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Advice to buy a Dobsonian.

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#1 alexantos

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Posted 05 January 2019 - 05:34 PM

Hello,

 

I'm planning to (finally) buy a Telescope and I was thinking in purchasing this one:

 

Bresser Dobson telescope N 150/750 Messier

 

https://www.bresser....-6-Dobson.html#

https://www.astrosho...er-dob/p,58693#

 

By choosing this one I took in consideration three aspects.
The first one is portability/usability, the second is the aperture, and the third is the cost which has a limit of, more or less, 300€ (340$).

 

I believe that for a beginner like me this would be a good, and fairly easy to use, Telescope.

 

Of all the data, namely, Aperture ratio (f/), Resolving capacity, Limit value (mag), Light gathering capacity and Max. useful magnification, I only have theoretical notions of it, not knowing how it really works in practice, what are the parameters more or less important and what is best to have or to have not.

 

Probably the eyepieces included are of low quality, but I intend later to get better ones.

 

The Red dot finder scope is better or worse than the optical ones?

The Gear rack focuser is better or worse than the Crayford ones?

 

So many questions..., but the main one is this; should I buy this Telescope?

 

If you guys think otherwise, please, and within the 300€ range, tell me what you think is a best buy.

 

Thank you all.

 

Alexandre Santos



#2 Feidb

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Posted 05 January 2019 - 06:23 PM

I often recommend a 6-inch simple Dob for beginners. It's basically the largest tabletop scope you can easily handle and still have enough aperture to see things.

 

It has no extra doodads to get in the way, complicate things and go wrong.

 

It has a parabolic mirror, which is essential for such a short focal ratio. Now, I can't vouch for the quality and since I have no idea where the mirror came from, who knows? More than likely, GSO in China so the likelihood that it's decent should be pretty good.

 

The red dot finder should work okay, though it personally wouldn't be my choice. However, for a beginner, it should work fine. My suggestion is if possible, turn the dot brightness down as far as possible so you don't drown out the background stars. Also, they take a bit of getting used to, especially head position, so practice in the daylight first.

 

As for the eyepieces, you're getting the standard medium and high power Kellners. They're 3-element 40 - 45 degree EPs. Nothing to brag about, but given their simplicity, they should do just fine for starting out, especially the 20(or is it 25)mm.

 

You have enough aperture to pick up ALL of the Messiers, the planets and quite a few of the brighter NGCs. They certainly won't look like the Hubble images, but you'll be able to see these objects.

 

Now, the biggest thing is practice. You need to learn how to point it, how to actually find stuff, and most important, how to actually recognize what you're seeing in the eyepiece. This is sometimes easier said than done.

 

While you aim at something faint, or even something fairly bright, when you look at it, you may not recognize it because of expectations. Also, you'll have to consider sky conditions and light conditions from where you're set up.

 

Portability should not be a big issue as this scope is fairly small and you should be able to wrap it up and transport it in any vehicle. Probably even on a bike.

 

Once you get into the 8-inch class and above, they become a bit more heavy and you need to consider not only weight and size, but also price.

 

Hope this helps.


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#3 sg6

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Posted 05 January 2019 - 06:43 PM

It is what is termed a table top mount, not sure I would entirely agree with the "dobsonian" description since in a way it resembles more a single arm alt/Az mount as used on the 4, 5, 6, 8 SE.

 

At 150/750 it seems big for the type it is.

 

Eyepiece are Kelners, description says "K".

An RDF is not easy to use on one since for an RDF you have to look along the tube and if sat on a surface it will be difficult. Whatever you stand it on will get in the way. And stighting along it with your head laid sideways on the tube is an acquired art.

 

Never like doing this but could you add another €25 ?

But sort of immediately, although it would reduce portability:

https://www.bresser....-Dobsonian.html

 

In honesty I am not a fan of the table top mounts, and at 150mm a Skywatcher 150 dobsonian (f/8) would make a better scope. At f/8 also a bit easier on eyepieces.


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#4 gene 4181

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Posted 05 January 2019 - 06:47 PM

  Yes its a  decent scope  .   Cools quickly  ,  you'll have too collimate it  with a combination  chesire / sight tube tool  .  Hopefully you have  decent skies in Portugal  ,   and the patience and perseverance  to learn the skies / location of the faint stuff  ,      Get yourself a good guide book  ,   Stars and Planets by  Ridpath and Tirion is a good one  or   Skywatching by Levy  .    The hobby is a journey more about you than the scope / scopes    



#5 alexantos

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Posted 05 January 2019 - 06:48 PM

I often recommend a 6-inch simple Dob for beginners. It's basically the largest tabletop scope you can easily handle and still have enough aperture to see things.

