.

 

A 10" "Dobsonian" would make for a mini observatory there at the home, and somewhat portable for camping and travelling.  Its f/5 primary-mirror, however, will "hunger" for corrective and therefore more expensive eyepieces.  In addition, for the higher powers associated with the planets, the collimation will need to be spot-on, and for sharp, pleasing images.  The atmosphere will play its part in that as well.  Collimation instructions...

 

http://www.schlatter...y/collimate.htm

http://www.astro-bab...nian-reflector/

https://garyseronik....-what-you-dont/

 

If you choose a laser-collimator to collimate the telescope, you will need to check the collimator itself for collimation before using it to collimate the telescope, else mis-collimation may result, and the images will suffer as a result.  I prefer the passive tools myself, a collimation-cap or a Cheshire.



#13 Sully606

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Posted 12 August 2019 - 12:10 AM

If it's in your budget, get the Orion XT10i.

 

You don't have to use the computer.  You can hunt and star hop the old fashioned way which is a lot of fun, and, very rewarding.

 

But, if you are in light pollution, or, want to observe when the moon is nearly full, the "push-to" computer will help you find objects that you couldn't find otherwise.

This is what I did. I was in your shoes just about a month ago. I had a deal on a 120mm SW ED but was leaning toward a Dob after viewing both types at our local club. 

 

I found a Orion XT10i locally for a good price and have been out every evening until tonight when the first clouds rolled in. 

 

I live north of Chicago so all the views south are full of light pollution and we have the jet stream overhead so not great seeing. Even with these limitations the Dob has been great and I’m looking forward to clearer/darker skies. I wanted to learn the old fashion way and not use the push-to function so that I would have to really understand the night sky. In the last week the moon came out and the push-to was a godsend. I was still kinda star hopping because I was motor pushing that thing around. 

 

As as others have said, its a no-lose situation. I asked the same question in a post and, like this one, had some really great responses. I haven’t figured out how to post a link to my previous post but you should be able to find it under my screen name. Good luck, you’re going to love either upgrade. 

 

Sully

 

ps. I keep my Dob on rollers in my garage. I take it out early and it’s ready to go when the sun goes down. I my situation I would have had to disassemble the refractor and put it into its case for every session. Your mileage may vary. 



#14 sg6

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Posted 12 August 2019 - 01:58 AM

Forget 7 years time, by then too many factors will have changed.

Since you have tried in effect both options at a star party which are you most comfortable with?

Always think that if you "like" a scope you will use it more. And an 80mm outside will show a lot more then a 250mm in the garage.

 

Big newtonians have their own "problems". They are fast - they have to be otherwise the eyepiece sits too high up for you to look through it at times. Being fast they need you to be comfortable with collimating them, suspect most experienced users will just check and adjust almost every time. You need, owing to the fast bit, better eyepieces. Likely would buy eventually good eyepieces anyway but you may not get the choice. Being fast you could need a coma corrector to get a good image at the eye - making a good parabola is not easy and the edges tend to be spherical rather then parabolic. The production detail is they make a spherical mirror then "parabolise" it. Being a bid newtonian they are big, that lump of glass is not light.

 

In a way not a case of buy and forget.

 

A 100mm ED can show CA, likely minimal and likely of no great consequence, and you lose aperture - this is the main one. With children you have the prospect of adding a DSLR to an ED and obtaining images - something many people at least try, if you go buy a good mount suitable for at least giving it a go. They cost.

 

Suggest you try and ignore the many positive you get told and examine the negatives. People tend to find things they cannot live with. If something doesn't click you will not make the use of it you should/could.

 

Has to come to that odd factor of which will you enjoy the most. Forget all the assorted specifications. Me, I use a 70mm most. Just enjoy it, it is fun, it is easy. And I do have both bigger and better.

 

Any chance of another star party or outreach to gather more information?  Although the observing season will soon be upon us and you will want one scope or the other.

 

The other option: Get both.

From someone with 7 scopes and presently building a portable dobsonian (hopefully)



#15 gcdouglass

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Posted 12 August 2019 - 08:41 AM

Thanks for all the great advice.

 

I will use it at home. Besides the light pollution their are neighbors tree that limit viewing near the horizon in the east and south. Have been able to work around by moving scopes around yard to see between the trees.

 

To be stored in the dining room replacing the meade 4500 currently residing there.  Only two steps out of the house.

 

Currently taking maybe once a year camping taking in a minivan.

 

Really do not view the moon other than a quick look.  So far mainly have been looking at planets and a handful of Messier Objects (M42, M45, M35, M13, M11, M5)

 

Budget of under $1100.

