12 replies to this topic

[lemarr7]

As i said in topic GSO 10 inches [254/1000] f3,9 with homemade dobson for visual. I heard that scope need good eyepieces and perfect colimation. What else should i know before buying?

[DouglasPaul]

Well, it's big. And it's heavy. Also, you didn't state how much money so it's kind of hard to give an opinion.

[sg6]

Also doesn't say where they are and in some parts of the world scopes are expensive and harder to come by.

[Tangerman]

Correct me if I'm wrong, but I was under the impression that GSO made f3.9 scopes for astrophotography. That just means you'd need an extension tube to get eyepieces to focus properly. The GSO f4.9 10 inch scopes, whatever the rebrand, are probably going to be easier to use and a bit better for visual, with a smaller secondary mirror.

[lemarr7]

Price is 470 usd . I live in Poland. Scope is near me [50 km]. This is advantage . Usually 10 inch scope is 250 -350 km from me. Price this scope its  a little more than my monthly earnings , so its much for me. Thanks for posts.

[lemarr7]

Extension tube 35mm is included. Secondary mirror is bigger?  How much bigger compared GSO 10 f4,9?

[DouglasPaul]

I wish I could be more help. It sounds like it's pretty hard to acquire a telescope where you are. Hopefully someone can chime in on how that OTA will do for visual observing with the extension. I have no experience with a scope that fast.

Edited by DouglasPaul, 01 March 2021 - 01:02 PM.

[SeattleScott]

At F4 a coma corrector is pretty much required. At F5, some people insist on coma corrector and some don’t bother. Has a lot to do with what eyepieces they use.

F4 newts are really intended for imaging. You can use them for visual. I have an 8” F4 that I use for visual. The secondary ends up being a bit bigger, but about the same size or maybe slightly smaller than a SCT so really not a huge deal for visual. It just won’t be a planet killer. Like most SCT.

The real issue is the collimation, coma and need for very good eyepieces to get good views at F4. Especially if you want wide angle eyepieces.

Scott

[maroubra_boy]

Lemarr7,

 

I actually have TWO 8" f/4 Newts.  One is a solid tube that I made a dob mount for, and I can remove the OTA from the dob mount and use it on an equatorial mount.  The other is a truss style scope that is also on a dob mount, and the whole thing packs down into a small case, which is the mount itself.

 

Don't be too concerned about the larger secondary that f/4 scopes have compared to and f/5.  As Scott said, it is not a big deal for visual.  If the mirror though is a good one, it can still do a good job with the planets - some of the most satisfying views I've had of Jupiter and Saturn have come with these scopes.

 

I won't double up on what Scott said.  I will add do not be concerned about collimating these scopes.  I find the process no different from doing this with my other Newtonians of f/4.5 and f/5, and the process takes me only 2 minutes - it is only minor tweaks that ever needs to happen.  "Collimation" is only the term used to align the mirrors, nothing more.  It is not difficult.  You check it when you have finished setting up and you will then know that your scope will be performing at its very best for you.

 

A 10" f4 scope is a great visual instrument.  Not too heavy so should not have a problem taking it to and from an apartment if that is where you live.  It will serve you very well for many years

 

Alex.

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[Tank]

Love the F4s you get WF and aperture
I would recommend a laser collimator

[lemarr7]

Love the F4s you get WF and aperture
I would recommend a laser collimator

I havent  bougth it yet. I dont have good eyepieces for this f4 scope .Only kellner 25mm and 10mm, plossl 6mm , erfle 42mm 2 inches but that eyepiece give me in this telescope exit pipil 10-11mm! What should i do? I dont have much money for expensive eyepieces.I wont see anything because of the cheap eyepieces?

[CowTipton]

For a beginner I would recommend a slower scope.

[SeattleScott]

Basically you will be able to see stuff in the middle but the edges will be messy. Have you watched Star Wars or Star Trek? Remember how the stars especially around the edge get stretched when they jump to warp speed? That’s sort of how stuff would look through the scope. Especially without a coma corrector.

You would also need a collimation tool of some sort.

If you are happy with 50-60 AFOV the eyepieces don’t have to cost a fortune. The real issues arise if you want 70, 80, 100, 110 AFOV. That’s when it gets expensive. Still most of your current set will struggle at F4. Although they are narrow so might not be too bad. But I would consider a collimation tool an absolute must right away, and a coma corrector sooner rather than later.

Scott