Reflector or Refractor ?

[JOC]

44 minutes ago, Louis D said:

Although most Dob focusers don't have enough back focus to reach prime focus with a DSLR

I've seen that mentioned on SGL several times.  For the record I never had the slightest problems with my set-up 200P flextube from FLO.  T-ring on, took out the 1.25" adapter and just whacked straight into the 2" EP holder on the 200P and never had any issues getting spot on focus with my camera which is an un-modded Canon T3 Rebel (1100D clone) in fact my Avatar is a photo taken with just that set-up.

[Golfox2]

Hi guys, thanks a lot for every answers, I really appreciate how you help me, and I am learning fast, even though it still remains difficult

So,
@Geoff, the Skywatcher Heritage 90P Virtuoso looks really well, but I am surprised the DSLR mount is without the scope tube, only the goto mount ?
@happy-kat, I assume that the darker the environment, the larger aperture I should use for better results ?
@Louis, what's the difference in star-seeing quality between parabolic and spherical mirror ? I feel confuse, as a parabole is an element of a sphere ... ? or you mean plain sphere like a "D" rather than a ")" ?

> What should be the primary mirror diameter for a beginner like me with telescopes, you guys were telling me 150-200mm as shown in your links ?
> A smaller primary mirror size means a less bright image seen in the scope, doesn't it ?

I am then narrowing down between:

- a Skywatcher 200p

- a Skywatcher 150p with GoTo

- a Heritage 90p (seems really small ?)

But not sure which one to choose :S

what do you think of this nexstar 4se, above budget, but could be doable if I wait for christmas ?
meanwhile, I don't understand what is a back focus and barlow (is it the eyepiece ?)

 

Thanks folks, I can feel I am coming up with a more precise idea of what I need, everytime I check new messages on this topic =D

Can't wait to read you again

[ronin]

For the budget then really goto is not an option, although something like the Meade ETX-80 would just about fit in. One may be an option.

One question I have is how easy or difficult will be the task of taking it up the mountain to observe. For this you really do want "simple". Goto is not necessarily simple, there is a scope and a mount and power and eyepieces and a few other bits. Equally a 6" dobsonian is not big but again carrying bit from A to B when A and B are a distance apart is not simple either. Even with a dobsonian you will have 3 bits + OTA, Base, Accessories.

When you have 3 bits it causes problems as you have 2 hands and arms.

I have a Bresser 102 refractor that is maybe a bit big but is a good size and Bresser do a simple manual single arm mount - twilight I think. Likely a bit above budget for the pair however. ES, who Bresser seem to work with, do a very nice 80mm scope on a mount - the Flirstlight 80640 - the problem is they do not offer it in the EU or UK. Shame as it is $150 in the US and as a first scope it is sort of a good option.

For Bresser this is worth looking at: https://www.bresser.de/en/Sale/Display-Items/

Occasionally a well priced item appears, I bought my 102 via this and it was half or less the cost.

One other aspect I will say is that there is no ideal first scope, in effect half expect to buy something now then purchase what you find you really want later. The alternative is to know what you want specifically now then buy a good one now. A good all round ED refractor of around 90-100mm is a good do-it-all scope but a scope like that is easily 1000-1200€ all on it's own.

Problem is that astro equipment is increasing in cost. As an example there is a new WO ZS 61 scope (small and easy to go up a mountain with. Also there is a new Skywatcher GTi WiFi mount. Here is the sum:

WO ZS 61 - £400, GTi WiFi - £250, good diagonal - £100, 3 eyepieces £150: Total £900. That is 1000€ easily.

Look at the Bresser 102/600 and think of it - will do lots. Being f/6 the CA is a little better then an f/5. But a mount will I think have to be a simple manual Alt/Az.

[Ricochet]

9 hours ago, Golfox2 said:

he Skywatcher Heritage 90P Virtuoso looks really well, but I am surprised the DSLR mount is without the scope tube, only the goto mount ?

