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jefrs

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Posts posted by jefrs

  1. Hello Jefrs, Sorry to hear of your problems with arthritis and your need edit (although we all make frequent mistakes). If you click the "more options" button at the bottom of your post before sending it, you will see a "preview post" option which may help.

    The reason for the restriction in editing is because there were many people abusing this option, posting inflamatory/rude posts and deleting them before they could be brought to admins attention. We hope by the time someone reaches 250 posts they have proven themselvess to be serious about obeying the forum code of conduct.

    Nobody really cares too much about some spelling mistakes, and if you type something that is wrong (eg "I do care" instead of "I do NOT care") contact a moderator and we'll sort it for you.

    Thank you for your understanding

    Thank you for rplying. I'm sad that you had those problems in the past but its seems the current inhabitants are perfectly polite. Imo is it now a silly rule.

  2. +1 for this advice. Might be something you want to look at in the future and the scope will handle it but you only get to make one mistake with the sun and its goodbye to one of your eyes/your equipment etc. Best be careful, get used to the scope, your routine, etc. and then research once, twice and thrice again.

    Hope you get clear skies!

    Will

    Good advice but :-

    An eye surgeon told me in all seriousness that no one, no one has ever permanently damaged their eyesight by looking at the sun through a telescope because we have a blink reaction fast enough to stop burning (confirmed by our senior laser safety specialist) and our eyes have an emergency shut off mechanism; they literally switch off, both of them at once: you may go temporarily blind until your eyes decide you have stopped doing that and they have regenerated the visual purple you have just destroyed. I'm a physicist and have to know stuff like laser safety 'cos we use nasty ones, and hence go on specialised courses, meet interesting people and discuss stuff with them.

    Be warned - the eye surgeon also told me it hurts, a lot, and you will be blundering around sightless until carted off in the ambulance. Not goodbye eyesight but au revoir for a week or so.

    Best cure - don't do it, bad case of stupids. "We can do fool proof but we can't do blumming-fool proof"

  3. I was able to use the GH4's focus peaking confirmation very effectively on the moon last night. I don't know what functions the Sonys have but expect similar.

    The telescope focusser is rather coarse and has backlash which means it goes out of focus as soon as I let go the knob unless I allow for that.

    I am still having difficulty getting the combined lens systems close enough to the secondary mirror to acquire focus with the mirrorless MFT camera. I resorted to removing the eyepiece adaptor to fit the T2-M43 with the eyepiece holder inserted upside down inside the focusser: there must be a better solution?

  4. To keep it simple, take the whole cap off don't worry about the smaller inset apertures.

    Other then the moon you will want the full aperture for everything and you can get long with full aperture on the moon if you don't mind it being a bit bright and leaving a residual image on the retina for 30 seconds. :grin: :grin: :grin:

    If the moon is too much you can get a 30% or 50% moon filter.

    Some scopes are also for land (such as our 130SLT) hence giving us a ≈42mmØ hole (I used the calipers this time :-) )  = f/15-ish or three whole stops (EV) reduction (but note I often miscount count f-stops ;-) )

    It's a pity they didn't put a T-thread on it (M42) for a filter. It works well in daylight.

    Slightly OT - Samyang aka Walimex/Rokinon make reflex lenses and others with T-threads which then screw into your camera mount adaptor ring. Filters for these incl ND are made for the back end of the lens, on the T-thread because the front element is over 10cmØ and would be very expensive filters.

    T-mount :- It may be "T" for telescope but it is an old lens fitting and actuall stands for "Tamron" or "Taisei" and used on many cine lenses too. M42x0.75 (T) or M42x1 both are iso-metric but one is our T-thread (T2) the other (1mm pitch) is Praktica/Pentacon, "Russian" (not it's E.German Zeiss) and Contax (Zeiss Ikon), etc. Ring/flange marking T and T-2 (T2) are identical fitment. The "T-ring" has (3) grub screws around its flange which allow the optics to be rotated so the picture is upright (ok it doesn't do that but you can get screws and/or camera where tyou want them)

  5. My Celestron 130SLT has two lumps on the cap but only one comes off, the other lump is a holder seat for the removeable cap.

