Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Advice on Beginner telescope (Dobsonion 8 inch vs 127 mm cassegrain)

  • Please log in to reply
20 replies to this topic

#1 vkpradeep

vkpradeep

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 27 Dec 2020

Posted 23 January 2021 - 07:04 PM

Hi - I am new to Astronomy and was planning to get a good beginner telescope for viewing planets & deep sky objects. After some research, I have landed on couple of options:

 

  1. Apertura AD8 Dobsoinion : https://www.highpoin...n-telescope-ad8
  2. Celestron Nexstar 127 cassegrain : https://www.highpoin...telescope-22097

 

I have heard that dobsonion with 8 inch reflector has better light gathering capability, however celestron has a computerrised goto mount and larger focal length.

 

Just wondering how the cassegrain compares to the Dobsonion.  I have tried "how" the views may look using stellarium and could not tell much difference. 

 

I wanted to get some advice from the forum / members who have experience using either of these scopes. 

 

Thanks in advance for your comments / feedback.

 

Pradeep



#2 Maritime

Maritime

    Viking 1

  • *****
  • Posts: 615
  • Joined: 19 Aug 2020

Posted 23 January 2021 - 07:22 PM

I can’t compare them BUT the 127slt, of my four scopes, is a favorite. The mount is very accurate and the optics first rate BUT the tripod is a shaky nightmare. I found a used 4/5se tripod, which is rock stable, and only paid $60. The tube never needs collimating and the views are beautiful. Keep in mind it is a right hand mount, which is a minor issue if you use another mount, but I love and highly recommend it. 



#3 SeattleScott

SeattleScott

    Voyager 1

  • *****
  • Posts: 10,698
  • Joined: 14 Oct 2011

Posted 23 January 2021 - 07:31 PM

Views through the Dob will be about 150% brighter at same magnification. Also capable of wider views to help hunt stuff down, but no goto. I don’t know that GoTo is all that valuable below 6” aperture as you just don’t have much light grasp for DSO, which is kind of the point of GoTo.

Scott

#4 Sheol

Sheol

    Viking 1

  • -----
  • Posts: 824
  • Joined: 20 Mar 2010

Posted 23 January 2021 - 07:39 PM

                                Your 2nd choice is more of a Planetary viewing scope. I'd go with the Dob. But I might, just possibly MIGHT be slightly in good opinion of Dobs in general, seeing as how I own an 8 & 12 inch model of 1 each. Just saying...

 

                                  Clear Skies,

                                      Matt.


  • spaceoddity likes this

#5 Maritime

Maritime

    Viking 1

  • *****
  • Posts: 615
  • Joined: 19 Aug 2020

Posted 23 January 2021 - 07:39 PM

Hmm. I have no difficulty observing star clusters, nebula and some galaxies. The go to is VERY accurate, and tracks stars, planets or whatever for longer than I care to observe the object. Without go to, I probably wouldn’t bother observing. I own and use a 4se, 6se, 127slt and an 8 inch edgehd. Each is go to, and I have two starsense cameras with programming for each. I live in the city of Seattle, and there is no time to waste with manual alignments or searches. 


  • TJF stars likes this

#6 Jethro7

Jethro7

    Surveyor 1

  • *****
  • Posts: 1,654
  • Joined: 17 Dec 2018
  • Loc: N.W. Florida

Posted 23 January 2021 - 07:41 PM

Hello Pradeep,

Aperure wins out for DSO's. Dobs are easy to learn on, with their very simple and have a very stable base. I used to really like GoTo mounts until I found the charm of manual Alt Az mounts. With this style of mount I have learned to navigate the night skies and haven't any use really, for the GoTo function anymore. You can learn how to do this your self. And you know what there is somthing very satisfying finding your targets yourself.  A 8" Dob and these two books will get you going in the right direction. If you buy the Dob and later get a chance to view with the other scope you will know instantly that you made the right decision. And that's statement comes from a refractor Guy "Me" I prefer the views through a refractor for Lunar, planetary,  Splitting double stars, these are the realm of refractors. Many DSO's are out of reach of my refractors and that is where my Dob comes in to play. A Dob is no slouch for viewing the Moon and planets either. They are the best all around scope for viewing you can own. I dont even use my C8 Edge HD anymore after I bought a Dob.

