Nexstar 4SE: Buying Eyepieces, but do I need filters?

[jweaver]

I am an absolute novice who has just bought a Celestron Nexstar 4SE.

I have been reading 100s of posts on various forums over the past few days and its clear that I need some more Eyepieces..

I have decided on the GSO/Revelation set and had decided on this:

Revelation Photo Visual Eyepiece Kit

It seems to have everything I need, plus it gives me the option to connect my SLR (assuming I buy the necessary adaptor).

But just as I was about to order, I found this for £31 less:

GSO 8 part Photo-Visual eyepiece and accessory kit by GSO

It seems to be exactly the same kit.. You can even see the "eve" of "Revelation" on the lid.. But it doesn't have the filters.

So my questions is easy.. Do I need filters? Which set represents the best value considering my model of telescope and level of experience.

Jon

[MorningMajor]

I'm certainly no expert and I'm sure someone more qualified than I will come along soon, but I have bought a polarising moon filter (you can adjust how much light it filters) for my scope and it is fantastic when viewing the moon - especially when it's full as it really is too bright to be comfortable in that state

[great_bear]

You absolutely don't need filters.

- except a moon filter, which is included in the cut-down kit.

With this scope however (I have something similar) you ought to consider separate eyepieces rather than an eyepiece kit.

(LATER: I also ought to mention that I have that exact, filterless eyepiece kit and I don't use it at all with this scope)

[Nexus 6]

Have to agree with above comment, a Moon filter is a must, you should try a local astro society if possible, then you may be able to try some various ep's before you spend anything, so getting a good 2 or 3 rather than a set of 4 or 5 for the same money may be worthwhile, just an idea.

[jweaver]

Thanks all... You are probably right about the eyepieces.. But after looking around, I get the feeling that most people think that the "kits" are such good value, as they cost the same as 2-3 filters.. And since the Revelation/GSO ones are fairly good, its a bit of a no brainer.

As for my question asking do I "need" filters.. I should I have really asked "can I use" filters.. At the end of the day, the kits are £31 different in price.. And the difference is 4 filters, which would cost about £30-£40 to buy separately..

So I am not really saving much buying the kit with the filters, when I could buy the filters later...

Jon

[Steep]

I don't think you'd get much use from the filters there, as others have said a polarising filter for the moon is about all you'll need and even then only when it's full and bright.

As for the kit, it's your decision but my advice fwiw is to buy the best eyepieces you can afford, the eyepieces in the kit are unlikely to be much better than the supplied ones. Maybe consider a good quality zoom (add about 50% to the kit price for one) or buy one at a time of the sizes that suit you best, saving up in between.

[jweaver]

I don't think you'd get much use from the filters there, as others have said a polarising filter for the moon is about all you'll need and even then only when it's full and bright.

As for the kit, it's your decision but my advice fwiw is to buy the best eyepieces you can afford, the eyepieces in the kit are unlikely to be much better than the supplied ones. Maybe consider a good quality zoom (add about 50% to the kit price for one) or buy one at a time of the sizes that suit you best, saving up in between.

Thanks.. My scope came with a Moon filter, so I am sorted there.. And if I do go down the kit route, both come with a Moon Filter..

I will do a bit more reading, but It think that if I do decide to go down the 'kit' route, I will get the cheaper ones without the filters.

Thanks again.

Jon

[cgarry]

I bought that set, played with the filters once and never looked at them again.

Cheers,

Chris

[jweaver]

I bought that set, played with the filters once and never looked at them again.

Cheers,

Chris

Good to hear.. That certainly helps.. But more imporatntl, since you bought the kit.. Whats your thoughts on them for someone like me? Is it a good starting point, or as other posters have said, am I better off spending the money on better, individual items.

Jon

[Doug]

Hi Jon

Just to let you know, there are different filters , some are just colourful blues greens ect and then there are ones that let you see nebulae and galaxies and cost between

£40 to £180.00 for ones at a good price are at the top of the page from First Light Optics Baader are a good start

Doug

Essex

[cgarry]

Good to hear.. That certainly helps.. But more imporatntl, since you bought the kit.. Whats your thoughts on them for someone like me? Is it a good starting point, or as other posters have said, am I better off spending the money on better, individual items.

Jon

I thought they were a very good starting point and the 32mm EP in the kit is really nice. However I replaced them one by one so they don't get used any more. If I were to do it again I doubt I would buy the kit again, I would buy a nice high power EP and nice low power EP and build up a collection from there.

