-
Posts
36,419 -
Joined
-
Last visited
-
Days Won
191
Content Type
Profiles
Forums
Gallery
Events
Blogs
Everything posted by michael.h.f.wilkinson
-
The TV Plössl 20mm is no doubt one of the best Plössls you can find, but eye relief alone would make me go for the SLV. I have three of these (5, 9, and 15mm in my travel and outreach set) and their performance is superb. They basically give the same optical quality across their 50° aFOV as the legendary Pentax XWs give across their 70° aFOV. I have several XWs so have been able to verify this. It's almost like having orthos with good eye relief.
-
Lovely image of one of my favourite galaxies
-
Help with Saxon telescope.
michael.h.f.wilkinson replied to Williamc09's topic in Getting Started Equipment Help and Advice
Indeed a 25mm or even 32 mm would work much better than the 10 mm you have on deep sky objects in general. The wider field makes finding things easier too -
How many telescopes do you own?
michael.h.f.wilkinson replied to Grump Martian's topic in The Astro Lounge
Currently I have the following OTAs Celestron C8 Baader/Celestron 8" Tri-Band SCT Meade SN-6 6" F/5 Schmidt-Newton APM 80 mm F/6 APO triplet Coronado SolarMax II 60 Skywatcher ST80 (guide scope) generic 70mm F/5 achromat (giant finder) 60 mm guide scope If we count binoculars as telescopes that would add Helios LightQuest 16x80 mm Zeiss Victory 10x42 mm Lunt 8x32mm SUNoculars Zeiss Victory Pocket 8x25 mm These scopes may be mounted on the following gear: Vixen Great Polaris Vixen GP-DX iOptron HEM-15 ZWO AM-5 SkyWatcher EQ3-2 Tele-Optic Mini-Giro Home-made P-mount -
Show Us Your Binoculars.
michael.h.f.wilkinson replied to LukeSkywatcher's topic in Discussions - Binoculars
Latest family portrait of my somewhat reduced collection of binoculars. Left are the two Carl Zeiss Victory bins: 10x42 mm in the rear, 8x25 mm (donning Opticron objective caps) in front. On the right we have the Helios LightQuest 16x80 mm in the rear and the Lunt 8x32 mm SUNoculars. I note there has been a shift towards roof prisms, and quality rather than quantity. -
Note that a front-mounted ERF (D-ERF or otherwise) just sits in ordinary daylight. It should not get hotter than any other surface exposed to dirtect sunlight. A D-ERF will actually reflect most of the heat, rather than absorbing much, so will stay comparatively cool. A thicker filter is needed at larger apertures not because it is expected to get hotter, but because it might otherwise deform. A half-aperture ERF, i.e. one halfway down the OTA (which is usually recommended as the smallest one you should consider), receives a 4x larger concentration of light, which is manageable for all sorts of optical glass, especially if it reflects the light and heat, rather than absorbing it.
-
Most likely, the view would be a lot better with an ERF of some kind. Apart from being safer, the thermal currents in the tube caused by the heat will be massively reduced. BTW, the thickness of the filter isn't really an issue in a D-ERF. In this case, the coatings do the filtering, the glass is merely there to hold the coatings in place. A smaller aperture requires thinner glass to do the job.
-
Just had them out under hazy skies, with some reasonably clear patches. Orion's belt stood out nicely, the stars pin sharp across the field of view. M42 could be spotted, but other DSOs like M65 and M66 were not visible in the haze. The optics seem very sharp, but deserve better skies to work properly. I did find eye placement a bit trickier than in daytime viewing, but a slight twist of the eye cups sorted that out. Normally I would use the bigger binoculars for astronomy, but it is nice to have a portable travel option.
-
I should add that using an ERF, which isn't required for a quark or Ca-K module, cuts down tube currents a lot. Imaging in Ca-K without an ERF in place causes considerable reduction in sharpness, I find. With my tri-band ERF (which transmits Ca-K, H-alpha, and the solar continuum band) gives much better results. It may be that the larger aperture scopes suffer from similar issues more than a 60 mm would when using a quark.