 

" NightWatch" Revised Fourth Edition by Terrence Dickerson. Best beginning Astronomy Primer in print.

 

" Turn Left at Orion" by Guy Consolmagno and Dan M. Davis. One if the best guides to the night skies that you can buy.  You will learn how to navigate the night skies very quick on your own.

 

HAPPY SKIES AND KEEP LOOKING UP Jethro

 

P.S. a pair of binoculars really comes in handy.


Edited by Jethro7, 23 January 2021 - 09:37 PM.

  • Jim Haley, spaceoddity and mooresaw like this

#7 byi

byi

    Explorer 1

  • *****
  • Posts: 76
  • Joined: 07 Aug 2019
  • Loc: Princeton, NJ

Posted 23 January 2021 - 08:16 PM

I have never used a goto; I'm cheap and have found I enjoy the process of star hopping and tracking anyway. I prefer minimal fussing with and debugging computers - I do enough of that at work. I can imagine it can be quite convenient though.

So, with the above bias stated, I have had an AD8 for a year and a half (effectively my first scope) and recently got an AD12. I can vouch that the AD8 is a fun, easy scope.

Concerning aperture and focal length, the views will be noticeably narrower and dimmer with the sct. For the former, you might want to invest in one or two eyepieces with high focal length and/or wide apparent field of view in order to fit the handful of relatively large DSOs in frame (Andromeda, Pleiades, etc although I don't know how much of Andromeda you could see anyway).

Best of luck with your choosing.
  • spaceoddity, vtornado, Jethro7 and 1 other like this

#8 izar187

izar187

    Aurora

  • *****
  • Posts: 4,527
  • Joined: 02 Sep 2006
  • Loc: 43N

Posted 23 January 2021 - 09:09 PM

Welcome aboard!

 

My vote would be the 8" as well.

From my experiences with 5" vs 8" of aperture.


  • Jethro7 likes this

#9 sevenofnine

sevenofnine

    Messenger

  • -----
  • Posts: 445
  • Joined: 16 Apr 2016
  • Loc: Santa Rosa, California

Posted 23 January 2021 - 10:33 PM

As you can see from my signature, I have both types. The Dob is better for DSO's but the Mak is surprisingly good on the brighter ones especially with better eyepieces. Lots easier to find objects with go-to as well. They are dramatically different in size and weight. The Dob can be more than you want to deal with some nights. You can tuck the Mak under one arm. If you think solar system objects and bright DSO's (like the Orion Nebula) are the most interesting then get the Mak on a go-to mount. If DSO's (like the Messier Objects) are your main interest then get the Dob. Each scope has it's strengths and weaknesses. That's why I have them both. Good luck with your decision! waytogo.gif


Edited by sevenofnine, 23 January 2021 - 10:34 PM.

  • spaceoddity, Bigal1817 and byi like this

#10 Moosi

Moosi

    Lift Off

  • -----
  • Posts: 6
  • Joined: 14 Jan 2021

Posted 24 January 2021 - 12:31 AM

Hi Pradeep,
I took the plung as well, and just ordered a C90 Mak with a stable alt az mount (no goto, ordered "Turn Left at Orion" since I want to wander around). It's intended for planetary and moon watch.
Did some research and the Aperatura 8" is highly recommended, has fine focus etc.
I'm from Israel and can join a local astronomy club, which lends out gear, including 8" Dobsonian so that's covered.
My intention is to get the hang of things then see if I'm going the visual route (=aperture fever Dobsonian) or astrophotography (=divorce).
I'm still trying to figure out the two most important issues - how to deal with mosquitoes and what to drink.
Have fun!

