Jump to content

Banner.jpg.b89429c566825f6ab32bcafbada449c9.jpg

SiriusB

Members
  • Posts

    472
  • Joined

  • Last visited

Everything posted by SiriusB

  1. Guess part of me is still the 4 year old asking "why?" mercury 707 frac, cheap as chips, slightly floppy focusser, can't expect too much @ end of day. Don't anyone get too hung up about it, just trying to understand the star test. Works fine for what it is (cheap small low power scope), but a highish power star test shows a diffraction pattern like an out of collimation newt~ the rings are not concentric but drift off to one side. (old hands will know what i mean) Spent some time adjusting focusser & moving cell from one extreme to other, plus trying to get best allignment with a cheshire. Nothing seems to change the diffraction pattern. My two theories~ 1) lens wedge? but i'm thinking this would give spurious chromatic effects? 2) lens elements tilted in respect to one another? Guess this could be rectified playing with the thickness of the lens spacers~ maybe one is different? Can anyone shed any light?m Even if it's uncorectable i'd like to understand the cause. Thankyou. diffraction pattern drifts off to north of view regardless of what i do to focusser or lens cell.
  2. Part two of my reviews just to show you don't have to spend a lot to enjoy astronomy. This is out of sequence,it should be part 3 but more testing required on what should have been part2. part1 is here: I've managed to make it through most of my astronomy years with hardly a nod to the humble Plossl...until the last 6months or so. As most of my ep's are worthy if unremarkable Japanese old school designs, i thought it was high time i picked up some cheap ep's for field trips,quick peeks etc. My eye was drawn to FLO's Astro Essentials Plossls, as they were a) cheap & b) listed as FMC~ many of the cheap Plossls are only listed as fully coated. I find other things being equal, on DSO's at least, better coatings seem give a bit more contrast & a brighter image. I eventually ended up with a set of 7.5, 10, 12.5, 15 ,17 ,20 & 26mm AE Plossls, probably more focal lengths than you really need to buy, but @ £20 each, it didn't break the bank. Additionally 32mm & 40mm fl's are available for a few £ extra. 1st impressions. All metal barring the eyecups, nice chromed smooth barrel with no undercut, which i much prefer. They are parfocal, so only the slightest of touches (may) be required on focus knob when swapping ep's. The eyecups were a nice suprise~ generally i prefer no eyecup, due to long years without & also personally i have previously found an eyecup pressing on my eye socket uncomfortable.(everyone's different) from 7.5mm thru 20mm the eyecups are quite thin & flexible~no discomfort here. 👍 on that one, plus very easy to fold down should you wish to do so. I've used them with f5,f7,7.5,f8 & f12.8 refractors in the 70-150mm range. Nothing fancy. FLO's website recommends these ep's for f6 plus. Whilst i found them useable @ f5 i would caution that a significant portion of the field shows distortion(astigmatism?) ,though i strongly suspect in my st120 even an ultra premium ep would show some edge distortion?~ It's a budget fast achro. @ f7 plus, edge distotion is much tamer & i've personally no issues on that score. @ f12.8, as should be expected they were great nearly to edge. I don't currently have an f6 scope but previous experience suggests there's a big difference between f6 & f5 when using simpler ep's. Ok, next, Planetary & lunar~ quite frankly this was pretty good, comparing with my orthos maybe a little more scatter on planets but i didn't see any less detail on axis. Maybe on a first class night,with planets @ higher altitude i would. Lunar,very very good. On DSO's i found them bright & contrasty, I do have better performing ep's, but not by very much. minus points? On the odd fl, anodizing was not perfect, one ep had slightly jagged field stop~ this all seems fairly common with budget Chinese ep's, minor quibbles for the low price. The field stops were in sharp focus however, which is more important IMO. AFOV~i've not actually measured, but i get the impression lower fl's may fall a little short of 50 deg, longer ones maybe a smidgeon more. None are quite as 'claustrophobic' as a Classical Kellner or Orthoscopic. Minimal flare from objects outside FOV. ~a 'pass', as this is a pet bugbear of mine. If you wear glasses to observe the shorter focal lengths may well not suit~ plenty of info elsewhere on this site relating to that. If you are worried about eye relief, don't buy the shortest fl's 1st, work downwards till you reach your own comfort limit. Personally i find the 7.5mm comfortable. I'm actually ok with a 6.3mm Plossl, but i suspect Mr/Mrs average may find 7.5mm the limit for a Plossl & credit to FLO for stopping the range @ this focal length. I'm sure they could have boosted sales by offering shorter fl's, but many buying may have ended