Is 250X Too Much For The Uk?

[dharma66]

My new scope will be arriving in a couple of weeks. It's going to be a 12" f/1500 dob, and I'm starting to plan on a couple of extra eyepieces, initially to perhaps fill the gap between the supplied 10 and 25mm, and almost certainly to go shorter than the 10mm.

At the moment, after reading reviews, and investigating some stats, I'm coming down on Delos as being a fair choice. Depending on reviews when it actually hits the shelves, I'm thinking an 8mm, giving around 188x would probably get some good use.

What I'm wondering is whether a 6mm, giving 250x is just too much for the UK? I'm in the 'burbs of Manchester, and wouldn't expect to get much use out of this from my back garden, but I'm a short drive from some better viewing locations up on th'ills. Would 250x still be asking too much of UK viewing conditions to make this a worthwhile purchase? Maybe I should look at something like a 7mm Nagler sitting between the two?

[Stephen]

Once in a while you will certainly be able to use it, but I wouldn't suggest you would get regular use with it

[John]

I used to be pretty conservative when giving advice about using high magnification but I've been finding 300x / 350x working pretty well on the right objects over the past few nights with a 6" refractor during patches of good seeing. The objects in question have been Saturn, Mars, the Moon and close binary stars. The caveat I'd add, apart from being guided by the seeing conditions, is that the scope needs to be in pretty good collimation and the eyepieces of decent quality.

[Space Bat]

It's not an unusable magnification - but the seeing has to be good to exceptional to get the full appreciation from it. I have used high magnification on occasion and this tends to be lunar or planetary use....but also close doubles...also useful for collimating....

[sgazer]

Presumably mainly for planetary use, I found 250x fine on nights with good seeing. The main problem might be tracking the dob at that magnification, depending how skilled you are.

[LukeSkywatcher]

Once in a while you will certainly be able to use it, but I wouldn't suggest you would get regular use with it

I agree. 200X is the norm. On rare occasions you can push it towards 250x.

[Mike73]

How about getting 14mm Delos and Barlow or Powermate if you could stretch it? That would give you x107 and x214.

If you wanted to play it safe you could go for a 16mm t5 Nagler, x83/x187.

The stock 25mm isn't that bad and by going for something like the above you'd have a good range covered.

[Damo636]

I have a 12" dob and do find I can use that much power surprisingly often. I had been using a 10mm eyepiece in an Antares 1.6x barlow to achieve 6.25 fl/240x mag but bit the bullet and bought a 6mm Delos at the weekend.

[Mike73]

I have a 12" dob and do find I can use that much power surprisingly often.

I've found the same, I'm not too worried about using a x2 barlow with my 13mm Ethos when I get it.

[dharma66]

Many thanks for the replies all. Good to hear that this kind of magnification is at least occasionally usable!

This is indeed what I'm thinking of for planetary use. I'm not too worried about tracking at high mag, as I cheated and ordered a dob with electrickery bult in.

I'm also wondering now whether, rather than an 8 (as well as the six - the thinking being an 8 would be more often usable at 188x), maybe it'd make more sense to go for the 17.3 plus Barlow/powermate, giving 87/174x?

That would also equip me with the Barlow/pm, giving me 12.5 and 5mm from barlowing the supplied eyepieces. Can't imagine 5mm being useful very often at f/1500, but at least it'd be there for that elusive 'perfect night'!

That would just leave me with the other end to think about. I fancy something with a nice, wide true field. The 41mm Panoptic offers the maximum possible field stop, and a true field of 1.76*, but at f5, would have an exit pupil of 8.2mm, which is perhaps larger than ideal? Would I be better with something like a 31T5 Nagler, offering 1.6*, but with a 6.2mm exit pupil?

Sorry about the long list of questions. This is the last one.

Does anyone use, or feel the end to use, a paracorr with the Delos (or Ethos, I guess) eyepieces in an f5 scope or thereabouts? If so, I may have to have a bit of a rethink, as I believe that would effectively lengthen scope FL by about 15%, with corresponding increase in mag and field reduction. 15% on top of 250x would push it to something like 287x, which is surely starting to push even 'very good' UK seeing?

Thanks again for all your input.

[Damo636]

The 17.3 Delos/Powermate would be a good option as you would have a good workhorse fl and with the PM a useable on most nights 8.65mm/173x. The Powermates are simply superb and the only reason I sold mine is because I prefer the unbarlowed approach, simply because its less juggling expensive glass in the dark. The 31mm Nagler would be a better option than the 41mm Panoptic for the reasons you mention. I personally don't use a coma corrector at f5 and don't find the coma bothersome

[dharma66]

Brilliant, thanks Damo

[michael.h.f.wilkinson]

I often go well beyond 203x (10mm Radian). I use my Pentax XF 8.5mm a ot (239x) a lot, and want to add an XW 7 for 290x, which I got with my old UWA 14 plus TeleXtender (very much like the powermates). As I now have a 12mm Nagler, I really miss the 7mm focal length. At this kind of magnification, you do not see sharp all the time. In stead, you wait for the moments of stable seeing. The views during those fleeting moments are great.