Sent from my SM-G955F using Tapatalk

#11 SeattleScott

SeattleScott

    Voyager 1

  • *****
  • Posts: 10,698
  • Joined: 14 Oct 2011

Posted 24 January 2021 - 02:15 AM

Hmm. I have no difficulty observing star clusters, nebula and some galaxies. The go to is VERY accurate, and tracks stars, planets or whatever for longer than I care to observe the object. Without go to, I probably wouldn’t bother observing. I own and use a 4se, 6se, 127slt and an 8 inch edgehd. Each is go to, and I have two starsense cameras with programming for each. I live in the city of Seattle, and there is no time to waste with manual alignments or searches.

Certainly GoTo can work in and around the city, but under 6” aperture you kind of have to know your DSO and which ones will actually show up. A lot of beginners will be in Bortle 7 skies and try to plow through the galaxies in the Virgo Cluster or Big Dipper and get frustrated because they can’t see anything. I mean around Seattle you got what, maybe half a dozen galaxies to choose from with 5” aperture? So maybe 2-3 at any given time of year? As long as you know which ones they are, that’s fine. But a beginner could get frustrated trying to go to all these galaxies, or maybe nebulae that just aren’t going to show well (if at all) in light pollution with 5” aperture. But star clusters do tend to show better. Those are mostly what I view in town.

Scott

#12 izar187

izar187

    Aurora

  • *****
  • Posts: 4,527
  • Joined: 02 Sep 2006
  • Loc: 43N

Posted 24 January 2021 - 04:29 AM

 Each scope has it's strengths and weaknesses. That's why I have them both. Good luck with your decision! waytogo.gif

What!?!?

Both?

Are you sure that's allowed?

 

Hi Pradeep,
I took the plung as well, and just ordered a C90 Mak with a stable alt az mount (no goto, ordered "Turn Left at Orion" since I want to wander around). It's intended for planetary and moon watch.
Did some research and the Aperatura 8" is highly recommended, has fine focus etc.
I'm from Israel and can join a local astronomy club, which lends out gear, including 8" Dobsonian so that's covered.
My intention is to get the hang of things then see if I'm going the visual route (=aperture fever Dobsonian) or astrophotography (=divorce).
I'm still trying to figure out the two most important issues - how to deal with mosquitoes and what to drink.
Have fun!

Sent from my SM-G955F using Tapatalk

Cover up with long sleeves, pants and socks.

Treat your clothes with a little repellent, and dampen a hat with it.

Use Deep Woods Off or equivalent, on exposed neck, face and back of hands.

Be very well hydrated, so your retina's are getting lots of oxygen.


  • Moosi likes this

#13 Spile

Spile

    Explorer 1

  • -----
  • Posts: 67
  • Joined: 27 Dec 2020
  • Loc: Bromsgrove, Worcestershire, UK

Posted 24 January 2021 - 05:51 PM

I have an 8” Dobsonian and I am very happy with the build quality and optics. It is a Skywatcher 200P.



#14 Bigal1817

Bigal1817

    Vostok 1

  • -----
  • Posts: 102
  • Joined: 04 Jan 2019
  • Loc: Colorado

Posted 25 January 2021 - 03:09 PM

The 8" will show you more.  That said, I find happy telescope owners can successfully answer the following questions prior to purchase:

1.) where will you use the telescope?

2.) where will you store the telescope?

3.) how will you get the telescope from storage to destination?

 

If you can answer all three questions for both scopes, go for the 8".  If you can only answer all three for one telescope, you might want to buy that one.


