Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_comet_46p_winners.thumb.jpg.b3d48fd93cbd17bff31f578b27cc6f0d.jpg

bobro

Members
  • Content Count

    559
  • Joined

  • Last visited

Community Reputation

565 Excellent

About bobro

  • Rank
    Proto Star

Profile Information

  • Location
    Isle of Wight
  1. Quite lovely and the (candifloss) nebulosity is great. Rotated left 90 degrees provides a view easier to appreciate on a computer screen. Makes me want to dig out the 135mm lens I purchased a while back to try a bit of wider field - but never got round to doing!
  2. Quite amazing what can be achieved in processing. Whilst not astronomically correct, I'm drawn to the starless version - sometimes less is more!
  3. Would be interesting to see the full frame.
  4. As @david_taurus83 suggests, practising with polar alignment and bright star targets such as M13 (or M3) is a great way to tune your setup and can get you ready for winter when the bright Orion nebula etc comes into view. Imaging galaxies unguided is harder as they are much dimmer. I recently destroyed my guide camera by plugging too high a voltage PSU into a hub, forcing my setup back to EQ5 unguided. I have to say the subsequent images weren't great - even at 30 secs. There's something I haven't quite got right with my setup, so it depends on guiding to keep it on track. If you can get your EQ5 tracking well unguided that will be a great start. Good luck! Bob
  5. The dual axis motors are in fact stepper motors, which allow the simple handset to accurately track a target in the RA axis direction in order to keep the target in the same position in the fov. I initially used the dual axis motors with AstroEQ before upgrading to motors better suited to goto. As mentioned above, there is no goto functionality with the simple handset - a synscan handset and motors are required for this. A major drawback of the dual axis motors is the painfully slow slewing speed due to the motor gearing - takes an age! That means it is often best to unlock the clutches and point the mount manually before tightening the clutches for final positioning using the simple handset, followed by tracking.
  6. What doesn't seem to have been discussed earlier in this thread is that the ASI294MC is a colour sensor, whereas the ASI120MM is mono. Hope I'm not missing something here, but here is a stab at an explanation (I'm just starting with understanding the differences between mono and colour imaging). Due to the colour filters on the 294MC, photon capture rate will be reduced by a factor of 3. This is equivalent to the difference between stacking a single sub and three subs or alternatively the difference extending the overall imaging time by a factor of 3. Taking into account the relative f#s of the two scopes and the different pixel sizes results in a 1.6x higher arrival photon count per pixel for the 120MM compared to the 294MC (as noted above by @vlaiv). The end result is the 120MM captures 3x1.6 = 4.8 times more photons per pixel than the 294MC (assuming same QE). For the same overall exposure time the SNR will be higher for the 120MM due to more photons being collected. @microbe increased the gain of the 294MC image to try and match the target brightness of the two scope images taken with the same imaging time. This will increase the apparent on screen noise of the image. Part of this noise will include read noise and thermal noise, which will be a higher portion of the 294MC overall noise due to the lower photon capture rate.
  7. Having spent all of my working life in design, production and sale of relatively small market though high margin specific electronic products, the answer lies in the route to market- base component costs aren't so much more than a mass market product, but intrinsic cost comes from the design, production, marketing and selling costs of a lower volume product. These costs are increased by a lack of sales competition e.g. can you find different selling, or even temporary promotional, prices for a given astro product? We have to accept that our interest lies in a small and specific sector and that means cost to us. In addition we like to have good service from our suppliers and that adds to the selling price.
  8. It's a slightly chilly and damp 12 deg C down here - hence more comfortable testing indoors! (Plus working on the coma corrector spacing.) When first powered up and already at ambient, with the fan running the sensor settles at 2-3 deg C above ambient within 5-10 minutes, so not much time lost there. Good ideas about building a dark library - thanks. Bob