up disappointed. Ok, whether this has helped anyone i don't know. If you only have £20 per eyepiece to spend, these are great. I doubt you'll do better for the price. If you have a bigger budget, is it worth paying more? Maybe, ask lots of questions first. Bottom line~ i have been somewhat astounded with these £20 budget wonders. I didn't know what to expect,so i expected nothing & came away pleasantly suprised. If i only had a set of these ep's, i could be quite happy, i've been looking heavenward many years & these ep's show pretty much most of what my average scopes are capable of showing. On a personal note i actually enjoyed the shorter fl's more, though i suspect for most the middle fl's would be the more pleasing. If you have a premium scope, premium ep's may be called for, but again i have proved, at least to my own eyes, that you can enjoy visual astronomy on a budget. ~Particularly relevant with the recent Skywatcher price rise. £20 each, price of a good Chinese takeaway~ you should be smiling with these long after that takeaway's been forgotten. 😉
  3. This should be possible with your scope, depending on sky conditions. Previously I have seen the rosette from suburban skies on nights of excellent transparency with a ST120. It's about 1.25 deg dia. From memory i used 30x, i had no nebula filter to use, it was pretty low contrast against the background sky, but visible. On an average night,i would have had no chance. Once you have the central cluster in sight be patient & keep looking. How do you find viewing m33 Dominic?~ easier target,similar size againwith low contrast~a good practice run maybe?
  4. Rome wasn't built in a day....& a 'definative' eyepiece collection probably takes much longer 😉
  5. All interesting stuff, I'd not picked up on Betelguese possibly going pop~ glad it hasn't, one of my favourite naked eye stars... next to Sirius that is! 😉 Short session last night due to the below zero temps & wind chill. Sirius was errm.... shrouded in blue haze, guess i picked the wrong 'scope (ST120) for that quick session. Actually a long time since i pointed a scope @ Sirius~ forgotten how bright it appears telescopically. Suprisingly I've no recollection of the brightness in a 12" from 30 years ago.
  6. That's around 5mm exit pupil, pop it in your 130mm f6 & see how you get on? Yes a 2" will give you wider more aesthetic views. Conversely, as i slowly become a more critical observer, sometimes a narrower field of view enables you to see fainter objects, (less overall background light to the eye @ the expense of 'better framing')
  7. If you were happy with a 40mm before, please ignore my 2cents.
  8. Hard for me to say,I'm not over familiar with bortle scale, looking @ the scale i'd say i had bortle 3 or a little better skies in 80's~ Idid see m33 naked eye on the very best of Autumn nights with young eyes. I'm Probably bortle 5 @ best now. Maybe try 5mm exit pupil? Ideally you'd beg, borrow or steal some ep's of different focal lengths to try before spending a fair chunk of change.
  9. I have the 'old' mak 127, read somewhere the new ones have a larger mirror & larger dia tube?~ you'd need to confirm this with a supplier though. As a more allrounder i'd say the skywatcher. Planetary & lunar, the Bresser should be better,but i haven't owned one. Mak127 aint bad for DSO apart from the large ones~ performance somewhere between a ST102 & ST120, closer to the latter. Contrast is good DSO wise, best subjective lunar views i've ever had. Whichever you get, buy or make a dew shield~ pretty important IMO.
  10. Senior moment James .😆 Put me down for a set of BGO's@ £49 a pop too!
  11. I'm not sure this is so, i've seen that f ratio thing quoted in books by respected AA's. That dog don't hunt, as they say in the States. It's highly relevant to photography (or imaging as it's called in these more modern times.) An f15 scope @ a given exit pupil will give as bright an image as an f10 , f5 (or f1 for that matter)~ for visual use. I've certainly not seen any difference in the field regarding f ratios. As to aperture being they key, well it is....but not quite the whole story. Contrast is important for DSO's too. Hypothetically let's take two scopes, one has twice the light gathering of the other but the smaller one has twice the contast. Now i'll grant you it's hard to quantify contast, but stick with me. Ignoring any resolution advantage, & assuming the DSO magnitude is within the light grasp of both, what you see in both is likely to be about the same. Actually, it may be aesthetically more pleasing in the smaller contrastier scope. (Think old school TV~ turn the brightness dial up full & the pictures bright but washed out without fiddling with the contrast dial also.) Now real world, it's possible,(but unlikely) any scope will be twice the relative contast of another, so aperture is much more significant than contrast for practical purposes, but contrast is not to be ignored. I don't claim to know everything, so may stand corrected, but f ratio has very little,if anything to do with visual DSO brightness. Time that old chestnut was laid to rest. IMO
