Best aperture for planetary viewing

[Andrew*]

If you could choose only one aperture for the best views of planets, what would you choose, given typical UK seeing?

The theory goes larger scopes are more sensitive to seeing, but resolve more in the good moments, so what's the happy medium for you?

Andrew

[Andrew*]

I've voted "more than 10" owing to the consistently good views of planets through my 12" f/6 David Lukehurst.

Interestingly, there seems to be a very strong preference for 8-10".

Any comments?

Andrew

[ollypenrice]

I haven't voted because every time I use a different instrument I change my mind! When the 10 inch SCT is good it is very good. The 5.5 inch apo is very good far more often. Very occasionally the big Dob is the winner...

If I were to go for just one, I suppose the 5.5 apo.

Olly

[James]

I've voted 8"- 10". Whilst my 4" refractor will always give a really good view the Skymax 180 I'm using gives an excellent view most of the time and with increased resolution etc.

I know that if I was stuck with the 4" (what a hard life!) I'd always be hankering after the increased aperture...

James

[astro_al]

The largest aperture you own that is supported by your local seeing conditions on a regular basis. For me this is a 4" refractor.

[James]

Just realised I've done my sums wrong - the Skymax 180 is a 7" scope, not at 8" so I should be in the 6-8" category

[Andrew*]

I was going to say... Are you going to change your vote or shall I?

[James]

It'll need to be you as I can't change it

[Andrew*]

Done

Thanks all voters - most interesting!

Andrew

[RikM]

I've chosen 6-8" because the best planetary views I have had from home have been with an 8" f/6 Meade Dob.

The best view I have ever had though was through Astronut's SCT at SGL5.

[Andrew*]

Showing quite a clear trend here - a nice bell curve!

[Pete Presland]

i have gone 8-10" as well. this size does seem to be becoming quite a common entry level aperture these days

[Ad Astra]

I'll challenge anyone's 8-10" Newt to a 'Saturn Shootout' with my 133mm f/12 refractor... I've never seen a scope that small beat my Apomax!

Dan

[dweller25]

I've tried all sorts of scopes on the planets ....

4" APO

5" APO

6" Newtonian

7" Maksutov

8" Newtonian

9.25 SCT

10" Newtonian

My conclusions ....

1. The refractors give the 'nicest' images - sharp and contrasty.

2. Large central obstructions do not help with planetary views.

3. A good 10" Newtonian outperforms a 5" APO on the planets and is relatively cheap.

4. 'Poor seeing' can be overcome by putting a fan on the back of a newt to remove the boundary layer off the mirror surface.

BUT - the 10" Newt did my back in so I'll stick with the 5" APO.

HTH

[brantuk]

I used to think the Jupiter was brilliant in the SCT 8" till I saw it in clear seeing through the 12" dob

[Ags]

A trend I've seen on this forum is back injury.

Dweller25, you've done a lot of planetary sketching, so would you really say the 5" APO gets close to the performance of a 10" newt? I'm asking you because I've seen your sketches and you obviously pay close attention to the hard-to-see details on planets. I would have thought that going down to half the aperture would sacrafice too much resolution.

[dweller25]

AGS - the 5" APO cannot compete with the planetary views through a 10" Newt, but the 10" was too heavy for my bad back.

The 5" APO is the best compromise for me.

[Ad Astra]

My monster 133mm (5.25") f/12 is a bit over 22 kg -- so it's bad for the back AND provides excellent views.

The best of both worlds!

Dan

[dweller25]

Dan,

22kgs !!!!! - my 128mm F/8.1 is a lightweight at 9.4kgs - gives great views though

[Nexus 6]

I voted in the 8-10 range, my cpc 925 has, with the combination of a Televue 13mm Nagler, delivered some outstanding observations of Saturn at times this year.

[astroeddie]

I've gone for 10" and over.

Best ever views of the planets where with my old 254mm F5.7 Newtonian. Mirror from Oldham Optics. Amazing detail. I'm awaiting my 300mm F5 Dob delivery as I type.

Aperture rules

Eddie

[Moonshane]

if the poll is that were are only allowed to view planets then I'd go for my 6" f11 newt. this outperformed my 12" f5.3 dob on almost every occasion. it has more contrast, sharpness and detail on average.

BUT and it's a big but (I like big buts and I cannot lie etc....) when the good seeing really kicked in the 12" gave literally jaw dropping photo quality images with more brightness and sharpness in the best moments of seeing than the 6". it also of course showed more moons than the 6". you know, those views that make you gasp and make loud(ish) proclamations in the middle of the night and you start explaining to the cat 'how awesome that was'.

if we are allowed to include other objects (other than doubles and lunar) then of course the 12" wins hands down and if I had to keep one it would be the latter.

I am putting together a 16" f4 with 1/8 PV and strehl of 0.984. Although not a typical planetary candidate, it will be interesting to see how it compares on planets with the 6" and how I recall the 12".

I also have a 8.5" f8 mirror set and will be interesting to see how this performs when converted into a dob. not sure of the figure/quality of that though.

[Telrad]

IMO I think I'd have to say that depending on seeing conditions 120x to 200x on most Planets works well. But when Mars is worth looking at it seems that it requires a little more , say 200x to 250x . This is what I have experienced .

[haitch]

Well my 14" dob gives me better planetary views than any other scope I've owned (Helios 6" reflector, Meade 6" Achromat, WO Megrez 88FD). I think the Megrez could prove better than I've seen from it but I need to get some decent very short f/l planetary EPs. My shortest, a 7mm Nagler, only gives 71x in its 498mm f/l.

[Telrad]

IMO a good eyepiece for planetary is a UO Ortho 9mm giving 168x.