Forum Replies Created
-
Posts
-
Posted by David Mottershead at 19:47 on 2010 Sep 06
HelloIt’s a while since I owned a Newtonian, but from when I did, if it really is only very slight, and I mean veryslight, then I would suggest its nothing to worry about. How do the Airy rings appear on a star test? Are targets such as Jupiter clear, sharp and crisp through a range of magnifications? Again, if all looks good, then I wouldn’t worry.
Posted by David Mottershead at 19:42 on 2010 Sep 06
Another fine set of images Andrea. Jupiter is looking good at the moment (ok, not actually as I write this as it’s blowing a gale and raining outside)and hopefully we will have clear skies for its opposition on the 21 of this month – plus Uranus less a degree away on the same night!
Posted by Gary Poyner at 10:45 on 2010 Sep 03
Hi Paul,OK. Lets try again (my last attempt was slightly too big).Here is a 2 degree field from GUIDE 8. The circle in the centeris 1 degree. The limiting magnitude is only 11, as it would lookvery crowded at this size if it went any fainter. Is your star here?
Cheers,GaryPosted by Paul A Brierley at 20:06 on 2010 Sep 02
Thank you Gary,I’m sorry for missing vital information. The eyepiece is a 24mm Panoptic with a 68 deg FOV; The true field of view is 1.36deg. Magnification x50 and the telescope focal length is 1200mm f4.8
Posted by Gary Poyner at 19:36 on 2010 Sep 02
There are a number of very red stars in that field. You didn’t sayhow large your FOV with that eyepiece is, but this star isa candidate TYC 3168 1108 Spec. M0 and mag 8.47 It’s 12.5 arc minutesdue south of 61 Cyg. I’ve attached a one degree field (N to bottom, Eto right) with 61 Cyg centered (Guide 8).Gary
Posted by Paul A Brierley at 17:39 on 2010 Sep 02
Hi Callum,The star was in the same field as 61 Cyg and was visible above and to the right of the companion star to 61 Cygni. I can’t say how far it was unfortunately.I’m off tomorrow on a week-end field trip to Harris House in the Yorkshire Dales with members from Macclesfield AS.I will look again if it’s clear tomorrow evening and see if there is somebody there who can identify this mastery object. Or see whether the star shows any variability.On reflection, I probably saw a red giant; but It would be nice to know if it has a number.
Posted by Callum Potter at 12:29 on 2010 Sep 02
Hello Paul,not sure i can help really… How far was this red star from 61 Cyg ? The variable you mention is about 2.5 degrees away, is that about right ?I did a quick review of ‘bright’ carbon stars in Cygnus, but none come very close to 61 Cyg.Also, V1334 Cyg is a fast period cepheid (3 days), and reported as spectral type F1, so should not be especially red. So, sounds like a bit of a mystery…Regards, Callum
Posted by Graham Relf at 08:36 on 2010 Aug 28
PS: That link doesn’t seem to work. But the URL is correct – just paste into browser.
Posted by Marlyn Smith at 11:51 on 2010 Aug 24
Image by Sheri Lynn Karl, Aberdeen showing the sun in H-alpha 2010 August 20th at 1637 UT.Posted by Marlyn Smith at 08:49 on 2010 Aug 19
AR1093 and AR1099 imaged by Andy Devey in CaK on August 14th 2010 at 15.13.47 UT. Both these groups have now rotated off the earth facing side of the disk and are thought to be responsible for a flare and CME on August 18th on the far side of the solar disk.Posted by David Arditti at 22:45 on 2010 Aug 17
I like that. Nice observatory with an agreeable rough-hewn character. Does that till exist?
Posted by Robin Vann at 23:41 on 2010 Aug 16
I am interested in taking part in this, it seems more worthwhile than the old SETI project which worked along similar lines.Robin VannWarwickshire
Posted by Ian Papworth at 21:44 on 2010 Aug 16
What a name from the past, my first telescope was a 6" Newtonian made by Rob Miller in 1981, in fact I still have it as well as my 6" Celestron Nexstar 6 SE.Found a couple of photos of it that I have just scanned, what a wonderful telescope it was and still is.
Posted by Robin Vann at 20:07 on 2010 Aug 13
Thanks David, I shall go ahead with a #80A from one of those.The only reason I’m using IR cut is that the Baader Neodymium Moon & Skyglow has IR cut. I find this filter very good for Moon glow, but also for helping eliminate sodium light pollution (which I have to the west, from Birmingham, which is about 25 miles away); the filter pretty much rejects 589-590nm. It is actually very effective. It also seems to darken the reddish areas on Jupiter, though I hope a #80A will be more effective in this regard.
Posted by David Arditti at 13:50 on 2010 Aug 13
No to gelatin sheets – thing of the past. As to the normal, glass 1.25 inch screw-in filters for visual use, all the major manufacturers seen to make pretty much equal quality. Celestron, Orion (US), Meade, Baader, all very similar in my opinion. For visual use you don’t need IR cut, it’s cameras that are sensitive to IR, not the eye.
Posted by Robin Vann at 00:47 on 2010 Aug 12
Thank you David, that’s reassuring.I’ve also been checking up on the Dawes’ limit. My book (a lunar observing guide) gives it as R = 120 / A where A is aperture in mm and R is in arcseconds. This would appear to give me a Dawes limit of 0.8 arcseconds with my 150mm aperture, assuming seeing being good enough; and for your 5", 0.96 arcseconds, which would also be sufficient to discern them as discs, seeing allowing.I would be interested in your experiments in this regard, and to know what formula you are using for Dawes’ limit.Robin
Posted by David Arditti at 14:53 on 2010 Aug 11
I think your initial assertion, Robin, that you could see the moons as discs was almost certain correct. I would expect them to be resolved at 280x in a 150mm scope. I was looking last night (morning of the 11th) as well, with a 14" SCT and a 5" SCT with binoviewers. Obviously I could see far more detail in the 14", but the view through the 5" was interesting as well. I did not think to look to see if I could resolve the moons with the 5", but I will see next time. I suspect the answer would be yes, and even with a smaller aperture under good conditions. One thing I have learned (from imaging) is that Dawes’ Limit, developed for resolving double stars, does not apply to solid objects like moons and planetary detail. You can often resolve them below Dawes’ Limit. I took some images with the 14" (not yet processed).
Posted by Robin Vann at 02:56 on 2010 Aug 11
I suspect my assertion that I could see Ganymede and Callisto as tiny discs was not correct. They do look like tiny discs at 280x but I am thinking now that this is an optical issue or lack of experience; seeing 1 arcsecond objects as discs seems pretty unlikely at this magnification.I have now dropped the magnification to 150x where I feel the contrast is better; I am still using the Neodymium + IR cut, as this seems to ‘bring up’ the reddish details. I shall now detail the reddish areas I am identifying. Obviously they are seperated by the appropriate zones.I am seeing the NEB strongly and, somewhat less strongly, the SPR, which seems to occupy more latitude than it should: I think I’m seeing the SPR and one or more of the STB as a whole, without seeing anything of an STZ.There is also a glimpse of the NTB showing during moments of best seeing and very occasionally, a hint of the NNTB.Telescope: Skywatcher 150mm f/8Eyepiece: Baader Hyperion 8mmFilter: Baader Neodymium + IR Cut (Moon and Skyglow): obviously there is no moon troubling me, but the filter seems to be enhancing the reddish areas I’m discussing.I still can’t wait for my Orion (UK) SPX200 f/6 to arrive.Robin VannWarwickshire
Another image of AR1093 by Rogerio Marcon in white light 20100808
AR1095 in H-alpha 20100808 imaged by Rogerio Marcon