It is a small mount for a small telescope. I think you would have clearance issues when trying to look up if you fitted a camera to the scope, plus the weight might be an issue.

9 hours ago, Golfox2 said:

I assume that the darker the environment, the larger aperture I should use for better results ?

A larger aperture will give better results in any location.

9 hours ago, Golfox2 said:

what's the difference in star-seeing quality between parabolic and spherical mirror ? I feel confuse, as a parabole is an element of a sphere ... ?

A parabolic and spherical curves are different shapes, as shown in the image below. The mirrors in the telescopes we use only use the central section of these curves where the profiles are quite similar. This is why for telescopes of sufficiently high focal ratio a spherical mirror may be used. The parabola bringing all the light to a single focus point means the image from a parabolic mirror is sharper.

9 hours ago, Golfox2 said:

What should be the primary mirror diameter for a beginner like me with telescopes, you guys were telling me 150-200mm as shown in your links ?

I've seen quite a few experienced observers state 100mm as the minimum they have found from experience (aside from solar telescopes).

9 hours ago, Golfox2 said:

A smaller primary mirror size means a less bright image seen in the scope, doesn't it ?

Yes and no. It is true that for a certain magnification a smaller scope will be dimmer than a larger scope. However, I think that the optimum magnification for viewing an object is more determined by exit pupil (proportional to brightness) than by magnification. This means that for a fixed exit pupil (brightness) the larger scope will have a larger magnification. The larger scope will also resolve dimmer stars than the smaller scope.

 

From your scope choices I would either go with the 200p Skyliner or 150p Star Discovery. I think if you buy one of the others you will soon want a bigger telescope, unless portability is your main concern. It really comes down to whether you want an electronic go-to system to find objects for you or a slightly better view once you find the objects. In addition, a tripod mounted telescope will be easier to use on uneven ground.

[AstroKerr]

Before you spend a single ducat, go to a star party and try out any thing they'll let you try.

Before your budget starts getting bigger and your wait longer, visit with the members of the nearest astronomy clubs and suggest they 'outreach' you.

Put all thoughts of a 'goto' out of your head until you've seen one in action, mashed the little keys on the controller, goofed up the keen little sequence a few times.

I'd like you to think Equatorial Mount (maybe with tracker motor - which is useful). It will help you acquire skills you will need later that you need now.

Don't try to pick reflector/refractor/schmidt-cass/mak-cass before you've looked thru each and understand how they work and what they will do well that you might like to pursue.  Me, I like'em all - specifically whichever it is that I'm not getting shoved off. Little ETX60, 8" Newt, 90 Mak - whatever I can peer thru undisturbed and see the moon if not jupiter if not saturn if not doubles if not Neb-things if not M-things - heck, I like looking at the ducks, cormorants, geese, heron/cranes, hawks, eagles and condors in the area of the dam I work at. It's ALL good.

Go Astro-clubbing and get hands-on and eyes-thru before you buy anything other than say a (preferably pre-owned) 114 Newt or 60~80 refractor on an equatorial mount - everything else you might want to buy you really need to try first.  You get sort of 'free pass' on the 114 Newt / 60~80 refractor because they're like taters (or carrots or cabbage); they're a staple you can pass on to your neighbor w/ kids for a decent recoup, or some one like the SG Loungers or Cn'ers, myself certainly included, who will gladly listen to your upgrade tale and want to help out and take it off your hands - seriously. And if you get a good deal and it suits you - you'll keep it for a long while because it's your first and what the hey, ya save a few weeks more, buy the 2nd and YOU GOT TWO!! So you can share with loved ones, who despite their protestations of eternal unconditional love, will stomp, mutter and whine until you get out of line =). Telescopes are that magical, they really are...

Everyone here wants you to succeed, guaranteed. You have gotten excellent advice, guaranteed - these folks are very good at this, they have an immense amount of experience, they have seen things that to most are only legend - but none of us are you, so at some point unless you get hands-on and eyes-thru - it can all seem like noise. I'm months new and they tell me 'go slow' and so I pass that bit on - go slow, do not leap. Try before buy - it saves geld & regrets.