Chris

[jweaver]

I thought they were a very good starting point and the 32mm EP in the kit is really nice. However I replaced them one by one so they don't get used any more. If I were to do it again I doubt I would buy the kit again, I would buy a nice high power EP and nice low power EP and build up a collection from there.

Chris

Many thanks for that... So my next question is how much would a "nice" high and low power EP be?

The thing I like about the kit is that it immediately gives me the option to play with some photography. I am not really interested in using the scope to take photos as I am sure it will be disappointing, but since the kit gives me everything I need, I will automatically have the option.

So its seems like a lot of bang for my buck..

Jon

[Debostar]

I have ordered a moon filter and also a light pollution filter...The moon filter is a must for lunar observing during brighter moon phases, the LP filter may come in handy if your observation point is near street lamps and other strong man-made light sources...I am anxious to try out mine...

[cgarry]

Many thanks for that... So my next question is how much would a "nice" high and low power EP be?

Jon

That is a tricky question without an easy answer. But having said that...

For a high power EP consider the TMB clones. They are very well regarded and cost less than £40 delivered new:

1.25" Eyepieces

For low power, again it depends on how much you want to spend. The 24mm TeleVue Panoptic is stunning and so is the price, but there are many excellent widefield EPs to be found much cheaper.

This is an interesting thread on the subject:

http://stargazerslounge.com/equipment-discussion/131324-year-bargain-eyepiece.html

In fact there are many many threads to read on the subject of EPs, and you can always start your own!

The thing I like about the kit is that it immediately gives me the option to play with some photography. I am not really interested in using the scope to take photos as I am sure it will be disappointing, but since the kit gives me everything I need, I will automatically have the option.

So its seems like a lot of bang for my buck..

Jon

Yes I agree, the kit is not bad value and does give you a complete set of usable EPs for a good price. If you are the kind of person who will not feel the need to constantly buy new EPs (a rare breed I believe) then this kit will easily serve you well for years.

Cheers,

Chris

[great_bear]

OK, there are some interesting points on this thread, so I will address them as best I can, one by one:

the eyepieces in the kit are unlikely to be much better than the supplied ones.

Actually, it must be pointed out that this is not the case. The Plossls in the Revelation/GSO kit are very high quality Plossls indeed with a nice, solid build quality to them. For scopes of F6 and above they are excellent and whilst Tele Vue Plossls have more detail in their design, in slower scopes there's not much difference optically between Tele Vue and Revelation/GSO Plossls - the main difference being that Tele Vues are corrected down to F4.

I get the feeling that most people think that the "kits" are such good value, as they cost the same as 2-3 filters.. And since the Revelation/GSO ones are fairly good, its a bit of a no brainer

(in the above I assume you meant "eyepieces" not "filters" as a typing error! )

What you say is true enough and actually, I'd recommend the kit if you had (say) a 130P as your telescope (another scope I have - and have used the eyepiece kit with quite extensively). However, you don't have a 130P - you have a 4SE - a slow scope that makes the Barlow in the kit redundant, and the spread of focal lengths (IMO) less useful than might initially appear. You'd be better off with an 8mm TMB Designed Planetary (£36), an 18mm BST Explorer (£38), and a 32mm Meade Plossl (£42)*

Here's why (in my opinion):

With a 130P (or similar F5 scope), every eyepiece in the Revelation Eyepiece Kit is useful to some degree, and the Barlow additionally provides 7.5mm, 6mm, and 4.5mm focal length that are equally useful as well. The Barlow can also be used with the 32mm and 20mm eyepieces to provide 15mm and 10mm focal lengths with less astigmatism than the dedicated 15mm and 9mm tend to show in fast (F5) scopes.

The above - with a 130P - works quite well as a system because you've got a spread of Barlowed, planetary lengths, but also a nice spread of lengths all above a two-millimetre exit pupil - so you can get a nice range of rich, bright, star-filled views to enjoy.

But those of us with long focal-length catadioptric scopes live in an altogether darker world (literally). In my experience, there's not much point in having more than just four focal lengths with such a scope:

1: Maximum possible magnification

2: Slightly backed-off magnification for poor conditions

3: Wide view at the lower limit of DSO brightness

4: Minimum possible magnification

An 8mm TMB Designed Planetary pushes the scope to its maximum magnification, and provides amazing planetary and lunar views. I know this, because I use one with a 105mm Mak similar (if not optically identical) to yours. Some might think it pushes the magnification too far, but it really doesn't; views of the moon are still crisp and have impressive depth of detail. You'll love it.