 

It has no extra doodads to get in the way, complicate things and go wrong.

 

It has a parabolic mirror, which is essential for such a short focal ratio. Now, I can't vouch for the quality and since I have no idea where the mirror came from, who knows? More than likely, GSO in China so the likelihood that it's decent should be pretty good.

 

The red dot finder should work okay, though it personally wouldn't be my choice. However, for a beginner, it should work fine. My suggestion is if possible, turn the dot brightness down as far as possible so you don't drown out the background stars. Also, they take a bit of getting used to, especially head position, so practice in the daylight first.

 

As for the eyepieces, you're getting the standard medium and high power Kellners. They're 3-element 40 - 45 degree EPs. Nothing to brag about, but given their simplicity, they should do just fine for starting out, especially the 20(or is it 25)mm.

 

You have enough aperture to pick up ALL of the Messiers, the planets and quite a few of the brighter NGCs. They certainly won't look like the Hubble images, but you'll be able to see these objects.

 

Now, the biggest thing is practice. You need to learn how to point it, how to actually find stuff, and most important, how to actually recognize what you're seeing in the eyepiece. This is sometimes easier said than done.

 

While you aim at something faint, or even something fairly bright, when you look at it, you may not recognize it because of expectations. Also, you'll have to consider sky conditions and light conditions from where you're set up.

 

Portability should not be a big issue as this scope is fairly small and you should be able to wrap it up and transport it in any vehicle. Probably even on a bike.

 

Once you get into the 8-inch class and above, they become a bit more heavy and you need to consider not only weight and size, but also price.

 

Hope this helps.

Thanks Feidb

 

About the mirror I have no idea...

It comes with two eyepieces, one 9mm and one 25mm.

 

I was investigating for quite a while about what you would expect to see on a telescope.

I found this website https://www.stelvisi...cope-simulator/ that gave me an idea of what to expect to see, especially about deep sky objects.

 

Appreciate your advices.

 

Take care.


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#6 alexantos

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Posted 05 January 2019 - 07:00 PM

It is what is termed a table top mount, not sure I would entirely agree with the "dobsonian" description since in a way it resembles more a single arm alt/Az mount as used on the 4, 5, 6, 8 SE.

 

At 150/750 it seems big for the type it is.

 

Eyepiece are Kelners, description says "K".

An RDF is not easy to use on one since for an RDF you have to look along the tube and if sat on a surface it will be difficult. Whatever you stand it on will get in the way. And stighting along it with your head laid sideways on the tube is an acquired art.

 

Never like doing this but could you add another €25 ?

But sort of immediately, although it would reduce portability:

https://www.bresser....-Dobsonian.html

 

In honesty I am not a fan of the table top mounts, and at 150mm a Skywatcher 150 dobsonian (f/8) would make a better scope. At f/8 also a bit easier on eyepieces.

Thanks sg6

 

But what do you mean "An RDF is not easy to use"?

And I was assuming that one can rotate the scope on the mount, adjusting the way you look through the eyepiece!

 

Take care.



#7 alexantos

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Posted 05 January 2019 - 07:21 PM

  Yes its a  decent scope  .   Cools quickly  ,  you'll have too collimate it  with a combination  chesire / sight tube tool  .  Hopefully you have  decent skies in Portugal  ,   and the patience and perseverance  to learn the skies / location of the faint stuff  ,      Get yourself a good guide book  ,   Stars and Planets by  Ridpath and Tirion is a good one  or   Skywatching by Levy  .    The hobby is a journey more about you than the scope / scopes    

Thanks gene,

 

I'm using Stellarium for guidance and the web for information, but I will surely buy some books...

 

I have a nice spot near my mom's house where I can watch the skies.

Radiance information
Coordinates: 38° 10′ 42″ N 8° 46′ 23″ W
Value: 0.35
Elevation: 41 meters

 

I use to go there with my binoculars.

 

Take care.

 



#8 alexantos

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Posted 05 January 2019 - 07:45 PM

Sg6 gave another suggestion (he is not a table top mount fan) about another telescope to buy.

 

https://www.bresser....-Dobsonian.html

 

Can you please explain me, apart from portability and aperture, what are the main differences between this one and the one I've chosen?

