Meade LX90 SCT 8"

[batesy71]

I have just been browsing around looking for what I can invest in next to move to more serious stargazing.

I unfortunately will be limited by the budget and at £1500, this might be my limit.

One website offers a SCT and ACF version. I understand what SCT is but I am unsure what the ACF means. At an extra £100 or so to the SCT, is it better?

I am also under the impression that a lower focal ratio of say f/4 is better for deep sky observation.

Compared the the f/10 of the LX90, what difference would be expected for such objects?

Finally, what are the thoughts generally of the LX90 from those who own or have previously owned one.

Many thanks in advance.

Alan

[PeteC]

Hi Alan

I've had an LX90 for a few years as a first serious scope and I've been happy with it. SCT is Scmidt Cassegrain Telescope - it's the optical design. ACF is Advanced Coma Free optics - less distortion at the edge of the field than the version I've got. It may be better but I haven't had the chance to compare them. The LX90 is f10, which is a reasonable compromise for both deep sky and moon/planets. If you want to get into deep sky imaging you can get a 0.63 focal reducer that turns the scope into f6.3 - this gives a wider field of view and half the exposure time.

The LX90 is on an altaz mount, which is fine visually but if you want to do imaging you will be limited to about 30sec exposures. I get reasonable results with maybe 50 to 100 30 sec exposures stacked together. If you want to do longer exposures than that you need to look at an equatorially mounted scope - you can get a wedge to turn the LX90s mount from altaz to equatorial.

That's all I can think of, if you have any questions let me know.

Pete

[ollypenrice]

The F ratio is a bit long, maybe, for some deep sky viewing. There is no real advantage to F10 at high powers since you can use a shorter FL eyepiece on a faster scope to get the magnification. However, well collimated SCTs are good on the planets, double stars etc and with a 2 inch back and a widefielld EP you can open up the view. They are also nice and compact and easy to collimate.

For deep sky imaging this would be near the bottom of my list. Wedges are expensive and, in my experience, a pain. The tracking precision of the LX mounts leaves a lot to be desired. I had an LX200 and never got it to track well enough for DS imaging. A friend had an LX90 and came to the same conclusion. We both ended up piggybacking small apos and guiding through the Meades.

In a nutshell, nice for visual if a bit 'boxed in ' by the FL, great for planetary imaging, bad for DS imaging. One other issue is whether or not you really want to buy a setup which is mount-and-scope in one. Experience suggests that with growing experience we tend to want to change our setups from time to time. If you really fancy the SCT you might consider putting the OTA on a universal mount.

Olly

[michael.h.f.wilkinson]

For visual work, and planetary photography, aperture is king, for DSO imaging, focal ratio rules. For a given aperture, an F/10 scope with a 10mm EP gives essentially the same performance as an F/5 scope with 5mm EP. The F/10 scope will be more tolerant of lower cost EPs than an F/5 scope. The maximum FOV of the F/10 will be smaller.

An F/10 SCT is fine for visual observation of DSOs, except for a handful of large ones (Rosette, Pleiades, M31, NGC 7000). With a 2" visual back I get 1.34 deg FOV, which fits even the double cluster. I have bagged over 500 DSOs including 234 galaxies (down to mag 13), and 2 quasars (mag 12.8 and 13.8) with my Celestron C8. The great advantage of the SCT design is that it is very compact indeed and lightweight. I can take it on holidays without omitting a single pair of my wife's shoes. It sets up quickly and rarely if ever needs collimation.

Mine came with the very good Vixen Great Polaris mount, which tracks very nicely for visual and planetary photography. I much prefer German equatorial mounts (GEM) to fork mounts ad wedges. For deep sky photography my set-up is not that good, as Olly says. With a 0.63x focal reducer I made one or two shots on film years back, but I have not done anything since. BTW, reducer/correctors are available for SCTs but ACF and the similar Edge-HD versions seem to require very different (largely unavailable) correctors. Even with my large FOV EPs I have never been troubled by coma.

In short, for visual work, the SCT is a compact, versatile scope, especially if paired with a good mount (GEM, or alt-azi fork for preference). They do not come cheap, and going for a Dob gets you more aperture for the same money, but in a much larger package, which needs much more frequent collimation.

[E621Keith]

I agree with Michael, a F10 SCT is much easier on the eyepiece than a F4 Newt. Also, a 12.5 mm ortho (8" f10 - 163x) is much more comfortable to use than a 5 mm ortho (8" f4 - 160x), so if you opt for conventional eyepiece designs, the fast Newt can be very uncomfortable to use.

[Northern Soul man]

Hi Alan

Agree with all that's been said. I owned and LX90 for a few years and had a fantastic time with it, very portable - some say that the Meade electrics are a little hit and miss - but I owned one for about 4 years and never had a problem with it, nearly out every clear night and fantastic, just sold mine and a 12" dob to part fund my cpc 1100, the SCT's, as with all scopes are a compromise, but visually they "fill" a lot of the middle ground - as you know there are different types of scopes for different goals - but I like the SCT's and for me the majority of galaxies are faint fuzzies and unless you have truly dark skies - which are rare now - they are "patches of mist and just "detectable" - but that's the fun for me, also the long focal length helps with planetary work - some say that the large central obstruction (secondary mirror) degrades the views, but the atmosphere, seeing and transparency don't help either, but for me, a very nice scope and ticks all my boxes for me. Paul.

[r3i]

Had an 8" LX90 for about 4 years. As others have said it's a great visual package, very versatile and pulls a lot in.

Only sold mine because I got sucked into DSO imaging, which is where the LX90 is challenged for a variety of reasons. OK for lunar & planetary imaging though.

[batesy71]

Many thanks for the replies guys. Very useful information

Al

[earth titan]

I have the 8" lx SCT version and it's not going anywhere, ever....

Mine is mounted on an HEQ5 as I wouldn't touch the Meade mounts with a very long stick, form the reviews I've seen.

[vlebo]

Looking at the posts in this discussion I would assume a large aperture SCT like the 9.25 Celestron or meade equivalent would be a good all round scope for visual use. I am looking to have just one scope that allows planetary and deep sky viewing mounted on an alt az mount (Skytee 2 ) for grab n go use whenever I have the time.

Vlebo

[earth titan]

I think you may find an f10 insufficient for some DSOs but as a compromise scope they are good.

[michael.h.f.wilkinson]

Looking at the posts in this discussion I would assume a large aperture SCT like the 9.25 Celestron or meade equivalent would be a good all round scope for visual use. I am looking to have just one scope that allows planetary and deep sky viewing mounted on an alt az mount (Skytee 2 ) for grab n go use whenever I have the time.

Vlebo

Sounds like a good plan.