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jonstarrysky

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  1. jonstarrysky

    Slide 1

    From the album: collimation

  2. That's all very interesting. But instead I will talk about the Watec camera..... Only kidding... good luck with the project. Don't see the attraction myself. The secondary mirror does a very good job of bringing the focal plane out the way of incoming light, so you can put as much clobber there as you wish and its not casting a shadow. Regarding getting rid of the secondary, quoting Suitor: "as long as the obstruction is kept inside that fraction [20-25%], the image closely approximates that of an unobstructed telescope." And a camera might well weigh more than a secondary mirror. I know of someone who has the kind of setup you refer to. Hoping to take a trip to see his obs sometime, will be interesting how it works out in practise...
  3. Seems an obvious gap in the market. The Mallincam Universe has a 1.12" chip (28.4 mm). http://mallincam.tripod.com/id56.html Claims magazine quality images from live view. But no analogue output for a slimmed-down pure "electronically assisted" visual approach.
  4. Talking pure video astronomy (camera analogue output fed direct to AV input of monitor), it seems these vid cameras are based on CCTV units. These typically have small 1/2" or 1/3" chips. Means equilavence to a 6mm eyepiece i.e. narrow field. Contrast that with full blown CCD imaging or dSLR, with their huge chips and big fields. So has no one developed an astro video camera with a big chip ? Mallincam have their "Universe" that does this. But ....that looks more like an imaging decide for me. Only USB output, and laptop is essential... Seems like to get the big field, you are forced down the digital route.....
  5. thanks Macavity, Good point about capture being asynchronous....Just noticed they do a cheap USB capture dongle at Modern Astronomy. Might be useful for evaluating tweaks and kit options (eg comparing filters and focal reducers) when it's cloudy...
  6. So some interesting feedback re focal reducers. Indeed autocollimation is the way to go for alignment accuracy. I'll be using a Catsete XLK infinity. My Servo-CAT 18" scope with the Watec will be an interesting experiment then..... The 18" will also have a new quartz primary mirror in a few months (of no relevance here, but I just cant wait for that !!!) OK, so equivalence to 6mm eyepiece is really pushing it. Technically and the kind of target objects. It the tracking is up to it, potentially awasome. But I can see my piggybacked 4.5" f/4 Newt getting most of the Watec action, as a worst case. Visual on the 18" and monitor on the piggyback 4.5".... I have several reducers to play with. One from modern astronomy, and two from Mallincam with variable spacers: MFR-3 and MFR-6. The MFR-3 is supposed to be ideal for Newts. And MFR-6 has a modest reduction ratio (0.7x I think). I plan to incrementally increase the redution factor till either there are image quality issues or .....I run out of in-focus. I asked for an inch longer FL for the new primary mirror, so will have more in-focus to spare (focus position moved out by an inch). And I bought a 1.25"-2" camara adapter that in effect buys some in-focus vs using a normal 1.25"-2" focusser adapter - the camera body goes flush against the 2" focusser drawtube opening. See http://mallincam.tripod.com/sitebuildercontent/sitebuilderpictures/2inchadapter.jpg I guess an image capture device may be called for at some point to document some of the results.... (not that imaging is the prime objective).
  7. Hey thanks for the posts you three. Good to know there are some users of the Watec left, with all the Lodestar talk. I guess this (or similar) will be the inevitable conclusion at some point. Or the Mallincan Universe....For now, my 18" dob has been set up for analogue video astronomy keeping things simple, using a classic analogue vid camera. The whole video thing - power, cables, monitor etc is integrated into my dob (no trailing cables or table) Peter, interesting you advocate mono. I was led to this via the Watec possibly running out of stock, my kneejerk entry into video, and later realised mono actually makes a lot of sense (eg sensitivity, allowing filters that mess up colours, taking in IR etc). I enquired about the peltier cooling, this mod is still available in the USA, so looks like a likely trip for my Watec...Your camera at prime focus project