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jetstream

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Posts posted by jetstream


  1. On 10/11/2019 at 19:27, Harmony Smurf said:

    Curious if anyone has had the opportunity to test the 18mm Tak abbe ortho with glasses on.  The eyepiece isn't common where I live so I can't test before purchasing it.  I wear glasses for astigmatism and also generally observe with a binoviewer. 

     

    thanks in advance

    The 18mm orthos have about 14mm of eyerelief. I have 2 Tak 18mm orthos that I use with the Denk Binotrons- they are very good. However I find myself reaching for the 25mm and 32mm TV plossls more often than not for the binos/powerswitch. The 32 TV plossl needs the eyeguards IMO.

    • Like 1

  2. On 27/10/2019 at 05:26, mdstuart said:

    Update on dewing in the shed.

    Good solution Mark.

    I took a bit different approach that seems to be working well for my shipping container. We painted it a gloss white that I'm told is 90%+ reflective  (any gloss white is apparently).

    So far the 24" mirror is within 4 deg f or less of outside and with a temp gradient across its surface of 34.3 deg F on the edges to 35 deg F in the center, +/- .1 deg F. When testing the gradient the mirror was within 2 deg F  of outside the other day. It might track better in the cold than the heat.

    Without the white paint the temps with the stock brown were 140F on the surface when 85F outside. With the white paint the surface was ambient + a couple of degrees.

    My brother in laws seacan has massive condensation problems, and has installed large vents and fans. Vents can pull in humidity...his sits on wet ground, partially in the shade.

    I put the seacan on a crushed rock pad, graded so water flows though it and it also sits on treated 6x6's. The stock sea vents are used. Zero dew so far Mark.

    Sorry to ramble but I'm always interested in passive climate control for scope buildings.

    Eagerly waiting scope reports and very nice cell btw!

     

    • Like 1

  3. 10 hours ago, bond19 said:

    Basically, once collimated using the cap, and then collimated using the laser (and lastly doing a final check with the cap). Suddenly everything looks totally out of alignment?

    Your 12" f4 is going to need some precise collimation, at least my f4 scope does.

    I use a sight tube to center the sec under the focuser and then use an accurate laser to line it up on the primary center marker.

    Then a cheshire to line up the primary or Glatters TuBlug/laser.

     

    • Like 1

  4. 7 minutes ago, bond19 said:

    I (think) I had the secondary collimated using the colli cap. Then I inserted the laser to align the secondary with the laser dot in the centre of the primaries doughnut. So far all good. Then I collimated the primary using the laser. Again all good. Finally I reinserted the colli cap to check and everything seems massively off 😞

    Whats it look like to seems massively off?

    The easiest,accurate way to collimate is with a cheshire/sight tube combo tool IMHO.

    https://www.firstlightoptics.com/other-collimation-tools/astro-essentials-cheshire-collimating-eyepiece.html

     


  5. 16 minutes ago, bond19 said:

    I’ve read the website advice, I’ve watched the YouTube videos. Yet I’m still having major problems collimating my OO UK Dob. I’m using a collimating cap & laser collimator. 
     

    Is anyone near or around the Blackpool area who can meet and show me hands on how to correctly collimate my scope? I’m losing the plot!!
     

    Thanks 😊 

    What is happening exactly?


  6. 30 minutes ago, domstar said:

    @jetstream I use my 32mm plossl with a UHC. I have an Aero 30mm which shows a larger field but is 2 inch so I can't use my filter. It actually showed up non filtered on Thursday, which surprised me. I wish my Baader plossl had a bigger FOV. The sky is Bortle 4 - east is good for nothing but the Milky Way is clear. 

    The Veil gives me a real thrill and is the dso I linger longest on. Maybe not the first thing I'd show a passing stranger, though, especially because it involves fiddling with a filter. Any tips would be greatly appreciated.

    Bortle 4- I just cant get on with the bortle scale, SQM or NELM is what I relate to but so is the appearance of the Milky Way, so we'll use that.

    Can you see the spur that goes into Cepheus from that location, just above Cass?

    Overall I feel that a tight OIII that catches both lines and gives high transmission (high 90%'s) works better in most situations, in particular from rural but not truly dark skies.

    Your 30mm-32mm is a nice spot for the low end of eye illumination and you can benefit from more ie a higher fl eyepiece, a 38mm-42mm would be good and work very well with the tight OIII.

    Can you easily see Pickerings Wisp in your scope/UHC/32mm?

     


  7. 31 minutes ago, domstar said:

    Very true. Had a great night on Thursday looking at the Veil. Amazing but not a great object for a quick look with unadapted eyes. 

    Dominic, which fl eyepiece are you using on the Veil with the VG SW 100mm?  filter? one more how dark is the sky do you figure?

    I ask because there are "tricks" to get better views of things like this.


  8. 45 minutes ago, domstar said:

    I just thought it was funny, especially not being able to find the Andromeda Galaxy. It felt like 'Mum, look at me ride my bike'-crash. It's really true that I had about 10 seconds. I wanted to blow minds but actually, what we do is very subtle apart from the moon Jupiter and Saturn. 

    Wanting to show a fantastic view of something is a nice idea, sometimes this desire can put extra pressure on, but really we (well me) are only observing for ourselves and if someone else likes it great. A neighbors grown children from far away expressed honest desire to see my equipment and outdoor obs, which I showed them. Next year they are invited to come over to look up and they are excited!

    In truth the only jaw dropped on the ground I care about is mine lol! if someone elses does bonus!

    • Like 1

  9. 1 hour ago, Northernlight said:

    Hi Iain,

    Thanks for the feedback. I'm trying to figure out if I need to replace the focuser for imaging or if I can get away with the stock one and save a bit of money as the price sharp creeps up when you add all the extras.