An 18mm eyepiece such as the BST Explorer, is about as dark as most people would want to go for DSO viewing with your scope, and also provides a nice whole-disc view of the moon, and also shows Jupiter and Saturn with their moons in context.

A 32mm Plossl eyepiece like the Meade 4000 (a cut above the Revelation one - albeit slightly) provides the brightest views that your telescope can provide and will probably spend a great deal of time in the focuser.

As for my question asking do I "need" filters.. I should I have really asked "can I use" filters.

Yes, that was understood I think. I had coloured filters for a while but in the end I sold most of them off, because they offer such little benefit compared to the extra faff in using them. You're best off just settling in and concentrating on the planetary view - you'll see more by observing carefully than by swapping filters in and out.

The only filters I have left are:

- An orange one (for viewing the moon during daylight)

- A deep red #29 one (for viewing the moon whilst preserving night vision)

- A polarising moon filter (only used with my largest scope)

- A Orion Ultrablock (for nebula viewing)

The thing I like about the kit is that it immediately gives me the option to play with some photography. I am not really interested in using the scope to take photos as I am sure it will be disappointing

Actually - with some skill and practice, it should be possible to get some great photos with the scope as-is, and world-class photos with a better mount. But bear in mind though that you don't use eyepieces (at least not usually) during astrophotography - and the kit's T-adaptor which merely lets you attach an SLR directly to the scope is only about £12 to buy. There's probably even folks on the forum who'd send you one for free if you asked

Admittedly there is one eyepiece in the kit that is designed specifically for astrophotography - and that's the 32mm Projection Eyepiece. It is a very nice eyepiece IMO, and I particularly like its adjustable eye-relief feature.

For low power, again it depends on how much you want to spend. The 24mm TeleVue Panoptic is stunning and so is the price, but there are many excellent widefield EPs to be found much cheaper.

Actually, above 20mm there are surprisingly few on the market. The 24mm Meade SWA (whilst stocks last) will be almost as good as the Pan in a slow scope - and for about half the price, then of course there's the Baader Hyperion 24mm too - but that's about it really. I can't think of anything else 68deg in a 1.25" barrel at that focal length.

Anyway, hope the above helps in some way.

Note: *The 8mm and 18mm can be got from Sky's The Limit, and the 32mm Meade Plossl from First Light Optics

[great_bear]

Just to let you know, there are different filters [...] there are ones that let you see nebulae and galaxies.

Yes but I should add that whilst I mentioned such a filter - the Orion Ultrablock - in my previous post as being a filter that I use, I must also point out that on a very slow scope, this type of filter really has very limited use indeed: Looking at M42 and... erm... that's about it...

The problem is that Maks tend to facilitate a maximum exit pupil of only about 2mm, and you really need quite a bit more than this in order to push enough light through a narrowband filter during visual use.

[MorningMajor]

Very interesting post great_bear - worthy of a thread of its own - thanks

[cgarry]

For scopes of F6 and above they are excellent and whilst Tele Vue Plossls have more detail in their design, in slower scopes there's not much difference optically between Tele Vue and Revelation/GSO Plossls - the main difference being that Tele Vues are corrected down to F4.

I would like to second this. I have some Tele Vue Plossls which match those from the Revelation kit. I spent many hours one night swapping between EPs of the same size on my 6SE Scope (F/10 SCT). The result of that test was that I could not tell the difference between the TeleVues and Revelations no matter how hard I tried.

Chris

[jweaver]

Thanks Great_Bear.. There is a lot of good info there. I don't understand much of it, but it gives me some options.

So am I right in thinking that the 8 and 18mm EPs you recommend are not Plossls? Does this mean that in this size/application, these are better choices than a Plossis EP? (please don't burn me for asking this.. In truth, I am not even sure if I understand WHAT I am asking here).

Does this mean that the "TBE Designed" EP will simply work better than the same sized Revelation Plossl.. I guess they both give the same magnification, but what will the TBE give? Better resolution? Clarity? Field of view???

Also, could someone help me understand the business with connecting an SLR to a scope.. I kind of get the fact that the T-Adaptor just connects to the scope and gives me a thread.. And then I have to buy the necessary AF/EOS to T-Adaptor for my camera..

But I am struggling to understand what the GSO/Revelation 32mm EP brings to the table?

