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Planetary scope

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John

John

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What sort of budget do you have ?

The planets are a long way off and don't exactly fill the field of view even at 250x which is around the practical maximum with the sort of seeing conditions that we have.

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DirkSteele

DirkSteele

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Conventional wisdom would suggest you could go in one of three directions, which will be somewhat driven by your budget as well as where you might keep your scope.

The first option might be a long focal length Newtonian scope, which will have a small secondary obstruction which will help to avoid the degradation of low contrast features that scopes with larger secondary mirrors are seen to suffer from. Something like the Skywatcher 150PL which is a 6” f/8 scope (http://www.firstlightoptics.com/reflectors/skywatcher-explorer-150pl-ota.html ) and at £190 for the OTA, certainly a more cost effective option.

The second, more costly option would be a Maksutov. These instruments have very long focal lengths (often f/12 to f/15) and are known for being fine planetary instruments. The Skywatcher Skymax 150 Pro is a 6” f/12 scope (http://www.firstlightoptics.com/maksutov/skywatcher-skymax-150-pro.html ), which is around £509, and has a big brother (http://www.firstlightoptics.com/maksutov/skywatcher-skymax-180-pro.html ), a 7” f/15 scope at £765. The primary issue you may find with a scope of this design is the thick meniscus corrector at the front of the scope, which can mean a several hour cool down period before the scope will perform at its best. If you are able to leave the scope in place (such as garage or shed) where it will be close to ambient temperature, this would help mitigate that issue. The primary advantage would be the short tube, making it easier to handle, as well as putting less strain on your mount (dimensions as well as weight are a consideration when mounting a scope).

The third and most costly solution would be a premium Apochromatic refractor. For a scope of comparable size (6-7” aperture), you are limited to the premium manufacturers like TEC, Takahashi and APM and the 6” models from these manufacturers can run to £7-10,000. Perhaps a good “cheaper” alternative is the new Esprit series from Skywatcher. This is their attempt at premium line of scopes at a more cost effective price. While the quintuplet 100mm scope has not been so successful I have heard good things about the performance of the triplets. The Skywatcher Esprit ED 150 Pro Triplet (http://www.firstlightoptics.com/esprit-professional-refractors/skywatcher-esprit-150-ed-pro-triplet.html ) at £4,250 is, by comparison a bargain.

There are of course other alternatives. Some would offer up that a SCT with good optics can be a good planetary performer and I tend to agree, but others will voice concerns over the large central obstructions these scopes have. Certainly more aperture will help resolve more detail, but at a point, the atmosphere becomes the limiting factor. Another alternative would be to purchase a larger aperture Newtonian, which if you chose, you could stop down with an aperture mask to create a very long focal length instrument with no central obstruction, leaving you a good light bucket should you decide to go deep sky hunting as well. Others have questioned this though as it could be argued that just having some extra aperture will help tease out those extra fine details in moments of super tranquil seeing.

I am sure many SGL members will be able to offer alternative views and suggestions of scopes, but hope this gets you started.

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Laurie61

Laurie61

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I was in a similar situation albeit in 1979. Not the choice of affordable scopes back then as there is now but the basic problem of how much aperture will give you useful Mag and resolution for planetary viewing are still the same. I settled on an 8.75in f7.3 Newtonian after some head scratching. Enough aperture and focal length to be seeing limited on many nights but with the ability to comfortably use up to 300x on the few good nights and with targets well placed. So a scope in the 8-9ish inch range and then decide on the most suitable type for your circumstances. SCT/MAK for a compact design, Newtonian, or a refractor if you are happy to spend the extra. If you are using high Mag then a decent mount and tracking ability make the experience more enjoyable so be aware that you will need to budget for this if you don’t already have something suitable.

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recceranger

recceranger

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That's really great feed back and advice. I am attending the IAS with the Mrs this Sat. Two things will come out of this show, advice from various quarters and my line in the sand from Mrs S!

Think I'm leaning more and more towards the MAK 180 from Sky Watcher. In the budget zone but I am tempted to push for a 12" dob with GOTO. All will become clear this weekend.

Thanks Guys,

Rick

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kerrylewis

kerrylewis

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I too am interested in the planets although I wanted any new scope to be a god all-rounder too. I have a 100mm refractor and I like the fact that it is straightforward with no collimating. But the aperture is clearly a limitation and once you go over 100mm the cost of fracs rises exponentially. So, after a lot of thought and with a target budget of less that £1,000 I went for the Celestron 9.25 SCT I am absolutely delighted with it. It is clear now that the limiting factor is seeing and not aperture. With a couple of good Televue eyepieces I have had the best views i have experienced of Jupiter of Saturn since I got the scope in Feb. The focal length also means that you can get the highest magnification that the seeing will accommodate. Having recently retired I wanted a scope (and since then a mount) which I would not need to upgrade again and now I think I have it. Although I have heard that there is no known cure for aperture fever!

So - I would recommend a Celestron SCT with the most aperture that you can afford (and handle).

Kerry

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scarp15

scarp15

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Rick, the 300p is quite capable at yielding some very good views on the planets, although at F4.9 it will require high quality eyepieces (Personally though, I prefer to use quality e.p's with my C8 too, such as T.V plossl's). However if your question was - Scope for Globular Clusters, then a 12" Dobsonian, if used at a dark location, as I am discovering, (at high power) provides some quite stupendous views of subjects such as M5, M3 etc.

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faulksy

faulksy

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as said the maks are very good for planets but have a very narrow field of view so if your only using/buying 1 scope then its worth thinking this over. if you like the compact ness of the mak then a sct would be a better choice

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recceranger

recceranger

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So the cool down of a MAK isn't an issue for me. The 180 has better aperture per quid than a 6" Frac (especially an APO!). I'm assuming then that the MAK 150 or 180 will give a better image for planetary visual?

Really wish I had time prior to the IAS this weekend to take a look through a few differing scopes (Mak's, Frac and 8 - 10" SCT's). Alas the weather, arrow of time and my own unique ability to leave everything to the last safe moment has made this impossible.

In short I will make a call when I take a look via a few dealers and also some sound advice from a few advanced members attending the show.

Thanks all for your replies.

Rick

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nightfisher

nightfisher

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I have the HEQ5 ready to go for the new scope. Do you have any mods on the MAK or is it good as?

Rick

I fitted a revelation dual speed crayford focuser, but this is not in any way vital and i converted my 180 to tube ring mounting, you will also need a good dewshield, there are some pics of my one in equipment gallery

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