Clear Skies & Sharp Eyes,

Jim

And I am going slow, really - tho' not always by choice. That has been the best advice, thank you.

 

[Louis D]

3 hours ago, AstroKerr said:

I'd like you to think Equatorial Mount (maybe with tracker motor - which is useful). It will help you acquire skills you will need later that you need now.

What skills are you alluding to?  I've been observing with undriven alt-az mounts for 20 years now and even built and then abandoned an equatorial platform because it hindered grab and go too much.  Tracking's nice, but not a necessity except for astrophotography.

[Louis D]

15 hours ago, Golfox2 said:

@Louis, what's the difference in star-seeing quality between parabolic and spherical mirror ? I feel confuse, as a parabole is an element of a sphere ... ? or you mean plain sphere like a "D" rather than a ")" ?

I think you're confusing spheres with cones.  A parabola is a conical section, not a spherical section.  Ricochet has it right that parabolas bring all rays to a single focus so you will get a sharp image.  At f/8 and above, a lot of lower cost 6" Dobs used to use spherical mirrors because the difference in figure at the slow focal ratio is slight enough that decent images can be formed.  At f/6 and below, you definitely want a parabolic mirror for the sharpest images.  A lot of cheap ebay telescopes use fast spherical mirrors without explicitly stating it, so buyer beware.

Parabolic mirrors aren't perfect.  They still have off axis coma which a coma corrector can take care of once you become sensitive to it.   Most beginners won't even notice it because they're only looking in the center using fairly narrow field eyepieces which don't easily reveal edge of field coma.  When they do use wide field eyepieces, they usually use cheaper ones with loads of edge of field astigmatism which totally masks the coma from the mirror.

[Louis D]

23 hours ago, JOC said:

've seen that mentioned on SGL several times.  For the record I never had the slightest problems with my set-up 200P flextube from FLO.  T-ring on, took out the 1.25" adapter and just whacked straight into the 2" EP holder on the 200P and never had any issues getting spot on focus with my camera which is an un-modded Canon T3 Rebel (1100D clone) in fact my Avatar is a photo taken with just that set-up.

That focuser doesn't appear to be particularly low profile.  I use a low profile focuser on my dob with the focal plane set at most about 20mm above the most inward position, and that's with my collimation screws near the top end of their travel.  I would need the focal plane at least 55mm above the most inward position of the focuser to use a T-ring mounted DSLR.  What is the percentage obstruction of your secondary?  I couldn't locate it online.  Mine is 18% by diameter, so I couldn't go with too tall of a focuser or a focal plane set to far away from the tube.

You also have the advantage with that scope in that you could always extend the poles less to reach focus if you added a filter wheel or OAG.

[JOC]

25 minutes ago, Louis D said:

What is the percentage obstruction of your secondary?

I wouldn't have the foggiest idea - if it's just the percentage by width of the primary I guess I could measure it and report back.  Mind you, the 200P flextube did advertise that it was 'ready to go' for DSLR photography, so perhaps that helps.

[Golfox2]

Wow, thanks a lot everybody ! 

So I better go for a
- manual (not GoTo)
- alt/azimuth
- tripod (easier to set up on my mountain's uneven ground)
- parabolic reflector
- mini 100mm diameter
- reflector (mirrors)
am I right ?