 

Planning on going public star party on 31st to take a final comparison.



#16 grzesznypl

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Posted 12 August 2019 - 08:44 AM

... Being fast you could need a coma corrector to get a good image at the eye ...

 

You do not need comma corrector with 10 inch Dobsonian and I am speaking this out of my experience (look signature). Of course CC could not hurt quality of your image however as mention above you going to need much more expensive eyepieces (ES 68º and 82º series works great) for fast Dobsonian then you would need for neutral or slow refractor.


Edited by grzesznypl, 12 August 2019 - 08:44 AM.

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#17 MalVeauX

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Posted 12 August 2019 - 09:03 AM

 

Really do not view the moon other than a quick look.  So far mainly have been looking at planets and a handful of Messier Objects (M42, M45, M35, M13, M11, M5)

 

Budget of under $1100.

I wonder if something like a NexStar system with an 8" SCT (C8) would be an option. Lots of aperture, portable, easy to use system, it will track a planet or DSO so you can just view for a while and not fiddle keeping it in the FOV. Should be able to get one around your budget ready to go out of the box. No CA on the mirrors and friendly to all eyepieces.

 

It would be really good to go to a star party and get an idea of what it's like to pick up a mount & 4" refractor and walk around with it and how the views of your subjects are. And compare that to moving a 10" dob reflector around and what it's like to use it. There's always going to be an argument for more aperture. And there's always going to be an argument for faster and easier setup and use (Grab & Go) simplicity. This is why your choices are hard because both options are excellent, just different paradigms and often everyone ends up with both.

 

I know that if I were to part with all of my scopes, I wouldn't keep my biggest, I would likely keep a 120mm aperture refractor and let the rest go, just being realistic about how it would be used and how often and all. If I want to view for just 5~10 minutes and go back inside, I can do that with a small aperture refractor. I can't really do that with a huge aperture instrument that is heavy, needs to thermally acclimate, etc. I'm a slave to convenience, to the point of having an observatory where my big scopes are always setup and ready and I can do those 5~10 minute sessions without setting up, so I do use my big scopes often, but only because I built the observatory. Without that, and if I had to reduce things, I would totally be using a grab & go for my "daily."

 

Very best,


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#18 aeajr

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Posted 12 August 2019 - 09:36 AM

Thanks for all the great advice.

I will use it at home. Besides the light pollution their are neighbors tree that limit viewing near the horizon in the east and south. Have been able to work around by moving scopes around yard to see between the trees.

To be stored in the dining room replacing the meade 4500 currently residing there. Only two steps out of the house.

Currently taking maybe once a year camping taking in a minivan.

Really do not view the moon other than a quick look. So far mainly have been looking at planets and a handful of Messier Objects (M42, M45, M35, M13, M11, M5)

Budget of under $1100.

Planning on going public star party on 31st to take a final comparison.

Great info in your posts.

So, most of us end up with three types of optical devices:
  • Binoculars
  • Smaller grab and Go - typically 70 to 130 mm
  • Light Bucket - Typically 8"/203 mm or larger
So, the question is, which spot are you trying to fill.

You have a 70 mm refractor - Not a great one but it seems to work for you.
You have a 4.5" reflector and it seems you are planning to replace that.

So, it becomes a question of which slot you are trying to fill. That 100 mm ED refractor sounds GREAT to give you a more powerful and higher quality Grab and Go. Great for the Moon, planets and brighter DSOs. And there are plenty of brighter DSOs.

The 8"-12" Dob works great on the Moon and Planets too but really gives you the "reach" to hit many of the dimmer DSOs and bring up more detail on the brighter ones.

I too am in a very light polluted area.

M31, the Andromeda Galaxy, is a small gray smudge in my refractors, Mak and my 8" Dob. Have not tried it in the 12. But if I go to a somewhat darker area with less ground light pollution the difference is dramatic.

M13, the Hercules Globular cluster, was a smudge in my 80 mm refractors, a little brighter smudge in my 127 mm Mak and starts to show some shape in an 8" Dob. But get to that slightly darker area with less ground light and it shows me shape and I can resolve stars. It is even better in my new 12". And with the 12" from home it looks like it does in the 8" at the darker site.

In visual astronomy, aperture rules.

So it all becomes a question of which slot are you trying to fill?

Assuming you are going to keep using your 70 mm and your 114 mm/4.5", I would opt for an 8" or larger scope. An 8" would gather over 3X the light of the 4.5". A 10" would gather almost 5X as much light as the 4.5. The more light you gather the more detail you can see and the more mag you can apply.