sounds interesting, I've heard of this being done. How will you collimate ? I bought several filters. Astronomik CLS & UHC and Lumicon "H-alpha Night Sky". Three choices of increasing severity. They all retain long wavelengths of >650nM, but progressively chop away at the shorter wavelengths. The Lumicon is a long wavelength pass filter that only lets through wavelengths longer than 650nm; all else is blocked. Apparently works well on DSOs including galaxies, which are actually bright in the longer wavelengths. Some tech questions: 1. With a f/4 newt the Watec wont show much coma ? How about with a reducer added on ?? Presumably going to cameras with bigger chips coma starts to take effect ?? 2. What do folks think of focal reducers on already fast Newts. I have a few to try, and spacers. I am reliably led to believe that reducing from a starting point of f/4 is tricky in terms of optical aberrations. I was told f/5 reduced to f/3 is easier than f/4 to f/3.....The bigger I can get my field the better. I was led to believe the Watec will behave like a 6-8mm eyepiece, which is pretty high mag on am 18" scope
  8. Just wanting to touch base with folks actively using this camera. Be interested to hear experineces eg what people use it for, kind of scopes being used, hints n' tips, filters, mods (eg cooling). I recently bought one for an 18" f/4 dob with ServoCAT tracking. Also for a 4.5" f/4 Newt OTA that rides on the back of the 18"........ Looks like a lot of the discussion on the forum related to the Lodestar. In the first instance I was wanting to get into video with an analogue video output to keep things simple. I really like the analogue feel of the Watec and its controller, good old knobs ! Cheers, Jon
  9. Hi, there's a site at Hatfield forest, not the regular car park. Used it a few times and not been hassled yet. Sites in North Essex have yet to be identified as far as I am aware, eg just South of Haverhill, North of Finchingfield is predicted to be dark from LP surveys, but there is no obvious suitable public ground eg a car park or public access space. Kind of frustrating. If you find a place there pls let us know. Folks on this forum have met in the Rodings area, details found on previous threads, technically (like the Hatfied forest site) it will be substantially light polluted, but may be worth a try, good luck !
  10. M57, M13, M27, M11 These are probably the most spectacular summer deepsky objects that are easily within the grasp of 4". Make sure you see all of those, then move on to the other stuff, probably including some easy doubles like Albeiro, the double double (epsilon Lyrae), Nu draconis. Check out the garnet star in cepheus for some colour....Check out the milk way in Cygnus using your lowest power eyepiece.
  11. Welcome Matt, there are a few of us in Bishop's Stortford who take trips out to observe (big dobs), locally we use Hatfield Forest (OK but not a proper dark site), we also have an overnight spot in Suffolk (very dark). Let me know if you're our end of the county or if you find any good spots this way. South of Haverill should be dark but haven't identified a practical spot there....
  12. OK, I thought I'd post this question here, technically not the video astro forum, but I suspect the knowledge-base is here.... I'm getting the Watec WAT-120N+ astro video camera, to feed direct probably into an 8" portable LCD monitor mounted on my scope, for live deep sky viewing, not imaging. The camera output is Composite Video of resolution 570TVL (horizontal) x 570TVL (vertical) and is fed to a monitor via a BNC socket. Typically this camera would be hooked up to an old school cathode ray CCTV monitor. So I want a medium/ small LCD monitor that is mountable on the scope. The monitor would have a native screen resolution eg 1024x768 pixels or 800 x 600 pixels, or 640 x 480 pixels, and probably selectable for the actual display resolution. Such as here: http://www.hunters-wholesalers.co.uk/images/DSM8WGF-Datasheet.pdf http://www.hunters-wholesalers.co.uk/images/DS9.7LED-Datasheet.pdf My question: with a video camera resolution of 570TVL (horizontal) x 570TVL (vertical), what is the most ideal pixel resolution of an LCD monitor used with it ??? And is there potential for freaky stuff to happen eg the view being stretched due to wrong aspect ratio on the monitor, differing pixel shapes, or the image being over/ under sized relative to the actual screen ?? Cheers, Jon
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