  • Asbytec and spaceoddity like this

#15 midwestastronomer

midwestastronomer

    Explorer 1

  • -----
  • Posts: 74
  • Joined: 04 Feb 2018

Posted 25 January 2021 - 03:31 PM

Hard no to the 127 Maksutov here. It's nice if you're only doing planets, double stars and bright globs, but the long focal length is no good for open clusters and nebulae.(in 5 inches you can barely make out galaxies other than M31)  Maksutovs are a specialty telescope as they have a very narrow field of view. You want great views of planets and globs? Maks are for you. Otherwise, choose another scope. I also warn newbies on going too big in aperture too fast. I jumped from a 5 inch Mak to a 12 inch dob and I didn't appreciate what I had. My suggestion for a first scope is always either a 4 or 5 inch long focus refractor(achromat) or a 6 inch reflector. If you get the achromat be sure to grab a light yellow filter as it will do the job for removing fringing on Jupiter and Saturn. 

 

Cassegrains are for experienced observers that know exactly what they want in their scope. This is my opinion. 


Edited by midwestastronomer, 25 January 2021 - 03:34 PM.


#16 vtornado

vtornado

    Gemini

  • *****
  • Posts: 3,460
  • Joined: 22 Jan 2016
  • Loc: Northern Illinois

Posted 25 January 2021 - 06:09 PM

A long focal length doesn't offer large advantages.

 

In the days of yore, with traditional eyepiece designs the long focal length allowed the use of longer focal length eyepieces

to reach equivalent magnifications over a short focal length design.   Today modern eyepiece designs

can offer a short focal length with a wide field of view and long eye relief.

 

The difference in focal length between an 8 inch dob (1200) and a 127 MCT (1500) is not that much.

 

Here are some of the considerations between the scopes you listed.

If the 8 inch dob has a two inch focuser it can reach a true field of view of 2.25 degrees. The MCT will be limited

to around 1 degree.

 

The MCT since it is on a goto mount , it will be able to find and track objects.    This can be a big help in light pollution.

Finding dim targets is hard.   Sometimes no guide stars are available for star hopping.

However goto is not magic.  There is a learning process in setting up the goto.   There is an alignment procedure that must be done each time the scope is used.

 

The SLT mount cannot be used manually,  you always have to use the hand box to move scope.  It takes batteries.

You will probably have to buy some larger high capacity battery if you want a long viewing time especially if it is cold.

If you have no batteries you have a very pretty paper weight.

 

Even though much smaller than the dob, you will probably find yourself making two trips to setup the MCT too.

The tripod  and scope is a bit awkward to carry.  I once had a telescope pop out of the vixen saddle, I don't carry two as

a unit.  

 

MCTs are susceptible to dew and frost.  if  you live in a humid climate you made need a dew shield or a dew heater.

 

The dob will have to be collimated every once in awhile.  This is an easy process but once again takes learning to 

do it well and accurately.  The MCT if handled carefully will never need collimation.

 

The dob has a lot more light gathering power and resolution.   Just about every target will be better in it.


  • spaceoddity likes this

#17 Jim Haley

Jim Haley

    Apollo

  • -----
  • Posts: 1,022
  • Joined: 04 Jul 2007
  • Loc: SugarLand, TX

Posted 25 January 2021 - 06:42 PM

The night sky is "dark".  Planets and the moon are relatively bright.  Everything else is dim to very dim.  5^2 = 25   8^2 = 64.  The 8" will collect about 2.5 times as much light as the 5".    I would start with the 8" dob.  It does well on all objects.  Only after a few years observing would I  consider the Mak or a refractor ( as they will be fantastic on the brightest objects) or possibly a bigger dob (better on the dimmer objects).  


Edited by Jim Haley, 25 January 2021 - 06:46 PM.

  • spaceoddity likes this

#18 vkpradeep

vkpradeep

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 27 Dec 2020

Posted 30 January 2021 - 09:55 AM

Thanks for all the feedback. I have ordered 8" dob and already got "Turn left at Orion" book!  Cant wait for the scope :)


  • izar187, TX4812, byi and 1 other like this

#19 Echolight

Echolight

    Surveyor 1

  • *****
  • Posts: 1,881
  • Joined: 01 May 2020
  • Loc: Texas

Posted 30 January 2021 - 11:14 AM

                                Your 2nd choice is more of a Planetary viewing scope. I'd go with the Dob. But I might, just possibly MIGHT be slightly in good opinion of Dobs in general, seeing as how I own an 8 & 12 inch model of 1 each. Just saying...

