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Sky-Watcher 10" f/4.7 Traditional Dobsonian Telescope as first telescope?

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#1 Kelthebeginner

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Posted 04 December 2020 - 12:10 AM

Hello I am Kel.

 

For the past 3 years I have been wanting to buy a telescope and now for the past 3 months I have been seriously looking to purchase one.

 

The purpose of this telescope would be to look at stars, galaxies, nebulas, planets, and moons from northern Utah with my girlfriend. The skies out here look nice enough.

 

I have been looking at the sky-watcher 10" dob for $610. But I need advice on what accessories I should get with it and if this telescope is a good idea for what I want to see?

 

I appreciate any information you guys/girls can provide.



#2 vtornado

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Posted 04 December 2020 - 12:27 AM

Hi Kel and welcome to CN.

 

A 10 inch dob is a great scope.  Nothing will show you more for that price. 

Do note that it is kind of big.  (Tube is 4ft tall, 12 inches in diameter and about 30 lbs)

You will have to learn collimation, and it takes about an hour to cool. (planning can fix this).

 

The things I use every night are.

sky safari - an app to help you find object that downloads to a phone or tablet.

32mm plossl.   widest possible field in a 1.25 inch eyepiece.

Then some other eyepiece ranging from 20 down to 5mm.

Red beam flash light.

It is cold ouside, you need some nice clothes to keep you warm.

 

Look into making a degree circle and and angle meter to help you find dim objects.


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#3 SeattleScott

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Posted 04 December 2020 - 01:09 AM

Yes it is cold in Utah right now so you have to consider how you will bring it in and out. What you do NOT want to do is spend an hour outside in the Utah cold, then carry it back into a warm house. This will result in condensation and water spots on your mirror. You either need to bring it back into an unheated garage, or you need to buy something like an Orion padded bag to act as insulation so the scope warms up gradually and doesn’t get water spots. The padded bag doubles as a measure of protection when transporting the scope also. You don’t really need a padded bag for the base too. Who cares if that gets water on it. Just wipe it off with a towel. But you want to protect the tube with the optics.

You will also want a collimation tool, such as a laser collimater.

As for eyepieces, I don’t know what it comes with, but I mostly use 24mm, 13mm, 8mm and 5mm with my 10” reflector. I recently picked up a 10mm too that I expect to get focuser time in this scope. Maybe Saturday. Weather looking hopeful. But basically a 25mm to 5mm spread is good, with maybe 4-5 eyepieces, or a zoom and an eyepiece or two. With your darker skies you could probably get away with a 30mm or so for low power.

Scott
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#4 Quopaz

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Posted 04 December 2020 - 01:16 AM

Hi, that's exactly what I got as my first telescope at the start of this year. You can use it as is and add accessories as you go. First I bought extra eyepieces and barlow lenses. Then I bought the GoTo/Synscan upgrade kit with tracking for taking photos. Also upgraded the focuser to a dual speed (you don't have to but it's better) and changed the finderscope to one with an illuminated reticle (the black cross can be hard to see in the dark). I'm pretty happy with it, pleased I didn't go smaller and sometimes think I should have gone bigger. I also got a sack truck that I strap it to so I can move it around, makes it a lot easier although initially I carried it outside in two bits.


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#5 Kelthebeginner

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Posted 04 December 2020 - 01:45 AM

Thank you for the quick responses guys, I appreciated all the information.

 

Questions for Quopaz, Scott, and tornado:

I actually downloaded Sky Safari Pro yesterday and was playing around with the app just to see what it does. It looks interesting and handy. I downloaded after I read a post here from someone suggesting to another member to get it.

 

I have also read on here, the advice about letting the telescope cool off. What does this mean exactly? (I am a complete beginner)

 

Red beam flashlight - is this that Telrad thing, or is that the red flash light I keep seeing people with on youtube? I imagine this is to minimize light pollution in your immediate area?

 

What are plossl eyepieces for? 

 

I have no clue what collimation is but I will do my homework on that.

 

Quopaz i'm glad you have this exact one. Is it popular on this forum? It would be nice because that way there's a lot of information about it.

 

Thanks again.

 

Edit: I do realize how big it is, I have seen several videos of it on youtube and yeah it's huge. Definitely didn't even know they sold telescopes like that. I thought telescopes for the public were small-ish. But I am okay with the size. There is a dark area near home and we plan to take it there in our truck. And I did see something like a padded bag and thought if that was some I needed so thanks for suggesting that.

 

Edit #2: What about filters? Are those needed? Like moon filters, galaxy filters, etc?


Edited by Kelthebeginner, 04 December 2020 - 01:56 AM.


#6 JohnBear

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Posted 04 December 2020 - 02:19 AM

Scott is absolutely right about lugging a big telescope out and back on a cold night.  You should Try before you Buy - contact your local club to find an owner and gain access to try one.  Also have someone experienced show you how to do collimation. It is easy when someone shows you how to do it right - otherwise you may be in for hours/days/weeks of frustration (probably the biggest reason beginners drop out of astronomy). 

 

I have the 8" SW collapsible Dob and it was by far the right choice for me. I keep it on a dolly for moving it in and out with relative ease. The collapsible OTA has several hidden advantages beside making the OTA smaller for transport - and contrary to popular opinions, the collimation remains remarkably stable.  The collapsible Dobs also have a RACI finder (which is a big "neck saver" and worth an extra $100). Your 10" has the "straight thru" neck breaker.

 

The big, unexpected advantage for me was that it allows me to use my binoviewer with it by allowing me easily to "collapse" the focal length slightly. You'll have to read up on binoviewers to learn why, but binoviewers provide awesome eye popping visual imaging.  

 

That said, the "telescope I use (and enjoy) the most" is my 5" AWB Onesky (a Zhumell Z130 is also recommended)  tabletop dob - which only costs $200.  It is a hard to beat combination of portable convenience and good optics with enough aperture for maximum utility.  Also very easy to collimate! Once you learn to use a 5" table top Dob you will be ready and fully prepared to move up to BIGGER telescopes, but you will keep the table top Dob as your trusty and reliable Grab & Go scope -  and it may continue to get more use overall than the big Yard Cannons.

 

Still, a 10" juggernaut Dob is not a bad choice for beginners with Aperture Fever. 


Edited by JohnBear, 04 December 2020 - 02:26 AM.

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#7 Naja keravnos

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Posted 04 December 2020 - 02:49 AM

A red beam flashlight is a flashlight that uses LEDs so that you can read star charts without affecting your dark-adapted eyes. You need different eyepieces to get different levels of magnification. Plossls are just a better eyepiece design over, say, Kellners.


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#8 therealdmt

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Posted 04 December 2020 - 04:20 AM

Thank you for the quick responses guys, I appreciated all the information.

 

Questions for Quopaz, Scott, and tornado:

 

I have also read on here, the advice about letting the telescope cool off. What does this mean exactly? (I am a complete beginner)

 

Red beam flashlight - is this that Telrad thing, or is that the red flash light I keep seeing people with on youtube? I imagine this is to minimize light pollution in your immediate area?

 

What are plossl eyepieces for? 

 

I have no clue what collimation is but I will do my homework on that.

 

Edit #2: What about filters? Are those needed? Like moon filters, galaxy filters, etc?

I’m not one of those guys, sorry, but hey, I’m "busy" at work and thought I’d jump in with my dos centavos lol.gif

 

Letting the scope cool off (or actively cooling the scope with a fan) is getting the temperature of the mirror and the air inside the tube down from the temperature of where it was stored (such as inside your house) to the same temperature as where you’ll be using it (the outside air temperature). If you store the scope in an unheated area, this could be little or no problem, but if you store it in a warm room, it’s going to take time for the mirror to cool down to the temperature outside. Beyond that, if the temperatures are rapidly dropping such as they sometimes do at night, you can end up chasing the temperature rather than simply cooling to the temperature it is when you get the scope out. 
 

If the air in the tube and/or the mirror temp is hotter than the air temp, you’ll get a distorted effect like looking down a hot highway in the summertime, especially when using high magnifications.

 

A red beam flashlight is just a flashlight with a red light (or a red cover over a white light). Red light let’s you see well enough to read things and handle equipment without ruining your night vision like white light will do. Meanwhile, a Telrad is a completely different thing - it’s a finder attachment to your scope that you can use to help you find things in the sky.