 

https://www.bresser....r-6-Dobson.html

 

Thanks



#9 DNA7744

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Posted 05 January 2019 - 07:47 PM

Here is a great field of view simulator that I used when deciding to purchase my scope and eyepieces.

 

 https://astronomy.to.../field_of_view/

 

I purchased an 8" Sky-Watcher Collapsible Dobson (was on sale for a great price) and have been very happy!


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#10 alexantos

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Posted 05 January 2019 - 07:53 PM

Here is a great field of view simulator that I used when deciding to purchase my scope and eyepieces.

 

 https://astronomy.to.../field_of_view/

 

I purchased an 8" Sky-Watcher Collapsible Dobson (was on sale for a great price) and have been very happy!

Thanks DNA7744

 

Great simulator...

 

And your Sky-Watcher is easy to transport, assemble?



#11 RKK

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Posted 05 January 2019 - 08:26 PM

Hello,

 

I'm planning to (finally) buy a Telescope and I was thinking in purchasing this one:

 

Bresser Dobson telescope N 150/750 Messier

 

https://www.bresser....-6-Dobson.html#

https://www.astrosho...er-dob/p,58693#

 

By choosing this one I took in consideration three aspects. ...

 

A 6" or 8" is an excellent place to start,  Small enough to move about and take to the Dark simple to use and large enough to supply some great views of the heavens.  I started with a 12" Dob, while it was a great scope it was difficult to move about and didn't get taken along as often as it should have.  I have sold the 12" and moved to a 20" Dob.  If I had started with a 6" I would still have it for a quick grab and go along with the 20" for when time allowed.



#12 DNA7744

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Posted 05 January 2019 - 09:42 PM

Thanks DNA7744

 

Great simulator...

 

And your Sky-Watcher is easy to transport, assemble?

 


Here is the Dobson I purchased and I see it is still on sale (check other sites as well)

 

 https://www.bhphotov..._Telescope.html

 

It was a breeze to assemble...and transport is easy (weighs about 60 lbs) but can be broken down to two pieces for transport.  I had a 6" Solid Tube Dobson...but I love the collapsible...and the 8" gives outstanding views of the moon and DSO's (in my opinion).  I also purchased a Rigel Quickfinder...and that really helps for locating your DSO's. (The Telrad...is great also but too big to fit this scope).  I also purchased a good Barlow (2.5x) and wide view eyepiece (32 mm).  I think this is a great scope...and though non-computerized (my first)...I am finding it gives me the satisfaction of locating DSO's on my own (and with smartphone app).  Here is one of my favorite pics taken with my cellphone....hope to get better at this.  Good luck in your quest!  Lunar New Year red.jpg


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#13 Feidb

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Posted 05 January 2019 - 09:55 PM

Alexandre,

 

An RDF is a red dot finder, which is what's on the 6-inch scope.

 

As others alluded to, a tabletop scope isn't really a Dobsonian and that 8-inch example for around the same price would be a better choice overall. However, if portability is still an issue and you are just a beginner, you have to consider that.

 

The 8-inch would be much more forgiving with those eyepieces.

 

On the other hand, the 8-inch is a solid tube about 1-1/2 meters long. You can't just pack it up in a suitcase. The mount is nothing to stow in a compact bag either. It will also weigh a bit more. However, you'll get more light grasp, better correction on the mirror (most likely), and can use a wider array of eyepieces without edge distortion.

 

As a complete beginner, you have to consider all that, and then the end result if this ends up being just a hobby or turns into a passion. For me, it became a passion way back when I started in 1966 with my first 60mm refractor. I went on to make my first 8-inch mirror. That was completed in 1968 and I haven't looked back since. I built my first 16-inch in 1987, started it in Spain and finished it in Turkey and have been using 16-inch aperture ever since. Visual observing has never been a hobby.

 

On the other hand, if you get out there with whatever instrument, get bored with it, find it isn't for you, you're going to have either a big or little beast to have to sell or give to someone.

 

On the other hand, say you do get the spark, how often can you get out to observe? If it really hits you, it won't matter how cumbersome your scope is. You're going to figure a way to get out.

 

The best advice is easy steps until you figure out if this is for you. Either scope should be within your budget from the looks of the ads. So, the real question is portability.

 

Hope this helps.


