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Gina

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Everything posted by Gina

  1. With the camera cooling running the casing gets slightly warm and so does the lens so I don't think dew will be a problem but it wouldn't hurt to direct the warm air up to the lens. I'll produce a casing [removed word] support bracket tomorrow.
  2. Connected the 12v power input to the camera so that I could run the cooling. Now down to -17°C and no sign of misting up so I think the desiccant tablets are fine. The view of the far hill several miles away is clearer in the image than it is with no.1 eyeball - it's covered in mist. That shows how well red light goes through mist (Ha wavelength).
  3. Been checking on previous NB imaging (getting on for two years ago) to see how much total exposure I might need to get something reasonable. The Quote below is from my Widefield Single Imaging Rig Blog. Camera temperature was -30°C. I can go up to 90s before significant star elongation and the lens is f1.8 rather than f3.5 which is about 2 stops better (4x as much light), so overall a x12 in effective maximum exposure before needing tracking. I think this is hopeful.
  4. Now like everyone else, I want some clear night skies! The weekend might be alright except for the full moon!! Not so bad for NB, of course. And the narrower bandwidth the less bright the moon is compared with nebulosity. Maybe I should have put the 3nm Ha filter in the ASI 1600MM-Cool camera. I still could, of course.
  5. I think I have an idea for easy dew prevention - redirect the warm air from the camera cooler up to the lens. Air would be drawn in from the bottom of the camera, through the cooling fins and out the sides. The next question is where to put this rig. The observatory scope room and EQ8 mount have obscured views to north and west. On a pole like the ASC may be a possibility (I have the other half of the length I cut for the ASC) but with a fixed rig the stars will rotate around Polaris (possible corrected in the stacking). Alternatively, I could produce an extension attached to the mount and follow the stars. Of course the FOV changes as the night progresses whatever I do. For NB imaging either long exposures or many short one ares needed to get enough data fro a decent image. This may mean imaging over several night due to the changing FOV as the night proceeds. It will be interesting if this idea will actually work.
  6. I've taken the Astrodon 5nm Ha filter out of my filter wheel, taken the filter out of the mount and fitted it inside the ASI 1600MM-Cool camera. I've retained the desiccant pellets as they were fine last time I used this camera but a nighttime run will tell. The image above taken with the Ha filter in the camera. Should add - I already have Astrodon 3mm Ha, OIII and SII plus IR/UV cut in the FW.
  7. I'm using the lens that I thought was imperfect but now I'm wondering if it was dew or something else that caused the stretched stars near the edge. I've been waiting for a reply from the seller but I think I'll do some more tests before sending it back.
  8. I think I like option 2. best. Less to do and better performance. Lower resolution but still plenty I think.
  9. This gives me two options :- ASI 178MM with a cooling setup like the ASC - a lot of work and a Peltier TEC to buy even then the cooling is nowhere as good as a proper cooled camera. It all needs a dry chamber same as the ASC. ASI 1600MM-Cool with a filter placed inside the camera in the dry chamber. This is my No.2 1600 which is a ZWO version 1 and several years old. The top unscrews and the inside is dried with desiccant tablets. I imagine silica gel will work just as well and there's quite a lot of room. Some sort of dew prevention will be needed for the lens but being well away from the cooling system a simple dew heater may be adequate.
  10. The Fujinon lens focuses alright with the ASI 1600MM-Cool without filter. Here's an image using ROI 1500x1500 pixels at X=1550 and Y=1000.
  11. Won't reach focus with 1600 and Astrodon filter. I'll try Baader. A little later - nearly but "no cigar"! This screenshot shows the size of the image circle in the full frame of the ASI 1600MM-Cool.
  12. Set up the ASI 178MM firstly with a Baader 2mm thick filter and got focus fine so tried an Astrodon 3mm thick filter and I can focus with that too with space to spare using the filter unmounted. Yippee So what was the matter with my calculations??? If my calculations for the ASI 178 were so far out I wonder about the ASI 1600.
