Increasing focal length via stacking barlows vs buying Mak/Cass

[Dally]

Seeing that short FL is ideal for AP for DSOs, and long FL is ideal for planetary viewing, is there not a jack-of-all-trades type scope out there or something that allows for you to have a variable focal length/ratio? I would've expected someone to come up with a special kind of telescope to deal with this but the closest I've come to seeing some kind of variable focal length would be one of those flextube scopes yet I don't see anyone using them for AP or attaching them to equatorial or non-Dob mounts. Is the mirror at the back the thing which limits the focal length from being adjusted via lengthening/shortening the tube? I've read briefly about "focal reducers" but it seems these appear only available for certain models of telescopes whereas the barlow lenses are more ubiquitous.

I have a hypothetical scenario. I buy a 6" Newtonian/reflector because of it's "faster F ratio" and cheapy. At some point I start imaging with it and I'd like to start using it on planets too. For that I'd need increased focal length which I'd get from using a barlow but anyone with a Mak/Cass uses a barlow also.... so the benefit is comparable. But could one use stacked barlows in a reflector to put it on the same level as a Mak/Cass with the same aperture?

6" Maksutov £500

-Aperture: 150mm

-Focal length: 1800mm (F/12)

-Focal length with 2x barlow: 3600mm (F/24)

-Total cost: £570

6" Reflector: £230

-Aperture: 150mm

-Focal length: 750mm (F/5)

-Focal length with 3x barlow: 2250mm (F/15)

-Focal length with 2x barlow stacked : 4500mm (F30)

-Total cost £370

I'm not quite sure how calculating focal length from stacked barlows is supposed to work so I'm guessing here.

Again, I don't see anyone use this configuration despite being cheaper and you only need one scope vs two. I smell a rat! *metaphorically*

I understand that with increased mag, the shakes/vibration and streaking may be increased, but would having stacked barlows give a disproportionatly higher vibration and tracking issues vs using a single barlow lense? Would getting a 5x barlow lens be a better option than using 2 stacked barlow lenses?

With a 5x barlow you'd be able to get a reflector with 3750mm of focal length giving a nice F/25.

Sorry if theses are silly boring questions  but I haven't the experience with scopes atm and I'm still reading around.

[Davey-T]

I don't think there is a "jack of all trades scope" which is why folks have more than one (six in my case) and I could do with a couple more.

I think stacking barlows quickly leads to dimmer and dimmer views, maybe better stacking powermates but then cheaper to buy another scope

Dave

[nightfisher]

I would say if you want to go with this idea, get 150 newt and 3x barlow, but keep it to a 3x

[Essex nightsky]

Its an expensive option but a cass with the hyperstar system is probably the closest jack of all scopes, use in "normal" mode for planets ect then add the hyperstar system for a shorter/faster focal ratio

[xtreemchaos]

i agree with Davey-t the less glass between your ep and mirror/lens cell the better.

[John]

The longer focal length scopes tend to have smaller central obstructions which helps with high power contrast and sharpness.

I guess a 5x Tele Vue Powermate might work OK ? - the optical quality of that would certainly exceed stacked barlows. Powermates tend to "dissappear" apart from adding the magnfication.

The mak-newtonian scope design is worth looking into. They seem to be a genuine all-rounder from the example I've owned. They are not low cost though and are heavy and take sometime to cool.

[Tinker1947]

When you start to magnify any views through a scope you will also magnify and errors that may be present, if you want to image then start looking at stable mounts......EQ8 and upwards......

[John]

When you start to magnify any views through a scope you will also magnify and errors that may be present, if you want to image then start looking at stable mounts......EQ8 and upwards......

Or a dobsonian. My dob mount seems to hold things pretty stable at 400x or more when I can use it. It's made from 18mm birch ply. Costs a lot less than an EQ8