For most other objects, 170x is about as far as I go (169x actually, with the 12mm).

[dweller25]

I also live in the burbs of Manchester and regularly use x250 on the planets with my 8" Dob - more if seeing is excellent....

[Mr Spock]

I find with my C925 the 10mm, x235 is the workhorse.

Most nights on the moon I can use an 8mm, x294. Jupiter used to top out at 9mm, x261 regardless.

On a few rare nights I can use a 6mm, x392 on the moon and the image is razor sharp. I would use that or a 7mm on doubles.

[dharma66]

Thanks everyone, this is sounding very promising for a nice short eyepiece or two

[swamp thing]

I used to be pretty conservative when giving advice about using high magnification but I've been finding 300x / 350x working pretty well on the right objects over the past few nights with a 6" refractor during patches of good seeing. The objects in question have been Saturn, Mars, the Moon and close binary stars. The caveat I'd add, apart from being guided by the seeing conditions, is that the scope needs to be in pretty good collimation and the eyepieces of decent quality.

I agree with John I regularly use high power with my scopes. That's the whole point of getting aperture, to get the bigger image scale so you can pump it up. I regularly used 300x - 350x on DSO with my 16", sometimes more.

It's very easy to get caught up in the low power for DSO school of thought, with aperture you don't need to. That's why we buy the wide field eyepieces. 150x -200x can be used easily on Galaxies through big scopes, sometimes more. Only the huge M31 needs low power to fit it in. Eg M101 is only half a degree accross so as long as your eyepiece covers this then go for it. You'll be surprised how much detail high power coupled with large aperture can drag out.

[Moonshane]

It really depends what you are looking at I think and where in the sky it is.

Some examples (from light polluted skies near Manchester):

Moon - From time to time, I can use 400-500x on the moon with a 6" scope (some tell me this is not possible but my scope clearly does not know this) or my 16" scope masked to 170mm (occasionally unmasked if the seeing is good to excellent) but only when the moon is relatively high in the sky. I can use 200-300x routinely on the moon. When it is lower down towards the horizon then the magnification needs to be lowered as the seeing is terrible.

Double Stars - I find that the same rules apply as for the moon. Close doubles sometimes need a lot of magnification or aperture to resolve. With doubles you are not looking for detail, just the ability to split. Accurate colours help and again the apochromatic nature of reflectors helps this.

Planets - (really Jupiter, Mars and Saturn) - I rarely use more than 200x but for Mars often 300x is needed to see any real detail. I have had seeing conditions where I can barely use 100x. You don't see much more detail at 200x plus than at 150x except on very rare occasions.

Faint fuzzies - often a smaller magnification helps to initially pick out the galaxy or what have you and you can then switch to higher. I find that 150x is often optimum for galaxies but not always. Nebulae are often larger and more diffuse, needing a filter or larger exit pupil (less mag) to see well. Planetaries need the same sort of treatment as planets.

Clusters - globulars really benefit from aperture and moderate magnification (maybe 120-150x) but open clusters often need wider views.

Hope this helps but in short, yes you'll use it although when I had a 12" f5 dob, the 'magic' number was 9mm giving 167x as this provided the most consistently good images of most targets.

Re the Paracorr, I don't feel the need for it at f5 but it's definitely beneficial at f4 and I use it routinely in my 16" f4 scope.

[alan potts]

I agree with Moonshane,

I have a 12 inch but different type SC, I can't remember the last time I sat for any length of time with more than x200. My sky is so dark I cant find the scope if I go indoors and come back out, sometimes it is nice to have a moon, I don't fall over things. I think that 250x is fine some of the time, but I wouldn't want to spend a lot of money on a eyepiece to get it just for the sake of it. I would barlow to this or powermate if I didn't have an eyepiece. I don't seem to see anymore with magnification, for me it works better on the 115mm refractor than on the LX 200.

Even though I have an eyepiece that will give me close to the maximum on the 12 inch I have never evn tried it.

Alan.

[alan potts]

I have just read all your post in this section, maybe there is something wrong wit either me or the LX 200. I cant see any detail on anything at 350X plus other than the moon. I do think that the air here in Bulgaria being hotter is more turbulant in summer.

Alan.

[michael.h.f.wilkinson]

If your LX 200 does not show detail at 350x you may need to check collimation. Furthermore, ensure that the scope is at ambient temperature, to avoid turbulence within the tube (tube currents often show up well in out of focus star images). Seeing might of course be a problem, but it is wise to rule out other possibilities.