-
I certainly feel my 80 mm consistently outperforms my 60 mm. I have also use an 8" Tri-Band SCT (a modified C8 with coating on the corrector plate acting as a tri-band ERF), and there the effects of seeing are visible, but under good conditions, it shows a great deal more detail, both in white light and H-alpha. In Ca-K seeing is much more of a problem than in H-alpha, I should add. Both images below were taken with the tri-band SCT
-
It is always tricky to compare images with the visual impact in H-alpha. The H-alpha image itself is a uniform shade of red, and it takes a while to get used to that. I very often have people looking through the scope and first just seeing a red disk, and then suddenly gasp as the detail pops out. When imaging, I always use a monochrome camera, as I would be wasting 75% of the pixels otherwise. I then stack about 10-20% of the best shots, sharpen, and apply a colour look-up table which runs from black through red, to orange, then yellow and finally white, to bring out detail. Regarding the image quality, aperture of course plays a big role, but the bandwidth of your etalon has a major role to play as well. The LS35 THa and SolarMax have a bandwidth of 0.7 Å (0.5 Å if double stacked). The Solar Spectrum filter is much narrower, and gives more contrast (at a lower apparent brightness).
-
I have used various H-alpha scopes for imaging, starting with a second-hand Lunt LS35THa. Despite this not being intended for imaging, I got some pretty neat results (with a planetary camera attached). I then got a Coronado SolarMax-II 60mm, to which I later added a double-stack unit. I still have this one at work for visual purposes, after I got a second-hand Solar Spectrum H-alpha filter with telecentric lens (sort of similar to a Quark) which I use in my APM 80mm triplet refractor. The difference between the three systems in imaging is shown below (click for full resolution) Left to right: Lunt LS35THa, Coronado 60 mm single stack, APM 80mm with Beloptik Tri-Band ERF, Solar Spectrum 0.3 Å H-alpha filter and Baader TZ4 telecentric
-
Spotting a spring quasar: 3C 273
michael.h.f.wilkinson replied to John's topic in Observing - Discussion
I have spotted it quite easily with my C8. At magnitude 12.9 it should just be doable in a 130mm scope -
Very nice indeed. If clear outside is right and I get some clear skies I might well go for this target tonight and/or tomorrow night
- 1 reply
-
- 1
-
Upgrade the 15x70 "generic".
michael.h.f.wilkinson replied to tico's topic in Discussions - Binoculars
I have had the Helios Apollo 15x70s and they were excellent, but then the Helios LightQuest 16x80 came along, and it is slightly better and somewhat lighter than the Apollos. The Helios Apollo is a clear step up compared to the generic type, the LightQuest 16x80 is just as easy (or difficult) to hold as the Apollo 15x70, and a marked step up again. -
I did consider Swarovski, but like my comparison of 10x42 roof prism binoculars from Zeiss, Leica and Swarovski, I found the Zeiss just a touch more comfortable. Otherwise they are very close in optical performance. The store I went to didn't have similar Leica in stock this time, so I just compared two. Eye placement in binoculars is a very personal thing, so your mileage may vary.
-
Yesterday I bit the bullet and got myself an ultra light pair of binoculars (because of course I need more binoculars). The aim is to have a quality pair that I can keep in my coat pocket, so it can travel with me without adding much weight to my luggage. I settled for the Carl Zeiss Victory 8x25 pocket binoculars, given the stellar reviews, and the stellar performance of my other Zeiss Victory binoculars (10x42). These bins have a curious asymmetric design. and fold up to a tiny package. They come with a handy protective case but sadly lack lens caps of any description. I have found 33.7 mm eyepiece caps fit snugly over the eyepieces of these bins, but don't quite fit over the objectives. Optical quality is outstanding, as you would expect, and the eye relief is sufficient for me with my glasses. Hope to bring them to Texas for the eclips, and intend to make some solar filters for them shortly.