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jonstarrysky

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Everything posted by jonstarrysky

  1. Have ordered a premium 1/10 wave secondary and want to make sure the method of mounting is optimal. For 63mm minor axis it is a rather thin 10mm plate glass, so may distort slightly under its own weight. My holder is the basic stalk/ post design that holds the mirror beneath it with silicone, rather than holding the mirror at the edge within a casing. Dogma is use 3 small blobs of silicone, and use 1-2mm removable spacers whilst the silicone is setting. Easy. What is less clear is *where* to put the blobs on the back of the mirror. For a 3 point *primary* mirror cell 70.7% radius gives the most equal distribution of mass across 3 support points. PLOP will say 40% of the radius is better - the deformation will be greater than 70.7% but is mostly compensated at the focusser. But we dont have a PLOP model for secondary mirrors -which are obvioulsy eliptical and orientated at 45 degrees. Can anyone advise on where to best place the 3 blobs of silicone to minimise the effect of the mirror deforming under its own weight ?
  2. Russ, can you tell me the site location. I am in Oxfordshire but dint mind travelling to join like minded visual astronomers :-)
  3. 21E would make the 26T5 + 20T5 combo redundant. The 21E gets the best of both worlds - similar TFOV as 26T5 and similar mag as 20T5. But ....sometimes its nice to have choices of magnification. 21E is also not fully corrected by paracorr-I. Also somehow the smaller TFOV is easier to view for extended periods, for me at least. Look ...I am just struggling here, the 21E is calling.
  4. OK anyone got the 21 Ethos ??? I have the 20T5 - same magnification and 20T6 - same field. I dont intend selling either. Does the 21E really add that much to this line up ??? As shockingly good as the 13E is, I find it hard to look thru for extended periods.
  5. Anyone own the 22T5 and 20T4 and keep/ use both ??????
  6. Delos, sounds like some April fools joke. I dont get it,
  7. offset. I guess same for same is simplest if it is an upgrade. But I have on best authority that the offset is unnecessary. Secondary holder stalk/ post can just attach at the centre of the back of the sec mirror. On my stock secondary it is attached with an off-set, causing the secondary to be shifted away from the foucsser. I am glad OO secondaries have good reputation. I am buying a 1/10 wave one. Do ppl feel the 10mm thickness is OK ?
  8. wasnt sure where to put this thread.... Are they putting out good secondary mirrors, with good coating ?? Thanks Jon
  9. Any feedback on secondary mirrors for Newtonian scopes from OO ? Ta, Jon
  10. very pertinent thread, as it is typical that backyards in the burbs are little use for astronomy. I get out to a rural dark site(s) and the astro experience is much better. But takes a bit of getting used to alone and some research to get a site that lacks disturbances eg: lads razzing about in their hot hatch. I have close at hand a bright torch (it is metal so in theory can also be used in self defense), car keys and mobile. Of course these will v unlikely be needed..... Choose your spot well, and you'll find somewhere with little hassle.... My experience is it needs to be somewhat obsure and small e.g. not a big national trust car park
  11. Which season, Good question. The weather this winter has been dismal for astronomy. Dogma that winter is best has lost it in my books. The few nights I got out were invariably marred by dew....Any season when the conditions are good is my answer. Dogma that mid summer is no good, is also wrong in my books. Just need to get out late and enjoy, lots to see, milkyway bright, and the warm is more comfortable....
  12. Sorry to read of the bad luck Moonshane. If you have (or plan) a fast newt and have a serious EP collection and have the cash, paracorr is a no-brainer IMO. Of course as you say, trying is best if you can. I'm sure u can get by without, but the way I look at it is I already pay top dollar for Televue glass, so I may as well go all the way. Ethos is corrected to the edge by design, and you pay for that privelege. But on a fast newt that edge performance will be masked by the coma. You will see optical performance enhancement over a broad range of f/ ratios in Newts - there is a hand plotted graph plotted by Al Nagler that shows this well (will be on televue site somewhere).
  13. Hi Moonshane, well it was a full moon and there is only so much lunar observing that one can do.... so I tested 26T5 +/- Televue Paracorr in my f/4.7 Newt, swapping the paracorr in & out. Target was beehive cluster, which coped with the moon-lit sky. I definitely prefer the 26T5 view +paracorr; stars appear tighter to my eyes. It's just easier to visualise as point sources across the field, no careful eye positioning or patience is required. But this will be highly subjective possibly dependent on eye sight, scope optics, skills as an observer etc. I experimented also with the 13mm Ethos, which I felt gave a more text-book coma situation. Minus paracorr, the stars to the periphery were markedly suffering from coma, distractingly-so to me, tell-tale coma star pattern is always there no matter how you position your eye etc. Stars in the centre were sharp. With paracorr, the stars are just crazy-sharp all the way to the edge. I never quite get over how tight they are, even close to the 100 deg AFOV periphery. Personally having the ethos on a fast newt minus paracorr and you're missing half of the wow factor.
  14. Has anyone been "wowed" by M31 ?? The best I've had was with 15x70 binos. Doesnt seem to respond well to aperture, its just too large. There are dozens of galaxies well placed in the sky now (closer to zenith) that I'd prioritise above Andromeda in a telescope. I guess M31 has the novelty of being a close neighbour...
  15. re paracorr, I have mine in the focusser all the time so cant comment accurately on 26T5 performance at f/4.5 *minus* paracorr. All I can say is 26T5 is pin-sharp till the edge with paracorr. I never regret buying my paracorr, but others get by in Newts of these focal ratios happily without paracorr. If you want I can check out 26T5 +/- paracorr at f/4.7. Technically speaking from Televue data, paracorr will copmpletely eliminate coma in the 26T5 at f/4.7. But how much is there to eliminate I cant say.
  16. Just remember the highest power thing is subjective ! You may wish to experiment with cheap plossls before splashing out on a top-end eyepiece for high mag work. You'll see a fair amount of planetary detail with your 13mm Nagler and the mag that gives you will always be within UK seeing conditions, be it a good night or a bad night for seeing. 8mm EP should be safe enough for most nights. Below that is getting into subjective territory were opinions will differ - even between ppl observing at the same site on the same night, as to what ppl enjoy looking at.
  17. The 8Ethos with paracorr gets me around 173x mag. If I go higher there will not be any real benefit, you wont see more, you'll just see the same thing but it will look bigger and more blurry and the field of view will be smaller. Thats UK seeing for you ! Others will claim differently. But seeing is the limiting factor for magnification in my scopes, not the theoretical liimit of the scope based on aperture (eg 50x per inch). Personally 20-30x per inch makes more sense anyway. Going above 200x isnt my cup of tea.
  18. ....mottling in M82. Thanks for that Talitha, will take a look. I like the Harrington book Star Watch, it lists the DSO with a visual rating, so will prioritize ones that are xxx and xxxx. Sombrero (M104) and M51 give up some detail and he rates as xxxx. How about magnification for galaxies ??? Exit pupil of 3-4mm unless if very big eg M31, M33 in which case use widest poss eg 5-6mm exit pupil ...??
  19. my best tip, wait till autumn, M31 is better placed in the sky then. When you do find it, which is easy when you known how, dont expect to be overly impressed. Expect to see a featureless oval of fuzziness, with its satellite galaxies (spots of fuzz). There are plenty of spring galaxies out now that will give better interest eg M51, NGC2903, Leo triplet, M81/82. Galaxies benefit from Dark skies so I'd take a trip outside from London.
  20. I got the acclaimed Antares 1.6x barlow for my 13Ethos. It was imported from US vendor - not available in UK at the time. During the long wait (customs etc) I though what the hell and just ordered the 8Ethos from a local dealer. The Antares ended up being used *once* confirming the fact that paracorr + ethos + barlow is just too crazy. It is mint condition and I should sell at some point. Love the big lenses. 24pan is the best EP for binoviewing. I have used several sets of televue and denk EPs for my MkV and DenkII binos. 24pan is top dog. As well as optical quality it is "comfortable" to use, a less well defined characteristic. If one was building an EP collection around 24pan and 13Nagler..... Well 24mm is giving you an exit pupil that is getting on the big side on an f/5.9 dob = washed out sky. It is fine but dont go too much longer. To get bigger TFOV (if you really need this) increase your AFOV eg 26Nagler, 21Ethos, 22Nagler (27pan at a push). They are all good. My preference is 26Nagler. Planatary: think about an 8mm EP as the next (possibly final) step up in mag. On my 10" dob I get no real benefit from increasing the mag beyond this - "seeing" in the UK !!!!!
  21. Any suggestioins for a top 10 (or more!) ? Like many others I have observed scores of galaxies in my modest sized scope (10"). But have I seen spiral arms, dust lanes, structural details outside the core etc ??? - the answer to that we all know the reality. There are a few exceptions eg M51 averted vision some perception of spiral arms. The other day I was picking up details in the outer regions of NGC2403..... Suggestions folks ? Or do I resign to seeing only the fuzzy core when it comes to galaxies ?
  22. I got the 20T5 recently after much indecidion vs. 22T4. Now I want both !! Because I already have 26T5 it made sense to jump to 20mm rather than 22mm...... 21 Ethos would make most sense, but I felt it would disturb the harmony in my eyepiece case, some serious foam cutting would be needed..... Apparently the 20T5 optically has a slight edge being a more modern design and better corrected, but they say the 22T4 is more immersive with its huge eye lens and long eye relief. I like the 20T5 I must say, very easy to use and very sharp, eyerelief a tad tight, but not enough to spoil it. Interestingly I have a Denkmeier EP with 68 deg AFOV and 20mm ER, and I find it equally immersive to the 20T5 with 82 deg AFOV. A big eye lens and long eyerelief might make things more immersive.....maybe this needs more examination....
  23. I've been using the 26T5 + paracorr in my 10" f4.7 Newt for several years now. It is a winner eyepiece. Stars sharp as pins across the field. Wide true field of view. Comfortable to use eg eye relief, seeing the full 82deg AFOV etc. Great for feint galaxies, large open clusters, large nebulae etc Personally even 26mm is a bit long for me on an f/4.7 scope, exit pupil will be 5.5mm (but smaller with p/c). You really want dark skies. But definitely superior to even longer EPs such as 35mm Panoptic or 31 Nagler at that f/ ratio which will give a sky that looks even more grey. The exception will be looking a the veil with a UHC filter.... I had the cash but the idea of losing my 26T5 in favour of the E21 (slightly bigger true field, better contrast) didnt appeal to me. 26T5 is to stay in my collection as the daddy.
  24. Hey I'm loving this thread, "compare my Maplins case to yours" kind of thing going on. I'm a bit of confused, some show the pluck foam stuff to be quite robust and others a bit wobbly and all over the place. Does anyone have thoughts on organic matter from the foam condensing on optics over long time periods, there is a posh word for that I forget. I guess as long as the case gets opened from time to time to let the vapours escape.....I actually prefer this non water tight design to Peli cases.
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