Sky-Watcher Explorer 150P DS OTA

[enigma]

I am thinking that a 6" f/5 Newtonian with a 2" focuser might make a nice wide field instrument and the 150P DS OTA is described as having a 1.25"/2" Dual-Speed 10:1 ratio focuser, but also a shorter tube with the secondary mirror positioned closer to the primary mirror. Does this mean that it has a bigger secondary mirror which might be a disadvantage for visual use?

[Deneb]

I believe the secondary size is the same size as the Black Diamond 150P, if you want a larger secondary, you may want to go for the 200P DS model...

Nadeem.

[enigma]

I don't want a larger secondary, but if it is the same size as the 150P, how can be positioned closer to the primary mirror?

[pook]

It's the same secondary... just moved further down the tube. This allows the focal point to "stick out" of the draw tube further, to allow easier focusing with DSLR and web cam prime focus attachments.

One problem with some newtonians is not having enough back focus to use with a camera without an eyepiece, and the DS version addresses this by moving the secondary further down the tube.

As the normal 150p can focus a DSLR I fail to see the point to be honest, but I suppose you can mount a DSLR on a wider range of attachments with the DS version.

It's still worth having for the 10:1 crayford IMO.

[Whippy]

The 'DS' models do indeed have more back focus, but it's primary that's moved up the tube, not the secondary further down.

IIRC, Ant had a 150P and he had modify it to get his DSLR to be able to use it, but I think that had something to with using a 2" focuser which they didn't use to to have. FWIW, some CCD's need to have lots of back focus, especially when you have filter wheels, come correctors and the like involved.

Good scope though, I've got one that I'm reviewing and so far it's doing what I've asked of it .

Tony..

[enigma]

Would there by any issues if using the150P DS visually? Its more compact tube and better focuser seem to justify the extra cost.

[pook]

T

IIRC, Ant had a 150P and he had modify it to get his DSLR to be able to use it, but I think that had something to with using a 2" focuser which they didn't use to to have. FWIW,

Yes. Mine has the 2" focuser, and can focus a dSLR with room to spare.

[Whippy]

Would there by any issues if using the150P DS visually? Its more compact tube and better focuser seem to justify the extra cost.

Not to my knowledge. I think if you're thinking about imaging, then the DS is the one to go for. But if you're not then save your pennies .

Tony..

[johninderby]

You could always put a 2" crayford on the regular OTA. The crayford fitted to the DS is still a low end one and you can get better but still not expensive ones.

I put a 2" crayford my 150PL planatay OTA project (1/12PV OO mirror etc.) and it was a fairly simple job, although the focuser hole in the OTA had to be enlarged.

John

[enigma]

I used to own a 6" Newtonian and I could not find a focuser replacement with a reasonable cost that would fit without any modifications. Does anyone know what would be the maximum true field of view with the 150P DS (or 150P) using 2" eyepieces?