  12. ....I'd like to point out not everything's gone up.(Yet) Just by way of example, on FLO website "Astro Essentials Plossls", still £20 a pop, "Baader Genuine Orthos" still £49 each. No ,I'm definitely not on commission!, just chose those as examples because i think they represent excellent VFM @ their repective price points(or maybe a little more) So 'bargains' still to be had for the wisey monkey.😉
  13. It doesn't have to be an expensive hobby. As others have stated the cost of entry level is way lower than it used to be even with price hikes. I doubt Astronomy will be the only sector hit by price rises this year.🤔 Probably saved me some £,I've suddenly lost any great desire for a larger ED. 😉
  14. A few suggestions: Offcut of round stock from your local metal merchant~if you can drill a central 12mm hole in it ?, scrap yard? ebay? ready made from astroboot? Tin can with melted lead cast inside,should be easy to drill that.... then paint?😉 As a very amateur machinist, i've found buying metal of specific sizes aint that cheap these days except in bulk.... figuring in materials cost/labour time/postage etc counterweights aren't quite as pricey as they first seem. As it's a counter weight, best source is local due to postage charge. People have used concrete blocks, bricks & all sorts in the past, all depends on how much you value your hard earned £ vs aesthetics/ ingenuity/practicality. Lead is traditional i think (& vibration damping)
  15. I don't want to put you off, but with 40mm ep in an f6 scope you're nearly @ a 7mm exit pupil. Unless you've access to pretty dark skies you may be disappointed with how bright the sky background appears through this setup. For reference, in 80's darkish rural skies 5.5mm exit pupil was about my lower limit. Always found 10x50 binos better than 7x50's back then. These days in suburban skies, around 4mm exit pupil is about as low as i dare go. Everyone's different, but for your consideration, something shorter & wider may prove more practical??
  16. https://www.newscientist.com/article/2234991-we-really-can-control-the-weather-but-it-may-not-be-very-useful/ ~Random response. 😉
  17. Hello Duncan, " This is an expensive hobby, that's for sure. "~ It certainly can be!, but it doesn't have to be. Have you used a telescope before? Just wondering about the wisdom of spending a substantial sum of money at the off if this is all new to you? As to the ED80, it can be a good visual only scope, but as someone else noted it depend on your expectations. I own probably one of the oldest ED80's in the country 😎,only ever used it for visual~ bought in 2004/5 i think, after a rave review by Ed Ting in 'Sky & Telescope' (2003?) of the Orion Telescopes version.(Sorry,I can no longer find this review on the interweb to link.) As soon as i knew Skywatcher were offering it i rushed out & bought one.😳 From a dark site it's pretty good,but most of it's life has been spent 'pushing the limits' of what's observable from suburban skies. High contast scope, but only 80mm. Probably not most peoples idea of visual Astronomy, but i feel it's honed my observing skills. Would i like a larger ED scope? Sure, would I reccommend you get a larger scope? Sure. I will never sell this scope. My advice would be ask more questions, do more research before you part with £. In happyier times i'm sure SGL members in your locale would be happy to let you view through their scopes to help you decide, but looks like that's unlikely to be possible for some time yet.🙁 Seems a fair few of experienced observers on SGL favour a quality 100-120mm ED/apo for visual observing. Worth noting & maybe asking them 'why'? Kind Regards.
  18. I have owned the evostar 120 twice~ guess i must like that model a little. My 2nd one is a keeper. Against good advice from SGL i bought a used evostar 150. I like that also, but it's a big lump to cart in & out~ which is what the advice pertained to. The weak point of the standard evostars for me is the focusser, which can be changed, but at additional expense. If you have the money the 120 ed pro is better with a much smoother focusser. It's not 4x better though.but is 4x the price! Have you factored in the cost of a mounting? 120/120ed on an eq5 is minimum for visual use IMO. Ideally you'd get something bigger & heavier & more stable. There's a reason i've stuck with the standard 120, It's a pretty good visual scope for not a massive amount of money. A 120ed could be a 'for life' scope though.
  19. Are you intending this for imaging? I had a 100mm triplet once, long long story about that(some other time), but this was for visual use. All i knew back then was triplet was better than doublet. It took like forever to cool,(my mak 127's quick in comparison) I would never buy another for visual use. Others may differ?, but at least consider this ~unless you're set on imaging.