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#14 barbie

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Posted 06 January 2019 - 12:08 AM

I have a 6" F8 dobsonian in my arsenal of instruments now becasue it has enough aperture to show enough for a lifetime and because it's portable and easy to transport.  The F8 focal ratio allows simpler, less complex, and thus less expensive eyepieces to be used to get great views!  I am a seasoned observer of 50 years and have found the 6"F8 dobsonian to be most versatile with plenty of aperture, easy to set up telescope to own and use.


Edited by barbie, 06 January 2019 - 12:36 AM.

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#15 SeattleScott

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Posted 06 January 2019 - 12:22 AM

What people are trying to tell you, but maybe not being clear about it, is the first scope you looked at is a tabletop scope, meaning you have to set it on something. Unless you are my 5-year old son. It would be the perfect height for him. But assuming you are a grown adult, the scope would be too short to use without setting it on something. Table, car hood, bar stool, whatever. Of course if it is table or car hood, then whenever you want to look at a different part of the sky, you have to pick up the scope and move around the table or car. One advantage of this design is the short tube means less magnification, meaning wider fields of view are possible to help find targets.

A dobsonian sits on the ground and is high enough for an adult to use, well, somewhat comfortably. Many observers prefer an observing chair for these scopes since the viewing position is often fairly low. Others just keep bending over and contorting themselves to line up targets in a finderscope. Depends on how young you are, or whether tripping over a chair in the dark bothers you.

Personally I have three reflectors and none of them are Dobs. I just picked up a used tabletop one for the kids for dirt cheap used. If nothing else it could give them something to play with that I don’t mind if they break it. My other two are tripod mounted, so they are a more comfortable height for me. This option tends to be a little pricier and doesn’t work well over about 10” of aperture. But for a midsize reflector it can be an appealing option because you can have a short, wide field scope and have it any height you want. Here in the states you could get a 6” tripod mounted reflector for $400 or so, plus a bit more for eyepieces. But for the same price you can get an 8” Dob, with a couple eyepieces, so most people do that.

Interesting, I would think an RDF would be easier for a beginner than a magnifying finder that reverses the view, and shows many more stars than one can see with their eyes, making it hard to tell where they are looking. I started out greatly preferring RDF and still prefer them for wide field scopes, or suburban observing. Now I can use any finder pretty effectively, and tend to prefer optical finders for narrow FOV scopes like Cassegrains, or at dark sites. In the city, the 50mm optical finders have a lot of trouble cutting through the light pollution so better off with RDF. Yes, RDF has a learning curve, but less so than optical finders in my opinion. Maybe I would feel differently if I lived under dark skies? Regardless the finderscope is easy to change so I generally wouldn’t make a decision based on the finderscope. But if there are two similar models with different finders, I suppose it could be the determining factor.

Scott

Edited by SeattleScott, 06 January 2019 - 12:23 AM.


#16 Space Station #5

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Posted 06 January 2019 - 12:36 AM

 

I was investigating for quite a while about what you would expect to see on a telescope.

I found this website https://www.stelvisi...cope-simulator/ that gave me an idea of what to expect to see, especially about deep sky objects.

 

 

I had never seen this www , thanks for posting that !   Been doing some research on what to buy as first scope.  I like that, as far as the simulations go.


Edited by Space Station #5, 06 January 2019 - 12:39 AM.


#17 Starkid2u

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Posted 06 January 2019 - 12:36 AM

Sg6 gave another suggestion (he is not a table top mount fan) about another telescope to buy.

 

https://www.bresser....-Dobsonian.html

 

Can you please explain me, apart from portability and aperture, what are the main differences between this one and the one I've chosen?

 

https://www.bresser....r-6-Dobson.html

 

Thanks

Working from a tabletop can be a pain in the neck if you try to leave your yard. This scope will be able to go wherever you do. All other things are equal in terms of collimation and care. A plus? 2 more inches of aperture is good! An 8" scope is highly recommended here at CN. By me and a thousand others. I prefer a straight-through finder to an RDF, but that's a personal choice, gained by experience. Good luck and clear skies for you!

 

STARKID2U



#18 Space Station #5

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Posted 06 January 2019 - 12:54 AM

 I'm leaning towards an Apertura AD10 , adding a Telrad and possibly a Hotech laser collimator later on, but,   I'm still researching things for now , not in any hurry to make a buy.  Doin a lot of reading on here !!  Always looking for new www's to check out. 



#19 Recretos

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Posted 06 January 2019 - 05:30 AM

Hey Alex, I see you are looking at the Astroshop, which means you must be from Europe. :)

I bought my Skywatcher 150p dobson there. And that is the scope I also recommend over the Bresser 150mm, the one you linked in your first post.

https://www.astrosho...sic-dob/p,15559

Despite both having 150mm (6") aperture, there are some optical differences, in which the Skywatcher (SW) is better in every way.