- and that I can carry entirely alone, with my 2 arms et 2 hands hahaha

I'll look for astronomy clubs near my city and see if I can try some scopes

If I understand good, I should go for a Skywatcher Skyliner 200P but with a tripod instead of the dobsonian mount, right ?

thanks folks

PS edit :
like this one : https://www.firstlightoptics.com/reflectors/skywatcher-explorer-200p-ds-ota.html
with a manual alt-az mount tripod ? (if I wait 'til christmas for money huehue)

[AstroKerr]

Gosh, Louis, I dunno... accurate polar alignments and the like, twisting those knobby bits associated with RA and Dec in a controlled manner so you can, needs be, use (silly me) tabled celestial coordinates and the RA and Dec rings (which may be of questionable quality, size, readability and hence utility) whilst adjusting for local time to find something so mystical, so elusive that point-n-go or star hopping just isn't getting you there OR you just want to expand your astronomical education/skill set a bit as countless others have over the centuries? There can be a certain satisfaction in that. The OP did indicate a certain minimal interest in AP and that, from what I hear, sometimes requires you to point a camera at something your eyes can't quite see and track it so that the magic of the electronic (or film) astronomical image capture device can occur - maybe I misunderstood...

I like AltAz w/ slomos. I like the little Orion Autotracker or the Orion/Celestron/Meade Goto AZ mounts - they're great for 4 button power slewing to a target, then one button push drops the speed and I can slow-slew after something - crazy fun for visual - and they have track modes as well if you do the inital alignment, which I usually skip because, as you mention, they're great grab and go! But doesn't it (in manual), unless you wedge, take two tweaks to track with AltAz vs EQ's one (properly setup) in general? So I thought maybe, given the OPs stated interests & budget and my limited experience, 'EQ' might be easier (after the initial learning curve) and more resource efficient to get him to 'visual with option of some AP'. 

I have also used a ball head camera mount to fine effect. No 'true' dobs yet, and when we do it will more than likely get 'equatorialised' to facilitate drag tracking.

I have the flu.

Clear Skies & Sharp Eyes,

Verbose Jim

[happy-kat]

I don't think you will carry a 200p alone with your two arms particularly over uneven ground and even less likely if tripod mounted. If you did it would be more than one trip.

There is a really good show me your telescope I'll try and find it.

Edit: didn't find the past I was after

200p on eq5

[AstroKerr]

2 hours ago, JOC said:

I wouldn't have the foggiest idea - if it's just the percentage by width of the primary I guess I could measure it and report back.  Mind you, the 200P flextube did advertise that it was 'ready to go' for DSLR photography, so perhaps that helps.

I'm fluey - but - It's can be determined for both as diameter and/or area. Area is the more 'refined' calculation, yielding what percentage of the primary's light gathering area is lost by inclusion of the secondary in the light path.  Area of circle = pi * (r*r) for both, then As/Ap  or 1/(Ap/As)  commonly 9~13% or so.  Can be higher for smaller main obj diameters - sometimes MFRS will use the same diam sec with a 90mm and a 127mm. Useful for comparing light gathering capabilities between reflectors and refractors, light avail for AP,  Object magnitude limits and so on.

 

Be Healthy, Wealthy and Wise!

[Cosmic Geoff]

2 hours ago, Golfox2 said:

If I understand good, I should go for a Skywatcher Skyliner 200P but with a tripod instead of the dobsonian mount, right ?

I wouldn't. I have a similar telescope OTA - a 203mm f5 Newtonian. It weighs about 9Kg, is quite long and I need both hands to lift it. It goes on a EQ-5 (the minimum mount for visual use - for photography you'd need a heavier mount) which weighs at least as much and is also a two-handed lift. Then it needs the counterweights - another 9 Kg or so.  It takes me up to 15 minutes to assemble it ready for use in the back garden.   

[Ricochet]

3 hours ago, Golfox2 said:

tripod (easier to set up on my mountain's uneven ground)

Sorry, when I said uneven I meant unlevel. A bit of unevenness will be ok for a dob, so long as you're not trying to set up on a slope.

A manual alt/az mount/tripod suitable for an 8" Newt will probably cost your whole budget.