 

Plossl eyepieces are simply a kind of eyepiece (you need an eyepiece to see things through your telescope), and they are known for being decent and affordable. Negatives about Plossls are that their field of view is kind of narrow and that high magnification Plossls require getting your eye right up against the eyepiece — so close that your eyelashes may even be uncomfortably making contact with the eyepiece. Anyway, they’re quite common and often come included with a scope to get you started. You may also find some Plossls to be favorites, but there are other eyepiece designs out there too to explore, perhaps especially ones with longer "eye relief" (distance your eye will be from the eyepiece - very important for glasses wearers!) and wider field of view (important for larger objects and also so that you don’t have to keep repositioning the scope as often at high magnifications)

 

Collimation is basically getting the mirrors in your scope all lined up with each other and the eyepiece so as to show the best possible image. This should be checked periodically, especially after, say, a scope has been banged around during transport.

 

You don’t really need any filters to get started, but, like upgraded eyepieces and other parts, they can be helpful and enjoyable and you may find yourself eventually wanting some. Nothing to stress about right off the bat though, imo


Edited by therealdmt, 04 December 2020 - 12:15 PM.

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#9 SeattleScott

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Posted 04 December 2020 - 12:53 PM

DMT covered it pretty well.

You will need a collimation tool. I suggest a laser collimater. Pretty easy to use, $50-80 usually. You just adjust the secondary until the laser hits the bullseye in the primary, then adjust the primary until the laser hits the bulls eye on the collimater.

There are no doubt YouTube videos.

Scott
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#10 MellonLake

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Posted 04 December 2020 - 06:02 PM

I started with a 10" Dob.  It has shown me so much; 70 galaxies in Virgo (in one night), 6 moons of Saturn, the thousands of stars in M13, the fine filaments of the Veil nebula, the Martian polar cap and albedo features, comets,...   A 10" Dob is a great starter instrument. 

 

I would recommend the following:

1) Collimation Tools...The Farpoint laser/cheshire combo kit.  (If you want to spend less get the Astrosystems Combo tool but ignore the instructions that come with it they are terrible). Note the cheap lasers ($60) are often inaccurate and the cheaper Cheshires/combo tools are too long for an F/4.8 Dob.  Collimation is critical to getting the most out of your Dob, it is easiest with good tools.  If you don't have the $ for the better tools a cheap laser collimator can be aligned (there are lots of threads here on CN about aligning cheap lasers).  

2) A good chair to observe from.  I used a folding stool for a while.  Dobs are best used when seated.  When you sit, you can absorb detail (like watching Jupiter's moon transits which are easily viewed in this telescope).

3) Telrad... Telrads really help you track down objects.  Astronomy software can be set up with the telrad "bullseye" to help you judge distance from bright stars to your object (known as Star Hopping).  

4) Gas and directions to a good dark sky site... no better accessory than very dark skies. 

5) A UHC filter (Like Lumicon, OrionUltraBlock...).  This will help with many faint nebulae (great for the Veil supernova remnant and huge nebula like the North America.

6) Learn about dark adaptation and averted vision.  You need to learn these skills to see the very faint galaxies and nebulae. 

7) An astronomy club.  Nothing better than having someone help you collimate and find objects!!! 

 

All the best

 

Rob 


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#11 GeoNole94

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Posted 04 December 2020 - 07:55 PM

Regarding the OP’s question about accessories, a moon filter is probably essential unless you don’t intend to look at it more than a couple of days either side of a new moon. For my 10” Dob, I plan to get a UHC/nebula filter soon, and perhaps a white light solar filter.


Edited by GeoNole94, 04 December 2020 - 08:24 PM.

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#12 Eddgie

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Posted 05 December 2020 - 09:11 AM

While I am not sure if it is an issue with the 10" Classic Sky-Watcher, I do not at all like the altitude control on the Flextube version of the Sky Watcher. 

 

A Dobsonian can be frustrating to use if it does not move smoothly and easily and on this particular design, the issue is that if the scope is not in near perfect balance, you have to tighten the handles on either side of the telescope. When you do this, you literally squeeze the side panels in until they come into contact with circular friction rings that are in grooves in the sides of the plastic bearings.  Since the sides do not move in exactly parallel, the "pinch" the bearings at the top. This means you have to apply more pressure than would normally be needed if they sides contacted the bearings parallel, which in my version, which uses the same size tube, bearing, and base, this does not happen.

 

Next is the azimuth bearing. This appears to use some type of nylon glide vs PTFE (Teflon) and them makes the movement on the azimuth stiffer than it really should be.