The Bresser scope has a focal ratio of f/5. Now compared to the f/8 from the SW, that means that the SW can better handle cheaper eyepieces. But thats is not all. The f/5 ratio also needs a bigger secondary mirror.
The Bresser has a secondary mirror of 55mm diameter.
The SW has a 34,5mm secondary diameter. That is quite the difference.

Doing simple math, if we calculate the central obstruction of both scopes, the SW dobson actually has 10%! more light gathering area than the Bresser, despite having the same aperture. That is because the larger secondary on Bresser blocks more of the incoming light, together with relatively thick secondary mirror supports, which also has a greater negative impact on the contrast of the image.
The light gathering power compared to the human eye (7mm pupil) is x395 for the Bresser, and x435 for the SW 150p dob, which is quite the difference. The resolving capacity is also better (lower the better) on the SW dob (0.77) compared to the Bresser (0.92)

Now to be realistic, will you see that 10% difference in better light gathering? I dont know. An experienced observer would very likely see a difference in brightness, and in contrast. As a beginner perhaps not as much or not even at all, but being on a budget, you would want the best optical performance you can get for the money.

About the money. The Bresser is 300€, and it comes with two EPs, of which the 9mm is said to be of very low quality. Its only what Ive heard, I dont know personally how good it is.

The SW 150p dob starts at 275€ on astroshop.eu and also comes with two eyepieces, of which the 25mm is very good and my regular eyepiece, and the 10mm is quite ok, and gave wow moments on Jupiter and Saturn in good seeing conditions.

I can guide you on how to get that SW 150 dobson for perhaps as low as 235€! like I did. Send me a private message if you are interested.
That would mean you would have money to spend on a good low power (35mm) eyepiece, and a 2x Barlow (I can also send you a link for quality one for 15€ that I have tested and works perfect).

Send me a private message if you are interested. I can try to help you out on a better deal, since I was in a tight budget myself, so I researched everything into oblivion. :)

Edited by Recretos, 06 January 2019 - 05:43 AM.

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#20 penguinx64

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Posted 06 January 2019 - 08:01 AM

I have a similar Celestron C6-N OTA with a 6 inch mirror and a 750mm focal length.  It works great for me.  I get some nice views at 192x with a 3.9mm eyepiece and a 0.78mm exit pupil.  I don't go much higher than that because of local seeing conditions.  Figure on a 1mm exit pupil at 150x, a 2mm exit pupil at 75x and a 3mm exit pupil at 50x.  At f/5 it's a little more forgiving on eyepieces than my f/4 4.5 inch reflector.  With a 1.25 inch 32mm Plossl, you would get a maximum 2.2 degree true field of view at 23x.  I think this scope is a good choice. 

 

One comment is that the description says 'Compact telescope also for traveling'.  The tube length of 685mm and 180mm diameter isn't what I'd call 'Compact'.  I guess maybe it's more compact than an 8 inch Dobsonian.  It's gonna be bigger than it looks in the picture.  Also the total weight is 9.2kg, or about 20 lbs.  My scope and mount weigh about the same.  Carrying it for short distances is ok, but mine gets heavy carrying it for more than a minute or so.  But again, that's half the total weight of an 8 inch Dob and mount, plus it would fit in a car much easier.  It's definitely too big for an airline carry on bag though.


Edited by penguinx64, 06 January 2019 - 10:09 AM.


#21 Bjorg63

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Posted 06 January 2019 - 09:40 AM

Welcome to CN. Plenty of good advice here for you to consider. I've never been a fan of tabletop setups. I find them cumbersome and difficult to view through above 45 degrees. Much of my viewing is above 45 degrees and towards zenith.

 

The Skywatcher 150 DOB listed by Recretos would be significantly better, and a great price. The dobsonian mount is functionally better than a tabletop mount. This scope is still easily transported, lightweight. It has better starter eyepieces and allows for upgrades to the scope, eyepieces and other accessories.

 

Get the SkySafari app for your phone or tablet. Best accessory I have.

 

I wish you well in your decision and clear skies.



#22 DNA7744

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Posted 06 January 2019 - 12:02 PM

Welcome to CN. Plenty of good advice here for you to consider. I've never been a fan of tabletop setups. I find them cumbersome and difficult to view through above 45 degrees. Much of my viewing is above 45 degrees and towards zenith.