Assuming that it useful for photography, then wouldn't this be the better choice over the Meade?? And if so, we are back on the subject of the kit again, after all, after buying the 32mm Revelation, case and a few bits and bobs, thats almost the price of the kit...

What about this suggestion.. Could I not buy the kit, mainly for the 32mm, adaptor and case... Then buy the 8/18mm EPs you recommend and sell some of the redundant EPs and Barlow from the kit?

I know that this is a long winded way around it.. But I might end up with a nice selection of EPs and it won't cost as much if I am able to sell the extra EPs?

Thanks again for your help.. I really do appreciate you taking the time to respond.

Jon

[great_bear]

I'll tackle those in reverse order :

What about this suggestion.. Could I not buy the kit, mainly for the 32mm, adaptor and case... Then buy the 8/18mm EPs you recommend and sell some of the redundant EPs and Barlow from the kit?

Sure - we're probably over-thinking the whole thing (easily done with eyepieces ) and indeed, I've sold about six individual Revelation Plossls on this very forum myself. People often want them either as individual ones or to double up some focal lengths for binoviewing with a kit they already have. They sell second-hand for about £17 to £20 usually and typically sell within a few days. The Barlow will sell quickly too - it's a good Barlow.

It's also true that the kit comes in a nice aluminium case (which would otherwise cost £20) and that the 32mm Projection Eyepiece is a lovely bit of kit, and the T-Adaptor is a well-machined item.

I am struggling to understand what the GSO/Revelation 32mm EP brings to the table?

Oh that's quite simple: It's an eyepiece with a built-in T-Adaptor to connect a camera to the eyepiece itself as shown here <click> and as you can see, it's a valuable item in its own right - in fact 365 Astronomy have it listed at £60 on its own!

Assuming that it useful for photography, then wouldn't this be the better choice over the Meade?

For visual use, the Meade will possibly have a slight edge, but I'll admit the difference is not significant really.

So am I right in thinking that the 8 and 18mm EPs you recommend are not Plossls?

Correct - they are both proprietary eyepiece designs. They both offer a wider apparent field-of-view than a Plossl (60 degree rather than 52) and in the case of the 8mm, much more comfortable eye-relief.

Does this mean that in this size/application, these are better choices than a Plossis EP? (please don't burn me for asking this)

It can't be answered in such broad terms, because in today's world where there are so many people making different eyepiece styles to different quality standards, you can no longer say "An eyepiece of type X is better than an eyepiece of type Y." - you can only compare specific models rather than design types. I mean, heck, the much-maligned classical Huygens eyepiece could beat a Tele Vue Nagler on planetary views if well-made and placed in the right scope under the right conditions.

All I'm saying (from what I've seen myself on my 105 Mak) is that the 8mm TMB Designed EP will give you startlingly bigger and more satisfying views than the 9mm Revelation Plossl will. Partly because the larger apparent wider field-of-view is more impressive on (e.g.) the moon, but also because stated focal lengths on eyepieces are a bit "rough and ready" and the magnification difference between the TMB and Revelation is substantially more than their 1mm focal-length difference would suggest, resulting in better Jupiter views with the TMB. The TMB is also a lot more comfortable to use because of the more generous eye-relief.

In the case of the 18mm BST, it's the wideness of the view that'll be appreciated most. It's not an eyepiece that I have myself but it's one of the most respected of the low-cost, wider-angle eyepieces.

There is a lot of good info there. I don't understand much of it

In case the exit-pupil thing threw you, here's a brief explanation:

Dividing the eyepiece focal length in mm, by the focal ratio of your scope, gives you the diameter of the light-beam in mm (and hence the brightness) of the image as it leaves the scope. It also indicates where a scope is reaching the limits of its magnification. Here's a (very) rough guide to what exit-pupil width tells you:

• 0.4mm: Sometimes used to detect double-stars, but not much use for anything else
  
• 0.5mm: Very dark image, can provide acceptable lunar/planetary views on top-quality scopes, but most scopes just "mush-out" at this level
  
• 0.8mm: Approximately the maximum "clean" magnification for most scopes - but only for lunar/planetary/double-star; too dark for most deep-sky objects
  
• 1.5mm: Roughly the minimum brightness for enjoyable DSO viewing
  
• 2.0mm: Considered by some as the optimum brightness for DSO viewing, as the sky background contrast is good.
  
• 5mm+: Much beyond 5mm and adult eyes stop noticing further brightness increases, since the excess light falls outside of the iris. Some people state this is "wasting light" - which shows a somewhat embarrassing lack of understanding as to what's actually going on.

I know that this is a long winded way around it.. But I might end up with a nice selection of EPs and it won't cost as much if I am able to sell the extra EPs?

Sure. Go for it I think it's important not to think of eyepiece purchases as an irreversable once-in-a-lifetime decision. You can always sell on unwanted ones. That's why there's such a thriving second-hand eyepiece market both here and elsewhere.

[jweaver]

I'll tackle those in reverse order :.

Thanks Jeremy. You are an absolute star..

I am now swaying towards the idea of buying the filterless kit for £99 but also the 8mm TBE EP..

Then over time, I will work out what I can and can't use and will sell the redundant onces and will then pick up the 18mm BST at a later date.

Again thanks.. Your info is invaluable to me and has explained a lot!

Just another quick one about Exit Pupil... My scope has a Focal Ratio of 13.. So if I use an 8mm, then this gives me a 0.61mm.. Isn't this a bit close to 0.5, where you say "can provide acceptable lunar/planetary views on top-quality scopes, but most scopes just "mush-out" at this level"?

Since my scope has a theoretical magnification of 241x, which I could achieve using a 5-6mm EP this would make the exit pupil 0.38-046mm which we too dark. So is this a paradox with small scopes? Whilst they can optically achieve higher magnifications, the amount of light is so low that you can't actually use it?.

So I assume that the Exit Pupil is the most important factor when choosing an EP and/or Scope?

Jon

[twotter]

One benefit to buying a kit is you have an immediate selection of EPs allowing you to find the ones you most commonly use. Then it's a simply a case of upgrading those.

For instance I've built up a collection of GSO & Meade 4000 plossls in a range of sizes. Over time I found that I used the 32mm and 12mm in nearly all my observing sessions. Following a good bit of research I decided to try and build up a collection of Hyperion EPs. The first one to come up on the For Sale boards was a 13mm which I bought, and it's a great EP.

I'll buy others as they come up for sale in the future

Btw, the only filters I use are a Moon filter and an OIII (lovely views of the Veil Nebula last year).

[great_bear]

Just for reference (for anyone else reading this thread), the 8 part kit that Jon mentioned here <click>, is also available as a 7 part kit here <click>

But you're losing the 12mm Plossl - which is a very good Plossl - and so not worth the mere £8 saving.

[jweaver]

Just for reference (for anyone else reading this thread), the 8 part kit that Jon mentioned here <click>, is also available as a 7 part kit here <click>

But you're losing the 12mm Plossl - which is a very good Plossl - and so not worth the mere £8 saving.

Hi Jeremy.. I did post the links in my first post.. And just for clarity, I have put my original choice below..

The first one I was looking at was this one for £130:

Revelation Photo Visual Eyepiece Kit

This one is sold by many places and is the kit which one the SkyAtNight award..

The 7/8 piece kit appears to be the same, but with no coloured filters.

Thanks for posting the 7/8 piece kit.. This now explains why I kept seeing the price change between £92 and £99.. I didn't even notice there were 2 kits.. They seem to be the same as the "Revelation Photo Visual" kit but with no filters.. And in the case of the 7 piece set, its also missing the 12mm EP too.. Which as you say for £8, it seems a no brainer to get the kit with the 12mm EP.

So I think that the 8 piece kit is the best value at £99.

Jon

[great_bear]

Just another quick one about Exit Pupil... My scope has a Focal Ratio of 13.. So if I use an 8mm, then this gives me a 0.61mm.. Isn't this a bit close to 0.5, where you say "can provide acceptable lunar/planetary views on top-quality scopes, but most scopes just "mush-out" at this level"?

Yes, most scopes do - but these small Maks can handle it. Since it's at the upper limit of the scope, the brightest stars will show a tiny circle around them (known as the "first diffraction ring") but the Moon's surface will appear sharp, and the planets will be at the largest possible size at good viewing quality with this scope.

So is this a paradox with small scopes? Whilst they can optically achieve higher magnifications, the amount of light is so low that you can't actually use it?

It's the same with all scopes actually - but the real issue is what do you actually mean by "maximum magnification"? After all, as you push the magnification higher and higher, the scope doesn't stop working nor does it explode. So how do you define what maximum magnification actually means?

