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rl

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Everything posted by rl

  1. Look on the bright side; TeleVue don't make orthoscopics.....
  2. Minimum glass aficionados swear by them. Good orthos are relatively cheap with respect to the usual suspects in the eyepiece quality league and punch well above their weight in terms of contrast and sharpness. Modern multi-element eyepieces can be as sharp with more field, but at vastly inflated cost. Most visual observers keep a couple in the back of their eyepiece case. Anonymous circle T or circle V are fine, Baader maybe a slight step up. Scratch that itch...try one secondhand and just sell it on if the 45 degree field or short eye relief is an issue. MK1 eyeball can be the limiting factor for more experienced observers like myself (read "old")...exit pupils much below 1mm are fairly useless for me because of floaters.
  3. The secondary on a fast newt always looks slightly offset due to foreshortening of the ellipse; the rays hitting the top end of the secondary have had a couple of inches extra travel up the tube to come in closer to the optical axis. . Some people offset the secondary slightly to compensate but OO scopes don't allow for this as the vanes are fixed length, as is true in most commercial designs.
  4. Close, but the third clip on the primary is outside the field. Secondary might need a tweak followed by the primary. Take it in very small steps.
  5. @pipina E6 was ok to process, but you're right in that a temperature drift could shift the colour balance. I used to do my processing in the bath (not me..the developing tank..). The large volume of water held its temperature relatively well and you had the option of letting a little out and topping up with more hot water as required. It did require some practise and nobody else in a hurry for the bathroom.. I've just looked at the data sheet for the latest incarnation of Ektachrome and its red response looks quite good: https://imaging.kodakalaris.com/sites/default/files/files/products/e4000_ektachrome_100.pdf Still nowhere the QE of a modern sensor but H-alpha can be done... If film and the processing kits were not so expensive I'd have a go myself just for old times' sake. SLR bodies are 10-a-penny in charity shops.
  6. It's the way we all used to start 50 years ago before this new-fangled electronics malarkey took over the universe..... Faster films are not always better; there is an effect called "reciprocity failure" which limits the useful exposure time to 5-10 minutes (guided) but for unguided shots a 3200 speed should be ok. I used to use Tmax 400 (B+W) or Konica 3200 (colour). Ektachrome 100 was great for colour slides and easily push processed if you do your own processing with the E6 kit. Look out for the original edition of "Astrophotography for the Amateur" by Michael Covington on ebay/ amazon. Most camera lenses gave best results (sharpest stars) run at slightly less than maximum aperture. Aahh..the memories!
  7. @ Franklin Yep, I've seen the rings of Saturn through scopes with less aperture than the eyelens of the ES92...
  8. Turd expertly polished! What sort of lap did you use?? Murphy's law in action, I'm afraid. No chance of a supernova in December at new moon while the streetlights are out of action for maintenance.... That is a better result than I got under Bortle 4 skies....
  9. Feel free to rant! Actually light nights are the chance to debug the system one step at a time so that when darkness returns mid-august you will be ready.... You are not alone here! In the early days I often felt like chucking the whole lot in the skip. Eventually I actually did chuck an old EQ5 mount in the skip because my particular example was so unreliable, having had a hard life in the hands of it previous several owners. . Getting a working system generally takes time, patience and a lot of frustration along the way. And when you've worked out how to do it right, the weather intervenes for a month and you go and forget something vital..forgetting stuff is even more annoying than not knowing it in the first place, after you've just ruined an evening's subs over some stupid cockup! The problem is of course that you probably want longer subs with longer focal lengths on fainter targets so the level of perfection required from the kit goes up exponentially, so there is no going back! Might I suggest going out with very low expectations and simply fixing one thing at a time, not spending too long on it.. Getting the guidescope to focus seems like a good start. Can you use one of the plate solving programs to get easier / better polar alignment compared to crouching down peering through the polarscope? Do PHD2 default parameters work ok with your mount? Is the mount balanced correctly (i.e not exactly balanced to as to take out the backlash)?
  10. Yep, beautiful view. Reminds me of why I got into this hobby in the first place..... Nice view of the Petavius rille through the scope as well...
  11. Absolutely par for the course...I think a certain masochistic trait is an essential requirement to do this hobby. Astronomy was a hell of a lot simpler when I started 50 years ago..
  12. Hi.. Visually an 8" is noticeably better but the difference is not massive. A good site counts for more than the extra 2". Since you *know* you are intending to go down the AP route I'd stretch the budget if at all possible, start with the mount and look out for a s/h HEQ5. There is nothing more likely to give you problems than a substandard mount which will frustrate you and end up putting you off. It will take a decent choice of OTA including the ubiquitous ED80 and 150PDS, plus all the trimmings. I sold my 150PDS for £120 a couple of years ago..when cash is really tight s/h is the way to go providing you check that the seller has a good reputation.
