Advice what to buy

[AyaOva]

Hello, everyone. I need some help from people who have experience viewing trough multiple types of telescopes.

I used to own a 150/1200 dobson but I had to sell it for many reasons one of which was I'm moving often and can't carry it with me.

Later I bought a more compact SkyWatcher Heritage but the view trough it is lacking compared to the old one - the planets are smaller, more distant and they're brighter so they lose surface detail.

I want to buy something that's still smaller than my first telescope but comes as close as possible to the image I could observe trough the 150/1200.

The first thing I considered buying was a 150/750 on a compact mount: https://www.astroshop.eu/telescopes/bresser-dobson-telescope-n-150-750-messier-dob/p,58693#tab_bar_1_select

What bothers me is that I read the aperture ratio is still f5 just like the Heritage and I read that higher f is better for planets?

So then I considered buying a Maksutov type of tube. https://www.astroshop.eu/telescopes/bresser-maksutov-telescope-mc-100-1400-messier-ota/p,44004#tab_bar_1_select

The ratio on this is f14 so I'm assuming this is better for planets and the compact size sounds amazing for people like me but how close would that telescope come to the view from a 150/1200?

What bothers me the most about this one is that I read higher f means more narrow field of view. I want to buy the tube and put it on the mount that I got with Heritage so my question is:

with the limited field of view, will I have too much trouble manually tracking planets on maximum magnification with this tube or will I not be able to observe at maximum magnification? Will it's view come close to a 150/1200 and if not do you have any other recommendations what might? Maybe a third option like a 130/1000?

Just fyi I'm not interested in astrophotography and also with both 150/1200 and 130/650 I've had no trouble manually tracking at maximum magnification.

[Victor Boesen]

According to the situation you are in I would also recommend a mak like the one in the second link. You ask if you would be able to tract the planets manually and then I have to ask if you already have a suitable mount for holding the telescope, because if you don't then the answer to your question is simply no.

I would recommend a mount like this:
https://www.astroshop.eu/alt-azimuth-without-goto/skywatcher-mount-az-4-steel-tripod/p,16101

That mount is used by many to handle longer refractor telescopes and I'm sure it'll do the job with the mak you shared yourself.

I hope this makes your decision easier! feel free to ask anything else.

Victor

[vlaiv]

Out of the listed scopes, 150/1200 Newtonian is by far the best scope for planetary observation. Pity that you are not able to hold onto it.

150/750 and other F/5 scope are well able to provide good looking planets but there are couple of issues that you need to address in order to get such views.

First you need a suitable eyepiece to get to wanted magnification. Too low magnification - planets will look small and bright. With 150/1200 it is fairly easy to get to "planetary magnifications" because scope has long focal length. With supplied 10mm eyepiece magnification is x120. You need ~6mm eyepiece to get such magnification with 150/750 or ~5.5mm eyepiece to get such magnification with 130/650 (I think Heritage has that aperture and focal length). Or you can use a decent barlow lens to give you scope focal length amplification, and hence more magnification out of eyepieces that you already have.

Second very important point about fast scopes is that collimation needs to be much more precisely done than your original 150/1200 (f/8) scope. So in order to get best views out of such scopes, you really need to keep eye on collimation and make sure it's next to perfect.

As for manual tracking performance - it depends on three things - eyepiece magnification, eyepiece AFOV and of course, how smooth is mount tracking.

Higher magnification means that planet is "moving" out of the view more quickly.

Larger AFOV of eyepiece - means that view thru eyepiece will be "wider", or cover more of the sky (for same magnification), hence it will take planet a bit more time to drift out of the view - less often corrections.

And smoothness of the tracking speaks for it self - how easy it is to reposition scope when planet moves outside of field of view.

Since you mentioned that you had no trouble manually tracking with 6" F/8 dob, I think that you will not have trouble tracking with any of mentioned scopes.

