New Scope LX90 any tips?

[Patw#73]

I've just got myself a secondhand LX90 8" SCT. I'm pretty pleased with it so far, though I haven't had much chance to use it. Is there anything I should know/look out for or any tips etc to make it easeier to get on with?

How easy is collimation?

How regular would you check it?

Thanks everyone!

[robbieince]

Congrats! I used to have one - they are cracking scopes......

Mainly trouble free - the only thing to watch out for is the screws on the OTA can rust - there is a replacement stainless set from AstroEngineering.

Collimation is a doddle but uses an Allen key - you can get replacements known as Bobs Knobs - much better. Mine held collimation really well although I checked it pretty regularily. I only had to change it if I transported the scope - not in normal set up / tear down.

I would add a counter balance kit especially if you intend to hang a camera off it - or even some heavy 2 inch eyepieces.

But mainly - just use it - it will give you loads of pleasure!

[Patw#73]

Rob,

Thanks for the advice - where would i get Bobs from?

Counter balance? Can you explain how that would work?

Sorry for being dumb but I still quite new to this lark!

Cheers

Pat

[robbieince]

No Worries Pat

http://www.bobsknobs.com/ for the collimation knobs - they are cheap and price includes postage etc.

As for blance - there is an attatchment here (under the LX SCT all models section) thats shows a couple of options.

Accessories for ETX90, ETX105, ETX125, LX90, LX200, LXD55, LXD75, and Coronado PST telescopes

Basically extra weight at the back of the scope from diagonals, cameras etc puts it rear heavy which puts strain on the clutches and can wear the drive gears. This is counterbalanced by putting extra weight on the front of the scope - or slung underneath.

[Ben Ritchie]

"Bob's Knobs" are certainly worth it. They're in the states, but very reliable and quick delivery - http://www.bobsknobs.com/

Assuming the LX90 is like the LX200, I found the Calibrate Motors and Train Drives routines did a lot to help GOTO accuracy (you do Calibrate Motors first, then Train Drives). The benefit depends on how accurately you do it, I used to use a cross-hairs eyepiece and distant chimney pot in daylight to get it spot on.

[Patw#73]

Thanks for tip about the Calibrate drives and motors.

I've had a look at the astro engineering site and well, that's done me no good at all! Now i'm convinced I can't possibly live without all those add-ons.

One other thing - the diagonal doesn't seem to be of particularly high quality - is it worth replacing?

Any thoughts?

[Ben Ritchie]

One other thing - the diagonal doesn't seem to be of particularly high quality - is it worth replacing?

Yes - you don't need to spend a lot of cash here, but the stock diagonal is pretty poor and a replacement's well worth it.

[Patw#73]

Any particular make of diagonal you would recommend?

[Ben Ritchie]

Not a make so much as a type - pretty much any of the "enhanced" (97% reflectivity) or "dielectric" (99% reflectivity) ones, although these days the latter is much more common. They're a step up from the el-cheapo one that came with your 'scope. Visually you can't tell the difference between 97% and 99% reflectivity and they're all pretty well made these days, so no need for the expensive brands. I can't tell the difference visually between my Celestron diagonal and my Astro-Physics one that cost almost three times the price. So i'd shop on price more than anything else, although it's worth picking up a 2" one to get the flexibility to use wide-field eyepieces, nice with the long focal lengths of a SCT.

The Celestron 2" dielectric was on sale recently for £75 and is excellent. Haven't tried this:

Diagonal Dielectric 99% Quartz LX

but it also looks good - FLO might know if the Celestron one is still available at clearance price.

[Patw#73]

Sorry to ak the obvious but I only have 1.25" eyepieces and i presume that you can get some kind of adaptor - would this have any effect on image quality etc?

[Ben Ritchie]

Sorry to ak the obvious but I only have 1.25" eyepieces and i presume that you can get some kind of adaptor - would this have any effect on image quality etc?

The 2" diagonals usually come with a 2"-1.25" adapter. Optically they're effectively identical (some say that you get more even illumination with a 2" diagonal, even with 1.25" eyepieces, but it's at best a very minor difference).

You don't have to buy a 2" diagonal, but it's not a lot more money (e.g. a William Optics 1.25" diagonal at £65, or a Revelation 2" at £75ish) and gives you the option of using 2" eyepieces in the future.

[Patw#73]

I've had a look at the Diagonal Dielectric 99% Quartz LX.

As you said it does come with the smaller adaptor - I feel yet another purchase coming on!

