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Everything posted by John
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Comet C/2020 F3 (NEOWISE)
John replied to verreli's topic in Observing - Widefield, Special Events and Comets
Rather frustrating amounts of clouds about in the wrong places tonight. Just a quick comet pic using the hedge to block a streetlight: -
Beautiful disintegrating meteor
John replied to Victor Boesen's topic in Observing - Widefield, Special Events and Comets
I have seen a meteor break up a few times but I've never heard any sound from one. Not yet anyway. -
I seem to recall that they perform about as well as the Meade 4000's and 3000's but have a flashier body. They pushed the field of view out to 60 degrees but the design didn't really handle that well so the edge correction is lacking. If your scope is F/8 or slower they should be OK. The HD60's were a different optical design and handled the 60 degree field somewhat better.
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They are Series 5000 plossls. I have owned a couple of them. They are fairly average performers I thought. The Meade HD60's (below) are much better:
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Next upgrade choice
John replied to AstroNebulee's topic in Getting Started Equipment Help and Advice
Something very wrong there and not with the eyepieces I think. A 130mm scope will show good planetary details. I could see Cassini's Division in Saturns rings and a number of Jupiters cloud bands with a 90mm mak-cassegrain a couple of nights back. Not an expensive eyepiece either. You are further south than I am by 150 miles. Jupiter and Saturn will be a bit higher in the sky than they are here. -
Next upgrade choice
John replied to AstroNebulee's topic in Getting Started Equipment Help and Advice
One cheap way to get more detail on the moon and planets is to observe them as often as possible and for extended periods. Its surprising how the eye starts to get "trained" and picking out the more subtle details becomes a little easier each time you observe a particular object. An eyepiece upgrade can make a slight difference but gaining observing experience and skill somewhat more I reckon. -
If it's off, it's not far off at all.
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When is a Televue 55mm Plossl no longer a Plossl?
John replied to alanjgreen's topic in Discussions - Eyepieces
Interesting development. This is TV responding to the needs of the evolving EEVA market presumably ? "Extended Plossl" perhaps ? -
I used the 31 more before I got the Ethos 21 which shows almost as much sky but at a higher magnification. The Nagler 31 is still a favourite for extended DSO's such as the Veil Nebula, N A Nebula etc. With my Vixen 102 F/6.5 ED refractor the big Nagler will show a 3.8 true field of view and the whole of the Veil Nebula complex
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I occasionally use a 40mm 70 degrees eyepiece with my F/5.3 12 inch dob. I don't recall seeing the shadow of the secondary but the skies have been dark when I've done this so I might not have noticed it. It is not the most effective eyepiece for DSO's in that scope though. The 31mm Nagler and 21mm Ethos are much preferred usually. And this is my excuse for not getting a 41mm Panoptic
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There are some big variations. Zeta Herculis, for example, has an orbital period of a touch less than 35 years. I have a sketches of it done in 2016 and 2020 and the change in position angle between the two is very obvious.
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Comet C/2020 F3 (NEOWISE)
John replied to verreli's topic in Observing - Widefield, Special Events and Comets
A Pentax K-r DSLR. It's not a camera that is commonly used for astro photography - I bought it so that I could use my old Pentax K fit lenses etc from my old 35mm days. -
Comet C/2020 F3 (NEOWISE)
John replied to verreli's topic in Observing - Widefield, Special Events and Comets
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Comet C/2020 F3 (NEOWISE)
John replied to verreli's topic in Observing - Widefield, Special Events and Comets
Surprise break in the clouds here allowed some quick shots and a view with 8x56 binoculars. Still looking lovely ! -
This one caught a few people out in April 2017
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I ought to shed some stuff really ...... then I can get some more !
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Too true !
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Another interesting challenge is that it is possible to discern the identities of the moons by their apparent disk sizes. Although very tiny, they do show some variation if you focus sharply and the largest, Ganymede, has an apparent diameter noticeably larger than the others if you look closely.
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Interesting tables. Tube lengths come into the equation having as much or more impact than weight as they get longer.
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Mobile phone images of Jupiter invariably over-expose the planet so the features that can be seen quite well with the eye at the eyepiece vanish in the glare. With a 90mm mak-cassegrain at around 120x a few nights back I could see 4 cloud belts and some festoons coming off the northern equatorial belt and into the pale equatorial zone. A couple of nights earlier, with my ED120 refractor I could see the Great Red Spot sitting in the center of the disk embedded in the South Equatorial Belt. Here is a nice image of Jupiter (not mine) showing the various features to look out for:
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On this topic, I find it important to position the eye cup correctly to ensure the you get the best from an eyepiece. Some eyepieces have twist up and down eye cups or top sections and, if you do not wear glasses when observing, generally the upper positions work the best. If you do wear glasses when observing, generally the lower eye cup position works the best. I use the word "generally" here because we are not all the same of course with regard to our eyes, face shape, depth of eye socket etc, etc. I like to use the eye cup as my guide that my eye is in the right place so my preference is to gently nestle my eye brow / eye socket against it. I have come across a few eyepieces where the eye relief is so long that the correct eye position involves "hovering" the head above the eyepiece top and this I find less than relaxing for lengthy periods making maintaining the correct eye position more difficult than it should be. These are my personal findings and preferences however. Yours may well be different !
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Some Tele Vue eyepieces include a small circular mask which is placed immediately above the eye lens to help find the exit pupil of the eyepiece for those who have difficulty with this. It is called a pupil guide. As the focal length of the eyepiece gets shorter, finding and holding the exit pupil (the small circular spot of light that exits an eyepiece) becomes more challenging because the exit pupil reduces in diameter. Holding the head still, so that the eye is both central and at the right distance from the eye lens, becomes even more important. When doing outreach I tend to use longer focal length eyepieces for this reason. People who have not used a scope can find positioning the eye tricky with a short focal length eyepiece.