    I queried this with a seller and was told that at one time Celestron sold a dark solar filter for the small hole but this was not considered a good solution; discontinued.

    And that biggest problem with reflector for solar was burning the secondary mirror with focussed sunlight (it needs a filter before it gets there then)

    sums -

    The 130SLT is a 650mm so 650/130 = f/5

    The cap is guesstimate 50mm so 650/50 = f/13 i.e. a reduction of roughly 2.1/2 stops : suitable for viewing a bright moon.

  6. Hi guys,

    Recently received a Celestron 114EQ telescope as a present, and then went and bought a Sony DSLR for taking some pictures.

    I understand I need a T-Adaptor, and was wondering where the best place to get one might be?

    Is something like this what I need?  http://www.ebay.co.uk/itm/Sony-DSLR-camera-T-Ring-To-mount-Sony-cameras-on-telescopes-for-digiscoping-/281023473942?pt=LH_DefaultDomain_3&hash=item416e4de916

    Also, does that take away from using an eyepiece for magnification?  Or what do I do about that?

    Silly, obvious, basic question no doubt.

    If Sony is mirrorless and not DSLR then the sensor may sit too close to the scope's secondary mirror; a spacer tube may ne needed.

    I gave my wife a 130SLT for Christmas but being half engineer I get to do the Meccano job on it.

    But I am having a right 2&8 getting my GH4 mounted on the focusser with or without an eyepiece even with 'correct' spacer; this is of course mirrorless and micro four thirds (M43 mount, not a metric screw thread)

    Best solution so far has been to use the scope tube as prime lens with the eyepiece holder unscrewed which leaves a T-thread exposed for the slim (no spacer) T2-M43 adaptor; the 130SLT focusser has a fairly long throw, even so I am almost fully in at the focus point; with the provided T2/1.25-in adaptor in place the camera image is heavily vignetted.

  7. A soft gig bag for a guitar or bass (I have a collection) would probably take tube and tripod both: these are quite cheap and most have zip side pockets for O&S; various sizes - acoustic or jazzbox are largest volume.

    Drummer's bags tend to cost more (& wrong shape) because they're heavier duty; the kit weighs a ton as I know form helping load in/out

    I cannot think of a reason why one should not drill a couple of small holes in the tube at CofG to fit a steel loop drawer-pull handle to carry the tube with.

  8. Do not leave the telescope outdoors. Not in England.

    It will get soaked with rain and dew and be destroyed. You can put a bike under a bike or barbecue cover but they still get damp, no good for a telescope.

    After use they need to be aired out to remove dampness from dew (and ice) in a nice dry heated room. You may have an utility room, conservatory or even a heated shed.

    Failing that break it down and haul it in. Don't pack any of it away until it is thoroughly dry.

  9. From the Celestron website

    "It appears that your hand control is stuck in programming mode. 

    Fortunately, it is an easy fix:

    1. Cycle the power of your scope. This will often clear the condition.

    2. If you have an RS-232 cable (the cable that attaches between your computer's serial port and the port on the bottom of the hand control) you will be able to download the HCupdate program that will allow you to reprogram the hand control. This is available for free download off of our web site, celestron.com/downloads

    Complete instructions on how to do the reflashing are elsewhere in the Knowledgebase, “How to Flash Update your Hand Control and Motor Control Firmware“.

    If you are unable to program the hand control or this problem continues after attempting to program it, your hand control needs to be replaced.

    Updated 12/25/13"

    HTH,

    Neil.

    Point 1) "cycle the power on your scope" translates as pull the batteries out for 20 minutes. This works for most high tech toys, or do as NASA once advised an astronaut to fix the Hasselblad by "assist with lunar boot".

    Point 2) the RS-232 cable is not an RS-232 connector it is an olde and most ancient RJ12 telcon as once used for wind-up modem connection, the ones that went, "biddle-iddle-iddle-diddle-dong-bong-blart!"

    We need a RJ12 to RS232 and then serial to USB cables, but we need special Celestron 4-wire flavour plus software to drive that USB to serial link (should come with cable).

    There is a WiFi USB dongle thingy for NexStar that may do it to iOS etc (I'm a bit dubious on that)

    In terms of firmware and connectivity the Celestron/Nexstar is pretty old hat. Having got a nice new Windoze 8.1 Pro laptop, I may have to dig out the elderly Win98 Dell Inspiron with the dead battery to connect to the telescope.

    OTOH small M$Windoze laptops are pretty cheap these days, but they don't have RS-232 serial ports now.

  10. Ok I understand, sorry I didn't provide more info.  The reason I didn't though is because I'm not really interested in buying a telescope just yet, considering I live in a dorm room, and also don’t have much time to spare in terms of going outside and setting up a telescope.  Next year when I move out of the dorms and into a house, chances are high that I'll be much more interested in buying a telescope and setting it up in our yard or something along those lines (my classes will hopefully be winding down next year also, so I’ll have more time).  

     

    Right now though, I do have time to spare occasionally to read or do research, especially since I'm in the library and on my computer a lot nowadays doing work.  So basically like I said, I'm really just interested in expanding my knowledge on the night sky.  Learning the more general ideas so I can actually get started and find out the specifics that I'm more interested in, so maybe I can concentrate on certain areas more.

     

    Also, a little more specifically, I want to learn more of the technical and science side of the sky.  How planets and stars are formed, why they are where they are, what certain ones consist of and the different types of things out in space. The technology used to study and travel into space and how the technology works.

     

     

    Does some of this help? Let me know if there's any more info I can provide.

     

    Thanks

    Next year when you move out of dorm you won't have any money for telescopes. On the grounds no student ever has any money.

    You may be on the wrong course. Talk to your college re your interests.

    You don't say which college? Whereabouts?

    Does your college have an observatory? Many do. Try to get some time there or at least talk to that department.

    Your college should have a library, this should be like a kid let loose in a toy shop.

    Colleges often have interest groups like astronomy societies.

    etc etc

  11. Being a student, going from high school to university college, the main difference is now you have to learn how to learn because at school it is spoon-fed to you, now you have to research your own material.

    It's no good going at it like a fart in a colander, every hole at once, you have to decide what it is you want to study: you have to pass a course and your tutors should be advising you.

    I'm a retired physicist-engineer. A bit of my work went into Concorde and NASA's space shuttle. Astonomy is physics but astrophysics is all heavy-duty mathematics (except they can't do statistics). The physics came from college, the mech/elec.eng from earlier apprenticeship and garnered through work later with a side-order of polymer chemistry.

    Keep at it but focus, put everything else aside until you graduate. Good luck.

    • Like 1
  12. Light polution here too but ti doesn't have to be a problem so long as light does not fall directly into on the tube all should be well.

    I can set up in the garden and even observe nebulae withing 4 metres of a sodium-yellow street lamp. Not ideal but it does work.

    Memo to self, I must ask the council to hood that lamp.

    For better viewing one simply transports to the nearest woodland or heathland clearing where the foliage shields out the urban lights.

    We can even find such spots within the town proper but better to go a few kilometres away and up onto the nearby (Newbury, England) downland.

    Problem there is our National Truss like to lock car park gates at dusk to stop "vanadalism". I'm a bit puzzled by that.

    • Like 1
  13. I would not consider using water on any mirrored surface because water is the chemist's universal solvent, it reacts with everything and the mirror is mostly aluminium, a very reactive metal and would be oxidised by the air if it was not given a very thing protective coating. Contact with air or water will instantly turn aluminium into alumina Al2O3, also known as sapphire or emerald, one very hard and utterly useless mirror.

    I have eletroplated and sputtered enough stuff (including gold plating safety specs, don't ask but there was a good reason) to know to only use good iso-propyl alcohol or one of the new didgital camera sensor cleaners on such delicate surfaces with a very soft grit-free mop. And that's only if the blower and camel hair didn't shift it. You should not be able to get grease on the mirror: Sod's Law and Murphy's Law say otherwise.

