dan_adi

I view it as the best of both worlds. Let the encoders do most of the work for tracking, and correct an eventual drift with a guide correction. I've seen examples of 1-2 guide corrections per minute. I wonder how professionals are doing it. It's safe to assume they can afford absolute encoders. Do they also guide ? Given those big scopes, and big metal structures, I guess flexure and mirror movement is a problem for them as well.

If the model is not quite good, as is the above example from youtube, the 10 Micron should/could be guided also. There are lots of 10micron users, mostly examples on CN, that use guiding + model, simply because with lower quality scopes, the model is not enough. I was referring to RMS guiding accuracy. The option for really fast tracking is useful for satellites, otherwise maybe for a fast model build? I had my fair share of headaches with the sitech control system on the Mesu, until I learned what was needed for a smooth and reliable operation. So I am not a big fan of the sitech system. But once you learn the software, the performance of a guided friction drive is quite impressive.

I understand now, thanks!

My guess is that the model is flawed due to using an SCT with the mount. I bet with a high quality Planewave CDK the results would be much better. Or better yet, a refractor. This is why you need both, good scope + good mount. What is impressive to me, is that my Mesu mount has better performance than this, at more than half the price ... makes one wonder about overpricing. With absolute encoders this mount should deliver 0.2-0.3" RMS constantly! Otherwise it's hard to justify 20K EUR

Hmm, but these mount have the option to update the temperature and pressure all night, so the refraction is computed at every zentih angle. With regard to seeing ... if we don't use a guide camera and issue no guide corrections, how can the seeing influence tracking?

Very good points, but I wonder how seeing can influence the model. While tracking there is no guide camera to influence the tracking, no camera, no guiding corrections. Does the seeing error creep in when we build the model? Does the seeing affect platesolving? I do agree that the model is flawed due to the SCT mirror movement.

Indeed these are the specs. Have to say I am not impressed. "No point guiding at 0.3” RMS when your seeing is 1.5”??" - Yes you should! Your stars fwhm is determined by a combination of factors like seeing, guiding error, image scale, angle from zenith etc. I regularly guide at 0.3" with seeing above or at 1.5" . To test go here: https://clearskies.go.ro . Submit the default values in the exposure time calculator, then, on the results page go to the Image FWHM tab. Leave everything as is, except increase the guiding error from 0.35" to 0.75". The FWHM jumps from 2.18 " to 2.68". That is an additional blur of 0.5 " in 1.5" seeing.

If I remember correctly, seeing has a big impact with regular guiding. A model takes into account temperature, pressure, refraction .. so the seeing has less impact on a model. Mirror flop is random, so it cannot be modeled out. This could explain the deteriorating performance as time passed. Still, I didn't expect this.

Hello, Recently I stumbled on this video of a beautiful 10 micron 3000 HPS mount. But when I reached the 9:55 minute mark, I was kind of disappointed with the numbers reported on 'guiding'. Since there were no corrections made, everything was running on a model. Considering he was using a C11 Hyperstar config, at a forgiven focal length ... 0.7 " RMS is quite disappointing. It could be the SCT quality. These scopes should not model well. Bottom line, do you think it's the scope at fault? or is this a regular performance of this kind of mount?

Hello, Did you manage to check the cable contacts to the controller? To initialize the mount you need to unpark, and do a photo init from sitech.exe. the init pop up windows will show up.before you click ok, make sure looking east/west is selected appropriately. Also do not pick a region on the sky below your horizon file for an init. On the sitech.exe forum you will get more help on from Don or Dan. They know their stuff.

I did have a similar problem long ago. I my case it was a slightly loose wire connection on the controller. This made the scope start moving on its own, and go blinky. Also be sure you are correctly initializing the mount. A bad init can cause lots of problems... Simple routine: power up unpark the mount the tracking starts do a photo init take pictures all night do a photo init before parking park the scope power off All this implies you made correct settings in the software - sitech.exe

Thank you. I don't quite get what you mean? You don't have to know python, it's just a webpage. You enter the data for your scope camera target etc. and it spits out an exposure time for your target given a desired SNR (signal to noise ratio)

Hi, The webapp is now available over secure https connection. The app is at: https://clearskies.go.ro/

I'm a little late to the discussion. I made my own software for my astro needs. I encourage you to build any astro app you desire. It is a wonderful learning experience, even if something similar exists. If you are a professional programmer it will be easier for you. In my case, I only took programming classes in high school, so I had to learn python from scratch. With astropy you can build lots of cool stuff! I made an exposure time app, a cosmology app, and a simple Simbad query to generate 3D star maps and orbits. Lots of fun!

Thanks for all the likes, happy holidays everyone!

