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About timwetherell

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    Star Forming

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  1. Yeah, I had a clever idea to store some smaller eyepieces in the pier for my scope in my observatory. But in the English climate they were getting a hammering. Not so much from fungus but from a daily dew cycle "gluing" muck to the lenses. Fortunately they cleaned up perfectly but I don't store them in the obsy anymore. As for ventilation, I have an air gap round the rotating roof with a flange that keeps the rain out perfectly. However in our recent blizzards that fine powdery snow blew right under it and I ended up with 1/2" of snow on the observatory floor!
  2. cement mix pier base?

    I used a 6" auger to drill 1m deep piles into clay which seems to have done a god job. The polar alignment hasn't drifted at all in two years. Reading Miguel's post above, If I was doing it again i'd probably protect the ends of the rebar in some way rather than just poking them into the clay!
  3. I had a chance to compare a 6" f8 Celestron achromat against a TEC 140 once, and at low powers with a 31 Nagler it was very similar. So in a way yes, if you're looking at big dim things in wide fields such as M31, to my eyes it was 95% of the performance for 10% of the cost. At higher magnifications the difference was more obvious though, stars not just quite such tight pinpoints in the achromat and chromatic aberration around the brighter ones. Small deep sky objects were still pretty good in the achromat, but didn't just quite have the edge of the apo. Likewise, Jupiter was quite well resolved in the achromat but again, there's the purple halo which does detract a bit. The achromat was still a pretty good telescope especially considering it only cost about £300! If you happened to have a couple of grand sitting in your pocket a 6" apo would definitely be noticeably better as an all rounder, but for many people there are other priorities like feeding your family! In which case the achromat would still give a lot of enjoyment
  4. Evostar 72ED early impressions

    LOL - love it! But of course now they'll say "WOW it was so much brighter in the big dob" Enjoy the new scope - ED refractors do give a lovely view of double stars!
  5. Yes Sirius B is a very challenging target in the UK with Sirius so low in the sky! I finally managed it visually a couple of nights ago with my 7" refractor but I've tried many times before to no avail. It all comes down to seeing. In moments of very steady air it's right there and relatively obvious but most of the time it's lost in a sea of scattered and dispersed light from Sirius. For some reason the atmospheric dispersion and turbulence tend to smear the light into a flame or fan shape like a peacock tail, which would be very pretty if it's wasn't masking what you were looking at!
  6. All of the above is absolutely true, but remember that the human eye is very non-linear in its perception of brightness. My own general rule of thumb is that you have to double the apperture to get a sense of "Oh wow, that's much better". Going from 60 to 150 would definitely qualify for the "oh wow"
  7. With my 1250mm fl scope about 2" or 50mm - pretty much the physical length of the ADC
  8. Absolutely! On an excellent night with jupiter or Mars near zenith I think a dedicated "planetary" eyepiece perhaps has a slight advantage over something like a skywatcher plossl. But with planets 15 degrees above the horizon dispersion and seeing effects will be 10,000x more significant than eyepiece differences. I think once upon a time before computer ray tracing, ED glass and multicoatings something like a monocentric would have been spectacularly better than say a Huygens eyepiece on planets. But today I don't think there's nearly so much difference especially since generic plossls are often really quite well made.
  9. I'm finding it so most days. I guess the thing with low elevation is that it also comes with more pronounced seeing related problems too. On some days when the seeing is so bad one is looking through a shimmering river of air then it's seeing that contributes most to image degradation rather than dispersion so the effect of the ADC is less noticeable. But when the seeing is good, it's very, very much better with the ADC. Prior to owning one, I thought dispersion was just adding a coloured halo to the top and bottom of the planet. But thinking about it further, it's actually smearing the RGB right across the disc, so it's like looking through a photoshop motion blur filter. I'm definitely an enthusiastic convert to these things - especially for £130 which is not peanuts, but it's not crazy money in amateur astronomy terms either
  10. My preference is alcohol (ethanol such as surgical spirit) and unperfumed facial tissue using a new piece for each wipe. To finish off I breathe on the surface and wipe off the fog with a new tissue. This has worked very well for me
  11. Micro-observatory build plan

    I park my refractor horizontally when not in use because it keeps the lens out of the apex of the dome where it tends to get hot on a sunny day but I don't know that's really necessary? Probably would be just fine up there. Before I built my obsy, I made a little model of my scope and observatory in cardboard first to see how the scope would work inside and the general logistics would be. That helped a lot with the design.
  12. part 2 the obsy base/shed and pier

    I don't think the telescope's gonna wobble much given that concrete monolith it's going on
  13. Mine's a ZWO brand that I got from First Light Optics and I'm 100% happy with it and their service. The disadvantage of the cheaper designs (like ZWO) is that the image shifts a bit as you adjust the prisms but that's something I can live with given the very reasonable price. The total range of motion is only about 20 minutes of arc so it's not really an issue. And of course once adjusted for a given elevation, it stays very much the same from night to night. Now I just pop it in each morning observing jupiter - Other than rotating the whole thing to minimise the dispersion, no other messing about is usually required. I did this sketch this morning with my 7" refractor (Jupiter on the meridian and about 20° elevation) LHS with the ADC - beautiful view of the red spot RHS without the ADC - can just about make out the equatorial bands. Of course it won't correct for the worse seeing associated with low elevation but I'd say it makes more difference than just about any other eyepiecey/filtery thing I've ever bought!
  14. Actually I've been using a relatively inexpensive ADC (cost me about £130) for a few months now and I find it a game changer! It's true, one can use filters but unless it's an interference filter with a very narrow bandpass, one will only be eliminating about 2/3 of the dispersion (which is still pretty good for the £5 price tag I'll grant you!). I'm finding with the planets so low at the moment, having the ADC is the difference between a blurry mush and a half decent view.
  15. A new home-built 2,2 m Dome

    Thanks for an interesting read, your obsy's looking great! Well planned and executed project. Interesting to see the efforts you went to making sure the base ring for the dome was actually circular and level - I had much the same struggle building mine