Another thing to consider is aperture size. If you are used to 150mm aperture, and have gone x150-300 magnification wise, it will feel as a step back to go down in magnification and detail. You should really look into 5" or 6" class instrument to replace 6" F/8 Newtonian. Depending on your budget and for ease of transport/storage following instruments should be on your list:

- Short tube newtonian like 150/750 - but do be careful about collimation and need for short focal length eyepieces or decent barlow lens.

- 6" Mak-Cass - it will be able to use longer focal length eyepieces to get you to planetary magnifications, it is really short and easy to carry, but can suffer from cool down issues (it takes a bit longer for scope to reach ambient temperature and this is important for planetary observing)

- 6" SCT - very versatile scope, a bit less in everything mentioned for 6" Mak - less focal length, so a bit shorter FL eyepieces, less cool down issues - a bit less glass in corrector but still needs to cool down.

Mind you both 6" Mak and SCT are prone to dew issues - so either dew heater or some sort of dew shield is often added by users of these instruments.

- 4-5" ED doublet refractor - here we are starting to stretch the budget (depending if you have set budget) - this will cost the most, and arguably will provide the best planetary views in this list. Portability and storage size wise - it will be between Short tube newtonian and Mak/SCT (thinner than former and longer than latter). You can go for 4"-5" Achromat if you are not that sensitive to chromatic aberration, but you will be giving up some sharpness unless you get long focal length instrument - like 4" F/10 or F/11 with a good figure. Long focal length achromats tend to be long instruments - almost as long as 6" F/8 newtonian - so check if it will be a problem to store or move if you go that route.

All of above scopes will sit very nicely on Skywatcher AZ4 mount - that is smooth enough for easy tracking of planets and is relatively light but stable platform.

HTH

[domstar]

Great post above but I have to disagree with the AZ4 mount as good for tracking planets. I have one and I like it but it isn't great at tracking at high magnifications or at least I'm not skilled at tracking at high magnifications. 90x is fine but 150x is not much fun for me because it doesn't have slow motion controls. 

I know your question is about scopes and not mounts but as two people have recommended the same mount I thought I'd warn you about the lack of slow motion controls.

Good luck- I hope you get a wonderful scope.

[AyaOva]

I did look into eyepieces when I bought the Heritage since I knew with the different length there would be a change in eyepieces, I bought a 6mm eyepiece with it but view still feels lackluster. I'm not sure which gutted the view more - the size of the mirror or the length of the tube since both got downgraded. Or the fact that half of Heritage tube is uncovered and light pollution ruins the view. Otherwise Heritage probably came well collimated since the edges of the planets look really sharp and nice - they're just small and less detailed sadly.

Since price will go up a lot with this mount I guess I will give up on macs. But I'm not sure what tube combination should I get then. Do I get a larger mirror (6") with (still) shorter tube or do I go for another 5 inch with a longer tube 900 or 1000 compared to the current 650.

[Stu]

Great post from @vlaiv laying out plenty of options for you.

May I ask what your constraints are? You say you move around frequently, but what is practical for you to take? Presumably you have a car?

When you are observing are you short of time or can you get setup and allow the scope to cool?

Something like a 6” SCT on an AZ5 might give you a decent solution, having slo mos on the mount to help tracking.

[AyaOva]

No car. The weight and size are too much for a small person with chronic back problems. I'm not even sure if that 150/750 I linked isn't gonna be too much as well. But I don't have a tripod mount either only the one that came with Heritage so it makes things expensive. I'm trying to also figure out if there's anything I can mount on it and just not buy a mount at all.

[Stu]

2 minutes ago, AyaOva said:

No car. The weight and size are too much for a small person with chronic back problems. I'm not even sure if that 150/750 I linked isn't gonna be too much as well. But I don't have a tripod mount either only the one that came with Heritage so it makes things expensive. I'm trying to also figure out if there's anything I can mount on it and just not buy a mount at all.

Chronic back problems I can relate to.