 

Now if your scope is in perfect balance, the azimuth bearings are not that big a deal, but if you decide to later put on a Telrad or use very heavy eyepieces and things like a coma corrector, the scope can get very nose heavy so you wind up cranking down on the side plates and this makes fine, slow motion movement almost impossible. 

 

Bottom line... It is inexpensive but in my opinion, it if a frustrating design to use.   

 

In this case, my recommendation would be to go with the Apertura or the Skyline telescope (same scope, different brands).  This design has (in my opinion) a superior setup.  While it still needs to be balanced, the axles on either side of the scope can be moved on their base places to more finely tune balance. Now the scope has to be taking off of the cradle to do this, but the idea is that you would find a "Neutral" position where you are a bit nose heavy with your heaviest load and a bit tail heavy with your lightest load.

 

These scopes uses ball bearings in altitude and a Lazy Susan type bearing in azimuth.  The altitude friction adjustment is a far better design, and the Lazy Susan azimuth bearings make super smooth and light azimuth motion. In fact, some people have to put in a little path of velcro between the base boards to actually add a bit of friction because motion is so light. 

These scope also come with a better focuser that has a low and high speed.

 

I regret getting the Sky Watcher over the Apertura.  I have spend a lot of time on these issues and while I have improved the scope, it is sill not a scope that moves the way a good dob should. I go back and forth with the thought of just selling it and taking a big loss and moving to the Aperature, but I have already invested in digital setting circles and a WiFi adapter so I can use my phone to aim the scope. 

 

My advice is to go to the reflector forum and ask other owners what they think about the motion of the scope. Again, I own the Flextube version, but from what I can see, the Classic uses the exact same bearing system. 

 

So, in my own opinion, this scope has sub-standard altitude and azimuth handling. It just does not move as smoothly as it should and in my own case, this can be very frustrating to use at high power or when tracking closer to zenith, where stiff motion becomes a very annoying problem. 


Edited by Eddgie, 05 December 2020 - 09:12 AM.

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#13 vdog

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Posted 05 December 2020 - 10:05 AM

A 10" dob is an amazing scope for both planets and DSOs, especially in dark skies. Really, there's only a couple of things you absolutely have to have to get started.

 

One, some type of collimation tool.  Lasers are the most precise, but I wouldn't get one unless you're going to spend enough to get a good one like a Farpoint.  I get by pretty well with just collimation caps, which can be had for less than $10 from Agena Astro.  Heck, you can make one yourself if you have the mind.

 

Two, a plan for storage and easy transport.  As big as it is, a 10" dob can be pretty grab-and-go if you have the setup to make it so.  Storage in an outdoor shed or garage would be ideal so that you can avoid the issues mentioned above and also more easily get it to your observing area and back.  It can be carried in two pieces one at a time, or you could get some type of cart or handtruck to move it back and forth. 

 

Beyond that, you're going to want a million things:  more / better eyepieces, nebula filters, an observing chair, etc., etc.  As far as those go, the only thing I would suggest is to wait until you can buy quality stuff.  Look for bargains (like buying used) but take your time and don't go cheap.


Edited by vdog, 05 December 2020 - 10:40 AM.

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#14 vtornado

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Posted 05 December 2020 - 02:35 PM

I have also read on here, the advice about letting the telescope cool off. What does this mean exactly? (I am a complete beginner)

 As others have said if the mirror is much warmer than the outside

air, this will set up heat currents in the optical tube which will make your high power images fuzzy.  Also while your mirror is cooling

the outside  edges of the mirror cool faster than the middle which will lead to the mirror deviating from a perfect shape. (This is called

thermal astigmatism)  I see it in my 12 inch mirror.

 

Red beam flashlight - is this that Telrad thing, or is that the red flash light I keep seeing people with on youtube?  As others have said a red-beam flashlight is just a flash light with a red filter on it.  I use it all the time to help setup

my equipment.  Occasionally I have to find a dropped item.

 

What are plossl eyepieces for -- plossl is a type of eyepiece (other types are kellners, orthos, erfles, naglers etc)  It refers to the optical design.  The main thing about eyepieces  are the focal length, and the apparent field of view.   Different eyepieces designs have different fields of view for the same focal length. In general it is better to get a wide field of view for example 70 degree vs 50 degree, but realize that making wide field eyepieces is technically  harder than a narrow field.  You either pay for that with a higher cost, or you pay in that the outer 20 degress field of view ( in a 70 vs 50) will not be quite sharp as the inner 50 degrees.