  13. Carl I used to work for the HIROS astronomy group at Birmingham University in England. 30 years ago we used to spin cast parabolic epoxy mirrors up to 1 metre in diameter for use a flux collectors in long term spectroscopy projects where it was not possible to get enough telescope time for the amount of data needed. These mirrors were not of optical quality but were very light and quite good enough to focus starlight on to an optical fibre which would connect to the spectrometer. They were used to look for low level pulsations on bright stars..basically sound waves bouncing around the stellar interiors in the same way that earthquakes travel around the earth. The photon signal-to-noise needs to be excellent to do this, and you need a lot of data over a long period of time...often months or years. It's called asteroseismology. Most of their work was done on the sun where s/n is obviously not a problem and you can see sound waves with a 5-minute period in real time, but quite a few PHD students tried the far more difficult stellar stuff. https://www.birmingham.ac.uk/research/activity/physics/astronomy/solar-and-stellar/helioseismology/bison/background.aspx/background The epoxy has to be mixed so as to set over a period of 10 days or more..... the room temperature has to be held constant.... the balance needs to be perfect...you need an air bearing to keep the rotation smooth enough...the spin speed has to be tightly controlled.....you need to keep dust off using an electrostatic screen..there is an art to it!
  14. Welcome Stuart. That's a fine glassware collection for a relative beginner...
  15. @bomberbaz Steve If it's any consolation the Nikons now have pride of place in a good home with a diehard 2" fan, and I managed to sneak them in without "her indoors" noticing. So far no need to explain the extra bits of kit in the astro box! Many thanks. Might even be a clear night tonight...
  16. @jeremys: I'm glad you sold your 34mm Maxvision, that has become my staple widefield finder!
  17. It's been around a long time and maybe underrated a bit compared to newer offerings. I love mine; it covers a lot of bases magnification-wise and is nearly parfocal over the whole adjustment range. Eye relief could be a little bit better; DeLites do have an advantage here (yes, I've got a couple of those as well). To my eyes the contrast holds up with the best of the competition; I have a Vixen 3.4mm which is supposedly better in this regard but to be honest I can't see much difference in terms of contrast or scattered light. It sees more action than the Vixen or any other of my sub-5mm eyepieces just because it is light, works on virtually any scope and takes up so little space. I'm actually thinking of selling the Vixen because it does not really add anything over the TV zoom. I've got the 3.7 and 4.7 ethoses. The views have about the same contrast and obviously much more field, but they are too bulky for small scopes and don't fit in the pocket so easily. Their very expense renders them less useful just because of the extra care taken in handling! The ability to tune the magnification to the seeing is genuinely useful, and it works just fine between the click stop positions. It is expensive for what it is, but it is TV so quel surprise....
  18. What is the biggest Dob you can pick up and move? Will you need a trolley? To be a worthwhile improvement on an 8" you're probably looking at a 12" Dob. I can manage a 14" just about on a regular basis.
  19. You would need something like a Poncet mount for imaging; not sure they are controllable enough for reliable results. Alt-AZ will limit your subs to low seconds. I'm a big Dob fan but they really do visual best. If you're serious about imaging look at the mount first and then see what scope you can fit on the top!
  20. How do the secondary mirrors compare? The 300PDS is optimized for photography. Is this ever going to be of interest? If so you will need a big equatorial mount, is the GOTO mount equatorial?. Is the GOTO actually useful visually or do you prefer to star-hop? If you are visual only I'd take the one with the smallest obstruction. And the simplest mount...
  21. Excellent result. Assuming an exposure can be made and read out in 10 seconds, that's over 1000 subs to stack and align over the 3 hours!
  22. I have owned several small apo doublet / triplet scopes in the 60mm - 90mm range and my example has the best optics for the aperture of any of them. Quibbles; The OTA is not the lightest and some people complained of slightly wobbly focusers (early versions only?). The tensions are adjustable, and I haven't hears of this for a while now. It's been around a long time in various incarnations. WO have a habit of changing the model with the weather (it's called continuous improvement..) so the fact that the GT81 has lasted this long with the optics unchanged probably says something about the commercial benefits of keeping it in production. I paid £450 for my MK1 secondhand ant it's a keeper.
  23. Over the past 30 years of using guiding eyepieces equiped with these illuminators I've found them to fail fairly regularly; I've got 2 broken ones and a third that is intermittent...it only works if the two halves are unscrewed a fraction of a turn. They might almost be considered a disposable item. I've seen several guiding eyepieces for sale on ABS "illuminator missing" which probably tells you all you need to know on build quality.
  24. Field curvature often gets forgotten as a source of edge distortion. A ST120 with an ethos 21 sounds like the perfect combo for widefield views, but FC really takes the edge off the experience. I have 2 scopes that are designed primarily as astrographs; one is a TS65Q and the other is a Pentax SDHF75. Both have a flat focal plane built-in for the camera. When teamed up with an eyepiece also having a flat focal plane the view across the whole field is just insanely sharp without any need to refocus. Optically they are the perfect match for Delite and the smaller Ethoses . The tragedy is that it only works reliably for 1.25" format eyepieces with a 1.25" diagonal and reducer. Using a 2" diagonal requires too much in-travel for many fine eyepieces......why, oh why can't they make an astrograph that will handle both? A 13mm ethos will focus but the 21mm won't... Similarly on Newts, the better coma correctors also flatten the field as well as sorting the coma, getting the best out of flat-plane eyepieces.
  25. If you don't need the eye relief I'd look at a S/H Nagler zoom 3-6mm which might see a lot more use. I bought one off ABS and have not regretted it; they generally go for about £270 used. But the Delites do really live up to their name....
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