    £819 for scope + £115 for 1/10pv upgrade + £220 for a coma corrector, + £50 for secondary dew heater + £240 for Baader focuser + £35 for focuser base plate + £319 for cats eye collimation kit.

    So the scope suddenly doubles from £819 to over £1600

    My VX10 has a pretty good focuser but fell apart when obs on the ice. I found the parts, loctited them and alls well. The 200mm f3.8's focuser is a complete piece of junk and is barely working now, its a new design with a unique 1.25" adapter.


  10. 1 hour ago, johninderby said:


    Because it uses circles instead of a crosshair it is a lot more accurate. You move the drawtube in or out until one of the circles matches the outside edge of the secondary mirror. Rotate and move the mirror up or down until it is a perfect circle. This also takes care off offset adjustment. They do 1.25” and 2” versions. Takes eye of eye placement as well during setup.

    https://www.teleskop-express.de/shop/product_info.php/info/p5506_TS-Optics-Concenter-2--Collimation-Eyepiece-for-Newtonian-Telescopes.html

    Sounds interesting, I might try one. With the Teletube the end can be extended and the focuser racked so it gives a "circle" edge the same as the sec circle picture sight. This will show the position under the focuser very accurately as well.

    How do you find the accuracy of sec alignment to the primary and vice versa using this tool?

     


  11. 1 hour ago, johninderby said:

    The Telescope Express Concentre is a pricy but simple device for getting your seconday mirror perfectly set up. I had thought my secondary was perfectly set up but found it wasn’t after using the Concentre. Made me realise how imprecise a Cheshire or colimation cap is for setting up the seconday position.
     

    Interstingly found my laser colimator gave much better results after setting up the secondary using the Concentre.

     

    How does the Concentre work?


  12. 2 hours ago, Captain Magenta said:

    Many instructions advise racking the focus-tube (and hence collimation-cap and viewing-hole) out as far as it can go, or even using an extender as I did, to allow the guaranteed-circular far end of the focus-tube and the edge of the secondary to come close together for accurate evaluation of circularity.

    This adjustable sight tube works very well and very accurately. I removed the 24" spider/sec for a fiber batten tweak last night and re collimated. Sec is accurately centered and collimation is not perfect (no AC) but very very close. You can extend the tube into the focuser to get a really fine view of the sec edges. Fast, accurate, simple and expensive.

    image.png.7afd909e194e7ec1af4ecae9ae8b9585.png

    • Like 4

  13. A good newt is hard to beat and I would think that you either have to splash out on an expensive SCT or get a "good" one to compete with the newt.

    2 hours ago, piff said:

    Millimetre for millimetre, is it considered that you get clearer images or greater magnification or both  from a refractor, or from a Schmidt-Cassegrain of equal aperture?

    Which refractor? which SCT? generalizing is not the best option IMHO.

    A top refactor offers such purity to the view.... and will take high mag, at a large price. However a top SCT type scope can deliver stunning views, @dweller25 might (does) have a good opinion.

    Then there is the 200mm f6 newts out there that can make so many high end scope owners cringe under good seeing...

    • Like 2

  14. On 20/10/2019 at 12:36, estwing said:

    John Nichol makes outstanding mirrors below F4...

    Gerry, the bigger the dob the less ep's you use..most of my observing sessions are with the 21 and 8 mm ethos...Mapstar has plenty of nights where the 13 ethos is the only ep he uses in his 22".

    Had a poor sky last night so I got around to fine tuning the 24" and tried different EP's with the Paracorr. The 21E/17E really work with the PC- TV knows what they are doing.

    I can see why you guys only use a small few eyepieces now- whats your thoughts of the Delos in the bigger scopes? I'm thinking of a deep eyepiece or 2 for easy use with the Paracorr.

    My Nikon HW so far wont work with the PC which is too bad, it is a superb eyepiece. The Docter is most likely out too, but I'll try TV's infocus adapter before getting the 13E.


  15. 2 hours ago, Piero said:

    Still, if one spends 3K pounds in eyepieces, 500 pounds in a CC is not a big deal to me, particularly considering that the views through all the eyepieces will improve.

    In my case there were a couple of issues for the wait- cost yes, with a but...I wanted to be re assured that the Paracorr would work very well, its too much money (for me) to buy and have not work.

    Second, my 15" at f4.8 gives such good lunar/planetary views I didn't think it was needed, however I think an improvement will be made with the CC. I'm curious about 2 things- on axis sharpness and threshold objects with the CC.

    Oddly enough I use far less eyepieces with the 24"?:dontknow: some might be on the chopping block, with a Delos or 2 coming (back) in. I just cant wait to try the 21E/Paracorr II on the Swan neb.... the Nikon HW might get chopped, we'll see.

    Down the road I would investigate sub f4 dobs Piero, in the 16"-18" range and the corresponding need for truly engineered mirror cell design. Lockwood is one of the only makers really into this, but a couple of others can do it ie Terry O, not sure about EU. NV will add a different perspective on objects and offer much flexibility to observing.

    Me, I'll slog away with a few pieces of polished glass and a dark sky lol!

    • Like 4

  16. 10 hours ago, Piero said:

    Before this, I want to reduce the currents in the tube and understand the interplay between fan and light shroud.

    In my brief experience with truss dobs it seems to me they have unique likes. At times I leave my shroud pulled back at the top of the mirror box to allow any heat to rise up there. I cool with the fan-pre seacan that is- and then turn it off to observe, I find tiny blurring caused by the fan.

    The white seacan keeps the 15" and 24" within 4 deg F of ambient, which is great and with no early morning dew. When its really cold I keep the shroud all the way on to combat body heat wrecking the views, this can make a big difference as does the stance taken to observe.

    • Thanks 1
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