[Golfox2]

AstroKerr, I love your messages hahaha, they're making my day x)
Ow the 200p on eq5 is huuuge, I had not imagined that big... Yeah, it's far better if I can make it in only 1 travel from the car to the observation point indeed.

damn it's more complicated that what I thought. So in fact, I'm looking for a scope that is transportable alone (on a tripod with manual alt/az)

Yes, uneven/unleveled, whatever, I'll be able to find a plane surface somewhere on this bloody mountain !
Ideally, I imagined me on a camping chair, looking through my telescope. So nothing so big or that need a special convey to bring up there.

 

 

[Louis D]

3 hours ago, AstroKerr said:

Gosh, Louis, I dunno... accurate polar alignments and the like, twisting those knobby bits associated with RA and Dec in a controlled manner so you can, needs be, use (silly me) tabled celestial coordinates and the RA and Dec rings (which may be of questionable quality, size, readability and hence utility) whilst adjusting for local time to find something so mystical, so elusive that point-n-go or star hopping just isn't getting you there OR you just want to expand your astronomical education/skill set a bit as countless others have over the centuries? There can be a certain satisfaction in that. The OP did indicate a certain minimal interest in AP and that, from what I hear, sometimes requires you to point a camera at something your eyes can't quite see and track it so that the magic of the electronic (or film) astronomical image capture device can occur - maybe I misunderstood...

I do a two star alignment on my Sky Commander DSCs and then manually slew to difficult targets like PNs and Uranus Neptune.

[Louis D]

4 minutes ago, Golfox2 said:

Ideally, I imagined me on a camping chair, looking through my telescope. So nothing so big or that need a special convey to bring up there.

A lot of folks here in the states observe from car camping areas to minimize carrying distance.

[Louis D]

54 minutes ago, Ricochet said:

A manual alt/az mount/tripod suitable for an 8" Newt will probably cost your whole budget.

Even for a smaller scope, a decently stable alt/az mount and tripod will have some substantial weight to it.

[AstroKerr]

24 minutes ago, Louis D said:

I do a two star alignment on my Sky Commander DSCs and then manually slew to difficult targets like PNs and Uranus Neptune.

Took a look around Sky Commander - nice stuff! Usable with Dobs, Forks and GEMs - that's very handy. Thank you for the info!

 

CS&SE

[JOC]

You probably wouldn't regret buying a 200p on a Dobsonian mount.  In two pieces it can easily be carried I would guess up to about 100 yards easily by one person in two trips, base and Telescope tube (OTA).  30 seconds to dismantle, 30 seconds to put back together and you are viewing.  If you get a flex-tube it will easily go in most cars in the same two bits and will take up no more space than a dining chair to store.  Even better is the 200P Dobson setups are often available 2nd hand as people suffer from apperture fever.

[AstroKerr]

Thanks, Fox-o!

JOC and Louis have both made good cases for Dobs and the points they make are valid. I too doubt you'll regret a 200p Dobs and ya have to start somewhere. I will maintain 'try before buy' whenever possible. Our first scope was going to be a 12" Dobs, but I needed something HoneyBadger and the granddaughters could move easily when I was at work, so the 8" flector... which still turned out more than she likes dragging, but will drag. =/  - and I sort of ignored the smaller Dobs although I couldn't tell you why - meh.

M' gaen t' bile m' haed... 

I still like the lil Heritage - got the Orion equiv.

 

 

[Golfox2]

Yup thanks guys, I'll try before buy at a Stargazing club around my city, and then I'll probably go for the 200p dobs.

Thanks a lot again to everyone for all the help  

[jazza]

Lots of good advice here but I would also advise considering starting out with a pair of good binoculars, 8 x 50.

Cheap and will do what you asked for in the original post. As well as being very compact, comfortable to use, and a great way to see some of the bigger things and learn the sky!

[Golfox2]

Yey but I'm already using binoculars and know a bit of the sky.

Someone at a astro club I know suggests this one : https://www.astromanie.ch/fr/telescopes/246-sky-watcher-skyhawk-1145p-synscan-az-goto.html
Would it be good ? What would be pros and cons ?