Bought a Skyliner 250px Dobsonian Telescope on eBay - anything to look out for when checking it over?

[SpoonyPizzas]

Good afternoon all,

After too much research.... I decided to take the plunge and bought my first telescope - Skyliner 250px for £300 on eBay supposedly in excellent condition with no scratches/marks on mirrors.

Is there anything I should be looking for or something to take with me to check this scope isn't faulty?

Is there any tests I can carry out?

Thanks

(First couple of many questions I assume!)

[wolfpaw]

Welcome to the forum

[wolfpaw]

The best way of checking it out is to have a look through it. Not easy if it's cloudy. Newtonians are pretty simple things so have a look at the secondary mirror, the spider vanes that hold, see if the focuser moves in an out easily and doesn't have any 'give' in it, and check that the primary mirror looks clean without any mottling or scratches. Testing the primary mirror without a clear sky is difficult so in some respects you just have to hope that all is in order.

I'm sure someone will be along to give a more detailed answer soon

[Joseki]

I'd agree with wolfpaw.  Reflectors on dob bases are quite simple.  First up I'd check both mirrors are in good condition (I wouldn't worry about dust), that the focuser works well, and the dob base is in good condition - i.e. none of it has gone crumbly.   If it's a flextube version check that it extends and collapses fine.  With the telescope on it's base try moving it in the horizontal and vertical (az & alt), should be nice smooth movement.  The only other possible thing that could go wrong with it that I can think of is if one of the screws that adjust the mirrors is ceased up  - though I don't think that's likely especially if the rest of it is in good condition.  Checking you can actually come to focus on a distant object (like Jupiter) would be nice but I guess you're covered through ebay in the end.

[mashedpotatomountain]

there are loads of way more experienced people on here who can give you a better checklist, but i would say there's not much difference to checking out a 250PX than there would be most other scopes -

and most people in this hobby take utmost care of their equipment, but here are a few things that come to my mind :

• as you say, the mirrors are THE thing to make sure of. if you're a total newcomer to telescopes (like i was in january), then you won't yet have the experience to know if the scope is well collimated etc, so by all means ask to look through an eyepiece if you can,

but if the view isn't perfect that might just be a collimation issue and not something to worry about now. unless the mirrors have a factory defect (highly unlikely), then as long as they aren't scratched or damaged in any way visible to your eye then you should be

pretty confident that they'll perform well, even if they need a lot of adjustment once you learn how to do it. don't be put off if you see a bit of dust etc, which naturally settles on all mirrors eventually, doesn't harm performance too much (until they're really very dusty)

and can be cleaned off with due care. if something has been dropped down the tube and hit the primary mirror, it will be pretty obvious i think.

• you shouldn't see any damage to the tube assembly either, including stripped or badly treated screws, dents or anything that indicates it's been thrown around. again not very likely, but accidents happen.

• check for the 6 screws on the bottom end of the tube that hold & adjust the primary mirror, 3 large & three smaller. again highly likely, but if any are missing this would be very odd!

• the base, whilst very sturdy and good at its job, is only coated ply or chipboard i think? so you might like to check around/underneath to see that this hasn't been roughly handled either -

if the coatings are chipped or coming away, this might lead to wet eventually getting into the wood, which wouldn't be great.

• have a go with the focuser just to make sure it travels smoothly, fully inwards & outwards. can't see this being a problem but i'm just trying to think of things you may as well check anyway.

• make a list from the FLO website or another retailer of all the additional components you should be getting too (assuming the seller listed it as complete with these) - ie. 10mm & 25mm eyepieces, 9x50 finderscope & mount, both 2" and 1.25" eyepiece adapters,

plus all the relevant lens caps for the scope, finder and focuser.

hope this helps, i'm sure you'll be fine - most people who buy a telescope treat it lovingly not badly!

rich

[Tinker1947]

Take a torch and if you can't get a good view of the primary mirror shine it at the mirror it should show anything nasty, the odd dirty blotch is nothing to worry about.....

[SpoonyPizzas]

Thank you all - really appreciate the info been a great help and it is the solid-tube version not the flex-tube but grateful you covered all possibilities