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jetstream

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Everything posted by jetstream

  1. I would seriously consider one of these- f 6 is a great place to be and the 200mm should be easier to transport.
  2. Yes, for sure Steve. I tried the Baader Neo from my former town location, about mag 20- it didn't help...
  3. Sadly enough any filter cannot increase contrast on galaxies, the bright sky reduces one of the 2 main components of actual contrast. Observing from extremely light polluted skies are the realm of NV IMHO, their primary use- again IMHO.
  4. Great report! I have push to DSC on my dobs and love it, very accurate if I do my part.
  5. Fun is the name of the game! Yes the obstruction does that and strangely enough increases contrast in the higher frequencies and keeps the frequency range intact for the aperture. I would guess, if the mirrors are 1/4 wave total that this scope would give the Telementor a run on the moon detail wise. I would definitely flock it, and paint the sec edge and holder with flat black paint with the smoke in it. The drawtube and area would also get attention. It would be nice to check reflectance before getting re coated- don't know how maybe someone here does? Roland Christen tested mass SCT's before the "Starbright" coatings era and some of those were extremely low in light transmission, as were some eyepieces. The SCT had the 88%x2 x mirrors and about the same for the corrector...about 68% transmission and without counting the CO reduction in aperture. With high reflectance mirrors, all flocked up etc I would be surprised if the TAL didn't offer similar DSO views. To its + side it is already APO chromatic. With the most modern equipment available and from an optician that is VG -Terry O - my 97% nominal mirrors are about 93% true reflectance avg, which is top tier. There just might be a bit of hocus pocus with the mass produced reflectance numbers...but I think a lot are 90% or so.
  6. I would think that a couple of things might be at play here- the possibility of stray light reducing contrast- the u tube video shows much reflections with a light shone down the tube. Another thing is mirror reflectivity- even the best are quoted as "nominal" and also vary in reflectance across its surface. A typical 96% high quality mirror will produce in the low 90's -92%-93% ( a top coater told me this). So, if the TAL has 88% reflectance X2 for the secondary were down to 77% , add the eyepiece at 97% and were at about 75% system throughput. This does not take into account the reduction in aperture from the secondary. The Zeiss will have top coatings and polish around 97% so were comparing a top 63mm (60mm effective with EP) to a scope operating around <48mm effective that has stray light issues (possibly). The obstruction will make the TAL easier to split stars for sure IMHO- airy disk stuff. The CO might be a goodly number on this scope. Glad you had fun Stu!
  7. How big do you figure it is? obstruction can do weird things IMHO
  8. Great report Stu! It sounds like the TAL has well figured lenses and the Zeiss has excellent coatings and a fine polish that allows better views of the galaxies.
  9. AFOV... I find that 100 deg eyepieces give me better results on large diffuse nebula that smaller AFOV eyepieces, regardless of TFOV. Some say that the larger, full engagement of the eye, with no visible field stop can provide better views on certain things and in my experience this holds true. Please note I usually observe these objects at an exit pupil smaller than my 7mmish pupil dilation. Dilation measure by the "drill bit" method. There is a sweet spot mag wise for every object in each telescope IMHO. It might be possible that photon concentration as dictated by the exit pupil (field stop) plays a role. I get better views around 4.5mm-5.5mm that at say 6.25mm, still below the 7mm dilation. Ive been testing this for years.
  10. what are you going to look at primarily? the article said the contrast booster removes most all CA but reduces transmission and adds a yellow cast. It would be good for planets IMHO but my natural no experience guess would be to use the semi APO
  11. How many teflon glides are in this focuser? from me: The adjustment is now done and the Tak focuser is now buttery smooth. I loosened the 3 glide set screws until I had backlash and drawtube side play. The set screws were then slowly snugged up until both the backlash and side play were "just" gone. For me there is no need (yet anyway) to delve into the bottom plate area as there is a nice relationship between the glides and the rack & pinion backlash. As a test a hvy Baader/Zeiss prism diag and 30mm Es 82 were put vertical in the scope- no problem holding it at all. Tonight we'll see how the Binotron 27's make out."
  12. Mine too- the TSA 120 adjusted up nicely, smooth as butter and no play.
  13. M13 is a bright object and might show as a smallish fuzzy ball at low power in your 100mm and upping the mag will resolve more stars. The propeller feature can be tough and personally find that there can be a smallish sweet spot mag wise. Highly recommend playing with magnification on this one.
