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UKAstroBill

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About UKAstroBill

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    Oxfordshire
  1. Borg responded with the useful detail that their filter adapter has an optical length of 31.3mm and is designed for IDAS filters, of thickness 2.5mm and refractive index 1.5168. So they have decided to calibrate well for a certain thickness, which makes a lot of sense. I’m ordering one and will try it out in comparison with the 2 inch version of FAstroTZ.
  2. All kinds of possibilities. Just make sure that when you screw in a filter it is clear of the sensor and the end of the lens. The Geoptik has plenty of clearance to ensure this and I screw the filter assembly well in to be clear of the lens. 1.25 is plenty for a 4/3 or DX sensor. meanwhile Borg have confirmed their part is fixed length and indicated they designed it with IDAS filters in mind. I hope to get more details after Thanksgiving. Don’t know the optical length yet.
  3. Space Oddities: I think it would be sensible for me to compare the Borg device to my 2inch prototype when I get to the next stage. I’ve emailed AstroHutech to ask them some questions especially about its optical length. Eg is the fixed length the same as the FTZ or is it calibrated at eg around 2mm filters with a larger optical length. Can you tell me what lenses you Use it with and what the image quality is like edge to edge? When I first built the 1.25 gadget I calibrated it to the FTZ by matching infinity focus without filters. When I put an Optolong l enhancer or Baader Halpha in the image quality was good edge to edge on the Nikon 200-500 but poor on wide angles. I mean that if you focused in the middle the edges were fine on telephoto but way off for wide angle. Adjusting the spacer up to allow for the filter made a big improvement for the wide angles, especially UWA zone. So I’m curious how well you find a fixed length part works at various focal lengths. If you have time! I’ll probably buy it anyway to compare once I’ve heard back from them.
  4. I’m not sure if direction matters! For a filter where it is the body of the material that does the job it can’t matter. I’ve been a bit anxious about whether a more complex layered design would be sensitive to it. Both the contraption in the video and my 2 inch prototype have the filter “right” way up but for the 1.25 case that was more to do with moving the filter away from the lens to kill the vignetting as much as possible. I’m more concerned about getting the right Backfocus though. A couple of days ago I spent some time calibrating the infinity focus on my gadget to various or no filters. The device seems to be a bit wider than the manufacturer data suggests and it was calibrating to close to FTZ infinity focus with a 0.8 mm spacer, and 1.4mm nailed it for the Optolong L enhance, with the Baader Halpha wanting a tiny bit more, though I left it at 1.4.
  5. Thanks Mark - There is some discussion of this in the video. On the Nikon 200-500 there is hard vignetting at 500 but the 1:1 crop is fine. On a dedicated telescope you would almost certainly get the same. On my scopes (an APM 107/700 and a Celestron C6 with reducer) I have 2 inch filters in line and just do not use this contraption.
  6. That's great for the 2 inch case - thanks for pointing this one out. I was hoping this post would turn something up. Costs a bit more than my contraption though. My main concern is whether it allows adjustment of the back focus distance for the effect of the filter? I've been doing some focus fine tuning and have discovered that if you do not correct for that you have to focus quite a bit short of where infinity was in the ordinary FTZ.
  7. Weather in UK is dire at moment. Biblical rain. I’ll get out eventually. But on the matter of “need” there are all kinds of projects. I picked up my Halpha filters today at the Astronomy show with a view to seeing if I can synthetically astro mod the Z6 in a less crude way, given that it appears to capture a bit over 20%. The layout is great and having focus peaking give you a first fix is amazing.
  8. The weather has been so bad I have had the time to finish a video on using astro filters with the Nikon Z bodies and Nikon camera lenses. There is a manual alternative to the FTZ allowing 1.25 inch filters to be fitted between camera and F-mount lenses, and for some lenses and end of lens solution make sense. FAstroTZ is described here:
  9. Six years later and same problem. Have cut mine.
  10. I've got the Geoptik working with various Nikon and 3rd party F-mount lenses. I have had no problems keeping the aperture wide open. 1. There is a pin in the Geoptik that holds the aperture wide open for those lens that support mechanical aperture control; e.g. Nikon 20mm f/1.8; Samyang 12mm Fisheye, Sigma 35mm Art 2. For lenses like the Nikon 200-500, the pin does not work, but if you detach the lens from a camera before turning the power off the aperture stays in the last position. I have had no problems using this at f/5.6 on the Geoptik. Nothing bad has happened to lens or camera doing this. My issue with the Geoptik is its attaching mechanism, my least favourite. Hard to see why they could not have a secure click option rather than the annoying orange tightening screw. *** QUESTION *** But I do have another question about the Cyclops Nikon lens adapters as I am looking for 2 inch compatibility which the Geoptik does not have. Can any one tell me the camera side interface, in terms of thread AND gender and depth if you know for (a) the Cyclops Blade-N Nikon gadget (b) the simpler M54 Nikon adapter (part 020073) (c) the simpler M42 Nikon adapter (part 020074) For the last two it is obviously the gender I am after! By the way, if anyone has a Nikon Z and some F mount glass, the Baader wide T mount for Z attaches to the Geoptik and lets you have 1.25in filters in line. They screw together to create an optical path about 1.2mm shorter than the Nikon FTZ, but it allows the filters and you can space it out if you are fussy. Thanks William
  11. Mark what exactly did JTech make for you in the end? M62 female on flattener side I guess but what did you have camera side? And what was the optical length of what you got from them? ta william
  12. JTech have Also been recommended to me, by FLO. It’s a bit frustrating that Sky-Watcher have picked such an idiosyncratic thread size for the camera side of the reducer. I’m trying to attach a Nikon Z using Baader UFC system and am hung up on this link and how much Backfocus is going to be eaten up. Anybody found any new good solutions to attach to then M62 male flattener camera side?
  13. The back focus calculations change somewhat if you work with a Nikon Z system with a much smaller distance to the sensor in the camera. I think it makes the Edge 8 a much more practical proposition.
  14. So I am looking around for an imaging refractor and the specs of this imaging star for the price caught my eye. The info I have seen suggests 73mm from the M68 adaptor to the sensor and a 42mm imaging circle, and there is a viewing option now with an adaptor. The first distance is easily created with some Baader bits and the second figure suggests most of a full frame sensor will be lit. So I am not sure what the problem is? Is the 73 wrong? Is there a lot of vignetting at 42mm?
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