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John

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About John

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  • Birthday 21/02/1960

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    North Somerset, United Kingdom
  1. Just observed SN2018pv (NGC3941)

    Well done Alan. I got it tonight with my 12" dob at 318x. Rather tough to split the SN from the galactic core under tonights conditions. The split "came and went" as you say. Not a great galaxy night but you have to take the chance when it's clear.
  2. Which Tak

    4 would be a large proportion of the whole UK allocation I think. Australia only got 4 of the 1st run of 100 I understand.
  3. Which Tak

    I realise that you were jesting but was that necessary really Mike ? When this report was posted you jumped straight in with excuses as to why the why slight differences between the scopes were detected. I've noticed that the author has not qualified his report, which given his reputation I'm sure he would want to do ? http://scopeviews.co.uk/TakFC100s.htm As I see it the F/9 is simply a slower variant of the F/7.4 aimed perhaps at a slight different audience - I'd have been very happy to own either
  4. Which Tak

    I have the DL.
  5. If you get over 8,000 feet here in the UK you are flying 3,600 feet over the highest mountain top (Ben Nevis in Scotland) ! . My back yard is just 300 ft up and the seeing is usually a little better here than when I've observed more or less at sea level. On the topic of seeing detail on Jupiter, I agree that the bands and other features are more distinct when the planet is viewed against a twilight sky. As the sky gets darker (I most often observe in the evenings when the planet is visible then) it can get harder to pick out the more subtle details. With my 120mm refractor I have managed to pull out some quite nice Jovian detail at times. This (rather basic) sketch was done using that scope a few years back:
  6. I ought to add that I'm not over-critical on these chinese 6" F/8's. For what I paid for them (all were under £200 on the used market) they provide a big refractor / unobstructed aperture experience and I generally enjoyed using them (I did own 4 of the things, but not all at the same time !). A 6" ED doublet is going to cost around 9x as much on the used market I'd have thought. Skywatcher are due to launch a 150mm ED doublet later this year so it will be interesting to see what that costs.
  7. How would you like it quantified ? I've owned 3 of them. The CA seemed about the same in all 3. Quite noticable around the moon, brighter planets and stars brighter than around mag 2/3. I tried to measure it around the moons limb (it varies with the magnification used, increasing as more mag is applied). I seem to remember that the depth of the CA halo around the limb was similar to the apparent diameter of the crater Copernicus so something around 60 arc seconds at perhaps 150x I also owned a Meade AR6 which is a 152mm F/7.9 and that showed a similar amount. It's a difficult thing to quantify through because some people seem to notice it more than others. All the above scopes had a degree of SA (spherical aberration) as well which had some impact on their performance at higher magnifications. There is probably some example to example variation on both CA and SA though so others may have had better experiences ? Using a Chromacor to correct the bulk of the CA and SA was very educational for me with these scopes and why I've ended up with ED doublets now.
  8. I have a 55mm plossl which is similar to the one described above. It's an ex military optic that has been adapted to fit a 1.25" barrel. It works but the AFoV is really narrow - probably around 30-35 degrees. There is no field stop as such and the field edges are defined by the inside of the 1.25" barrel. It's not a lot of use to be honest - I bought it a long time ago when I didn't know much about eyepieces
  9. Which Tak

    Wonder how many DL's are left to purchase from the 2nd run ? It was always going to have more limited appeal than the faster versions though so Tak were sensible to limit the production. Apparently faster apos outsell slower ones by quite a ratio - by as much as 10:1 in some cases according to Markus Ludes of APM Telescopes. The TMB / LZOS 130 is the example I'm thinking of. There is an F/6 and the F/9.2 version that I have. They have made 105 of the F/9.2's since production started in 2006. 9 more will be made. All three Tak FC-100 models are wonderful scopes though, IMHO I went for the F/9 because I already had the very nice Vixen ED102SS which is F/6.5. I'm sure you will really like your F/7.4 Shaun
  10. Interesting, very interesting I've got an old Pentax SMC F/1.7 50mm lens somewhere - maybe worth an experiment with my longer FL refractors
  11. Focal ratio of an eye piece?

    Many eyepieces have lenses of varying diameters used in them. Which lens is used to calculate the focal ratio or is it the field stop diameter ? Edit: Ooops ! - just noticed that this Q was asked in the opening post of the thread
  12. Finding M78

    What is your gear ? M78 is visible in small scopes as a small faint patch of light with 2 stars seemingly embedded in it. It's not particularly spectacular but it's worth seeking out on a dark night. Here is a link to a good finder chart: https://freestarcharts.com/messier-78 I use the path indicated by the red arrows on the image below to find it with a low power eyepiece in the scope:
  13. Very interesting post Jay Jupiter, to me, definately shows more detail and contrast against a twilight sky than against a really black one.
  14. Lazy Susan...no thanks.

    This one was built by an SGL member who knew what he was doing. It works superbly
  15. I think a 6" achromat needs to be f/15 at least to reduce the CA to levels that are not really visible in the eyepiece. My Istar 6" F/12 had a very nice objective (ie: nice, smooth figure) but the CA was quite obvious around the brightest targets I thought. The 6" F/8 achromats I've owned showed more, until the Chromacor was installed and then it was controlled to ED doublet levels. Sir Patrick Moore's 5" Cooke refractor is one of my very favourite telescopes It was part of the motivation behind my decision to buy the 5.1" TMB / LZOS F/9.2 - the latter being a touch easier on the mount than an F/12 but having roughly similar lines and proportions perhaps ?:
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