 

                                  Clear Skies,

                                      Matt.

But didn't it take you about 6 months just to get those dobs put together and collimated?lol.gif


Edited by Echolight, 30 January 2021 - 11:17 AM.


#20 mooresaw

mooresaw

    Explorer 1

  • -----
  • Posts: 53
  • Joined: 01 Feb 2021

Posted 05 February 2021 - 01:52 PM

Hi - I am new to Astronomy and was planning to get a good beginner telescope for viewing planets & deep sky objects. After some research, I have landed on couple of options:

 

  1. Apertura AD8 Dobsoinion : https://www.highpoin...n-telescope-ad8
  2. Celestron Nexstar 127 cassegrain : https://www.highpoin...telescope-22097

 

I have heard that dobsonion with 8 inch reflector has better light gathering capability, however celestron has a computerrised goto mount and larger focal length.

 

Just wondering how the cassegrain compares to the Dobsonion.  I have tried "how" the views may look using stellarium and could not tell much difference. 

 

I wanted to get some advice from the forum / members who have experience using either of these scopes. 

 

Thanks in advance for your comments / feedback.

 

Pradeep

Never used an 8" dob...I have a 4.5" Dob and a 9.25" SCT

 

  • The Dob was very easy to use I was viewing within an hour of opening the box. I got to see Venus, Mars, Saturn and Jupiter + 20-30 Deep Sky objects in the first month or two with it.
  • My friend bought an Orion second hand 8" Dob and quickly re-sold it when he realized it was massive and not something you simply pick up and go with easily...its somewhat large
  • The SCT has a GoTo scope which gives you 40,000 objects to view which is crazy cool....BUT
  • It took 3 sessions of playing around with the mount to learn how to set it up, align the mount, polar align the mount etc. 
  • Learning curve with an SCT is higher but it can be broken down easier and moved about with a few trips vs one massive Dob. 

How do they compare in terms of what you see?

 

An 8" Cassegrains is likely to have a longer focal length than an 8" Dob. That meanss you get a bigger magnification but sacrifice the field of view. For example with my cassegrain I can't look at the Pleiades as a whole, its too magnified I can see specific stars but for a wider field of view I have to use the Dob. Both scopes will gather a lot of light. The Cassegrain will track objects and excel with planetary. The dob will be easier to use and give you wider fields of view.

 

The Dob will be very difficult to do imaging with but SCTs are not easy either so I'm told...

 

If equal Apeture It might depend on what you want to use it for to decide....if its a 5" vs 8" I take the 8" for the Aperture. At 5" I drop $300 on a small Dob and learn to do stuff manually the Go-To will not be worth the hassle for what you get imho.


Edited by mooresaw, 05 February 2021 - 01:58 PM.


#21 mooresaw

mooresaw

    Explorer 1

  • -----
  • Posts: 53
  • Joined: 01 Feb 2021

Posted 05 February 2021 - 01:54 PM

Hmm. I have no difficulty observing star clusters, nebula and some galaxies. The go to is VERY accurate, and tracks stars, planets or whatever for longer than I care to observe the object. Without go to, I probably wouldn’t bother observing. I own and use a 4se, 6se, 127slt and an 8 inch edgehd. Each is go to, and I have two starsense cameras with programming for each. I live in the city of Seattle, and there is no time to waste with manual alignments or searches. 

The fun is the hunt!!! I enjoyed star hopping to find the Messier objects but it gets very frustrating when light pollution means you can't see the stars! More than a few nights I felt I was "On something" but couldn't see it.....the Eagle nebula for example was notoriously hard to find in my skies.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics