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Praseodyymi

Selecting the first telescope

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Hey all, I know there are already lot of posts regarding the selection of first telescope, but I hope you still could advice me a bit further.

Few things about what I am planning to do with the telescope. So I am not interested in photography, I hope to view also deep sky objects and the place I will be mostly (I live in Finland) viewing will located in a countryside (not much light pollution). Telescope, however, should fit into a normal car (should not take the whole backseat though), and I hope I would be able to carry it on my own (I am about 160cm tall, female). My maximum budget is around 1000 euros (less naturally better).

At this point, after numerous internet research, I would select the Sky-Wacher Skyliner-250 Flextube (DOB 10" Collapsible, http://skywatcher.com/product/bk-dob-10-collapsible/ ), which would cost me 790 here in Finland (including shipping, 2 oculars etc.).

So, what do you think? Mainly I am wondering if it is going to be too big to manage alone (won't be alone most of the time, but just in case) and as a "manual" telescope (there is the much more expensive version with synscan goto, 1430 euros) is it difficult to keep objects in the "visual field" with higher magnifications as there is no automated tracking?

Hope to get faster answers here as similar forum here in Finland is not that active.

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Hi and welcome to SGL.

Don't worry about tracking, manual dobs are quite usable even on high magnifications used for planetary viewing.

Dob is excellent choice, but I think that 10" will be a bit too much for you to handle regularly. OTA (optical tube assembly - or main part of the telescope that you use to view) for this telescope is almost 20kg in weight, while base is 25kg in weight. These two parts are easily assembled / disassembled so you will carry each one separately. It is still quite a bit of weight and bulk in each.

You might want to look at 8" version as it is considerably lighter - about 10kg for OTA and 16kg for base (about two times lighter than 10"), and you won't be loosing much of light gathering power.

I have solid tube 8" Skywatcher and it is quite manageable. It will fit even small car - base in the trunk and OTA goes on back seat, but it does take much of the space there as it is about 1.2m long. I did travel in 3 person arrangement with the scope in the smallish car, with person sitting in the back needing to hold a piece of OTA in their lap, so not quite comfortable, but manageable. Collapsible 8" version might fit on single seat when collapsed (not sure about that, but I guess it could).

If you have not done that already - it would be worth looking at some videos on youtube of said scopes - both 8" and 10" to see how large they are compared to an average person. Most telescopes look smaller in the images than in real life, so seeing one next to people puts things in perspective.

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vlaiv answered exactly what I would have answered. Since your scope will be f/5 or f/6 you will need a widefield 2-inch eyepiece in the 20mm to 30mm range. To enjoy the largest view your future scope will provide its specs have to be around 30mm for a 68°, 25mm for an 82°, or 20mm for a 100° eyepiece. Always start your eyepiece set with a low power one that shows the largest piece of sky the scope can give.

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Yes sounds like an 8” dob would be more suitable for you as it’s easy for anyone to carry. An 8” solid tube will fit in any car. The only advantage of the flextube is when storing. One thing most find surprising is that the solid tube is about 1kg lighter than the flextube. The collapsing mechanism adds weight.

The Skywatcher is OK but would recommend spending just a bit more and getting the Bresser 8” dob. It’s just a better quality scope with a lot of improvements over the Skywatcher and well worth the extra. You will find that most end up modifying their dobs to improve them but the Bresser already has the improvements done for you. Would recommend getting the optional 1/10 upgrade knob for the focuser.

https://www.bresser.de/en/Astronomy/BRESSER-Messier-8-Dobsonian.html

Edited by johninderby
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Thanks a lot for you all! I will dig in more to the 8'' version, also the Bresser one. SW is something I can get from Finland and with online/hands-on help if needed, but sure, maybe I could manage without the extra help! Also, if the Bresser is better anyway, I can spend the money to that instead of a larger scope. The SW 8'' collapsible was what I first thought, but at least SW-webpage I could not find it without the synscan goto. But I will definitely go to make some measurements from my car to see if the solid tube version could actually fit in to the trunk. I have watched a lot of youtube videos so I am familiar with the size of the telescopes, but I guess for me the weight is more of an issue (don't want to drop anything!). My 4 year old daughter weights about 15kg, and at least she feels easy to carry no matter which position she is :D

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Here’s my thread on the Bresser 10” dob but the 8” is the same,  just smaller. but will give you a better idea of what the scope is like.🙂

 

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On 26/09/2019 at 13:22, johninderby said:

Here’s my thread on the Bresser 10” dob but the 8” is the same,  just smaller. but will give you a better idea of what the scope is like.🙂

 

Thanks from the info again! I have now almost ordered the 8'' version of this, but just out of curiosity, could you specify any properties that are better with this telescope compared e.g. to the SkyWacher version? Not meaning I am not believing you (I am) but just out of curiosity 😃  In addition, do you have any recommendations about the eyepieces that could be good to start with? It comes with the 25mm SPL, should I get something else also right away? 

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Posted (edited)

Optically the Bresser and Skywatcher are very similar. There won’t be a lot in it.

The advantage the Bresser has over the Skywatcher is as follows.

Focuser. 

       The Skywatcher has a cheap one that while usable is usually the first upgrade that people do. The Bresser has a great high quality focuser rhat is a pleasure to use although recommend ordering the 1:10 knob.

Alt & Az Bearings

       No contest as the Bresser has proper full sized alt bearings and a proper az bearing. On the Skywatcher the az bearing  in the base is just three teflon pads rubbing on the underside of the base. The Bresser has the three teflon pads but also a textured bearing ring for the pads to run against. The Bresser’s alt bearings also make great carrying handles. Also with the Bresser you just have to drop the tube into place on the base. With the Skywatcher you have to insert handles into each side and screw them into place after dropping the tube in place.

Way the tube is mounted

       The Skywatcher has plastic bearing”blocks” that are bolted onto the tube. The Bresser uses tube rings which aloow you to move the tube up and down a bit to adjust balance (afer temporarily .loosening the tube rings). Also you can rotate the tube to put the focuser in the right position for you. Then as it uses tube rings easy to remove the alt bearings and fit a dovetail if you ever wanted to use the scope on an EQ mount.

Inside of tube

      The Skywatcher has some thin paint that isn’t very black. The Bresser has a rubberised anti-refective coating that is very effective. Yes proper flocking would imprive it even further but not really needed.

Mirror cell

      The Skywatcher has a very basic 3 point mirror cell. The Bresser has a proper 9 point cell for beter mirror support. Although in an 8” scope not a huge advantage.

Secondary mirror adjustment

        The Skywatcher has screws to adjust the tilt. The Bresser has asjutment knobs.

Now to the weak point of both scopes. Poor finder scopes. They need replacing with something better. Usualy a 9x50 right angle erect image finder is fitted. This is where the Skywatcher has it’s one adavantage. A standrad finder mounting shoe is fitted. The Bresser has an odd finder shoe and will want chaning to a Skywatcher type shoe. You may also want to fit a red dot finder as many find using the red dot fiber is usefull to get you near to you target and then use the right angle finder to zero in on your target.

 

Hope this answers your question.

Edited by johninderby
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Ditto all the comments about Dobs. 👍

Simplest, best all-rounder, mirrors - so no Chroma fringing, wide field f5 and high mag when necessary with Barlows.

I've tried Eight, Ten, and Twelve Inch Dobs, and it depends completely on how far you will need to carry it.

My twelve inch goto synscan flextube (bought secondhand), is amazing, but I can only move it by wheeling it around, and (only just possible) carrying it through an external doorway in the two constituent parts.

I used to have a ten inch GSO solid tube Dob, and that was a monster to grapple with, like cuddling a four foot long heavy torpedo, so it was actually trickier to move than the twelve inch flextube.

I kept my original solid tube Skywatcher eight inch Dob because it is so easily manageable in the two parts (base and OTA). 

I've had no experience of an eight inch flextube, but I  think there would be little advantage of the folding in that size, as the solid tube is still quite manageable at about one meter long and quite light.

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Posted (edited)

I think the sct is your best bet nothing can match its size, like 8sct. And if u want portable then try the 8se.

You get it all tripod tracking goto etc of course 1000 u cant buy new but I always see some on the used market.

It's also only 35 lbs total I carry everything with 1 hand by the fork arm, of course I  cant go too far like that tho.

 

Edited by joe aguiar

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also you said that u don't want it to take up your whole back seat BUT either one will do that. also the 10 inch dob is a 2 step setup maybe the 8 inch you can do it in one shot .

the dob wont give you tracking at all a eq verion will and u can later add a motor drive to keep the object in your ep.

 

most dobs Teflon friction is not smooth enough to alow mm movement, so at high powers moving it in a mm movement is hard. moving it lets say half an inch is not much BUT in the ep that can throw the item out the fov. these dobs if its too light and smooth it will slip so it has to have friction to keep it where its pointed but then it isn't smooth enough for high powered views.

 

also both dobs with be about 4ft tall so even looking upwards yopu will be bending down already and if its pointed 45 degree u will be on your knees. what if the ground/grass is wet muddy?some people told me get a table to raise the dob BUT then it HAS to be very sturdy to hold the dob well without vibrations. then that's another item to carry with you too.

 

just letting you some of the cons before u buy a dob so you know what you are getting into.

from your parameters I think the 8" sct is best bet. I have used it on a cg4 mount as well if you want a lighter setup. most times it comes with a cg5.

 

joe jaguar

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The Breeser dob can be moved a mm at a time due to the proper bearings yet doesn’t move too easily. Just right. Get a stool/ seat for comfortable viewing. If you want an easy way to add tracking get an EQ platorm and stick the whole dob on it.

BCDCE50E-1590-491E-B7E7-581BAAD91ACA.jpeg

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Posted (edited)

based on my experences before they cant be moved easily but ok

I rather not carry another 3 items tho like a stool and a table for the dob and a eq platfom. I heard from the cenius that 80% of the population live in citys anything bigger then 500k pop and more. and within those citys / large citys and mega city a huge population growth is the apt condo market. for those people carrying 3 to 4 trips outside down the elevator to the courtyard cant be done  leaving your gear alone.

I still say the 8"sct on eq4 or 5 is better bet or a 6"f/5 reflector on eq4 is a 1 step setup and you don't need the tracking platform table or stool to view. but this is based on my years of obsevering and other may have different prfrences.

those tracking are expensive at least 500 from what I saw before which is almost the whole scope tho.

Edited by joe aguiar

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The most important thing in selecting a telescope is finding one that suits you. It might be an SCT or it might be a dob that suits you best. People are different so don’t always agree on what’s best. A lot depends on your particular requirements. Of course we could get into the an APO refractor is the best argument but not going there. 🙄

I’ve had 5”, 6”, 8” and 11” SCTs but sold all of them. Might even get another one someday. Who knows but in no hurry. 🤔

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I have got a lot of useful info from here, so thanks from that! Of course, you cannot get everything to be perfect right at the start, and I am also keen on practicing and learning. I know there are also a lot of personal preferences depending on what is important and prioritized (the debate between 8'' SCT or Dob seems to be around 50-50). I measured our car trunk, and it is around 110cm wide. In principle, the 8'' dob could fit there if I place it somehow diagonally with other end of the OTA higher than the other. So needs proper support if it is safe to transport OTA that way anyway. However, it is not a problem to put it to the backseat, if necessary. 

I decided to go to the 8'' dobson. It seems to be much cheaper to the 8'' SCT + eq mount, considering I also need to by eyepieces etc. at some point. And what I have understood, it should be relatively easy to use "general" telescope. During assembly, it is not a problem here to leave stuff alone, so that won't be a problem. Wet grass etc. wont be a problem yet, as I planned to bring the telescope to my parents' home, where they have huge terrace and also a big dock by the lake (not floating one, but like, solid?) which I think are super practical places to start observing. Sure, it is probably not the best grab-and-go telescope due to its size, but at the current state of my life that is not something I can do (unfortunately) anyway (having kids and all). 

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Good, I think you properly understand that every telescope is a comprimise. 👍🏻

I like the simplicity of a dob. If you look at my link to the Bresser 10” dob you’ll see that I fitted feet to keep the base out of the wet grass. 

I do like other scopes too. Here’s Big Red a scope that I built myself using Japanese optics.

     John

2B8ADA87-6B44-47D6-9F52-87405FAF1549.jpeg

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1 hour ago, Sini said:

I have got a lot of useful info from here, so thanks from that! Of course, you cannot get everything to be perfect right at the start, and I am also keen on practicing and learning. I know there are also a lot of personal preferences depending on what is important and prioritized (the debate between 8'' SCT or Dob seems to be around 50-50). I measured our car trunk, and it is around 110cm wide. In principle, the 8'' dob could fit there if I place it somehow diagonally with other end of the OTA higher than the other. So needs proper support if it is safe to transport OTA that way anyway. However, it is not a problem to put it to the backseat, if necessary. 

I decided to go to the 8'' dobson. It seems to be much cheaper to the 8'' SCT + eq mount, considering I also need to by eyepieces etc. at some point. And what I have understood, it should be relatively easy to use "general" telescope. During assembly, it is not a problem here to leave stuff alone, so that won't be a problem. Wet grass etc. wont be a problem yet, as I planned to bring the telescope to my parents' home, where they have huge terrace and also a big dock by the lake (not floating one, but like, solid?) which I think are super practical places to start observing. Sure, it is probably not the best grab-and-go telescope due to its size, but at the current state of my life that is not something I can do (unfortunately) anyway (having kids and all). 

Dobs are great with kids because they are practically impervious to damage in use or transport.  You may need a step stool for shorter kids to get them up to the level of the eyepiece for viewing objects near zenith.  Pick up a collimation cap at the very least to check primary mirror alignment each time it is setup.  It also makes a nice dust plug during storage while allowing for a tiny amount of fresh air to reach the inside of the tube (assuming the main tube's ends are capped).

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Hi again, decided to update! My 8'' Dob arrived few days ago, and I got to test it yesterday! It has been very cloudy and rainy here, so I could only see some bits of the moon for a very short time before the clouds took over, but I am impressed (and my parents too!) 😃

But in case @johninderby is around (or anyone with more experience than me..), I might have few questions. To have enough "outward" focus with the 25 mm eyepiece to get sharp images, I needed to add the drawtube extension. Is that, kind of,  normal (I noticed you use it with your 10'' dob)? If it is, then my intuition says that with shorter focal length (like 10 mm) eyepieces I need to focus more inward, is that correct? I did not collimate the dob, as it looked okay for now when following the manual instructions, and for star test, well, they were hiding behind the clouds...  I also noticed you had nice handle attached to the tube, which I think would help a lot. Did you just drill screw holes to the tube or how is the handle attached? Will the screw ends affect to the image, I guess they should be painted black at least? The finder was okay, but I found it slightly difficult to use as the image is also upside down. Not sure if it would be easier if I get a finder that shows the sky as it is (to first pick object by naked eye, then from the finder and so on) or if it is just matter of learning, any suggestions/thoughts?

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Hi

Yes it is normal to use the extension piece with eyepieces and with most eyepices you shouldn’t have to move the focuser very much when changing eyepieces. Exactly where they reach focus depends on the design of the eyepiece not the mm. If using a camera or binoviwer you might not need the extension. 

A right angle errect image finder is a very popular upgrade. The Skywatcher one is good and usually the cheapest. Telescope Express has many to choose from.

Collimation is a bit of an art but not difficult with a bit of practice. There are many tools for collimation and this subject often provokes dicussion on what is best. A star test is the best way of checking your collimation. This guide is very usefull.

http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/

The handle was just bolted on from the inside using black button head bolts. Button head are best as they don’t stick up too much. There are many suppliers of handles on line such as Amazon etc. and I bought this one from a local hardware store and it’s called a door pull and is a nice fat handle. I enlarged one of the finder base mounting holes and drilled another for the other end. I covered the other hole finder base mounting hole with a self adhesive screw hole cover.

The new finder base I fitted required drilling one new hole as the stock finder base holes are too far aoart. Used one of the self adhesive screw covers cut in half to hide the unused hole. 

Glad to hear you are enjoying using your scope already. 👍🏻

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Edited by johninderby

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8 hours ago, Praseodyymi said:

The finder was okay, but I found it slightly difficult to use as the image is also upside down. Not sure if it would be easier if I get a finder that shows the sky as it is (to first pick object by naked eye, then from the finder and so on) or if it is just matter of learning, any suggestions/thoughts?

You might look into a unit power finder such as a Telrad or QuikFinder.  Their bases can just be stuck on the tube with double sided foam tape if you don't want to drill additional holes.  They do require cranking your head around, but it's manageable for the young and young at heart.  These finders make star hopping to your target much easier than trying to sight along the tube.  Once in the general vicinity, a RACI (Right Angle Correct Image) finder will be much easier to use.  I find trying to use a RACI by itself to put the scope in the general vicinity problematic because you're looking at the tube, not the sky, as you line it up.  I like to think of RACI's as low power refractors; and as such, most useful for picking out objects invisible to the naked eye but just detectable with it for centering.

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