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fwm891 last won the day on October 27 2019

fwm891 had the most liked content!

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About fwm891

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    Retired Photographer

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  • Interests
    Astro Imaging, Acoustic Guitar building, Making own equipment, tinkering...
  • Location
    Kingstone, Hereford
  1. Noticed these while walking the dog this evening. Quite strong colour (I have added a little saturation too) They had faded a bit by the time I got back and grabbed a camera but still a good display - best I've seen both sides of the Sun for years.
  2. Bill, I think this is where you're getting confused: Your motor gives 0.9° per step. You want to micro step x4 steps = 0.225° per step. OK with that? your reducing the step size so the angular movement per micro step will also be reduced. Divide 360° / 0.225° = 1600 steps per 360° rotation of the motor. Your Horse shoe is 1219.2 diameter giving 3830.22976... circumference Your pully is 11.9 diameter giving 37.38495... circumference Your motor needs to turn 102.453788... times per sidereal day Total micro steps 102.453788 x 1600 = 163,926.061583.... in a sidereal day There are approx. 86,164 seconds per sidereal day (ignoring decimals) Therefore you motor needs to run at 1.9025 steps per second to drive your 1219.2mm horse shoe at sidereal rate. I think you've got timing and distance measurements crossed. At approx. 2 steps per second that will appear jerky in an eyepiece so you may want to either increase the micro stepping rate, or add a reduction gear to increase the number of steps per second. Old movies used 16 frames per second as a minimum rate as below that rate visual persistence showed flicker. Hence why its common now to use 25, 30 and higher rates to smooth out motion. I hope that helps Francis
  3. Problem there is that you have to re-collimate both ways when you add/remove the secondary assembly.
  4. The observatory stayed closed due to wind last night but it gave me another chance to use the ASI 294MC Pro with my 70-200mm f2.8 Nikon lens with an IDAS NB-1 filter. Orion was shot at the bottom end of the range at 70mm the others at circa 100mm. exposures ranged from 30s to 180s. quite a few subs were lost to clouds but I was pleased with the CEM25P mount's tracking. All subs were unguided which given the windy conditions I felt was good. I need to shoot some calibration subs for these images at some stage. The image of IC1805, IC1848 plus 2017 T2 (Panstarrs) had 60s and 180s subs. The others were 30 and 60secoonds. The grouping of IC405, IC410, M36, M37 and M38 is probably my favourite for the night. Both above were slightly cropped but the Orion image is full frame.
  5. Superb Martin - one of the best images I've seen posted for a long time (even mine!)
  6. Images of the eccentric added
  7. I've been playing and come up with an adapter allowing me to fit my Nikon lenses to my ASI294MC Pro cooled camera body. The adapter is based around a Nikon lens to Canon body adapter (it was in my kit box doing nothing !). This is fitted into an aluminium body (main body in photo) with 6x 2mm metric machine screws. The 294 has a 42mm male T thread, I've used this to fit the camera body to a small aluminium insert which slides into the main body of the adapter. I've threaded the front of the insert to take 48mm filters. To allow the lenses to be changed easily I have inserted an eccentric cam to depress the release lever - operated by the brass lever on top of the adapter. The main body has a slip ring/clamp arrangement to allow the whole adapter/lens/camera combo to rotate for framing. I've etched (scratched!) 10° markings around the main body to act as an aid when framing. Currently fitted to a shortish Vixen bar but this will be altered so when using longer lenses to front of the lens will be supported to reduce loading on the adapter/lens mount. Photo of the adapter with the 294 and a 24-85mm Nikon lens. Also a section through the adapter (not exactly as built I made a couple of minor changes as the machining progressed. An image of the rosette nebula from it's first light session last night. It needs a few tweaks but it works. Images of the eccentric and adapter/294 with IDAS NB-1 filter in place