I would use your current scopes as your grab and go and go for the 8-10". Later replace the 4.5" with the ED refractor. (100 mm ED is my next planned scope to replace one or two scopes in that range.)

So, which one? You have a $1100 budget.

Apertura AD10 – $659 ( have the 12") ( leaves money for eyepiece upgrades)
10”/254 mm aperture Dob - Includes roller bearing base 1.25” and 2” eyepieces, eyepiece tray
2” dual speed focuser, laser collimator, 8X50 RACI Finder, Moon filter
I own the 12” version of this scope.
https://www.highpoin...-telescope-ad10


Orion XT10 Intelliscpe ( have owned the XT8i and loved it) (helps you find things)
https://www.telescop...s?keyword=XT10i
Video ( 8 and 10 are the same focal length)
https://www.youtube....h?v=BoVhWDftc3A
https://www.youtube....h?v=EmHogk9pwlw



Then you get into these large aperture GoTo scopes. Fully computerized with tracking.


Orion SkyQuest XT8G GoTo Dobsonian - $1045
Full computerized and motorized 8” Dobsonian so it will find the targets and then track them.
http://www.telescope...yPriceAscending
Video
https://www.youtube....FW_R6e-KlI&t=7s

SKY-WATCHER 8" GOTO COLLAPSIBLE DOBSONIAN TELESCOPE – $1,035
https://www.optcorp....SZhIRoCw9Dw_wcB
Video
https://www.youtube....h?v=XW8nRe_-LyE
Demo of the GoTo system
He is using a tripod mounted scope but the GoTo system is the same for the Dobs
https://www.youtube....h?v=C03CdNY71k8


Celestron NexStar 8SE - $1199 - Goto Schmidt Cassegrain
SCT style telescope – computer assisted and motorized so it will find the targets and then track them.
https://www.telescop...-8-se-telescope
Video
https://www.youtube....h?v=Kz_MJQF37lY


Different types of Telescopes
https://telescopicwa...-of-telescopes/

#19 Sky Muse

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Posted 12 August 2019 - 10:46 AM

Thanks for all the great advice.

 

I will use it at home. Besides the light pollution their are neighbors tree that limit viewing near the horizon in the east and south. Have been able to work around by moving scopes around yard to see between the trees.

 

To be stored in the dining room replacing the meade 4500 currently residing there.  Only two steps out of the house.

 

Currently taking maybe once a year camping taking in a minivan.

 

Really do not view the moon other than a quick look.  So far mainly have been looking at planets and a handful of Messier Objects (M42, M45, M35, M13, M11, M5)

 

Budget of under $1100.

 

Planning on going public star party on 31st to take a final comparison.

The more time you take in deciding, the better the decision in the long run.  I spent a week before deciding upon my definitive 4" refractor, and back in 2003. 

 

One of the telescopes that has been suggested is an 8" Schmidt-Cassegrain with a go-to mount.  It simulates an 8" f/10 Newtonian, or "Dobsonian", but in a short, compact tube.  That's what makes it so popular among amateurs...

 

8" Newtonian/"Dobsonian"... https://i.pinimg.com...7e50d3d9ef5.jpg

8" Schmidt... https://cdn.shopify....pg?v=1529944328

 

But the focal-length of the Schmidt is almost twice as long; narrower views of the sky at the lowest power, but with greater ease in reaching the higher powers, with inexpensive eyepieces to boot, although there are focal-reducers available for Schmidts, which will enable somewhat wider views, and with 2" eyepieces.  In addition, the Schmidt's secondary-obstruction, which reduces contrast and sharpness, is larger than that of the 8" Newtonian.  With the Schmidt, however, there are no secondary spider-vanes to degrade the view further; a toss-up I suppose in that.  Also, of all the mirrored telescopes, reflectors, the Schmidt is the easiest to collimate, when needed.  With the open tube of the Newtonian, the main mirror acclimates more quickly to the outdoor conditions, for steadier viewing.  A Schmidt requires a dew-shield, absolutely, despite vendors' listings which fail to mention the need.  A Newtonian does not, ordinarily.  Of note, users of the Celestron 8SE have reported instability issues, of that size telescope mounted on the SE mount.  Celestron does offer their 8" Schmidt on their "Evolution" mount, as illustrated above, and at greater cost.


Edited by Sky Muse, 12 August 2019 - 10:46 AM.


#20 grzesznypl

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Posted 12 August 2019 - 11:23 AM

You guys not paying attention. Topic Starter mentioned $1100 budget. Any 8" computerized Schmidt would put him well over that budget. TS mentioned also that majority of his viewing will be done from light polluted backyard so good luck with high magnification. 10" (or even 8") Dobsonian seems to me most logical choice. Apertura AD10 offers bigger aperture over 8" Schmidt, would cost him $679.95 (****, price went up from $659.95) leaving plenty of money left to buy quality eyepieces and and other accessories. Not to mention that wilder FOV over Cass would make transition to bigger telescope much easier. 



