LX-85 5" Refractor viewing Saturn (26th Sept 2023)

Beta Ray Bill

Hi

I'm new to Astronomy. I have an Refactor Telescope on an LX-85 mount (Nice piece of kit 😊 )

Last night I was observing Saturn and the Moon.

Moon was great, I was able to focus it well and could see a lot.

Saturn was also great, I started with a big lens and try and go smaller and smaller to get a better view.

I have 2 issues though.

1: The Earth's movement means I keep need to readjust the telescope, considering its an electric mount, is there a slewing option I should be using that keeps it fixed on target.

2: Getting good focus is hard with the smaller lens's (6mm and below) is the a fine tune focus piece you can get for the eye piece? The focuser feels stiff on the telescope, do you need to lubricate/clean it?

Regards

G.

Popoutman

It's not a bad scope by any means, and it can give you a lot of enjoyment. The aperture of the scope is enough to start to give nice details on the Moon and the planets, and there's enough light-grasp to start to make deep-sky things visible.

There are some deliberate design choices that force some limitations into the design - but those design choices allow the cost to be brought down to a more achievable amount. The Achromatic objective (two-part front lens, without any 'exotic' extra-dispersion glass) will cause some colour halos around

The mount is generally "good enough" for most beginner uses, but it will frustrate if any long exposure astrophotography is tried with that scope and mount. It'll give great results when polar aligned and using short exposures, e.g. with "electronically-assisted astronomy (EAA)", example vid here - https://www.youtube.com/watch?v=mOZI549sT58 and forums https://www.cloudynights.com/forum/73-electronically-assisted-astronomy-no-post-processing/ and https://stargazerslounge.com/forum/208-eeva-electronically-enhanced-visual-astronomy/

To answer point 1:

It sounds like you are either not polar aligned well, or your GoTo setup is not correct.

Polar align the mount (a starting point would be here: https://www.youtube.com/watch?v=9wOg7zH9Z_Q). When the polar axis is aligned parallel with the Earth's axis, the mount can be driven on that axis to counter the Earth's rotation. On pages 4 and 5 of this pdf (https://www.meade.com/downloadEntityFile/assets/product_files/instructions/LX85_07302018A.pdf) the polar axis is the one that goes from the "optional polar scope cover" through the "polar axis port with cover". If that's pointed to the right spot beside Polaris, then only one of the motors will be needed to drive the mount.

When the mount is polar aligned, the computerised GoTo routines have a much easier time in getting to know where they are pointing, and when they are correctly aligned, they will do a much better job of pointing and a much much better job of tracking. If you are having to continually correct the drive, there's something wrong with your GoTo setup, or (fairly unlikely) there could be an issue with the mount itself.

As for point 2:

The scope is a 120mm f/6 Achromat, with a two-lens front objective. The f/ratio is actually 5.8 (if I've got the right scope in mind). The physical depth of focus from detectably-just-inside-of-sharp to detectably-just-outside-of-sharp is theoretically 90 microns (0.09 mm). The focusers are deliberately stiff, but if you have good mechanical aptitude the focuser can often be tweaked to feel better. If you do not have really good mechanical aptitude, I would recommend not to go fiddling unless you are being assisted by someone that does have good mechanical aptitude. You're not likely to break anything, but it may be an exercise in frustration trying to get things back to anything near a workable state if mis-tweaked. Also, the tooling for the tweaking may be smaller than most hobby toolsets would have.

It is certainly possibly to replace the focuser with other higher-spec and higher accuracy models - but at a significant cost. For the lens you have, it would be a hard justification to upgrade the focuser if it costs a chunk. There may be updates to the focuser wheels to have a fine-focus dual-wheel - this is a Chinese-built scope from one of the major manufacturers that supply the main brands so there's likely quite a bit of a catalogue of mix'n'match components to pick from. You might be lucky, but it will be a fairly significant chunk of work to research.

At this link is a simulation of Saturn with various focal length eyepieces. Note that more magnification is not always a good thing. If the atmosphere is wobbly then those wobbles are also magnified. Higher magnification also means the image is more dim, and it can sometimes be the case that you'll lose detail by going higher in magnification..

I hope this is useful to you! Enjoy the using of the scope!