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Merlin66

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Everything posted by Merlin66

  1. Chris, Not exactly the same, but I have manged to record down to 3700A with a ATiK314L+ with the slit spectroscope. Without a UV cut it really depends on the optics and camera response. I'm interested to hear about your objective prism....I have a 20 deg f2 prism which can be mounted in front of my ED80.... early results with a FULL modded DSLR were very promising ( especially in the NIR) Ken
  2. Changing over to groups.IO now attract a ransom fee of $110/ year, they say this is the cost of procrastination.....change over prior to April 2019 would have been free......
  3. Yeah, a real bumma!! Google.groups doesn't look to well itself.... no recent updates and doesn't seem to accept transfer of data from an existing Yahoo group.
  4. Lots of features of Yahoo groups will cease on the 21st October 2019 including deleting attachments, message digests etc, etc. See https://in.help.yahoo.com/kb/SLN3101...pressions=true What are the options available to support a similar group?? I'm already aware of groups.IO (but at an annual cost to the owner of $110)
  5. Possibly not the best solution..... but I’ve use a C11 at f10 for spectroscopy mounted on a NEQ6PRO for the past ten years, no issues no drama.
  6. Nigella, I'd recommend Andrew's Tutorial ( see p 36) https://britastro.org/sites/default/files/BAA_BASS_Tutorial_0.pdf I usually crop the profile from say 3800 to 7000A, to make things easier. (The Astronomical spectroscopy website has recently been updated - worth checking out.... http://www.astronomicalspectroscopy.com/ )
  7. All the manufactures of the four element Petzval designed scopes (WO, Tak and TV) have put it in writing that their scopes are 100% safe to use with a Herschel wedge.
  8. Ok, but could the top plate be removed and redrilled/ modified to give more Az adjustment......
  9. I ‘ve been using TeamViewer for the past ten years between the laptop in the observatory and the office PC. what else can I say....works well for me, no issues, no drama.
  10. RonL, He states but doesn’t explain. As mentioned above the FOV brightness will diminish due to the higher magnifcation being achieved - for the same eyepiece used without the barlow. You would see the same effect using an eyepiece with half the focal length without the Barlow.
  11. Matt, What's the small orange piece and spring at the bottom - just odd bits? When you look through the "gap" at the base of the mount - anything visible??? Ken
  12. Matt, I think I understand the issue..... The text in the images obscures the bottom connection to the pier plates... Is there any option of re-setting/ adjusting the mount at this interface?? (or at the base of the pier??) Ken
  13. Louise, Although not the best solution the beamsplitter guider worked reasonably well. We developed a "virtual" slit which could be registered to the actual as a means of acquiring and guiding on the target star. A Vixen flip mirror body was used: http://www.astronomicalspectroscopy.com/files/Vixen mod.pdf Al's reticule was used... AlsReticule33.zip
  14. Louise, Think of the reflective slit plate as an off axis guider... but where the pick off mirror is large and on the optical axis so it picks up a guider FOV as big as the mirror/ guider chip. In the middle of this "pick off mirror" we have a very fine gap (the slit) say around 20 micron wide. We need to focus the target star into this slit gap and still be able to guide for as long as required. The starlight then goes through the slit and into the spectrograph....the light is collimated (made parallel) and reaches the grating which disperses the light into the spectrum. This spectrum is then refocused (after the grating) by the imaging lens (or the collimator in the case of a Littrow) to present a spectral image to your imaging camera. Hope this helps.
  15. Louise, The description and usage is very similar to the Classical spectrograph (but a folded optical layout) The links on this page may help:http://www.astronomicalspectroscopy.com/classical.html For setting up and usage: http://www.astronomicalspectroscopy.com/How_to.html
  16. Louise, On our files area : https://groups.yahoo.com/neo/groups/astronomical_spectroscopy/files/Paul Gerlach/
  17. Looks like you focused on the zero order star image....not the spectrum. http://www.astronomicalspectroscopy.com/gratings.html
  18. Yes, That's one of my books. I designed and constructed the Spectra-L200 Littrow spectrograph. This used a custom designed multi gap reflective slit plate from OVIO, very convenient. The latest generation of the 3D spectrographs are being constructed by guys like Paul Gerlach, John Paraskeva (BASS Project) and Tony Rodda among others. Some details on the astronomical spectroscopy group and webpage. http://www.astronomicalspectroscopy.com/instrument.html
  19. Vlaid, Check out the TransSpec spreadsheet - I think you have a copy. It shows the effect of focus and chromatic aberrations.
  20. RonL, Not sure where the "" However all barlows reduce light by 75% "" comes from. I could measure the actual transmission with the spectrograph, but I'm sure with today's coatings it's much better than 75%
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