  8. I've been making an adapter to fit Nikon lenses to my ASI294MC Pro (uncooled test) and last night cleared for a short while to get a few test frames with this set-up. Mount iOptron CEM25P (Unguided) also unbalanced as the original counterweight was way too heavy so shot with no CW. Lens Nikon 24-85 f2.8 zoom (D series) Camera: ASI294MC Pro (uncooled) for test. Filter used: IDAS NB-1 filter Processing: APP for stacking, PI and PS for colour. I should have got out earlier for the Orion frames (2x 60s) as it was disappearing into my gutters so switched to the rosette and the Heart & Soul areas where I had a little more imaging time. Rosette: Lens set at 50mm but heavy crop for final frame Orion: Lens set to 24mm again heavy crop H&S: Lens set to 50mm and cropped.
  9. I like to tinker with bits like adapters so when I came this morning to test my latest gadget to link my Nikon lenses to my ASI294 MC Pro I couldn't quite believe my screen images - there was this round object where a round object shouldn't be? Quick check: stars in focus, aircraft moving across FoV, clouds passing (fast) and it's still there! I had the camera and 24-85mm lens mounted on a bean bag on the window sill with the lens leaning on the double glazing pointing up at about 45°. I'd pushed the gain up to about 500 in SharpCap(3.2) with 3 sec exposures to avoid too much trailing. I took a couple of snapshots to plate solve later then tried SharpCap's live stack to see if I could reduce the noise around this mystery object. That's when the penny dropped (plonker) that mystery object was a water droplet hanging under the gutter and catching a local street lamp... It wasn't moving with the star background but with the short single frames that wouldn't show. It was only viewing the livestack that things began to register (no pun intended)...
  10. Your background looks a bit dark - maybe my monitor but to me needs to be taken to a darkish grey rather than black...
  11. @Osprey Oops see below... Typo in above... Total = 86,164.0905 seconds in a sidereal day which is the length of time the Earth takes to rotate 360° or 239.434469 (original calc showed as 234.34469 sec) sec per 1° = 3.989078 mins per 1° rotation 3.989078 mins per 1° rotation then 360° = 1,436.06808 mins for 360° If your motor does 200 steps per min. Then for 360° rotation = 1,436.06808 x 200 = 207,213.616 steps per sidereal day Sorry about the typo
  12. @Osprey You need to first break it down to give you the number of seconds in a sidereal day: 23 x 60 x 60 = sec in 23 hours = 82,800 Plus 56 x 60 = 56 mins in seconds = 3,360 Plus the odd 4.0905 sec Total = 86,164.0905 seconds in a sidereal day which is the length of time the Earth takes to rotate 360° or 234.34469 sec per 1° = 3.989078 mins per 1° rotation Your stepper motor will give 200 steps per minute = 47,868.9391666 steps If you drive your horseshoe directly from the 5mm diameter shaft at 200 steps per minute then: 5 x pi = 15.70796 mm surface travel per shaft rotation in 1 minute. There are 3.989078 mins per degree rotation = 62.6602776 mm travel per 1° x 360 for full rotation = 22,557.6999 mm or 22.5577 metres for your horseshoe circumference Divide by pi = 7.180.34 meters diameter. You will need to gear down the motor by some factor to bring the mount to reasonable proportions or use micro stepping... Hope that helps...
  13. I use a TS Optics 80mm guide scope and ASI120mm camera combo which I switch between scopes. For the f2 RASA I get 1:1.104 ratio, with the Altair 115 EDT APO I get 1:2.04 and the little William ZS 73 +ASI294MC pro and 9x 50mm guider (ASI120mm camera) I get 1:2.06 Great little prog.
  14. fwm891

    M78 area

    There's very little tolerance with the f2 RASA. I've made my own spacer/filter holder to give me the 25mm back focus. The filter at present is not sitting quite square on and causing a few distortions (left to right in above image) though that may also be due to the IDAS NB-1 filter not being well corrected for the f2 light cone. Correcting the mount PA last night has made a big difference and something I will check more often especially after working round the mount / tri-pier.
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