Thanks for the advice.

[brianb]

1. Like any Mak or SCT, you positively need a dew shield. And a dew heater for the objective, unless you live in a desert or or prepared to put up with 15 minute maximum observing sessions.

2. Don't bother with Bob's Knobs. There is no better way to guarantee spoiling the collimation that to fit them, or to pretty well ensure that you'll have to recollimate most times you use it. If you take reasonable care there is no danger in using a hex key to make the adjustment; you won't get greasy finger marks on the corrector (you will if using Bob's Knobs) and the standard adjustment holds well enough that you will probably only have to do the job once.

3. Get a 2" SCT visual back & use a standard (but high quality) 2" diagonal, or save a few pence by getting a SCT threaded diagonal (WO diagonals come with both 2" & SCT nosepieces). You don't need 2" fitting eyepieces but they do help, especially in longer focal lengths.

4. Learn the names of the bright (first magnitude) stars & how to find them in the sky. If you misidentify your alignments will be up the swannee. Otherwise they should be pretty good.

5. You need a good quality power tank - to drive the dew heater (see above) as well as the mount; internal batteries are expensive & always seem to fail at critical moments. Read the manual regarding cordwrap. At least Meade's implementation works, unlike Celestron's which is insane.

6. Let the scope cool down before trying to observe moon, planets & anything else at high power. It typically takes 1-2 hours. And don't push the magnification too high, x240 is plenty.

7. As others have stated, counterweighting can be useful, but you don't need it unless you're using a very heavy eyepiece or a camera. Wrist/ankle weights stuck to the tube with velcro work and are a lot cheaper than the "professional" counterweight systems.

It's a great wee scope, take your time to learn its foibles (they all have them) & enjoy it!

[Ben Ritchie]

4. Learn the names of the bright (first magnitude) stars & how to find them in the sky. If you misidentify your alignments will be up the swannee. Otherwise they should be pretty good.

That's a good point, it's confusing as hell when it asks you to pick out Rasalhague or Zubenelgenubi - both reasonably bright 2nd magnitude stars that my LX200 used to pick for alignment but probably not names that trip off the tongue

(Alpha Ophiuchi and Alpha Librae in case you were wondering )

[Patw#73]

Thanks again - a dew shield was on the list anyway.

I'm pretty comfortable with navigating my way round the skies so alignment shouldn't be an issue.

Interesting though that there are different opinions about Bobs Knobs...

I'll go for the 2" diagonal it seems to make more sense in the long run.

By "letting the scope cool down" I presume you mean have in its observing postion and temperature for an hour or so before observing the moon, which would normally involve moving it from indoors to out.

[brianb]

By "letting the scope cool down" I presume you mean have in its observing postion and temperature for an hour or so before observing the moon, which would normally involve moving it from indoors to out.

Precisely.

[Patw#73]

Once again thanks for advice.

The more you talk, the more you learn.

Can i ask one more thing?

Where do you normally store your scope when not in use?

For instance, how do they react to temperature changes, say stored in a garage?

Or is it better to keep them indoors?

I have stored mine in a conservatory which is subject to quite significant differences in temperature.

[Ben Ritchie]

It'll be fine stored pretty much anywhere dry - I used to keep my LX200 in a conservatory. The bigger the difference from ambient temperature the longer the cool-down time outside, but if you take it out a couple of hours before you plan on using it then it'll be fine.

[brianb]

Where do you normally store your scope when not in use?

For instance, how do they react to temperature changes, say stored in a garage?

Or is it better to keep them indoors?

Don't have a garage but an unheated garage or shed would be good provided it's dry. Keep the caps on everything to keep spiders etc. out & throw a tarp over to keep dust off.

Mine lives in a spare room which is normally left unheated though it's obviously a few degrees warmer than it is outside.

[alfingido]

Superb scope, good choice. I had a few mods on mine, I got a Peterson EZ Dec clutch kit and EZ focus kit . Look HERE. Really makes a difference, the clutch kit will stop you running the risk of stripping the threads on the declination clutch knob ( easily done) and the focus kit makes the focus knob much smoother and gets rid of backlash.

I also bought a Williams Optics dielectric diagonal that made a huge difference over the original. A good set of eyepieces is essential, I dont remember seeing any real benefit from 2" eyepieces on sizes below about 17mm.

Get yourself a good eyepiece about 40mm for wide field views. Double cluster looks really impressive in a 40mm eyepiece.

Go out and enjoy it.

Allan