great_bear

It’s worth noting also that - at the time of writing - the instructions on FLO’s website for collimation using this device have an error in the last step. I let them know a few mins ago.

Guess it wasn’t fully locked-down then 😉

Gosh I can see how - if not properly understood and/or used correctly, this device could cause a lot of confusion. It’s a myth that *everything* should be concentric; in fact it’s physically impossible to do so because: If the secondary has been mounted according to secondary offset rules then the shadow of the secondary will appear be off-centre (as shown in Spiles diagram above) since the secondary is (intentionally) no longer exactly physically centred with respect to the spider vanes. This is normal and correct If the secondary hasn’t been mounted with secondary offset, then the spider vanes will appear be slightly off-centre, because the optical axis in a non-offset scope is slightly skewed relative to the tube. This is also normal and correct. In a properly-collimated Newtonian, the following three conditions need to be met: The outline of the secondary mirror should be centred relative to the sight-tube/collimator The outline of the primary should be centred within that secondary outline The primary’s reflection of the sight-tube/collimator should be centred relative to the primary’s centre-spot The position of the secondary shadow and the position of the spider vanes can be ignored, and in practice, will tend to lie somewhere between 1 and 2 above.

Once the primary gets locked down after colimation, the springs are out of the equation and make no difference.

I thought “I must read this thread to find out what those ‘guilty feelings’ are about”, and I had assumed it could only be: Buying a scope during a cost-of-living crisis Secretly enjoying being away from the family Observing when it was your turn to do the washing-up I must admit, I hadn’t even considered “goto guilt”. The only “goto guilt” that I can imagine is from NOT buying it in order to save money! In the modern world we now know that you don’t need to spend a lot of money to get a great scope, and that “bigger” is not necessarily “better” because 8 inches is too unwieldy for many people. A five or six-inch scope really hits the sweet spot in terms of portability, and the only reason NOT to get goto is if you prefer the joy and freedom of sweeping the skies with a heavy, long-length scope and a smooth, well-engineered alt-az mount. …so don’t worry, the last of the old-school ‘scope-scoffers’ died years ago, and we no-longer live in that kind of world. I’m sure I speak for all, when I urge you to just enjoy your goto scope, guilt-free, along with all that extra productivity that it brings!

Also worth noting that you can’t compare daytime viewing with night. The best bet is to find some double stars to test with on a clear, still night.

Oh - one other thing - this time of year seems awful for astronomy here in London - high-level cloud seems to be a permanent fixture here. As such I don’t expect to get much astronomy done for a few weeks until the weather clears up. That’s frustrating but you learn to live with it.

Expect to get cold - especially if you’re in the UK. So buy a pair of fingerless gloves, a woolly hat, some thermals to wear under your jeans, and a generous scarf. You will likely need these things even in the summer in the UK - it’s shocking how much the temperature drops once the sun goes down. I assume you already have a jumper and a warm coat. It’s frustrating to cut short an astronomy session on a perfect night for no reason other than being frozen to the bone. On the flip side it’s wonderful to be smugly warm whilst everyone around you is saying “Well I simply must go inside - I don’t know how you can bear the cold out here!” You’ll also need a chair. I find with a 1200mm Dobsonian I don’t need a fancy chair; a simple lightweight walking stick chair is enough, as the seating position is typically quite high on those. Smartphone apps are handy - I use Stellarium, and that’s mainly because I can tweak my on-screen settings so the views match what I see through the eyepiece under the heavily light-polluted skies where I live. One final thing I’d recommend is a head torch with red-light mode - it’s more useful than a standard torch in my experience. It doesn’t need to be super-bright and it’s better to have standard batteries as it won’t see enough use to justify the hassle of rechargeable batts. You can make do with a rear bicycle lamp as an alternative.

Note that you don’t *have* to get a laser collimator - but it definitely helps when the scope’s so long that you can’t look through a Cheshire collimator at the same time as adjusting the primary mirror - it makes the process a lot smoother and more intuitive than ‘tweak-peek-tweak-peek’…

OK now done using the kitchen scales. The standard 130P weighs 3.1Kg - so not as light as I thought!

Yeah I should really weigh mine on the kitchen scales. The bathroom ones might not kick-in unless a certain threshold is met. I’ve weighed the cats before (moggies, not telescopes) but I did that by stepping on the scales holding each cat, and then sleighing myself without any cat, and doing the maths.

Well, my (wife’s) Explorer SynTrek died last month - but it had worked fine for 14 years, which was fair enough. To repair it, I just bought a SynScan motorised head off eBay for £90 which screws on to the same tripod - so the “repair” actually turned into an upgrade! 🙂 As I’m sure you can imagine there are reliable units and some which were not so good. Best to ask about specific ones that you are considering.

That is not the case. The 130PDS is listed at 4Kg but the 130P is different. I put one on the bathroon scales last week when I was weighing all my scopes. It registered 0Kg. Clearly it can’t be weightless - it’s just less than my bathroom scales could measure. The 130P scopes are very, very light. In a gust they can wobble, but they settle down immediately, unlike heavier scopes. [EDIT: Just weighted using kitchen scales - 3.1Kg, so not worlds apart from the PDS version - the 0Kg reading must be a ‘feature’ of the bathroom scales]

I’ve changed my earlier post to recommend the 3.2mm Starguider - because mine arrived the other day and I just tested it in my 130P (same mirror as your scope). It is a *stunning* eyepiece in that scope, and provides razor sharp detail on the moon with even the tiniest craters clearly visible. Some will tell you that a 3.2mm Starguider is “two powerful” that that scope. They are categorically wrong. It’s amazing and you’d have to pay significantly more money to improve on the crisp lunar views it provides.