    Probaly better to leave a speck well alone than scour the mirror trying to remove it.

    If you must handle a mirror lens then wear cotton 'museum' gloves (cheap at industrial PPE stores) because rubber lab gloves (available in blue or tranlucent white) can and will deposit their plasticiser precisely where least wanted. The same industrial PPE shop will also sell you as many rubber gloves as you can eat.

    Post war some of our chaps got their hands on some German U-boat schnorkel lenses and one now nameless lab tech helpfully washed them in water. Only to find that the clever chaps at Leitz had made then from common salt NaCl, oops.

  14. Coming from photography too, it can seem counter intuitive that my 25mm eyepiece is the wide angle and a 9mm is the telephoto.

    Divide focal.length of scope by focal.length of eyepiece to get magnification factor :  read the sticky on eyepieces for advice :-)

    Mine by example  650/25 = 26X and 650/9 = 72X

    But our 130SLT telescope is 130mm therefore 650/130 = f/5 which is probably the limiting maximum for eyepiece here i.e. 650/5 = 130X

    Limiting factor at the other end is pupil dilation, we're both getting on (pupil <5mm) so the 25mm is probably as wide-field as we want.

    I am finding the telescope is great for observation but trying to fit a camera to the eyepiece is a bit of a nightmare: there are better solutions; long-long reflex lenses; piggy-back tracking or camera's own eq mount.

  15. I put "sucherfernrohr" into Google and got a huge number of hits for finderscopes for sale, in German.

    They all seem to be more up-market versions than the red-dot gunsight on the Celestron 130 we have.

    But they are out there :-)

    I have noticed that optics sell for ludicrous prices in Germany,  approx 50% more than same thing in the UK - German Ebay sellers must wonder why they can't shift stuff over here in blighty.

  16. An old "ROWI" camel-hair lens brush which lives in a tube with a cap. Camel hair is softer than the usual squirrel hair artist's brush.

    Polyester is related to protein and therefore absorbs grease, therefora a polyester lens cloth.

    Lens tissue also sold as industrial "precision wipes" e.g. "Kimwipes" are super-dry tissues that feel harsh but are not.

    There are two types of air-duster, compressed air (best) and cheaper propane/butane which can jet freezing liquid all over the place.

    Iso-propyl alcohol is used as lens cleaner but cheaper in 500ml can. It should evaporate without leaving any residue, safe on most surfaces.

  17. My friends at NPL (National Physical Laboratory, UK) operate what is probably the world's most accutate Standard Clock at present and which provides their UTC(NPL) service here :-

    http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/time-synchronisation-of-computers-to-utc%28npl%29

    The page is a couple of years old but their atomic clock is brand new and they were showing it off at their Centenary 'do' I attended last year (I was running an International Primary Standard then, since retired). A similar service is provided by NIST for left-pondians.

    Do note however that if you link you computer to the NPL (or NIST) time server(s) then Windoze may (will) object as it likes to be linked to M$ (which is out by a few ticks)

    And iOS will only link to Cupertino time but your telescope may appreciate accurate positioning ... enjoy.

  18. It is raining now but the worst of it is that it is completly overcast.

    On astronomy reading matter I have to reccomend anything and evrything by Sir Patrick Moore. Not only extremely knowlegable but also a very good writer.

    Currently delving through Patrick Moore and Pete Lawrence "The 21st Centurey Astronomer" ISBN 978 1 78177 125 9 sub titled "The Practical Guide To Observing And Photographing The Moon, Sun, Planets and Stars In The Digital Age" basically everything you never wanted to know here and it's bang up to date.

    Sadly I only got to meet him the once.

  19. I have only been here a short while and I have arthritits, I typo frequently and need to edit posts regularly.

    Why on earth do you force newbies to post 250  times before they =cam edit?

    No other forum does that and th einhabitants here seem reasonably intelligent and well mannered enough that editing a post would not be a problem.

    Daft rule.

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