#21 tomykay12

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Posted 12 August 2019 - 11:33 AM

Dob.



#22 SeattleScott

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Posted 12 August 2019 - 02:38 PM

Remember him saying he has to move the scope around the yard to dodge trees? That effectively eliminates GoTo options. Sounds like he doesn’t do much DSO anyway.

So what is portable enough to easily tree dodge? A 4” Apo on that Skyview Deluxe Mount. Preferably an F7 like the SV Access model on close out sale. Maybe a 6” Dob or 6” F5 newt on the GSO mount.

I get the whole 10” Dob thing. But I also know I tend to use refractors when I am out with my kids. At the last star party I felt like my AR6 was surrounded and besieged by Dobs and SCTs. But my 6 year old has an easier time with the lower eyepiece height of a long tube refractor. Yes you can get an observing chair or step stool, but how big are your kids? How tall of a ladder do the need to reach the focuser on a Dob? Well that’s one more thing you have to haul out, and carry around the yard with you as you dodge trees. So if the kids are really driving this, and you have to dodge trees, and some of the kids are less than five feet tall, and they prefer short lunar/planetary sessions, then the Apo is the obvious answer. It isn’t the most capable scope. But it is the best for the circumstances you describe.

I do have a friend who can move his 10” Dob around his yard to dodge trees. But he is a big guy. There are potentially options for wheelbarrow handles to make tree dodging easier with a Dob if you are handy like that. But the planetary viewing will still be hampered for a good 30 minutes due to cooling. Sure, you could add three fans on back and install a couple boundary layer fans if you enjoy cutting holes in metal tubes. Anything is possible. But a big reflector is also going to be hampered more by poor seeing. And collimation. And diffraction spikes. And in the winter, by air currents caused by your body heat next to the tube opening. So yes under the right circumstances a 10” Dob will best a 4” Apo on planets, but the Apo is always giving you its best shot. It will perform more consistently, even if not always as well.

Scott
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#23 Jond105

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Posted 12 August 2019 - 03:03 PM

To the OP, I get why you want the Sky-Watcher 100ED. It’s on sale this month, you get the diagonal and a couple of usable eyepieces with a nice case. If your dodging trees, and watching with your kids, it’s the simplest route I feel. As far as Skyview Deluxe with this scope, it’s pretty bad. The mount is good, for a shorter refractor like an AT102ED though, as I’ve had the 100ED with this set up, and did not like it. The AT102ED would be a much better fit for it, but then you’ll have to get your own diagonal and other accessories. Something to keep in mind with the mounting requirements these 100ED’s really need. 

 

And you may not be a viewer of the moon so much now with your 70mm, but adding either of these scopes, the moon actually becomes something entirely different to view. It’s becomes extremely nice. Something to keep in mind. 

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#24 SeattleScott

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Posted 12 August 2019 - 03:27 PM

Yeah it’s not just the F ratio and length. The 100ED is nose heavy, which makes a long moment arm at the focuser. The AT102 has a more substantial focuser that will make it better balanced and consequently more stable, in addition to being shorter.

Scott

#25 spongebob@55

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Posted 12 August 2019 - 03:34 PM

Went to a star party a while ago. Saw M13 in a 10" dob and 8" dob. The improvement in the 10" decided for me to go with the larger dob if I every get one.  

 

Preferred the sharpness of the Saturn on the refractors vs the dobs. 

 

I see there is another one coming up at locally the end of August. Put on calendar so I can see if anyone there has a 100mm refractor I can compare to the dobs.

if you're going to another star party, go early a ask around to see if you can observe with your current scope close to a 10" Dob and/or a 100mm refractor.  Describe your issue to these observers and ask if you can take looks through their scopes and compare.   Doing this and seeing it for yourself will convince you which way to go.  You might even, depending on the club, send an email to the club describing your issue and asking for help from members.

Also remember that seeing and colimation have a lot to do with what you've seen through those other scopes, especially if they were on different nights.  So you might have looked through a 10" that wasn't so hot, it might have been poorly colimated.   If you look through a DOB, just focus in and out and you'll see if its properly colimated and if there's any plumes coming off the mirror indicative of an uncooled mirror.

Seeing will be convincing.   We can suggest a way to go on and on, but actually seeing it will clear it up in your mind.

Good luck and have fun.

Bob




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