F4 Newtonian for Visual Observing

[jam1e1]

Hi, 

looking for some opinions / advice on F4 vs ~ F5 newtonian.

In summary, ive owned a F4.7 10" SW 250pds for a while and has served well, its a good compromise in my view with respect to aperture and over portability, comfort in EP height and coma. I'd been thinking of upgrading to an Orion Optics for a while, either a 10" similar spec VX10 at F4.8 or 12" VX12 at F4 due to same length. This will be mainly for DSO / clusters / PNs. 

Either way, at astrofest got offered a really good deal on 12" OO VX12 F4 with PV1/10 mirrors, so went ahead and purchased. Yes did get a bit of apeture fever  I didnt get a dob as want to mount on my Skytee2 or AZEQ6 mount.

As this will be for visual, appreciate being a faster system this will require a coma corrector / good EPs and already have a paracorr, so i'll be sending this off to them so the focal plane & position of focuser can be optimised.

Questions are, as F4 is quite fast:

- any other considerations to take into account in terms of views/brightness to expect

- would a ~F5 option be better for visual giving less coma? (adding extra length)

thanks

Jamie

 

[Stu]

There's no doubt f4 is fast, and will show you more coma than f5. Whether you find this a problem or not is really only something you can decide. A Paracorr or similar would be well worth investing in I think, if you like open clusters then you will want the stars sharp to the edge, and they won't be without one.

Given the fact that you want to use your SkyTee or AZEQ6, I think the f4 was the right decision for stability and ease of use.

Shane seems quite happy with his f4 scopes, but does use a paracorr.

[swamp thing]

8 minutes ago, Stu said:

 

Given the fact that you want to use your SkyTee or AZEQ6, I think the f4 was the right decision for stability and ease of use.

 

I agree.

F/4 + paracor and premium eyepieces is a great combo  

[Moonshane]

totally agree with the above. A f5.3 tube is a completely different animal to an f4 with the latter being a lot more manageable. That said, I would recommend a dob base rather than an altaz. I'd soon get bored of putting it on my Giro iii. I made my own dob base and it's a lovely set up. I find that with decent eyepieces (I use TV) the paracorr is worth it but not overly horrible without. I sometimes remove it to look at larger objects to squeeze that extra little bit of field.

if you are at SGLXI then I'll have mine with me.

here's the thread of my scope

 

 

[Peter Drew]

Nothing wrong with F4 for visual as long as the optics are good and well collimated. As already said it will place greater demands on the type of eyepieces and a coma corrector would be useful to improve the field characterisics. The brightness of of objects at the SAME magnification is governed by the aperture rather than the focal ratio.

[andrew s]

At F4 you will need very well corrected eyepieces for them to be "good" but that may be what you intended in your original post. Unfortunately, they are normally expensive!

 

Regards Andrew

[jam1e1]

thanks all for the responses! Glad to hear didnt make a mistake with this option  will post a review once received, circa April/May time

Ive got TV 12 and 17mm, rest are meade UWA 5k series- depending on how they perform may see about upgrading the meades

Shane thanks for link, unfortunately unlikely to be able to make SGLXI at this rate, though its definitely on my to do list so hopefully next one! Like your dob base, may give that a go depending on how get on with mount. Good to hear F4 is workable and not too extreme for visual - which was main point to consider

[estwing]

yup a paracorr is going to clean the view up nicely...and good ep's are where their quality comes into play at F4...or lower..congrats on the scope...clear skies!