  13. APS-C lenses won't cover anything like the whole sky with a 4/3 sensor as in the ASI 1600MM-Cool camera. 8mm FL ones are available for £100-£150 which would give much more coverage that the 28mm M42 lens I already have but probably "fall between two stools". Seems a lot to pay for experimental imaging in my present financial state.
  14. Googling the spec shows that the "micro four thirds" standard has a flange to focal plane distance of 19.25 mm, only about 1.75mm more than C mount so there still wouldn't be room for a filter with the ASI 1600MM-Cool camera. There goes another option!!!
  15. The alternative might be an M4/3 camera lens which I've read is compatible with the ASI 1600 camera. Found one on ebay which is almost whole sky (maybe across the diagonal). UK 7artisans 7.5mm F2.8 Fisheye Lens Manual Fixed Lens For Olympus Panasonic M43
  16. In the fresh light of day (and a fresh brain), I can do some calculations :- For a C mount the flange to focal plane distance is quoted as 17.526 mm. The objective lens element of the Fujinon fish-eye lens projects 8mm below the flange. Thus focal plane is approximately 17.5 - 8 = 9.5mm. Distance from sensor to front of camera is 7.5mm for the 178 and 10.5mm for the 1600. So the 1600 camera shows an interference of 1mm and cannot be used with the Fujinon lens even without filter! With the 178 the gap will be 9.5 - 7.5 = 2mm. Astrodon filters are 3mm thick Which is no-go!!! Interference of 1mm! BUT a filter moves the focal plane out by 1/3 of the thickness = 1mm Well, I might just get away with using the ASI 178MM camera with a filter but there is a severe danger of the lens touching the filter.
  17. Great stuff!! Wish it was Northern Hemisphere though so that I could recognise things. I want to make an ultra widefield image from here but it wont be high resolution - that Southern Hemisphere image is amazing.
  18. Been looking at the ASI 1600MM-Cool and various adapters plus a 1.25" mounted filter. The ZWO lenses supplied with the smaller astro cameras are CS mount and definitely won't work with a filter in between. Nor will the Arecont type 1.55mm FL lenses which are also CS mount. The Fujinon fish-eye lens is C mount with 5mm longer focus distance and even that won't work with a mounted filter using the supplied adapters. Next, I tried taking a filter out of its mount and putting the filter directly on top of the camera window but the lens has a protruding part for its objective element and I'm pretty sure that will touch the filter before focus is reached! Drat!! The ASI 178MM has the sensor nearer the front and I think an unmounted filter may work with that. Distance from sensor to front of camera is 7.5mm for the 178 and 10.5mm for the 1600. That 3mm might make all the difference. I'll set up a test rig tomorrow.
  19. Looks like the ASI 1600MM-Cool will be alright for focus with a 1/2" format fish-eye lens. The 178 has smaller pixels (2.4µm) so better resolution v 1600 @ 3.8µm. OTOH the bigger pixels mean better sensitivity. I can use ROI covering an area of about 1200x1200 pixels, to fit the image. This compares with 2000x2000 pixels for the ASC thought that is colour so really only 1000x1000 picture elements. Two screenshots from the specs for the ASI 178MM left and ASI 1600MM-Cool right.
  20. Crossed posts... Yes, the curvature would be a big problem with a mosaic. Mosaics are alright with long focus but not with short - forgot that. Drat!
  21. Ha is very faint and OIII is worse and as for SII, forget it (probably). A well cooled astro camera would seem to be called for so for me that would be the ASI 1600MM-Cool. I can get down to -20°C by cooling the casing with a Peltier TEC as shown in my ASC and I have an ASI 178MM which is fine with a 1/2" format fish-eye lens but accommodating a filter is a problem. The ASI 1600MM-Cool can take a filter just in front of the optical window but I don't think a 1/2" fish-eye lens would reach focus. I'll have to check. Of course, the image would only be a fairly small circle in the middle of the sensor. Another possibility might be to capture a mosaic of the sky using the shortest FL standard camera lens.
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