You're welcome, In my search of an amateur shot of this object, Morten's image was the best. He benefited greatly from better seeing and a bigger scope. His image contains subs with fwhm <2.5, but in my case I had to go with subs <3fwhm otherwise too much data would have been tossed. In my Luminance image, PI reports a median fwhm of 2.6 and an eccentricity of 0.43.

Thanks. Still not done yet ... need the RGB data, and to learn more about processing 🙂

Thank you! Abell 370 seems to be about twice as far as Abell 2218, with z = 0.375. But the main arc seems rather big compared to the ones in 2218. So it might be doable ... if I can find some info on the magnitude of the arc, I can crunch the numbers. I am anxiously waiting for next galaxy season to add the RGB data! My inspiration was the effort of Morten here https://www.astrobin.com/344564/?q=Astrodon E-series 2 B , and the image from Mauna Kea http://sky.esa.int/?target=248.9765671854323766.1993560685588&hips=DSS2+color&fov=0.20099604102438107&cooframe=J2000&sci=false&lang=en&hst_image=heic0404c He used a 12 inch scope, with better seeing, and 65 hours. But I think I am very close to his performance.

😃 it's small and big at the same time, depends on your perspective ... but it does take 2 people to safely mount it

Two years ago I wanted to see if I can confirm gravitational lensing in the cluster ABELL 2218 using a small aperture 8 inch apochromatic refractor. This is a preliminary result, composed of luminance and near infrared data. As a side project I wrote a little webapp for computing exposure time, since I had no idea how much I should expose for such faint targets, especially in my backyard. To make matters worse, I live at sea level Next summer, I will add an estimated 20hours per RGB channel, for a total exposure time of 160 hours. I was pleasantly surprised to capture some of the arcs, so all the work paid off. The image is a widefield view with lots of other interesting galaxies. You will have to zoom in to reach the cluster. I also attached the hubble image for comparison and easier arc identification. Specs: Telescope: CFF 8 inch apochromatic refractor Mount: Mesu 200 MK1 Camera: Moravian G3 16200 mono CCD Filters: Astrodon Luminance, Astrodon Ic (NiR) Luminance: 81 hours NIR: 27 hours Data was drizzled I only made minimal processing PI: Crop, automatic background extraction, noise reduction and blur exterminator (works awesome). Data on some ARCs using Planck 2018 cosmology: The whole cluster is located at 2.3 Glyrs, with a redshift of 0.1704 ARC A Redshift = 2.515 Proper distance (at light emission or “then”) = 5.553 Glyr (Billion light years) Proper distance (at light arrival or “now”) = 19.520 Glyr (Billion light years) Light travel time = 11.191 Gyr (Billion years) Velocity = 434267.523 km/sec or 1.448 x c Currently the galaxy is outside the event horizon, so light emitted now will never reach us again Vmag = 22.35 ARC L Redshift = 1.033 Proper distance (at light emission or “then”) = 5.578 Glyr (Billion light years) Proper distance (at light arrival or “now”) = 11.340 Glyr (Billion light years) Light travel time = 8.067 Gyr (Billion years) Velocity = 210330.975km/sec or 0.701 x c Vmag = 20.25 ARC H Redshift = 0.702 Proper distance (at light emission or “then”) = 4.954 Glyr (Billion light years) Proper distance (at light arrival or “now”) = 8.432 Glyr (Billion light years) Light travel time = 6.501 Gyr (Billion years) Velocity = 153231.638km/sec or 0.551 x c

Indeed my Luminance exposure is 300 sec and NIR exposure is 600 sec. Later this evening I will have time to test in PI and see if I see an improvement in the image. I thought it should be a waste to throw away 20 hours of data if I can add them to the rest of 80 hours Today I'll get to work on my Abell 2218 lensing project. I didn't get to do much besides wbpp and a crude stretching, but I am happy to see I detected a few arcs with a 8 inch scope. Next year during Galaxy season I will get the RGB data as well

Hello, The Luminance is 80 h of data, and NIR is 20 h. So the ratio should be 20/80, or 1/4? After looking on the forum I see the common way is to average 2 masters in PI pixel math, simply (master1 + master2)/2. So, with ratios I should do master1L + 0.25* master2Nir? To get the full spectrum I should have used a clear filter, but I forgot. Thanks

I was simply thinking in extending the Luminance range from 400-700 nm to 400-900 nm, thus making an extended Luminance master.

I had the same dilemma when I build my processing PC. What I used: processor: AMD Ryzen 16 cores Ram: 128 GB DDR4 Disk: Samsung 980 nvme Video card: an old GeForce GTX 960 I had around OS: Linux Wbpp in Pixinsight takes 1 hour from start to finish with 1000 62 MBytes fits files

Hello, I have some Near Infrared Data captured with a Astrodon NIR filter. What is the optimal way, in Pixinsight, to add the NiR to L. Do I simply use pixel math like L master +NiR master?