telescope for planetary suface

[Josh Wilson]

Refractors just can't beat a Dob in aperture to cost ratios (if such a thing exists). The Dob does have the central obstruction which cuts prob an inch off the advertised aperture, but the you'll still be left with more aperture than a frac. I can't say I've seen a frac over 5" (120mm) for a good reason- they cost bucket loads and an APO that big is even more. I really don't mean to start a fight here but that's just what I have to say about fracs vs. Dobs as far as planetary observing.

Back to the orig. topi: As you can see, the majority of members have suggested scopes that near your maximum budget. I'd agree with many of the suggestions but I'd ask that you not forget the other half of purchasing a scope- an eyepiece. Since planets have more light to use, you can get more magnification without a huge loss of detail. With a 6" (150mm) scope you can reach up to around 300x. I'm not sure what EP you'd need to get that but I assume its around 7 to 5mm. You can get an average eyepiece for an average price but remember you get what you pay for. I recommend you expand your budgt a little to accommodate for an eyepiece or two. I cannot suggest what eyepiece you should get because I don't know the true quality of EP's over in the UK. Maybe someone else can though.

Josh

[John]

.... I cannot suggest what eyepiece you should get because I don't know the true quality of EP's over in the UK. Maybe someone else can though....

I agree about allowing for a couple of decent eyepieces and £80-100 or so will be needed for that.

We have pretty much the same choice of eyepieces that you have in the USA Josh, with one or two exceptions. The pricing here is a bit more than you pay in some cases though.

[Astro_Baby]

Its probably worth mentioning that planets dont show much surface detail almost irrespective of scope size available in the amatuer market.

Mercury shows as a small white dot, Venus shows as a larger white dot sometimes as a crescent, the moon shows lots of surface detail of course but then moving ouwards you have Mars which shows mostly as a small orange dot with white polar caps if your luckyand seeing is good. Youmight just make ou some darker areas. Jupiter shows a couple of cloudbelts, the red spot ( whichis actually more grey and the odd ripple in the cloud belts plus shadow transits of its moons.

Neptune and Uranus show as small green or green/ blue dots and Pluto would show as a small white dot. Without GoTo you would peobably struggle to find Pluto ( you might even struggle with it to be honest) and you might struggle with Neptune and Uranus too unless seeing is good or they are placed near some other unmistakable object.

I just raise this in case your thinking of seeing things like NASA put out.

On the budget you have I would sugget the 150 refelector at f8 on an EQ mount.

[Scott]

I prefer eq mounts as tracking motors mean (for me) the viewing experience is more pleasant (an English teacher I am not). However, I also have a small dob which gets loads of use with these patchy nights. For £300 I wouldn't look at anything other than a http://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-200p-dobsonian.html. just my opinion for what it's worth

Scott

[Scott]

Its probably worth mentioning that planets dont show much surface detail almost irrespective of scope size available in the amatuer market.

Mercury shows as a small white dot, Venus shows as a larger white dot sometimes as a crescent, the moon shows lots of surface detail of course but then moving ouwards you have Mars which shows mostly as a small orange dot with white polar caps if your luckyand seeing is good. Youmight just make ou some darker areas. Jupiter shows a couple of cloudbelts, the red spot ( whichis actually more grey and the odd ripple in the cloud belts plus shadow transits of its moons.

Neptune and Uranus show as small green or green/ blue dots and Pluto would show as a small white dot. Without GoTo you would peobably struggle to find Pluto ( you might even struggle with it to be honest) and you might struggle with Neptune and Uranus too unless seeing is good or they are placed near some other unmistakable object.

I just raise this in case your thinking of seeing things like NASA put out.

On the budget you have I would sugget the 150 refelector at f8 on an EQ mount.

hmmm, now you've got me doubting my own post

Scott

[SkyGibbon]

Have to agree on the f8 dob. Might pick one up myself, even though my 10" f/4.7 does great on planets with some es 82 degree eyepieces. Just wanted a longer focal scope and I love dobs.

[Astro_Baby]

hmmm, now you've got me doubting my own post

Scott

Well dont, we are all different, it would be dull if we werent

[Marki]

As a user of a 10" Dob with a reasonable mirror for all-round work F6.4 I can assure all that following planets through a nudge from time to time is easy and the secondary mirror on an F6 or longer Newtonian is small enough to avoid contrast loss. On an F8 lunar and planets will be great.

Aperture resolves fine detail and in the UK skies the brief glimpses of steady seeing deserve aperture to provide the detail.

I have a TAL100 but it does not compare to the Dob on the planets unless the LP and seeing is so poor that I don't bother with the Dob, which isnt that often thankfully.

The TAL used to be on an EQ mount but it is now AZ4 Alt-Az and is so much easier for planets / lunar and doubles.

+1 vote from me for the 6" F8 Dob.

4" achro frac v 10" dob is hardly a fair comparison , but your general point is well taken. On the op's budget maybe the 150mm f8 dob is best