  14. Yes, thank you Robin. Its great to hear this from you- most say aperture cannot give brighter images etc visually- actually most start off believing it until "corrected" by others. Excellent info about the photons and how the image is formed, I did not realize the image is built up this way in our brain. The 24" gives so much more detail than my 15" it really puzzled me until now. Both the scope builder and optician said it would surprise me. I also have a 200mm f3.8 for comparison. Now for the exit pupil... I know there is a sweet spot for nebula, my favourite objects with and without filters. So if I maintain a "proper" exit pupil range of say 4.5mm to 5.5mm could it be true then that the smaller exit pupil has more photons available for my eye? ie packing more in the disk? Edit: just thought about it...the photon level must be dictated by primary mirror aperture so the same number must pass through the eyepiece(s). The smaller exit pupil must have more concentrated photon levels?
  15. Congrats! In the image of M13 do you see the "propeller"? another great feature in this fantastic spray of stars.
  16. Living around animals means interactions with them, we don't mind it here and in fact like it. For the most part the predators have their traditional prey and its only the odd ones that become a problem. About 50 miles away in farmland very few cattle are taken by wolves, again their main prey is deer (and moose by me). We have Lynx as well- they make wide loops and focus on where large groups of animals (unhealthy) have exploded and they bring things back under control. We had a wild rabbit problem 4 years ago, they were everywhere- until a Lynx set up shop for a couple of weeks. One of my very favorite animals is the Owl- they are here now and at night I'll sit on the deck listening to them hoot back and forth as I watch the stars. Hopefully some wildlife can be introduced over there Iain, the farmers could make it work and protect their livestock.
  17. Me too... I find the best approach is keeping an absolutely open mind, placing my own thoughts in the archives and building the archives up more. The end result is usually pretty good and thanks to those that help.
  18. Thank you sir! I have been wanting (needing) a confirmation of what Ive noticed and what some other various and serious astronomers have told me. Packing more light into the exit pupil or however we want to describe it. This idea seems to send some into fits and they always refer to mag at exit pupil as the only factors. I have to say that fast f ratios and large apertures under dark skies give absolutely remarkable views. I cannot believe what the 24" shows, maybe around this aperture crosses the line or something light wise, view wise, eye brain wise etc etc. I truly appreciate you helping me along again Andrew, @vlaiv too. I hope you guys continue on in the thread- I might be a few posts back trying to absorb but I'll be here.
  19. Sounds good and I hold this view but- do you think its possible that the larger aperture can give "brighter" images due to the aperture itself? Bartels believes in throughput or "entendue". More waves and resulting photons or whatever? Sorry if this is a redundant question. In my scope jumps I went for 1 stellar magnitude increase- I had to use something as a gauge- but my 24" f4.1 seems to blow the doors off the 15" in unexpected ways, M1's detail for example or the Veils. Is this all due to increased magnification at the same(ish) exit pupils? I never thought there would be such a difference Andrew. Btw, back to the brain filling in info- an optics acquaintance said there no way I can see "real" red or blue in M42- that it is an illusion from exposure to the bright green I do see and that the brain fills in the other colours some how. Oddly enough where I see red or blue is in the right places from images I've seen. No clue but the colours are there for me now but were not at first.
  20. I can say this John- any twig snap, crack or unusual sound has my attention. Just before ice out a couple weeks ago I woke up to the sound of wolves screaming...sounded right under my window. Turns out they chased the deer through here and killed it 500 yds away. I found the remains the next day on the sled. Wolves howl but they also scream...its horrific. One timber wolf crossed my path on the road walking last fall thankfully he was hot on a track and only gave me a brief look-at 25yds or so. They are huge. I do love it here, my home it is.
  21. Well it does work sometimes but there are many many cases where it doesn't...there is zero chance I'd be the tester on a grizzly. I truly hope I don't ever have to try mine out either!
  22. Yes, I have bear spray- works if their not mad- doesn't work on grizzlys, thankfully none of those here. We won't talk about what that bear was doing as it was standing over the woman... but there is a reason they wanted to find the others. Bears can pattern themselves on food by observing other bears ^^.. and they have food location memories. They can remember single trees or houses or anything else and can be passed down by generation, hence repeated visits in certain locations. Here its my dads berry tree- I can't bring myself to cut it down.
  23. Thanks so much Vlaiv, Andrew and yourself are helping immensely and it is much appreciated. I will go over this info repeatedly. To fastrack to my aperture question which you and @andrew s can answer- will an aperture of say 8" contain the same information an aperture of say 24"? I might think it would if the photon level in the smaller is enough to form the same image? Are more photons or light packets in the larger aperture? can and will this be seen by the eye? Many believe in "light grasp", I'm undecided as traditionally most serious observers think in terms of magnification at a certain exit pupil level, which aperture is a component of. My 24" might be changing my mind a bit...
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