In the absence of any formal definition of "maximum magnification", department stores can slap any figure they want for "maximum magnification" on cheap telescopes - like this 76mm reflector from Argos - which apparently has 525x maximum magnification! I do hope customers - especially children - aren't too disappointed when they discover that the real maximum is closer to 100x

The astronomy industry however, seems to have adopted an informal standard: Twice the aperture size for standard telescopes, or three times the aperture size for very high-quality scopes. But this isn't really helpful for beginners, because - as a budding astronomer - you have to consider the question: "Maximum magnification for what purpose? Star splitting? Lunar/planetary observation? Deep sky objects (galaxies/nebulae)?" - each of those has a different maximum in any given scope.

So, casting aside marketing tricks and ploys, here's what happens with any scope or binocular - of any reasonable quality - with regard to magnification:

• When the magnification reaches half the numerical value of the aperture of the telescope in mm, then you've reached the maximum visual daytime resolution of the scope. This equates to an exit pupil of 2mm. Any more magnification will make the image bigger, yes, but it won't reveal anything you couldn't see before if you looked hard enough; as you magnify more, the image blurs more; you simply can't get any more detail. It's important to remember that some people might still find more magnification subjectively enjoyable - that's their prerogative. At night however, our vision is distinctly more ropey. Therefore, the magnification can be pushed higher before it hits the lower-resolution limits that our eyes have at night.
  
• When the magnification reaches the same numerical value as the aperture of the telescope in mm, then you're starting to approach the maximum visual nighttime resolution of the scope. This equates to an exit pupil of 1mm. The image quality should remain top-quality at this point, but if you push much past it, the artifacts of "diffraction-limited optics" start to come into play - the most noticeable being that concentric rings will start appearing around bright stars, yet lunar and planetary images can still remain good even at this stage with good scopes. That's at a magnification figure of about 1.2 to 1.3 x the aperture size. If the scope in question is a small scope, people will push harder in order to get a satisfyingly larger planetary image; although experienced observers will appreciate that you don't actually get any more detail this way. On lesser scopes (in particular, cheap Newtonians) image contrast can drop at this point, leaving views that are starting to look smeary and washed-out.
  
• When the magnification reaches twice the numerical value of the aperture of the telescope in mm, diffraction effects and low-light levels have already taken quite a toll on lunar and planetary images, and pushing further won't achieve anything useful, and there are those who argue that even pushing this far is is counter-productive.
  
• Higher than this? Well you'll still see stars, but they'll look like little discs at this level (but only as a side-effect of the optical process). The only thing this is typically useful for is detecting double stars, where an elongated disc - even if only slightly - is an indication that you're looking at a double star, not a single one.

Bear in mind of course, that the above figures should be treated as a very loose guide. Also (especially when reading older texts) you'll sometimes see people refer to magnification in terms of "power per inch". If you divide 25.4 by the exit-pupil (in mm) then you'll get the power-per-inch figure for the equivilent magnification level.

So I assume that the Exit Pupil is the most important factor when choosing an EP and/or Scope?

It's a balance between that and magnification levels, yes, although obviously the reputation of a particular eyepiece model plays a significant part in the choice too.

Here's some useful magnification levels to remember:

• 25x Fits all of the Pleaides into a Plossl-sized view
  
• 75x Fits all of the moon into a Plossl-sized view
  
• 150x Minimum magnification for satisfying planetary views - but experienced observers can cope with less
  
• 170x Above this level, atmospheric conditions both outside and inside the telescope may start causing havoc
  

That last point is an interesting one. You'll read many posts from people - even from me in the past - stating things like "You'll never get more than 220x magnification under UK skies." I am however, no longer convinced that this is correct. Whilst exceptional skies are - by definition - somewhat rare, I believe that a lot of turbulence problems that people suffer are due to poor scope cooling or bad scope design. Either way, I'm sure that it's possible to get impressively high magnification levels under the right skies with the right equipment.

Finally, note that since the amount of sky that you can see depends on the size of the "apparent field of view" of the eyepiece as well as the magnification, and also the fact that the size of astronomical objects is specified in sub-units of degrees, some people (especially more experienced ones) find it more helpful to talk about view sizes in arcminutes and arcsecond rather than in magnification levels.

I didn't even notice there were 2 kits.. They seem to be the same as the "Revelation Photo Visual" kit but with no filters.

- and just to really confuse things, there used to be variations of the kit with the Barlow replaced by a 6mm Plossl, and a completely different selection of filters!