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Everything posted by Merlin66

  1. Interesting. I've designed and built a few..... What focal length collimator are you thinking about? What resolution? A reflective slit plate is a better option than the beamsplitter (I've tried both!) A microscope glass slide works well (4/92) Checkout our website below for some ideas.
  2. Louise, Look carefully at the slit plate.. it is only reflective on one side.... The numbers look "correct" when viewed from the front (non reflective side)... The attached image shows the original OVIO slitplate I designed for the Spectra-L200.
  3. Louise, Definitely mirror face towards the grating. The guider can seen the reflection in the rear surface, no problems! I don't know what Paul did with the illuminator.......
  4. Looking good, well done! Definitely the reflective surface is at the rear, towards the grating. Any internal reflections then affect the guiding not the important spectral image. Ken
  5. Paul, I'm sitting in the study looking at an image I took of Comet Halley in March 1986. From Australia it was pretty spectacular - we had many visiting amateurs from the US, an exciting time.
  6. Louise, An f6.96 will be a good starting point, no need for reducers/ flatteners. Unless you intend to work with very faint, obscure stars/ targets I'm sure you'll find a well centred finder will position the target into the reflective slit aperture. I use a 260mm fl eFinder (with a DMK51) on the C11 @f10 (!!!!) and can easily position the target (I use FireCapture with cross-wire overlay) very near the slit gap. I use AstroArt or PHD2 for guiding. Plate solving with the reflective slit plate has two issues - the limited FOV and the secondary images from the internal reflections in the glass slit plate. If I use Plate solving (not very often) then I use the eFinder FOV. Ken
  7. Louise, The slit illuminator was used on the early non reflective slits (Surplus Shed) - I used separate beamsplitters mounted in front of the spectrograph to provide a guide image (Using Al's reticle ). As I said, the availability of reflective slit plates has improved over the years, and is the recommended solution. The QHY5_I will work pretty well as a guider, the imaging camera...start with what you have, you can check the wavelength coverage and probable R value using the SimSpec spreadsheet. I'm still using the ATiK 314L.
  8. Louise, I've tried slit illuminators.... (ASA, p203/4) but to be honest they didn't add any functionality. The key is it have a reflective slit plate which allows the slit gap to be seen (most of the time) against the sky background, and just position the target star in/on the gap and guide. AstroArt has a neat slit guiding routine. I also persuaded the guys at PHD2 to include a slit guiding option. This produces a "virtual" slit in the guide screen which can be positioned exactly over the actual slit position, makes life much easier. With the OVIO reflective slit plate you'll be OK.
  9. Good to hear! Onwards and Upwards
  10. I only do solar imaging.....getting a good flat is problematic.
  11. Yeah! I've just spent three frustrating days trying to clean motes from my ASI 1600 sensor. Looked OK when tested at f5....but add the PM and "they're back". A real PITA.
  12. Louise, The IR blaze angle would give a reduced efficiency for visual, if the original packaging is still sealed, you should be able to exchange. Ken
  13. Louise, I'd try to exchange the grating... you really need the 500nm for visual. Ken
  14. Marcel, As I said, moving the main mirror will increase the light hitting the secondary.
  15. Marcel, Moving the main mirror means that the focus is moved further from the side of the tube (usually done to allow easier camera access) Ideally a slightly larger secondary mirror would be required to maintain the same un-vignetted FOV. Usually the secondaries are over sized due to the standard sizes used, so not a major issue.. In general, larger secondaries allow larger field coverage at the cost of blocking more of the aperture and the impact on the Airy Disk. Many planetary observers actually reduce their secondaries to a minimum, just sufficient to give a small FOV around the planets.
  16. Fo_Cuss, The eye relief is the distance from the eyepiece to where the eye should be positioned to accept all the incoming light. This is where the size of the exit pupil should be measured. Pointed a camera into an eyepiece is always problematic, getting the best position and alignment can be difficult, that's why most imagers work with a lensless camera at the telescope focus without eyepieces.
  17. Fo_Cuss, Don't over think these things..... At f11 any eyepiece will work, and work pretty well. You probably have to consider the exit pupil and eye relief to suit your needs.
  18. Sounds like you’re quickly coming to terms with PST. Practice with the tuning , different settings will show different detail. ”The little scope which could....” Enjoy.
  19. Excellent result! I had similar motes on my ASI 1600 chip and it seemed to take forever to clean them up.
  20. Craney, RSpec don't manufacture the SA100, they only resell it with their software. Its produced by Paton Hawksley here in the UK. Gav, good start..needs a bit more focus on the spectrum, the "hump" at 5900 A is due to the Bayer matrix in the colour camera.
  21. Alex, The double stacked PST is a very nice introduction to Ha solar observing... Any of your current eyepieces will work with the PST, I actually use a 8-2 mm Zoom for convenience.... You don't mention which mount you will use with the PST. The only extras I can think of would be a solar shade https://www.stjarnhusetonline.se/magnify/906.1.html , or make one yourself http://www.billsastro.com/Astronomy/ATM/PST Sunshade.htm The Sun is still pretty quiet at the moment, but there are usually some interesting proms. Check GONG ( http://halpha.nso.edu/ ) daily to see what's happening. Ken
  22. A blatant plug....my book “Astronomical Spectroscopy for Amateurs” covers most of the design bases. Some very helpful links also on the Webpage (see below).
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