Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.



Advanced Members
  • Content Count

  • Joined

  • Last visited

  • Days Won


ollypenrice last won the day on November 19

ollypenrice had the most liked content!

Community Reputation

20,754 Excellent

About ollypenrice

  • Rank
    Neutron Star

Contact Methods

  • MSN
  • Website URL
  • Yahoo

Profile Information

  • Gender
  • Interests
    Imaging, Cycling, Thinking, Literature, French culture, Mountains...
  • Location
    South east France, Lat 44.19N.
  1. I'm an anti-gadget astrophotographer. It would do no harm to build up an idea of how temperature change affected focus but but instinct tells me that creating a hard and fast link between focal distance and temperature will never work. I certainly wouldn't trust it. There are variables everywhere. Olly
  2. I do sense a problem in this reply. It may be a matter of wording. If we take, 'Ha signal captures all the details and combined with a narrow filter ,smaller stars.. you can expose for longer without the light polluion affecting the image..capture more details with smaller stars..awesome...the only thing it won't give you is star colour..thats the only downfall I can see..the rest is a positive' and apply it to shooting the Pleiades we can see that it can't be right. There is insignificant Ha signal in this region but there is ERE (extended red emission.) Likewise you could shoot galaxies through a filter which passed only deep red (an Ha filter) but why would you do that? Galaxies do not emit primarily deep red light. I think it's important to be clear why we use the filters we do. I shoot through (amongst others) red, luminance and Ha filters, all of which pass pretty much identical amounts of Ha light. What matters is not the light which the filters pass but the light which they block. The Ha filter allows the imager to extract those structures which are shining in Ha and emphasize them in the final image. Without careful processing, shedloads of Ha light will not make for a better image. Olly
  3. ollypenrice


    I like your image. Sure, there are halos but these are very bright stars which throw up stellar artefacts which we see in all sorts of bright star images. The halos are probably internal reflections and the spikes we know about from spiders. I'd rather concentrate on your tight focus, crisp, tight field stars, well colour-balanced background sky and well-judged black point. Good image. There it is. Olly
  4. The resolutions were 0.66 for the big scope and 0.9 for the small one. Realized detail was honestly about the same. The test was complicated by the greater sensitivity of the small pixel camera. In fact the smaller telescope with smaller but more sensitive pixels was probably faster but I didn't have the original raw data to explore this side of the comparison. In priniciple I agree with you, though. Olly
  5. In my view these conversations spend too much time on the weight issue and not enough on the accuracy which, at these pixel scales, can be the dominant factor. Olly
  6. Given the general agreement over the 'greats' I think a thread on 'under-rated or unsung' scientists would be interesting. In the twentieth century you'll find more mention of Shapley and Hubble than you will of Walter Baader, for instance, but should this be the case? And such a thread might lead to interesting 'further reading.' I'm mortified to say that your Emmy Noether was new to me. (It's rather a shame she didn't work with Michelson and Morely...)* Olly *I know, inexcusably bad...
  7. Why are you keen to add resolution via focal length and then reduce it via binning? It really doesn't matter whether you fill the frame or not. What matters is how many pixels (single or 4 pixel superpixels) you put under the object's image as projected by the telescope. It is this which determines the object's image's final size at full size (1 camera pixel = 1 screen pixel.) * Earlier in the year I did a comparison in Astronomy Now between a 14 inch scope (2.4M FL) with large pixels and a 150mm scope (1M FL) with small pixels on galaxies. I found that the level of resolution and the size at which the images could be presented on screen was effectively the same. It seems that the considerably greater optical resolution of the larger scope was not translating into more final details. In both cases the mount was running with an RMS of less than half the image scale. Personally I'd look for a scope with a FL which will give you about an arcsecond per pixel or a tiny bit less and make it the kind of nice simple design that you know you will find productive. I've struggled with one of those RCs with a guest and got nowhere. The theory is one thing but this example did not behave according to the theory. Olly *Not the best sentence I ever wrote!
  8. ollypenrice

    Hell and The Devil in Astronomy?

    'Why this is hell, nor are we out of it...' (Marlowe's Faustus.) Olly
  9. Of course its anthropomorphic. How can something have 'cultural impact' without being so? I didn't suggest that cosmological theories were 'less profound,' I suggested they they have less 'cultural and philosophical impact,' than evolution by natural selection and I believe this to be so. Darwin's spin-off takes us into both politics and religion so we'll stop there. You're perfectly free to feel that a scientific theory doesn't have to be judged on its cultural impact and I might well agree with you, but my response to the OP involved offering one definintion of 'greatest' and testing the theories I know of against that one. Olly
  10. Maybe the great thing about science is that it's cumulative, so one person's contribution is built in response to a predecessor's contribution. Einstein built on Maxwell. In part Relativity arose from his conviction that Maxwell's equations were too beautiful to be wrong. But both Maxwell and Einstein needed the notion of a field, which they drew from the humble Michael Faraday. And so on. However, I don't believe that the greatest single scientific theory comes from physics or astronomy. It comes from biology: Darwin's evolution by natural selection. Although it's been edited and refined the essential bulk of the theory really is Darwin's. I think it's the most robust theory in science and will remain so. And I think it has had by far the greatest cultural and philosophical impact because it tells us the single most important thing about ourselves, an insight which triggers other insights branching off in all directions. So I'm going to conclude that science itself is the hero of the story. The gradual and unseen evolution of scientific method has created humanity's greatest intellectual achievement. It's beauty lies in the fact that it has many authors. Olly
  11. ollypenrice

    NGC 1333 lum.....done?

    You're winning! Olly
  12. ollypenrice

    First LRGB -M45

    You're right, it isn't a negative curve. My mistake. Still, your top fixing point is putting in a kind of curve I try to avoid. It reverses the 'trend of the stretch,' shall we say, and will affect the brighter nebulosity as well as the stars. Olly
  13. ollypenrice

    14” Meade RCX

    I have a 14 inch LX200 and I have two EQ sixes but I wouldn't mix them! Don't consider putting such a thing on an EQ6. It would be massively overloaded. I think an EQ8 would be fine and a Mesu best. Controlling focus could be a problem though. Is there no manual mirror mover of any kind? Olly
  14. ollypenrice

    First LRGB -M45

    Incomparably better. That's turning into a classy image. It is so important to get the background right and it can be very tricky. Goran's control curve for the stars is one way to do it and it's worked. However, I'm wary of introducing a long negative curve, just in principle, because it inverts the recorded histogram. I favour a layers approach in Ps in which I would blend the stars from a softer stretch into the image you have now. That way you confine the modification to the area just around the stars themselves. It's great to see an image come right in this way. Good going. Olly
  15. The 'flashlight test' makes anything look horrible. Ignore it. Nice one from Dave here! Olly

Important Information

By using this site, you agree to our Terms of Use.