So, what sort of weight can you cope with, that’s a starting point surely?

[vlaiv]

18 minutes ago, AyaOva said:

No car. The weight and size are too much for a small person with chronic back problems. I'm not even sure if that 150/750 I linked isn't gonna be too much as well. But I don't have a tripod mount either only the one that came with Heritage so it makes things expensive. I'm trying to also figure out if there's anything I can mount on it and just not buy a mount at all.

Having constraints both on weight (total, so both mount and scope should be light) and on budget is tricky to deal with.

I'm not sure what is carrying capacity of Heritage "dob" mount, but I do presume it has god a Vixen dovetail clamp so other scopes can be used with it. I can how ever imagine that it is going to be awkward to use any scope that has eyepiece on the back on such mount (Mak, SCT or Refractor).

If there were no budget constraints, I would say - go for 6" SCT and Skywatcher AZ5 mount - very light weight combination - OTA is less than 4kg and mount is less than 5kg so total weight is going to be about a half of that of 6" Dob. This setup is going to have much less bulk so it should be quite a bit easier to carry around.

Next thing to consider budget wise, would probably be SW Mak 5" or Bresser Mak 5".

Skywatcher is more or less know to produce decent scopes, not sure how good are Bresser maks. There is difference between two designs however - Bresser Maks are slower scopes - that means eyepieces will work better and you will reach high magnification more easily (any decent eyepiece will work fine with SW Mak as well - both are considered slow scopes by today's standards). This is good if you are interested in planetary only. If you want to take a peek at other targets, additional field of view of faster SW Maks might be a benefit.

In the end you will choose the scope to suit your constraints - budget and weight, so this might help your decision in the end - Here is a simulated view of Jupiter for different diameter scopes to give you rough idea how much detail you are going to loose by using smaller aperture scope. Do note that this is simulation only, it assumes perfect optics (with 30% CO so closer to Mak and SCT spec than to 6" Newtonian) and does not account for actual conditions nor observer (so in reality you might see less difference).

4" (100mm) scope:

5" (125mm) scope:

6" (150mm) scope:

Images are best views at about half a meter from monitor and represent respective maximum detail and magnifications for each scope (~ x200, x250, x300).

[SIDO]

A 6" mak or sct on a lightweight alt az platform is a really popular combo, a focal reducer can be added easily when a slightly wider field is needed for other objects. Good planetary representations Vlaiv, the 6" aperture is really a great place to start for planets. 

[AyaOva]

I appreciate all the detailed replies. Much more detailed than on my local forums. The thing is I live in a third world-ish country and most of the suggested scopes are out of my league. What I did get from this topic though is that aperture is more important for bigger looking planets and the length of the tube is more about getting sharper edges at higher magnification?

So I'm guessing I should go for the 150/750 scope although I've only had Sky Watchers so far and I'm very satisfied with their mirror quality I'm not sure what's the quality of a Bresser reflector.

This is my current telescope

the reason I was considering a Maksutov tube is because it's cheaper without a mount and I was hoping I could just replace the tube and use the MAksutov on this mount. which I already have but if you think tracking would be a problem and with a smaller mirror I guess it's not the best option.

Ideally my dream is to have an 8" dobsonian in my backyard but life as it is now is just living under rent in small rooms so no opportunity to carry such a big scope around.

[Ricochet]

What eyepieces are you using with these scopes? Just the supplied 25/10mm and a 6mm you bought? What exact eyepiece did you buy? I am surprised there is such a difference between the two scopes but an f5 telescope requires better eyepieces than an f8, perhaps that is part of the problem. The smaller, brighter description means you're viewing at a lower magnification which possibly can be resolved with different eyepieces. 

[AyaOva]

27 minutes ago, Ricochet said:

Just the supplied 25/10mm and a 6mm you bought?

And a x2 barlow. The barlow is cheap I don't even remember what brand, nothing is written on it. The 6mm is Vixen.