The only "essential" accessory that you need is a dust blower to keep eyepieces clean (such as can easily be found on amazon). You don't need a laser to collimate that telescope. A home-made collimation cap is good enough. Later on, when you've got more money and decide that you are enjoying astronomy, then you might want to consider a 3.2mm Starguider eyepiece for more magnification. Avoid any eyepieces cheaper than that, as they won't won't get the best out of that particular telescope that you have. It is a nice telescope that can serve you well for many years.

I've never seen them side-by-side to judge. Parabolic mirrors just allow shorter telescopes to be made (e.g. F5 instead of F7) at the expense of adding some 'coma' distortion at the edge of the view. The other disadvantage of shorter scopes is the limits it places on eyepiece selection. You've got more options.

It turns out the OP's scope is a 130, not a 130P so a 3.2mm eyepiece is way too high. 200x is the maximum I can get out of my 130p but reaching 240x is usually possible on my Mak180 or 8" Dob, and on a good night, between 1am and 2am, there can be a period of about 30mins where 280x is no problem, and one can see the swirls on the clouds on Jupiter.

Best avoided - modern binoculars are often gas-filled, and if you dismantle them for repair, then they can fog up internally whenever you take them into cold environments.

I hadn't heard of the hygroscopic issue before - that explains why I had a bizarre experience two days ago where - despite using clean materials, the eye lens on an eyepiece I was cleaning was getting dirtier and dirtier as I was cleaning it. It simply didn't make any sense. As I was very familiar with this eyepiece I dismantled it and cleaned the lens seperately as I feared some eyecup-grease had maybe found its way under the rim of the barrel which might explain it. Carefully and slowly cleaning the lens by itself, it was STILL getting dirtier and dirtier as I cleaned it! I thought I was going mad. Then I came to the conclusion that the discolouration around the edge of the lens must be permanent damage from me rubbing the edge of the lens - despite being very gentle. The marks weren't shifting at all. Still puzzled by what could possibly have gone wrong, and quite resigned to the fact I'd need to replace the eyepiece, I gave up and reassembled it - but just before I put the eye lens back in, I again sprayed isopropyl onto a tissue and very quickly gave the lens a final wipe. To my amazement, it was instantly perfect and good-as-factory clean. No marks, scratches nor dust. Crystal clear. I finished the re-asssembly, and it was as good as new. I was utterly bewildered. But it turns out - athough your article doesn't explicitly mention it - neat isopropyl alcohol is also hygrophobic, which can cause all kinds of problems. I think I will take the unopened bottle I have of it, and convert it into your formula using a 65% solution of it (to make rubbing alcohol) mixed with ammonia, detergent and more water as you describe. Thank-you for this. Your book looks interesting - where is it available from?

Oh! - You've got the spherical 130 Explorer! The F7 - that might change things a little. I've got the 130P Explorer. What a different a P makes! Not the same scope at all. Apologies for the confusion! The Starguiders are still a good option but not the 3.2mm - that's too much magnification for an F7 scope. Unless you're feeling adventurous and have the time to dabble in buying/selling eyepieces, you might want to hold off upgrading and take your scope to a local astronomy club to try out other people's eyepieces in it. Because with an F7 scope, you're getting a higher level of performance out of the supplied eyepieces than I am familliar with, so I can't say how much improvement you've get by upgrading - and you've got more eyepiece options available to you at F7 compared to F5. Apologies again for my confusion.

As I say - I've got exactly the same scope (albeit now on a go-to mount), and bought it when my daughter was born, so I've spent thirteen years now buying and selling eyepieces for that scope, which has been an both an interesting and frustrating experience; as it has a focal ratio of F5, it means most eyepieces will struggle to produce sharp stars at the edges. At the same time as I bought the scope, I purchase a set of cheap, but reasonably good Plossls that came in a nice case and cost about £100. Similar kits are still available today and cost £150-£199. I even added extra focal lengths, but the short focal-length ones are almost unusable because you have to press your eye right up against them. They now sit at the bottom of a cupboard and haven't been used for years. They probably never will. I only keep them for nostalgia. Plossls like that cost £20-£40, but as FLO says: "best suited for telescopes with f-ratios f6 or slower" (plus as mentioned above, you have to press your eye right up against them in the short focal lengths) After many years trying many eyepieces, I'd say that the three cheapest eyepiece ranges that work well with that telescope are: Planetary II's - £38 Focal lengths less than 8mm are not very sharp overall and can suffer from glare when looking at the moon and bright planets Focal lengths above 9mm are not sharp at the edges (and don't seem to be made anymore - probably for that reason) The exactly same eyepiece optics are sold at a higher price as the Skywatcher Planetary UWA's in a different body with (sadly) worse glare issues BST Starguiders - £55 (sold as “Paradigm Dual ED” in the USA) Remarkably good in the short focal lengths, with (only minor) glare on the moon with the 5mm The longer focal length ones (the 18 and 25mm) are not sharp at the edges Celestron X-Cel LX - £89 Similar optical performance to the Starguiders but better/different build quality Some focal lengths are better than Starguiders, others may be worse The important thing to remember about eyepiece cost, is that optically (as people sometimes say) "the eyepiece is one half of the telescope" - they are precision devices that are difficult to make cheaply to a high standard. Don't waste your money on sub-standard ones - the Starguiders set a very good standard, at a very good price for what they are. If you're a bit short of cash, then build up a collection one eyepiece at a time.

Try drift alignment - that should fix it.

What method are you using for polar alignment?

The standard lid from plastic milk cartons is a good fit for some eyepieces.

One potential issue with those is that they're airtight, and as such might trap moisture in potentially causing fungal growth on the optics (I put a tiny bag of silica gel in mine, to be safe). Bolt cases on the other hand seem (deliberately?) not airtight so the eyepieces can breathe.