 

The Skywatcher 150 DOB listed by Recretos would be significantly better, and a great price. The dobsonian mount is functionally better than a tabletop mount. This scope is still easily transported, lightweight. It has better starter eyepieces and allows for upgrades to the scope, eyepieces and other accessories.

 

Get the SkySafari app for your phone or tablet. Best accessory I have.

 

I wish you well in your decision and clear skies.

 

I use the Sky Safari and the Sky View apps on my phone!  Both help significantly!  Technology is great!



#23 alexantos

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Posted 06 January 2019 - 03:09 PM

Alexandre,

 

An RDF is a red dot finder, which is what's on the 6-inch scope.

 

As others alluded to, a tabletop scope isn't really a Dobsonian and that 8-inch example for around the same price would be a better choice overall. However, if portability is still an issue and you are just a beginner, you have to consider that.

 

The 8-inch would be much more forgiving with those eyepieces.

 

On the other hand, the 8-inch is a solid tube about 1-1/2 meters long. You can't just pack it up in a suitcase. The mount is nothing to stow in a compact bag either. It will also weigh a bit more. However, you'll get more light grasp, better correction on the mirror (most likely), and can use a wider array of eyepieces without edge distortion.

 

As a complete beginner, you have to consider all that, and then the end result if this ends up being just a hobby or turns into a passion. For me, it became a passion way back when I started in 1966 with my first 60mm refractor. I went on to make my first 8-inch mirror. That was completed in 1968 and I haven't looked back since. I built my first 16-inch in 1987, started it in Spain and finished it in Turkey and have been using 16-inch aperture ever since. Visual observing has never been a hobby.

 

On the other hand, if you get out there with whatever instrument, get bored with it, find it isn't for you, you're going to have either a big or little beast to have to sell or give to someone.

 

On the other hand, say you do get the spark, how often can you get out to observe? If it really hits you, it won't matter how cumbersome your scope is. You're going to figure a way to get out.

 

The best advice is easy steps until you figure out if this is for you. Either scope should be within your budget from the looks of the ads. So, the real question is portability.

 

Hope this helps.

Hi Feidb,

 

What can I say, I just don't know if it will become a passion. Right now surely it will be a hobby.

I'm on my fifties now (I was 1 year old when you started), and looks like I've finally found the time to pursue my love for astronomy.

One thing I can say to you, I'll never be bored to look at the skies...

Thank you for your experienced advices of great help to me.

Take care.


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#24 alexantos

alexantos

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Posted 06 January 2019 - 03:16 PM

I have a 6" F8 dobsonian in my arsenal of instruments now becasue it has enough aperture to show enough for a lifetime and because it's portable and easy to transport.  The F8 focal ratio allows simpler, less complex, and thus less expensive eyepieces to be used to get great views!  I am a seasoned observer of 50 years and have found the 6"F8 dobsonian to be most versatile with plenty of aperture, easy to set up telescope to own and use.

Hi barbie.

 

Can you tell me the major differences between that 6" F8 and the 8" F6 dobsonian that sg6 refereed on a previous post?

 

I mean, one is heavier than the other of course, but the viewing quality is huge in comparison?

 

Thanks



#25 alexantos

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Posted 06 January 2019 - 03:31 PM

(...) Interesting, I would think an RDF would be easier for a beginner than a magnifying finder that reverses the view, and shows many more stars than one can see with their eyes, making it hard to tell where they are looking. I started out greatly preferring RDF and still prefer them for wide field scopes, or suburban observing. Now I can use any finder pretty effectively, and tend to prefer optical finders for narrow FOV scopes like Cassegrains, or at dark sites. In the city, the 50mm optical finders have a lot of trouble cutting through the light pollution so better off with RDF. Yes, RDF has a learning curve, but less so than optical finders in my opinion. Maybe I would feel differently if I lived under dark skies? Regardless the finderscope is easy to change so I generally wouldn’t make a decision based on the finderscope. But if there are two similar models with different finders, I suppose it could be the determining factor.

Scott

Hi SeattleScott,

 

So, and based in what you say, the advice is to use an RDF if you are a beginner like me.

Assuming that I follow the advice from sg6 on a previous post, and buy instead the BRESSER Messier 8" Dobsonian with RDF, you think that is a better purchase than perhaps the Skywatcher Dobson 8" with 9x50 finderscope?

 

Thank you




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