 

 

I have no clue what collimation is but I will do my homework on that.  Collimation is getting all of the optical elements in your

scope aligned to give the sharpest image.  That is eyepiece, secondary and primary.   There are many tools available to do this.

lasers, site tubes, collimation caps etc.  A barlowed laser is easy to use at night.   Collimation caps work fairly well and

are cheap, but are difficult to use at night.

 

 

Edit #2: What about filters? Are those needed? Like moon filters, galaxy filters, etc?

In a 10 inch scope the moon can be painfully bright.  Many folks will say only use high power, or view with a light on ....

but I think a moon filter is only 20.00 just get one.  I do prefer the 25% transmission of the more common 13%.

There is no such thing as a galaxy filter.   There is such a thing as a nebula filter.   If you get one

the first one to get is a UHC type filter.   UHC filters are expensive, and are not miracle makers, but do help.

Think before you buy.

 

VT


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#15 Kelthebeginner

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Posted 05 December 2020 - 05:17 PM

I appreciate all the information everyone has provided. Thanks to all. I will read through them now and research everything you guys have mentioned.


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#16 spaceoddity

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Posted 05 December 2020 - 05:36 PM

My first telescope was a 10"dob(orion xt10i). I have several other scopes now but that is still my most used scope, so I would say it was a good first scope for me. It's a good aperture that will show you the things you are interested in so long as you have realistic expectations and realize that there is a learning curve involved, and there will be other accessories that you will need to purchase to get the most out of your scope. They don't need to be purchased all at once though. The stuff included will be enough to get you started. 


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#17 Mr Dobson

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Posted 05 December 2020 - 10:47 PM

I have this exact scope, assuming it is the Classic 250P.  Balance is not an issue, as the side tensioning handles will allow you to tighten just enough for balance while maintaining manual movement.  At one point, I had a Telrad, RACI, 2X focal extender, and 2 inch EP.  It handled the weight easily without any counterweight, while still allowing me to make manual adjustments.  I have a printed/laminated degree circle on the base and use an angle gauge for locating objects.  Separating the OTA from the base takes seconds; you just unscrew the tensioning handles.  It is easily moved.


Edited by Mr Dobson, 05 December 2020 - 10:48 PM.


#18 Kelthebeginner

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Posted 06 December 2020 - 01:34 AM

My first telescope was a 10"dob(orion xt10i). I have several other scopes now but that is still my most used scope, so I would say it was a good first scope for me. It's a good aperture that will show you the things you are interested in so long as you have realistic expectations and realize that there is a learning curve involved, and there will be other accessories that you will need to purchase to get the most out of your scope. They don't need to be purchased all at once though. The stuff included will be enough to get you started. 

I see you have a 16" truss dobsonian. I looked it up and see it costs over $3k brand new. I'm curious to know why that isn't your most used scope? I saw a video of what I think it's that scope, and man that thing is huge. Is that the reason it's not your most used one?

 

Also a question to everyone: Why are dobsonian scopes cheaper than Schmidt-Cassegrain scopes even though the dobsonians have bigger apertures?

 

Just an example is this one here: Celestron NexStar 8SE 203mm f/10 Schmidt-Cassegrain GoTo Telescope for $1200

 

https://www.bhphotov...03mm.html/specs

 

It has an 8" aperture and sure it has a high focal ratio, but why else does it cost 2x more than a 10" sky-watcher dobsonian? Is it because it's computerized and more mobile? It reminds a lot about desktops vs laptops. Even though a desktop would generally have better specs than a laptop, laptops are more expensive just because of mobility. Is this the case with these two telescopes?



#19 Kelthebeginner

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Posted 06 December 2020 - 01:40 AM

Another question I have is, what is considered good specifications for a telescope for deep space observation? Is it basically bigger = better? Since you can take in more light. Or can you get some good deep space observation with that $1200 dollar schmidt-cass with an 8" aperture?

 

Do people go for telescopes such as that celestron while knowing they can get more power from a bigger scope, but they prefer the mobility even though it comes with a bigger price tag and less power?