  9. Having recently purchased an Altair Hypercam 183M with a simple fan cooler rather than a TEC cooler, I wondered what effect the fan would have on sensor temperature as it's really an anti-warming fan rather than an active cooler. So a simple test was to let the camera operate without the fan running to see what stable temperature it reached, followed by turning on the fan at full speed to see how this affected the sensor temperature. The (indoor) test without the fan running stabilised the sensor at over 28 deg C (actually the temp was still climbing but very slowly). This took about 25 minutes. With the fan then turned on, the sensor temperature dropped by over 5 deg C in a further 25 minutes - showing the fan does provide a useful cooling effect which will help with the (already low) sensor noise. With the fan running the sensor temperature looks to be about 2-3 deg C above ambient.
  10. Sometimes I think about relaxing in a sky viewing chair looking at the night sky through a pair of imaging specs that would show me real-time what only cameras can today capture. A great mixture of visual and imaging - what a sight that would be looking around the sky e.g. just imagine the size of the Rosette nebula!
  11. My 650/130 reflector started out life as a Meade Polaris 130 before various mods (including fitting a SkyWatcher mirror) but it still has the Meade 1.25" focuser (teflon strips inside to eliminate slop). As 1.25" coma correctors are hard to come by (and expensive!) I made one from stock parts based on a design in an old magazine. https://stargazerslounge.com/topic/288608-diy-125-coma-corrector For such a simple design it works pretty well with the f#5 scope as can be seen in the attached M42 taken with the 1000D and CC. A 1.25" filter can be screwed on to the bottom of the CC, so I can even do a bit of LRGB or Ha before deciding on which filter wheel to purchase. Yes - just 15 to test with. Taken at the same time as imaging. Lots of sky noise around from the near full Moon. First time for me using darks as I depended on dithering to reduce noise with the DSLR. Longer exposures did result in some amp glow though. Certainly an alternative Adam. I think that's Super Pixel mode in DSS (have tried it once some time ago with success). Bob
  12. Thanks for the info @jjosefsen and @david_taurus83. The replacement guide camera module and hub arrived, so I've been able to make a start on testing and learning about the new setup - takes time as I didn't become familiar with my DSLR overnight (using APT for capture and PHD2 for dithered guiding)! Due to the imaging and guiding resolution of my setup I plan to use 2x2 binning. As confirmed on the APT forum, APT has an issue with binning with the Hypercam 183M, so I won't use if for now until the issue is fixed. SharpCap seems to take quite a lot of memory and my little netbook has trouble running SharpCap together with all of the other necessary programs, so I'm using Altair Capture at the moment as this runs without problem and is easy to use. At some point I will likely need to control a filter wheel and also run dithering so a change of program will be necessary - but I'm not there yet. Before that there are still flats to get right (didn't work first time) and installation of the coma corrector. Although the Moon was up last night, I did a couple of quick test images (attached) using my 650/130 reflector. Both 60 off 30 sec subs at gain 4 (I think that is unity gain with Altair Capture - please correct me if not) plus darks, no flats. At 13 degrees C darks seem free of noise with just hot pixels evident. Aligning targets and focusing using a mask is quick and easy with the 183M camera in video mode - a nice improvement. I'd like to do an Ha test image with an (old) Astronomik 1.25" filter (especially with the Moon up) - just need to work out how to mount it! If you have any ideas on a suitable target please say. So far seems a great camera. The simple cooling fan helps stop the sensor warming - It doesn't look like sensor thermal noise will make much difference to LRGB imaging for my conditions. Ha imaging is likely to be different of course. NINA looks interesting. I will give it a go. Bob
  13. Nice one - I like the smoothness and detail in the galaxies. A bit of blue around the stars - something to do with the filters? Perhaps a bit of star reduction would improve the image. I'm just starting out with an IMX183 sensor camera and will be very happy if I can do as well. Bob
  14. Like yourself, I was out last night testing my new Altair Hypercam 183M on the Moon. For comparison, here is a single sub at minimum gain (good for max dynamic range) and 12msec exposure.
  15. Thanks Adam - I will post on the APT forum. No real reason to slow the fan down other than SharpCap and Altair Capture provide this and (very brief) testing suggested half speed kept the sensor at a similar temperature. The fan is very quiet so full speed isn't an issue and the fan certainly helps with limiting sensor warming. Bob
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.