  20. Sept2020 to present appears to have been a particularly cloudy period, least from my backyard! Yet to observe m42 this Winter without moon glow. Usually it's 'let's find something else, i've seen m42 enough' Usually you'll get a glut of clear nights somewhere along the line though (usually when you can least use them 😉) so don't get too despondant. I think my first proper years observing in the early 80's & the only one i kept proper weather notes for was basically cloudy January thru March! 2003 late Summer,nearing Mars' closest approach, seemingly night after night of clear weather....& i was working nights!!😦 Ended up taking an ST80 to work for my dinner break~my colleagues were quite impressed with the red planet till the security guy spotted us all on cctv & attempted a rugby tackle. 🤣🤣 Swings & roundabouts UK weather wise.
  21. Back in the Summer I obtained a new 'capricorn 70' ota for the price of a cheap eyepiece, around £30 plus shipping. I guess i wished to revisit my 80's roots with a small refractor. Certainly it was an 'impulse' buy, i didn't really need one. At f12.8 this is the 1st achromatic refractor i've ever looked through which could be considered genuinely achromatic, ie it meets & exceeds the 'sidgwick standard' by a significant degree. 1st impressions were it was very lightweight & rather a long tube for a small scope. The focusser being partially plastic is a weak point & not ultra precise, but given the 'lazy' focussing of long focal ratio instruments proved adequate under the night sky. I wasn't expecting much for the price, after 1st light a couple of minor modofications were made before a more extensive evaluation. The two m3 bolts provided for attatching a RDF were removed,then the holes carefully tapped out to m4 which enabled a SW finder shoe to be fitted along with a 6x30 finder from the 'parts bin' The inside of the dewshield was unpainted & very shiny. I flocked this, along with the 1st section of the tube (to the 1st baffle) with FLO's flocking paper.~much better! Now to the night sky, lowest mag & max field of view were 28x & 1.75 deg approx with a 32mm eyepiece. I found even @ 120x or 142x on a suitably steady night, Jupiter still gave remarkably good views for such a small aperture. The moon was, superb. I have yet to see any discernable false color in this scope,( with these eyes), regardless of mag or target. Note, it's not an apo, always an achromat appears to very slightly yellow the view (to me) compared to the view through say an 80ED. As my backyard is now not terribly good for DSO's the 70mm aperture struggled a bit on these, but suprisingly good views of the brighter ones were still noted. The long focal ratio meant any eyepiece abberations near the edge of field were very minimal. Basic ep's worked well! I've yet to do a direct head to head with my 80ED. Yeah sure the 80ED is better, but @ 10x the cost it's really not that much better optically. Mechanically, there's a big gap. I've been using it on an az3, which is adequate, but the long tube length makes focussing a little wobbly north of 100x Summary: I've really enjoyed using this scope, without a doubt the best 🙂 per £ of any astro equipment i've ever bought in all my astro years. No really! It's probably not a 'serious' scope, but i think it's a keeper. Very lightweight, would make a great,cheap grab & go. Your only scope? I don't know. It would however complement something larger for those 'quick peek between the clouds' sort of nights. Not sure about the eq1 mount it normally comes bundled with (do your own research) but the ota gets a big budget thumbs up here 👍 I really have been quite suprised......Don't cancel your Takahashi order just yet mind.😉....... Part2....some budget ep's......???
  22. Thankyou all for your replies on passbands~ & especially for your comprehensive reply Don. Genuinely learned something from the responses. 👍
  23. Maybe a History of 'Astro Systems' is also in order? I remember the catalogue,Vixen fluorites et.c I bought a few bit's from Astro Systems' in the 80's,~ some i still have~like 'astro systems collimation plug' (with clearest collimation instructions ever IMO,these (now tatty) instructions still reside in my Nortons'), vixen 36.4mm kellner, an m42 eyepiece projection thingy....
  24. Remove the screw holding the clutch lever on, carefully pull the lever off the clutch shaft,it may be tight. You can then rotate the clutch lever a little (shaft is splined) to allow a bit more movement for tightening clutch. Generally,don't overtighten the clutch, it will wear quicker. If you can get your scope balanced really good you almost don't need the clutch~a very light tightening should suffice. Hope that helps.
  25. Thanks John, that's interesting & sounds expensive~ thought a cheapie would be all i'd need.😉
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.