#20 Muffin Research

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Posted 06 December 2020 - 03:25 AM

Another question I have is, what is considered good specifications for a telescope for deep space observation? Is it basically bigger = better? Since you can take in more light. Or can you get some good deep space observation with that $1200 dollar schmidt-cass with an 8" aperture?

 

Do people go for telescopes such as that celestron while knowing they can get more power from a bigger scope, but they prefer the mobility even though it comes with a bigger price tag and less power?

Yes, the 8"sct is super compact for an 8" inch telescope which makes it very popular.
They often are coupled with goto motorised mounts which makes it also interesting for beginners. Which is one part what makes it more expensive.

I started off with a C8, very cool scope but a 10" newton will show you more detail and give a sharper image.

And what also makes Schmidt Cassegrain more expensive is the optics, the light takes a completely different route than with a Newton, that's 1 parabolic mirror and a diagonal.. the Schmidt Cassegrain is a corrector lens and two spherical mirrors and then you put in your star diagonal.

The benefit there is that they are folding 2-3 meters of telescope if it was a Newton or Refractor design into a small tube you can carry in one hand.

 

Yes for DSO's bigger is better, or small with wide field is also cool as there are DSO's which are quite large and don't fit in the field of view of bigger scopes with longer focal lengths.

The bigger you go you'll run into different sets of problems to deal with. 

 

I think 10" is dob is superb place to start as that will be very satisfactory for DSO's and Planets. and get a pair of binoculars in the 50 to a 100mm range. That way you can scan the night sky and get an overview of regions and locations and use the Dob to reveal and magnify.


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#21 MellonLake

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Posted 06 December 2020 - 08:13 AM

There are several things that help with viewing DSOs:

 

1) Dark skies.  We measure the darkness of a site using the Bortle Scale (read up on it).  A suburban environment if Borlte 6 or Borlte 7.  In Botle 7, my backyard I can find a few of the very brightest DSOs, they are washed out and very hard to find.  At my Bortle 4 site, I can find all of the Messier Objects in my 10" dob easily.  At my Bortle 1 site, pristine skies with no light pollution, I was able to find nearly 70 galaxies in Virgo alone.  A 10" will show thousands of DSOs in Dark skies.  In the city a 10" will show only a few.  Nothing helps with DSOs more than dark skies.

2) Aperture:  I have compared the effects of aperture in my 10" (254mm), 120mm and 90mm.   In Dark skies I can find all of the Messier objects in all of the telescopes but in the 90mm it is tougher and most galaxies and nebula are faint smudges.  In the 120mm I can easily find all of the Messier objects but they don't show a lot of detail.  In the 10"; Andromeda is larger than my field of view and I can see the extended disc, I can see the spiral arms in galaxies, I see the fine filaments of the Veil nebula, I see the nebulosity of the Pleiades...  Aperture really helps with DSOs.  Remember that light gathering power goes up with square of the radius.  So my 10" is 4 times better at DSOs than my 5".  

3)Dark adaptation/Averted Vision: Learning to dark adapt and stay dark adapted and learning to use averted vision helps.  

4) Learning how to see DSOs... sounds funny but we really need time behind the eyepiece to know what we are looking at.

 

"Another question I have is, what is considered good specifications for a telescope for deep space observation? Is it basically bigger = better? Since you can take in more light. Or can you get some good deep space observation with that $1200 dollar schmidt-cass with an 8" aperture?"

 

"Do people go for telescopes such as that celestron while knowing they can get more power from a bigger scope, but they prefer the mobility even though it comes with a bigger price tag and less power?"

 

Do not think that SCT are somehow more powerful than other telescopes.  They are different.   The ability to see detail in planets and to collect the light of DSOs is really only about having more aperture.  An 8" SCT will not show you more than an 8" Dob/Newtonian and actually will show you less as the SCT has a narrower field of view.  The SCT design is simply so we can get a smaller telescope tube size so it can more easily be stored and transported and mounted,  the only advantage of SCTs over other telescope designs is that they have shorter tubes.  SCTs actually have several disadvantages over other designs (prone to dew, coma, long cooling time, longer focal length/narrower field of view in larger sizers...).  Large SCTs are nice for putting on mounts because the tubes are smaller (I put my 10" Dob tube on an EQ mount, which I don't recommend, and it is huge and moves even in gentle winds).   The biggest drawback of larger SCTs is their narrower field of view.  This limits their ability to view the entirety of large DSOs in one field of view (Andromeda, Pleiades, North America Nebula, Veil Nebula...).  As such, I would personally get a Dob over an SCT.  SCTs are still excellent telescopes and where smaller sizes is needed are a great choice.   


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#22 Eddgie

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Posted 06 December 2020 - 11:36 AM

Another question I have is, what is considered good specifications for a telescope for deep space observation? Is it basically bigger = better? Since you can take in more light. Or can you get some good deep space observation with that $1200 dollar schmidt-cass with an 8" aperture?

 

Do people go for telescopes such as that celestron while knowing they can get more power from a bigger scope, but they prefer the mobility even though it comes with a bigger price tag and less power?

The compact form factor of the Schmidt Cassegrainian and it observing comfort are the only good things about the design. In every other way, an equal size Newtonian will be a better instrument.  It will have higher contrast, go deeper (though only very very very slightly) have a much wider true field, and will generate that true field using far less expensive eyepieces.

 

And my 10" dob is quicker to set up than my C8 was though the tube is of course much heavier, but I can still carry the telescope tube without a great amount of effort.

 

One other point in favor of the SCT is that you may never have to clean the mirror.  With Dobs, you will usually need to clean mirror periodically. That may or may not be a big deal to you.   


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#23 Muffin Research

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Posted 06 December 2020 - 12:55 PM

One other point in favor of the SCT is that you may never have to clean the mirror.  With Dobs, you will usually need to clean mirror periodically. That may or may not be a big deal to you.   

Ah but you still have to clean the corrector once in a while and lots of people tend to be equally squeamish about that. 

 

A good example of a SCT can be satisfying as an observing tool (with a fork mount on a wedge) the range of motion is small, access is easy.. dunno there's something to it.. but the instrument that will throw up more satisfactory images would indeed be an 8" or 10" dob.

When that comes to focus that's a lot crispier, even if it's sharp and you can see a lot of detail there always something soft about the image quality in the SCT, if you then walk over to a refractor or a dob you go "I need one these"


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#24 spaceoddity

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Posted 06 December 2020 - 05:36 PM

I see you have a 16" truss dobsonian. I looked it up and see it costs over $3k brand new. I'm curious to know why that isn't your most used scope? I saw a video of what I think it's that scope, and man that thing is huge. Is that the reason it's not your most used one?

 

Also a question to everyone: Why are dobsonian scopes cheaper than Schmidt-Cassegrain scopes even though the dobsonians have bigger apertures?

 

Just an example is this one here: Celestron NexStar 8SE 203mm f/10 Schmidt-Cassegrain GoTo Telescope for $1200

 

https://www.bhphotov...03mm.html/specs

 

It has an 8" aperture and sure it has a high focal ratio, but why else does it cost 2x more than a 10" sky-watcher dobsonian? Is it because it's computerized and more mobile? It reminds a lot about desktops vs laptops. Even though a desktop would generally have better specs than a laptop, laptops are more expensive just because of mobility. Is this the case with these two telescopes?

Yes, the size and weight and effort to set up is why I don't use the 16" more than the 10. I live in town so I need to travel about 45 minutes to get to my dark observing site. That means the scope has to be carried out of my apartment to my vehicle(suv). I don't regret buying the 16 since I got it used for $1200 and it definitely has a wow factor over my other scopes on many objects. I take it out a couple times a year in the spring and summer.  

 

Dobs are cheaper than SCT's for a couple reasons. The design is a little simpler with just 2 mirrors while the SCT's also have 2 mirrors but also a corrector plate and diagonal(which also has a small mirror). The folded design makes it more costly to produce. The mounts/tripods and electronics that come with SCT's also make them more expensive. The advantage is these mounts have go-to and tracking. You can get that with a dob too but they are more expensive. Most dobs just have a simple alt/az base mount that you move by hand. I prefer the simplicity of the dob mount actually, but go-to and tracking are certainly nice features to a lot of people, as is the shorter tubes of the SCT's. Of course SCT's have their flaws too - as pointed out above. 



#25 csrlice12

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Posted 07 December 2020 - 12:20 PM

10" done are called Goldilocks done for a reason....plenty of aperture, yet still fairly easy to pick up and assemble.  Once you get past 10", easy goes out the window for any scope.


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